| 摘要 |
A thermodynamic method and system is described and claimed for up-grading the quality of digester methane gas by removing substantially all of the non-combustible carbon dioxide gas from the digester gas in a scrubbing system operated by the waste heat of an internal combustion engine utilizing the up-graded methane gas as its fuel source and driving a generator to produce electric power. In accordance with the invention, raw digester gas is compressed and blended with relatively cold water (absorbent). The compressed gas-water mixture is scrubbed in a contact tower with the result that an absorbent-condensed gas stream (primarily water and condensed carbon dioxide) is formed. The absorbent-condensed gas stream is removed from the tower, heated and expanded to release the carbon dioxide component of the stream as product CO2 gas. Non-condensible gases (primarily methane) are removed from the contact tower and utilized as up-graded fuel in an internal combustion engine driving a generator to produce power. The engine is water cooled with the result that saturated steam is produced in the cooling system of the engine. The waste heat of the steam is utilized to both generate refrigeration to cool the water absorbent after the release therefrom of product CO2 gas and to heat the absorbent-condensed gas stream before such stream is expanded to release the product CO2 gas. During such utilization the steam is condensed to form water condensate for return to the engine as coolant water.
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