. Is there any way to remove residual product left in pipes after a batch operation? OEG Company in Osaka, Japan commercialied a device called !ushkun that runs throu"h pipes and #pushes$ out left over product. %he system is particularly valuable in batch operations where product recovery is chief concern. %he manufacturer manufacturer claims that at one installation, the system paid for itself in four months throu"h product recovery. &ystem costs depend on the scale of the system, but are typically around '(),))) *& +(-.
/. 0hat particle sies are electrostatic precipitators used to remove? 1. 2uprey conducted testin" on an electrostatic precipitator in a pulp mill. %he results were published in a 3ational 1ir !ollution Control 1dministration report called #Compilation of air !ollutant Emission 4actors$.
5. 0hat are 6ameless o7idiers? 4lameless o7idiers are used to treat volatile or"anic compounds +8OC and li9uid or"anic streams. %raditionally, these types of streams were combusted to break down the molecules. %he disadvanta"e of this treatment method was the formation of 3O7. 4lameless o7idiers use electrically heated ceramic packin" and a hi"h velocity introductio introduction n system to initiate the destruction of the or"anic compounds into carbon dio7ide and water. Once this o7idation reaction be"ins, it continues via self:perpetuation. Capital cost for such systems are usually about /;< less than traditional combustion combustion systems and capacities can ran"e from /;) to =),))) &C4> +standard cubic feet per minute. %hermatri7 Inc. is the pioneer for this technolo"y. 8isit their website below.
=. 1re there any special considerations to be taken into account for combustin" ammonia? %he heat of combustion of ammonia is -,))) tu per pound. %here is no reason why it cannot be combusted with or without au7iliary fuel. @owever, ammonia combustion does result result in a 6ue "as havin" a hi"h concentration of 3O7 and the desi"n of a combustion chamber for ammonia re9uires special conditions to miti"ate or reduce the level of 3O7 emissions.
;. 0hat are some common causes of control valve noise? If you have e7cessive pressure drop across the control valve and the downstream pressure is low enou"h to cause the li9uid to 6ash, a "reat deal of noise in the control valve can result. E7cessive E7cessive dama"e can be done as well. %his is a common problem at low 6ows. Aeview the desi"n information on the valve and the process to see if low 6ow may be the problem. If the valve is incorrectly sied the noise will be
apparent from from the day of installation. If 6ows have recently been chan"ed, the valve may have been desi"ned correctly at the time, but is too lar"e for current operation.
B. @ow much water is lost throu"h a commercial coolin" tower system with a throu"hput of about B)) G!>? %his 9uestion depends on many factors. It sounds like the tower is small. 1 rule of thumb su""ests that the tower will see an evaporation loss of about ).(< of the circulation 6owrate for each 4ahrenheit de"ree of coolin". Other losses include drift losses +probably +probably very small for your tower and blow down. low down is simply a pur"e of tower water to prohibit the buildup of solids.
. 0hat is the diDerence diDerence between C4> +cubic feet per minute and &C4> +standard cubic feet per minute? C4> and &C4> are both measures of 6ow rate. C4> mi"ht refer to either the 6ow rate of a "as or a li9uid, whereas &C4> refers only to the 6ow rate of a "as. %he same mass 6ow rate of a "as +i.e., lbsminute is e9uivalent to various volumetric 6ow rates +i.e., C4> dependin" upon the "as pressure and temperature. %hus, when "as 6ow rates are speciFed, it is very important to specify at what pressure and temperature the "as was measured. 0hen the "as 6ow rate is speciFed as &C4>, it means that the 6ow rate was measured at a set of standard pressure and temperature conditions.
In the *&1, the most common set of standard conditions used in industry is B) de"rees 4ahrenheit and one atmosphere of pressure. 3ote that we have stressed most common, because there are other standard conditions conditions that may be used. It is always best to spell out what standard conditions are bein" used +i.e., (/)) &C4> at B) de"rees 4 and ( atmosphere pressure. 0hen "as 6ows are e7pressed simply as C4>, the reader is can only speculate as to what "as temperature and pressure apply to that 6ow rate and, because of that, the C4> 6ow rate cannot be converted to a mass 6ow rate
-. 0hat is the ma7imum recommended velocity for steam in a plant pipe network? @i"h:pressure steam should be limited to about (;) fts and low:pressure steam should be limited to about ()) fts.
. 0hat is the ma7imum recommend pipe velocity for dry and wet "ases? 4or dry "ases, you should desi"n for a velocity of about ()) fts while wet "ases should be limited to about B) fts.
(). @ow instrument air is continually supplied in process plant? %he instrument air supply is "uaranteed by dedicated air supply with :=) oC dew point. 1part from this there is about /) to 5) minutes of back up provided for emer"encies like power failure, instrument air:"eneration failure, etc.
((. @ow can you keep our seawater used for heat reHection clean before enterin" our heat e7chan"ers? &eawater is used as a coolin" a"ent in condensers and coolers. Intermittent Intermittent inHection of chlorine "as is used to eliminate marine "rowth. %he system is a once throu"h type. %he band screens before the suction of the pumps are supposed to eliminate scales and other suspended materials. %he band screens are not properly functionin". Coolin" water 6ow is about /.B million "allons per hour.
%he prescreenin" prescreenin" and mobile screens screens are are not a sucient sucient protection protection for the recirculatin" water. %his is a very common problem. In clean salt water the biolo"ical "row in the coolin" water pipes is the main problem +mussels, barnacle, al"ae, etc.. 1fter the life cycle is Fnished they die and blockin" the condenser tubes. %o solve this debris problems use self:cleanin" 2ebris 4ilters +24 directly installed in front of the waterbo7 of the heat e7chan"ers.
(/. 0hat are some "uidelines for desi"nin" for li9uid and "as velocities in process plant pipin"? 4or normal process plant desi"n li9uid pump dischar"es, look for velocities in the ran"e ;: ftsec. probably not a bad idea to keep desi"n vapor velocities below (/; ftsec. %hese "uidelines mi"ht be applied by an en"ineerin" company for desi"n. If you are lookin" at plant operation, it is common to Fnd velocities in the :(/ ftsec ran"e. Erosion problems can also complicate the answer to this 9uestion. Erosion is hi"hly dependent on the nature of the 6uid. 4or e7ample, -< @/&O= is not corrosive to carbon steel pipe, however it very erosive at #normal desi"n$ velocities. 2esi"n criteria for -< @/&O= mi"ht be ).) ftsec >1I>*>. @owever, it is also well known that if the same -< @/&O= has a little emulsiFed hydrocarbon, it is substantially substantially less erosive.
(5. Is it advisable to cool a Fn fan by sprayin" demineralied water on it? 4in fan has carbon steel tubes with aluminum Fns AE&!O3&E In a similar service, the Fn fan suDered e7ternal corrosion when sprayin" it with demin water. %he salt and o7y"en in the air corrodes the air:cooler.
%he "as is piped normally normally from an an outside cylinder cylinder stora"e facility to a process process control panel at appro7imately B) psi". %he panel:output chlorine pressure is (; psi" and a 6ow rate of appro7imately ).)5 scfm. Occasionally the 6ow control devices in the process panel are contaminated by what appears to be li9uid chlorine. It seems that temperature temperature variations in the iron transport pipe may have some in6uence on the li9uid formation.
%he condensation condensation temperature temperature of "aseous chlorine chlorine at B; psi" is ;= de" 4. 4. %hus, if your transport line is lon", it is 9uite likely that ambient temperatures lower than ;= de" 4 could result in coolin" the line enou"h to cause condensation of the chlorine "as. If you lower the transport pressure to /; psi", the condensation temperature would be /= de" 4 , which should si"niFcantly lower the likelihood of cold ambient temperature temperature causin" the "as to condense.
(=. 0hat is a "ood method of steam tracin" lar"e vessels? One common approach to heat tracin" proHects is a #platecoil$ concept. If you are unfamiliar with this type of e9uipment, you should visit one of the links below. 2ependin" on your tank+s or application, the platecoil can easily steam trace +or heat:up your process. %he method of application is simple and routinely done by sub:contractors. sub:contractors. 3ew heat:tracin" cements have made this method even more ecient and less costly than what we had in the past. %he platecoils can be pre: formed to Ft your tankKs cylindrical shell or elliptical heads. 4lat surfaces are very easy.
!latecoils are a 9uick, low:cost, and safe installation. >ost platecoils are found in stock, oD:the:shelf in stainless construction. construction. I have used them to winterie tanks as well as to reduce viscosities in heavy polyols and other hi"h molecular wei"ht compounds while processin" or durin" stora"e. One of the best features of this type of tracin" is that it is not invasive L dependin" on the application, you may be able to install the platecoils while the tank is operatin". &till another interestin" feature is that you can use them as an assembly inside of tanks L as internal heaters. Mou can use steam, 2owtherm, hot oil or process streams inside the coils. Mou can easily insulate over them to conserve heat or to protect personnel. personnel. 1nother resource would be a publication by &pira7 &arco +link below. %his book contains a lot of information on steam tracin", best practices, traps, re"ulatin" valves.
(;. @ow can you control the p@ level in our coolin" water with respect to ammonia contamination?
1 coolin" tower in a urea manufacturin" facility is e7periencin" very hi"h ammonia levels +/)) to 5)) ppm in the coolin" water. %he ammonia level 6uctuates with wind direction. AE&!O3&E if your coolin" water has /)):5)) ppm of ammonia, you have a problem, which must be solved. Mou may have a water:cooled process heat e7chan"er, which has a tube leak that is leakin" ammonia into your coolin" water. Or the ambient air in your urea plant has a si"niFcant ammonia content +from various fu"itive leak sources such as pipin" 6an"es, control valve packin" "lands, pump and compressor seals, etc. and when the wind blows that ambient air into the coolin" tower, the ammonia is absorbed in the coolin" water. In either event, you have an unhealthy situation, which must be corrected. Contactin" a company that is specialied in these types of water treatment problems may be a wise decision +E7 3alco.
(B. 0e have some pieces of metals that have been #powder coated$, how does that work? !owder coatin"s are similar to paint, but they are usually much more durable. Aather than addin" a solvent to the pi"ments and resins in paint, as is typically the case, powder coatin"s are applied to the surface in a Fne "ranular form. %hey are typically sprayed on so that they stick to the surface. Once the surface has been suciently spray coated, the piece is baked at hi"h temperatures, and the pi"ment and resins pieces melt and form a durable, color layer.
(. 0hat industries re9uire Fltered compressed air? 1lmost every chemical process, power plant food processin" etc. plant has some type of air:operated device from control valves to air operated pumps and all have an air compressor deliverin" Fltered air.
(-. 0hat are some "ood tank mi7in" rules of thumb? 4or 6uid with viscosities under (),))) Cp, baNes are hi"hly recommended. %here should be four baNes, ) de"rees apart. %he baNes should be ((/th the tank diameter in width and should be spaced oD the wall by (;th the baNe width. %he oD: wall spacin" helps to eliminate dead ones. If baNes are used, the mi7er should be mounted in the vertical position in the center of the tank. If baNes are not used, the mi7er should be mounted on an an"le, (; de"rees to the ri"ht and positioned oD center. %his breaks up the symmetry of the tank and simulates baNes althou"h not nearly as "ood as baNes.
