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flare system design manualA preview of this full-text is provided by Springer Nature. Download full-text PDF Read full-text Download citation Copy link Link copied Read full-text Download citation Copy link Link copied Figures (1) Abstract and Figures The flare is a last line of defense in the safe emergency release system in a refinery or chemical plant. It is used to dispose of purged and wasted products from refineries, unrecoverable gases emerging with oil from oil wells, vented gases from blast furnaces,Flares are also used for burning waste gases from sewage digesters process, coal gasification, rocket engine testing, nuclear power plants with sodium, water heat exchangers, heavy water plants, and ammonia fertilizer plants.They were designed for engineers to do preliminary designs an d process specification s heets. The final design must always be guaranteed for the s ervice selected by the manufacturing vendor, but these guidelines will greatly reduce the amount of up front engineering hours that ar e required to develop the final design. The guidelines are a training tool for y oung engineers or a resource for engineers with experience. This document is entrusted to the recipient personally, but the copyright remains with us. It must not be copied, reproduced or in any way communicated or made accessible to third parties without our written conse nt. VIII) Social Requirements 1 6 Design Consideration 1 6 DEFINITIONS 1 8 NOMENCLATURE 20 Greek Letters 21 THEORY Elevated Flare Tips Sizing 2 2 Stack Support 2 4 Flare Stack Diameter 2 5 Vent Stack 2 7 Separation of Flare Headers 27 Load of Flare Systems 2 9 Sizing the Flare Line 3 0 Sizing Piping, Headers, and Valves 31 Flame Length 3 3 Flame Distortion Caused by Wind Velocity 34 They were designed for engineers to do preliminary designs an d process specification s heets. It must not be copied, reproduced or in any way communicated or made accessible to third parties without our written conse nt.http://dayalindia.com/userfiles/farmgate-milk-price-manual.xml
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They were designed for engineers to do preliminary designs an d process specification s heets. Diffusion Type Seal 68 Selection of Flares 6 9 Flaring of H 2 S 70 Flare Gas Recovery 7 1 Flare Test Method 72 Flaring Efficiency 73 Reducing Flare Pulsing and Noise 75 Flare Stack Safety 75 Flare Stack Accident and Incident 83 APPLICATION Example 1: Sizing of Elevation Vent Stack 9 0 Example 2: Sizing of Elevation Flare Stack (simple approach method) 92 Example 3: Sizing of Elevation Flare Stack (Brzustowski’s and Sommer’s Approach) 99 Example 4: Thermal Radiation Consideration 104 Appendix A 107 Appendix B 112 They were designed for engineers to do preliminary designs an d process specification s heets. Appendix C 113 REFERENCES 114 LIST OF TABLE Table 1: Material for low-temperature service 28 Table 2: Combination of flare header 28 Table 3: Emissivity values for flared gases 50 Table 4: Effect of Thermal Radiation 51 Table 5: Recommended Design Total Radiation 51 Table 6: Type of Seal Drum 65 Table 7: Comparison between Elevated Flare and Multijet Flare 69 Table 8: Surface Emmisivity for Material 106 Table A.1: Limits of Flammability of Gases and Vapors. in Air 108 Table A.2: Limits of Flammability of Gases and Vapors. in Air 109 Table A.3: Example Calculation of Flammable Limits 110 LIST OF FIGURE Figure 1: Steam Assisted Elevated Flare System 10 Figure 2: Typical Enclosed Ground Flare 12 Figure 3: Simplifield representation of a flare gas recovery unit integrated with an They were designed for engineers to do preliminary designs an d process specification s heets. INTRODUCTION Scope The flare is a la st line of defencein the safe emergency release system in a refinery or chemical plant. It is use d to dispose of purged and wasted p roducts from refineries, unrecoverable gases emerging with oil from oil wells, vented gases from blast furnaces, unused gases from coke ovens, and gaseous water from chemical industries.http://fortis21vek.ru/uploads/file/farmers-tree-planting-manual.xml Flares are also used for burning waste gases from sewage digesters process, coal gasification, rocket engine testing, nuclear power plants with sodium, water heat exchangers, heavy water plants, and ammonia fertilizer plants. The flare provides a means of safe disposal of the vapor streams from its facilities, by burning them under controlled condit ions such that the adjacent equipment or personnel are not exposed to hazards, and at t he same time obeying the environmental regulation of pollution control and public relations requirements. The c hemical process used for flaring is a high temperature oxidation re action to burn combustible components, mostly hydrocarbons, or wast e gases from industrial