Pyrophoric Ignition Hazards in Typical Refinery Operations
A pyrophoric material is a liquid or solid that, even in small quantities and without an external ignition source, can ignite within 5 minutes afte r coming in contact with air. In oil and petrochemical industry, this only partially defines the concern. We also need to be concerned with the fact the pyrophoric material can create heat which can ignite residual hydrocarbons associated with the equipment containing the pyrophoric material. Example pyrophoric materials include alkali metals and many organometallic compounds such as alkylmagnesiums, alkylzincs, and of course course pyrophoric iron sulfide. Nickle carbonyl in some catalysts. Pyrophoric compound + oxygen (typically (typically air) ---> Oxide of the compound + heat Sometimes with several intermediate reaction steps Can be very reactive or very slow to react Can vary with conditions, humidity, temperature, particle size, degre e of disbursement in air, etc.
Conditions required to form pyrophoric iron sulfide H2S concentration > 1% (can form at lower concentrations but typically not in concentrations that are a concern) Iron scale or rust (FeS) Less than a 1:1 ratio of oxygen to H2S (some oxygen is r equired to form the rust but if insufficient oxygen is present the reaction reac tion with H2S cannot go to completion)
Pyrophorics have been known to form in refinery equipment such as : Crude oil tanks Asphalt tanks Sour water tanks Vessels in sour service such as coke drums, distillation distillation columns, inlet separators, pig receiver / launchers Reactors API Separators
Marine tankers and barges Portable tanks and tote bins Mitigation methods : Most effective method is chemical neutralization before opening the equipment; potassium permanganate solution (typically around a 1% solution, circulate and check for color) Keeping the deposits and scale wet until it can be safely removed to a remote area and allowed to dry Maintain a constant air ventilation to ensure there is plenty of oxygen to allow the reaction to go to completion, preventing the formation of the pyrophoric intermediates Replace components that contain sulfur compounds Use nitrogen or other inert gases to keep oxygen out (obviously difficult and adds hazards of its own) Quickly move scale and potential pyrophoric deposits to a remote area and monitor in case ignition does oc cur Source : Doug Jeffries Chief Fire Protection Engineer , Chevron
Pyrophoric Materials Recommendations for Safe Use of Pyrophoric Materials Definition and Hazards Controlling the Hazards Personal Protective Equipment Designated Areas Important Steps to Follow Storage Disposal Emergency Procedures References
Definition and Hazards Pyrophoric materials are substances that ignite instantly upon exposure to oxygen. They can also be water-react ive, where heat and hydrogen (a flammable gas) are produced. Other common hazards include corrosivity, teratogenicity, and organic peroxide formation, along with damage to the liver, kidneys, and central nervous system. Examples of such materials include metal hydrides, finely divided metal powders, nonmetal hydride and alkyl compounds, white phosphorus, alloy of reactive mater ials and organometallic compounds, including alkyllithiums. Failure to follow proper handling techniques could result in serious injury or death.
Controlling the Hazards If possible, use safer chemical alternatives. Limit the amount purchased and do not accumulate unneeded pyrophoric reagents. BEFORE working with pyrophoric reagents, read the relevant MSDS sheets and associated technical bulletins. The MSDS must be reviewed before using an unfamiliar chemical and periodically as a r eminder. A Standard Operating Procedure and Hazard Assessment should be prepared for each process involving pyrophoric or water-reactive materials.
On-the-job training should be completed and documented. Conduct an emergency drill reviewing the procedures to be taken in an emergency. Review the location of the safety shower, eyewash, telephone (dial 911), and fire extinguisher.
Personal Protective Equipment ALWAYS wear the proper PPE at all times when handling pyrophoric materials. Eye Protection: Chemical Splash goggles or safety glasses must be worn whenever handling pyrophoric chemicals. Ordinary prescription glasses will NOT provide adequate protection. A face shield is required any time t here is a risk of explosion, large splash hazard or a highly exothermic reaction. Po rtabl shields are also acceptable. Skin Protection: Gloves must be worn when handling pyrophoric chemicals. Nitrile gloves should be adequate for handling most of these in general laboratory settings but they ar e combustible. Be sure to use adequate protection to prevent skin exposures. Sigma-Aldrich recommends the use of nitrile gloves underneath neoprene g loves. Avoid wearing synthetic clothing while working with pyrophorics. A lab coat or apron (not made from easily ignited material like nylon or polyester) must be wor n. Special fire-resistant lab coats made from Nomex are mor e expensive, bu recommended for labs using these reage nts routinely. No open toe shoes are allowed.
