Economical use of air preheat

Abstract

An economical heat recovery system [ 100 ] is described for use in a boiler [ 26 ] includes an air preheater [ 150 ] that receives hot flue gasses [FG 1 ] and inlet air and creates heated air [A 2 ] and incremental air [A 2 ′]. The incremental air [A 2 ′] is provided to a regenerative heat capture and transfer (RHCT) system [ 300 ] positioned to receive the incremental air [A 2 ′] from the air preheater [ 150 ]. The RHCT includes a heat exchanger [ 310 ] that preheats feed water [WF 1 ] for the boiler [ 26 ]. Since a heat exchanger [ 310 ] receives clean air as opposed to those of the prior are, it may be made more efficient with more heat exchange units in closer proximity, since there is little chance of blockage. Also, there is less maintenance with the present invention.

1 . An economical flue gas heat recovery system for use with a boiler [ 26 ] comprising:
 a regenerative heat capture and transfer (RHCT) system [ 300 ] configured to receive a heated air stream [A 2 ′] from an air preheater [ 50 ], to receive a water feed [WF 1 ] from a water supply [ 65 ], to transfer heat from the heated air stream [A 2 ′] to the water feed [WF 1 ] to create a heated water supply feed, and to output a heated water supply feed [WF 2 ] to a boiler [ 26 ].   
     
     
         2 . The system of  claim 1  wherein the RHCT system [ 300 ] comprises a heat exchanger  310  configured to receive the water feed WF 1  and the heated air stream A 2 ′. 
     
     
         3 . The system of  claim 2  wherein the heat exchanger [ 310 ] is further configured to transfer heat from the incremental air stream [A 2 ′] to the water supply feed WF 1 . 
     
     
         4 . The system of  claim 2  further comprising an air preheater  150  configured to provide the incremental air stream [A 2 ′] to the RHCT system  300 . 
     
     
         5 . The system of  claim 4  wherein the air preheater  150  is configured to receive flue gases [FG 1 ] from said boiler [ 26 ] and to transfer heat from the flue gases [FG 1 ] to an air stream input [A 1 ]. 
     
     
         6 . The system of  claim 3  wherein the heated air stream [A 2 ′] is substantially free of post combustion particulate matter. 
     
     
         7 . The system of  claim 4  wherein the RHCT system [ 300 ] is configured to receive a portion of an input air stream [A 2 ] from the air preheater [ 150 ] as incremental air [A 2 ′] and to transfer heat from the incremental air [A 2 ′] to feed water [WF 1 ] for said boiler [ 26 ]. 
     
     
         8 . The system of  claim 7  further comprising a pump [ 340 ] for pumping feed water [WF 1 ] through the heat exchanger [ 310 ]. 
     
     
         9 . An economical heat recovery system [ 100 ] for use with a boiler [ 26 ] that boils water feed from a water supply [ 125 ] supplied to it, comprising:
 an air preheater [ 150 ] for receiving heated flue gasses [FG 1 ] produced by boiler [ 26 ], for receiving input air [A 1 ] and for creating incremental air [A 2 ′];   a regenerative heat capture and transfer (RHCT) system [ 300 ] adapted to receive the incremental air [A 2 ′], said water feed [WF 1 ], then transfer heat from the incremental air [A 2 ′] to the water feed [WF 1 ], create preheated water feed [WF 2 ] and supplied preheated water feed [WF 2 ] to boiler [ 26 ].   
     
     
         10 . The economical heat recovery system [ 100 ] of  claim 9 , wherein the RHCT system comprises:
 an heat exchanger [ 310 ] adapted to receive the incremental air [A 2 ′] from the air preheater [ 150 ], receive the water feed [WF 1 ] and transfer heat from the incremental air [A 2 ′] to water feed [WF 1 ] to create preheated water feed [WF 2 ], and   a pump coupled to said water supply [ 125 ] and to the heat exchanger [ 310 ] for pumping the feed water [WF 1 ] from water supply [ 125 ] through the heat exchanger [ 310 ] and the preheated water feed [WF 2 ] to the boiler [ 26 ].   
     
     
         11 . The economical heat recovery system [ 100 ] of  claim 9 , wherein at least some incremental air [A 2 ′] from air preheater [ 150 ] is provided to the RHCT [ 300 ]. 
     
     
         12 . The economical heat recovery system [ 100 ] of  claim 9 , wherein leakage gasses [ 360 ] from the air preheater [ 150 ] are provided to the RHCT [ 300 ]. 
     
     
         13 . The economical heat recovery system [ 100 ] of  claim 10 , wherein:
 the heat exchanger [ 310 ] is designed with tolerances that do not include additional internal space for particulate buildup.