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.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]Not Applicable.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]Not Applicable.THE NAMES OF THE PARTIES TO A JOINT RESEARCH OR DEVELOPMENT[0003]Not Applicable.BACKGROUND OF THE INVENTIONField of the Invention[0004]The present invention relates to biomass fuel gasification chambers and particularly to a grate clearing and ash removal system and method for a gasification furnace; the system comprises a relatively level grate surface angle, multiple feed screws which press fuel material into and across the level grate surface, and 90 degree deflection of the under fire air, up through the grate bar spacing, and against a deflector changing the air flow to blow across the adjacent grate bar and act as a grate sweeper. Description of Related Art including information disclosed under 37 CFR 1.97 and 1.98[0005]The basic gasification furnace works by providing an automatic feed of wood chips or other solid fuel onto a sloped g...

AI Technical Summary

Benefits of technology

[0017]An object of the present invention is to provide an integrated three component approach to grate clearing, utilizing only a non-mechanical grate structure and existing components to achieve the grate clearing, wherein the success of the combination of these factors leads to longer run times, longer term combustion efficiency and load maintenance, less frequent shut down for grate maintenance, less ash fusion and clinkering, and less mechanical maintenance requirements.

[0018]In brief, multiple feed screws pushing the fuel against and across the grate to maintain a continually scraping action of the solid fuel on the grate, to provide a relatively level grate with only a slight downward angle into the gasification chamber to assist the feed screws in pushing the entire fuel pile including the bottom of the fuel pile across the grate to move the fuel into the smoldering gasification area and push the ashes into the augur in the ash removal bin, and to provide regularly spaced air spaces across the width of the grate to receive upward air flow and orthogonal air directing flanges above each air space and over the top of the adjacent grate element to direct the airflow over each grate element parallel to the grate element in a continual cleaning action and to provide a smooth transition of the fuel and ash material from one grate component to the next and prevent fuel and ash from falling into the air spaces, thereby utilizing a three component approach to grate clearing, utilizing only a non-mechanical grate structure and existing components to achieve the grate clearing.

[0020]The combination of these three factors allows for more successful grate clearing and maintenance. It eliminates the need for to frequent shut down, and / or mechanical systems to maintain the grate surface area. This allows for longer run times, better fuel utilization, longer term combustion efficiency and load maintenance, less ash fusion and clinkering, less frequent shut down for grate maintenance, and increased quality combustion, and therefore improved air quality.

Problems solved by technology

Natural mineral contents of fuels and tramp mineral materials accreted to the fuel tend to cause major problems maintaining good air flow, and therefore good quality combustion.

Steep angled grates attempt to use gravity to move the solid fuel and ash down the grate, but the gravity alone is not sufficient to keep the grate clean.

Steepness of the fuel grate in a gravity feed has to be in excess of the angle of repose of the material, which for ash, which is fairly dense is fairly steep resulting in the feed screws pushing out over the top of the fuel pile, and not moving the material successfully.

The consequence is the build up and melting of ash material on the grate, causing poor fuel utilization and decreasing system output, which requires the furnace to be shut down for manual grate maintenance, or have an elaborate moving or automated grate agitation approach to minimize the grate build up and ash fusion.

These “systems” are high cost and have high maintenance components which often breakdown, clog up, or ultimately fail to successfully stop the ash build up problem without frequent shut down and manual maintenance.

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