Mobile solid waste gasification unit

Abstract

A mobile waste gasification system comprised of a container, at least one gasification chamber, and a produced fuel gas combustion chamber, and may include a control room. Waste material is loaded into a suspended mesh liner that is offset away from the walls of the gasification chamber, thereby increasing the surface area of waste materials that are exposed to gasification conditions, and thus decreasing gasification temperature, time, and cooling period between subsequent gasification procedures. Process gas and supplemental flaring gases are preferably comprised of an oxygen or hydrogen rich gas. Produced fuel gases are withdrawn from the gasification chamber and into the produced fuel gas combustion chamber. The produced fuel gas combustion chamber may be comprised of a maze ignition chamber for the flaring of said fuel gases. Alternatively, the fuel chamber may be comprised of a gas accumulation tank that stores the produced fuel gas.

Description

RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Application No. 60 / 518,245, filed Nov. 7, 2003, and U.S. Provisional Application No. 60 / 561,936, filed Apr. 14, 2004, both of which are incorporated herein by reference in their entirety. This application also claims the benefit of U.S. application Ser. No. 10 / 632,043, filed on Jul. 31, 2003, which in turn is a continuation of U.S. application Ser. No. 10 / 439,398, filed on May 16, 2003, which in turn claims the benefit of U.S. Provisional Application 60 / 381,958, filed on May 17, 2002, all of which are incorporated herein by reference in their entirety.FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] [Not Applicable]MICROFICHE / COPYRIGHT REFERENCE [0003] [Not Applicable]BACKGROUND OF THE INVENTION [0004] Many attempts have been made at creating waste disposal systems that eliminate or reduce the need to landfill municipal solid waste. Traditional approaches have included incineration and pyrolisis. C...

AI Technical Summary

Benefits of technology

[0032] The present invention is directed to an apparatus that converts combustible solids, sludges, and liquids into a usable non-fossil fuel gas. More particularly, the present invention relates to a self-contained mobile gasification unit that includes at least one gasification chamber and a produced fuel gas combustion chamber. Additionally, the present invention may be adapted to also include a control room, wherein the gasification chamber, produced fuel gas combustion chamber, and a control room are all substantially located within the same self contained mobile gasification unit. The mobile gasification unit is preferably a container that has a standard configuration, such as that of a standardized sea cargo shipping container, so that the container may be easily transported from one location to another via a variety of intermodal modes of transportation, including, but not limited to, truck, train, or container ship.

Problems solved by technology

Conventional incineration however is objectionable because the high burn temperatures result in the formation of complex pollutants that are difficult and expensive to control.

Furthermore, the vast majority of incinerated organic material is converted into undesirable carbon dioxide and nitrous oxides, which are implicated in global warming, ozone layer depletion, and the formation of volatile organic compounds which contribute to smog problems in urban areas.

However, the high temperature, depleted oxygen environment of pyrolisis creates some extremely toxic compounds.

Furthermore, pyrolisis is an inefficient method for disposing large volumes of waste materials due to the requirement that pyrolisis feed stocks must be pre-sorted and processed.

However, conventional gasification systems have proved to be somewhat difficult to cost-effectively construct.

These systems have high capital costs.

The permanency of such systems prohibits the ability to move the waste disposal systems to a areas of need as job demands change or vary over time.

Yet, higher gasification temperatures tend to reduce the Btu content of the resulting produced fuel gas.

Longer cycle durations also greatly reduce the overall capacity of the system.

Furthermore, the costs associated with obtaining and maintaining higher gasification temperatures, along with the cost of fabricating a complex gasification reactor chamber that can withstand prolonged exposure to high temperatures, also increase.

Application of refractory material is thus labor intensive, time consuming, and a significantly expensive step.

Additionally, the weight of the refractory liner necessitates a expensive, high strength gasification chamber construction, such as a steel vessel constructed from at least {fraction (1 / 4)} inch thick hot rolled A36 steel plate and heavy structurals.

This additional weight of the superstructure further increases the overall cost of manufacturing, shipping, and installation.

An additional problem with the use of refractory material is the length of time required for cooling the gasification reactor chamber before it can be re-used to gasify a subsequent load of solid waste material.

More specifically, a subsequent gasification process typically cannot begin until the gasification reactor chamber has cooled to approximately 150 degrees Fahrenheit.

Yet, at the end of a process cycle, the clay refractory material tends to retain heat for a long period of time.

The limited waste load capacity of prior art gasification systems often required the construction of multiple gasification reactor chambers to meet demand requirements.

As the length of the rectangular sidewalls is increased to satisfy larger feed stock capacity requirements, the size of the gasification reactor chamber creates problems associated with load density in various feed stocks in the gasification reactor chamber.

This problem typically limits gasification reactor chambers to configurations that are approximately 20 feet high, 20 feet wide, and 20 feet long, accommodating approximately 50 tons of municipal solid waste.

Larger configurations develop problems with the side load waste dump arrangement.

Because of the large size of these chambers, they require substantial fabrication and installation time, and as a result are expensive.

The use of fans and / or air compressors also increases the initial cost of the system and operating and maintenance expenses.

Conventional gasification systems also use cumbersome techniques for moving the produced fuel gas to the point of combustion.

This large piping, and associated ductwork, increases not only equipment cost, but also installation expenses.

A further disadvantage of traditional air draft systems is that produced fuel gases have a tendency to linger in the gasification reactor chamber, and become subject to accidental combustion, which ultimately lowers the Btu content of the extracted produced fuel gas.

This problem is exacerbated by the inconsistency of up-draft air movement in a natural draft system.

This inconsistent flow causes the evacuation of gases from the gasification reactor chambers to frequently stall, produces negative results in the process, and adversely effects the total cycle time for the gasification of the feed stock material.

Additionally, the ability to withdraw and vent gases produced during the gasification process out from the gasification chamber affects the overall gasification process cycle time.

However, because some prior art designs are only capable of moving approximately 9 to 15 cfm, the complete gasification of 2 tons of waste material could require more than 48 hours.

Therefore, the use of ambient air as a process gas to obtain desired oxygen levels in the gasification chamber, results in the unavoidable inclusion of a large volume of nitrogen.

Unfortunately, this additional volume of nitrogen to the gasification process contributes substantially to the formation and ultimate system air emission of nitrous oxides, which is an air emission contaminant that is currently regulated by the Environmental Protection Agency.

Such mixing has usually required that four parts of ambient air be mixed with one part of the produced fuel gas to sufficiently bring the produced fuel gas from its starved oxygen state (+ / −9%) to one of maximum combustibility (17-20%) Yet, as previously mentioned, thermal processes, such as flaring the mixture of produced fuel gas with ambient air, may result in the presence of regulated nitrous oxides in the gas exhaust stream.

The presence of large volumes of nitrogen in ambient air also increases the size, associated fabrication costs, and weight of gasification systems.

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