Pulverized Coal Burning Boiler

Abstract

A pulverized coal burning boiler is provided, which reduces an air-excess ratio thereby to reduce the emission of unburned contents such as CO. The pulverized coal burning boiler includes a pulverized coal feed measuring device for measuring the feeding rates of the pulverized coal to be conveyed through coal feeding pipes, individually, and a control device for calculating the burning air feeding rates to match the pulverized coal feeding rates thereby to send a control command signal to burning air feed adjusting device, so that a burner air ratio set by a burner air ratio setting device may be kept on the basis of both the pulverized coal feeding rate, which is measured by the pulverized coal feed measuring device, and the burning air feeding rate, which is measured by the burning air feeding rate measuring device and fed to a pulverized coal burner connected to the coal feeding pipes.

1 . A pulverized coal burning boiler comprising:
 milling means which generate pulverized coal by milling supplied coal;   coal feeding pipes which are arranged in such a manner that a plurality of coal feeding pipes are connected to one milling means and through which the pulverized coal is airflow-conveyed by primary air;   pulverized coal burners which are connected to front end sides of the coal feeding pipes respectively and which have pulverized coal nozzles disposed so as to face into a furnace;   combustion air supply means which supply combustion air other than the primary air to the pulverized coal burners individually;   combustion air supply amount measuring means which measure the supply amounts of the combustion air supplied by the combustion air supply means individually;   combustion air supply amount adjusting means which adjust the supply amounts of the combustion air; and   burner air ratio setting means which set burner air ratios;   wherein pulverized coal milled and generated by the milling means is distributed to the coal feeding pipes, jetted from the pulverized coal nozzles into the furnace and burned under supply of the combustion air;   the pulverized coal burning boiler characterized in that there are provided:   pulverized coal supply amount measuring means which individually measure the supply amounts of pulverized coal conveyed through the coal feeding pipes respectively; and   air supply amount control means which calculate the supply amounts of combustion air corresponding to the supply amounts of pulverized coal based on the supply amounts of pulverized coal measured by the pulverized coal supply amount measuring means and the supply amounts of combustion air supplied to the pulverized coal burners connected to the coal feeding pipes and measured by the combustion air supply amount measuring means and send control command signals to the combustion air supply amount adjusting means so that burner air ratios set by the burner air ratio setting means can be kept.   
     
     
         2 . A pulverized coal burning boiler according to  claim 1 , characterized in that the pulverized coal supply amount measuring means are attached to the coal feeding pipes of pulverized coal burners or pulverized coal burner groups high in unburned component reducing effect in the pulverized coal burners so that the supply amounts of combustion air are adjusted individually. 
     
     
         3 . A pulverized coal burning boiler according to  claim 1 , characterized in that the pulverized coal burners are disposed as several stages for the furnace and the pulverized coal supply amount measuring means are attached to the coal feeding pipes of the pulverized coal burners except the pulverized coal burners disposed on the lower stage so that the supply amounts of combustion air are adjusted individually. 
     
     
         4 . A pulverized coal burning boiler according to  claim 1 , characterized in that the pulverized coal burners are disposed as several stages for the furnace and the pulverized coal supply amount measuring means are attached to the coal feeding pipes of the pulverized coal burners disposed on at least the uppermost stage so that the supply amounts of combustion air are adjusted individually. 
     
     
         5 . A pulverized coal burning boiler according to  claim 1 , characterized in that a plurality of the pulverized coal burners are disposed side by side to form a burner stage, a plurality of after air ports are disposed side by side on a downstream side of the burner stage in an exhaust gas flow direction,
 the amount of combustion air supplied to at least one of the pulverized coal burners is adjusted, and   the amount of combustion air supplied to an after air port near to flame formed by the pulverized coal burner is adjusted.   
     
     
         6 . A pulverized coal burning boiler according to  claim 5 , characterized in that the plurality of pulverized coal burners and the plurality of after air ports are disposed so as to be separated into a vessel front and a vessel back of a furnace,
 when the amount of combustion air supplied to the pulverized coal burners disposed in the vessel front is adjusted, the amount of combustion air supplied to the after air ports disposed in the vessel back is adjusted, and   when the amount of combustion air supplied to the pulverized coal burners disposed in the vessel back is adjusted, the amount of combustion air supplied to the after air ports disposed in the vessel front is adjusted.   
     
