Integrated gasification process
OwnerShang-I Chenginventor
Life of this patent
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Abstract
An integrated process for the gasification of coal alone or with other carbon-containing materials such as solid municipal wastes, biomass and sewage sludges, wherein the endothermic heat required by the gasification reaction is supplied at least in a significant part by the exothermic reaction of CaO in the form of calcined lime or dolomite with carbon dioxide. The CO.sub.2 is recycled to provide a high CO.sub.2 vapor pressure for the exothermic reaction. The calcium carbonate formed in the reaction is decomposed in a combustor to produce the CaO which is recycled to the gasification stage.
Claims7
A method of gasifying water and a carbon-containing substance consisting of coal alone or coal together with municipal waste, sewage sludge or another biomass which comprises the steps of:
- (a) pyrolyzing said carbon-containing substance by contacting it with hot CaO in the form of calcined lime or dolomite, thereby producing a solid phase containing CaO, CaCO.sub.3 and char, and a gaseous phase containing CO.sub.2, H.sub.2 O, CO, H.sub.2 and hydrocarbons;
- (b) reacting water from a source other than step (a) with said char in said solid phase in a steam-carbon reaction energetically promoted by concurrently reacting CO.sub.2 with said CaO to form CaCO.sub.3 and the heat necessary to drive the steam-carbon reaction, thereby producing a combustible-containing solid residue which also includes CaCO.sub.3, and a gas containing CO.sub.2, CO, H.sub.2 and hydrocarbons;
- (c) removing CO.sub.2 which remains unreacted with CaO from the gas produced in step (b) and recycling at least a portion of the removed CO.sub.2 back to step (b);
- (d) combusting the residue produced in step (b) and transforming the CaCO.sub.3 thereof to CaO and carbon dioxide, the steam-carbon reaction of step (b) being controlled so that residual char in said solid residue will upon combustion in step (d) produce sufficient heat to completely decompose the CaCO.sub.3 ;
- (e) recycling the CaO from step (d) to step (a);
- (f) recovering at least a major portion of the gas from step (c) after removal of CO.sub.2 to form a product gas;
- and
- (g) recovering CO.sub.2 from flue gas obtained from step (d) and sending part of it back to step (b).
A method of gasifying water and a plurality of carbon-containing substances including coal, and municipal waste or sewage sludge or another biomass and wherein n carbon-containing substances are used, said method comprising the steps of:
- (a) pyrolyzing said carbon-containing substances by contacting them with hot CaO in the form of calcined lime or dolomite, thereby producing a solid phase containing CaO, CaCO.sub.3 and char, and a gaseous phase containing CO.sub.2, H.sub.2 O, CO, H.sub.2 and hydrocarbons;
- (b) reacting water from a source other than step (a) with said char in said solid phase in a steam-carbon reaction energetically promoted by concurrently reacting CO.sub.2 with said CaO to form CaCO.sub.3 and the heat necessary to drive the steam-carbon reaction, thereby producing a combustion-containing solid residue which also includes CaCO.sub.3, and a gas containing CO.sub.2, CO, H.sub.2 and hydrocarbons;
- (c) removing CO.sub.2 which remains unreacted with CaO from the gas produced in step (b) and recycling at least a portion of the removed CO.sub.2 back to step (b);
- (d) combusting residue produced in step (b) and transforming the CaCO.sub.3 thereof to CaO and carbon dioxide, the steam-carbon reaction of step (b) being controlled so that residual char in said solid residue will upon combustion in step (d) produce sufficient heat to completely decompose the CaCO.sub.3 ;
- (e) maintaining the balance of the components fed to step (a) such that it is defined by the relationship:
- ##EQU2## where x.sub.i =mole fraction of fixed carbon content for the i.sup.th component,
- y.sub.i =mole fraction of water content for the i.sup.th feed component,
- .DELTA.Hc=heat of combustion of carbon in BTU/lb mole or Kcal/g mole,
- .DELTA.Hl=heat of steam-carbon reaction in BTU/lb mole or Kcal/g mole, and
- i=stands for an individual feed component, including coal municipal solid waste, sewage sludge, and other biomass;
- (f) recycling the CaO from step (d) to step (a);
- (g) recovering at least a major portion of the gas from step (c) after removal of CO.sub.2 to form a product gas, and
- (h) recovering CO.sub.2 from flue gas obtained from step (d) and sending part of it back to step (b).
Dependencies are inferred from the claim text.