INDIAN OIL CORPORATION LIMITED, PANIPAT
SUMMER VOCATIONAL TRAINING REPORT
Guided by,
Submitted by,
Mr. Kamal Pahwa
Bunty Rathore
Mr. Pradeep C Yadav
4th Year (UG)
Ms. Sangeeta Sinha (T&D) Mr. R Sharma (T&D)
IIT Roorkee
Acknowledgement I would like to express a deep sense of gratitude to Ms. SANGEETA SINHA(Training & Development), MR. R. SHARMA (Training &
Development) for their cordial support, valuable information and guidance, which helped us in completing this task through various stages. I would also express my profound gratitude and deep regards to my guide Mr. KAMAL PAHWA (Chief Production Manager) and Mr. PRADEEP C YADAV for their exemplary guidance, monitoring and
constant encouragement throughout the course of training. Their blessing, help and guidance given by them time to time shall carry us a long journey of life on which are about to embark. I wold also place my thanks to various engineers and operators for their cooperation in acquainting us in to the various in the plant. Especially, Mr. Bhuvan Gupta and Mr. Kartikey for guiding me and clearing all my doubts. I express my deep sense of the gratitude and indebtness to Dr. V. C. Shrivastav (Assistant professor, Dept. of Chemical Engineering) for giving me the opportunity to undertake training in Indian Oil Corporation Limited, Panipat, Haryana.
Last but not the least, I would like to thank my parents, my friends and my brother for their constant encouragement and help without which this assignment would not be possible.
INDEX
Introduction to Panipat Refinery
Atmospheric and Vaccum Distillation Unit
Once through Hydrocracker Unit
Diesel Hydro Desulphrisation Unit
Continous Catalytic Cracking Unit
Thermal Power Station
Euipments used in the Plant
Project 1
Project 2
Introduction to Panipat Refinery IOCL Panipat Refinery was established in 1998. It is the seventh and also the largest refinery established by IOCL. It has a capacity of 15MMTPA. Earlier it has the capacity of 6MMTPA but then in 2006 it is expanded to 12MMTPA under the Panipat Refinery Expansion Project (PREP). It is mainly an oil refinery, therefore crude processing is the main function here. The crude oil is refined into more useful and a variety of products such as petroleum naphtha, gasoline, diesel, kerosene and LPG. Crude oil is separated into fractions by fractional distillation. The fractions at the top of the column have lower boiling points than the fractions at the bottom. The heavy bottoms are often cracked into lighter, the more useful products. All these fractions are sent to other refining units for further processing. Major Products Petroleum products are usually grouped into three categories light distillates, middle distillates, heavy distillates and residue.
Light distillates: LPG, gasoline, naphtha Middle distillates: kerosene, diesel, ATF Heavy distillates and residuum: heavy fuel oil, lubricating oils, wax Common Process Units found in a refinery: Atmospheric Vacuum Distillation (AVU/CDU/VDU) unit distils crude oil into fractions. Continuous catalytic regeneration (CCRU) unit increases octane number of petrol. Once through Hydrogen Cracking unit (OHCU). Diesel Hydro Desulphurization unit (DHDS). Thermal Power Station (TPS) Hydrogen generation unit (HGU) Coking units (DCU) Fluid Catalytic Cracker
Atmospheric & Vacuum Distillation Unit
( AVU ) 1. Capacity : CRU - 7.5 MMTPA (million metric tons per annum) VDU – 4.125 MMTPA
2. Product Exit Main Column: Internal fuel Domestic fuel MS Component HSD Component Domestic fuel Aeroplanes HSD HSD HSD HCU/FCCU HCU/FCCU RFCCU/ IFO Bitumen/ VBU feed
Some notations in above table:
MS Component – Petrol
HSD – High speed Diesel
HCU – Hydrocracking Unit
FCCU- Fluidized Catalytic Cracking Unit
IFO- Intermediate Fuel Oil
VBU – Vacuum Blowing Unit
3. DESCRIPTION OF PROCESS FLOW SCHEME:
Crude is stored in eight storage tanks (six having a nominal capacity of 50,000 m3 each and remaining two are of 65,000m3 each). Booster pumps located in the off-sites are used to deliver crude to the unit feed pumps. Filters are installed on the suction manifold of crude pumps to trap foreign matter. For processing slop, pumps are located in the offsite area which regulates the quantity of slop into the crude header after filters. Provision to inject proportioned quantity of demulsifier into the unit crude pumps suction header with the help of dosing pump is available.
Crude oil from feed pumps is charged to heat exchangers in two parallel streams.