%he purpose of baNes is to prevent solid body rotation all points in the tank are movin" at the same an"ular velocity and no top to bottom turnover. %he formation of a lar"e central vorte7 is a characteristic of solid body rotation. @owever, small vortices that travel around the 6uid surface, collapse, and reform are more a function of the level of a"itation.
(. 0hat is a "ood source of e9uations for calculatin" dischar"e 6owrates from accidental releases? If you are interested in the calculation of dischar"e 6ow rates from accidental releases, read the online technical article #&ource %erms for 1ccidental 2ischar"e 4low$ at the website below. It provides the e9uations used for a variety of common types of accidental "as or li9uid releases and e7plains how to use them.
/). 0hat is the deFnition of #"ood$ coolin" tower water? Generally speakin", coolin" tower water should have a p@ between B and -, a chloride content no more than ;) ppm, a sulfate content +&O= below (/)) ppm, and a sodium bicarbonate +3a@CO5 content below /)) ppm. 1dditionally, coolin" tower water should not be heated past (/) P4 to avoid platin" out of treatment chemicals in process coolers.
In addition, if free chlorine is used for biolo"ical "rowth control, it should be added intermittently with a free residual not to e7ceed ( ppm and this should be maintained for short periods.
/(. 0hen specifyin" a coolin" tower, should I look up historic wet bulb temperatures for my area or should I take measurements? If this is a new installation, look up historical wet bulb temperatures for area and be sure to report them to the coolin" tower manufacturer as #ambient wet bulb temperatures$. %he manufacturer will adHust this temperature accordin"ly to estimate an #enterin" wet bulb temperature$.
If you have an e7istin" tower that is to be replaced, take several wet bulb temperature measurements near the air inlet durin" the hottest months. Aeport this as the #enterin" wet bulb temperature$ to the tower manufacturer.
%he diDerence between the ambient and the enterin" wet bulb temperatures is to account for wet recirculation from the tower e7it back to the tower entrance. %he
enterin" wet bulb temperature always hi"her than the ambient wet bulb temperature.
//. I& there a rule of thumb to estimate the footprint of a coolin" tower durin" desi"n phase? Over the years, this one has seemed to stand the test of timeQ
Every million tuh of tower capacity will re9uire appro7imately ())) ft/ of coolin" tower basin area.
/5. 0hat could be a possible cause for sudden foamin" in a coolin" tower? 1ssumin" that no other chan"es have been made, especially to the water treatment chemicals, the most common outcome to this mystery is a leakin" heat e7chan"er.
e"in a systematic check of all of the heat e7chan"ers that use the coolin" tower water and inspect them thorou"hly for leaks. Even small amounts of some chemicals can cause bi" foamin" problems in the tower. In addition, not all of these components will set oD a conductivity alarm.
/=. 0hat factors should be compared when evaluatin" coolin" tower bids? E7aminin" the followin" factors should allow for a reasonable evaluation of coolin" towersQ
( !urchased cost
/ Installed cost
5 4an ener"y consumption
= !ump ener"y consumption
; 0ater use
B 0ater treatment costs
E7pected maintenance costs
- 0orker safety re9uirements
Environmental safety
() E7pected service life
/;. 4or a heat e7chan"er, will the overall heat transfer coecient increase alon" with an increase in R>%2 +lo" mean temperature diDerence around the unit? %he overall heat transfer coecient is "enerally weakly dependent on temperature. 1s the temperatures of the 6uids chan"e, the de"ree to which the overall heat transfer coecient will be aDected depends on the sensitivity of the 6uidKs viscosity to temperature. If both 6uids are water, for e7ample, the overall heat transfer coecient will not vary much with temperature because waterKs viscosity does not chan"e dramatically with temperature. If, however, one of the 6uids is oil which may have a viscosity of ())) c! at ;) P4 and ; c! at =)) P4, then indeed the overall heat transfer coecient would be much better at hi"her temperatures since the oil side would be limitin". Aealie that the overall heat transfer coecient is dictated by the local heat transfer coecients and the wall resistances of the heat e7chan"er. %he local heat transfer coecients are dictated by the 6uidKs physical properties and the velocity of the 6uid throu"h the e7chan"er. &o, for a "iven heat e7chan"er, 6uid 6ow rates, and characteristics of each 6uid.the area of the e7chan"er and the overall heat transfer coecients are F7ed +theoretically anyway.as the overall heat transfer coecient does vary sli"htly alon" the len"th of the e7chan"er with temperature as IKve noted and the *:value will decrease over time with foulin".
/B. 0hat is condensate lift? %his is a term that is usually used to indicate how much pressure is re9uired to SliftK condensate from a steam trap or other device to itKs destination at a condensate return line or condensate vessel. %he Frst ima"e below shows a situation where a properly sied control valve is used on a steam heater. 2urin" nominal operation, the utility steam under"oes a nominal ():/; psi pressure loss throu"h the valve. 4or typical utility steam +(;) psi or hi"her, this can leave a pressure at the steam trap
e7it that is often ade9uate to lift the condensate to its destination. 4or e7ample, if the steam losses /) psi throu"h the valve and another (; psi throu"h the heater and pipin", that can leave up to /B; ft of head to push the condensate to the header. In this case, there is little need for a condensate pump. On the other hand, if the control is too lar"e, it will only be a few percent open durin" normal operation and the steam can under"o a pressure loss of ;):; psi or even hi"herT In addition to supplyin" terrible control for the heater, it also reduces the available head for condensate lift. In this case, or if the steam supply pressure is relatively low, it may be necessary follow the steam trap with a separation vessel and a condensate pump to push the condensate to the return line.
/. 0hat type of heat e7chan"ers are most commonly used for a lar"e:scale plant: coolin" loop usin" seawater as the utility? Commonly known as a #secondary coolin" loop$ or &ECOOR, a closed loop water system is circulated throu"h a processin" plant near a sea. !rocess heat is transferred into the closed loop water and then this water is circulated throu"h heat e7chan"ers to transfer +reHect the heat to seawater. %his is a hallmark plate and frame heat e7chan"er application. %he hi"her heat transfer coecients that are available in plate and frames e7chan"ers +!@Es will minimie the installed cost because the material of construction of choice it Grade ( %itanium +hi"her *:value means lower area. %o combat plu""a"e the narrow passa"es in the e7chan"ers, the seawater is typically run throu"h lar"e automatic back6ush strainers desi"ned especially for seawater. !eriodically, these strainers will reverse 6ow and #blowdown$ debris to clear the strainer. %his method has been used for many years with "reat success.
/-. Can condensate control in a reboiler cause water hammer problems? %his topic was recently discussed in our online forum. %he short answer to this speciFc 9uestion is$not very often$. It is very common to control reboilers on distillation columns via this method. %his is not to say that this control method is the best for any heat e7chan"er usin" steam for heatin". 4or e7ample, if there is an appreciable de"ree of subcoolin" of the condensate, the incomin" steam can e7perience #collapse$ +or thermal water hammer when it is e7posed to the cool condensate. In reboilers, the process 6uid is simply bein" vaporied so little or no subcoolin" of the condensate takes place. %his makes for a "ood opportunity for condensate level control in a vertically oriented shell and tube reboiler. %he level controller is typically placed on a vessel that is installed in conHunction with the shell side of the reboiler. %his will allow for full condensate draina"e +if necessary and there is no need to weld on the shell of the e7chan"er. +&ee "raphic below AeferenceQ Cheresources >essa"e oard
/. 0hy is a vacuum breaker used on shell and tube heat e7chan"ers that are utiliin" steam as the heatin" utility? 8acuum breakers are often installed on the shell side +steam side of shell and tube e7chan"ers to allow air to enter the shell in case of vacuum conditions developin" inside the shell. 4or an e7chan"er such as this, the shell side should already be rated for full vacuum so the vacuum breaker is not a pressure +vacuum relief device. 2evelopment of vacuum in the shell could allow condensate to build in the unit and water hammer may result.
5). 0hat is a barometric condenser? &in"le:sta"e or multi:sta"e steam:Het:eHectors are often used to create a vacuum in a process vessel. %he e7haust from such eHector systems will contain steam +and perhaps other condensable vapors as well as non:condensable vapors. &uch e7haust streams can be routed into a #barometric condenser$ which is a vertical vessel where the e7haust streams are cooled and condensed by direct contact with downward 6owin" cold water inHected into the top of the vessel. %he vessel is installed so that its bottom is at least 5= feet +().= meters above the "round, and the eNuent coolin" water and condensed vapors 6ow throu"h a 5=:foot len"th of vertical pipe called a #barometric le"$ into small tank called a #hotwell$. %he #barometric le"$ allows the eNuent coolant and condensed vapors to e7it no matter what the vacuum is in the process vessel. &uch a system is called a #barometric condenser$. %he non:condensable vapors are withdrawn from the top of the condenser by usin" a vacuum pump or perhaps a small steam eHector. %he eNuent coolant and condensed vapors are removed from the hotwell with a pump.
5(. 0hat is the best way to control an oversied, horiontally oriented shell and tube steam heater? 1 used shell and tube heat e7chan"er is to be used in steam heatin" duty. %he heat e7chan"er is lar"er than necessary and the control scheme to be employed is bein" investi"ated. %he steam to be used will be B; psia:saturated steams. %he process 6uid is a li9uid brine 6uid. 13&0EA& %wo opinions were oDered on this topicQ 1. %he actual pressure in the heater, while the steam is condensin" is dependent on the condensin" rate and the overall dirty *. %ubes can be plu""ed to reduce the amount of heat transfer area, as lon" as the process side +tube velocity does not "et too hi"h. Calculate the needed area and then the re9uired steam 6ow rate. 1n oriFce can be sied to control the steam 6ow rateU however, at reduced loads the condenser may e7perience partial vacuum conditions so be sure that the shell is rated for full vacuum. 0hen this partial vacuum condition does occur, choked 6ow will be e7perienced throu"h the steam control valve. %he Cv trim value would need to be sied such that the choked 6ow does not e7ceed what is needed. %his is tricky and re9uires several trim sie chan"e outs.
