Combustion Method and System

Abstract

A method of combustion for pulverized hydrocarbonaceous fuel includes the steps of injecting an air/fuel stream into a burner, causing a low-pressure zone; directing a flow of a high-temperature combustion gas from a combustion chamber into the low-pressure zone in the burner; mixing the high-temperature combustion gas with the injected air/fuel stream to heat the injected air/fuel stream, and injecting the heated air/fuel stream from the burner to the combustion chamber, wherein the air/fuel stream is rapidly devolatilized and combusted in a flame that has a high temperature; sensing a combustion parameter; and based on the sensed combustion parameter, controlling combustion to achieve at least one of a desired NOx reduction and a desired distance from the burner to a flame front.

1 - 48 . (canceled) 
   
   
       49 . A method of combustion for pulverized hydrocarbonaceous fuel, the method comprising:
 injecting an air/fuel stream into a burner, causing a low-pressure zone;   directing a flow of a high-temperature combustion gas from a combustion chamber into the low-pressure zone in the burner;   mixing the high-temperature combustion gas with the injected air/fuel stream to heat the injected air/fuel stream, and injecting the heated air/fuel stream from the burner to the combustion chamber, wherein the air/fuel stream is rapidly devolatilized and combusted in a flame that has a high temperature;   sensing a combustion parameter; and   based on the sensed combustion parameter, controlling combustion to achieve at least one of a desired NOx reduction and a desired distance from the burner to a flame front.   
   
   
       50 . A method according to  claim 49 , wherein the step of controlling the combustion includes controlling the pressure of the low-pressure zone. 
   
   
       51 . A method according to  claim 50 , therein the step of controlling the pressure of the low-pressure zone includes controlling a tertiary air fed into the low pressure zone to control the pressure of the low-pressure zone. 
   
   
       52 . A method according to  claim 51 , wherein a feeding pipe for feeding the tertiary air is located in the first two-third of the burner measured from its entrance for the air/fuel stream. 
   
   
       53 . A method according to  claim 49 , wherein the step of controlling the combustion includes controlling the flow rate of the high-temperature combustion gas from the combustion chamber into the low-pressure zone in the burner. 
   
   
       54 . A method according to  claim 49 , wherein the step of controlling the combustion includes controlling at least one of the flow rate and air/fuel ratio of the injected air/fuel stream. 
   
   
       55 . A method according to  claim 49 , wherein the air/fuel stream is a concentrated air/fuel stream. 
   
   
       56 . A method according to  claim 55 , wherein the concentrated stream has a weight ratio of air to fuel in the range of 0.4 to 2.2. 
   
   
       57 . A method according to  claim 55 , wherein the concentrated stream is heated to a temperature of 700° C. to 1200° C. in a distance between 250 mm and 1950 mm as measured from the entrance of the burner for the high-temperature gas. 
   
   
       58 . A method according to  claim 55 , wherein the concentrated stream has a weight ratio of air to fuel in the range of 0.7 to 1.8. 
   
   
       59 . A method according to  claim 55 , wherein the concentrated stream is injected into the burner at a speed from 10 to 60 m/s. 
   
   
       60 . A method according to  claim 55 , wherein the concentrated stream is injected into the burner at a speed from 15 to 50 m/s. 
   
   
       61 . A method according to  claim 49 , wherein a cross-sectional area of the injected air/fuel stream at the entrance to the burner is a fraction of a cross-sectional area of the burner. 
   
   
       62 . A method according to  claim 61 , wherein the cross-sectional area of the injected air/fuel stream at the entrance to the burner is less than 50% of the cross-sectional area of the burner. 
   
   
       63 . A method according to  claim 49 , wherein the fuel is at least one of coal and oil coke. 
   
   
       64 . A method according to  claim 55 , further comprising separating a primary air/fuel stream into the concentrated air/fuel stream and a diluted air/fuel stream, and feeding the diluted stream into the combustion chamber. 
   
   
       65 . A method according to  claim 64 , wherein the step of controlling the combustion includes controlling the feeding of the diluted stream into the combustion chamber. 
   
   
       66 . A method according to  claim 64 , wherein the separating of the primary air/fuel stream into the concentrated stream and the diluted stream is performed by a bent pipe. 
   
   
       67 . A method according to  claim 66 , wherein the winding angle of the bent pipe is between 60° and 120°. 
   
   
       68 . A method according to  claim 64 , wherein the primary stream contains 10% to 35% of stoichiometric air. 
   