Desalting is a purification process used for the removal of salts, inorganic particles and residual water from crude oil and thereby reducing corrosion and fouling of equipment. This desalting process consists of three main stages, viz. heating, mixing and settling. Crude oil is heated to 125-135 °C in the pre-desalter heat exchanger train. Water is injected under flow control upstream of mixing valves. Brine outlet from the desalters is cooled in air cooler and water cooler before final disposal. Desalter pressure is controlled between11-12 kg-12 kg/cm2 by a control valve located at the discharge end of the crude feed pumps.
: Desalted crude from desalter is pumped by post desalter pumps into streams going through a second train (two in parallel) of heat exchangers. Downstream of the exchanger trains, crude oil streams combine to average out the temperature. Normal preheat temperature is in the range of 230-250°C.
the preheated crude is further heated and partially vaporized in three parallel tubular heaters. Each furnace is four pass heater with air preheater. Each furnace is provided with 14 burners capable of firing FO and FG, either fully or partially. Convection section has 8 rows of tubes with 8 tubes in each row. Two rows of shock tubes just above the radiant section are plain tubes without studs. In the convection section 4 studded tubes are for the service of superheating MP stream for strippers. The radiant box has 21 tubes in each pass. Convection zone had 12 rotary and 12 retractable soot blowers in two rows.
To recover waste heat from flue gases of CDU and VDU furnaces four identical parallel stationary air preheater units are provided and installed in parallel. At APHs cold combustion air routed to the burners will pick up heat from flue gases for efficient combustion. Three FD fans each capable of 55% of full load are provided with SCAPH in there discharge to heat the air up to 45 °C the combustion air requirement of each heater is controlled by individual FICS damper located in the air duct to the respective furnace. Load on the fans is varied by regulating the inlet guide vances. Heaters are provided with slain temp
O2 analyser and draft gauges. Furnaces are provided with different trip logic to save the equipments under different abnormalities.
This column contains 56 trays of which 10 are baffle trays. 6 chimney trays are also provided. Feed is introduced on tray number 10. Heated and partly vaporized crude enters the flash zone of the column at tray number 10 at 360-370 0 C. Hydrocarbon vapors flash in this zone and get liberated. Non-flashed liquid moves down which are largely bottom product called RCO.
The overhead vapors are totally condensed in crude overhead air condenser and trim condenser. This overhead condensed product is separated as hydrocarbons and water in reflux drum. Water is sent to sour water stripper. Unstabilised naphtha containing fuel gas, LPG and naphtha is partially refluxed and partially pumped to stabilizer.
Heavy naphtha is withdrawn from tray number 44 to the side stripper. Light ends in heavy naphtha are stripped in heavy naphtha reboiler using LGO as hot medium. The bottom product is cooled
in heavy naphtha exchanger followed by air fin cooler and sent to storage.
: kero is withdrawn as side product from tray no 31 to the kero side stripper .light ends in kero are stripped in the kero reboiler using HVGO CR as hot medium .the bottom product is routed to MP steam generator followed by LMP steam generator and finally cooled in trim cooler and sent to storage.
LGO is withdrawn as side product from tray no 22 to the LGO side stripper .Light ends in the LGO are stripped using MP steam .Bottom product is pumped through heavy naphtha reboiler ,crude preheat exchanger. Then the steam is cooled by air fin cooler and trim cooler before being routed to storage.
HGO is withdrawn from tray no 15 to the HGO side stripper .Light ends in HGO are stripped using MP steam .Bottom product is routed to preheat exchangers and then it goes to cooler before being finally routed to storage .
stripped RCO drawn from the bottom is sent to vacuum heaters of vacuum distillation unit.
In order to maximize heat recovery and balance tower loading ,heat is removed by the wave circulating reflux from each of the section .These pump around are withdrawn and pumped through preheat
train for maximum heat recovery thus cooling these steams .
Unstabilized naphtha from CDU is sent to Naphtha Stabilizer Unit. After preheating with stabilizer bottom in the feed/bottom exchanger. This column contains 40 trays with feed entering on 21st tray. Main components are fuel gas, LPG and Stabilized Naphtha. Stabilized naphtha is split
into two products 1) C 5 65/90 0 C - top product 2) C 5 115/165 0 C - bottom product The overhead vapour is condensed in air cooler and condensed product goes to the reflux drum, where a part is refluxed back to the column. This overhead product is further cooled to 40 0 C before being routed to storage via caustic wash. There is no need of caustic/water wash of bottom stream.