5/. Is it ever advanta"eous to use shells in series even thou"h it may not be necessary? *sually you desi"n for the least number of shells for an item. @owever, there are times when it is more economical to add a shell in series to the minimum conF"uration. %his will be when there is a relatively low 6ow in the shell side and the shell stream has the lowest heat transfer coecient. %his happens when the baNe spacin" is close to the minimum. %he minimum for %E>1 is +&hell I.2. ;. %hen addin" a shell in series "ives a hi"her velocity and heat transfer because of the smaller 6ow area in the smaller e7chan"ers that are re9uired. 55. 0hat is some "ood advice for specifyin" allowable pressure drops in shell and tube e7chan"ers for heavy hydrocarbons? 4re9uently process en"ineers specify ; or () !&I for allowable pressure drop inside heat e7chan"er tubin". 4or heavy li9uids that have foulin" characteristics, this is usually not enou"h. %here are cases where the foulin" e7cludes usin" tabulators and usin" more than the customary tube pressure drop is cost eDective. %his is especially true if there is a relatively hi"her heat transfer coecient on the outside of the tubin". %he followin" e7ample illustrates how 1llowable pressure drop can have a bi" eDect on the surface calculation. 1 propane chiller was coolin" a "as treatin" li9uid that had an avera"e viscosity Of .; c!. %he eDect on the calculated surface was as followsQ 1llowable tube pressure drop E7chan"er surface ; !&I =)(/ &9. 4t. /; !&I /()= &9. 4t. ;) !&I (=( &9. 4t. Mou can see that usin" /;:!&I pressure drop reduced the surface by nearly one:half. %his would result in a price reduction for the heat e7chan"er of appro7imately =)<. %his savin"s oDset the cost of the pumpin" power 5=. 0hat is a "ood appro7imation for the heat transfer coecient of hydrocarbons inside 5=V tubes? *se the followin" e9uation to estimate the heat transfer coecient when li9uid is 6owin" inside 5= inch tubin"Q @io W (;).s9rt+av". viscosity 0hereQ @io +%*ft/: hr:)4 8iscosity +c! this is limited to a ma7imum viscosity of 5 c! 5;. 0hat is a "ood relation to use for calculatin" tube bundle diameters? %he followin" are e9uations for one tube pass bundle diameter when the tube count is known or desiredQ 5) 2e". 2& W (.);/ 7 pitch 7 &XA%+count Y tube O.2. ) 2e". 2& W (.(5 7 pitch 7 &XA%+count Y tube O.2. 0hereQ Count W 3umber of tubes 2& W undle diameter in inches !itch W %ube spacin" in inches 5B. 0hat eDect does chokin" a vertical thermosiphon have on the heat transfer rate? Chokin" down on the channel outlet nole and pipin" reduces the circulation rate throu"h a heat e7chan"er. &ince the tubeside heat:transfer rate depends on velocity, the heat transfer is lower at reduced recirculation rates. 1 rule of thumb says that the inside 6ow area of the channel outlet nole and pipin" should be the same as the 6ow area inside the tubin". &hell Oil in an e7perimental study showed
that a ratio of ). in nole 6ow areatube 6ow area reduced the heat 6u7 by ()<. 1 ratio of ).= cut the heat 6u7 almost in half. 5. @ow can one 9uickly estimate the additional pressure drop to be introduced with more tube passes? 0hen the calculated pressure drop inside the tubes is underutilied, the estimated pressure drop with increased number of tube passes is new tube 2! W 2! 7 +3!1&&O!1&&5 0here 3!1&& W 3ew number of tube passes. O!1&& W Old number of tube passes this would be a "ood estimate if advanta"e is not taken of the increase in heat transfer. &ince the increased number of tube passes "ives a hi"her velocity and increases the calculated heat transfer coecient, the number of tubes to be used will decrease. 4ewer tubes increase the new pressure drop. 4or a better estimate of the new pressure drop, add /;< if the heat transfer is all sensible heat. &ourceQ Gulley Computer 1ssociates 5-. Can lar"e temperature diDerences in vaporiers cause operational problems? Rar"e temperature diDerences in heat e7chan"ers where li9uid is vaporied are a warnin" 6a". 0hen the temperature diDerences reach a certain value, the cooler li9uid can no lon"er reach the heatin" surface because of a vapor Flm. %his is called Flm boilin". In this condition, the heat transfer deteriorates because of the lower thermal conductivity of the vapor. If a desi"n analysis shows that the temperature diDerence is close to causin" Flm boilin", the vaporier should be started with the boilin" side full of relatively cooler li9uid. %his way, you do not start 6ashin" the li9uid. %he li9uid is slowly heated up to a more stable condition. If the vaporier is steam heated, the steam pressure should be reduced which will reduce the temperature diDerence. 0ith steam heatin", take a close look at the desi"n if the >%2 is over ) )4 this is close to the critical temperature diDerence where Flm boilin" will start. 5. 0hen should one be concerned with the tube wall temperature on the coolin" waterside of a shell and tube e7chan"er? 0hen desi"nin" heat e7chan"ers where hot process streams are cooled with coolin" water, check the tube wall temperature. @ewitt says that where calcium carbonate may deposit heat, transfer surface temperatures above (=) )4 should be avoided. Corrosion eDects should also be considered at hot tube wall temperatures. 1s a rou"h rule of thumb, make this check if the inlet process temperature is above /)) )4 for li"ht hydrocarbon li9uids and 5)):=)) )4 for heavy hydrocarbons. Consider usin" 1ircoolers to brin" the process 6uid temperature down before it enters the water:cooled e7chan"er. =). 0hen an e7pansion is Hoint needed on the shell side of a shell and tube heat e7chan"er? 1 F7ed tube sheet e7chan"er does not have provision for e7pansion of the tubin" when there is a diDerence in metal temperature between the shell and tubin". 0hen this temperature diDerence reaches a certain point, an e7pansion Hoint in the shell is re9uired to relieve the stress. It takes a much lower metal temperature
diDerence when the tube metal temperature is hotter than the shell metal temperature to re9uire an e7pansion Hoint. %ypically, an all steel e7chan"er can take a ma7imum of appro7imately =):)4 metal temperature diDerence when the tube side is the hottest. 0hen the shell side is the hottest, the ma7imum is typically (;) )4. *sually if an e7pansion Hoint is re9uired, it is because the ma7imum allowable tube Compressive stress has been e7ceeded. 1ccordin" to the %E>1 procedure for evaluatin" this stress, the compressive stress is a stron" function of the unsupported tube span. %his is normally twice the baNe spacin". &ourceQ Gulley Computer 1ssociates =(. 0hat kind of concerns is associated with temperature pinch points in condensers? e e7tra careful when condensers are desi"ned with a small pinch point. 1 pinch point is the smallest temperature diDerence on a temperature vs heat content plot that shows both streams. If the actual pressure is less than the process desi"n operatin" pressure, there can be a si"niFcant loss of heat transfer. %his is especially true of 6uids that have a relative 6at vapor pressure plot like ammonia or propane. 4or e7ampleQ If an ammonia condenser is desi"ned for /= !&I1 operatin" pressure and the actual pressure is ; !&I less and the pinch point is - )4, there can be a (B< drop in heat transfer. &ourceQ Gulley Computer 1ssociates =/. 0hat factors "o into desi"nin" the vapor space of kettle type reboiler? %he sie of the kettle is determined by several factors. One factor is to provide enou"h space to slow the vapor velocity down enou"h for nearly all the li9uid droplets to fall back down by "ravity to the boilin" surface. %he amount of entrainment separation to desi"n for depends on the nature of the vapor destination. 1 distillation tower with a lar"e disen"a"in" space, low tower eciency, and hi"h re6u7 rate does not re9uire as much kettle vapor space as normal. 3ormally the vapor outlet is centered over the bundle. %hen the vapor comes from two diDerent directions as it approaches the outlet nole. Only in rare cases are these two vapor streams e9ual in 9uantity. 1 simpliFcation that has been e7tensively used is to assume the hi"hest vapor 6ow is B)< of the total. In one case, where this would cause an undersied vapor space is when there is a much lar"er temperature diDerence at one end of the kettle then the other. %he minimum hei"ht of the vapor space is typically - inches. It is hi"her for hi"h heat 6u7 kettles. &ourceQ Gulley Computer 1ssociates =5. Is there a 9uick rule:of:thumb to estimate a "as side heat:transfer rate inside the tubes of a shell and tube heat e7chan"er? If you need to estimate a "as heat transfer rate or see if a pro"ram is "ettin" a reasonable "as rate, use the followin"Q h W ; &9. Aoot+Op. pressure()) %he operatin" pressure is e7pressed as absolute. %his is for inside the tubes. %he rate will be lower for the shell side or if there is more than one e7chan"er. &ourceQ Gulley Computer 1ssociates
==. 0hat are some "ood strate"ies for curin" tube vibration in shell and tube e7chan"ers? >ost 6ow:induced vibration occurs with the tubes that pass throu"h the baNe window of the inlet one. %he unsupported len"ths in the end ones are normally lon"er than, those in the rest of the bundle. 4or 5= inch tubes, the unsupported len"th can be = to ; feet. %he cure for removable bundles, where the vibration is not severe, is to stiDen the bundle. %his can be done by insertin" metal slats or rods between the tubes. 3ormally this only needs to be done with the Frst few tube rows. 1nother solution is to add a shell nole opposite the inlet to cut the inlet 6uid velocity in half. 4or non:removable bundles, this is the best solution. 1ddin" a distributor belt on the shell would be a very "ood solution if it were not so e7pensive. &ourceQ Gulley Computer 1ssociates =;. 0hat are some of the conse9uences of an undersied kettle type reboiler? %he eDect will be a decrease in the boilin" coecient. 1 boilin" coecient depends on a nucleate boilin" component and a two:phase component that depends on the recirculation rate. 1n undersied kettle will not have enou"h space at the sides of the bundle for "ood recirculation. 1nother eDect is hi"h entrainment or even a two: phase mi7ture "oin" back to the tower. &ourceQ Gulley Computer 1ssociates =B. 1re some heat transfer services more prone to tube vibration that others for a shell and tube e7chan"er? undle vibration can cause leaks due to tubes bein" cut at the baNe holes or tubes bein" loosened at the tubesheet Hoint. %here are services that are more likely to cause bundle vibration than others are. %he most likely service to cause vibration is a sin"le:phase "as operatin" at a pressure of ()) to 5)) !&I. %his is especially true if the baNe spacin" is "reater than (- inches and sin"le se"mental. &ourceQ Gulley Computer 1ssociates =. 1re there any alternatives to scrapin" a shell and tube if a capacity increase will make the pressure drop across the e7chan"er too lar"e? 0hen an increase in capacity will cause e7cessive pressure drop, you may not have to Hunk the heat e7chan"ers. 1 relatively ine7pensive alteration is to reduce the number of tube passes. Other possibilities are arran"in" the e7chan"ers in parallel or usin" lowFns or other special tubin". &ourceQ Gulley Computer 1ssociates =-. 0hat is a "ood method of minimiin" shell side pressure drop in a shell and tube e7chan"er? 0hen shell pressure drop is critical and impin"ement protection is re9uired, use rods or tube protectors in top rows instead of a plate. %hese create less pressure drop and better distribution than an impin"ement plate. 1n impen"ement plate causes an abrupt ):de"ree turn of the shell stream, which causes e7tra pressure drop. &ourceQ Gulley Computer 1ssociates =. Is there a diDerence in >%2 +>ean %emperature 2iDerence between #E$ and #J$ +2ivided 4low type shell and tube heat e7chan"ers?
