Configurations and methods of carbon capture
View Patent ↗An IGCC plant has a precombustion decarbonization unit in which acid gas is removed from a combustion gas before the combustion gas enters a combustion turbine. In one preferred configuration, a sulfur removal unit removes hydrogen sulfide from a feed gas before the desulfurized feed gas enters an autorefrigeration unit in which carbon dioxide is removed. In another preferred configuration, hydrogen sulfide is converted to carbonyl sulfide in a dryer, and the carbonyl sulfide is absorbed in the liquid carbon dioxide that is prepared from the feed gas using autorefrigeration.
1. A method of removing hydrogen sulfide from shifted syngas, comprising:
dehydrating and cooling the shifted syngas in an amount sufficient to convert the hydrogen sulfide in the shifted syngas to carbonyl sulfide;
absorbing the carbonyl sulfide from the shifted syngas in an absorber using liquid carbon dioxide to produce a desulfurized syngas and a carbonyl sulfide containing liquid carbon dioxide product;
feeding the desulfurized syngas into an autorefrigeration unit to form the liquid carbon dioxide from the desulfurized syngas and to further produce a desulfurized and decarbonized syngas;
using refrigeration content in the desulfurized and decarbonized syngas and the carbonyl. sulfide containing liquid carbon dioxide product in the step of cooling the shifted syngas; and
feeding the desulfurized and decarbonized syngas into a hydrogen pressure swing absorption (PSA) unit to produce a hydrogen product and a carbon dioxide-containing PSA offgas.
2. The method of claim 1 wherein the step of dehydrating the shifted syngas comprises contacting the shifted syngas with a desiccant that is coated with a carbonyl sulfide hydrolysis catalyst.
3. The method of claim 1 further comprising a step of feeding the carbonyl sulfide containing liquid carbon dioxide into a separator to thereby produce a carbonyl sulfide bottom stream and a carbon dioxide overhead vapor stream.
4. The method of claim 1 further comprising a step of feeding the carbon dioxide containing PSA offgas into a second autorefrigeration unit to produce a second liquid carbon dioxide stream.
5. The method of claim 4 further comprising a step of combining the second liquid carbon dioxide stream from the second autorefrigeration unit with the liquid carbon dioxide of the autorefrigeration unit.