operations. In combustion, the gaseous hydro carbon (nat ural gas, propane, ethylene, propylene, butadiene, butane an d etc) reacts with atmospheric o xygen to form carbon dioxide (CO 2 ) and water. Several b y-products formed will be carbon monoxide, hydrogen and others dependent upon what is being burned. Efficiency of hydrocarbon conve rsion is generally over 98. They were designed for engineers to do preliminary designs an d process specification s heets. Pilot Burners Flare Tip Flare Types In industrial plants the most common utilized flare systems are elevated flares and grou nd flares. Selection of the type of flare is influenced by several factors, such as availability of space; the characteristics of th e flare gas (composition, quantity and pressure); economics; investment and operating costs; public relations and regulat ion. I) Elevated Flare Elevated flare (refer Figure 1) is the mo st commonly u sed type in refineries and chemical plants. They have l arger capacities than ground flares. The waste gas stream is fed through a stack from 32ft to over 320 ft tall and is combu sted at the tip of the stack. The elevated fla re, can be steam assisted, air assisted or non-assisted.http://fscl.ru/content/dukane-24a700b-manual If adequately elevated, this type of flare has the best dispersion chara cteristics for malodorous and toxic combustion products. Capital costs are relatively h igh, and an appreciable plant area may be rendered unavailable for plant equipment, because of r adiant heat considerations. They were designed for engineers to do preliminary designs an d process specification s heets. Knock-out Drum Drain Gas Collection Header and Transfer Line Water Sear Purge Gas Air Line Gas Line IgnitionDevice Steam Line Gas Barrier Steam Nozzles Flare Stack Figure 1: Steam Assisted Elevated Flare System They were designed for engineers to do preliminary designs an d process specification s heets. II) Ground Flare A ground flare is where the combustion takes place at ground level. It varies in complexity, and may consist either o f conventional flare burners discharging ho rizontally with no enclosure or of multiple burners in refractory-lined steel enclosures. The type, which has been used almost exclusively, is the multijet flare (en closed type). Compare to elevated flare, ground flare can achieved smokeless operation as well, but with essentially no noise or lum inosity problems, pro vided that t he design ga s rate to the flare is not exceeded. However, it have poor dispersion of combustion product because its stack is near to grou nd, this may result in severe air pollution or hazard if the comb ustion prod ucts are toxic or in the event of flame-out. Capital, operating and maintenance requirements cost are higher. Genera lly, it is not practical to install multijet flares large enough to burn the maximum release load, b ecause the usual arrangement of multi jet flare system is a combination with an elevated over-capacity f lare. They were designed for engineers to do preliminary designs an d process specification s heets. UV Flame Scanner SightPort Burner Burner Arrangement Landfill Gas Inlet Thermocouple Enclosed flare Combustion Chamber Exhaust Gas (1500 o F) 63,179 scfm) Landfill gas From collection Wells and header system 1,000scfm Air Damper (2) UV Flame Scanner SightPort UV Flame Scanner SightPort Air Inlet Air Inlet 5 to 10” Refractory Lining (2”) Base on sources to flare Landfill Gas Inlet Concrete Pad Figure 2: Typical Enclosed Ground Flare They were designed for engineers to do preliminary designs an d process specification s heets. Flare System Typical flare system consists of: i) Gas collec tion header and piping for collecting gases from processing units, ii) A knockout drum to remove and store cond ensable and entrained liquids, iii) A p roprietary seal, water seal, or purge gas supply to prevent flash-back iv) A single or multiple burner unit and a flare stack, v) Gas pilots and an igniter to ignite the mixture of waste gas and air and vi) A provision for external momentum force (steam injection or forced air) for smokeless flaring. Flare System is represented in Figure 3. Figure 3: Simplified representation of a flare gas recovery un it integrated with an existing flare system. They were designed for engineers to do preliminary designs an d process specification s heets. Design Factors Is very important for the flare designer to understand seve ral factors which can affect his flaring system design, the major factors influencing flare system design are. Flow rate; ? Gas composition; ? Gas temperature; ? Gas pressure available. Utility costs and availability. Safety requirements. Environmental requirements. Social requirements. I) Flow Rate How flow rate will affect the design of flare system. No rmally the designer of the flare system will follow exactly t he flow