2ivided 6ow +shell type J does not have the same correction as the usual 6ow pattern +shell type E. %hermal desi"n pro"ram make this correction factor mistake. %rue, there is very little diDerence at correction factors above ).). @owever, there is a diDerence at lower values. 4or e7ample, E9ual outlet temperatures &hell type #E$ correction 4n W ).-); &hell type #J$ correction 4n W ).; Cold outlet ;4 hi"her than hot outlet &hell type #E$ correction 4n W ).B; &hell type #J$ correction 4n W ).B; Contact us if you do not have >%2 correction factor charts for divided 6ow. %E>1 has one chart for a sin"le shell but it "ives hi"h values for the above e7amples and it is hard to read in this ran"e. &ourceQ Gulley Computer 1ssociates ;). @ow is plate heat e7chan"ers used in an ammonia refri"eration system? !late heat e7chan"ers are widely used in ammonia refri"eration systems, and they can be much smaller than the e9uivalent tubular e7chan"er can. %hey work best 6ooded. 1 6ooded e7chan"er system needs a way to separate the li9uid from the vapor. 1 typical system has a vessel, which acts as knockout drum, accumulator, and header tank in one, alon" with the heat e7chan"er. Ri9uid ammonia 6ows from the vessel to the e7chan"er, and li9uidvapor is returned to the middle of the drum. 8apor is removed from the top of the drum. %he li9uidvapor mi7ture from the e7chan"er has a lower density than the li9uid enterin" the e7chan"er, so "ravity provides the drivin" force to circulate the refri"erant. ;(. Is there a handy way to determine if a horiontal pipe is runnin" full if the 6ow rate is known? If Xd/.; is "reater than or e9ual to about ()./, then the pipe is said to full. In this case, X is in G!> +*.&. Imperial "allons per minute and d is in inches. AeferenceQ !ocket Guide to Chemical En"ineerin", I&3Q )--=(;5(( ;/. 0hat are some factors to consider when tryin" choosin" between a dry screw compressor and an oil:6ooded screw compressor? &crew compressors utilie a pair of #meshin"$ helical screws to compress "ases. %hese types of compressors a "enerally appropriate for a 6ow ran"e of -;:() m5h +5))):B))) acfm and dischar"e pressures in the ran"e of /)):/B) k!a +5)):=)) psi". 1s the name implies, dry screw compressor run dry while oil:6ooded compressors use oil for bearin" lubrication as well as to seal the compression chamber. %he oil also carries the heat from the compression away from the compressor. %his heat is typically reHected to an e7ternal heat e7chan"er. &ome factors to consider when choosin" between the two types of screw compressors include
Is the process "as compatible with the oil? If the answer is no, use dry type 2oes the process "as have to be oil free? If the answer is yes, use dry type is eciency the top priority. If the answer is yes, use oil:6ooded type 1re you lookin" to minimie shaft:seal leaka"e. If the answer is yes, use oil:6ooded type 1re there any li9uids in the incomin" "as. If the answer is yes, use oil:6ooded type 2oes the "as
contain small particulate matter? If the answer is yes, use dry type these and other "uidelines can help in choosin" between the two types of screw compressors. ;5. *nder what circumstances are vorte7 6owmeters the most accurate? %he accuracy of vorte7 6owmeters can be within (< so lon" as theyKre bein" operatin" within their recommended 6ow ran"e, have a steady stream, and you have () pipe diameters of strai"ht pipe behind the in front of the 6owmeters. Outside of these parameters, these 6owmeters are not accurate. ;=. 0hat are the advanta"es and disadvanta"es of usin" "ear pumps? Gear pumps are a type of positive displacement pump that are appropriate for pumpin" relatively hi"h pressures and low capacities. 1dvanta"es include the ability to handle a wide ran"e of viscosities, less sensitivity to cavitation +than centrifu"al style pumps, relatively simple to maintain and rebuild. 2isadvanta"es can include a limited array of materials of construction due to ti"ht tolerances re9uired, hi"h shear placed on the li9uid, and the 6uid must be free of abrasives. 1lso, note that "ear pumps must be controlled via the motor speed. %hrottlin" the dischar"e is not an acceptable means of control. ;;. @ow can one estimate how the friction factor chan"es in heat e7chan"er tubes with a chan"e in temperature? &eider and %ate recommended the followin" for determine friction factors inside heat e7chan"er tubes with varyin" temperaturesQ 4irst, determine the avera"e, bulk mean temperature in the processin" line. 4or e7ample if the 6uid enters the line at 5)) PC and leaves at /-) PC, use /) PC to determine the physical properties and friction factors. 1s for correctionsQ Raminar 4low If the li9uid is coolin", the friction factor obtained from the mean temperature and bulk properties is divided by +bulk viscositywall viscosity)./5 and for heatin", itKs divided by +bulk viscositywall viscosity).5-. @ere, the bulk and wall viscosity are determined at the mean temperature over the len"th of the line. %urbulent 4low If the li9uid is coolin", the friction factor obtained from the mean temperature and bulk properties is divided by +bulk viscositywall viscosity).(( and for heatin", itKs divided by +bulk viscositywall viscosity).(. ;B. 0hat type of pump may be appropriate for a li9uid near saturation, a low 6ow rate, and very limited 3!&@a +net positive suction head available? %his application is nearly perfect for a turbine re"enerative type of pump. 4actors that immediately identify your application and pump type are the small 6owrate, low 3!&@a, and hi"h temperature. %he re"enerative turbine was speciFcally developed for these conditions and one moreQ hi"h dischar"e pressures. %he hi"h dischar"e pressure may not be necessary, but the re"enerative turbine can "ive you an 3!&@r of ).; feet with ease. %hey are particularly suited to saturated boiler feed water and your application is similar, albeit not in pressure. Mou can visit the site below to learn more about these types of pumps. ;. 0hat type of 6ow measurement devices is best for slurries?
1ny device that restricts the 6ow to perform measurements is not recommended for slurries. %hese devices include oriFces and dampeners. %hese devices can lead to li9uidsolid separation and they can lead to e7cessive erosion. Instead, measurin" devices that do not restrict the 6ow should be used. One e7ample of such a device is the ma"netic 6ow meter. ;-. &hould slurry pipes be sloped durin" horiontal runs? If possible, slurry lines should indeed be sloped. Generally, to slope the pipes (/ inches for every () feet of pipe is recommended. ;. 0hat is the best way to conF"ure a bypass line in slurry services? ypass lines should be placed 1O8E the control valve so that the slurry cannot settle out and build up in the line durin" bypass. B). 0hat types of valves are recommended for slurry services? %ypically strai"ht:throu"h diaphra"m, clamp or pinch, and full:port ball valves with cavity Fllers are the preferred type of slurry valves. In "eneral, "ate, needle, and "lobe valves are 3O% recommended for slurry services. B(. 0hat is a "ood estimate for the absolute rou"hness for epo7y lined carbon steel pipe? %he speciFc rou"hness for welded, seamless steel is .)))/ ft. !8C has a speciFc rou"hness of ).))))); ft. Mou may also want to consider usin" the @aen:0illiams formula, which lists a coecient of (5):(=) for cement:lined cast iron pipin". Mou need to decide which is more conservative for your application. Is %his 1nswer Correct? ( Mes ) 3o B/. @ow can you determine the lar"est impeller that a pump can handle? %he motor ampera"e should be measured in the Feld with the pump dischar"e valve wide open. &ubtract about ()< from the pumps ma7imum rated ampera"e. %hen the ma7imum impeller sie can be determined from 1/ W 1( +d/d(5 1/ W >a7imum ampera"e minus ()< 1( W Current operatin" ampera"e d/ W >a7imum impeller diameter d( W Current impeller diameter B5. 0hat is the si"niFcance of the minimum 6ow re9uired by a pump? %he minimum 6ow that a pump re9uires describes the 6ow below which the pump will e7perience what is called #shutoD$. 1t shutoD, most of the pumpKs horsepower or work is converted to heat that can vaporie the 6uid and cause cavitations that will severely dama"e the pump. %he minimum 6ow of a pump is particularly important in the desi"n of boiler feed pumps where the 6uid is near its boilin" point. B=. @ow can you estimate the eciency of a pump? %he followin" method, developed by >.0. Zello"", "ives results within 5.;< of most manufacturersK curves. ED < W -):)./-;;@Y5.-[():=@4:/./5[(): @4/Y;.5[():=@/:B.5[():@/4Y=.)[():()@/4/ @ W 2eveloped head, ft 4 W
4low in G!> +"allons per minute 1pplicable for heads from ;) to 5)) ft and 6ows from ()) to ())) G!> B;. @ow can you 9uickly estimate the horsepower of a pump? %ry this handy little e9uationQ @orsepower W +G!>+2elivered !ressure ((; +Eciency G!> W Gallon per minute of 6ow 2elivered pressure W 2ischar"e minus suction pressure, psi Eciency W 4ractional pump eciency BB. 0hat are the anity laws associated with dynamics pumps? (. Capacity varies directly with impeller diameter and speed. /. @ead varies directly with the s9uare of impeller diameter and speed. 5. @orsepower varies directly with the cube of impeller diameter and speed. B. @ow can you estimate a "as 6ow based on two pressure measurements? Mou can use the 0eymouth e9uation to estimate the "as 6ow. elow is the e9uation. %he compressibility should be evaluated at !av" shown below. 3omenclature is as followsQ X W 6ow rate, >illion Cubic 4eet per 2ay +>C42 %b W base %emperature, de"rees Aankin !b W base pressure, psia G W "as speciFc "ravity +reference airW( R W line len"th, miles % W "as temperature, de"rees Aankin \ W "as compressibility factor 2 W pipe inside diameter, in. E W Eciency factor EW( for new pipes with no bends EW).; for pipe less than a year old EW)./ for avera"e operatin" conditions EW).-; for unfavorable operatin" conditions B-. 0hat is a 9uick way to calculate frictional pressure drops in carbon steel pipe? %he relationship shown below is valid for Aeynolds numbers in the ran"e of /()) to ()B. 4or smooth tubes, a constant of /5,))) should be used rather than /),))). B. 0hat is screen analysis and what are its applications in the chemical industry? 1 screen analysis is the one passes solids throu"h various sies of screen mesh. %his is done to "et a particle sie distribution. 1 "roup of solids is Frst passes throu"h Fne mesh and the amount that passes is noted, then a little lar"er mesh and the amount recorded and so on. ). 0hat is a "ood device to use for obtainin" viscosity data for a non:3ewtonian 6uid? Consider a rotational viscometer. It will measure the shear rate applied and the subse9uent viscosity at the same time. Mou can also vary the temperature and time the stresses are applied for the truly #fun$ non:3ewtonian 6uids. 1ccordin" to Cole: !armer, #%he rotational viscometer measures viscosity by determinin" the viscous resistance of the 6uid. %his measurement is obtained by immersin" a spindle into the test 6uid. %he viscometer measures the additional tor9ue re9uired for the spindle to overcome viscous resistance and re"ain constant speed. %his value is then converted to centipoises and displayed on the instrumentKs RC2 readout.$ 0hen testin" a tomato sauce sample, the followin" results were observedQ #1 sample of tomato sauce was analyed to determine the productKs viscosity proFle. %he test was conducted at a temperature of /;PC. 1n updown speed ramp was
performed from () to ()) A!>, "ivin" a viscosity ran"e of from 5,-)) to B5/.; c!, over shear rates from 5.= to 5=.) reciprocal seconds. %he test data obtained for tomato sauce shows that this product e7hibits a marked shear thinnin" viscosity proFle over the test conditions. (. 0hat are some common methods for helium leak testin" a vacuum system? It is common to have a location in the suction line of the pump to detect the helium. %hen, the helium source is passed over the 6an"es and other possible sources of leaka"e. %his is done while monitorin" the detector at the pump suction for detectable amount of helium. 1lternatively, if your system can take pressure as well as vacuum you can try pressurin" it up and lookin" for the leaks that way. 1s yet another alternative, you can install an IA unit to the suction of the pump and spray isopropyl alcohol on the 6an"es. /. 0hat is a common source of error in determinin" the percent spent caustic in reFnery applications? In titrations, a common error made is that the technicians stop at the phenolphthalein endpoint +which is incorrect rather than the methyl oran"e endpoint +which is correct. &toppin" the titration too soon can cause the results to be "rossly under:reported. E9uation +(Q /3aO@ Y @/& :] 3a/& Y /@/) E9uation +/Q 3a/& Y @/& :] /3a&@ Overall E9uationQ 3aO@ Y @/& :] 3a&@ Y @/O 5. 0hat is a "ood method of analyin" powders for composition? 1 method known as 4ourier transform:infrared +4%:IA spectroscopy is often used for this purpose. 4%:IA sends li"ht beams of varyin" wavelen"th throu"h the sample and the re6ected li"ht is analyed by spectroscopy to Fnd the absorption of each wavelen"th. %he measured wavelen"ths are compared with a reference laser and the sample composition can be calculated. 1nalect Instruments Inc. specialies in 4%:IA measurement. =. 0hat are some common problems associated with bellow e7pansion Hoints? ellow e7pansion Hoints have "ained a reputation for bein" #weak$ points in pipin". *sually they are used to remove pipin" stresses from e9uipment or to allow for minor pipin" moments. If they are used properly, e7pansion Hoints can save e9uipment andor e9uipment welds from stresses "enerated from pipin" forces. %he two most common complaints about bellows are (. %hey tend to build up dirt /. %hey are #weak$ point in pipin" +as noted earlier. %o overcome these issues, manufacturers can be"an installin" drains in the bellows to allow for the period pur"in" of material. 1dditionally, bellow manufacturers have placed much emphasis on installation advice and showin" their customers how to protect the bellow from unnecessary dama"e. One such method is the use of tie rods between the end 6an"es to avoid pressure thrust movements +beyond the bellowKs desi"n conditions which are often the cause of bellow failures ;. 1re there any methods of preventin" crackin" of carbon steel welds in reFnin" environments?
