Streamlined methane gas generation system

Abstract

A process for producing high purity methane gas from digested or composted organic materials as well as a high purity methane gas generation system that operates in accordance with this process are provided. The inventive system, which is capable of delivering at least about 0.5 slpm of methane product gas, is streamlined in design and provides a more reliable and cost-effective source of renewable methane gas.

1 . A streamlined process for producing high purity methane gas from digested or composted organic materials, which comprises: 
 (a) digesting or composting organic materials to produce a mixed gas stream containing methane, carbon dioxide and trace impurities including hydrogen sulfide, nitrogen and oxygen, wherein the mixed gas stream may also contain small quantities of water;    (b) directing the biogas or mixed gas stream to a first mixed gas purification device for removing at least a portion of the hydrogen sulfide from the mixed gas stream;    (c) directing portions of the desulfurized, mixed gas stream to one or more mixed gas-driven engines that power one or more compressors, wherein the mixed gas stream serves to fuel the one or more mixed gas-driven engines;    (d) directing remaining portions of the desulfurized, mixed gas stream to the one or more compressors for compressing the mixed gas stream; and    (e) directing the compressed, desulfurized, mixed gas stream to a second mixed gas purification device for removing at least a portion of the carbon dioxide and any excess nitrogen from the mixed gas stream to produce a high purity methane gas product stream.    
     
     
         2 . The streamlined process for producing high purity methane gas of  claim 1 , wherein the biogas or mixed gas stream is produced by anaerobically digesting the organic materials.  
     
     
         3 . The streamlined process for producing high purity methane gas of  claim 1 , which further comprises directing portions of the mixed gas stream or desulfurized, mixed gas stream to one or more mixed gas-driven engines for powering one or more generators.  
     
     
         4 . A streamlined process for producing high purity methane gas from digested or composted organic materials, which comprises: 
 (a) digesting or composting organic materials to produce a mixed gas stream containing methane, carbon dioxide and trace impurities including hydrogen sulfide, nitrogen and oxygen, wherein the mixed gas stream may also contain small quantities of water;    (b) directing the mixed gas stream to means for: (i) removing at least a portion of any water contained in the mixed gas stream; (ii) aerating the mixed gas stream; and (iii) heating the mixed gas stream to a temperature ranging from about 15 to about 33° C.;    (c) directing the condensed, aerated and heated mixed gas stream to a first mixed gas purification device for removing at least a portion of the hydrogen sulfide contained therein;    (d) directing a portion of the desulfurized, mixed gas stream to one or more mixed gas-driven engines for fueling same, wherein the one or more mixed gas-driven engines power one or more compressors;    (e) directing remaining portions of the desulfurized, mixed gas stream to the one or more compressors for compressing the mixed gas stream; and    (f) directing the compressed, desulfurized, mixed gas stream to a second mixed gas purification device for removing at least a portion of the carbon dioxide and any excess nitrogen contained therein to produce a high purity methane gas product stream.    
     
     
         5 . The streamlined process for producing high purity methane gas of  claim 4 , wherein the mixed gas stream is produced by anaerobically digesting the organic materials.  
     
     
         6 . The streamlined process for producing high purity methane gas of  claim 4 , which further comprises directing portions of the mixed gas stream or desulfurized, mixed gas stream to one or more mixed gas-driven engines for powering one or more generators.  
     
     
         7 . The streamlined process for producing high purity methane gas of  claim 4 , which further comprises directing the high purity methane gas product stream to means for neutralizing sudden pressure surges in the product stream.  
     
     
         8 . A streamlined, high purity methane gas generation system, which comprises: 
 (a) one or more devices for digesting and/or composting organic materials to produce a mixed gas stream containing methane, carbon dioxide and trace impurities including hydrogen sulfide, nitrogen and oxygen;    (b) a first mixed gas purification device, which serves to remove at least a portion of the hydrogen sulfide from the mixed gas stream, wherein the first mixed gas purification device is in fluid communication with the one or more devices for digesting and/or composting organic materials;    (c) at least one mixed gas-driven compressor, which serves to compress the desulfurized, mixed gas stream, wherein the at least one mixed gas-driven compressor is in fluid communication with the first mixed gas purification device; and    (d) a second mixed gas purification device, which serves to remove at least a portion of the carbon dioxide and any excess nitrogen from the compressed, desulfurized, mixed gas stream to produce a high purity methane gas product stream, wherein the second mixed gas purification device is in fluid communication with the at least one mixed gas-driven compressor.    
     
