Boiler with integrated economizer

Abstract

A boiler comprises a boiler gas exhaust providing an exhaust for recuperated gases; and a secondary heat exchanger comprising: an economizer cold fluid inlet connected to a source of cold fluid; an economizer cold fluid outlet fluidly connected to the economizer cold fluid inlet and located thereabove, the cold fluid circulating upwardly from the economizer cold fluid inlet towards the economizer cold fluid outlet; a hot gas inlet for receiving the recuperated gases from the boiler gas exhaust; and a hot gas outlet fluidly connected to the hot gas inlet through the secondary heat exchanger, the recuperated gases circulating from the hot gas inlet toward the hot gas outlet; wherein the recuperated gases cross the secondary heat exchanger and exhaust by the hot gas outlet, the cold fluid being heated between the economizer cold fluid inlet and the economizer cold fluid outlet thereby resulting in a preheated fluid.

1 . A boiler for heating a cold fluid with recuperated gases, the boiler comprising:
 a boiler gas exhaust providing an exhaust for the recuperated gases; and   a secondary heat exchanger comprising:
 an economizer cold fluid inlet connected to a source of cold fluid; 
 an economizer cold fluid outlet fluidly connected to the economizer cold fluid inlet and located thereabove, the cold fluid circulating upwardly from the economizer cold fluid inlet towards the economizer cold fluid outlet; 
 a hot gas inlet for receiving the recuperated gases from the boiler gas exhaust; and 
 a hot gas outlet fluidly connected to the hot gas inlet through the secondary heat exchanger, the recuperated gases circulating from the hot gas inlet toward the hot gas outlet; 
   
       wherein the recuperated gases cross the secondary heat exchanger and exhaust by the hot gas outlet, the cold fluid being heated between the economizer cold fluid inlet and the economizer cold fluid outlet thereby resulting in a preheated fluid. 
     
     
         2 . The boiler of  claim 1 , wherein the secondary heat exchanger comprises a secondary shell for conveying the recuperated gases from the boiler gas exhaust. 
     
     
         3 . The boiler of  claim 2 , wherein the secondary heat exchanger comprises a plurality of secondary tubes between the economizer cold fluid inlet and the economizer cold fluid outlet and within the secondary shell, the plurality of secondary tubes being fluidly connected to the source of cold fluid. 
     
     
         4 . The boiler of  claim 2 , wherein main heat exchanger comprises a main shell receiving the preheated fluid. 
     
     
         5 . The boiler of  claim 4 , wherein the main shell comprises a boiler cold fluid outlet near a bottom portion of the main shell and the source of cold fluid is connected to the boiler cold fluid outlet and whereby the cold fluid flows upwardly by natural circulation into and through the secondary heat exchanger. 
     
     
         6 . The boiler of  claim 5 , further comprising an external cold fluid inlet wherein the source of cold fluid is also connected to external cold fluid inlet to admit cold fluid from an external source. 
     
     
         7 . The boiler of  claim 6 , further comprising a flow restrictive device located near the boiler cold fluid outlet and an external cold fluid inlet, the flow restrictive device letting the cold fluid flow from the boiler cold fluid outlet to the economizer cold fluid inlet when there is no fluid flow from the external source and, when the level of cold fluid is too low in the boiler, the cold fluid flows from the external source and the flow restrictive device will close to let the cold fluid flow from the external source through the external cold fluid inlet and further prevent the cold fluid from the external source to flow directly in the main shell. 
     
     
         8 . The boiler of  claim 4 , wherein the secondary shell is connected to or extends from the main shell. 
     
     
         9 . The boiler of  claim 4 , wherein the main shell and secondary shell form a single shell. 
     
     
         10 . The boiler of  claim 4 , wherein the main heat exchanger comprises two ends and the secondary heat exchanger is located at at least one of the two ends. 
     
     
         11 . The boiler of  claim 1 , further comprising a main heat exchanger for heating the preheated fluid, the main heat exchanger comprising the boiler gas exhaust and a burner for producing hot gases directed to the boiler gas exhaust. 
     
     
         12 . The boiler of  claim 1 , further comprising a lower header fluidly connected to the economizer cold fluid inlet. 
     
     
         13 . The boiler of  claim 12 , further comprising an upper header being fluidly connected to the economizer cold fluid outlet.