Nox removal system for biogas engines at anaerobic digestion facilities

Abstract

Provided herein are methods, devices and systems comprising a reactor that is operatively connected to: (a) a biogas production unit for converting waste to a biogas stream; and (b) an engine that utilizes the biogas stream from the biogas producing unit to produce energy and an engine exhaust.

1 .- 20 . (canceled) 
     
     
         21 . A reactor comprising:
 (a) an inlet for receiving liquid waste;   (b) an inlet for receiving exhaust from an engine that produces energy and an engine exhaust;   (c) a chamber for contacting the liquid waste with the engine exhaust;   (d) an outlet for providing exhaust from the reactor; and   (e) an outlet for the liquid waste to exit the reactor;   
       provided that the reactor is configured to permit flow of the liquid waste from the inlet for receiving liquid waste to the outlet for liquid waste to exit the reactor, and provided that the reactor is configured to decrease NOx emissions in the engine exhaust by contacting the engine exhaust with liquid waste thereby producing an emission with at least about 1.1 times less NOx relative to the engine exhaust. 
     
     
         22 . The reactor of  claim 21  further provided that the reactor is configured to provide exhaust from the reactor-comprising an amount equal to or less than about 1 pound of NOx per MWh of energy produced by the engine. 
     
     
         23 . The reactor of  claim 21  further provided that the reactor is configured to provide an exhaust from the reactor that contains an amount equal to or less than about 0.75 pounds of NOx per MWh of energy produced by the engine. 
     
     
         24 . The reactor of  claim 21  further provided that the reactor is configured to provide an exhaust from the reactor that contains an amount equal to or less than about 0.1 pounds of NOx per MWh of energy produced by the engine. 
     
     
         25 . The reactor of  claim 21  that comprises an absorption chamber that reduces NOx emissions from the engine exhaust using extended absorption. 
     
     
         26 . The reactor of  claim 21  further provided that the reactor is configured to operate:
 (a) at a temperature within the reactor that is within the range of about 50° C. to about 0° C.; 
 (b) at a pressure within the reactor that is within the range of about 1 atm to about 15 atm; 
 (c) at a pH of an absorbing solution within the reactor that is within the range of about 5.5 to about 9; and 
 (d) with a retention time of exhaust that is at least about 10 seconds. 
 
     
     
         27 . The reactor of  claim 21  further provided that that the reactor is configured to produce emission with at least about 1.1 times less NOx when compared to the NOx level obtained from contacting the engine exhaust with tap water instead of liquid waste. 
     
     
         28 . The reactor of  claim 21  further provided that that the reactor is configured to produce emission with about 1.1 to about 2.5 times less NOx when compared to the NOx level obtained from contacting the engine exhaust with tap water instead of liquid waste. 
     
     
         29 . The reactor of  claim 21  further provided that that the reactor is configured to produce emission with at least about 90% less NOx relative to the engine exhaust. 
     
     
         30 . The reactor of  claim 21  further provided that that the reactor is configured to increase an oxygen content of the engine exhaust to at least 15% of the engine exhaust. 
     
     
         31 . A method of reducing SOx emissions of an engine exhaust and producing energy, the method comprising:
 contacting the engine exhaust with a biogas stream in a reactor, wherein the reactor is operatively connected to:   a. a biogas production unit for converting a liquid waste stream to the biogas stream; and   b. an engine that utilizes the biogas stream from the biogas producing unit to produce energy and the engine exhaust.   
     
     
         32 . The method of  claim 31 , wherein the engine exhaust is contacted with the liquid waste stream at 15-105 psi. 
     
     
         33 . The method of  claim 31 , wherein the SOx emissions are reduced by at least 10-fold. 
     
     
         34 . the method of  claim 31 , wherein the SOx content of the engine exhaust is reduced to less than 20 ppm. 
     
     
         35 . The method of  claim 31 , wherein the engine is an internal combustion engine. 
     
     
         36 . The method of  claim 31 , wherein the engine exhaust is obtained from combustion of the biogas stream. 
     
     
         37 . A method of reducing COx emissions of an engine exhaust and producing energy, the method comprising:
 contacting the engine exhaust with a biogas stream in a reactor, wherein the reactor is operatively connected to:   a. a biogas production unit for converting a liquid waste stream to the biogas stream; and   b. an engine that utilizes the biogas stream from the biogas producing unit to produce energy and the engine exhaust.   
     
     
         38 . The method of  claim 37 , wherein the engine exhaust is contacted with the liquid waste stream at 15-105 psi. 
     
     
         39 . The method of  claim 37 , wherein the COx emissions are reduced by at least 10-fold. 
     
     
         40 . the method of  claim 37 , wherein the COx content of the engine exhaust is reduced to less than 20 ppm.