     
         7 . A pulverized coal burning boiler according to  claim 1 , characterized in that a plurality of after air ports are dispersively disposed on a downstream side of the pulverized coal burners in an exhaust gas flow direction, concentration distribution detection means for detecting a distribution of oxygen concentrations or CO concentrations in exhaust gas is provided in a flue on a downstream side of the after air ports in an exhaust gas flow direction, and
 while the amount of combustion air supplied to the pulverized coal burners is adjusted, the amount of combustion air supplied to the after air ports corresponding to a low oxygen concentration or high CO concentration region detected by the concentration distribution detection means is increased.   
     
     
         8 . A pulverized coal burning boiler according to  claim 5 , characterized in that the pulverized coal burners are disposed as a plurality of stages for a furnace, the pulverized coal burners to adjust the supply amount of combustion air are pulverized coal burners disposed on the uppermost stage. 
     
     
         9 . A pulverized coal burning boiler according to  claim 1 , characterized in that each of the pulverized coal supply amount measuring means has a microwave resonance pipe through which a mixed fluid of the pulverized coal and primary air circulates, and a microwave transmitter and a microwave receiver which are disposed in the microwave resonance pipe so as to be at a predetermined distance from each other along a direction of a flow of the mixed fluid, and
 the microwave transmitter transmits microwaves to the microwave receiver to measure a resonance frequency of the microwave resonance pipe to thereby measure the supply amount of the pulverized coal based on the resonance frequency.   
     
     
         10 . A pulverized coal burning boiler according to  claim 9 , characterized in that a part of each of the coal feeding pipes is used as the microwave resonance pipe. 
     
     
         11 . A pulverized coal burning boiler according to  claim 9 , characterized in that the microwave transmitter and the microwave receiver protrude into the microwave resonance pipe, and a knocking member is disposed on an upstream side of the microwave transmitter in the microwave resonance pipe to unravel a flow of the pulverized coal condensed like a string in the microwave resonance pipe. 
     
     
         12 . A pulverized coal burning boiler according to  claim 1 , characterized in that the pulverized coal supply amount measuring means has a first charge sensor and a second charge sensor which are disposed in each of the coal feeding pipes so as to be at a predetermined distance from each other along an axial direction of the coal feeding pipe, and
 movement of electrostatic charges resulting from passage of pulverized coal in the coal feeding pipe is measured by the two charge sensors so that the supply amount of pulverized coal is measured based on the movement of electrostatic charges measured by the two charge sensors.   
     
     
         13 . A pulverized coal burning boiler according to  claim 12 , characterized in that the first charge sensor and the second charge sensor are circular and fluid guiding means is provided on an upstream side of the charge sensors to collect pulverized coal and pour the collected pulverized coal into a central portion side of the coal feeding pipe to thereby reduce the amount of pulverized coal passing through an inner circumferential side of the charge sensors. 
     
     
         14 . A pulverized coal burning boiler provided with a first reheater system and a second reheater system disposed side by side so that supplied steam circulates while forked into the first and second reheater systems, characterized in that there are provided:
 reheating steam distributing amount adjusting means which adjust the amounts of steam distributed to the first and second reheater systems;   reheater outlet steam temperature measuring means which measure reheater outlet steam temperatures of the first and second reheater systems; and   reheating steam distributing amount control means which send control command signals to the reheating steam distributing amount adjusting means to eliminate the temperature difference based on a deviation between the reheater outlet steam temperatures measured by the reheater outlet steam temperature measuring means.   
     
