GAS SEPARATION PROCESS

摘要

A continuous gas purification process for selectively removing acid gases such as CO2, H2S, and SO2, other sulfur-containing molecules such as COS, and other relatively high boiling point impurities from a gas mixture stream containing lower boiling point components, such as H2, N2, CO, CH4, C2H4, C2H2, and the like, comprises: Providing the gas mixture to be treated as a dehydrated stream at an initial pressure above atmospheric and at a temperature which is substantially the dew point temperature of carbon dioxide in the gas stream; contacting the gas stream at such pressure and temperature with a liquid carbon dioxide refrigerant-absorbent to absorb such impurities other than CO2, and separating these impurities together with still liquid carbon dioxide absorbent from a first residual gas stream, separating a portion of the carbon dioxide component of said first residual gas stream at such pressure, preferably by condensation while further cooling the pressurized stream by indirect heat exchange, leaving a second residual gas stream; contacting said second residual gas stream at such pressure with a second refrigerant-absorbent maintained below the triple point temperature of carbon dioxide for absorbing additional carbon dioxide and leaving a third residual gas stream; and preferably, performing a final separation of additional carbon dioxide from said third residual gas stream by absorption into a liquid absorbent maintained below said triple point temperature, which liquid absorbent may be a liquid phase of the second refrigerant-absorbent. The second refrigerant-absorbent preferably comprises particulate solid carbon dioxide suspended in an organic liquid vehicle as a slurry in which the solid phase is a mixture of carbon dioxide and organic liquid and melts to provide in situ refrigeration for condensing carbon dioxide from the second residual gas stream. The finally purified gas stream is heat exchanged to recover its refrigeration potential and is discharged at substantially ambient temperature and at substantially said initial pressure. Some of the liquid carbon dioxide refrigerant-absorbent is separated from sulfur-containing impurities absorbed thereby to concentrate the latter for processing in a Claus plant to recover elemental sulfur. The absorbents used in the process are regenerated therein. Additional carbon dioxide is recovered with a purity acceptable for discharge to the atmosphere or recovery as a by-product. In various parts of the process, pressure energy and refrigeration potential are recovered and used to minimize the net energy input to the process.