Process for gasification and production of by-product superheated steam

Claim 1

A process for the partial oxidation of an ash-containing solid carbonaceous fuel for producing a cooled cleaned product gas stream of synthesis gas, fuel gas or reducing gas along with by-product saturated and superheated steam comprising: (1) reacting particles of said solid fuel with a free-oxygen containing gas and with or without a temperature moderator in a down-flow refractory lined gas generator at a temperature in the range of about 1700° to 3100° F. and a pressure in the range of about 10 to 200 atmospheres to produce a raw gas stream comprising H 2 , CO, CO 2 , and one or more materials selected from the group consisting of H 2 O, H 2 S, COS, CH 4 , NH 3 , N 2 , and A, and containing molten slag and/or particulate matter; (2) passing the gas stream from (1) down through the central outlet in the bottom of the reaction zone and into a separate thermally insulated gas diversion chamber provided with a side outlet and a bottom outlet; separating by gravity molten slag and/or particulate matter from said gas stream; passing from about 0 to 20 vol. % of said gas stream as bleed gas along with said separated material through the bottom outlet of said diversion chamber and into a pool of quench water in a quench chamber located below said diversion chamber; and passing the remainder of said gas stream through a side exit passage in said diversion chamber directly through a thermally insulated transfer line and inlet passage of a separate thermally insulated gas-gas quench cooling and solids separation zone at substantially the same temperature and pressure as produced in step (1) less ordinary pressure drop in the lines; (3) impinging the gas stream from (2) in said gas-gas quench cooling and solids separation zone with a stream of recycle quench gas comprising cooled cleaned and compressed product gas from (7), thereby partially cooling the gas stream from (2) partially solidifying entrained molten slag, and separating from the gas stream a portion of the slag and particulate matter; and passing the partially cooled gas stream up through a separate thermally insulated upper chamber located above and communicating with said gas-gas quench cooling and solids separation zone and removing additional entrained solids from the gas stream; (4) cooling the gas stream from (3) in a main gas cooling zone and producing by-product saturated and superheated steam by passing said gas stream in indirect heat exchange with preheated boiler feed water first upward through the tubes in a first upright high temperature shell-and-straight fire tube gas cooler having refractory lined inlet and outlet sections, one pass on the shell and tube sides and having fixed tube sheets, then passing the gas stream in indirect heat exchange with saturated steam down through the tubes in a second upright shell-and-straight fire tube gas cooler having one pass on the tube-side and shell-side and having fixed tube sheets, and then passing the gas stream in indirect heat exchange with preheated boiler feed water up through the tubes in the first tube-side pass of a third gas cooler comprising an upright low temperature shell-and-straight fire tube gas cooler having two passes on the tube-side and one pass on the shell-side and having fixed tube sheets, and then down through the tubes in the second tube-side pass of said third gas cooler; and wherein saturated steam is produced on the shell-sides of said first and third gas coolers, and at least a portion of which is superheated on the shell-side of said second gas cooler to produce by-product superheated steam while the remainder, if any, is removed as by-product saturated steam and preheating boiler feed water for use in (4) by indirect heat exchange with the gas stream leaving said third gas cooler; (5) cooling, and scrubbing the gas stream from (4) with water in gas cooling and scrubbing zones producing a carbon-water dispersion; (6) cooling the gas stream from (5) below the dew point and separating condensed water to produce said cooled, cleaned stream of product gas; and (7) compressing a portion of said product gas stream from (6) and introducing same into said gas-gas quench cooling and solids separation zone in (3) as said stream of recycle quench gas.