Method and apparatus for biomass gasification

Abstract

A system includes a gasifier configured to gasify a mixture of a biomass feedstock and an oxidant to generate a producer gas and a producer gas purification system configured to purify the producer gas from the gasifier. The system also includes a gas supply system configured to supply a gas that is not the oxidant to at least one of the gasifier, or the producer gas purification system, or any combination thereof.

1 . A system, comprising:
 a gasifier configured to gasify a mixture of a biomass feedstock and an oxidant to generate a producer gas;   a producer gas purification system configured to purify the producer gas from the gasifier; and   a gas supply system configured to supply a recycle gas to at least one of the gasifier, or the producer gas purification system, or any combination thereof, wherein the recycle gas comprises an exhaust gas, one or more gases separated from the exhaust gas, or a combination thereof, generated from a combustion system.   
     
     
         2 . The system of  claim 1 , comprising a gas separator configured to separate the exhaust gas into at least a first gas and a second gas, wherein the gas supply system is configured to use the first gas as the recycle gas. 
     
     
         3 . The system of  claim 2 , wherein the first gas comprises carbon dioxide separated from the exhaust gas and used as the recycle gas. 
     
     
         4 . The system of  claim 2 , wherein the gas separator comprises a pressure swing absorption system. 
     
     
         5 . The system of  claim 1 , comprising the combustion system configured to generate the exhaust gas from a combustion of the producer gas. 
     
     
         6 . The system of  claim 1 , comprising a controller coupled to the gas supply system, wherein the controller has a first mode configured to provide the recycle gas to the gasifier and a second mode configured to provide the recycle gas to the producer gas purification system. 
     
     
         7 . The system of  claim 1 , wherein the gasifier comprises:
 a first opening configured to receive the oxidant; and   a second opening configured to receive the recycle gas, wherein the second opening is separate from the first opening.   
     
     
         8 . The system of  claim 1 , wherein the gas supply system is configured to supply the recycle gas to the producer gas purification system at a lower temperature than the producer gas. 
     
     
         9 . The system of  claim 8 , wherein the producer gas purification system comprises one or more scrubbers, and the recycle gas is configured to cool producer gas in the one or more scrubbers. 
     
     
         10 . The system of  claim 8 , wherein the recycle gas comprises the exhaust gas, carbon dioxide separated from the exhaust gas, nitrogen separated from the exhaust gas, or any combination thereof. 
     
     
         11 . A system, comprising:
 a gasifier configured to gasify a mixture of a biomass feedstock and an oxidant to generate a producer gas;   a producer gas purification system configured to purify the producer gas from the gasifier;   a combustion system configured to combust the producer gas from the producer gas purification system to generate an exhaust gas; and   a pressure swing adsorption system configured to separate the exhaust gas from the combustion system into a first gas and a second gas, wherein the pressure swing absorption system is configured to supply the first gas to at least one of the gasifier, or the producer gas purification system, or any combination thereof.   
     
     
         12 . The system of  claim 11 , wherein the producer gas purification system comprises at least one scrubber configured to scrub the producer gas from the gasifier, and the pressure swing absorption system is configured to supply the first gas to the at least one scrubber at a lower temperature than the producer gas to facilitate cooling. 
     
     
         13 . The system of  claim 11 , wherein the producer gas purification system comprises:
 a first water scrubber configured to receive the producer gas from the gasifier;   a second water scrubber configured to receive the producer gas from the gasifier or the first water scrubber, wherein at least one of the first or second water scrubbers comprises a chilled water scrubber;   a water source configured to supply water to at least one of the first or second scrubbers, wherein the first gas is configured to facilitate cooling in at least one of the first or second scrubbers.   
     
     
         14 . The system of  claim 11 , wherein the first gas comprises carbon dioxide. 
     
     
         15 . The system of  claim 11 , comprising a controller having a first mode and a second mode, wherein the first mode is configured to provide the first gas, the second gas, or the exhaust gas to the gasifier, wherein the second mode is configured to provide the first gas, the second gas, or the exhaust gas to the producer gas purification system. 
     
     
         16 . A method, comprising:
 gasifying a mixture of a biomass feedstock and an oxidant in a gasifier to generate a producer gas;   purifying the producer gas from the gasifier using a producer gas purification system;   combusting the producer gas to generate an exhaust gas using a combustion system;   separating the exhaust gas into a first gas and a second gas using a pressure swing adsorption system; and   supplying the first gas to at least one of the gasifier, or the producer gas purification system, or any combination thereof.   
     
     
         17 . The method of  claim 16 , wherein supplying the first gas comprises controlling a flow rate of the first gas based on a temperature of the producer gas in the gasifier. 
     
     
         18 . The method of  claim 16 , wherein the first gas comprises carbon dioxide. 
     
     
         19 . The method of  claim 16 , wherein supplying the first gas to the gasifier comprises facilitating a reaction to convert char into carbon monoxide. 
     
     
         20 . The method of  claim 16 , wherein supplying the first gas to the producer gas purification system comprises facilitating cooling in at least one scrubber used to scrub the producer gas.