System and method for downdraft gasification

Abstract

A downdraft gasifier for producing a gaseous fuel to be used in an engine from a carbonaceous material with a pyrolysis module, a reactor module, and a heat exchanger system that cooperate to produce the gaseous fuel from the carbonaceous material and to extract particulates from the gaseous fuel from the reactor. The heat exchange system includes a first heat exchanger coupled to the dryer module that heats the carbonaceous material with the gaseous fuel output of the reactor module to dry the carbonaceous material; a second heat exchanger coupled to the pyrolysis module that heats the dried carbonaceous material with the exhaust from the engine to pyrolyze the dried carbonaceous material into tar gas and charcoal; and a third heat exchanger coupled to the reactor module that heats air used to combust the tar gas with the gaseous fuel output of the reactor module to preheat the air.

I claim: 
     
         1 . A downdraft gasifier system for producing a gaseous fuel from a carbonaceous material, the downdraft gasifier system comprising:
 a dryer module;   a pyrolysis module;   a reactor module defining a combustion zone and a reduction zone, the reactor module comprising an air path fluidly connecting an oxygen source to the combustion zone of a reactor module interior, and a gaseous fuel outlet fluidly connected to the reduction zone;   an engine comprising an engine inlet and an exhaust outlet; and   a heat exchanger system comprising:
 a first heat exchanger thermally coupled to and fluidly separated from the dryer module, the first heat exchanger fluidly coupled between the gaseous fuel outlet and the engine inlet; 
 a second heat exchanger thermally coupled to and fluidly isolated from the pyrolysis module, fluidly coupled to the engine exhaust; and 
 a third heat exchanger thermally coupled to and fluidly separated from the air path, the third heat exchanger fluidly coupled between the gaseous fuel outlet and the first heat exchanger. 
   
     
     
         2 . The downdraft gasifier of  claim 1 , further comprising a heat extractor that further extracts heat from the gaseous fuel from the reactor module prior to the first heat exchanger. 
     
     
         3 . The downdraft gasifier of  claim 2 , wherein the heat extractor includes a cyclone module that cooperates with the dryer module, pyrolysis module, and the reactor module to further extract particulates and heat from the gaseous fuel from the reactor module, wherein the cyclone includes a gaseous fuel inlet that receives gaseous fuel from the reactor module, a gaseous fuel path within the cyclone module that extracts heat and particulates from the gaseous fuel, and a gaseous fuel outlet that delivers gas to the first heat exchanger. 
     
     
         4 . The downdraft gasifier of  claim 2 , wherein the heat extractor further includes a fourth heat exchanger that exchanges heat with the gaseous fuel to extract heat from the gaseous fuel. 
     
     
         5 . The downdraft gasifier of  claim 4 , wherein the fourth heat exchanger heats water with the gaseous fuel to extract heat from the gaseous fuel. 
     
     
         6 . The downdraft gasifier of  claim 5 , wherein the carbonaceous material is dried by extracting water content in the carbonaceous material, and wherein the fourth heat exchanger heats the water extracted from the carbonaceous material. 
     
     
         7 . The downdraft gasifier of  claim 5 , wherein the fourth heat exchanger includes a water inlet that receives water, a water path substantially isolated from the gaseous fuel, and a water outlet. 
     
     
         8 . The downdraft gasifier of  claim 7 , wherein fourth heat exchanger substantially vaporizes the water with the heat from the gaseous fuel and wherein the water outlet outputs water vapor into the reactor module. 
     
     
         9 . The downdraft gasifier of  claim 7 , wherein the gaseous fuel path traverses about the cyclone module at least once. 
     
     
         10 . The downdraft gasifier of  claim 9 , wherein the gaseous fuel path revolves about the cyclone module at least once. 
     
     
         11 . The downdraft gasifier of  claim 1 , wherein the dryer module substantially isolates drying from pyrolyzing, and wherein the pyrolysis module substantially isolates pyrolyzing from combusting and reducting. 
     
     
         12 . The downdraft gasifier of  claim 11 , wherein the dryer module includes a drying portion and a condensing portion arranged substantially above the drying portion, wherein the dryer module vaporizes the water content in the carbonaceous material in the drying portion and condenses the rising water vapor in the condensing portion away from the carbonaceous material, thereby drying the carbonaceous material and substantially isolating drying from pyrolyzing. 
     
     
         13 . The downdraft gasifier of  claim 11 , wherein the pyrolysis module is arranged above the reactor and includes a tar gas and charcoal outlet that is coupled to the reactor, and wherein the reactor receives the tar and charcoal from the tar gas and charcoal outlet of the pyrolysis module. 
     
     
         14 . The downdraft gasifier of  claim 13 , wherein the tar gas and charcoal outlet includes a motor that drives the tar gas and charcoal outlet into the reactor. 
     
     
         15 . A method for managing heat within a downdraft gasifier for producing a gaseous fuel from a carbonaceous material to be used in an engine, comprising the steps of:
 drying the carbonaceous material with the heat from the gaseous fuel output in a dryer module to produce dried carbonaceous material;   pyrolyzing the dried carbonaceous material with the heat from the exhaust of the engine in a pyrolysis module to produce tar gas and charcoal;   combusting the tar gas with air and reducing the combusted tar gas with the charcoal in a reactor module to produce gaseous fuel;   preheating the air used to combust the tar gas with the gaseous fuel post reduction; and   extracting heat and particulates from the gaseous fuel post reduction prior to using the heat from the gaseous fuel to dry the carbonaceous material.   
     
     
         16 . The method of  claim 15 , wherein the step of extracting heat and particulates from the gaseous fuel post reduction includes the step of extracting heat and particulates from the gaseous fuel in a cyclone module. 
     
     
         17 . The method of  claim 15 , wherein the step of extracting heat from the gaseous fuel post reduction includes vaporizing water with the heat from the gaseous fuel post reduction and injecting the vaporized water into the reactor module. 
     
     
         18 . The method of  claim 17 , wherein the step of drying the carbonaceous material includes extracting water from the carbonaceous material, and wherein the step of vaporizing water includes vaporizing the water extracted from the carbonaceous material. 
     
     
         19 . The method of  claim 15 , further comprising the steps of substantially isolating the drying carbonaceous material from the pyrolyzing carbonaceous material and substantially isolating the pyrolyzing carbonaceous material from the combusting tar gas and the reducing charcoal. 
     
     
         20 . The method of  claim 15 , further comprising the step of substantially isolating gaseous fuel output from the carbonaceous material in the dryer module while allowing heat exchange between the gaseous fuel output and the carbonaceous material and substantially isolating exhaust gas from the dried carbonaceous material in the pyrolysis module while allowing heat exchange between the exhaust gas and the dried carbonaceous material.