data provided, therefore overstated of the flows will lead to oversized of flare equipment which lead to more expensive capital and operating costs and can lead t o short service life as well. Understated the flow can result in a design of an unsafe system. Flow rate obviously affects the mechanical size o f flare equipment, increased flow will results increase o f thermal radiation from an ele vated flare flame, which have direct im pact on the height and location of a flare stack. II) Gas composition The combustion gas products are depend on the feed gas composition, by studying the feed gas composition the potential combust ion product can be determined and burning characteristic can be identified. It enables the design c ompany to shown the weight ratio of hydrogen to carbon in gas which indicates the smoking t endency of t he gas. Some gas, such as hydrogen sulfide will need special design f or metallurgies, therefore detail of the feed gas compositions to de sign the flare system is very im portant and should be determined accurately. Related to regulatory mandates Depends on the gas stream released They were designed for engineers to do preliminary designs an d process specification s heets. Th is can be solved by ad ding a liquid removal equipment such as a knockout drum. IV) Gas Pressure Available The gas pressure available for the flare is determ ined by hydraulic analysis of the complete pressure relief system from the pressure re lieving devices to the flare burner. This parameter is a factor for smokeless burning design of flare. S ome flare design companies have proved that smokeless burning can be enhancedby converting as much of the gas p ressure available as possible into gas momentum. V) Utility Costs and Availability To achieve smokeless op eration, it is necessary to add an assist medium to increase the overall momentum to the smokeless burning le vel. The common medium is steam which is injected into nozzles of the flare syst em. In order to achieve this o bjective, local energy costs, availability and reliability must be taken into account in selecting the smoke-suppression medium. Other utilities are needed to be in place are purge gas and pilots. The quantity required is depending on the size of the flare sys tem. Pilot gas consumption will also be influenced by the combustion c haracteristics of the waste gases. They were designed for engineers to do preliminary designs an d process specification s heets. VI) Environmental Requirements The primary environment al requirement is the need for smokeless burning to protect the environment from pollution, it may be necessary to inject an assist medium such as steam in order to achieve smokeless burning. Unfortunately the injection of the steam and the turbulence created by the mixing of steam to so lve the smoke burning problem causes the emission of sound. The sound level at inside and outside the plant boundary is often limited by regulation. VII) Safety Requirements The ma in safety concern for the flaring system is thermal radiation issues. The allowable radiation from the flare flame to a given point is freq uently specified based on the owne r's safety practices by following the safety regulation. Special consideration should be given to radiation limits for flares located close to the plant bounda ry. VIII) Social Requirements Although the plant operation has complied with the environmental regulation, sometime the outcome resulting flare system may not me et the expectations of the plant's neighbors. Example: A smokeless flame may meet the regulatory requirements, but the neighbors may complaint due to light and noise from flare system. They were designed for engineers to do preliminary designs an d process specification s heets. Design Consideration When de signing the flare system, several important parameters have to be consider, there are flare head design, flare exit velocity, VOC (Volatile Organic Compounds) heating value, and whether the flame is assisted by steam or air. The design should be based on consideration bellow as well, 1. Flare Spacing, Location, and Height. Radiant h eat ? Burning liqu id fall out. Pollution lim itations 2. Flare Capacity and Sizing. Flare design capacity is design to handle largest vapor release from pressure relief valve, vapor blow down and other emergency sy stem 3. Flashback Seals- flashback protection, which pre vents a flame front from trave lling back to the ups tream piping and equipmen t. Sizing of flare systems is a function of maximum allowable back p ressure on pressure relief valves and other sources of release into the emergency systems. They were designed for engineers to do preliminary designs an d process specification s heets. Flare Safety Flare Stack Accidents and Incidents The most frequent causes of flare accidents are: 1. Internal explosion 2. Liquid carryover 3. System obstructions 4. Faulty maintenance procedures 5. Ignition loss Incidents categories:.They were designed for engineers to do preliminary designs an d process specification s heets. Stack Explosions Most of incidents in flare stack is flame out or stack explosions. There are m any problem that may cause a stack explosion. 