0here carbon steel is an appropriate material of construction, 31CE +3ational 1ssociation of Corrosion En"ineers has issued the followin" standardQ 31CE A!)=/, #>ethods and controls to prevent in:service environmental crackin" of carbon:steel weldments in corrosive petroleum reFnin" environments$. 4or welds where hardness testin" is re9uired, A!)=/ "ive the followin" "uidelinesQ 1. %estin" shall be taken with a portable rinell hardness tester. %est techni9ue "uidelines are "iven in an appendi7 in the standard. . %estin" shall be done on the process side whenever possible. C. 4or vessel or tank butt welds, one test per () feet of seam with a minimum of one location per seam is re9uired. One test shall be done on each nole 6an"e:to:neck and nole neck:to:shell +or neck:to:head weld. 2. 1 percenta"e of helpin" welds shall be tested +; percent minimum is su""ested. E. %estin" of Fllet welds should be done when feasible +with the testin" fre9uency similar to the butt welds. 4. Each weldin" procedure used shall be tested. G. 0elds that e7ceed /)) rinell shall be heat treated or removed. B. 0hat is a common failure mechanism for above "round atmospheric stora"e tanks? %anks constructed prior to the (;)Ks are notorious for failin" alon" the shell:to: bottom seam or on the side seam. %he principle reason for this is that these tanks were constructed before there were established procedures and codes for such a tank +E7 1!I:B;) #0elded &teel %anks for Oil &tora"e$. One of the key features of these codes and procedures was to make sure that tanks were desi"ned to fail alon" the shell:to:seam such that the li9uid remained lar"ely contained. . @ow does a tank:blanketin" valve operate? %ank lanketin" 8alves provide an eDective means of preventin" and controllin" Fres in 6ammable li9uid stora"e tanks. 8apors cannot be i"nited in the absence of an ade9uate supply of o7y"en. In most instances, this o7y"en is provided by air drawn into the tank from the atmosphere durin" tank emptyin" operations. %ank lanketin" 8alves are installed with their inlet connected to a supply of pressuried inert "as +usually 3itro"en, and their outlet piped into the tankKs vapor space. 0hen the tank pressure drops below a predetermined level, the blanketin" valve opens and allows a 6ow of inert "as into the vapor space. %he blanketin" valve reseals when pressure in the tank has returned to an acceptable level. -. @ow can one determine if a particular solid can be 6uidied as in a 6uidied bed? >r. 1le7 C. @oDmann of the &tratin"h Institute for Chemistry and Chemical En"ineerin" statesQ #0hether a material can be 6uidied at all is the 9uestionQ if it is Fne or sticky, the bed will be cohesive. It will then tend to form channels throu"h which the aeration "as will escape rather than bein" dispersed throu"h the interstices supportin" the particles. In the other e7tremeQ if the particles are too lar"e and heavy the bed will not 6uidie well either, but tend to be very turbulent and form a spout.$ @e "oes on to present classiFcation of 6uidiation by Geldart by use of the chart shown below. On this chart, the 7:a7is is the avera"e particle diameter and the y:a7is is the bulk density of the bed.
. 0hat are some "uidelines for siin" a !&8 for a Fre scenario on a vessel in a reFnery service? &iin" a !&8 on your vessel is a matter of calculatin" how much heat is inputted from the Fre. 1!I:;/) uses X W 41).-/ where X is %*hr, 4 is the insulation factor +commonly taken as (.) but can be less than (.) if your insulation will remain eDective durin" the Fre and not be dislod"ed by Fre hoses and Fnally, 1 is the e7ternal area in ft/. %he vapor load is then the total heat input from the Fre divided by the li9uidKs latent heat +%*lb.
1s a 6uid approaches its critical pressure, the latent heat as it boils decreases so the relievin" 6ow rate increases. 1t the critical point, the latent heat "oes to ). &ome companies simply use a minimum ;) %*lb latent heat others look at de: pressurin" e9uipment, etc. One point is the protection, or potential lack of it, provided by a !&8 durin" a Fre. %he boilin" li9uid in the vessel from the Fre helps keep the metal ScoolK so it retains its stren"th. Once the li9uid is "one or the 6ame impin"es on the wall not in contact with li9uid, the metal can 9uickly reach a temperature where it has insucient stren"th to withstand the internal pressure and you have a RE8E. 3ot somethin", you want to be around. 1s an added point to the information above, if ;) tulb is not your companyKs minimum standard for latent heat, here is an alternative to calculate the latent heatQ -). 1re there 6ow velocity restrictions to avoid static char"e build up in pipelines? %here is an 1ustralian standard #1&()/) +(-= ^ Control of undesirable &tatic Electricity$ In it, there is a table for 6ammable hydrocarbons as followsQ
!ipe &ie +mm >a7 8elocity +ms
() -
/; =.
;) 5.;
()) /.;
/)) (.-
=)) (.5
B))Y (.)
%his is based on pure hydrocarbons, and there is a correction, which can be applied for 6uids of diDerent conductivity. >ethanol has a hi"her polarity than hydrocarbons and hence is more conductive. %he resistivity of diesel is ()(5 ohm:m vs ()- for methanol. In addition to this, normal pipin" desi"n "uidelines should however be followed, such as appropriate earthin", and ensurin" e7it velocities into tanks of ( ms. -(. @ow can I evaluate the thermal relief re9uirements for double block:in of -< sulfuric acid? 1!I A!;/) "ives e9uations to calculate relief re9uirements. 4or thermal relief, a very simple formula re9uires the heat input and the coecient of thermal e7pansion of the li9uid. %he heat input could be a problem. If you are concerned about sulfuric in a line that is part of a heat e7chan"er system, then the heat is simply the desi"n capacity of the heat e7chan"er. If it were a pipeline in the sun, then you would have to calculate the amount of heat that the sun can put into the pipe. Mou can "et the coecient of thermal e7pansion from your supplier or any book on sulfuric. Mou can also calculate it by takin" the speciFc "ravity at two diDerent temperatures and divide the &G diDerence by the temperature diDerence. Coecient of e7pansion has the units of ()4. 3ow for the easy part, if you are at all concerned, Hust put in a 5=V 7 (V thermal relief valve and do not worry about doin" any calculations. @owever, I do not believe sulfuric has any problems in pipelines unless it is a very lon" one and directly in the sun. In addition, I would make it a standard procedure to drain the line if it will sit dead headed for any si"niFcant period. Just a small bleed will be enou"h. -/. 0hat is a "ood source of information for the desi"n of pressure vessels? !ressure 8essel @andbook 1uthor W Eu"ene 4. >e"yesy !ublisher W !ressure 8essel @andbook !ubl., Inc. !.O. o7 5;5B; %ulsa, OZ =(;5 !a"e (- tells you how to calculate a pressure vesselKs wall thicknessU pa"e (B tells how to calculate an 1!I &td. B;) &tora"e tank wall thickness. %he rest of the book is a "oldmine for youn" en"ineers ^ especially C@EKs involved in vessel desi"n. It also "ives all the information you re9uire for supports, noles, head desi"n, pipin", ladders, platforms, etc. -5. 0hat is the method of determinin" ma7imum diDerential pressure durin" hydro testin" of shell and tube heat e7chan"ers? >r. Aichard Ree of !lumlee International Consultin" usually heat e7chan"ers have two sets of test pressures per side, one for stren"th tests, and the other for #operatin"$ or #leak$ tests. %he stren"th tests are set by the desi"n code and if you have the ori"inal desi"n data sheets for your e9uipment then the information
should be shown on these. If you do not then you will have to do the calculations yourself, the e7act method will depend upon which desi"n code you use, the most common one bein" %E>1 +which uses the 13&I1&>E pressure vessel code for reference in this area.
