Process for the recovery of carbon dioxide of very high purity

摘要

Carbon dioxide is recovered from a gas containing CO2 by countercurrently scrubbing the gas with a liquid capable of absorbing carbon dioxide at 5-100 Atm., reducing the pressure of the liquid in a turbine to 20-80% of the scrubber pressure and separating the gas, containing the greater part of non-CO2 gas, in a separator; the liquid is then passed to one or more vessels in which the pressure is reduced to 0.3-3.0 Atm. below the pressure in the separator and each preceding vessel, the gas is separated and the liquid passed to a second turbine at a pressure 0.2-2 Atm. higher than the static pressure of the column of liquid between the second turbine and the gas collector in which pure CO2 is separated from the liquid passing from the second turbine and which is located above this turbine. The scrubbing liquid may be water, an aqueous alkaline solution, or an anhydrous liquid absorbent e.g. an aqueous solution of ammonia or an organic derivative or of an alkali metal salt of a weak acid. Gas containing CO2, CO, H2, N2, A and CH4 at 28 Atm. is mixed with gas from separator 3 containing CO2, CO and H2 which is compressed by 4. The mixed gas containing 29% CO2 is fed to scrubber containing H2O at 28 Atm. and is treated to leave 0.3% CO2. Scrubbing H2O from 1 is passed to turbine 2 at 8.9 Atm. yielding gas to 3. H2O from 3 is passed to vessel 5 at 7 Atm. yielding a gas containing CO2, CO and H2 which is vented to atmosphere. H2O from 5 is fed to turbine 6 at a pressure of the water column from 6 to degasifier 7 where 99.2% pure CO2 is obtained. H2O from > is freed from dissolved gases in 8 by aeration and then returned to 1 via pump 9 driven by motor 10 supplementing turbines 2 and 6.