     
         9 . The streamlined, high purity methane gas generation system of  claim 8 , wherein the system is self-sustaining during operation, requiring no outside sources of energy.  
     
     
         10 . The streamlined, high purity methane gas generation system of  claim 8 , wherein the one or more devices for digesting and/or composting organic materials comprises one or more anaerobic digesters.  
     
     
         11 . The streamlined, high purity methane gas generation system of  claim 8 , which further comprises one or more generators which are powered by one or more mixed gas-driven engines.  
     
     
         12 . The streamlined, high purity methane gas generation system of  claim 8 , wherein the second mixed gas purification device is a pressure swing absorption device.  
     
     
         13 . The streamlined, high purity methane gas generation system of  claim 12 , wherein the pressure swing absorption device comprises at least two molecular sieve chambers.  
     
     
         14 . The streamlined, high purity methane gas generation system of  claim 8 , which further comprises one or more high pressure, mixed gas-driven compressors for further compressing the methane gas product stream, wherein the one or more high pressure, mixed gas-driven compressors are in fluid communication with the second mixed gas purification device.  
     
     
         15 . The streamlined, high purity methane gas generation system of  claim 8 , which produces up to 3,000 standard liters per minute of methane gas at pressures ranging from about 1.0 to about 1.4 megapascals, wherein the methane gas has a purity level of greater than 90%.  
     
     
         16 . A streamlined, high purity methane gas generation system, which comprises: 
 (a) one or more devices for digesting and/or composting organic materials to produce a mixed gas stream containing methane, carbon dioxide and trace impurities including hydrogen sulfide, nitrogen and oxygen;    (b) means for removing at least a portion of any water contained in the mixed gas stream, which is in fluid communication with the one or more devices for digesting and/or composting organic materials;    (c) means for aerating the mixed gas stream, which is in fluid communication with the one or more devices for digesting and/or composting organic materials;    (d) means for heating the mixed gas stream to a temperature ranging from about 15 to about 33° C., which is in fluid communication with the one or more devices for digesting and/or composting organic materials;    (e) a first mixed gas purification device, which serves to remove at least a portion of the hydrogen sulfide from the mixed gas stream, wherein the first mixed gas purification device is in fluid communication with the one or more devices for digesting and/or composting organic materials;    (f) at least one mixed gas-driven compressor in fluid communication with the first mixed gas purification device; and    (g) a second mixed gas purification device, which serves to remove at least a portion of the carbon dioxide and any excess nitrogen from the mixed gas stream to produce a methane gas product stream, wherein the second mixed gas purification device is in fluid communication with the at least one mixed-gas driven compressor.    
     
     
         17 . The streamlined, high purity methane gas generation system of  claim 16 , wherein the system is self-sustaining during operation, requiring no outside sources of energy.  
     
     
         18 . The streamlined, high purity methane gas generation system of  claim 16 , wherein the one or more devices for digesting and/or composting organic materials comprises one or more anaerobic digesters.  
     
     
         19 . The streamlined, high purity methane gas generation system of  claim 16 , which further comprises one or more generators which are powered by one or more mixed gas-driven engines.  
     
     
         20 . The streamlined, high purity methane gas generation system of  claim 16 , wherein the second mixed gas purification device is a pressure swing absorption device.  
     
     
         21 . The streamlined, high purity methane gas generation system of  claim 20 , wherein the pressure swing absorption device comprises at least two molecular sieve chambers.  
     
     
         22 . The streamlined, high purity methane gas generation system of  claim 16 , which further comprises one or more high pressure, mixed-gas driven compressors for further compressing the methane gas product stream, wherein the one or more high pressure, mixed gas-driven compressors are in fluid communication with the second mixed gas purification device.  
     
     
         23 . The streamlined, high purity methane gas generation system of  claim 16 , which produces up to 3,000 standard liters per minute of methane gas at pressures ranging from about 1.0 to about 1.4 megapascals, wherein the methane gas has a purity level of greater than 90%.