>ost shell and tube e7chan"ers are desi"ned such that each side of the unit will withstand the full desi"n pressure, with only atmospheric pressure on the other side. In order to save money, some lar"er units will have the tube:sheets especially desi"ned to withstand only a much lower diDerential pressure +re9uirin" both sides to be tested simultaneously. %his important information should be shall 9uite clearly on the desi"n sheets and on the vessel nameplate +assumin" that either are available. If the only need is to check that a "asket has been properly installed then it can be permissible to perform a lower pressure test based on the operatin" pressure. %he acceptability of this lower pressure test will often depend upon the conse9uences of a leak. -=. 1re there any "eneral rules that should be considered when desi"nin" a slurry pipin" system? %he followin" are items to consider when desi"nin" a pipin" system that will transport slurriesQ
( 0henever possible, pipin" should be desi"ned to be self:drainin"
/ >anual drainin" should be installed to drain sections of the pipin" when self: drainin" is not possible
5 low:out or rod:out connections should be provided to clear lines in places where plu""in" is likely or could occur
= 1ccess 6an"es should be provided at %:connections
; >anifolds should have 6an"ed rather than capped connections to allow for easy access
B Clean:out connections should be provided on O%@ sides of main line valves so that 6ushin" can take place in either direction
reak 6an"es should be provided every /) feet of horiontal pipe or after every two chan"es in direction -;. @ow are vessel lined with "lass or how are they coated? 4irst, the "lass mi7ture is smelted for form the proper recipe based on temperature and pressure re9uirements of the vessel. %hen the "lass is "round into tiny particles and suspended in a li9uid medium called a slip. %his mi7ture is then spayed onto the surface to be coated. %he vessel is then heated to about -)) )C to bond the "lass to the steel +usually carbon steel. %he vessel is then slowly cooled. -B. 1t what temperature is "lass fused to steel in the makin" of "lass:lined e9uipment? %he borosilicate "lass is typically fused to carbon steel at a temperature of about -)) )C. -. 0hat are some typical applications for "lass:lined reactors? Glass:lined e9uipment "ives superior protection to all mineral acids at all concentration and temperatures. One e7ception is hydro6uoric acid. %hey are also used is hi"h:purity processes where cleanliness is very important. *sin" "lass:lined e9uipment help eliminate the possibility of metal contamination. 1 third application is in polymeriation. >etallic vessels sometimes tend to allow the polymer to stick to the walls of the vessels while "lass:lined vessels have "ood anti:stick properties. --. Is there any way to slow coke formation in ethylene furnaces? 0estaim Corporation has a commercial process for applyin" a special coatin" to the tubes used in ethylene furnaces. 0estaim claims that coke buildup is reduced to one:forth to one:tenth of the normal rate. %he coatin" consists of a combination of metal, ceramic powder, and a polymer. Once the coatin" is applied, the tubes are then heat:treated and reacted with an unspeciFed "as. 0elds cannot be coated with this process. -. 0hat information is needed to specify a mi7er? (. &peciFc Gravity
/. 4luid 8iscosity
5. !hase to be dispersed
=. &olid:li9uid systems
%he settlin" velocities of the (), ;), and ) percent wei"ht fractions of the particle sie distribution should be available. ;. 4or "as systems, the standard and actual 6ow rates will be needed. ). @ow can viscosity aDect the desi"n of a mi7er? 4or 3ewtonian 6uids, which will have a constant viscosity at all impeller speeds, most desi"n correlations will perform satisfactorily for viscosities up to ;,))) c!. 1bove ;,))) c!, estimatin" errors from /)< to ;)< can result in the siin" of the a"itator. (. @ow do you desi"n a vapor:li9uid separator or a 6ash drum? %he sie of a vapor:li9uid separator should be dictated by the anticipated 6ow rate of vapor and li9uid from the vessel. %he followin" siin" methodolo"y is based on the assumption that those 6ow rates are known. *se a vertical pressure vessel with a len"th:to:diameter ratio of about 5 to =, and sie the vessel to provide about ; minutes of li9uid inventory between the normal li9uid level and the bottom of the vessel +with the normal li9uid level bein" at about the vesselKs half:full level.
1t the vapor outlet, provide a de:entrainin" mesh section within the vessel such that the vapor must pass throu"h that mesh before it can leave the vessel. 2ependin" upon how much li9uid 6ow you e7pect, the li9uid outlet line should probably have a level control valve. /. @ow is waste heat boilers cate"oried? Chemical plants :+hydro"en, nitro"en, sulfuric acid, sulfur recovery Incineration plants:+fumes, chemicals, municipal solid waste AeFneries:+cat cracker, CO oD "ases Co"eneration, combined cycle plants:+"as turbine, diesel en"ine e7haust 4urnaces, kilns:+e7haust "ases &ee a complete table at the link below. 5. 0hat is the an"le of repose and what are its applications in the chemical industry? %he dictionary deFnes #an"le of repose$ as #the inclination of a plane at which a body placed on the plane would remain at rest, or if in motion would roll or slide down with uniform velocityU the an"le at which the various kinds of earth will stand when abandoned to them$. 1pplications to the chemical industrythink about the desi"n of the conical section of a stora"e bin. %he material would not fall out the bottom, as we may want. %his concept is also important in the desi"n of system desi"ned to move bulk solidsfor the same reasons. =. I would like to know how to sie a partial combustion reactor processin" methane and o7y"en, as a function of the 6owrate and of the pressure. In your case, you essentially have two reactionsQ C@= Y 5/ O/ L] CO Y / @/O +incomplete combustion C@= Y / O/ L] CO/ Y / @/O +complete combustion each of these reactions has a speciFc rate at which it occurs. If you wanted to desi"n a reactor properly, you would need to determine the conversion of methane
in each of the above reactions. %he upper limit of your 6ow rate is bound by the rate of reaction. If the 6ow rate is too hi"h, the reaction simply will not take place +i.e. the 6ame will burn out. I am not sure that there is a simple relationship between pressure and 6ow rate in this case. %he "ases need to spend a certain amount of time in the reactor in order for the combustion to take place +residence time. Once you know the residence time, you could desi"n a reactor for your speciFc 6ow rate. ;. 0hy is post:weld heat treatment +stress relievin" sometimes necessary for welded vessels? 2urin" the weldin" process, the two metal pieces bein" Hoined are subHect to e7treme temperatures and can cause the crystalline structure of the metal to pass throu"h various metallur"ical phases. 1s a result, hardenin" +and embrittlement of the metal can occur to varyin" de"rees +usually dependent on carbon content. @eat treatment is desi"ned to reduce the hardness in the heat:aDected one of the metals and increase ductility in these sections. 8arious pressure vessel codes contain the speciFcs re"ardin" the procedures for post:weld heat treatment. @eat is usually held for one hour per inch of thickness of the metal. %he temperature used is based on the #!:number$ of the metals. !:numbers are assi"ned based on the chemical composition of the metals. @oldin" temperatures can ran"e from (()): (5;) P4 +;5:5/ PC. B. Is it possible to compare the resistance to chloride attack of several materials of construction? %he !ittin" Aesistance E9uivalent Inde7 +!AE can be used for such a comparison if the chemical make:up of each material is known. %he formula for the !AE is !AE W < Cr Y +5.5 7 < >o Y +5) 7 < 3. . @ow can wet carbon dio7ide be responsible for a corrosion problem in iron: containin" metals? Carbon dio7ide reacts with water accordin" to the followin" e9uationQ CO/ Y @/O ^ ] @CO5: Y @Y 1s the concentration of CO/ increases, so does the concentration of the @Y ion. %his ion can then react with 4e in metals as followsQ 4e Y /@Y ^] /@ +atom Y 4e/Y 1s corrosion proceeds, the ferrous ions produced can react with the bicarbonate ions to form ferrous carbonate, which precipitates as a scale. -. 0hat steps can be taken to avoid stress corrosion crackin" +&CC in steel vessels used for storin" anhydrous ammonia? %he *.&. 3ational oard of !ressure 8essel Inspectors recommends the followin" in one of their classic articlesQ
(. !ressure vessels should be fully stress relieved or fabricated with heads that are hot:formed or stress relieved.
/. E7treme care should be used to eliminate air from the ammonia systemsU new vessels must be thorou"hly pur"ed to eliminate air contamination.
5. 1mmonia should contain at least )./ percent water to inhibit &CC. &ourceQ 3ational oard of !ressure 8essel Inspectors . 0hat chemical is used to e7pand air ba"s in such a short amount of time? %hat chemical is sodium aide +3a35 which is a solid propellant that can be electrically i"nited to form nitro"en "as almost instantly. ()). 0hat is an additive? 1n additive is anythin" that is added to a process that is not a basic raw material. It is usually present in such small 9uantities that it does not interfere with Fnal product 9uality. It is usually added to act as an enhancer or to prevent some unwanted reaction. 4or instance, anti:foam additives are added to columns, evaporators, reactors, etc. to prevent foamin". Inhibitors are added to &tyrene systems to prevent polymeriation. 1 well:known additive is a deter"ent added to motor oils and "asoline to keep your en"ine clean. ()(. @ow many "rams per liter would there be in a ).5; 3 +3ormality Citric acid solution? %he normality of a solution is the number of "ram:e9uivalent wei"hts of the dissolved substance per liter of solution. %he "ram:e9uivalent wei"ht of the dissolved substance is the molecular wei"ht of the dissolved substance divided by the hydro"en e9uivalent of the dissolved substance. Citric acid has a molecular wei"ht of (/.(/ and it contains three hydro"en e9uivalents +i.e., three COO@ "roups. %hus, the "ram e9uivalent wei"ht of the citric acid dissolved in water is (/.(/5 W B=.)= "rams. %herefore ).5; 3ormal citric acid would have +).5;+B=.= W //.=( "rams of citric acid per liter of solution. ()/. @ow can I treat a waste stream containin" both he7avalent chromium and arsenic? 0aste streams that contain these types of mi7tures are often treated in two or more reducin" tanks. &tron" reducin" a"ents such as sodium metabisulFte, sulfur dio7ide, and sodium bisulFte are often used. ()5. @ow can arsenic be removed from a9ueous waste streams? Often times, ferric chloride is added to such a stream. %he ferric chloride aids in the formation of 6oc to a""lomerate Fne arsenic particles that can then be removed by mechanical means. ()=. @ow can he7avalent chromium be removed from a9ueous waste streams?
