Low NOx cogeneration process and system

Claim 1

A process for low NO x cogeneration to produce electricity and useful heat, which comprises: providing fuel and oxygen to an internal combustion engine connected to drive an electric generator, to thereby generate electricity; recovering from said engine an exhaust stream at a temperature of about 500° to 1000° F. which includes from about 6 to 15% oxygen; adding to said exhaust stream sufficient fuel to create a fuel-rich mixture, the quantity of fuel being sufficient to react with the available oxygen and reduce the NO x in said exhaust stream; providing said fuel-enriched exhaust stream to a thermal reactor and reacting therein said fuel, NO x and available oxygen, to provide a heated oxygen-depleted stream; cooling said oxygen-depleted stream by passing same through a heat exchanger; adding conversion oxygen to said cooled stream from said heat exchanger, and passing the cooled oxygen-augmented stream over a first catalyst bed under overall reducing conditions, the quantity of conversion oxygen added being in stoichiometric excess of the amount of NO x , but less than the amount of combustibles; whereby the NO x is first oxidized to NO 2 , and then the NO 2 is reduced by the excess combustibles; adding air to the resulting stream from said first catalyst bed to produce a cooled stream having a stoichiometric excess of oxygen; and passing said stream over an oxidizing catalyst bed to oxidize remaining excess combustible, to thereby provide an effluent stream having environmentally safe characteristics.

Claim 15

A system for low NO x cogeneration of electricity and useful heat comprising in combination: an electrical generator; an internal combustion engine connected to drive said electrical generator to produce electricity, said internal combustion engine providing a hot gaseous exhaust stream including elevated NO x levels and unburned oxygen; means for introducing to said internal combustion exhaust stream sufficient fuel to create a fuel-rich mixture; an afterburner connected to receive the fuel-enriched exhaust stream from said engine and burn out substantially all of the said oxygen; a heat exchanger connected to receive the gaseous flow from said afterburner and cool same to provide an output stream having a temperature below 1050° F., while extracting useful heat from the input stream; means for adding controlled quantities of conversion oxygen to the cooled output stream proceeding from said heat exchanger; an overall reducing catalyst bed connected to receive the oxygen-augmented cooled air stream from said heat exchanger and pass said flow through said bed; the conversion oxygen acting upon the gaseous flow at the forward end of said bed to oxidize NO x to NO 2 , and the excess fuel present in said stream acting in the remainder of said bed to reduce the NO 2 to innocuous compounds; means to add excess oxygen to the flow proceeding from said reducing catalyst bed; and an oxidizer catalyst bed positioned and connected to receive the oxygen-enriched flow from said reducing catalyst bed and oxidize remaining combustibles therein; said catalyst bed having an outlet for the NO x -reduced and combustibles-reduced gases.

Claim 16

A system for low NO x cogeneration of electricity and useful heat comprising in combination: an electrical generator; an internal combustion engine connected to drive said electrical generator to produce electricity, said internal combustion engine providing a hot gaseous exhaust stream including elevated NO x levels and unburned oxygen; means for introducing to said internal combustion exhaust stream sufficient fuel to create a fuel-rich mixture; an afterburner connected to receive the fuel-enriched exhaust stream from said engine and burn out substantially all of the said oxygen; a heat exchanger connected to receive the gaseous flow from said afterburner and cool same to provide an output stream having a temperature below 1050° F., while extracting useful heat from the input stream; means for adding controlled quantities of conversion oxygen to the cooled output stream proceeding from said heat exchanger; an overall reducing catalyst bed connected to receive the oxygen-augmented cooled air stream from said heat exchanger and pass said flow through said bed; the conversion oxygen acting upon the gaseous flow at the forward end of said bed to oxidize NO x to NO 2 , and the excess fuel present in said stream acting in the remainder of said bed to reduce the NO 2 to innocuous compounds; means to add excess oxygen to the flow proceeding from said reducing catalyst bed; and an oxidizer catalyst bed positioned and connected to receive the oxygen-enriched flow from said reducing catalyst bed and oxidize remaining combustibles therein; said catalyst bed having an outlet for the NO x -reduced and combustibles-reduced gases.