Designated Areas Fume Hood: Many pyrophoric chemicals release noxious or flammable gases and should be handled in a laboratory hood with the sash down at the lowest feasible position. In addition, some pyrophoric materials are stored under kerosene (or other flammable solvent); therefore the use of a fume hood (or glove box) is required to prevent the release of flammable vapors into the laboratory. Glove (dry) box: Glove boxes are an excellent device to control pyrophoric chemicals when inert or dry atmospheres are required. When using a disposable plastic syringe, glove boxes are also recommended.
Important Steps to Follow A “dry-run” of the experiment should be performed using low -hazard materials, such as water or solvent, as appropriate. If possible, use the “buddy system”. Working alone with pyrophorics is strongl y discouraged.
Conduct the procedure only after a supervisor has observed the user performing the proper technique unassisted. All glassware used for pyrophorics should be oven-dried and free of moisture. Keep an appropriate fire extinguisher or extinguishing material close at hand. Remove all other flammable material from the hood, as well as any clutter. Secure the pyrophoric reagent bottle to a stand. Sigma Aldrich recommends the use of a long needle, 1-2 foot, and a syringe that is twice the volume of liquid to be transferred. Secure the syringe so if the plunger blows out of the body it, and the contents will not splash anyone. Avoid the transfer of large volumes (>20 mL) using a syringe. The cannula technique is recommended. Further details, such as safe experiment set up diagrams, can be found in the references listed below.
Storage Pyrophoric chemicals should be stored under an atmosphere of iner t gas or under kerosene as appropriate. Avoid areas with heat/flames, oxidizers, and water sources. Containers carrying pyrophoric mater ials must be clearly labeled with th correct chemical name and hazard war ning. Do NOT allow pyrophoric chemicals stored in solvent to dry out. Check periodically to ensure there is a visible amount of solvent in the bottle.
Disposal All materials that contain or are contaminated with pyrophoric chemicals should be disposed of as hazardous waste. Submit a Hazardous Materials Pick-up Request form to REM. Proper and complete hazardous waste labeling of containers is vital. A container with residual material must NEVER be o pened to the atmosphere. If the pyrophoric chemical was originally stored in solvent and is dried, please hydrate the chemical with an appropriate
solvent before pick-up. The best solvent to use is the same solvent used for the solution of the original reagent.
Emergency Procedures Keep material within arm’s length to absorb spills. Powdered lime, dry sand, Celite® (diatomaceous earth), or clay based
kitty litter should b used to completely smother and cover any spill that occurs. If a person is exposed, or on fire, the use of the stop, drop, and roll method, safety shower, a fire blanket, or fire extinguisher are the most effective means of controlling clothing on fire. If a safety shower is available, keep the person under the shower for at least 15-20 minutes to ensure all chemicals are washed away. The recommended fire extinguisher is a st andard dry powder (ABC) type. Class D extinguishers are recommended for combustible solid metal fires (such as sodium), but not for organolithium reagents. Call 911 for emergency assistance
References: Aldrich Technical Bulletins AL-134 and AL-164 Handling Pyrophoric Reagents from U.S. Dept. of Energy and Pacific Northwest National Laboratory Chemical Hygiene and Safety Plan from Berkeley National Laboratory Laboratory Safety Fact Sheets #34 and #37 on Pyrophoric Reagents
Pyrophoricity From Wikipedia, the free encyclopedia Not to be confused with Porphyria.
