Patent attributes
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 CO2 and H2S, by method of autorefrigeration and delivering or producing those acid gases, mainly CO2, 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 CO2; 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 CO2 removal/sequestration from a coal (or petroleum coke) gasification process.
