Fluidized bed boiler and method for enhancing furnace efficiency of the same

Abstract

A method for enhancing furnace efficiency of a fluidized bed boiler is provided. The fluidized bed boiler includes a boiler body for carrying out fuel combustion in a fluidized bed thereof; a fluidized gas inlet for inputting an oxygen-containing fluidized gas into the boiler body to fluidize a boiler bed and facilitate the fuel combustion; a steam outlet for outputting a steam resulting from the fuel combustion from the boiler body; and a flue-gas exhaust for emitting a flue gas resulting from the fuel combustion from the boiler body. The method includes steps of: detecting an oxygen concentration of the flue gas; feeding a portion of the flue gas back to the fluidized gas inlet; and dynamically adjusting a flow rate of the feeding fluidized gas according to oxygen concentrations of the flue gas and the feeding fluidized gas to achieve automatic control of the fluidized bed boiler.

What is claimed is: 
     
         1 . A method for enhancing furnace efficiency of a fluidized bed boiler, the fluidized bed boiler comprising:
 a boiler body for carrying out fuel combustion in a fluidized bed thereof;   a fluidized gas inlet for inputting an oxygen-containing fluidized gas or a feeding fluidized gas into the boiler body to fluidize a boiler bed to form the fluidized bed and facilitate the fuel combustion;   a steam outlet for outputting a steam resulting from the fuel combustion from the boiler body; and   a flue-gas exhaust for emitting a flue gas resulting from the fuel combustion from the boiler body,   the method comprising steps of:   detecting an oxygen concentration of the flue gas;   feeding a portion of the flue gas back to the fluidized gas inlet to provide a recirculating flue gas which is mixed with the feeding fluidized gas to form the oxygen-containing fluidized gas; and   dynamically adjusting a flow rate of the feeding fluidized gas according to the detected oxygen concentration of the flue gas and an oxygen concentration of the feeding fluidized gas to achieve automatic control of the fluidized bed boiler.   
     
     
         2 . The method according to  claim 1 , further comprising a step of dynamically adjusting a flow rate of the recirculating flue gas. 
     
     
         3 . The method according to  claim 1 , wherein the oxygen concentration of the feeding fluidized gas is a predetermined value. 
     
     
         4 . The method according to  claim 3 , wherein the feeding fluidized gas is air. 
     
     
         5 . The method according to  claim 1 , wherein an overall flow rate of the oxygen-containing fluidized gas is a predetermined value. 
     
     
         6 . The method according to  claim 1 , wherein the flow rate of the feeding fluidized gas is calculated based on equations of:
     QT=Qa+Qf   (1)
       QO=Qa×Ca+Qf×Cf   (2)
   wherein QT is an overall flow rate of the oxygen-containing fluidized gas, Qa is the flow rate of the feeding fluidized gas, Qf is a flow rate of the recirculating flue gas, QO is overall oxygen content in the oxygen-containing fluidized gas, Ca is the oxygen concentration of the feeding fluidized gas and Cf is the oxygen concentration of the flue gas.   
     
     
         7 . A fluidized bed boiler comprising:
 a boiler body configured to carry out fuel combustion in a fluidized bed thereof;   a fluidized gas inlet device connected to the boiler body and configured to input a feeding fluidized gas into the boiler body to fluidize a boiler bed to form the fluidized bed and facilitate the fuel combustion;   a steam outlet device connected to the boiler body and configured to output a steam resulting from the fuel combustion from the boiler body;   a flue-gas exhausting device connected to the boiler body and configured to emit a flue gas resulting from the fuel combustion from the boiler body;   a flue-gas recirculating device connected between the flue-gas exhausting device and the boiler body and configured to feed a portion of the flue gas back to the boiler body to provide a recirculating flue gas, the recirculating flue gas being mixed with the feeding fluidized gas to provide an oxygen-containing fluidized gas to the boiler body; and   a detector connected to the flue-gas exhausting device and configured to detect an oxygen concentration of the flue gas to dynamically adjust a flow rate of the feeding fluidized gas.   
     
     
         8 . The fluidized bed boiler according to  claim 7 , wherein the detector is an oxygen analyzer. 
     
     
         9 . The fluidized bed boiler according to  claim 7 , further comprising a controller in communication with the detector and the fluidized gas inlet device and configured to dynamically adjust the flow rate of the feeding fluidized gas according to the oxygen concentration of the flue gas. 
     
     
         10 . The fluidized bed boiler according to  claim 9 , wherein the controller is in communication with the flue-gas recirculating device and configured to adjust a flow rate of the recirculating flue gas according to the oxygen concentration of the flue gas. 
     
     
         11 . The fluidized bed boiler according to  claim 10 , wherein the controller is a computer system. 
     
     
         12 . The fluidized bed boiler according to  claim 10 , wherein the flue-gas recirculating device comprises a blower with an inverter duty motor, the controller controlling a rotational speed of the blower to adjust the flow rate of the recirculating flue gas. 
     
     
         13 . The fluidized bed boiler according to  claim 9 , wherein the controller is a computer system. 
     
     
         14 . The fluidized bed boiler according to  claim 9 , wherein the fluidized gas inlet device comprises a blower with an inverter duty motor, the controller controlling a rotational speed of the blower to adjust the flow rate of the feeding fluidized gas.