Flare

Flares are an attempt to deliberately burn the flammable safety relief and/or process vents from a plant. The height of the stack is important to the safety of the surroundings and personnel, and the diameter is important to provide sufficient flow velocity to allow the vapors/ gases to leave the top of the stack at sufficient velocities to protide good mixing and dilution after ignition at the flare tip by pilot flames. 

The velocities of the discharge of relief devices through a stack usually exceed 500 feet/second. Because this stream exits as a jet into the air, it is sufficient to cause turbulent mixing [33]. 

For a flare stack to function properly and to handle the capacity that may be required, the flows under emergency conditions from each of the potential sources must be carefully evaluated. These include, but may not be limited to, pressure relief valves and rupture disks, process blowdown for startup, shutdown, upset conditions, and plant 

Diameter sizing based on stack velocity [33c], solve for d.  

W = vapor relief rate to stack, lbs/hr Pt = pressure of the vapor just inside flare tips (at top), psia (For atmospheric release, P, = 

Flares are sometimes used after knockout drums. The objective of a flare is to burn the combustible or toxic gas to produce combustion products that are neither toxic nor combustible. The diameter of the flare must be suitable to maintain a stable flame and to prevent a blowout (when vapor velocities are greater than 20% of the sonic velocity). 

The height of a flare is fixed on the basis of the heat generated and the resulting potential damage to equipment and humans. The usual design criterion is that the heat intensity at the base of the stack is not to exceed 1500 Btu/hr/ft2. The effects of thermal radiation are shown in the following table  

Using the fundamentals of radiation, we know that the heat intensity q at a specific point is a function of the heat generated by the flame Q, the emissivity e, and the distance R from the flame  

Determine the stack height required to give a heat intensity of 1500 Btu/hr/ft2 at a distance of 410 ft from the base of the flare. The flare diameter is 4 ft, the flare load is 970,000 lb/hr, and the molecular weight of the vapor is 44. 

10Soen H. Tan, Flare System Design Simplified, Hydrocarbon Processing (January 1967). 

The general principles for the location of flares should be governed by the following 

When immersed in water, the explosives in water-activated contrivances are initiated by electric current as water (acting as an electrolyte) immerses the electrodes of specially designed batteries by chemical reaction with water and by pressure sensors triggered at certain depths. These contrivances include ammunition, signal flares and other pyrotechnics, sounding devices (which are dropped by ships to determine depth), and actuating cartridges for gas cylinders that automatically inflate life rafts and jackets. 

Some cartridge cases are made of combustible materials (e.g., paper, plastic) that leave no residue or spent case to be removed from the device, tool, or weapon. In transportation terms, however, true combustible cases are those made of nitrocellulose which, being an explosive, adds force to the overall power of the explosive charge as well as leaving no residue. 

Ammunition, smoke (water-activated contrivances), white phosphorus, with burster, expelling charge or propelling charge, see Ammunition, p.8 

Ammunition, toxic (water-activated contrivances), see Ammunition, p.8 

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Flares. Flares are used for the combustion of waste hydrocarbon gases in which the rates may vary over a wide range and for emergency releases. Steam injection is usually used to enhance mixing and the formation of a clean flame. 

To prepare gas for evacuation it is necessary to separate the gas and liquid phases and extract or inhibit any components in the gas which are likely to cause pipeline corrosion or blockage. Components which can cause difficulties are water vapour (corrosion, hydrates), heavy hydrocarbons (2-phase flow or wax deposition in pipelines), and contaminants such as carbon dioxide (corrosion) and hydrogen sulphide (corrosion, toxicity). In the case of associated gas, if there is no gas market, gas may have to be flared or re-injected. If significant volumes of associated gas are available it may be worthwhile to extract natural gas liquids (NGLs) before flaring or reinjection. Gas may also have to be treated for gas lifting or for use as a fuel. 

Gas can be injected into reservoirs to supplement recovery by maintaining reservoir pressure or as a means of disposing of gas which cannot be flared under environmental legislation, and for which no market exists. 

Product quality specification Contractual agreements Capacity and availability Concurrent operations Monitoring and control Testing metering Standardisation Flaring and venting Waste disposal Utilities systems... 

Product quality is not limited to oil and gas quality certain effluent streams will also have to meet a legal specification. For example, in disposal of oil in water, the legislation in many offshore areas demands less than 40 ppm (parts per million) of oil in water for disposal into the sea. In the UK, oil production platforms are allowed to flare gas up to a legal limit. 

In some undersaturated reservoirs with non commercial quantities of gas but too much to flare, gas has be used to fuel gas turbines and generate electricity for local use. 

Flow measurements using tracers are performed in all piping systems carrying oil, gas or water including separators, compressors, injector systems, and flares. Calibration of elsewhere difficult accessible flow meters is regularly performed by the tracer methods, which are based on international standards. Tracer flow measurements are also well suited for special purposes... 

Gas flaring in offshore installations and oil refineries represents a source of loss of energy making it important to operators and authorities to monitor the amounts of flared gas. In some countries the flare gas is subject to CO2 tax. Flow metering systems are installed on some but not all flare systems. 

In situ control and calibration of flare and other gas metering systems is performed by gaseous tracers using the transit time method without affecting the normal production. Details about methodology are given in / /. 

The gaseous tracer method yields the equivalent piston flow linear velocity of the gas flow in the pipe without any constraints regarding flow regime under the conditions prevailing for flare gas flow. 

The method is based on the international standard ISO 4053/IV. A small amount of the radioactive tracer is injected instantaneously into the flare gas flow through e.g. a valve, representing the only physical interference with the process. Radiation detectors are mounted outside the pipe and the variation of tracer concentration with time is recorded as the tracer moves with the gas stream and passes by the detectors. A control, supply and data registration unit including PC is used for on site data treatment... 

The main sources of error which define the accuracy are counting statistics in tracer concentration measurements, the dispersion of the tracer cloud in the flare gas stream, and the stationarity of the flow during measurements. 

Amorphous boron is used in pyrotechnic flares to provide a distinctive green color, and in rockets as an igniter. 

Strontium is softer than calcium and decomposes in water more vigorously. It does not absorb nitrogen below 380oC. It should be kept under kerosene to prevent oxidation. Freshly cut strontium has a silvery appearance, but rapidly turns a yellowish color with the formation of the oxide. The finely divided metal ignites spontaneously in air. Volatile strontium salts impart a beautiful crimson color to flames, and these salts are used in pyrotechnics and in the production of flares. Natural strontium is a mixture of four stable isotopes. 

Mldiomycin [67527-71-3] Mid steel Mid steel cast iron Mlezyme Mlitary flare technology Mlitary pyrotechnics Milk... 

Sigma (s-) receptors Signal flares Signaling smokes Signal modulators Signal processing... 

Storage tanks should have temperature monitoring with alarms to detect the onset of reactions. The design should comply with all appHcable industry, federal, and local codes for a class IB flammable Hquid. The storage temperature should be below 37.8°C. Storage should be under an atmosphere of dry nitrogen and should vent vapors from the tank to a scmbber or flare. 

For environmental reasons, burning should be smokeless. Long-chain and unsaturated hydrocarbons crack in the flame producing soot. Steam injection helps to produce clean burning by eliminating carbon through the water gas reaction. The quantity of steam required can be as high as 0.05—0.3 kg steam per kg of gas burned. A multijet flare can also be used in which the gas bums from a number of small nozzles parallel to radiant refractory rods which provide a hot surface catalytic effect to aid combustion. 

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