Method and apparatus for particle recycling in multiphase chemical reactors

Abstract

Method and apparatus for recycling fine ash particles for a multiphase chemical reactor (MCR), wherein coal is partially oxidized in the MCR to produce an exit gas stream in which fine ash particles are entrained, and wherein the MCR comprises a high temperature region with a temperature at or above a fusion temperature of the fine ash particles, wherein substantially all of the fine ash particles from the exit gas stream are returned to the high temperature region, to achieve improved carbon conversion and reduction in fly ash quantity.

What is claimed is: 
     
         1 . A method for recycling fine ash particles for a multiphase chemical reactor (MCR), wherein coal is partially combusted in the MCR to produce an exit gas stream in which fine ash particles are entrained, and wherein the MCR comprises a high temperature region with a temperature at or above a fusion temperature of the fine ash particles, the method comprising:
 a) separating the fine ash particles from the exit gas stream, and   b) returning the fine ash particles collected in step a) above to the high temperature region.   
     
     
         2 . The method according to  claim 1 , wherein the MCR is selected from the group consisting of a fixed bed reactor, a fluidized bed reactor, and an entrained-flow bed reactor. 
     
     
         3 . The method according to  claim 2 , wherein the MCR is a fluidized bed reactor. 
     
     
         4 . The method according to  claim 3 , wherein the fluidized bed reactor is one used for coal gasification. 
     
     
         5 . The method according to  claim 4 , wherein the fluidized bed reactor comprises a vertical reaction vessel having a dense phase portion and a dilute phase portion above the dense phase portion, and a distribution grid within the vessel in the dense phase portion defining the bottom of the reaction bed, wherein a high temperature zone is located above the distribution grid, and wherein the fine ash particles are returned to the high temperature zone through the distribution grid. 
     
     
         6 . The method according to  claim 5 , wherein the fine ash particles are returned to the high temperature zone using a pneumatic gas conveyor system. 
     
     
         7 . The method according to  claim 6 , where the gas used for the pneumatic conveyor system does not contain oxygen. 
     
     
         8 . The method according to  claim 6 , where the gas used for the pneumatic conveyor system comprises nitrogen, carbon dioxide, hydrogen, syngas, steam, or a mixture thereof. 
     
     
         9 . The method according to  claim 1 , wherein one or more cyclones, one or more baghouse filter systems, one or more ceramic filters, one or more electric precipitators, or a combination thereof, are used to separate or collect the fine ash particles from the exit gas stream. 
     
     
         10 . A multiphase chemical reactor (MCR) in which coal is partially combusted in the MCR to produce an exit gas stream in which fine ash particles are entrained, and wherein the MCR comprises a high temperature region with a temperature at or above a fusion temperature of the fine ash particles, comprising: a fine ash particle collection system for separating the fine ash particles from the exit gas stream, and a fine ash particle conveyor system for returning the fine ash particles to the high temperature region. 
     
     
         11 . The MCR according to  claim 10 , selected from the group consisting of a fixed bed reactor, a fluidized bed reactor, and an entrained-flow bed reactor. 
     
     
         12 . The MCR according to  claim 11 , which is a fluidized bed reactor. 
     
     
         13 . The MCR according to  claim 12 , wherein the fluidized bed reactor is used for coal gasification. 
     
     
         14 . The MCR according to  claim 13 , wherein the fluidized bed reactor comprises a vertical reaction vessel having a dense phase portion and a dilute phase portion above the dense phase portion, and a distribution grid within the vessel in the dense phase portion defining the bottom of the reaction bed, wherein a high temperature zone is located above the distribution grid, and wherein the fine ash particles are returned to the high temperature zone through the distribution grid. 
     
     
         15 . The MCR according to  claim 14 , wherein the fine ash particles are returned to the high temperature zone using a pneumatic gas conveyor system. 
     
     
         16 . The MCR according to  claim 15 , where the gas used for the pneumatic conveyor system does not contain oxygen. 
     
     
         17 . The MCR according to  claim 16 , where the gas used for the pneumatic conveyor system comprises nitrogen, carbon dioxide, hydrogen, syngas, steam, or a mixture thereof. 
     
     
         18 . The MCR according to  claim 10 , wherein one or more cyclones or one or more baghouse filter systems, one or more ceramic filters, one or more electric precipitators, or a combination thereof, are used to separate or collect the fine ash particles from the exit gas stream. 
     
     
         19 . A fluidized bed coal gasification system in which coal-containing fuel particles react with oxygen and steam to produce syngas, the system comprising
 1) a fluidized bed reactor vessel which comprises   a) an upper portion, wherein a fluidized bed region is formed during operation, and wherein an exit gas stream is formed with fly ash particles entrained therein;   b) a lower portion separated from the upper portion by   c) a conically shaped distribution plate with its apex pointing downward, having perforations thereon and a central opening at the apex, wherein bottom ash formed in the fluidized bed region can fall through the central opening and collected in the lower portion of the reactor vessel,   d) a gas inlet through the opening, through which inlet a gas stream rich in oxygen can be injected into a region just above the distribution plate, wherein during operation a high temperature region is formed due to enhanced combustion of the carbon material in the region,   2) a fly ash collection subsystem wherein fly ash particles are separated from the exit gas stream and collected, and   3) a fly ash recycle subsystem, wherein the fly ash particles collected in the fly ash collection system are returned directly into the high temperature region.   
     
     
         20 . The fluidized bed coal gasification system according to  claim 19 , wherein the fly ash recycle subsystem comprises one or more stages of cyclone, one or more baghouse filter systems, one or more ceramic filters, one or more electric precipitators, or a combination thereof. 
     
     
         21 . The fluidized bed coal gasification system according to  claim 20 , wherein the fly ash recycle subsystem comprises a pneumatic gas delivery device for delivering the fly ash. 
     
     
         22 . The fluidized bed coal gasification system according to  claim 21 , wherein the pneumatic gas delivery system has a jet stream outlet through the distribution plate, and the fly ash is delivered directly into the high temperature region just above the distribution grid.