     
         15 . A pulverized coal burning boiler comprising:
 milling means which generate pulverized coal by milling supplied coal;   coal feeding pipes which are arranged in such a manner that a plurality of coal feeding pipes are connected to one milling means and through which the pulverized coal is airflow-conveyed by primary air;   pulverized coal burners which are connected to front end sides of the coal feeding pipes respectively and which have pulverized coal nozzles disposed so as to face into a furnace;   combustion air supply means which supply combustion air other than the primary air to the pulverized coal burners individually;   combustion air supply amount measuring means which measure the supply amounts of the combustion air supplied by the combustion air supply means individually;   combustion air supply amount adjusting means which adjust the supply amounts of the combustion air;   burner air ratio setting means which set burner air ratios; and   a reheater which has a first reheater system and a second reheater system disposed side by side;   wherein pulverized coal milled and generated by the milling means is distributed to the coal feeding pipes, jetted from the pulverized coal nozzles into the furnace and burned under supply of the combustion air; and   steam from a high-pressure turbine is heated by the reheater and supplied to middle-pressure and low-pressure turbines;   the pulverized coal burning boiler characterized in that there are provided:   pulverized coal supply amount measuring means which individually measure the supply amounts of pulverized coal conveyed through the coal feeding pipes respectively;   air supply amount control means which calculate the supply amounts of combustion air corresponding to the supply amounts of pulverized coal based on the supply amounts of pulverized coal measured by the pulverized coal supply amount measuring means and the supply amounts of combustion air supplied to the pulverized coal burners connected to the coal feeding pipes and measured by the combustion air supply amount measuring means and send control command signals to the combustion air supply amount adjusting means so that burner air ratios set by the burner air ratio setting means can be kept;   reheating steam distributing amount adjusting means which adjust the amounts of steam distributed to the first and second reheater systems;   reheater outlet steam temperature measuring means which measure reheater outlet steam temperatures of the first and second reheater systems; and   reheating steam distributing amount control means which send control command signals to the reheating steam distributing amount adjusting means to eliminate the temperature difference based on a deviation between the reheater outlet steam temperatures measured by the reheater outlet steam temperature measuring means.   
     
     
         16 . A pulverized coal burning boiler according to  claim 14 , characterized in that there is provided pulverized coal supply amount deviation calculating means which calculates a deviation between the amount of pulverized coal supplied to pulverized coal burners of a group heating the first reheater system and the amount of pulverized coal supplied to pulverized coal burners of a group heating the second reheater system, and
 control command signals are output from the reheating steam distributing amount control means to the reheating steam distributing amount adjusting means based on the deviation between the reheater outlet steam temperatures measured by the reheater outlet steam temperature measuring means and the deviation between the supply amounts of pulverized coal calculated by the pulverized coal supply amount deviation calculating means.   
     
     
         17 . A pulverized coal burning boiler according to  claim 14 , characterized in that there are provided:
 reheating steam temperature deviation prediction means which has reheating steam temperature deviation prediction models and which predicts a reheating steam temperature deviation based on information exerting influence on the reheating steam temperatures; and   correction means which obtain correction signals for correcting control command signals output from the reheating steam distributing amount control means based on the reheating steam temperature deviation value predicted by the reheating steam temperature deviation prediction means.   
     
     
         18 . A pulverized coal burning boiler according to  claim 17 , characterized in that the information exerting influence on the reheating steam temperatures contains at least one piece of information selected from the group consisting of the supply amount of pulverized coal, the supply amount of water, the flow rate of spray, and the power generator output. 
     
     
         19 . A pulverized coal burning boiler provided with a first superheater system and a second superheater system disposed side by side so that supplied steam circulates while forked into the first and second superheater systems, characterized in that there are provided:
 superheating steam distributing amount adjusting means which adjust the amounts of steam distributed to the first and second superheater systems;   superheater outlet steam temperature measuring means which measure superheater outlet steam temperatures of the first and second superheater systems; and   superheating steam distributing amount control means which send control command signals to the superheating steam distributing amount adjusting means to eliminate the temperature difference based on a deviation between the superheater outlet steam temperatures measured by the superheater outlet steam temperature measuring means.   
     
     
         20 . A pulverized coal burning boiler comprising:
 milling means which generate pulverized coal by milling supplied coal;   coal feeding pipes which are arranged in such a manner that a plurality of coal feeding pipes are connected to one milling means and through which the pulverized coal is airflow-conveyed by primary air;   pulverized coal burners which are connected to front end sides of the coal feeding pipes respectively and which have pulverized coal nozzles disposed so as to face into a furnace;   combustion air supply means which supply combustion air other than the primary air to the pulverized coal burners individually;   combustion air supply amount measuring means which measure the supply amounts of the combustion air supplied by the combustion air supply means individually;   combustion air supply amount adjusting means which adjust the supply amounts of the combustion air;   burner air ratio setting means which set burner air ratios; and   a superheater which has a first superheater system and a second superheater system disposed side by side;   wherein pulverized coal milled and generated by the milling means is distributed to the coal feeding pipes, jetted from the pulverized coal nozzles into the furnace and burned under supply of the combustion air; and   steam is superheated by the superheater and supplied to a high-pressure turbine;   the pulverized coal burning boiler characterized in that there are provided:   pulverized coal supply amount measuring means which individually measure the supply amounts of pulverized coal conveyed through the coal feeding pipes respectively;   air supply amount control means which calculate the supply amounts of combustion air corresponding to the supply amounts of pulverized coal based on the supply amounts of pulverized coal measured by the pulverized coal supply amount measuring means and the supply amounts of combustion air supplied to the pulverized coal burners connected to the coal feeding pipes and measured by the combustion air supply amount measuring means and send control command signals to the combustion air supply amount adjusting means so that burner air ratios set by the burner air ratio setting means can be kept;   superheating steam distributing amount adjusting means which adjust the amounts of steam distributed to the first and second superheater systems;   superheater outlet steam temperature measuring means which measure superheater outlet steam temperatures of the first and second superheater systems; and   superheating steam distributing amount control means which send control command signals to the superheating steam distributing amount adjusting means to eliminate the temperature difference based on a deviation between the superheater outlet steam temperatures measured by the superheater outlet steam temperature measuring means.   
     
