Two-Stage Plasma Process For Converting Waste Into Fuel Gas And Apparatus Therefor

Abstract

A two-step gasification process and apparatus for the conversion of solid or liquid organic waste into clean fuel, suitable for use in a gas engine or a gas burner, is described. The waste is fed initially into a primary gasifier, which is a graphite arc furnace. Within the primary gasifier, the organic components of the waste are mixed with a predetermined amount of air, oxygen or steam, and converted into volatiles and soot. The volatiles consist mainly of carbon monoxide and hydrogen, and may include a variety of other hydrocarbons and some fly ash. The gas exiting the primary gasifier first passes through a hot cyclone, where some of the soot and most of the fly ash is collected and returned to the primary gasifier. The remaining soot along with the volatile organic compounds is further treated in a secondary gasifier where the soot and the volatile compounds mix with a high temperature plasma jet and a metered amount of air, oxygen or steam, and are converted into a synthesis gas consisting primarily of carbon monoxide and hydrogen. The synthesis gas is then quenched and cleaned to form a clean fuel gas suitable for use in a gas engine or a gas burner. This offers higher thermal efficiency than conventional technology and produces a cleaner fuel than other known alternatives.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a method and apparatus for a two-stage conversion of organic components contained in solid and / or liquid waste, at high plasma temperature, into a fuel gas suitable for use in a gas engine or turbine for the production of electricity or a gas burner for the production of steam, or in chemical synthesis reactions. [0003] 2. Description of the Prior Art [0004] Numerous methods have been proposed for the conversion of waste into energy. The most common method is incineration. In incineration systems, waste is typically introduced in a high temperature chamber and reacted with large amounts of air. The process can be one stage or two stages. Whether the incineration process is one stage or two stages, the process always uses large amounts of air, resulting in the production of large amounts of hot off-gas, typically laden with entrained particulates and acid gas components. Thermal energ...

AI Technical Summary

Benefits of technology

[0015] In a gasification system, most of the energy from the waste is stored in the form of chemical energy instead of sensible (or thermal) energy as is the case in an incineration system. The amount of gas produced by a gasification system is typically four to five times less than the gas produced in an incineration system. This gives the possibility of quenching the gas from the gasification temperatures (800 to 1100° C. depending on system) down to below saturation using water quenching. This approach eliminates the problem of dioxin formation, which occurs in the 250 to 400° C. range.

[0017] The energy efficiency is higher when air is added to gasify the waste, namely by reacting the waste with oxygen, rather than simply dissociating the waste into simple molecules. The chemical energy of the products of dissociation is typically much higher than the chemical energy of the waste being treated. This means that significant amounts of electrical energy must be used for dissociation. In the present invention, by adding carefully metered amounts of oxygen or air and / or steam to the process, it is possible to limit the amount of electrical (or plasma) energy required for dissociation. In fact, the amount of oxygen fed can be increased so that partial combustion of the waste occurs and the plasma requirements are much reduced. Electrical energy is an expensive form of energy and it is important to use it as efficiently as possible.

[0031] (b) a secondary gasifier to which the primary synthesis gas is fed, said secondary gasifier being equipped with a plasma-torch fired eductor which ensures that the primary synthesis gas entering from the primary gasifier is exposed to a high temperature such as to transform any soot present in said primary gas into CO and to convert any complex organic molecules to simpler molecules CO, CO2 and H2; means for supplying metered amounts of air, oxygen and / or steam into the eductor; said eductor leading to an insulated chamber with a minimal heat loss; and an outlet being provided in said chamber for the fuel gas resulting from the operation.

Problems solved by technology

This means that significant amounts of electrical energy must be used for dissociation.

Electrical energy is an expensive form of energy and it is important to use it as efficiently as possible.

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