Hydrogen purification carbon dioxide removal

Hydrogen production from carbonaceous feedstocks requires multiple catalytic reaction steps For the production of high-purity hydrogen, the reforming of fuels is followed by two water-gas shift reaction steps, a final carbon monoxide purification and carbon dioxide removal. Steam reforming, partial oxidation and autothermal reforming of methane are well-developed processes for the production of hydro-... 

The char is recycled to the gasifier and the synthesis gas passes through a scrubber for additional cooling and purification. The clean gas is then sent to a shift converter to adjust the ratio of carbon monoxide to hydrogen. After shift conversion, the gas is improved by (1) hydrogen sulfide removal, (2) carbon dioxide removal, and (3) methanation. 

The water-gas shift (WGS) reaction is the exothermic conversion of carhon monoxide and water to hydrogen and carbon dioxide according to Scheme 16.1 [1, 2], The reaction is of industrial importance for purification when traces of carbon monoxide have to be removed from gaseous feed, such as in the Haber-Bosch process for ammonia production or in modem polymer electrolyte membrane (PEM) fuel cells [3]. 

Kohl, A. L. Riesenfeld, F.C. 1997, Alkanolamines for Hydrogen Sulfide and Carbon Dioxide Removal Gas Purification Houston, TX, 5, 99. 

Carbon Dioxide and Water Removal from Ethylene, 1076 Carbon Dioxide Removal from Cryogenic Plant Feed Gas, 1076 Removal of Sulfur Compounds, 1078 Hydrogen Purification by Pressure Swing Adsorption (PSA), 1081... 

Gas purification PSA with adjustment of the hydrogen to nitrogen ratio. Carbon dioxide removal (optional) in a low pressure MDEA wash on the offgas from PSA unit. Methanation upstream of the synthesis gas compressor. 

Gas purification is by conventional shift conversion followed by a physical carbon dioxide removal (e.g. Selexol) and final purification in a cryogenic unit. The hydrogen to nitrogen ratio of the synthesis gas at the cryogenic unit inlet is 1.0-1.8. 

Purification of hydrogen by high temperature shift conversion and Pressure Swing Absorption. Optional carbon dioxide-removal located upstream of the PSA unit in case carbon dioxide is required. 

This chapter reviews and discusses recent advances in carbon-dioxide-selective polymer membranes for hydrogen purification and carbon dioxide removal. 

Application. The absolute separator was developed for applications where the maximum possible separation of minute liquid particles—varying from mist to submicron in size— from a gas stream is required. The prindpal applications of the absolute separator are for removal of oil mist upstream of dessicant beds in ammonia and urea plants and other chemical and petrochemical plants. Absolute separators are also effective for removal of mist in process streams such as chlorine, nitrogen, hydrogen, oxygen, carbon dioxide, and air purification. 

Gas Reduction. The use of a gaseous reduciag agent is attractive because the metal is produced as a powder that can easily be separated from the solution. Carbon dioxide, sulfur dioxide, and hydrogen can be used to precipitate copper, nickel, and cobalt, but only hydrogen reduction is appHed on an iadustrial scale. In the Sherritt-Gordon process, the excess ammonia is removed duting the purification to achieve a 2 1 ratio of NH iNi ia solution. Nickel powder is then precipitated by... 

Gas purification processes fall into three categories the removal of gaseous impurities, the removal of particulate impurities, and ultrafine cleaning. The extra expense of the last process is only justified by the nature of the subsequent operations or the need to produce a pure gas stream. Because there are many variables in gas treating, several factors must be considered (/) the types and concentrations of contaminants in the gas (2) the degree of contaminant removal desired (J) the selectivity of acid gas removal required (4) the temperature, pressure, volume, and composition of the gas to be processed (5) the carbon dioxide-to-hydrogen sulfide ratio in the gas and (6) the desirabiUty of sulfur recovery on account of process economics or environmental issues. 

The reaction produces additional hydrogen for ammonia synthesis. The shift reactor effluent is cooled and tlie condensed water is separated. The gas is purified by removing carbon dioxide from the synthesis gas by absorption with hot carbonate, Selexol, or methyl ethyl amine (MEA). After purification, the remaining traces of carbon monoxide and carbon dioxide are removed in the methanation reactions. 

HS A family of gas purification processes developed by Union Carbide Corporation, based on the use of proprietary solvents known as UCARSOLs. UCARSOL HS-101, is based on methyl diethanolamine and is used for removing hydrogen sulfide and carbon dioxide from other gases. Ucarsol LH-101 is used in its Cansolv system for flue-gas desulfurization. 

Purification of Crude Hydrogen.—The crude hydrogen is first scrubbed with water, which besides removing mechanically contained impurities also reduces the amount of carbon dioxide, as this gas is soluble in water. 

The bulk of the carbon dioxide is absorbed by means of water, but if the hydrogen is required for aeronautical purposes, the gas is finally passed through either a caustic soda solution or over lime. Traces of carbon monoxide are removed by passing the gas under pressure through ammoniacal cuprous chloride solution. As a result of these final purifications a gas is obtained of approximately the following composition —... 

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