1) The stack was supposed to be purged with inert gas. However, the flow was not measu red and had been cut back almost to zero to save nitrogen. Air leaked in through the large bolted joint between unmachined surfaces. The flare had not been lit for some time. Shortly after it was relit, the explosion occurred the next time some gas was put to stack. The mixture of gas and air moved up the stack until it was ignited by the pilot flame. To prevent similar incidents from happening again: 1. Stack should be welded. They should not contain bolted joints between unmachined surfaces. 2. There should be a continuous flow of gas up eve ry stack to prevent air d iffusing down and to sweep away sma ll leaks of air into the stack. The continuous flow of gas does not have to be nitrogen a waste gas stream is effective. A higher rate is required if hydrogen or hot condensable gases are being flared. If possible, hydrogen should be discharged through a separate vent stack and not mixed with othe r gases in a flare stack. 3. The atmosphere inside every stack should be m onitored regularly for oxygen content. Large stack should be fitted with oxygen analyzers that a larm at 5 (2 if hyd rogen is present). Small stacks should be checked with a portable analyzer. They were designed for engineers to do preliminary designs an d process specification s heets. It must not be copied, reproduced or in any way communicated or made accessible to third parties without our written conse nt. 2) Th ree explosions occurred in a flare stack fitted, near the tip, with a water seal, which was intended to act as a flame arrestor and prevent flame s from passing down the stack. The problems started when, as a result of incorrect valve settings, hot air was added to the stack that was burning methane. An explosion occurred, which probably damaged the water seal, though no one realized this at the time. St eam was automatically injected to the stack, and the flow of the methane was tripped. This extinguished the flame. When fl ow wa s restarted, a second explosion occurred and as the water seal was damaged, this one traveled right down th e stack into the knock-out drum at th e bottom. Flow was again restarted and this time the explosion was louder. The operating team then decided to shutdown the plant. One should not restart a plant after an explosion until we know why it occurred. Blocked Stack 1) Vent stack became blocked by ice because cold vapor (at -100 o C) and steam were passed up the stack together. The c old gas met the condensa te running down the walls a nd caused it to freeze. A lique fied gas tank was overpressured, and a sm all split resulted. The stack was design to operate without stea m. But the steam was then introduced to make sure that the cold gas dispersed and did not drift down to ground level. 2) On other occasions, blowdown lines or stack have become blocked in cold weather because benzene or cyclohexane, both of which have freezing points of 5 o C, were discharged through them. Steam tracking of the line s or stack may be necessary. 3) Blowdown lines should never be designed with a dip in them, or liquid may accumulate in the dip and exert a back pressure. This has caused vessels to be overpreassured. 4) A blowdown line that was not adequately supported sagged when exposed to fire and caused a vessel to be overpressured. They were designed for engineers to do preliminary designs an d process specification s heets. It must not be copied, reproduced or in any way communicated or made accessible to third parties without our written conse nt. 5) Water seals have frozen in cold weather. They should not be used except in l ocales where freezing cannot occur. 6) Vent stacks are sometimes fitted with flame arrestors to prevent a flame on the end of the stack from traveling back down the stack. Th e arrestors are liable to choke u nless regularly cleaned. They are also unnecessary, because unless the gas mixture i n the stack is flammable, the flam cannot travel down the stack. If the gas mixture in the st ack is flammable, then it may be ignited in s ome other way. Stack should therefo re be swept by a continuous flow of gas to prevent a flammable mixture from forming. 