Drying and gasification process

Abstract

A process for producing syngas from a carbonaceous substance and/or treating a carbonaceous substance, the process including the following steps: a) reducing the surface moisture of the carbonaceous substance; b) reducing the inherent moisture of the carbonaceous substance; and, c) gasifying the carbonaceous substance to produce syngas, wherein at step a) the carbonaceous substance is directly contacted with a hot gas at a temperature of between 50° C. to 250° C., and/or the carbonaceous substance is indirectly contacted with saturated steam at a temperature of between 105° C. and 250° C.

1 . A process for producing syngas from a carbonaceous substance and/or treating a carbonaceous substance, the process including the following steps:
 a) reducing the surface moisture of the carbonaceous substance;   b) reducing the inherent moisture of the carbonaceous substance; and,   c) gasifying the carbonaceous substance to produce syngas,   wherein at step a) the carbonaceous substance is directly contacted with a hot gas at a temperature of between 50° C. to 250° C., and/or the carbonaceous substance is indirectly contacted with saturated steam at a temperature of between 105° C. and 250° C., and wherein the temperature of the carbonaceous substance after step b) and before step c) is between 80° C. and 220° C.   
     
     
         2 . A process according to  claim 1  wherein at step a) the hot gas is a waste gas from a combustion process, or, the hot gas is indirectly heated by waste heat before contacting the carbonaceous substance. 
     
     
         3 . A process according to  claim 1  wherein at step a) the carbonaceous substance is at least partially fluidised when contacted with the hot gas. 
     
     
         4 . A process according to  claim 1  wherein the temperature of the carbonaceous substance is between 25° C. and 100° C. after step a) and before step b) and some, or most of the surface moisture of the carbonaceous substance is removed. 
     
     
         5 . A process according to any  claim 1  wherein at step b) the carbonaceous substance is directly contacted with a hot gas at a temperature of 100° C. and 300° C., and/or the carbonaceous substance is indirectly contacted with saturated steam at a temperature of between 150° C. and 250° C. 
     
     
         6 . A process according to  claim 5  wherein at step b) the hot gas is a waste gas from a combustion process, or, the hot gas is indirectly heated by waste heat before contacting the carbonaceous substance. 
     
     
         7 . A process according to  claim 6  wherein at step b) the hot gas has a reduced oxygen content from that of air wherein the oxygen content in the hot gas is from between 2% to 15% volume. 
     
     
         8 . A process according to  claim 5  wherein at step b) the carbonaceous substance is at least partially fluidised when contacted with the hot gas. 
     
     
         9 . A process according to  claim 5  wherein the temperature of the carbonaceous substance is between 80° C. and 150° C. and the moisture content of the carbonaceous substance is from 2% to 20% wt after step b) and before step c). 
     
     
         10 . A process according to  claim 5  wherein an outlet gas from step a) and/or step b), produced after the hot gas directly contacts the carbonaceous substance, is directed to a water recovery process step to recover the moisture removed from the carbonaceous substance. 
     
     
         11 . A process according to  claim 5  wherein an outlet gas from step a) and/or step b), produced after the hot gas directly contacts the carbonaceous substance, is treated to remove potentially hazardous gaseous compounds yielded from the carbonaceous substance, such as for example ammonia and hydrogen cyanide. 
     
     
         12 . A process according to  claim 1  wherein process steps a) and b) are performed in the same vessel such as for example a partially fluidised bed reactor. 
     
     
         13 . A process according to  claim 1  wherein at process step c) the carbonaceous material is contacted with hot gas at a temperature of between 500° C. and 1000° C. yielding a gas stream of syngas and solid char. 
     
     
         14 . A process according to  claim 13  wherein at process step c) the carbonaceous material is at least partially heated by low temperate oxidation of the carbonaceous material. 
     
     
         15 . A process according to  claim 14  wherein oxygen is added to the hot gas before being contacted with the carbonaceous material at step c) to control the degree of low temperature oxidation of the carbonaceous material. 
     
     
         16 . A process according to  claim 1  wherein at process step c) the carbonaceous material is contacted with hot gas at a temperature of between 200° C. and 500° C. yielding a gas stream of low CV syngas and a carbonaceous substance that is at least partially pyrolised. 
     
     
         17 . A process according to  claim 16  wherein at process step c) the carbonaceous material is at least partially heated by low temperature oxidation of the carbonaceous material. 
     
     
         18 . A process according to  claim 17  wherein oxygen is added to the hot gas before being contacted with the carbonaceous material at step c) to control the degree of low temperature oxidation of the carbonaceous material. 
     
     
         19 . A process according to  claim 1  wherein the syngas produced by the process is combusted to form the hot gas, and/or the waste heat utilised in step a), step b) and/or step c). 
     
     
         20 . A process according to  claim 16  wherein the partially pyrolised carbonaceous substance is used as a feed stock for a combustion process. 
     
     
         21 . A process according to  claim 16  wherein the partially pyrolised carbonaceous substance is gasified in a further step to produce a higher CV syngas which may be used in a gas engine or gas turbine. 
     
     
         22 . A process according to  claim 21  wherein the high CV syngas is cooled to a temperature of between 3° C. and 25° C. and excess water separated from the gas stream. 
     
     
         23 . A process according to  claim 22  wherein the excess water separated from the gas stream is recycled and injected into the gasification steps c) and/or the further gasification step. 
     
     
         24 . A process according to  claim 1  wherein the carbonaceous material is chosen from a material, or a mixture of materials, that has a relatively high moisture content and/or low cross over temperature. 
     
     
         25 . A process according to  claim 1  wherein the carbonaceous material is a low rank coal including brown and/or sub-bituminous coal, biomass including wood and bagasse, tar sands, municipal solid waste, agricultural or farming waste, animal waste, human waste or a mixture thereof. 
     
     
         26 . A process according to  claim 1  wherein the carbonaceous substance is substantially granular. 
     
     
         27 . A process according to  claim 20  wherein the partially pyrolised carbonaceous substance is used as a feed stock for a boiler for power generation.