Importance

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Abstract

A method is provided for operating a coal gasifier, preferably an oxygen-blown two zone-coal gasifier, without the need for the addition of water and producing a high LHV-content coal product fuel gas from coal. A first supply of coal, preferably dry coal, first supply of carbon dioxide, and a supply of oxygen are passed into a high pressure combustion vessel wherein the coal reacts with the oxygen and carbon dioxide to form an exothermic zone producing a combustion temperature in excess of the melting point of the ash in the coal. This in turn produces a melted ash and a combustion product gas comprising carbon monoxide. The melted ash is drained or otherwise removed for disposal and the combustion product gas subsequently is passed into an entrained flow reaction vessel. A second supply of dry coal and a second supply of carbon dioxide are injected into the entrained flow reaction vessel wherein the coal thermally reacts with the combustion product gas and the carbon dioxide and produces a product fuel gas. The resultant product fuel gas comprises more moles of carbon monoxide than moles of carbon in the first and second supplies of coal. The product fuel gas may exhibit a gas exit temperature at a value below the melting point of the coal ash but no lower than about 1400° Kelvin, and it may be passed to a turbine having closed loop internal cooling thereby recovering energy and lowering the product gas pressure and temperature prior to potential heat exchange with incoming gasifier feed gases.

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First Claim