   
       69 . A method according to  claim 49 , wherein the combustion parameter includes at least one of a pressure sensor, a temperature sensor, and a chemical sensor for sensing the content of a gas. 
   
   
       70 . A method according to  claim 49 , wherein the sensing step is performed by a sensor that is placed in the burner or combustion chamber or embedded in a wall of the burner or combustion chamber. 
   
   
       71 . A method according to  claim 49 , further comprising injecting at least one additional air and fuel stream. 
   
   
       72 . A method according to  claim 71 , further comprising heating one of the at least one additional air and fuel stream by an additional reflow of a high-temperature combustion gas from the combustion chamber. 
   
   
       73 . A method according to  claim 71 , wherein one of the at least one additional air and fuel stream is an over-fire air, wherein the over-fire air is 0 to 30% of the total air fed to the combustion chamber. 
   
   
       74 . A method according to  claim 73 , wherein the step of controlling the combustion includes controlling the feeding of the over-fire air. 
   
   
       75 . A method according to  claim 71 , wherein one of the at least one additional air and fuel stream is a secondary diluted air and fuel stream. 
   
   
       76 . A method according to  claim 75 , further comprising feeding the secondary stream to the combustion chamber adjacent to the periphery of the exit of the burner for the first air/fuel stream. 
   
   
       77 . A method according to  claim 75 , wherein the step of controlling the combustion includes controlling the feeding of the secondary stream. 
   
   
       78 . A method according to  claim 75 , wherein the secondary stream is one of a straight flow or a swirling flow. 
   
   
       79 . A method according to  claim 78 , further comprising dividing the swirling secondary stream into an inner secondary stream and an outer secondary stream. 
   
   
       80 . A method according to  claim 79 , wherein the swirling strength is between 0.1 and 2.0. 
   
   
       81 . A method according to  claim 71 , wherein the first air/fuel stream is a first concentrated air/fuel stream, and wherein one of the at least one additional air and fuel stream is a second concentrated air and fuel stream. 
   
   
       82 . A method according to  claim 81 , wherein the second concentrated air/fuel stream is heated. 
   
   
       83 . A method according to  claim 49 , wherein the step of controlling combustion includes controlling combustion to maximize NOx reduction without impermissible slagging. 
   
   
       84 . A combustion system for pulverized hydrocarbonaceous fuel, the device comprising:
 a burner that is designed to receive an air/fuel stream;   a combustion chamber that is connected to the burner to send to the burner a flow of a high-temperature combustion gas to heat the air/fuel stream, and to receive the heated air/fuel stream from the burner for combustion;   a sensor for sensing a combustion parameter; and   a controller for controlling combustion based on the sensed combustion parameter to achieve at least one of a desired NOx reduction and a desired distance from the burner to a flame front.   
   
   
       85 . A system according to  claim 84 , wherein the controller controls the pressure of the low-pressure zone. 
   
   
       86 . A system according to  claim 85 , therein the controller controls a tertiary air fed into the low pressure zone to control the pressure of the low-pressure zone. 
   
   
       87 . A system according to  claim 84 , wherein the controller controls the flow rate of the high-temperature combustion gas from the combustion chamber into the low-pressure zone in the burner. 
   
   
       88 . A system according to  claim 84 , wherein the controller controls at least one of the flow rate and air/fuel ratio of the injected air/fuel stream. 
   
   
       89 . A system according to  claim 84 , wherein the air/fuel stream is a concentrated air/fuel stream. 
   
   
       90 . A system according to  claim 84 , wherein the combustion parameter includes at least one of a pressure sensor, a temperature sensor, and a chemical sensor for sensing the content of a gas. 
   
   
       91 . A system according to  claim 84 , wherein at least one additional air and fuel stream is injected into the combustion chamber. 
   
   
       92 . A system according to  claim 91 , wherein one of the at least one additional air and fuel stream is heated by an additional reflow of a high-temperature combustion gas from the combustion chamber. 
   
   
       93 . A system according to  claim 91 , wherein one of the at least one additional air and fuel stream is a secondary diluted air and fuel stream. 
   
   
       94 . A system according to  claim 91 , wherein the first air/fuel stream is a first concentrated air/fuel stream, and wherein one of the at least one additional air and fuel stream is a second concentrated air and fuel stream. 
   
   
       95 . A system according to  claim 94 , wherein the second concentrated air/fuel stream is heated. 
   
   
       96 . A system according to  claim 84 , wherein the controller controls combustion to maximize NOx reduction without impermissible slagging.