Vacuum Furnace: Hot RCO from atmospheric column at 355/365 0 C is mixed with slope recycle from vacuum column heated and partially vaporized in a 8 pass vacuum furnace and introduced in flash zone of vacuum column. The heater can be fuel gas, fuel oil or
combination of fuel fired. The radiant section tubes are arranged horizontally. Common convection section has horizontal banks of tubes positioned above the combustion chamber.
Vacuum Column: vaporized stream entering the flash zone of column along with stripped light ends from the column bottoms, rise up in the vacuum column and is fractionated into four side stream products. Hydrocarbon vapours are condensed in the HVGO, LVGO and Vac diesel sections by circulating refluxes to yield side products. Vacuum is created using ejector system in which MP steam at high velocity is introduced. Vacuum Diesel: it is drawn from the top section along with Circulating Reflux(CR) and Internal Reflux(IR). IR is return to the LVGO section and CR is returned to the top of the vac diesel packing after exchanging heat with the crude. Light Vacuum Gas Oil (LVGO): This section comprised of two beds for fractionation and heat transfer respectively. LVGO is drawn along with CR and IR from chimney tray number 2.
Heavy Vacuum Gas Oil (Hvgo): HVGO is drawn from chimney tray number 3 below bed number 4 along with CR and IR using HVGO pump. Vacuum Slop: This section is a combination bed with demister pad provided above the wash zone to prevent asphaltenes carry over. Slop distillate is withdrawn from chimney tray number 4 below bed number 5. Along with slop recycle on gravity. Vacuum Residue: The liquid portion of the feed drops into the bottom section of the tower and is withdrawn as vacuum residue. MP steam is used for stripping. Quenching is achieved by returning a quench stream to the tower at temperature of 250 0 C after heat exchange with crude in preheat train. Vacuum Residue is withdrawn by VR pumps and sent for heat exchange with incoming crude in the crude preheats train.
4. Process Optimization : 1) Through Circulating reflux 2) Through Coil oil Temperature 3) Through preheating the crude with product.
Once Through Hydro-Cracker Unit (OHCU) Hydrocracking is an extremely versatile catalytic process in which feed stock ranging from Naphtha to vacuum residue can be processed in presence of hydrogen and catalyst to produce almost any desired product lighter than feed. Thus if the feed is Naphtha it can be converted into LPG if feed is VGO it can produce LPG, Naphtha, ATF, Diesel.
Depending upon the feed quality, product mix desired and the capacity of unit, following process flow configuration can be adopted for hydrocracker. 1. Single stage – for 100% conversion 2. Two stage – for 100% conversion 3. Once through – for partial conversion of feed to products 60-80% In single stage, the unconverted material from fractionator, bottom is recycled to first reactor along with fresh feed. In two stages the unconverted material is routed separately to another reactor.
1. LPG 2. Stabilized light Naphtha 3. Heavy naphtha 4. ATF/SKO high Speed Diesel
In Hydrocracker the VGO feed is subjected to cracking in reactor over catalyst beds in presence of Hydrogen at pressure of 185Kg/cm2 and temperature from 365-441 C. the cracked products separated in fractionator. Light ends are recovered in Debutanizer column. The process removes almost all S and N from feed by converting them into H2S and NH3 respectively, thus the product obtained are free of sulfur and nitrogen compound and saturated. Therefore except for mild NaOH wash for LPG , post treatment is not required for other products.
1. Make up hydrogen section 2. Reaction section 3. Fractionation section 4. Light ends recovery section
The makeup Hydrogen Compression section consist of three identical parallel compressor trains, each with three stage compression during normal operation two trains are in use and compress makeup hydrogen form a pressure swing adsorption (PSA) unit to reaction section the compressed makeup hydrogen is combine with hydrogen recycle gas in the reaction to form reactor feed gas. The makeup hydrogen compression section is also used to compress a mixture of nitrogen and air during catalyst regeneration.
The reaction section contains one reaction stage in a single high pressure loop. Due to reactor weight limit of approximate 400 M Ton. The reaction section consists of two reactors in series. The hydrotreating & hydro-cracking reactions taking place in the reaction stage occurs at high temperature and pressure. A high hydrogen partial pressure is required to promote the hydro0cracking reaction and to prevent coking of the catalyst. An excess of hydrogen is recirculated in the reactor loop for reactor cooling to maintain a high hydrogen partial pressure and to assure even flow distribution in the reactors.
It is used to separate reaction section products into sour gas, unstabilized liquid naphtha, heavy naphtha, kerosene and diesel. Furthermore, bottom containing un-converted product servers as feed to the FCC unit or is sent to tankage. The sour gas and un-stabilized naphtha are sent to the light end section to make fuel gas, LPG and light naphtha.
