초록 ▼

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

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.

대표청구항 ▼

In the method of up-grading the heating value quality of digester generated methane gas by removing carbon dioxide gas therefrom and using the up-graded methane gas as fuel in an internal combustion engine - generator system to produce electric power, the steps comprising: (a) mixing raw digester me

In the method of up-grading the heating value quality of digester generated methane gas by removing carbon dioxide gas therefrom and using the up-graded methane gas as fuel in an internal combustion engine - generator system to produce electric power, the steps comprising: (a) mixing raw digester methane gas and cold water absorbent under relatively high pressure and introducing the cold gas-absorbant mixture to a contact tower to separate methane gas and other non-condensible gases from said raw digester gas and to condense the carbon dioxide component and other condensible gases of said raw digester gas for absorption by said water absorbant; (b) removing the methane gas and other non-condensible gases from said contact tower as an overhead gas mixture of higher heating value quality, and utilizing said gas mixture as combustible fuel in the engine of an internal combustion engine - generator system to produce electric power; (c) removing the water absorbent with absorbed condensed carbon dioxide and other condensed gases from said contact tower as a relatively high pressure bottoms absorbent - condensed gas stream, and heating and expanding said stream to reduce the pressure thereof and vaporize and release carbon dioxide gas and other absorbed gases from said absorbent; (d) introducing water coolant to the cooling section of the engine of said engine - generator system to cool said engine with the attendant conversion of said coolant to saturated steam; (e) removing said saturated steam from the cooling section of said engine; (f) utilizing said steam in part to generate refrigeration to cool the water absorbent after the release therefrom of carbon dioxide gas and other absorbed gases and before the recycle of said absorbent as the cold water absorbent for mixing with raw digester methane gas and in part to heat the bottoms absorbent-condensed gas stream removed from said contact tower before said stream is expanded to release carbon dioxide gas and other absorbed gases therefrom, said utilization of said steam resulting in the cooling thereof to form water condensate; and (g) recycling said water condensate to the cooling section of the engine of said engine - generator system as the water coolant for said engine.