Ammonia injection in NOx control

A method for reducing nitrogen oxides in the exhaust gasses of an engine that combusts hydrocarbon in the presence of air and that produces a stream of exhaust gasses, comprising:

• passing ammonia in a gaseous state to provide ammonia gas, to an injector and injecting at least components of the ammonia gas from said injector, into said stream of exhaust gasses;
• activating said ammonia gas to break down at least 10% of said ammonia gas into components of ammonia, prior to injecting said ammonia gas and components into said stream of exhaust gasses and prior to allowing said ammonia gas to come into direct contact with said exhaust gases.

An engine which has a fuel injector apparatus positioned to inject hydrocarbon fuel into masses of air to combust them and produce work and to also produce a stream of exhaust gases that contain nitrogen oxides, with the engine having an exhaust conduit through which said stream of exhaust gases flow before being emitted into the environment, and with said fuel injector apparatus including an electronic fuel injector circuit that generates electrical currents whose time durations at least partially determine the average flow rate of fuel that is injected into said masses of air, the improvement comprising:

• ammonia injection apparatus comprising an injector coupled to said exhaust conduit to inject ammonia into said stream of exhaust gases, and a control that is coupled to said electrical currents of said electronic fuel injector circuit and that controls operation of said injector to respectively increase and decrease the flow rate of ammonia injected by said injector into said exhaust conduit as the average time durations of said electrical currents increase and decrease.

A method for controlling the injection of ammonia through an electrically operated valve into an exhaust gas conduit of an engine, where said engine includes a fuel injector and an electronic fuel injector circuit that generates fuel injection control currents whose average duration per unit of time determines the flow rate of fuel through said fuel injector, comprising:

• using said fuel injection control currents to control the opening of said valve to flow ammonia through said valve at a flow rate that is generally proportioned to the duration per unit of time of said injection control currents.

In an apparatus for receiving ammonia and injecting at least components of the ammonia into a stream of exhaust gasses of an engine the improvement, comprising:

• means for activating said ammonia to decompose at least 10% of the ammonia into ammonia components prior to injecting said activated ammonia into said stream of exhaust gasses, with said means for activating being constructed to isolate said ammonia from said stream of exhaust gasses until at least 10% of the ammonia that is being injected into the stream of exhaust gasses has already been decomposed prior to said injection;
• said means for activating including a body comprising material that is catalyzing to ammonia to decompose ammonia, said body lying in said stream of exhaust gasses, with said body having multiple parallel ammonia carrying passages that each have a length that lies within said stream of exhaust that is at least 10 times the average width of the passage.

In an apparatus for receiving ammonia and injecting at least components of the ammonia into a stream of exhaust gasses of an engine the improvement, comprising:

• means for activating said ammonia to decompose at least 10% of the ammonia into ammonia components prior to injecting said activated ammonia into said stream of exhaust gasses, with said means for activating being constructed to isolate said ammonia from said stream of exhaust gasses until at least 10% of the ammonia that is being injected into the stream of exhaust gasses has already been decomposed prior to said injection;
• said means for activating comprising a body having multiple ammonia-carrying passages that each has a cross-section of less than 1 mm.sup.2 and a length at least 10 times its width, and an electrically powered heater coupled to said body to heat said body.

A method for reducing nitrogen oxides in the exhaust gasses of an engine that combusts hydrocarbon in the presence of air and that produces a stream of exhaust gasses, comprising:

• passing ammonia from a source to an injector and injecting at least components of the ammonia from said injector, into said stream of exhaust gasses;
• activating said ammonia to break down at least 10% of said ammonia into components of ammonia, prior to injecting said ammonia and components into said stream of exhaust gasses and prior to allowing said ammonia to come into direct contact with said exhaust gases;
• said step of activating includes positioning a body with passage walls forming at least one elongated passage having a length at least 10 times its average diameter, so a length of said passage which is at least 10 times its average diameter lies in said stream of exhaust gases and allowing the heat of said exhaust gases to heat said passage walls, and passing said ammonia through said at least one passage prior to injecting said ammonia into said stream of exhaust gases to allow said passage walls to heat said ammonia to at least 500.degree. F.

A method for reducing nitrogen oxides in the exhaust gasses of an engine that combusts hydrocarbon in the presence of air and that produces a stream of exhaust gasses, comprising:

• passing ammonia from a source to an injector and injecting at least components of the ammonia from said injector, into said stream of exhaust gasses;
• activating said ammonia to break down at least 10% of said ammonia into components of ammonia, prior to injecting said ammonia and components into said stream of exhaust gasses and prior to allowing said ammonia to come into direct contact with said exhaust gases;
• said step of activating includes heating said ammonia in the presence of a catalyst prior to said step of injecting and prior to allowing said ammonia to come into contact with said exhaust gases.