Patent ID: 8001912
Filing Date: 2011-08-23
Classification: C10J,F23G,Y02E,Y02P

Abstract:
1. A method of pyrolyzing biomass at temperatures below 1000 degrees F. to obtain useable ash and heat energy without generating toxic byproducts, the method comprising primary combustion of biomass fuel using an all ceramic gasifier within which air flow is strictly controlled to gasify under starved air conditions in the range of 20 to 40 percent stoichiometric air, the gasifier comprising a plurality of individual modular cells, the individual cells joined together to form a monolithic furnace bed, each individual cell being completely lined with refractory material, upper end of the gasifier closed and sealed using a monolithic dome, the dome comprising a hemi-elliptical section, the hemi-elliptical section comprising a height to diameter ratio of at least 1 to 2, the dome being completely lined with refractory material, a cylindrical sidewall, the sidewall comprising a lower edge, an upper edge, and a refractory lined inner surface, wherein the lower edge of the sidewall is fixed to the furnace bed, the upper edge of the sidewall is fixed to the periphery of the monolithic dome, the sidewall centered on the vertical centerline of the gasifier, each individual cell comprises an overall wedge shape, each individual cell comprising a base, an apex, a first lateral edge and a second lateral edge, the base comprising a curvilinear contour which is identical to that of the sidewall of the gasifier, the apex of the individual cell being truncated adjacent the vertical centerline of the gasifier, the first lateral edge being spaced apart from the second lateral edge such that the respective lateral edges converge from base to apex, the plurality of individual cells are joined together along their respective lateral edges so as to provide a furnace bed which is annular and segmented, each individual cell comprises a feed cone portion and a fuel collection hopper, the feed cone portion overlying the apex, the fuel collection hopper residing between the feed cone portion and the base, the fuel collection hopper being separated from the feed cone portion by an linear, generally horizontal rim section, wherein the fuel collection hopper comprises an downwardly converging duct which terminates in an ash removal means, the fuel collection hopper comprising refractory air introduction means and refractory temperature sensing means, wherein the air introduction means and temperature sensing means within each cell is monitored and controlled independently of the remaining cells, wherein biomass fuel is fed into feed cone portion of the individual cells of the gasifier up from below the furnace bed and along the central vertical axis using fuel feed means, the fuel is received and combusted within the fuel collection hopper of each cell so as to produce useable ash which is discharged from the underside of the fuel collection hopper, and so as to produce a primary combustion flue gas which is discharged from the top of the gasifier, air flow into each cell is controlled using air introduction means, and temperatures within each cell are monitored using temperature sensing means to maximize fuel burn within the cell, and gasification of the fuel is continuous since the fuel feed rate is synchronized with the ash removal rate, the method comprising secondary combustion of the primary combustion flue gas using a cyclonic, staged oxidizer, the oxidizer comprising an elongate, hollow, completely refractory-lined cylindrical body, the body having a first end, a second end opposed to the first end separated from it by a mid portion, and a longitudinal axis, the first end comprising a conical end wall, the conical end wall terminating in an apex, the apex comprising ignition and burning means, the second end comprising a generally flat end wall, the mid portion comprising a cylindrical sidewall, a first baffle and a second baffle, the first baffle and second baffle extending radially inward from the interior surface of the sidewall in a spaced relationship such that the first baffle and the second baffle segment the interior space into a first stage, a second stage, and a third stage, the first baffle and the second baffle each comprising a circular plate, the circular plate comprising a first area, the circular plate comprising a radius which is the same as the interior radius of the sidewall, the circular plate comprising a circular opening, the circular opening comprising a second area, the second area sized to be approximately one third of the first area, wherein a portion of the peripheral edge of the circular opening coincides with both a portion of the peripheral edge of the circular plate and the sidewall, the first baffle extending from the sidewall on a first side of the body, the second baffle extending from the sidewall on a side which is opposed to the first side such that fluid flow through the oxidizer is caused to travel a helical path about the longitudinal axis, the respective first, second and third stages being serially aligned along the longitudinal axis of the body such that the first stage resides between the first end and the first baffle, the second stage resides between the first baffle and the second baffle, and the third stage resides between the second baffle and the second end, the oxidizer comprising a first baffle tuyere array and a second baffle tuyere array, each of the first and second baffle tuyere arrays comprising nozzles which are linearly aligned and spaced-apart, wherein the first baffle tuyere array is located along circular opening within the first baffle, and the second baffle tuyere array is located along the circular opening in the second baffle, wherein the primary combustion flue gas from the gasifier is directed through a first fluid duct into the first stage of the oxidizer where secondary combustion is initiated and performed at temperatures at or below 1800 degrees F. to prevent formation of NOx, secondary combustion flue gas exits the first stage and enters the second stage where air is injected using the first baffle tuyere array to enhance mixing and combustion and to control combustion temperatures, the second stage used to begin burnout of carbon monoxide and volatile organic compounds, secondary combustion flue gas exits the second stage and enters the third stage where air is injected using the second baffle tuyere array to enhance mixing and combustion and to control combustion temperatures, the third stage allowing the flue gas to be maintained at a temperature in the range of 1800 to 2200 degrees F. for a time period of at least one second to ensure burnout of carbon monoxide and volatile organic compounds, and resulting in generally clean flue gas, the generally clean flue gas is discharged from the oxidizer where it is directed through a second fluid duct into an all-refractory air-to-air indirect heat exchanger so that energy can be recovered from the clean flue gas.