Light naphtha from the fractionator is sent to de- ethanizer, where gas are removed and sent to amine absorber where the H2S is absorbed in the Amine and H2S free fuel gas is sent fuel gas system. Rich Amine with dissolved H2S is sent to Amine Regeneration unit in sulphur recovery unit. The bottom of dethanizer is sent to debutanizer. For the recovery of LPG, LPG is taken out from the top and sent to treating section where it is washed with caustic for removal of H2S. The stabilized naphtha from the bottom of the stabilizer is sent to hydrogen unit to produce hydrogen.
Feed optimization through a) Hourly spaced velocity b) Basic Nitrogen Sleepage 2) Product Optimization through a) Specification of products. For e.g. for more production of diesel we can add kerosene in diesel.
Diesel Hydro Desulphurisation Unit (DHDS)
The DHDS Unit is set up to reduce sulphur content in the diesel and produce diesel with 250ppm sulphur. However as per the design of this unit, it is capable of producing diesel of purity as good as 50ppm sulphur content from a diesel of 1.2% sulphur content.
Feed -
a. Straight Run gas oil b. Vacuum Diesel c. Vis-breaker gas oil d. Light Cycle oil(LCO) from RFCCU e. LCGO from DCU. Capacity1. Capacity of the unit : 770,000 MTPA 2. Stream factor : 8000 hours per year, 3. Nameplate capacity: 700,000 MTPA.
We studied the whole process occurring in this unit in three parts. 1. The feed section which describes the different units from where DHDS receives diesel as the very feed of this unit and how is it filtered, preheated (various heat exchangers, furnace etc.) before it is sent to the reactor. 2. The reactor section; in this section we studied what kind of reactors are engaged, what kind of catalysts are used what are the operating temperatures and pressures of the reactor, whether the reaction is endothermic or exothermic etc. 3. The last but also an important one, the separation step after which we get our desired product i.e.; sulphur free diesel. The DHDS unit is operated in two modes FEED 1 MODE: to produce ultra-low sulphur diesel (below 40wt ppm) during 80% of the time. FEED 2 MODE: to produce low suphur diesel during 20% of the time. Catalysts used for desulphurization are CoMo and NiMo.
Mercaptans,
sulphides and disulphides react with hydrogen to give corresponding saturated or aromatic compounds and hydrogen disulphide, These reactions are exothermic. Examples- R- SH + H2 → R -H + H2S R-S- R + H2 →2R -H + H2S Other than desulphurisation reaction, other reactions such as denitrification, hydrogenation of oxygenated compounds, hydrogenation of olefins, demetalization are also desirable and they do occur in the process along with desulphurisation. The rate of hydrogenation of olefins is the fastest and that of denitrification is slowest while the rate of desulphurisation is somewhere between the two. There are some undesirable reactions as well, which occur in the process. Such processes are coking, hydrocracking.
Feed to this unit is diesel coming from storage, CDU, VDU, FCCU, Vis-breaker units. It is first passed through a feed prefilter. The feed filter is of semiautomatic, self-cleaning, internal backwashing type capable of removing solid particle of 25 microns or
larger. The filter system consists of three banks of filter elements that are configured and designed to back wash sequentially and independently. During the filtration cycle particulate matter collects on the filter material as a result of which the differential pressure across the system rises. The backwashing is generally required as this differential pressure reaches 1kg/cm2. After pre- filtering is done, the feed enters the feed surge drum (V- 101). The pressure in this feed surge drum is maintained by split range pressure control using fuel gas. There are two valves say V1 and V2. When the pressure increases V1 is opened to release the gas and if the pressure decreases V2 opens and pressurizes the surge drum. The blend from this V-101 is kept at a pressure of 2.8-3 Kg/cm2 which is also the suction pressure of a multistage pump (P-101) used to pump the feed. The feed is pumped through a series of heat exchangers for heat economy before entering into the reactor section. The reactor feed is first allowed to exchange heat with the reactor effluent, for which two heat exchangers have been employed. In the first Heat Exchanger: feed temperature is raised from 45 0 C to 235 0 C.