     
         21 . A pulverized coal burning boiler according to  claim 19 , characterized in that there is provided pulverized coal supply amount deviation calculating means which calculates a deviation between the amount of pulverized coal supplied to pulverized coal burners of a group heating the first superheater system and the amount of pulverized coal supplied to pulverized coal burners of a group heating the second superheater system, and
 control command signals are output from the superheating steam distributing amount control means to the superheating steam distributing amount adjusting means based on the deviation between the superheater output steam temperatures measured by the superheater outlet steam temperature measuring means and the deviation between the supply amounts of pulverized coal calculated by the pulverized coal supply amount deviation calculating means.   
     
     
         22 . A pulverized coal burning boiler according to  claim 19 , characterized in that there are provided:
 superheating steam temperature deviation prediction means which has superheating steam temperature deviation prediction models and which predicts a superheating steam temperature deviation based on information exerting influence on the superheating steam temperatures; and   correction means which obtain correction signals for correcting control command signals output from the superheating steam distributing amount control means based on the superheating steam temperature deviation value predicted by the superheating steam temperature deviation prediction means.   
     
     
         23 . A pulverized coal burning boiler according to  claim 22 , characterized in that the information exerting influence on the superheating steam temperatures contains at least one piece of information selected from the group consisting of the supply amount of pulverized coal, the supply amount of water, the flow rate of spray, and the power generator output. 
     
     
         24 . A pulverized coal burning boiler according to  claim 15 , characterized in that there is provided pulverized coal supply amount deviation calculating means which calculates a deviation between the amount of pulverized coal supplied to pulverized coal burners of a group heating the first reheater system and the amount of pulverized coal supplied to pulverized coal burners of a group heating the second reheater system, and
 control command signals are output from the reheating steam distributing amount control means to the reheating steam distributing amount adjusting means based on the deviation between the reheater outlet steam temperatures measured by the reheater outlet steam temperature measuring means and the deviation between the supply amounts of pulverized coal calculated by the pulverized coal supply amount deviation calculating means.   
     
     
         25 . A pulverized coal burning boiler according to  claim 15 , characterized in that there are provided:
 reheating steam temperature deviation prediction means which has reheating steam temperature deviation prediction models and which predicts a reheating steam temperature deviation based on information exerting influence on the reheating steam temperatures; and   correction means which obtain correction signals for correcting control command signals output from the reheating steam distributing amount control means based on the reheating steam temperature deviation value predicted by the reheating steam temperature deviation prediction means.   
     
     
         26 . A pulverized coal burning boiler according to  claim 20 , characterized in that there is provided pulverized coal supply amount deviation calculating means which calculates a deviation between the amount of pulverized coal supplied to pulverized coal burners of a group heating the first superheater system and the amount of pulverized coal supplied to pulverized coal burners of a group heating the second superheater system, and
 control command signals are output from the superheating steam distributing amount control means to the superheating steam distributing amount adjusting means based on the deviation between the superheater output steam temperatures measured by the superheater outlet steam temperature measuring means and the deviation between the supply amounts of pulverized coal calculated by the pulverized coal supply amount deviation calculating means.   
     
     
         27 . A pulverized coal burning boiler according to  claim 20 , characterized in that there are provided:
 superheating steam temperature deviation prediction means which has superheating steam temperature deviation prediction models and which predicts a superheating steam temperature deviation based on information exerting influence on the superheating steam temperatures; and   correction means which obtain correction signals for correcting control command signals output from the superheating steam distributing amount control means based on the superheating steam temperature deviation value predicted by the superheating steam temperature deviation prediction means.