Ammonia storage and injection in NOx control

Abstract

A system is described for storing ammonia and injecting it into the exhaust gas stream of an engine to reduce nitrogen oxides. The ammonia is stored as a liquid mixture ( 70 ) of ammonia and water in a container ( 50 ). In one system, the mixture passes through a hot nozzle and is injected into an upstream portion of the exhaust gas pipe.

1 . In an engine which includes means for combusting hydrocarbons in air to produce work wherein said means also produces a stream of exhaust gasses that contain nitrogen oxides, with the engine having an exhaust conduit through which the exhaust gasses are passed before being emitted into the atmosphere, the improvement comprising: 
 a container;    a liquid mixture of ammonia and water in said container, said container being stored away from said means for combusting to minimize heating;    an injector apparatus coupled to said liquid in said container and to said exhaust conduit, said injector apparatus being constructed to inject at least ammonia of said mixture into said exhaust conduit.    
     
     
         2 . The engine described in  claim 1  wherein: 
 said mixture of ammonia and water in said container includes about 25% ammonia and about 75% water.    
     
     
         3 . The engine described in  claim 1  wherein: 
 said injector apparatus includes a tube that carries said liquid mixture, said tube lying in a heat-exchange relationship with said exhaust conduit to use the heat of the exhaust gasses to heat the liquid mixture of ammonia and water.    
     
     
         4 . The engine described in  claim 1  wherein: 
 said injector apparatus includes a tube that carries said mixture of ammonia and water from said source, and a nozzle coupled to said tube, said injector apparatus being constructed to inject said mixture of ammonia and water through said nozzle into said exhaust conduit.    
     
     
         5 . In an engine which has an engine block with cylinders where hydrocarbons are combusted in air to produce work, and which has an exhaust conduit that carries away a stream of exhaust gasses that contain nitrogen oxides, a source of ammonia and an injection apparatus that is coupled to said source and that injects ammonia into the conduit to reduce nitrogen oxides, the improvement wherein: 
 said source of ammonia comprises a container and a liquid mixture of ammonia and water in said container, said container being thermally isolated from said engine block and said exhaust conduit.    said injection apparatus is constructed to inject ammonia and at least some of the water into said exhaust conduit.    
     
     
         6 . The engine described in  claim 5  wherein: 
 said injector apparatus includes a tube that carries said liquid mixture and that lies in a heat-exchange relationship with said exhaust conduit to use the heat of the exhaust gasses to heat the mixture of ammonia and water.    
     
     
         7 . The engine described in  claim 5  wherein: 
 said mixture of ammonia and water in said container includes about 25% ammonia and 75% water.    
     
     
         8 . A method for reducing nitrogen oxide emission from an engine that has an engine block with cylinders where hydrocarbons are combusted in air to produce work, and which has an exhaust conduit that carries away a stream of exhaust gasses that contain nitrogen oxides, comprising: 
 storing a liquid mixture of ammonia and water in a container while thermally isolating the container from said engine block and said exhaust conduit;    passing said mixture from said container to an injector apparatus, and injecting ammonia and water into said exhaust conduit at a location downstream of said engine block.