One option is to use ferrous sulfate to reduce the he7avalent chromium to a less to7ic, trivalent chromium form that wills precipitate out of the solution. %rivalent chromium can then be reduced by sodium hydro7ide. ();. 0hat types of metals are typically removed via chemical precipitation? &ome of the more common metals or other substances removed via precipitation includeQ
( 1luminum
/ 1rsenic
5 arium
= Cadmium
; Calcium
B %rivalent chromium
@e7avelent chromium
- Copper
Iron
() Read
(( >a"nesium
(/ >an"anese
(5 >ercury
(= 3ickel
(; &elenium
(B \inc ()B. 0hat are some common precipitatin" a"ents used to remove metals from a9ueous waste streams? !erhaps the most common a"ents used areQ
( >etal hydro7ides
/ Rime or caustic soda
5 >etal sulFdes
= 1lum or ferric salts
; !hosphate or carbonate ions (). @ow can metals be removed from a9ueous waste streams? !recipitation is widely used to remove metals from waste streams. %he soluble heavy:metal salts can be converted to insoluble salts that will precipitate and can then be removed by clariFcation, Fltration, or settlin". ()-. 0hat is the 0et ulb Globe %emperature +0G%? %he sultriness of the ambient environment is more than a comfort factor. 4or workers, soldiers and athletes, hi"h levels of sultriness may result in heat stress that could very well be life threaten. %o determine the actual de"ree of sultriness in a 9uantiFable manner, the 0et ulb Globe %emperature +0G% inde7 is used. It includes the eDects of humidity, air speed, air temperature and the radiant heatin" factor +from the sun. %his inde7 was developed by the *.&. >ilitary in the (;)Ks and has become widely accepted for industrial temperature measurements to protect employees. It combines three temperature readin"sQ the wet bulb temperatureU the ordinary dry bulb temperature and a black bulb "lobe
temperature. %here are also instruments available, which measure 0G% inde7 directly, combinin" the three factors and their appropriate wei"htin" values. (). 0hat is a "ood source of surfactant information on the internet? Check out the &urfactant 8irtual Ribrary at the link below. ((). 0hat is a surfactant? 1 surfactant is a chemical that reduces the surface tension of pure li9uid or a mi7ture of li9uids. (((. 0hat is the easiest way to e7tract hydro"en from water and the safest way to store it? Electrolysis +which means splittin" usin" electricity of water is the method for producin" hydro"en from water. %he safest way to commercially store it would be to use a palladium #spon"e$, because palladium adsorbs several hundred times itKs own volume in hydro"en. One would need to produce a compound with a very hi"h surface area, which has a thin coatin" of palladium. %his type of material is commonly used as a catalyst in chemical processes. ((/. Can asphalt be recycled to form a useful product? 1sphalt can be "round into small pieces and emulsiFed to form a )< oil5)< water mi7ture. %his fuel can be used to power boilers. It has a heatin" value of B,B)) kcalk" and is said to be stable for about B months.
((5. @ow can separation of chiral chemicals aDect the chemical andor pharmaceutical industries? %his enantiomers +left or ri"ht _A` oriented versions of the same compound can have very diDerent propertiesU this development has been si"niFcant particularly in the pharmaceutical industry. 4or e7ample, the dru" &eldane is a racemic mi7ture of both & and A versions of the dru"Ks molecules. %hrou"h chiral separation technolo"y, @oechst was able to brin" the dru" 1lle"ra to market in only 5 years +far less time than is usually necessary. @oechst was able to bypass to7icity testin" because 1lle"ra is a sin"le chiral form of its molecule. y chiral separation, the most of the side eDects of &eldane were avoided in 1lle"ra.
((=. 0hat are !Cs? !C is a commonly used acronym for #!olyChlorinated iphenyls$. %hese compounds are famous for the disposal problems that they pose to the chemical industry.
((;. 0hat is 9uicklime and what are the uses? Xuicklime +Calcium O7ide is an ecient scaven"er of moisture in its dehydrated state. It is also cheap, compared to orthe scaven"ers such as silica "el, drierite, o7aolidines, etc. It is commonly found in water sensitive paint formulations +such as polyurethanes and polyureas. ((B. 0hat is happenin" when paint dries? 2urin" the manufacture of paint, solvents are added to make the paint thinner so that it can be applied to various surfaces. Once the paint is applied, the solvents evaporate and the resins and pi"ments that make up the paint for a thin, solid layer on the surface. ((. 0hat are the three classes of or"anic solvents? %ypically, or"anic solvents can be split up in the followin" classesQ O7y"enated, @ydrocarbon, and @alo"enated. O7y"enated solvents include alcohols, "lycol ethers, ketones, esters, and "lycol ether esters. @ydrocarbon solvents include aliphatics and aromatics. @alo"enated solvents include those that are chlorinated primarily. ((-. 0hat is a solvent? 1ccordin" to the *& &olvent Council, #1 solvent is a li9uid which has the ability to dissolve, suspend, or e7tract other materials without chemical chan"e to the material or solvent. &olvents make it possible to process, apply, clean, or separate materials. ((. 0hat is the easiest way to e7tract hydro"en from water and the safest way to store it? Electrolysis +which means splittin" usin" electricity of water is the method for producin" hydro"en from water. %he safest way to commercially store it would be to use a palladium #spon"e$, because palladium adsorbs several hundred times itKs own volume in hydro"en. One would need to produce a compound with a very hi"h surface area, which has a thin coatin" of palladium. %his type of material is commonly used as a catalyst in chemical processes. (/). @ow can you separate hydro"en pero7ide into hydro"en and o7y"en? %his is easily done. Just e7pose hydro"en pero7ide to air. %he o7y"en in the air will o7idie the hydro"en pero7ide into its component "ases. It happens far too slowly for industrial or most other purposes +an enyme catalyst can be used to speed up the process. @owever, neither hydro"en nor o7y"en is produced in this manner in industry. %he enyme catalyst is called #catalase$. (/(. 0hat is the lar"est application for surfactants? 1bout B)< of total surfactant market is composed of the deter"ent and cleanin" products marketplace. %hese types of compounds are sold in lar"e volumes at low prices.
(//. 0ho built the Frst production scale !R1 +polylactic acid facility? %he Frst production scale !R1 +polylactic acid facility was built by Car"ill 2ow in %he lair, 3ebraska, and *&1. %he facility is desi"ned to consume =),))) bushels of corn per day and produce 5)) million lbyear of !R1. (/5. 0hat is the avera"e salary for chemical en"ineers? 1IChE Hust came out with the results of a ChE salary survey +&ee Chemical En"ineerin" !ro"ress, &eptember /))). %o answer your 9uestion depends on years of service, the type of de"ree, the sie of the company and the type of industry, i.e. En"ineerin", 2esi"n Construction +EC, !lant work, &elf Employed as e7amples. %o summarie brie6y, median startin" salary is about ';),))) per year. >edian salary amon" all Chemical En"ineers is about ',/)) and annual raises are avera"in" =.=<. 1s far as Hob prospects that a"ain depends in which area you are interested. In "eneral, Hobs are still lookin" "ood. @owever, be forewarned, Chemical En"ineers no lon"er command the Hob security that we once had. In economic downturns, it can "et nasty. (/=. 0hat compounds are responsible for the odors that come from wastewater treatment plants? Compounds such as hydro"en sulFde, methyl mercaptan, dimethyl sulFde, and dimethyl disulFde can all contribute to this foul odor. (/;. 0hat does the catalystic converter on an automobile really do? 1 catalytic converter is a device that uses a catalyst to convert three harmful compounds in automobile e7haust "as into harmless compounds. %he three harmful compounds areQ
► @ydrocarbons
► Carbon
+in the form of unburned "asoline
mono7ide +formed by the combustion of "asoline
► 3itro"en
o7ides +created when the heat in the en"ine forces nitro"en in the air to combine with o7y"en.
Carbon mono7ide is a poison for any air:breathin" animal. 3itro"en o7ides lead to smo" and acid rain, and hydrocarbons produce smo". In a catalytic converter, the catalyst +in the form of platinum and palladium is coated onto a ceramic honeycomb or ceramic beads that are housed in a muNer:like packa"e attached to the e7haust pipe. %he catalyst helps to convert carbon mono7ide into carbon dio7ide. It converts the hydrocarbons into carbon dio7ide and water. It also converts the nitro"en o7ides back into nitro"en and o7y"en.
(/B. 0hat is an eDective means of removin" silicon from aluminum? &ilicon is well known for its chemical inertness, +i.e. it tends not to react with many other chemicals. 2ependin" on what type of silicon you are dealin" with, this may or may not be easy to solve. If the silicon is from a lubricant, it is probably the "raphitic form, which is soluble in a stron" combination of nitric, and hydro6uoric acids, neither of which I would recommend for you to usenor hydro6uoric acid is not easy to come by. If it is silicon from an acidic form +probably any other form other than a lubricant, you should try ammonia. In either case, leave your acetone at homeit will 3E8EA workT *!21%EQ 1n ammonia solution worked very well in this case (/. 0e wanted to know how to impart various colors to copper wire by simply dippin" them into various chemicals, formulations, etc. %his copper wire is to be used by us for our hobby of makin" various art obHects from copper wire. Chan"in" the color of copper by means of chemical reactions is a dan"erous Endeavour that I really do not recommend. @owever, there is somethin" you can do to "et a "reen color, if fact if you are familiar with the &tatue of Riberty here in 1merica, this would e7plain why it is "reen. Mou see, the outside of the statue is coated with copper and bein" in 3ew Mork City, it is subHected to acid rain. %his causes the formation of another chemical that coats the copper and "ives the statue its "reen color. %he two acids that you can use are nitric acid +which works best or sulfuric acid +which will probably re9uire some "entle heatin" alon" with the acid. I am not sure if there were a "ood way to "et nitric acid out of somethin" you may have around the house, you would probably have to buy it.
&ulfuric acid can be obtained from car batteries +the li9uid inside. Mou will want to boil the mi7ture +to concentrate it by evaporatin" the water, until you see white fumes +which are very dan"erous. %hen put your copper is while the acid is hot and leave it there until you "et the color you would like. If you are "oin" to do this, please do it outside or in a well ventilated area and make sure you have some bakin" soda handy is case you "et some of the acid on your skin. If you are lookin" for a diDerent color or more colors (/-. 1fter conductin" an internet search for ways to reduce ener"y costs, I found a recipe for whitewashin" that is said to re6ect sunli"ht. %he recipe calls for /) pounds hydrated lime to ; "allons water to (:9uart polyvinyl acetate. 0hat is a "ood source of polyvinyl acetate that I can buy at a local store? 0ell your recipe sounds e7citin". 4indin" your polyvinyl acetate should be easy. Go to your nearest department store and pick up a lar"e container of plain white "lueT %he chief active in"redient in this "lue is polyvinyl acetate. Good luck with your proHectT (/. 0hat are some characteristics of bulk solids that can aDect their ability to 6ow properly?
4our += main factors to consider include moisture content, temperature, particle sie +and shape, and time at rest.
( 1n increase in moisture content will "enerally make solids more #sticky$. &ome solids will absorb moisture from the air, which is why nitro"en is often used as a carrier "as +amon" other reasons.
/ 4or some solids, their ability to 6ow can be adversely impacted by temperature or even the len"th of time that the particles are e7posed to a speciFc temperature. 4or e7ample, soybean meal 6ows nicely at ) P4 but start to form lar"e brid"es at ()) P4.
5 Generally, the Fner a bulk solid becomes, the more cohesive the particles. Aound particles are "enerally easier to handle than #strin"y$ or oddly shaped particles.
1s particles rest in a bin, they can compact to"ether from their own wei"ht. %his can create stron" bonds between the particles.
