Improved coal gasification

Abstract

A two-zone gasifier is used to produce syngas from coal fines, oxygen and steam. The two-zone gasifier has a top fluidized gasification zone and a bottom entrained flow gasification zone connected by a Venturi throat. The syngas production will occur in both zones with the syngas being collected from the top of the gasifier.

Having thus described the invention, what we claim is: 
     
         1 . A gasifier for producing syngas comprising an upper fluidized gasification zone in fluid communication through a Venturi throat with a lower entrained flow gasification zone. 
     
     
         2 . The gasifier as claimed in  claim 1  wherein said upper fluidized gasification zone has refractory lining walls. 
     
     
         3 . The gasifier as claimed in  claim 1  wherein said entrained flow gasification zone has water membrane walls. 
     
     
         4 . The gasifier as clairned in  claim 1  wherein said upper fluidized gasification zone has inputs to provide for injecting materials selected from the group consisting of coal, fines, gas and steam. 
     
     
         5 . The gasifier as claimed in  claim 1  wherein said entrained flow gasification zone has inputs to provide for injecting materials selected from the group consisting of coal, fines, gas and steam. 
     
     
         6 . The gasifier as claimed in  claim 1  wherein said Venturi throat has a diameter small than said upper fluidized gasification zone and said entrained flow gasification zone. 
     
     
         7 . The gasifier as claimed in  claim 1  wherein said entrained flow gasification zone has an opening at its bottom. 
     
     
         8 . A method for producing syngas comprising the steps:
 a) Feeding coal fines oxygen and steam simultaneously to fluidize gasification zone and entrained flow gasification zone;   b) Reacting said coal fines in the presence of oxygen and steam to form syngas;   c) Feeding syngas from said entrained gasification zone to said fluidized gasification zone; and   d) Recovering syngas from said fluidized gasification zone.   
     
     
         9 . The method as claimed in  claim 8  wherein said fluidized gasification zone is at a temperature of about 1000° C. 
     
     
         10 . The method as claimed in  claim 8  wherein the coal fines fed to said fluidized gasification zone are greater than 75 micron in size. 
     
     
         11 . The method as claimed in  claim 8  wherein said fluidized gasification zone is connected to said entrained flow gasification zone by a Venturi throat. 
     
     
         12 . The method as claimed in  claim 11  wherein said Venturi throat is smaller in diameter than said fluidized gasification zone and said entrained flow gasification zone. 
     
     
         13 . The method as claimed in  claim 8  wherein said entrained flow gasification zone is at a temperature of about 1500° C., or above the coal ash fluid temperature. 
     
     
         14 . The method as claimed in  claim 8  wherein the coal fines fed to said entrained flow gasification zone are less than  75  micron in size. 
     
     
         15 . The method as clamed in  claim 8  wherein liquid slag is fed to a quench from said entrained flow gasification zone. 
     
     
         16 . The method as claimed in  claim 8  wherein said syngas is fed to a first stage cyclone. 
     
     
         17 . The method as claimed in  claim 15  wherein said syngas is at a temperature of about 900 to 1000° C. 
     
     
         18 . The method as claimed in  claim 8  wherein coal fines that are recycled from the first stage cyclone are fed to said fluidized gasification zone. 
     
     
         19 . The method as claimed in  claim 8  wherein coal fines that are recycled from a second stage cyclone are fed to said entrained flow gasification zone. 
     
     
         20 . The method as claimed in  claim 8  wherein steam is injected into said entrained flow gasification zone to drive the produced syngas into said fluidized gasification zone.