Steam Generating Slurry Gasifier for the Catalytic Gasification of a Carbonaceous Feedstock

Abstract

Steam generating gasification reactors for providing high-pressure and high-temperature steam for catalytic gasification of a carbonaceous feedstock can be based on oxygen blown gasification reactors adapted for processing a slurry feedstock comprising at least 40% water. The exhaust from the slurry gasifier comprises at least steam, carbon monoxide and hydrogen. The slurry composition and the oxygen to fuel ratio can be varied to control the ratio of carbonaceous gases in the generator exhaust. By directing substantially all of exhaust gases produced from the slurry gasification reactor through the catalytic gasifier and subsequent gas separation and sequestration processes, a greatly higher energy efficiency and decreased carbon footprint can be realized.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority under 35 U.S.C. §119 from U.S. Provisional Application Ser. No. 61 / 017,321 (filed Dec. 28, 2007), the disclosure of which is incorporated by reference herein for all purposes as if fully set forth.FIELD OF THE INVENTION[0002]The present invention relates to a steam generating slurry gasifier which produces steam and synthesis gas from an aqueous carbonaceous feed slurry. Further, the invention relates to processes for preparation gaseous products, and in particular, methane via the catalytic gasification of carbonaceous feedstocks in the presence of steam and synthesis gas generated by the slurry gasifier.BACKGROUND OF THE INVENTION[0003]In view of numerous factors such as higher energy prices and environmental concerns, the production of value-added gaseous products from lower-fuel-value carbonaceous feedstocks, such as petroleum coke and coal, is receiving renewed attention. The catalytic gasification of...

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Benefits of technology

[0008]In a fourth aspect, a process is provided for converting a carbonaceous material into a first plurality of gases comprising methane and one or more of hydrogen, carbon monoxide, carbon dioxide, hydrogen sulfide, ammonia and other higher hydrocarbons, the process comprising the steps of: providing a gasifier apparatus having a fluidized bed gasifier and a slurry gasifier according to the first aspect; supplying a particulate composition comprising a carbonaceous material and a gasification catalyst to the fluidized bed gasifier, wherein the gasification catalyst, in the presence of steam and under suitable temperature and pressure, exhibits gasification activity whereby the first plurality of gases is formed; supplying an aqueous carbonaceous slurry, enriched oxygen gas and optionally a syngas to the slurry gasifier; reacting the aqueous carbonaceous slurry in the slurry gasifier in the presence of oxygen and under suitable temperature and pressure so as to generate a second plurality of gases comprising steam, hydrogen and carbon monoxide; introducing the second plurality of gases into the fluidized bed gasifier; reacting the particulate composition in the fluidized bed gasifier in the presence of the second plurality of gases, and under suitable temperature and pressure, to form the first plurality of gases; and at least partially separating the first plurality of gases to produce a stream comprising a predominant amount of one of the gases in the first plurality of gases, wherein the gasification catalyst comprises a source of at least one alkali metal and is present in an amount sufficient to provide, in the particulate composition, a ratio of alkali metal atoms to carbon atoms ranging from about 0.01 to about 0.08; and the aqueous carbonaceous slurry comprises a mixture of carbonaceous material and water at a weight ratio ranging from about 5:95 to about 60:40.

Problems solved by technology

Such methods have the disadvantages of requiring an additional fuel source for the boiler, while producing an exhaust comprising additional acid gases (e.g, carbon dioxide, sulfur dioxide, nitrous oxides), which must be treated and exhausted to the atmosphere or otherwise sequestered.

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