Gas treatment plants

FoUowiag Monsanto s success, several companies produced membrane systems to treat natural gas streams, particularly the separation of carbon dioxide from methane. The goal is to produce a stream containing less than 2% carbon dioxide to be sent to the national pipeline and a permeate enriched ia carbon dioxide to be flared or reinjected into the ground. CeUulose acetate is the most widely used membrane material for this separation, but because its carbon dioxide—methane selectivity is only 15—20, two-stage systems are often required to achieve a sufficient separation. The membrane process is generally best suited to relatively small streams, but the economics have slowly improved over the years and more than 100 natural gas treatment plants have been installed. 

SOCAR has investigated small-scale gas treatment plants, capable of operation at low pressures, and Azerigaz has conducted studies into acquiring mobile treatment units which could be positioned at the more significant of these supply points. 

During the last three decades, the Norwegian transportation system has been developed from a single pipeline system (Norpipe system) into a complex interconnected network, as shown in Figure 1. New transportation-and treatment capacity has gradually been added and the network comprises today rich and dry gas pipelines, compressor stations, riser platforms and two onshore gas treatment plants. The system is by now the world s most comprehensive integrated offshore gas transportation network. 

In addition to this, another, often overlooked issue is the disposal of solid byproducts of the incineration process. MSW incinerators essentially produce two types of solid by-products. The first is the slag, or bottom ash, which is mostly made of the noncombustible fractions of the waste, plus a small fraction of the combustible fraction. The second is fly ash, the particulate material captured in the particulate removal section of the flue gas treatment plant, which is often mixed with various other chemicals used for flue gas treatment. Bottom ash and fly ash are characterized by very high concentrations of PTE, such as lead, mercury, cadmium, and nickel, which can easily leach into the environment. 

The separator produces a water phase, a hydrocarbon liquid phase (which can be regarded as a synthetic crude oil) and a recycle gas. Part of the synthesis gas is purged to stop the build up of inert materials such as nitrogen. The recycle gas contains light hydrocarbon gases, unconverted synthesis gas and carbon dioxide produced in the process. This is sent to a gas treatment plant for recovery of synthesis gas. This operation may be integrated into the gas clean-up operation of the fresh synthesis gas from the gasifier. 

Melting Gas-fired melting furnaces and flue-gas treatment plant (dry filter)... 

A gas treatment plant often has both absorption and stripping columns as shown in Figure 12-2. In this operation the solvent is continually recycled. The heat exchanger heats the saturated solvent, changing the equilibrium characteristics of the system so that the solvent can be stripped. A very common type of gas treatment plant is used for the removal of CO2 and/or H2S from refinery gas or natural gas. In this case... 

Explain what absorption and stripping do and describe a conplete gas treatment plant... 

D23. A complete gas treatment plant often consists of both an absorber to remove the solute and a stripper to regenerate the solvent. Some of the treated gas is heated and is used in the stripper. 

Ammonia consumption 0.8 t/h at max. sulfur concentration Amount ammonium sulfate 3.2 t/h at max. sulfur eoncentration FTP Flue gas treatment plant... 

H2S released from the stripper is treated in an O2- or air-blown Claus plant that oxidizes H2S to elemental sulfur. The tail gas from the Claus plant, still rich in sulfur compounds, is then treated in a Shell Claus off-gas treatment plant where those elements are catalytically converted to H2S and then recycled back to the absorption column of the AGR unit. 

The exhausted gas and organic acid mixture which leave the bottom of the reactor flow into two high-efficiency liquid-gas separators in series. The exhaust gas then flows to the exhaust gas treatment plant. The organic acid is transferred to the next stage, ageing and stabilisation of alkylbenzene sulphonic acid, or straight to the neutralisation unit for alcohols, alcohol ethoxylates and alpha-olefin feedstocks. 

Lyle, F. F., Jr., 1988, Stress Ckmosion Cracking of Steels in Amine Solutions Used in Natural Gas Treatment Plants, Paper No. 158, Cotrosion/88, NACE, St. Louis, March 21-25. 

SwRL 1989, An Investigation of Amine-Induced Stress Corrosion Cracking of Steels in Natural Gas Treatment Plants, Final Report SwRI Project No. 06-1202, prepared by the Southwest Research Institute, San Antonio, TX. 

Fortunately, a plant with a large number of processing units can be analyzed as smaller clusters of units—for example, a gas treatment plant and a separations plant that interact very little with each other. Then, with even simple steady-state and dynamic process models, it is possible to develop a design using the standard analytical methods we developed in Chapter 18 (RGA,... 

Gas treatment plants and gas refineries are bothered by corrosion problems. Much of these are caused by the breakdown of solvents, e.g. monoethanolamine, at the elevated temperatures of the reboiler regenerator. It is postulated that the breakdown products can chelate with iron and prevent the formation of an insoluble protective film at the high pH of operation, which should preclude corrosion of iron. 

The construction of commercial nuclear power stations has developed since 19S6. Although closely allied to fossil fuel fired power stations major differences occur because of the substitution of a nuclear reactor for a boiler house. This in turn leads to the virtual elimination of all external fuel handling facilities together with the flue gas treatment plant and chimneys. A comparison of the site areas involved is given in Fig. 1. 

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