= Often times, re:initiatin" 6ow can break these bonds and the solids will 6ow as normal, but this can depend on the load at "iven locations in the bin. (5). 0hat is a #saltation velocity$ and how is it used in desi"nin" pneumatic conveyin" systems? %he saltation velocity is deFned as the actual "as velocity +in a horiontal pipe run at which the particles of a homo"eneous solid 6ow will start to fall out of the "as stream.
In desi"nin", the saltation velocity is used as a basis for choosin" the desi"n "as velocity in a pneumatic conveyin" system. *sually, the saltation "as velocity is multiplied by a factor, which is dependent on the nature of the solids, to arrive at a desi"n "as velocity.
4or e7ample, the saltation velocity factor for Fne particles may be about /.; while the factor could be as hi"h as Fve for course particles such as soybeans could. (5(. @ow can one determine the particle sie distribution for a "iven bulk solid? 0hile there are hi"h:tech methods of performin" such an analysis +laser:diDraction and video ima"in" system are available, the simplest way is to use a sieve stack.
4or e7ample, to analye a particular solid, one would stack several diDerent mesh sies into a cylinder with the lar"est mesh openin" on the top and pro"ress down throu"h the cylinder to Fner mesh. %he cylinder would contain a pan on the bottom. efore be"innin", wei"ht the test sample, each piece of mesh, and the pan. %hen, the sample is loaded into the top of the test cylinder and the cylinder is e7posed to a combination of movements +shaken to allow the solids to pass throu"h the appropriate mesh sies. (5/. 0hat is the most common cause of solid sie se"re"ation in bulk solid systems? >any en"ineers usually point directly to the pneumatic conveyin" system as a source of such a problem. %he truth is that in most cases, se"re"ation occurs because of the diDerences in sies of the articles. 1s a rule:of:thumb, if the sie ratio e7tends outside of around (Q(.5, then there will most likely be se"re"ation. %his bein" said, one should inspect the e9uipment responsible for determinin" the particle sie rather than the pneumatic conveyin" system if this problem is occurrin". AeferenceQ Aichard 4arnish, the 0olfson Centre for ulk &olids @andlin" %echnolo"y (55. 0hat can cause bulk solids to stop 6owin" from a bin? Causes of such problems can fall into one of two cate"oriesQ >aterial stren"th or in GeometryQ 4actors that can aDect material stren"th include. >oisture is especially with particles, which fuse to"ether with moisture. (5=. 0hat is the practical particle sie limit for pneumatic conveyin"? 1s a rule, pneumatic conveyin" will work for particles up to / inches in diameter with a typical density. y #typical density$, we mean that a / inch particle of a polymer resin can be moved via pneumatic conveyin", but a / inch lead ball would not. (5;. 0hat is pneumatic conveyin"? !neumatic conveyin" is a method of movin" bulk solids from one place to another with the help of a carrier "as. 1 diDerential pressure is applied inside a conveyin" line. %he 6ow always moves from a re"ion of hi"her to lower pressure. (5B. 0hat types of pneumatic conveyin" systems are typically used? Essentially, there are two types of pneumatic conveyin" systems. In dilute phase systems, the solids are suspended in the carrier "as and transported to their destination. In dense phase systems, the solids:to:"as ratio is much hi"her. %he "as in these systems acts more like a piston to push the product to its Fnal destination. 2ilute phase systems are more typical than dense phase systems because they can employ positive pressure displacement or a vaccum system. 2ense phase conveyin" is useful if the product de"rades easily +works at lower velocities or is particularly abrasive. (5. 0hat is the most common carrier "as used in pneumatic conveyin"?
0hile many applications utilie air as a carrier "as, others are not suited for usin" air. 4or e7ample, if the substance bein" conveyed reactions with moisture in the air or if there is a threat of dust e7plosions, nitro"en is likely choice. (5-. 0hat are some common problems associated with dense phase pneumatic conveyin"? 2ense phase pneumatic conveyin", typically e7periences one common problem from system to systemQ plu""in" in the line due to a malfunctionin" booster valve. 2ense phase systems re9uire these booster systems to introduce new, pressuried air. %hese boosters are nearly always accompanied by a check valve. If the check valve becomes stuck, the product is allowed to plu" the line. (5. 0hat are some common problems associated with dilute phase pneumatic conveyin"? !robably the most common problem encountered in dilute phase pneumatic conveyin" is the wearin" of the rotary valve that serves as an air lock where the product is introduced into the system. If e7cess air is allowed to pass by the rotary valve, this can cause brid"in" of the material the 6ow can be slowed or stopped.
(=). 0hat is some common pipin" materials used to transport slurries? 0hen selectin" a pipin" material to transport slurries, corrosion and erosion considerations must be accounted for. &ome of the most popular pipin" materials includeQ
► Carbon
&teel
► &tainless
► @i"h
&teel
2ensity !olyethylene +@2!E
► 1crylonitrile
butadiene stryene +1&
► *nplasticied
► 4iber"lass
polyvinyl chloride +u!8C
reinforced plastic +4A!
► Elastomer:lined
carbon steel
(=(. @ow can you prevent brid"in" in a dilute phase pneumatic conveyin" system? >anufacturers of these systems recommend bin a"itation or blowin" air into the top of the feedin" bin. %hese methods can prevent Fne particle from brid"in" near the rotators valve. %wo types of particles that are especially prone to brid"in" include titanium dio7ide and calcined: kaolin clay.
(=/. 0hat is the best way to handle bend or turns in slurry pipin" systems? Even lon" radius elbows should be avoided in slurry pipes and lines. %hey are often the site of severe erosion or solidli9uid separation. Only "entle pipe bends or sweeps should be used to turn a slurry line. Industrial e7perience has shown that a bend:radius:to:pipe:diameter ratio of 5:; is recommended.
(=5. @ow can you determine the proper pipe thickness for a slurry line? 2esi"n of slurry pipin" systems should follow 13&I1&>E 5(.( and 5(.(( Codes. 1 simple e9uation for this calculation is as followsQ t W +!2 +/& Y C whereQ t W pipe wall thickness, in. ! W ma7imum desi"n pressure of the pipe, psi" & W ma7imum allowable desi"n stress, psi" C W corrosion or erosion allowance, in.
(==. 1re there any "eneral rules for 6ushin" slurry lines? &lurry lines should be 6ushed with a minimum 6uid velocity of () fts and the total 6ushin" li9uid volume should e9ual 5:B times the total pipin" volume.
(=;. 0hat is a "ood way to "et started in doin" a plant:wide steam consumption analysis? It is unclear as to whether or not you know the total steam consumption. If you do not, one way to "et it is to take the nominal capacity of the boiler in terms of heat, i.e. the total rated tuhr. %his is usually available either throu"h the documentation you have for the boiler or even on the nameplate. Mou also must know the steam pressure you are producin". *sin" the steam tables, "et the enthalpy of the steam and divide it into the nominal boiler capacity to "et the total rate. I hope that you also know how much of the capacity you are usin", ;)<, ;< etc. >ultiply this by the total lbhr to "et your rate. 1nother way to "et the capacity is by usin" the amount of boiler feed water you are sendin" to the boiler and the known level of steam you are producin". 2o not for"et to include the blow down in your heat mass balance. Gettin" the rate to each plant is more dicult if you are lackin" in instrumentation. *se as much plant instrumentation as possibleU 6ow meters,
pressure and temperature indicators. If you do not have a meter in each header to each plant, then see if you have them in sections or to pieces of e9uipment usin" the steam. 1nother way is to measure the amount of condensate you are returnin" to the boiler. If you are dumpin" the condensate, you may be able to collect and measure the amount in a pail from each source. 1nother way is to use the process instrumentation and do some mass and ener"y balances around the steam users.
(=B. 0hat are some "ood uses of low:"rade steam at (/ atm and (/)C? %here are various traditional methods to employ waste steam in an operatin" plantQ
(. Mou can "enerate electricity throu"h a steam turbine:"enerator set. %he electricity is usually put back in the lineU this is the idea behind the #Co:Gen$ concept used today in many *&1 plants. &team turbines can eDectively use saturated steam supply down to ; ^ ()) psi". In special conditions, they have used down to ;) psi" as a turbine steam supply. I have used steam as low as ()) psi".
/. Mou can pre:heat process streams that re9uire pre:heatin"U this is done by applyin" heat e7chan"ers.
5. Mou can employ the waste steam as a refri"eration source by employin" it in vacuum Het eHectors and producin" ;) of coolin" water.
Mou have to consider these as viable options if you can identify the heatin", coolin" and ener"y conservation re9uirements. 1n economic analysis is re9uired to identify the most attractive option. Mou usually utilie a 2iscounted Cash 4low analysis to base your decision and that means you must study each case as to savin"s "enerated. 1 fourth method mi"ht be that you can use the steam for environmental heatin" +if you live in a cold climate.
(=. 0hen usin" a pumpin" loop to mi7 two miscible 6uids in a tank, when can the content are considered well mi7ed? 1 rule of thumb is to turn the tank over three +5 times and then sample the tank for mi7ture properties. y #turn the tank over $, we mean to force the entire volume of the tank throu"h the pump at least three times. >ore turnovers may be necessary, but three times is a "ood startin" point.
(=-. Is there any way to repair a valve that is passin" leakin" internally without takin" our process oNine? 1 B)) psi", 5V steam line is e7periencin" #passin"$ or internal leaka"e. If you order to replace the valve, the process would have to be taken oNine. 1 temporary solution to the problem is sou"ht to "et the plant to their ne7t scheduled shut down 13&0EA Aesearch on:stream leak sealin" services. %his problem is 9uite common. 0hat they would do in this case is drill a hole into the bypass valve on the upstream side but not completely into the line. %hey would then tap the hole and install one of your inHection Fttin"s, which is like a small plu" valve. %hey would then take a lon" (-V drill bit and drill throu"h the open inHection Fttin" and into the pressuried line. %he drill bit is then removed and our inHection e9uipment is then attached. &ealant +heavy Fbers and "rease is pumped into the line and cau"ht in the 6ow, which will bind up a"ainst the leakin" seat on the bypass valve. If done properly, this techni9ue can be both eDective and safe.
(=. 0hile there, are many tests available to detect leaks on vessels, is there a technolo"y available to 9uantify the leak, or measure the 6ow throu"h a leak? %he Aheo8ac air in:leak monitor by Intek, Inc. in 0esterville, O@ is a viable meter that "ives the actual air in:leaka"e 6ow rate. It also "ives you e7hauster capacity and a vacuum 9uality readin". If you want to Fnd more information, you can view their web site below.
(;). 0hat are some common causes of "as pipeline vibration /) Carbon &teel line? Check consider the followin"Q
► %he
upper pressure ran"e and or the smaller pipe diameters prompts me to investi"ate the possibility that the "as is reachin" critical 6ow somewhere downstream within the pipe. 0hen a "as "ets to critical 6ow, sonic booms +producin" vibration are e7pected. In fact, one of the main means by which the additional pressure in the pipe is lost.
► If
the source is a compressor, look for sur"in".
► If
the source is a tower, look for pressure cyclin" in the tower
► Rook
at critical 6ow throu"h any control valve that may be in the line.
