Grate clearing and ash removal system for gasification furnace

Abstract

A relatively level fuel grate surface angle cooperates with multiple feed screws that press solid fuel material into and across the grate surface to continually clear off the grate. Air spaces between each pair of adjacent grate elements for under fire air each have a ninety degree deflector flange at the top of the air space extending from one grate element across the air space and up and over an adjacent grate element to deflect under fire airflow across the adjacent grate element to act as a grate sweeper. The smooth curved surface of the deflector flange between grate elements facilitates movement of the fuel and ash material and prevents from one grate element to the next and prevents clogging of the airflow space.

1 . An integrated system of fuel grate and fuel movement components and under-fuel air flow directing components for grate clearing and fuel movement in a biomass gasification furnace, the system comprising:
 multiple feed screws to feed biomass fuel material through a biomass fuel feed opening into a gasification chamber of a biomass gasification furnace;   a fuel grate comprising a series of interconnected grate elements aligned in a linear array having aligned top surfaces, the grate extending from the biomass fuel feed opening into and across the gasification chamber angled downwardly at a slight acute angle from the horizontal so that the feed screws press the fuel material into and across the aligned top surfaces of the grate elements to keep the bottom of the solid fuel moving along the aligned top surfaces of the grate elements in a scraping cleaning action during gasification and to push resulting ash byproduct down the grate and into an ash removal auger for removal;   each adjacent pair of grate elements having an air space therebetween to receive under fire airflow therethrough, and each grate element further comprising an airflow directing flange extending from one grate element over the air space and over the top of the adjacent lower grate element parallel to the top surface of the lower grate element to direct the airflow over the lower grate element so that the air flow blows across the top surface of the lower grate element to act as a grate sweeper to clean the top surface; thereby providing an integrated system of fuel grate and fuel movement components and under-fuel, airflow directing components for grate clearing and fuel movement in the biomass gasification furnace.   
     
     
         2 . The system of  claim 1  wherein the airflow directing flange comprises a smooth curved top surface transitioning smoothly into a smooth flat top surface over the lower grate element to facilitate movement of the fuel and ash material from one grate element to the next and to prevent clogging of the air space therebetween. 
     
     
         3 . The system of  claim 2  wherein each of the grate elements comprises a grate bar extending across the fuel grate, the grate bar formed from a metal square U-shaped channel having an extending top of one leg bent over the adjacent grate bar to form the airflow deflector, the square U-shaped channel further comprising a high temperature refractory material filling the channel to form a flat top surface aligned with the short leg of the square U-shaped channel.