Tennessee Valley Authority

Michael C Crim

Timmons S McClanahan

A relatively simple and energy efficient multiple stage cryogenic process for the purification of a hydrogen-rich stream by the removal of acid gases, mainly COand HS, by method of autorefrigeration and delivering or producing those acid gases, mainly CO, at pressure sufficiently high for disposal by containment, commonly known as sequestration. Autorefrigeration is comprised of (a) condensing acid gases from the syngas stream by cooling the syngas, (b) separating the liquefied acid gases from the syngas, and (c) evaporating the liquefied acid gases at a pressure lower than that of the syngas to provide cooling. The process is composed of multiple autorefrigeration stages to generate multiple acid gas product streams with a pressure as high as practical in each stream so as to lessen the power needed to pressurize the acid gas streams for sequestration. The final autorefrigeration stage utilizes an antifreeze liquid that allows the final stage to operate below the freezing point of CO; thus allowing more acid gas removal. The antifreeze liquid is an alcohol or a mixture of alcohols with a freezing point lower than about minus 110 degrees F. and a boiling point higher than about 100 degrees F. The process includes hydrogen recovery and recycle as well as recovery of the energy contained in the sulfur bearing compounds. The process is especially well suited for COremoval/sequestration from a coal (or petroleum coke) gasification process.

Multi-stage cryogenic acid gas removal

A simple, compact, and relatively efficient thermodynamic power cycle system and process for extracting heat from a heat source stream and converting a portion of the heat to mechanical power. The system and process are composed of the same series of four processing units or steps found in the most basic form of a Rankine power cycle: (1) heating (means) of a pressurized working fluid to produce a superheated gas, (2) expansion (means) to a lower pressure to produce power, (3) condensation (means) of the low pressure gas to a liquid, and (4) pumping (means) of the liquid to high pressure to complete the cycle. The working fluid is heated under pressures above critical. The working fluid must have a critical temperature more than 40&deg; F. lower than the temperature of the heat source stream and a normal boiling point less than 32&deg; F.

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Florence, AL, United States of America

Michael C Crim