In the second Heat Exchanger: it is further raised to 275 0 C. The reactor effluent is split into two streams, one is fed to the tube side of Heat exchanger employed to preheat the stripper feed. And the second one is fed to the 2nd reactor feed-effluent heat exchanger. After this the tube side outlet stream of these two heat exchangers is fed into the tube side of 1st reactor feed-effluent heat exchanger. For final heating of the reactor, a vertical cylindrical type fired heater with radiation, convection and air preheater section is employed. It has four burners installed on the floor of the heater, and they are provided with self- inspiriting continuously burning gas pilots. The burner has two combustion zones: Primary (gas is fired at sub stoichiometric air levels) and Secondary (combustion is completed here). The heating of the feed is mainly done by radiation so that heating is done without damaging the feed carrying pipe material. The fuel gas/oil train have strainers and control valves to regulate gas flow to the burner. Combustion air is supplied by two forced draft fans. Air preheater is provided above convection section. Combustion air is passed through the coils to preheat the same. This ensures the heater economy and also stabilizes the flame in the burner. Thermocouples are provided across
the length for measuring the temperature in fired heater. Draft gauges are provided for pressure measurement at burner level in the area above and below the damper. Decoking of tubes needs to be done when coke build up occurs to very high temperatures inside the tube.
The feed from the furnace is fed to the 1st HDS reactor (RB-101). Desulphurization reactions take place leading to H 2S formation and hydrogen consumption. Denitrification reaction takes place and leads to ammonia formation and hydrogen consumption.
The reactor RB-101 consists of two catalytic beds in series. The bed consists of support grid on which alumina balls distributed, and the catalyst is uniformly loaded on the support. Since the HDS reaction is exothermic the fluid temperature reaches very high and thus the equilibrium point reduces. Therefore it is required to bring the temperature down in between. For this purpose hydrogen quench is introduced between the two catalyst beds. Then there is a second reactor which is same as the first but it has only one bed. The reason why first reactor has been equipped with two beds is because most of the
reaction occurs in the first reactor and the sulphur present in the diesel reduces the catalyst activity. Splitting the catalyst into two beds can help for easy replacement of the catalyst (when it loses its activity) as well as lesser amount of catalyst that is to be replaced. Also ammonia injection facility is provided at reactor outlet for catalyst regeneration. Bed pressure drops temperature profile is 326-3730 C. The reactor pressure profile is 56.6 to 60 Kg/cm 2 . The reactor effluents are then sent to the heat exchangers for heat recovery.
Recycle
Gas Compressor: An increase in hydrogen partial pressure results in decrease of coke deposits on the catalyst. The hydro-treatment reaction can be enhanced. Hence, to maintain adequate level of hydrogen partial pressure at each point in the reactor, Recycle Gas Compressor is used. The recycle gas comes from H.P.Amine absorber after removal of H 2S . RCG is a steam turbine driven centrifugal type two stage compressor which develops pressure of 49.4 to 70.1 kg/cm 2 .
Makeup Hydrogen
Compressor –
Separation Section: Reactor effluent from feed-effluent heat exchanger enters the air cooler, where it is cooled down to 58.7 0 C. It is further cooled to 39.2 0 C in water trim cooler and then it is collected in cold separator. In the cold separator it separates into sour gas, sour water and hydrocarbon liquid.
The sour gas (H2S, H2 and lighter hydrocarbons) sent to H.P. Amine absorber section. Here the gas is washed by lean amine entering from the top of the column. H 2S from the gas gets absorbed in lean amine. The nearly H 2 S free gas is recycled back to recycle K.O. drum. The hydrocarbon phase is sent to stripping section where it is stripped using M.P. steam and thus lighter H.C. and H2S are removed as a top product. The top product so obtained is sent to L.P. Amine absorber to recover H2
from the mixture. The H.C. liquid is collected at the bottom section of the stripper and it is cooled. The hydro- treated diesel after being cooled down is passed through a coalescer pre-filter to remove all the remaining water out of the diesel, and we get our final product i.e., the ultra- low sulphur content diesel.
a. Backwash in filters b. Preheating of feed with the product. c. Quenching.
Continuous Catalytic Reforming Unit (CCRU) 1.)
The objective of this unit is Octanizing the process, i.e. to produce a high octane number reformates which is a main component of the gasoline pool and a hydrogen rich gas.
2.)
