Inerts venting

Inerts. Accumulation of inerts can drastically reduce heat transfer, particularly in steam reboilers. Accumulation of acidic or oxidizing inerts such as CO2 is also known to have caused severe corrosion (234, 253, 254). Numerous troublesome case histories of inert accumulation in the heating side of reboilers have been reported (28, 96, 232, 239). Inert venting facilities must be adequate. The following guidelines have recommended for venting inerts (28, 377, 381) ... 

Inerts. Accumulation of even a small fraction of noncondensables can impair condensation heat transfer. The mechanism by which noncondensables accumulation reduces heat transfer is described in Sec. 15.10. Inerts problems are most common in shell-side condensation, where gases can segregate in pockets, and are difficult to remove unless sufficient pressure drop is used to force them to the vent outlet (291, 381). Cross-flow condensers are particularly prone to inerts accumulation. Numerous cases where inerts venting was a problem have been reported (28,134, 239, 381). Adequate venting facilities are needed at all locations where noncondensables are likely to accumulate. Guidelines for venting are presented in Sec. 15.9. 

Inerting venting At the roof or side doors (weight/area < 40 kg/m ) Top and bottom section of the vertical tube On die roof for continuous duty d side vent fw batch Inlet and discharge hoods (vent area = dryer cross-section)... 

Vapor Treatment. The vapors from the tank space can be sent to a treatment system (condenser, absorption, etc.) before venting. The system shown in Fig. 9.1 uses a vacuum-pressure relief valve which allows air in from the atmosphere when the liquid level falls (Fig. 9.1a) but forces the vapor through a treatment system when the tank is filled (Fig. 9.16). If inert gas blanketing is required, because of the flammable nature of the material, then a similar system can be adopted which draws inert gas rather than air when the liquid level falls. 

This eliminates the vapor space but sealing the edge can be a problem. Double seals can help and sometimes a fixed roof is also added above the floating roof to help capture any leaks from the seal. However in this case, the space between the fixed and floating roof now breathes and an inert gas purge of this space would typically be used. The inert gas would be vented to atmosphere after treatment. 

Sampling ndAnalysis Guidelines. As a general safety consideration, ah gases should be vented to an external area and whenever possible, inert gases should be used as the test gas for piping systems. 

This carbon dioxide-free solution is usually treated in an external, weU-agitated liming tank called a "prelimer." Then the ammonium chloride reacts with milk of lime and the resultant ammonia gas is vented back to the distiller. Hot calcium chloride solution, containing residual ammonia in the form of ammonium hydroxide, flows back to a lower section of the distiller. Low pressure steam sweeps practically all of the ammonia out of the limed solution. The final solution, known as "distiller waste," contains calcium chloride, unreacted sodium chloride, and excess lime. It is diluted by the condensed steam and the water in which the lime was conveyed to the reaction. Distiller waste also contains inert soHds brought in with the lime. In some plants, calcium chloride [10045-52-4], CaCl, is recovered from part of this solution. Close control of the distillation process is requited in order to thoroughly strip carbon dioxide, avoid waste of lime, and achieve nearly complete ammonia recovery. The hot (56°C) mixture of wet ammonia and carbon dioxide leaving the top of the distiller is cooled to remove water vapor before being sent back to the ammonia absorber. 

Disposal. Moderate amounts of chlorine ttifluoride or other halogen fluorides may be destroyed by burning with a fuel such as natural gas, hydrogen, or propane. The resulting fumes may be vented to water or caustic scmbbers. Alternatively, they can be diluted with an inert gas and scmbbed in a caustic solution. Further information on disposal of halogen fluorides is available (115—118). 

Storage of Flammable Materials. The preferred storage for flammable Hquids or gases is in properly designed tanks. Floating roof tanks frequently are used in the petroleum industry for flammable cmdes and products (see Tanks and pressure vessels). The vents on cone roof tanks should either be equipped with flame arrestors or the vapor space above the contents should be inerted with a nonflammable gas or vapor, unless the flash point is weU above the maximum ambient temperature, the contents are not heated above the flash point, and the tank is not exposed to other tanks containing flammable Hquids. 

