Downdraft Fixed-Bed Gasifier for Producing a Product Gas from Pourable Biomass Particles

Abstract

A downdraft fixed-bed gasifier for producing product gas from pourable biomass particles includes a gasifier container, a gasifier component, a feeder, an air supply inlet, a grate and a product gas vent. The gasifier container has a larger diameter than does the gasifier component. The lower open end of the gasifier component extends down into the gasifier container. The feeder is adapted to receive biomass particles into the upper closed end of the gasifier component. Combustion air is fed into the gasifier component through the air supply inlet located near the upper closed end. The grate supports the biomass particles and is disposed in a lower portion of the gasifier container below the lower open end of the gasifier component. Product gas generated from oxidizing the biomass particles exits the gasifier container through the product gas vent located in the side of the container below the level of the grate.

1 - 20 . (canceled) 
     
     
         21 . A downdraft fixed-bed gasifier for producing a product gas from pourable biomass particles, comprising:
 a gasifier container with a first diameter;   a gasifier component with a second diameter, an upper closed end and a lower open end, wherein the lower open end of the gasifier component extends down into the gasifier container, wherein the upper closed end of the gasifier components projects up and out of the gasifier container, and wherein the first diameter is larger than the second diameter;   a feeder adapted to receive biomass particles into the upper closed end of the gasifier component;   an air supply inlet that enters the gasifier component near the upper closed end and through which combustion air is fed into the gasifier component;   a grate adapted to support the biomass particles that is disposed in a lower portion of the gasifier container; and   a product gas vent leading out of the gasifier container below the grate and through which the product gas generated from the biomass particles exits the gasifier container, and wherein the gasifier component is disposed in the gasifier container such that a first distance remains between the lower open end of the gasifier component and the grate.   
     
     
         22 . The downdraft fixed-bed gasifier of  claim 21 , wherein each of the gasifier container and the gasifier component has a circular cross-section. 
     
     
         23 . The downdraft fixed-bed gasifier of  claim 22 , wherein the gasifier component is arranged coaxially with respect to the gasifier container. 
     
     
         24 . The downdraft fixed-bed gasifier of  claim 22 , wherein each of the gasifier container and the gasifier component has a constant diameter. 
     
     
         25 . The downdraft fixed-bed gasifier of  claim 21 , wherein the grate is rotatable. 
     
     
         26 . The downdraft fixed-bed gasifier of  claim 21 , wherein the first distance is 90% to 110% of the second diameter. 
     
     
         27 . The downdraft fixed-bed gasifier of  claim 21 , wherein the second diameter is 50% to 80% of the first diameter. 
     
     
         28 . The downdraft fixed-bed gasifier of  claim 21 , further comprising:
 a nozzle of an ignition device leading into the gasifier container above the grate and below the lower open end of the gasifier component, wherein the nozzle is adapted to inject hot air into the gasifier container.   
     
     
         29 . The downdraft fixed-bed gasifier of  claim 28 , wherein the nozzle is ceramic. 
     
     
         30 . The downdraft fixed-bed gasifier of  claim 21 , further comprising:
 a biomass particle storage container; and   a biomass particle conveyor, wherein the biomass particle conveyor is connected to the feeder by a first airtight lock valve, wherein the biomass particle storage container has a second airtight lock valve, and wherein the biomass particle conveyor moves biomass particles from the biomass particle storage container through the feeder and into the gasifier component in an airtight manner sealed from the outside environment.   
     
     
         31 . The downdraft fixed-bed gasifier of  claim 21 , further comprising:
 a gas processing device connected to the product gas vent, wherein the gas processing device is connected to a combustion engine that operates using the product gas.   
     
     
         32 . The downdraft fixed-bed gasifier of  claim 31 , wherein the gas processing device includes a heat exchanger that cools the product gas received from the product gas vent. 
     
     
         33 . The downdraft fixed-bed gasifier of  claim 21 , further comprising:
 a level sensor that detects a level of the biomass particles in the gasifier component.   
     
     
         34 . A method of operating a downdraft fixed-bed gasifier, comprising:
 filling a gasifier component with biomass particles to a predetermined fill level, wherein a lower open end of the gasifier component extends down into a gasifier container, wherein the gasifier component is arranged coaxially with respect to the gasifier container, and wherein the biomass particles are supported by a grate disposed below the lower open end of the gasifier component in a lower portion of the gasifier container;   supplying air through an air supply inlet into the gasifier component;   discharging a product gas from a product gas vent leading out of the gasifier container below the grate, wherein the product gas is generated from the biomass particles; and   adding additional biomass particles to the gasifier component so as to maintain the predetermined fill level of biomass particles in the gasifier component as biomass particles are consumed by generating the product gas.   
     
     
         35 . The method of  claim 34 , further comprising:
 rotating the grate.   
     
     
         36 . The method of  claim 34 , wherein the biomass particles are wood pellets. 
     
     
         37 . The method of  claim 34 , wherein the biomass particles include a portion of kaolin, and wherein the portion is 1% to 5% by weight. 
     
     
         38 . The method of  claim 34 , further comprising:
 igniting the biomass particles by injecting air with a temperature of more than 300° C. into the gasifier container below the lower open end of the gasifier component.   
     
     
         39 . The method of  claim 34 , further comprising:
 stopping the adding of additional biomass particles; and   stopping the supplying of air when the biomass particles have been consumed such that an upper extent of the biomass particles has dropped to a predetermined lower cutoff level in the gasifier component.   
     
     
         40 . The method of  claim 34 , wherein ash is produced as product gas is generated from the biomass particles, further comprising:
 discharging the ash from the gasifier container in the product gas that is discharged from the product gas vent.