System for processing of biogas to produce electricity in fuel cells

Abstract

A system including biogas purification and provides biogas as feedstock to a solid oxide fuel cell. The biogas purification treatment process provides a polished biogas that is substantially free of carbonyl sulfides and hydrogen sulfide. The system uses a biogas treatment apparatus, that includes apparatus such as a packed columns, comprising copper oxide or potassium permanganate packing material, and an activated carbon component configured to treat the biogas by polishing it to remove carbonyl sulfides and deleterious trace residues, such as hydrogen sulfide, that were not removed by any prior bulk H2S removal steps. In addition, an oil removal device is used to remove any entrained fine oil droplets in the biogas. A polished biogas having in the range of 60% methane is charged to the fuel cell. Electricity generated may be fed into a grid or used directly as energy to charge electrical-powered vehicles, for example. Energy credits are tracked in real time and are appropriately assigned.

1 . A system of producing electricity directly from biogas, the system comprising:
 a digester producing a raw digester gas, the raw digester gas comprising methane, carbon dioxide and sulfur compounds;   a biogas treatment apparatus configured to remove sulfur compounds from the raw digester gas to produce the biogas;   a biogas purification treatment apparatus configured to purify the biogas to obtain a purified biogas suitable for methane-to-electricity-fuel cell operation; and   a fuel cell configured to receive a charge of the purified biogas and to produce the electricity directly from the purified biogas, wherein the electricity produced from the purified biogas is associated with electrical charges to generate renewable energy credits for appointment.   
     
     
         2 . The system of  claim 1 , wherein the raw digester gas is produced from animal manure. 
     
     
         3 . The system of  claim 2 , wherein the animal manure comprises cow manure. 
     
     
         4 . The system of  claim 1 , wherein the biogas is free of siloxanes. 
     
     
         5 . The system of  claim 1 , wherein the purified biogas exiting the biogas purification treatment apparatus is free of carbonyl sulfides. 
     
     
         6 . The system of  claim 1 , wherein the purified biogas has been treated to remove carbonyl sulfides before the fuel cell receives the biogas. 
     
     
         7 . The system of  claim 6 , wherein the biogas purification treatment apparatus further comprises an apparatus comprising copper oxide packing configured to treat the biogas by removing carbonyl sulfides. 
     
     
         8 . The system of  claim 1 , wherein the fuel cell continuously receives a rate of charge of biogas above a minimum turndown rate of the fuel cell. 
     
     
         9 . The system of  claim 1 , further comprising apparatus to convert a direct electrical current produced by the fuel cell to alternating current, and apparatus to feed alternating current to an electrical grid. 
     
     
         10 . The system of  claim 1 , wherein the fuel cell is configured to produce carbon dioxide and water. 
     
     
         11 . The system of  claim 1 , comprising a plurality of animal manure digesters, each producing raw digester gas. 
     
     
         12 . The system of  claim 11 , comprising a plurality of animal manure digesters, each producing raw digester gas, wherein the raw digester gas from each of the animal manure digesters is treated in the biogas treatment apparatus to remove hydrogen sulfide and produce a treated biogas, and the treated biogas from each of the digesters is combined and charged as feedstock to the biogas purification apparatus. 
     
     
         13 . The system of  claim 1  wherein the fuel cell operates at 80 to 100% of capacity. 
     
     
         14 . The system of  claim 1 , wherein the biogas comprises up to about 40 mol. % carbon dioxide. 
     
     
         15 . The system of  claim 10 , wherein the fuel is a solid oxide fuel cell, further wherein the fuel cell operates at temperatures below 750° C., and further wherein the system reuses the water on a farm having the animal manure digester and uses the carbon dioxide to promote plant photosynthesis. 
     
     
         16 . The system of  claim 1 , further comprising a computing device configured to receive data describing the amount of the electricity produced from the purified biogas, receive data describing an amount of the electrical charges received by the EVs, and calculate the renewable energy credits. 
     
     
         17 . The system of  claim 16 , further comprising an apparatus configured to measure, record and transmit data, to the computing device, the data describing the amount of the electricity produced from the purified biogas, the data describing an amount of the electrical charges received by the EVs, and the calculated renewable energy credits, wherein transmitting of the data is in real time. 
     
     
         18 . The system of  claim 1 , wherein the biogas purification treatment apparatus comprises materials to remove carbonyl sulfide from biogas. 
     
     
         19 . The system of  claim 18 , wherein the materials include one or more of copper oxide and potassium permanganate. 
     
     
         20 . The system of  claim 17 , wherein the real time transmitted data can be used to “book and claim” renewable energy credits in real time.