The feed to this unit is either straight run naphtha or cracked naphtha mixed with straight run naphtha. A rich hydrogen gas (90% purity) and LPG are obtained as valuable byproducts. The reformer can also be run for production of reformate rich in BTX – Benzene, Toluene, and xylenes. Due to the presence of contaminants in naphtha, it is first hydrotreated and then fed to catalytic reforming unit. This process is based on Axen’s licensed technology. It includes three sections: a. NHT section: Naphtha Hydrotreating Section, in which the main aim is to remove contaminants like sulphur (0.5 ppm max), nitrogen (0.5 ppm max), water (4 ppm max) from the feed. 2. b. The Naphtha Catalytic Reformer : which includes reactors, heaters, effluent recovery and stabilization
section and its main aim is to increase the octane number of the process. c. The catalyst recirculation and continuous regeneration – which involves solid handling and moving bed technology. It eliminates the need for shutdown for regeneration of the fixed bed reformers. It also minimises the amount of catalyst in the unit, while allowing high reformates yield and quality. 3.) : The purpose of the Naphtha Hydrotreating unit is to produce a clean desulphurized Naphtha for feeding the Catalytic Reforming unit. Impurities such as sulphur, nitrogen, halogens, diolefins, olefins, arsenic, mercury and other metals are poisonous to the reforming catalyst and therefore must be removed. The main reactions: a. hydrodesulphurization b. hydrodenitrification reactions These are carried out in a fixed bed axial reactor in the presence of hydrogen. The hydrotreating feed is a mixture of straight run naphtha, hydrocracked naphtha. Recycle H2 is mixed with the feed prior to its entry to the reactor. The major contaminants like S, N, O are converted to H2S, NH3 and H2O respectively in the hydrotreating
reactor. The liquid product from the reactor is then stripped to remove H2S, water, NH3 and light hydrocarbons in a stripper column. The hydrotreated naphtha from the stripper end is then directly fed to the Reforming Section. Catalytic Reforming
Capacity of the reforming unit : 0.64 MMTPA, Stream factor : 8000 h/yr. 5.)
Naphtha feed to a CCR unit typically contains C6 to C11 paraffins, napthenes, and aromatics. The purpose of this reforming unit is to produce high octane aromatics from napthenes and paraffins either for use as a high octane blending component as in the case or as a source of specific aromatic compounds. Naphthenes convert rapidly and efficiently to aromatics. Paraffins do not under go conversion easily, requiring higher severity conditions and even the conversion is slow and inefficient. In this process, conversion is achieved by passing naphtha over a slow moving bimetallic catalyst bed in adiabatic
reactor, in the presence of hydrogen at relatively high temperatures and low pressure. The rate of catalyst withdrawal and regeneration ensures a consistently high active catalyst with a low carbon content and controlled chloride/water contents. This maximises yields of both reformate and H2 rich gas. 6.)
For any chemical reaction the thermodynamics dictates the possibility of its occurance and the amount of products and unconverted reactants. Thermodynamics does not mention the time required to reach the equilibrium or the full completion of the reaction. Kinetics discuss the rate of the chemical reaction. Rate of the reaction is dependent upon operating conditions but can be widely modified through the use of properly selected catalayst. Therefore, thermodynamics dictates the ultimate equilibrium composition assuming time is infinite. Kinetics enables to forecast the composition after a finite time. Since time is always limited, when reactions are concurrent kinetics is generally predominant.
7.)
The fundamental reactions can be split into two parts: - Positive reactions: which lead to an increase in octane number, i.e. reactions which we wish to promote. -Negative reactions: which not only can lead to an octane reduction but also a loss in reformate yield, i.e. reactions we wish to avoid. a.) Positive Reactions 1. Dehydrogenation of naphthenes This reaction is rapid and very endothermic. It is promoted by the metal catalyst function and is favoured by high temperature and low pressure. Naphthenes are obvikosuly the most desirable feed components because in addition to being easy to promote they produce by-product hydrogen as well as the aromatic hydrocarbon. 2. Isomerization of paraffins and naphthenes (a) Paraffin isomerization occurs readily in reforming reaction. This reaction leads to an increase in octane when rearranging to the corresponding branched isomer (b) The isomerization of a cyclopentane to a cyclohexane must occur as the first step in converting the C5 naphthene to an aromatic. 3. Paraffin dehydrocyclization It is the most difficult reforming reaction to promote. It requires a difficult molecular rearrangement from paraffin to a naphthalene.
This reaction leads to a significant increase in octane number. It is very endothermic and due to its relative low rate, operating conditions must be more severe for this reaction to occur, resulting in increased coke formation b.) Negative Reactions 1. Hydrocracking Due to difficulty in ring formations and isomerization reactions that the alkylcyclopentanes and paraffins must undergo coupled with the acid function of the catalyst, the possibility of acid-promoted hydrocracking reactions occurring is very strong. 2. Dealkylation This reaction is metal catalysed and also favoured by high temperatures and high pressure does not improve the overall octane number of the reformate and it consumes hydrogen. 3. Dismutation This reaction has little or no influence on the octane number of the reformate. As it leads to heavier molecules, the end point of the reformate stream may increase. The higher molecular weight hydrocarbon also have a higher tendency to coke.