7) Molecular se als have been chocked by carbon from incompletely burn ed gas, and water seals could be chocked in the s ame way. The relief valve on a liquid hydrogen tank discharge to atmosphere through a short stack. The escaping hydrogen ca ught fire. The fire service poured water down the stack, the wa ter froze, and the tank was over pressured and split. The fire should have been extinguished by inje cting nitrogen up the stack. They were designed for engineers to do preliminary designs an d process specification s heets. DEFINITION Back Pressure- Back pressure is the sum of the superimposed and build-up back pressures. The pressure that exists at the outlet of a pressure relief device is as a result of the pressure in the discharge system. Gas Blower - Device for blowing air to flare system. Blowdown - The difference between the set pressure and the closing pressure of a pressure relief valve, expressed as a of the set pressure of in pre ssure units. Closed Disposal System- Disposal system which is capable of containing pressure that is different from atmospheric pressure. Flare Stack - Is a n elevated vertical stack found on oilwells or oil rigs, and in refineries, chemical plants and landfills used for burning off u nusable waste gas or flammab le gas and liquids rele ased by pressure relief valves during unplanned over-pressuring of plant equipment. Flame Arrestors - A crimped ribbon aluminum or stainless steel flame cell to protect against rapid burn backs in low-pressure situations. These passive safety device guaranteed to prevent flame fronts from propagating back through lines, destroying facilities, and causing injuries. Flare Tips - Structure at top of the flare play the role to keep an optimum burn and control over all flow rates, which results in a cleanercombust ion. The design of the tip makes sure that the tip does not come into contacting with the flame ma king the tips reliable and long lasting.They were designed for engineers to do preliminary designs an d process specification s heets. Open Disposal System- A disposal system that discharges directly from relief system to atmosphere without other devices. Overpressure- Pressure value increase more that the set point pressu re of the relieving device, expressed in percent. Pressure Relieving System- An arrangement of a pressure-relieving de vice, piping and a means of dispo sal intended for the safe relief, conveyance, and disposal of fluids in a vapour, liquid, or gaseous phase. It can be consist of only one pressure relief valve or ruptu re disk, either with or without discharge pipe, on a single vessel or line. The valve opens normally in proportion to the pressure incr ease over the opening pressure. A relief valve is used primarily with in compressible fluids. Rupture Disk Dev ice- A non reclosing differential pressure relief device actuat ed by inlet static pressure and designed to function by bursting the pressure containing rupture disk. A rupture disk device includes a rupture disk and a ruptu re disk holder. Three types available self-supported, Guy-wire supported and De rrick supported. Windbreaker - A windbreaker is structure uses to prevent the wind from extin guishing the flames which located at flare tip. It serves also to hid e the flames. They were designed for engineers to do preliminary designs an d process specification s heets. Greek letters ? Emissivity, (d imensionless).ResearchGate has not been able to resolve any references for this publication. March 2020 Karl Kolmetz Faulina Popy The flare provides a means of safe disposal of the vapor streams from its facilities,withKnockout drums are one of thePressure-relief systems inView full-text Article Full-text available WASTE WATER TREATMENT PLANT SELECTION, SIZING AND TROUBLESHOOTING, Kolmetz Handbook Of Process Equip. February 2016 Karl Kolmetz This design guideline covers the basic elements of Waste Water Treatment in sufficientSewage or waste water is a mixture of domestic and industrial wastes. It is more thanRIS BibTeX Plain Text What do you want to download. Citation only Citation and abstract Download Discover the world's research Join ResearchGate to find the people and research you need to help your work. Join for free ResearchGate iOS App Get it from the App Store now. Install Keep up with your stats and more Access scientific knowledge from anywhere or Discover by subject area Recruit researchers Join for free Login Email Tip: Most researchers use their institutional email address as their ResearchGate login Password Forgot password. Keep me logged in Log in or Continue with LinkedIn Continue with Google Welcome back. Keep me logged in Log in or Continue with LinkedIn Continue with Google No account. All rights reserved. Terms Privacy Copyright Imprint. To start viewing messages,Tynt Script Sponsored by Information Technology Salary By Marco Mamdouh Cookies help us deliver our services. By using our services, you agree to our use of cookies. Meeting Electricity Congress Symposium Symposium Experience and Prospects The methods used to calculate flare radiation are reviewed critically. Case studies are cited to illustrate the cost and material