Method and apparatus for heating a circulating fluid in an indirect heat exchanger

1. A heater having a liquid inlet, a hot liquid outlet, a hot gas inlet and a cooled gas outlet and adapted to heat a liquid stream by heat exchange with a hot gas stream to produce a hot liquid stream and a cooled gas stream; the heater consisting essentially of:

a) a radiant/convection heat transfer first section, a first section liquid inlet, a first section liquid outlet, a first section gas inlet and a first section gas outlet adapted to cool a hot gas stream by heat exchange with a liquid stream to a temperature to produce a hot liquid stream at the first section liquid outlet and a reduced temperature gas stream at the first section gas outlet at a temperature suitable for passage through a selective catalytic reduction unit;

b) a selective catalytic reduction unit having a reduction unit inlet in fluid communication with the first section gas outlet adapted to pass the reduced temperature gas stream to a reduction unit gas outlet where the selective catalytic reduction unit is operated at a suitable temperature range from about 750 to about 550° F.;

c) a convection heat transfer section adapted to cool a hot gas by heat exchange with a liquid having a second section liquid inlet, a second section liquid outlet in fluid communication with the first section liquid inlet, a second section gas inlet in fluid communication with the reduction unit gas outlet; and,

d) a waste heat recovery section having a waste heat recovery section liquid inlet, a waste heat recovery section liquid outlet in fluid communication with the second section liquid inlet, a waste heat recovery section gas inlet in fluid communication with the second section gas outlet and a waste heat recovery section gas outlet.

2. The heater of claim 1 wherein the catalytic reduction unit is a nitrogen oxide reduction unit.

3. The heater of claim 1 wherein the hot gas stream is supplied by a fired heater.

4. The heater of claim 1 wherein the hot gas stream is an exhaust stream from a light hydrocarbon fueled turbine.

5. The heater of claim 1 wherein the liquid is water.

6. A method for producing a hot liquid stream and a cool reduced nitrogen oxide content gas stream from a hot nitrogen oxide-containing gas stream and a cool liquid stream, the method consisting essentially of:

a) passing the hot nitrogen oxide-containing stream in heat exchange contact with a heated liquid stream to produce the hot liquid stream and a reduced temperature nitrogen oxide-containing gas at a temperature suitable for treatment in a selective nitrogen oxide catalytic reduction unit;

b) passing the reduced temperature nitrogen oxide-containing gas through the selective nitrogen oxide catalytic reduction unit to produce a reduced nitrogen oxide-containing reduced temperature gas stream;

c) passing the reduced nitrogen oxide containing reduced temperature gas in heat exchange contact with a warm liquid stream to produce the heated liquid stream and a further reduced temperature reduced nitrogen oxide gas; and,

d) passing the further reduced temperature reduced nitrogen oxide gas in heat exchange with a cool liquid stream to produce the warm liquid stream and the cool reduced nitrogen oxide-containing stream.

7. The method of claim 6 wherein the liquid streams are water.

8. The method of claim 6 wherein the hot nitrogen oxide containing gas stream is an exhaust gas stream from a fired heater.

9. The method of claim 6 wherein the temperature of the hot nitrogen oxide-containing gas is from about 1000 to about 2500° F.

10. The method of claim 6 wherein the temperature of the reduced temperature nitrogen oxide-containing gas is from about 350 to about 240° F.

11. The method of claim 6 wherein the temperature of the cool reduced nitrogen oxide stream is from about 80 to about 50° F. above ambient temperature.

12. The method of claim 6 wherein the cool liquid stream is from about 70 to about 120° F.

13. The method of claim 6 wherein the temperature of the hot liquid stream is from about 180 to about 300° F.