Steam boiler system and method of circulating water and steam in a steam boiler system

Abstract

The steam boiler system comprises a steam boiler comprising a burner and a chimney for exhausting flue gases, a feedwater line for leading feedwater to said steam boiler for producing steam, a steam line leading from said steam boiler to at least one application heat exchanger for feeding steam to said application heat exchanger, said application heat exchanger for heating an application fluid, and a condensate line leading away from said application heat exchanger for recuperating condensate from said application heat exchanger. An economizer heat exchanger is provided in said chimney, wherein at least one of said condensate return line and said feedwater line circulates through said economizer heat exchanger for allowing at least one of said condensate and said feedwater to be in heat exchange relationship with the flue gases for simultaneously cooling the flue gases while heating at least one of the condensate and the feedwater.

What is claimed is: 
     
         1 . A steam boiler system comprising:
 a steam boiler comprising a burner and a chimney for exhausting flue gases;   a feedwater line for leading feedwater to said steam boiler for producing steam with said burner;   a steam line leading from said steam boiler to at least one application heat exchanger for feeding steam to said application heat exchanger, said application heat exchanger for heating an application fluid;   a condensate line leading away from said application heat exchanger for recuperating condensate from said application heat exchanger; and   a condensing economizer heat exchanger in said chimney, wherein at least one of said condensate return line and said feedwater line circulates through said condensing economizer heat exchanger for allowing at least one of said condensate and said feedwater to be in heat exchange relationship with the flue gases for simultaneously cooling and condensing the flue gases while heating at least one of the condensate and the feedwater.   
     
     
         2 . A steam boiler system as defined in  claim 1 , wherein both said condensate return line and said feedwater line circulate through respective portions of said economizer heat exchanger for allowing both said condensate and said feedwater to be in heat exchange relationship with the flue gases for simultaneously cooling the flue gases while heating both the condensate and the feedwater. 
     
     
         3 . A steam boiler system as defined in  claim 2 , wherein said condensate return line circulates downstream of said feedwater line in said chimney, said feedwater line first cooling the flue gases circulating in said chimney and said condensate line then further cooling and condensing the flues gases to improve heat transfer. 
     
     
         4 . A steam boiler system as defined in  claim 3 , wherein said condensate return line further circulates through at least one condensate heat exchanger upstream of said condensing economizer heat exchanger, for cooling the condensate before it comes in heat exchange relationship with the flue gases. 
     
     
         5 . A steam boiler system as defined in  claim 4 , wherein said at least one condensate heat exchanger comprises a combustion air heat exchanger that is located upstream of said burner for simultaneously preheating the air fed into said burner and cooling the condensate. 
     
     
         6 . A steam boiler system as defined in  claim 4 , wherein said at least one condensate heat exchanger comprises at least one heat recovery heat exchanger for simultaneously cooling the condensate and for heating a heat recovery fluid used in a heat recovery application. 
     
     
         7 . A steam boiler system as defined in  claim 3 , wherein said feedwater line further circulates through at least one feedwater heat exchanger upstream of said economizer heat exchanger, for cooling the feedwater before it comes in heat exchange relationship with the flue gases. 
     
     
         8 . A steam boiler system as defined in  claim 6 , wherein said condensate line ends in a deaerator downstream of said condensing economizer heat exchanger, and said feedwater line originates at said deaerator upstream of said economizer heat exchanger, said deaerator for removing gases from the feedwater. 
     
     
         9 . A steam boiler system as defined in  claim 8 , wherein steam is further circulated from said steam boiler to said deaerator for preheating said feedwater. 
     
     
         10 . A steam boiler system as defined in  claim 3 , wherein said application heat exchanger is a flooded heat exchanger capable of subcooling the condensate. 
     
     
         11 . A method of circulating water and steam in a steam boiler system of the type comprising:
 a steam boiler comprising a burner and a chimney;   a feedwater line;   a steam line leading from said steam boiler to at least one application heat exchanger;   a condensate return line leading out of from said application heat exchanger; and   a condensing economizer heat exchanger in said chimney;   said method comprising:
 feeding feedwater to said steam boiler through said feedwater line; 
 using said burner to generate steam from said feedwater; 
 feeding steam from said steam boiler to said application heat exchanger through said steam line; 
 retrieving condensate from said application heat exchanger in said condensate line; 
 exhausting flue gases generated by said burner through said condensing economizer heat exchanger in said chimney; and 
 circulating at least one of said condensate return line and said feedwater line through said condensing economizer heat exchanger wherein said at least one of said condensate and said feedwater is in heat exchange relationship with the flue gases for simultaneously cooling and condensing the flue gases while heating the least one of the condensate and the feedwater. 
   
     
     
         12 . A method as defined in  claim 11 , wherein both said condensate return line and said feedwater line circulate through respective portions of said economizer heat exchanger, said method comprising circulating both said condensate return line and said feedwater line through said economizer heat exchanger wherein both said condensate and said feedwater are in heat exchange relationship with the flue gases for simultaneously cooling the flue gases while heating both the condensate and the feedwater. 
     
     
         13 . A method as defined in  claim 12 , wherein said condensate return line circulates downstream of said feedwater line in said chimney, the method comprising first cooling the flue gases circulating in said chimney with said feedwater line and then further cooling and condensing the flues gases with said condensate line to improve heat transfer. 
     
     
         14 . A method as defined in  claim 13 , wherein said condensate return line further circulates through at least one condensate heat exchanger upstream of said condensing economizer heat exchanger, the method comprising cooling the condensate before it comes in heat exchange relationship with the flue gases within the condensing economizer heat exchanger. 
     
     
         15 . A method as defined in  claim 14 , wherein said at least one condensate heat exchanger comprises a combustion air heat exchanger that is located upstream of said burner, the method comprising simultaneously preheating the air fed into said burner and cooling the condensate within the combustion air heat exchanger. 
     
     
         16 . A method as defined in  claim 14 , wherein said at least one condensate heat exchanger comprises at least one heat recovery heat exchanger, the method comprising simultaneously cooling the condensate and heating a heat recovery fluid used in a heat recovery application, within the heat recovery heat exchanger. 
     
     
         17 . A method as defined in  claim 13 , wherein said feedwater line further circulates through at least one feedwater heat exchanger upstream of said economizer heat exchanger, the method comprising cooling the feedwater before it comes in heat exchange relationship with the flue gases, within the feedwater heat exchanger. 
     
     
         18 . A method as defined in  claim 16 , wherein said condensate line ends in a deaerator downstream of said economizer heat exchanger, and said feedwater line originates at said deaerator upstream of said economizer heat exchanger, the method comprising removing gases from the feedwater in the deaerator and circulating said condensate back at least in part to said steam boiler through said deaerator then through said feedwater line as feedwater. 
     
     
         19 . A method as defined in  claim 18 , further comprising circulating steam to said deaerator from said steam boiler for preheating said feedwater. 
     
     
         20 . A method as defined in  claim 13 , wherein said application heat exchanger is a flooded heat exchanger capable of subcooling the condensate.