Plutonium's pyrophoricity can cause it to look like a glowing ember under certain conditions. A pyrophoric substance (from Greek πυροφόρος, pyrophoros, "fire-bearing") is a substance that ignites spontaneously in air at or below 54.55 °C (130.19 °F).[1] Examples are iron sulfide and many reactive metals including uranium, when powdered or thinly sliced. Pyrophoric materials are often waterreactive as well and will ignite when they contact water or humid air. They can be handled safely in atmospheres of argon or (with a few exceptions) nitrogen. Most pyrophoric fires should be extinguished with a Class D fire extinguisher for burning metals. Contents 1 Uses 2 Handling 3 Pyrophoric materials 3.1 Solids 3.2 Liquids 3.3 Gases 4 Notes
5 External links Uses The creation of sparks from metals is based on the pyrophoricity of small metal particles, and pyrophoric alloys are made for this purpose.[2] This has certain uses: the sparking mechanisms in lighters and various toys, using ferrocerium; starting fires without matches, using a firesteel; the flintlock mechanism in firearms; and spark-testing ferrous metals. Handling See also: air-free technique Small amounts of pyrophoric liquids are often supplied in a glass bottle with a PTFE (Teflon)-lined septum. Larger amounts are supplied in metal tanks similar to g as cylinders, designed so a needle can fit through the valve opening. A syringe, carefully dried and flushed of air with an inert gas, is used to extract the liquid from its container. Pyrophoric solids require the use of a sealed glove box flushed with inert gas. Glove boxes are expensive and require maintenance. Thus, many pyrophoric solids are sold as solutions, or dispersions in mineral oil or lighter hydrocarbon solvents. Mildly pyrophoric solids (such as lithium aluminium hydride and sodium hydride) can be handled in the air for brief periods of time, but t he containers must be flushed with inert gas before storage. Pyrophoric materials Solids Alkylated metal alkoxides or nonmetal halides (diethylethoxyaluminium, dichloro(methyl)silane) Alkali metals (lithium, sodium, potassium, rubidium, caesium), including the alloy NaK Copper fuel cell catalysts, e.g., Cu/ZnO/Al2O3[3] Grignard reagents (compounds of the form RMgX) Finely divided metals (iron,[4] aluminium,[4] magnesium,[4] calcium, zirconium, uranium, titanium, bismuth, hafnium, thorium, osmium) Some metals and alloys in bulk form (cerium, plutonium) Used hydrogenation catalysts such as Raney nickel (especially hazardous because of the adsorbed hydrogen) Metal hydrides (sodium hydride, lithium aluminium hydride, uranium trihydride) Iron sulfide: often encountered in oil and gas facilities where corrosion products in steel plant equipment can ignite if exposed to air.
Partially or fully alkylated derivatives of metal and nonmetal hydrides (diethylaluminium hydride, trimethylaluminium, triethylaluminium, butyllithium), with a few exceptions (i.e. dimethylmercury and tetraethyllead) Lead & Carbon powders produced from decomposition of lead citrate[5][6] Uranium is pyrophoric, as shown in the disintegration of depleted uranium penetrator rounds into burning dust upon impact with their targets. In finely divided form it is readily ignitable, and uranium scrap from machining operations is subject to spontaneous ignition.[7] Methane tellurol (CH3TeH) White phosphorus Plutonium: several compounds are pyrophoric, and it causes some o f the most serious fires occurring in United States Department of Energy facilities.[8] Petroleum hydrocarbon (PHC) sludge. Liquids Diphosphane Metalorganics of main group metals (e.g. aluminium, gallium, indium, zinc and cadmium etc.) Triethylborane tert-Butyllithium Hydrazine is hypergolic with oxidants like dinitrogen tetroxide, but not truly pyrophoric. Gases Arsine Metal carbonyls (dicobalt octacarbonyl, nickel carbonyl) Nonmetal hydrides (diborane, germane, silane) Notes SEMI, standard F6-92, Guide for Secondary Containment of Hazardous Gas Piping Systems, as cited by ChemiCool.com N. Pradeep Sharma, Dictionary Of Chemistry C.W. Corti et al. / Applied Catalysis A: General 291 (2005) 257
Angelo & Subramanian (2008), Powder metallurgy: science, tec hnology and applications, p. 48, "Powders of aluminium, iron and magnesium are highly pyrophoric in nature" Pyrophoric lead composition and method of making it The Reaction of Pyrophoric Lead with Oxygen(registration required) DOE | Office of Health, Safety and Security | Nuclear Safety and Environment | Uranium, retrieved 3 September 2013; archived on 24 August 2010. DOE | Office of Health, Safety and Security | Nuclear Safety and Environment | Plutonium, retrieved 3 September 2013; archived on 28 September 2010.