Thermal Power Station (TPS) The thermal power station of IOCL refinery generates power for all fulfilling all power requirements of the refinery and township as well. It has several parts which we will discuss soon. The major inputs of a TPS unit: WATER
Fuel oil
Coal
: The thermal power station burns fuel and uses the resultant to make steam, which derives the turbo generator. The pressure energy of the steam produced is converted to mechanical energy with the help of turbine. The mechanical energy is fed to the generator where the magnet rotate inside a set of stator winding and thus electricity is produced.
Different equipment that are used in TPS 1. Boiler: It is a device for producing steam. There are two types of boilers.
a. Fire tube boiler b. Water tube boiler Here boiler used is of water type. In the boiler, heat energy transfer takes pace through the walls and drum. The gases lose their heat to water in the boiler. 2. Turbine Generator: Turbine is form of heat engine in which available heat energy in the form of steam is converted into kinetic energy to rotate the turbine by steam expansion. In the TPS unit of IOCL refinery there are five huge turbine generators. It consists of three stages: high pressure, intermediate pressure and low pressure. The shaft is coupled with generator. The generator converts the kinetic energy of the rotating shaft to electric energy. Condenser: In condenser, the water passes through various tubes and steam passes through a chamber containing large number of tubes. The steam gets converted to water droplets, when steam comes in contact with water tubes. The condensate is used again in boiler as it is dematerialized water which was in tubes, during process of condensation. This water is sent to cooling tower.
3. Cooling Towers: It is a high cylindrical structure designed to cool water by natural draught. The cross section area is less at the centre just to create low pressure so that the air can lift up due to natural draught and can carry heat from water drops. The upper portion is also diverging for increasing the efficiency of cooling tower. 4. Water Clarifier: It receives impure water from raw water storage. In raw water storage big suspended particles settle down. CANAL →→ RAW WATER STORAGE →→ LAKE →→ WATER CLARIFIER In water clarifier the purification of raw water is done in two processes. a. Coagulation: in coagulation potash alum is added in the water. In this process suspended and colloidal particles are removed. b. Chlorination: chlorine is added to the water which have disinfectant action and it kills the harmful bacteria’s , germs and destroyed the pathogenic microbes.
5. Valves: A valve is a device that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids,
or slurries) by opening, closing or partially obstructing various passages. In an open valve, fluid flows from higher pressure to lower pressure. Valves used in IOCL Refinery: a. Gate Valve: gate valves are ideally suited for on/off services. A gate valve functions by lifting a rectangular or circular gate out of the path of the fluid. When the valve is fully open, gate valves are full bore, meaning there is nothing to obstruct the flow because the gate and pipeline diameter have same opening. But gate valves do have low pressure limitations, and are not optimal in applications that require cleanliness. They are excellent for use anywhere a shutoff valve is needed. They are designed to minimize pressure drop across the valve in fully opened position and stop the flow of fluid completely. b.Globe Valve: Globe valves were spherical in earlier times which gave them their name, but modern globe valves are not necessarily spherical. They are used for applications requiring throttling and frequent operation. C. Non Return Valve: It is a valve that normally allows fluid to flow through it in only one direction. They are
two port valves, one for fluid to enter and the other for fluid to leave. They work automatically and most are not controlled by a person or any external control. An important concept in these valves is the cracking pressure which is the minimum upstream pressure at which the valve will operate. d. Butterfly Valve: The butterfly valve offers many advantages that include quarter turn, openness for less plugging and good control capabilities. Both manual and control version are used. A butterfly valve is a flow control device that incorporates a rotational disk to control the flowing media in a process. The disk is always in the passageway, but because it is relatively thin, it offers little resistance to flow.
8.) Process Optimization: a. ) Recontacting b. ) Reuse of H 2 c. ) Preheating of inlet with outlet. d. ) Steam generation through high temperature gas.
EQUPIMENTS USED IN REFINERY Broadly two types of equipments are used in refinery They are not in motion and remain at their position. Example : pipes, column, valves, heat exchangers, vessels, drum. They are in motion. Examples: pumps, compressors.
A.
