Natural gas dehydration plant

Figure 14.8 Membrane process flow schematics of a natural gas dehydration plant of PRISM...

Figure 11-6. Large glycol natural gas dehydration plant. Courtesy of Southern Counties Gas Co. of California...

Figure 12-2. A typical natural gas dehydration plant employing dry desiccant in vertical...

The COS formation reaction can cause two problems in natural gas dehydration plants (1) the formation of H2O by the reaction affects the degree of dehydration attainable, and (2) the release of COS affects the product gas purity. When liquefied hydrocarbons are recovered from the dehydrated natural gas, the COS concentrates in the propane fraction requiring the installation of a propane treater. 

Figure 12-21. Process flow diagram of typical natural gas dehydration plant using an alumina or silica desiccant and wet gas regeneration.

Figure 12-22. Process flow diagram of typical natural gas dehydration plant using molecular sieve desiccant and dry gas regeneration. From GPSA Engineering Data Book (1987). Reproduced witii permission, copyright 1987, Gas Processors Supplier s Association...

A large use of molecular sieves ia the natural gas industry is LPG sweetening, in which H2S and other sulfur compounds are removed. Sweetening and dehydration are combined in one unit and the problem associated with the disposal of caustic wastes from Hquid treating systems is eliminated. The regeneration medium is typically natural gas. Commercial plants are processing from as Htde as ca 30 m /d (200 bbl/d) to over 8000 m /d (50,000 bbl/d). 

In Qadirpur, Pakistan, the world s largest membrane-based natural gas processing plant is situated (see picture in Figure 4.25). The plant is processing 265 MMSCFD natural gas at 59 bar, and with plans for expanding the plant to handle 400 MMSCFD [129]. The CO2 content is reduced from 6.5 mol% to less than 2 mol% using a CA membrane. The plant is also designed for gas dehydration with membranes. 

Standalone production sites Intermediate-sized natural gas processing plants that are similarly responsible for a variety of processes involved in removing liquids, impurities, and inert gases from natural gas, including fractionation, sweetening, treatment, dehydration, and compression. 

Commercial applications of the Selexol solvent for simultaneous hydrocarbon dew-point control and natural gas dehydration are de.scribed by Epps (1994). A plant design used in several European installations pretreats natural gas before it enters a molecular sieve unit. The design is intended to meet a treated gas specification of a maximum of 0.50 mole% CO2 and a maximum of 6.5 mole% ethane and heavier components. A plant is de.signed to treat 26 MMsefd of gas at 32"F and 603 psia. Operating data for this plant, given in Table 14-12, show that it meets the CO2 and ethane-plus removal specifications. The plant also reduces the water content of the gas from 75 ppmv to 12 ppmv, decreasing the load on the molecular sieve unit, and removes a major fraction of the sulfur components. 

Aker Solutions Chevron Texaco gas plant in Texas Natural gas dehydration Liqui-Cel membrane — ... 

Fig. 6. Adsorption capacity of various dessicants vs years of service in dehydrating high pressure natural gas (39). a, Alumin a H-151, gas 27° C and 123 kPa, from oil and water separators b, siUca gel, gas 38° C and 145 kPa, from oil absorption plant c, sorbead, 136-kPa gas from absorption plant ...

The raw material at this plant is natural gas supplied by the El Paso Natural Gas Company from a nearby pumping station. In each process train, gas is compressed to 850 psig, dehydrated by an adsorption method to remove 100% of the water, then passed through a refrigeration unit to lower the temperature to -60°F. A separator removes liquids upstream of the turboexpander. 

The extraction process at BP-Amoco Empress begins with natural gas arriving at the plant at about 15°C and 600 psi pressure. The gas is dehydrated to a -90°C dewpoint by means of molecular sieves. Still at 600 psi, the gas is introduced into heat exchangers and cooled to -70°C, at which point it begins to liquify in a separator. 

Uses Solvent for nitrocellulose, ethyl cellulose, polyvinyl butyral, rosin, shellac, manila resin, dyes fuel for utility plants home heating oil extender preparation of methyl esters, formaldehyde, methacrylates, methylamines, dimethyl terephthalate, polyformaldehydes methyl halides, ethylene glycol in gasoline and diesel oil antifreezes octane booster in gasoline source of hydrocarbon for fuel cells extractant for animal and vegetable oils denaturant for ethanol in formaldehyde solutions to inhibit polymerization softening agent for certain plastics dehydrator for natural gas intermediate in production of methyl terLbutyl ether. 

The membrane contactor for CO2 removal deserves special attention. It can be used for natural gas treatment, dehydration, and removal of CO2 from flue gas (see Section 4.4.4). A contactor (see Figure 4.22) patented and developed for this purpose by Aker Kvaerner— pUots have been installed and tested both in Norway (at Karstp) and at a gas terminal in Scotland. This module is based on PTFE membranes. A different commercial contactor based on polyimide membranes was recently installed at Santos Gas Plant in Queensland, Australia (December 2003). Santos is the largest gas producer in Australia. 

The need to obtain greater recoveries of the C2, C3, and C/s in natural gas has resulted in the expanded use of low-temperature processing of these streams. The majority of the natural gas processing at low temperatures to recover light hydrocarbons is now accomplished using the turboexpander cycle. Feed gas is normally available from 1 to 10 MPa. The gas is first dehydrated to a dew point of 200 K and lower. After dehydration the feed is cooled with cold residue gas. Liquid produced at this point is separated before entering the expander and sent to the condensate stabilizer. The gas from the separator is expanded in a turboexpander where the exit stream can contain as much as 20 wt % liquid. This two-phase mixture is sent to the top section of the stabilizer which separates the two phases. The liquid is used as reflux in this unit while the cold gas exchanges heat with the fresh feed and is recompressed by the expander-driven compressor. Many variations to this cycle are possible and have been used in actual plants. 

Use Manufacture of formaldehyde, acetic acid, and dimethyl terephthalate chemical synthesis (methyl amines, methyl chloride, methyl methacrylate) antifreeze solvent for nitrocellulose, ethylcellulose, polyvinyl butyral, shellac, rosin, manila resin, dyes denaturant for ethanol dehydrator for natural gas fuel for utility plants (methyl fuel) feedstock for manufacture of synthetic proteins by continuous fermentation source of hydrogen for fuel cells home-heating-oil extender. 

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