WO1997001730A1

WO1997001730A1 - Continuous flow gas generator

Info

Publication number: WO1997001730A1
Application number: PCT/CA1996/000419
Authority: WO
Inventors: Orville V. Burkinshaw
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-06-27
Filing date: 1996-06-25
Publication date: 1997-01-16
Anticipated expiration: 1997-12-27
Also published as: CA2152686A1; AU6183996A

Abstract

The most efficient performer of the various types of burners are those with oxygen starved primary chambers that convert solids to gases to be burned in an after burner. This better system, however needs more capacity per hour to be economical. Increasing its capacity without the addition of this invention will result in higher particulates and SO2 emissions than the regulations allow. This invention resolves these problems by using a variable speed round rotating cone shaped burner floor designed especially for oxygen starved units (4) that injects feedstock (1) continuously with a variable speed auger (3) on to the revolving cone-shaped floor that has a series of steps (9) the number depending on the size of the unit. This exposes the solids to the heat and speeds up the gasification process. The increase in gas production necessitated inventing a better afterburner (15) with an improved gas/air mixing capability, with a longer retention time to assure complete burning of combustible particulates and with a better capability to destroy other undesirable elements in a high temperature up to 2400 °F.

Description

CONTINUOUS FLOW GAS GENERATOR

SPECIFICATIONS AND BACKGROUND OF THE INVENTION

Several developers who expended time and money on various burner systems found that their processes either lacked capacity making them uneconomical or they were not efficient from an Environmental viewpoint.

This invention involves amendments to existing oxygen starved Gas Generators by adding a continuous feed auger that delivers a uniform amount of feedstock on to the top step of a specially designed rotating cone shaped burner floor. As the floor rotates at the desired speed with each one third of a round the feedstock is stirred twice and a scraper then moves the ^' burning material down to the next step. The longer exposure to heat greatly increases the conversion rate of solids to gases while causing little or no turbulence that could raise particulate levels.

Existing continuous feed oxygen starved gas generators equipped with this invention including the modified afterburners described herein will generate an increased flow of gas. This system could be the start of a trend to eliminate land fill sites and remove unsightly garbage piles as well as waste tires that are also unsightly, a fire hazard and breeding grounds for mosquitoes and rats. This invention substantially improves the performance of the conversion of solids to gases resulting in better economics - an essential factor in the success of any system.

A second related and important aspect of this invention described herein was developed to handle the increased amount of gases without creating more particulates or SO₂ emissions. This was achieved by designing an afterburner with more retention time and a more complete mixing of the gases and air. The resulting higher temperature in the afterburner improves its efficiency, while the longer retention time virtually eliminates the combustible particulates and enhances the destruction of unwanted toxins and/or other undesirable elements that may be present in MSW.

These inventions when applied to an oxygen starved burner will increase the conversion rate of solids to gases, be more efficient, at a lower cost per tonne and with less pollution to the air or ground waters.

SUBSTTTUTE SHEET (RULE 26) DISCLOSURE - DETAILED DESCRIPTION OF THE INVENTION AND DRAWINGS.

D(1) Feedstock consisting of Solid Municipal Waste (MSW), tires, wood waste, plastic or other combustible materials are coarse shredded to approximately four inches (1) and conveyed into a hopper (2) that feeds the variable speed auger (3) (FIGURE 1).

D(2) The feedstock material (1) is fed into the primary chamber (4) by the auger (3) on to the larger top step (5) of the rotating floor. In the intense heat of 1600°F to 1700°F the decomposition process commences immediately (FIGURE 1). The material on the top step is stirred twice by teeth (6) and (7) to improve exposure at 1/3 of a turn intervals and is then scraped off each step onto the next lower step by fixed scrapers (8). This procedure is similar on all the steps (9) on the cone shaped rotating floor in the primary chamber (FIGURE^.

D(3) When the feedstock is fully decomposed the ashes are scraped off the lower step (10) into a 24" outlet (11) to fall into the sealed ashes chamber (12) designed to control dust. The accumulation of hot ash in chamber (12) contributes to maintaining a constant temperature in the primary chamber (4) which reduces the amount of gases burned in the said primary chamber to hold the desired temperature level (FIGURE 1).

D(4) The ashes are removed from the ash chamber (12) by an auger (13) that operates intermittently as required to keep the ash chamber from overfilling. At all times a bed of ash is retained to be sure the combustible material is oxidized and the heat is retained (FIGURE 1).