Pump is a device which adds the energy of a liquid or gas causing an increase in its pressure and perhaps a movement of the fluid. There are many forms of energy, but when pumps are being considered, use can be made of the energy equation as follows. A simple pumping system consists of a suction branch, a pump and a discharge branch.
a. Characteristics of a Pump1. For circulation of water 2. For pumping the fluid (petrol, diesel, crude oil, etc) in reactor columns at high pressure 3. For the storage in the fluid tanks 4. For sending the fluid to the filling stations
5. For sending the crude from storage tanks to the processing units b. Types of Pumps1. Rotary pump/ centrifugal pump: Like most pumps, a centrifugal pump converts mechanical energy from a motor to energy of a moving fluid. A portion of the energy goes into kinetic energy of the fluid. Fluid enters axially through the eye of the casting, is caught up in the impeller blades, and is whirled tangentially and radially outward until it leaves through all circumferential parts of the impeller into the diffuser part of the casting. The fluid gains both velocity and pressure while passing through the impeller. 2. Positive displacement pump A positive displacement pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into the discharge pipe. Some positive displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is through each cycle of operation. They are commonly referred to as constant volume pumps.
B.) HEAT EXCHANGER A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall to prevent mixing or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power plants, chemical plants, petrochemical plants, petroleum refineries, natural gas processing, and sewage treatment. The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air. a. Types of heat exchangers 1. Cross flow heat exchanger In compact heat exchangers, the two fluids usually move perpendicular to each other and such flow configuration is called crossflow. There are further two types of cross flow heat exchangers a. Unmixed Flow b. Mixed Flow 2. Shell and Tube heat exchanger Shell and tube heat exchangers contain a large number of tubes packed in a shell with their axes parallel to that of the shell. Baffles are commonly placed in the shell side fluid to flow across
the shell to enhance heat transfer and to maintain uniform spacing between the tubes. c. Application for cross and parallel flows 1. Cross flow (a) Larger effective LMTD (b) Greater potential energy recovery The advantage of the larger LMTD, is that it permits a smaller heat exchanger area, for a given heat transfer. This would normally be expected to result in smaller, less expensive equipment for a given application. 2. Parallel flow (a) Where the high initial heating rate may be used to advantage (b) Where it is required that the temperature developed at the tube walls are moderate In heating very viscous fluids, parallel flow provides for rapid initial heating and consequent decrease in fluid viscocity and reduction in pumping requirement. In applications where moderation of the tube wall temperatures is required, parallel flow results in cooler walls. This is especially beneficial in cases where the tubes
are sensitive to fouling effects which are aggravated by high temperature. d. Use of heat exchanger in IOCL Panipat Refinery 1. Condensation of solvents and multiple material mixtures 2. Cooling/heating of reactors and production containers 3. Cooling and heating of intermediate products 4. Cooling of hydrocarbons 5. Cooling of water circuits 6. Benzene heat recovery 7. Heat recovery within petrochemical processes
C.) Gas Compressors A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor. Compressors are similar to pumps; both increase the pressure on a fluid and both transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a
gas. Liquids are relatively incompressible; while some can be compressed, the main action of a pump is to pressurize and transport liquids. a. Types of Compressors (a) Centrifugal compressors Use a rotating disk or impeller in a shaped housing to force the gas to the rim of the impeller, increasing the velocity of the gas. A diffuser (divergent duct) section converts the velocity energy to pressure energy. They are primarily used for continuous, stationary service in industries such as oil refineries, chemical and petrochemical plants and natural gas processing plants. Their application can be from 100 HP to thousands of HP. With multiple staging, they can achieve high output pressure greater than 69MPa. Two stage compressor is used for highly compressible gas for getting high pressure at the exit. In the IOCL Panipat Refinery, the WGC is used for the compression of LPG which is compressed in two stage having very high compression ratio in each stage. WGC is working on the principle of centrifugal action. It contains 6 impellers, 3 for each stage compression. (b) Positive displacement compressor Positive displacement compresssors work by forcing air into a chamber whose
volume is decreased to compress the air. It is further of two types: 1. Single acting It means the air drawn in and compressed on one side of the piston. The other side is exposed to the crankcase of the compressor. In this the downward stroke of the piston draws the air in, and upward stroke compresses it. 2. Double acting Compressors have the compression chamber on both sides of the piston. On down stroke air is drawn in on the top of the piston while air is compressed on the bottom side. On the upstroke air is drawn into the bottom side while the air is compressed on the top side. Double acting machines require sealing of the piston rod so a crosshead is used to eliminate thee angular element of the rod. (c) Reciprocating compressor A reciprocating compressor or piston compressor is a positive displacement compressor thar uses pistons driven by a crank shaft to deliver gases at high pressure. The intake gas enters the suction manifold, then flows into the compression cylinder where it gets compressed by a piston driven in a reciprocating motion via a crankshaft, and is then discharged. b. Application include oil refineries, gas pipelines, chemical plants, natural gas processing plants and refrigeration plants.
Heat Exchanger Design 102 A/B DHDS Unit (Project-1)