Waste facihties should be designed to prevent explosions in sewer systems and typically are comprised of suitable traps, vents, clean-outs, collecting chambers, etc. Flammable gas detectors are installed in sewers to warn of ha2ardous concentrations, and inert gas blanketing of closed process sumps generally is advisable. 

Fusion Process. In the fusion process, also frequendy referred to as fusion cook, inert gas is continuously sparged from the bottom of the reactor to carry away water vapor from the reaction mixture. The exhaust is then either vented away or sent to a fume scmbber, which is frequendy a small vessel with water atomi2ing no22les. After the reaction is completed, the finished resin may be discharged, filtered, and packaged without solvent. More frequendy, it is cooled to a safe temperature, then dissolved in the desired type and amount of solvent in a thinning tank, filtered, and packaged, or pumped... 

The ethylene feedstock used in most plants is of high purity and contains 200—2000 ppm of ethane as the only significant impurity. Ethane is inert in the reactor and is rejected from the plant in the vent gas for use as fuel. Dilute gas streams, such as treated fluid-catalytic cracking (FCC) off-gas from refineries with ethylene concentrations as low as 10%, have also been used as the ethylene feedstock. The refinery FCC off-gas, which is otherwise used as fuel, can be an attractive source of ethylene even with the added costs of the treatments needed to remove undesirable impurities such as acetylene and higher olefins. Its use for ethylbenzene production, however, is limited by the quantity available. Only large refineries are capable of deUvering sufficient FCC off-gas to support an ethylbenzene—styrene plant of an economical scale. 

Inerts present in chlorine feed are emitted in this vent stream. 

Container. The battery container is made up of a cover, vent caps, lead bushings, and case. Cost and appHcation are the two primary factors used to select the materials of constmction for container components. The container must be fabricated from materials that can withstand the abusive environment the battery is subjected to in its appHcation. It must also be inert to the corrosive environment of the electrolyte and soHd active materials, and weather, vibration, shock, and thermal gradients while maintaining its Hquid seal. 

Storage. Purified and dry aHyl chloride can be safely stored in carbon steel vessels. Use of lined vessels is recommended if slight discoloration or trace presence of metals is undesirable for its intended use. In any event, the presence of air should be avoided for safety (flammabHity) reasons through the use of an inert gas pad. Tank vents should be treated, eg, by incineration, prior to venting to the atmosphere. Some commercial producers intentionaHy add about 0.1% propylene oxide as a stabilizer to prevent discoloration however, this is usuaHy unnecessary if product purity is sufficiently high. 

The ethylene oxide recovered in the desorber contains some carbon dioxide, nitrogen, aldehydes, and traces of ethylene and ethane. In the stripper the light gases are separated overhead and vented, and the partially purified ethylene oxide is sent from the bottom of the stripper to the mid-section of a final refining column. The ethylene oxide from the refining section should have a purity of >99.5 mol %. The final product is usually stored as a Hquid under an inert atmosphere. 

Detonation arresters are typically used in conjunction with other measures to decrease the risk of flame propagation. For example, in vapor control systems, the vapor is often enriched, diluted, or inerted, with appropriate instrumentation and control (see Effluent Disposal Systems, 1993). In cases where ignition sources are present or pre-dic table (such as most vapor destruct systems), the detonation arrester is used as a last-resort method anticipating possible failure of vapor composition control. Where vent collec tion systems have several vapor/oxidant sources, stream compositions can be highly variable and... 

Explosion prevention by inerting has several advantages over explosion protection techniques, such as explosion venting. For example, with successful inerting, fires or business interruptions cannot occur. Nevertheless, beware of the potential of asphyxiation with inerting proper vessel entry procedures must be implemented and occasionally it may be prudent to monitor for oxygen in workplaces. 

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