D(5) The gases generated in the primary chamber (4) flow upwards through a throat (14) into the afterburner (15). A damper (16) in the throat regulates the flow of the gases into the afterburner (15) to stabilize the gas/air mixture (FIGURE 1). D(6) An automated igniter (17) ignites the gas/air mixture which is attained by injecting air with a fan (18). Complete mixing of the gases and air is important and is enhanced by a dispersal cone (19). The flow of the burning gas/air mix is diverted sideways and up and down through a series of deflective barriers (20) in the afterburner that lengthens the travel time of the burning gases without materially reducing the velocity. The higher temperature created by a good mix of gas/air up to 2400°F increases its effectiveness in the destruction of toxic substances as the waste is converted to heat/energy (FIGURE 2).

D(7) The waste heat generated by the burning of the gases can be exhausted out the stack (21) or drawn through steam boilers with an I.D. Fan to provide steam heat or energy to drive a turbine to power a generator. Thus waste to electric energy is achieved (FIGURE 1).

D(8) The inventions set out herein have the ability to economically convert wastes to electricity, one of the most important commodities in use day and night without which no country on earth can develop industries or provide a reasonable standard of living for its people.

D(9) The indirect benefit to both developed and developing countries is that a system utilizing these inventions provides electric power economically while simultaneously contributing to cleaning up the continuous flow of garbage every nation on earth is struggling to control. These benefits are achieved without pollution of the air or waters in excess of current allowable emissions. Every nation that applies the principles of the inventions set out herein converting wastes to heat or energy will realize realistic benefits.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

C(1) The claims made indicate that the inventions described herein when applied to oxygen starved Gas Generators sometimes referred to as burners will increase capacity to such an important degree that the overall economics will be substantially improved. This applies to both capital and operating costs.

C(2) The technology involved by this invention is unique and effective in that it increases the exposure of the feedstock to the heat to speed up the conversion of solids to gases. The exposure is created by a continuous auger feed onto a revolving cone shaped burner floor with circular stair steps. As the floor rotates the gasification process is further enhanced by stirring the material twice per round to increase its exposure to the heat prior to it being scraped off each step onto the step immediately below.

C(3) A better performance is assured in that a shallow bed of feedstock, be it garbage, tires, plastic, wood waste, rice hulls, sugar cane or other combustible material travels several hundred feet depending on the size of the unit and the length of the steps on the cone shaped floor. The time of exposure is regulated by a variable speed drive that rotates the said floor and the feed rate is controlled as required by a variable speed feed auger.

0(4) The increased volume of gases as a result of such exposure minimizes the amount of air required in the primary chamber to maintain the temperature and achieve total gasification. The reduction of oxygen molecules in the primary chamber prevents sulphur molecules from bonding with oxygen molecules. Thus this invention is effective in reducing the occurrence of SO₂ especially when tires that contain up to 4% sulfur are used as feedstock. C(5) This invention also relates to an essential modification to the afterburner. The internal design of the said afterburner is constructed to create a high degree of efficiency by obtaining a better mixing of the gases and air. It also extends the retention time of the burning process in the afterburner to completely gasify combustible particulates while the high temperature created stimulates and improves the overall purging process of the emissions.

C(6) The heat range of the afterburner is controlled by the volume of gases generated in the primary chamber and by the butterfly damper that controls the flow of gases from the primary chamber to the afterburner. A fan blows air into the afterburner to be mixed with the said gases in correct proportions to attain good combustion at a controlled high temperature.

0(7) The drawings and description of the functions of the continuous flow Gas Generator indicate why and how these inventions create improved efficiency and increase the quantity of feedstock that can be processed daily.

0(8) The predominant feature of the invention set out herein is that the conversion of solid waste to gases is achieved without emitting visible smoke or other emissions above allowable levels.

C(9) This invention incoφorates a variable speed drive rotating floor in the primary chamber that requires a minimum of air which greatly reduces the turbulence. This minimizes the amount of non combustible particulates that could enter the stack.

0(10) A low volume gentle air flow reduces the risk of non combustible particulates that are the light ends of the ashes from getting caught up by the air flow and carried into the atmosphere as is the case in other types of burners where air volume has to be high to maintain the burn.

SUBSTTTUTE SHEET (RULE 26)