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US 4,303,415 AGranted
Gasification of coal
AssigneeLubille Energy Development Co., Ltd.
InventorWilliam A. Summers
Life of this patent
Estimating the term…
Abstract
Coal is gasified, to yield a fuel gas having a medium-B.T.U. heating value, in the presence of air and steam in a plurality of reaction stages having different reaction temperatures. Reaction heat is principally supplied directly by recycle of char particles from a separate combustion zone to higher-temperature reaction zones and indirectly by combustion flue gas to lower-temperature reaction zones. Hydrogen sulfide, from product fuel gas, and flue gas are directly contacted to provide elemental sulfur. The only other product is a substantially non-combustible ash.
Claims22
The process of gasifying clean coal particles at a low superatmospheric pressure, wherein the coal particles are converted to a gaseous fuel product and a substantially non-combustible ash in a series of elevated-temperature stages, comprising the steps of:
- (a) drying the coal particles, in a drying stage at a temperature within the range from about 220.degree. to about 300.degree. F., in indirect heat exchange with a flue gas stream;
- (b) transferring the dried coal particles to a heat treating stage and heat treating the dried coal particles therein at a temperature within the range from about 400.degree. to about 700.degree. F., in indirect heat exchange with a flue gas stream;
- (c) transferring the heat-treated coal particles to a devolatilizing stage and devolatilizing the heat-treated coal particles therein at a temperature within the range from about 850.degree. to about 1150.degree. F., in indirect heat exchange with a flue gas stream, to yield an overhead volatiles stream and devolatilized coal char particles;
- (d) transferring the devolatilized coal char particles, to a calcining stage and calcining the devolatilized coal char particles therein at a bed temperature within the range from about 1550.degree. to about 1750.degree. F., in contact with steam and a gaseous stream comprising an oxygen-containing gas, to yield an overhead calciner effluent gas stream and carbon-rich calcined coke particles;
- (e) transferring the calcined coke particles to a gasifying stage and gasifying the calcined coke particles at a bed temperature of at least about 1650.degree. F., in contact with steam, to yield an overhead gasifier gas stream and carbon-lean coke particles;
- (f) transferring the overhead volatiles stream and the overhead gasifier gas stream to an upper zone of the calcining stage, whereby the respective streams and the calciner gas react further in contact with steam and the oxygen-containing gas and are mixed to form the calciner effluent gas stream;
- (g) cooling, and optionally scrubbing, the calciner effluent gas stream to provide a normally liquid condensate fraction and a gaseous fuel product stream;
- (h) transferring the normally liquid condensate fraction to the gasifying stage;
- (i) transferring the carbon-lean coke particles to a heat generating stage and generating heat therein by combustion of a portion of the coke in contact with a gaseous stream comprising air, to provide heated coke particles and the flue gas stream;
- (j) transferring a major portion of the heated coke particles to the gasifying stage, whereby requisite heat is supplied for the gasification of calcined coke particles and heated coke particles;
- (k) withdrawing a minor portion of the heated coke particles to an agglomeration stage, wherein substantially complete conversion of residual coke to ash and a gas is effected;
- and
- (l) discharging from the agglomeration stage a substantially non-combustible ash.
10 more elements
The process of gasifying sulfur-containing clean coal particles at a low superatmospheric pressure, wherein the coal particles are converted to an environmentally suitable gaseous fuel product and a substantially non-combustible ash in a series of stages, comprising the steps of:
- (a) heat treating dried coal particles at a temperature within the range from about 400.degree. to about 700.degree. F.;
- (b) devolatilizing the heat-treated coal particles at a temperature within the range from about 850.degree. to about 1150.degree. F., to yield an overhead volatiles stream and devolatilized coal char particles;
- (c) calcining the devolatilized coal char particles in an expanded bed at a bed temperature within the range from about 1550.degree. to about 1750.degree. F., in contact with steam and a gaseous stream comprising an oxygen-containing gas, to yield an overhead calciner effluent gas stream and carbon-rich calcined coke particles;
- (d) gasifying the calcined coke particles in an expanded bed at a bed temperature within the range from about 1650.degree. F. to about 1950.degree. F., in contact with steam, to yield an overhead gasifier gas stream and carbon-lean coke particles;
- (e) transferring the overhead volatiles stream and the overhead gasifier gas stream to an upper zone of the calcining stage, whereby the respective streams and the calciner gas react further in contact with steam and the oxygen-containing gas and are mixed to form the calciner effluent gas stream;
- (f) cooling and scrubbing the calciner effluent gas stream to provide a normally liquid condensate fraction and a gaseous fuel product stream containing hydrogen sulfide;
- (g) transferring the normally liquid condensate fraction to the gasifying stage;
- (h) transferring the carbon-lean coke particles to a heat generating stage and generating heat therein by combustion of a portion of the coke in contact with a gaseous stream comprising air, to provide heated coke particles and a flue gas stream containing sulfur dioxide;
- (i) transferring a major portion of the heated coke particles to the gasifying stage, whereby requisite heat is supplied for the gasification of calcined coke particles and heated coke particles;
- (j) withdrawing a minor portion of the heated coke particles to an agglomeration stage, wherein substantially complete gasification of residual coke is effected by reaction with air and steam at a temperature of at least about 1900.degree. F., to provide a producer gas stream containing hydrogen sulfide;
- (k) discharging from the agglomeration stage a substantially non-combustible ash;
- (l) extracting and recovering the hydrogen sulfide from the gaseous fuel product stream, to provide an environmentally suitable low-sulfur gaseous fuel product;
- (m) catalytically contacting the recovered hydrogen sulfide with the flue gas stream, containing sulfur dioxide, whereby elemental sulfur is produced and recovered;
- and
- (n) discharging an environmentally suitable low-sulfur flue gas effluent.
12 more elements
Dependencies are inferred from the claim text.