Carbonization and gasification of biomass and power generation system

Abstract

Biomass, including waste biomass, is gasified by a process in which the biomass is first carbonized, and the char and pyrolysis gas from the carbonizer are respectively fed to a high temperature gasifying part and a gas reformer part of a two-stage gasifier. A gasifying agent is continuously fed to the gasifying part, and intermittently fed to the gas reformer, to maintain the temperature required to avoid tar formation in the gas reformer stage. Multiple carbonization chambers are operated in rotation. When the carbonization/gasification apparatus is used to provide fuel to an electric power generator set, exhaust heat from the generator power plant is fed back to the carbonizer, and can be supplemented by exchange of heat from the gas delivered to generator power plant from the outlet of the gasifier.

1 . A biomass carbonizing-gasifying system for pyrolytic decomposition of a biomass fuel, said biomass carbonizing-gasifying system comprising: 
 a carbonization chamber for producing a carbonized material by heating the biomass fuel;    a two-stage gasifier comprising a high-temperature gasification part for gasifying the carbonized material, and a gas reformer for reforming combustible pyrolysis gas containing tar volatilized in the production of said carbonized material, said gas reformer having an outlet;    means for feeding carbonized material produced in the carbonization chamber to the high-temperature gasification part of the two-stage gasifier;    a pyrolysis gas flow path for sending the combustible pyrolysis gas produced in the carbonization chamber into the gas reformer of the gasifier; and    gasifying agent feed means for feeding a gasifying agent to the high-temperature gasification part of the gasifier, and controllably feeding a gasifying agent containing oxygen to the gas reformer, whereby the temperature at the outlet of the gasifier can be prevented from falling below a predetermined temperature.    
     
     
         2 . The biomass carbonizing-gasifying system according to  claim 1 , in which said gasifying agent feed means comprises means for intermittently feeding said gasifying agent containing oxygen to said gas reformer.  
     
     
         3 . The biomass carbonizing-gasifying system according to  claim 1 , in which the gasifying agent feed means comprises pipes, arranged to feed a gasifying agent containing oxygen both to said high-temperature gasification part, and to said gas reformer.  
     
     
         4 . A biomass carbonizing-gasifying process for pyrolytic decomposition of a biomass fuel said process comprising: 
 heating the biomass fuel in a carbonization chamber to produce a carbonized material and combustible pyrolysis gas containing volatilized tar;    feeding said carbonized material to a high-temperature gasification part of a two-stage gasifier comprising a gasification part and a gas reformer, said gas reformer having an outlet;    feeding said combustible pyrolysis gas containing volatilized tar into said gas reformer;    feeding a gasifying agent to the high temperature gasification part of the two-stage gasifier; and    maintaining the temperature of gas at said outlet of the gas reformer at a level above a predetermined temperature level by feeding a controlled amount of gasifying agent containing oxygen to said gas reformer.    
     
     
         5 . The biomass carbonizing-gasifying process according to  claim 4 , in which the temperature of the gas at said outlet of the gas reformer is maintained at a level above said predetermined temperature level by intermittently feeding a gasifying agent containing oxygen to said gas reformer when the temperature of gas at the outlet of the gas reformer approaches said predetermined level.  
     
     
         6 . The biomass carbonizing-gasifying process according to  claim 4 , in which said predetermined temperature is 1100° C.  
     
     
         7 . A biomass power generation system comprising: 
 a generator set, operated by a gaseous fuel, and releasing exhaust heat in its operation;    a carbonizer for receiving biomass, and receiving exhaust heat released by the generator set and utilizing said exhaust heat for pyrolytically decomposing and carbonizing said biomass and producing char and pyrolysis gas containing volatilized tar; and    a gasifier, arranged to receive said char, and said pyrolysis gas containing volatilized tar, from said carbonizer, for combustion, and gasification of said char and reforming said pyrolysis gas containing tar, thereby generating a gaseous fuel;    in which the generator set is operated by said gaseous fuel formed by the gasifier.    
     
     
         8 . The biomass power generation system according to  claim 7 , in which the gasifier is capable of decomposing the tar in said pyrolysis gas at a temperature of at least 1100° C., thereby reforming said pyrolysis gas.  
     
     
         9 . The biomass power generation system according to  claim 7 , further comprising a heat exchanger arranged to transfer part of the heat of the gaseous fuel generated by the gasifier to the exhaust heat released by the generator set, whereby the heat used for carbonization of the biomass in the carbonizer comprises not only the exhaust heat from the generator set, but also heat from the gaseous fuel generated by the gasifier.  
     
     
         10 . The biomass power generation system according to  claim 8 , further comprising a heat exchanger arranged to transfer part of the heat of the gaseous fuel generated by the gasifier to the exhaust heat released by the generator set, whereby the heat used for carbonization of the biomass in the carbonizer comprises not only the exhaust heat from the generator set, but also heat from the gaseous fuel generated by the gasifier.  
     
     
         11 . The biomass power generation system according to  claim 7 , in which the carbonizer comprises plural carbonization chambers, alternatively operable in rotation.  
     
     
         12 . The biomass power generation system according to  claim 8 , in which the carbonizer comprises plural carbonization chambers, alternatively operable in rotation.  
     
     
         13 . The biomass power generation system according to  claim 9 , in which the carbonizer comprises plural carbonization chambers, alternatively operable in rotation.  
     
     
         14 . The biomass power generation system according to  claim 10 , in which the carbonizer comprises plural carbonization chambers, alternatively operable in rotation.  
     
     
         15 . The biomass power generation system according to  claim 7 , in which: 
 said gasifier is a two-stage gasifier comprising a high-temperature gasification part for gasifying the carbonized material, and a gas reformer for reforming combustible pyrolysis gas containing tar volatilized in the production of said carbonized material, said gas reformer having an outlet;    and in which said system includes:    means for feeding carbonized material produced in the carbonizer to the high-temperature gasification part of the two-stage gasifier;    a pyrolysis gas flow path for sending the combustible pyrolysis gas produced in the carbonizer into the gas reformer of the gasifier; and    gasifying agent feed means for feeding a gasifying agent to the high-temperature gasification part of the gasifier, and controllably feeding a gasifying agent containing oxygen to the gas reformer, whereby the temperature at the outlet of the gasifier can be prevented from falling below a predetermined temperature.    
     
     
         16 . A method of generating power comprising: 
 operating a generator set and releasing exhaust heat in the operation of the generator set;    utilizing said exhaust heat from the generator set for pyrolytically decomposing and carbonizing biomass in a carbonizer, thereby producing char and pyrolysis gas containing volatilized tar;    effecting combustion and gasification of said char, and reforming said pyrolysis gas, in a gasifier, thereby generating a gaseous fuel; and    utilizing said gaseous fuel as a fuel for operation of said generator set.    
     
     
         17 . The method of generating power according to  claim 16 , in which the volatilized tar in said pyrolysis gas is reformed in said gasifiier at a temperature of at least 1100° C.  
     
     
         18 . The method of generating power according to  claim 16 , in which ash from said volatilized tar is melted in said gasifier and converted into slag.  
     
     
         19 . The method of generating power according to  claim 16 , in which the carbonizer comprises plural carbonization chambers, and in which said carbonization chambers are operated in rotation.