benefits which can be achieved if the flare system is considered from the outset as an integral part of the production process equipment. Engineers were often tempted to write the words 'To the Flare' on an arrow pointing off the edge of a process flow sheet and then forget them. Quite often this represented the bulk of the initial design information for the flare system and the detailed design was not considered until near the end of the project. The flare system then had to meet the diverse and often conflicting requirements of a multiplicity of gas sources, making design optimisation difficult if not impossible. Early consideration makes available a greater number of options and leads to the most efficient and cost effective system. The flare is much closer to the operator and previously used design calculation methods involving many implicit assumptions are no longer satisfactory. Under-design will lead to potentially unsafe operation whereas over-design carries enormous cost penalties. This paper presents a guide to the most important factors in designing offshore flare systems and looks critically into one of the most important aspects - accurate prediction of flare radiation. Case studies are presented which highlight the fact that offshore flare design is not a simple matter and that fairly detailed analysis is required to produce the most economic system.The initial content has been derived from: Robert E. Sheriff's Encyclopedic Dictionary of Applied Geophysics, fourth edition. Depending on local environmental constraints, these systems can be used for: 1. Extensive venting during start up or shutdown 2. Venting of excess process plant gas 3. Handling emergency releases from safety valves, blow-down, and depressuring systems Designs will vary considerably, depending on the type of connected equipment and the complexity of the overall system. A flare system generally consists of an elevated stack, means to maintain burning conditions at the top of stack, and means to prevent flashback within the system. Whenever industrial plant equipment items are overpressurized, the pressure relief valves provided as essential safety devices on the equipment automatically release gases and sometimes liquids. Those pressure relief valves are required by industrial design codes and standards, as well as by law. The released gases and liquids are routed through large piping systems called flare headers, to a vertical elevated flare. The released gases are burned as they exit the flare stacks. The size and brightness of the resulting flame depend on the flammable material’s flow rate in terms of joules per hour (or btu per hour). Steam is often injected into the flame to reduce the formation of black smoke. To keep the flare system functional, a small amount of gas is continuously burned, like a pilot light, so that the system is always ready for its primary purpose as an overpressure safety system. Because the flare tip is open to the atmosphere, high gas velocities are expected at this point. Very high tip velocities cause a phenomenon known as blow-off, in which the flame front is lifted and could eventually turn into a blowout. Very low velocities could damage the flare tip owing to high heat intensities and smoking. In this case, ingress of air in the system and creation of a flammable mixture are possible. Therefore, determination of the right flare diameter is important as far as operation of the system is concerned. The location and height of flare stacks should be based on the heat release potential of a flare, the possibility of personnel exposure during flaring, and the exposure of surrounding plant equipment. There are exposure limitations set forth that must be taken into consideration. In effect, this fixes the distance between the flame and the object. If there are limitations regarding the location (distance), the stack height can be calculated; otherwise, an optimum tradeoff between height and distance should be applied. Wind velocity, by tilting the flame, changes the flame distance and heat intensity. Therefore, its effect should be considered in determining the stack height. If the flare is blown out (extinguished), or if there are environmental hazards associated with the flare output, the possibility of a hazardous situation downwind should be analyzed. 1. Diameter Flare stack diameter is generally sized on a velocity basis, although pressure drop should be checked. Depending on the volume ratio of maximum conceivable flare flow to anticipated average flare flow, the probable timing, frequency, and duration of those flows, and the design criteria established for the project to stabilize flare burning, it may be desirable to permit a velocity of up to 0.5 Mach for a peak, short-term, infrequent flow, with 0.2 Mach maintained for the more normal and possibly more frequent conditions.