CN109268824B - Boiler combustion control method adopting front-wall and rear-wall combustion mode - Google Patents

Boiler combustion control method adopting front-wall and rear-wall combustion mode Download PDF

Info

Publication number
CN109268824B
CN109268824B CN201811163008.4A CN201811163008A CN109268824B CN 109268824 B CN109268824 B CN 109268824B CN 201811163008 A CN201811163008 A CN 201811163008A CN 109268824 B CN109268824 B CN 109268824B
Authority
CN
China
Prior art keywords
coal
mill
fineness
inlet
boiler
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201811163008.4A
Other languages
Chinese (zh)
Other versions
CN109268824A (en
Inventor
陈辉
戴维葆
蔡培
王爱英
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Guoneng Nanjing Electric Power Test Research Co.,Ltd.
Original Assignee
Guodian Nanjing Electric Power Test Research Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Guodian Nanjing Electric Power Test Research Co Ltd filed Critical Guodian Nanjing Electric Power Test Research Co Ltd
Priority to CN201811163008.4A priority Critical patent/CN109268824B/en
Publication of CN109268824A publication Critical patent/CN109268824A/en
Application granted granted Critical
Publication of CN109268824B publication Critical patent/CN109268824B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C10/00—Fluidised bed combustion apparatus
    • F23C10/18—Details; Accessories
    • F23C10/28—Control devices specially adapted for fluidised bed, combustion apparatus

Abstract

The invention discloses a boiler combustion control method in a front-wall and rear-wall combustion mode, wherein high-ash bituminous coal is combusted in the boiler, and the fineness R90 of coal powder is controlled to be 8-15%. The control method of the invention is adopted to control the fineness of the pulverized coal of the front and rear wall combustion boilers burning high ash content bituminous coal, which can effectively reduce the fineness of the pulverized coal, reduce the carbon content of the boiler fly ash and reduce NO at the outlet of the economizerXConcentration, and improves boiler efficiency and unit economy.

Description

Boiler combustion control method adopting front-wall and rear-wall combustion mode
Technical Field
The invention relates to a control method for a front wall and rear wall combustion boiler to burn high-ash bituminous coal.
Background
The utility boiler actually operates in a state where low-nitrogen combustion, economical coal for combustion, and medium-low load operation are mutually superimposed, which causes a number of rather serious problems: the carbon content of fly ash and large slag is increased, the temperature reduction water amount is increased and the like; coking on a heating surface, high-temperature corrosion of a hearth, low-load stable combustion and other safety problems; the NOx production exceeds the standard, the ammonia injection is excessive, the preheater is blocked and the like. The technical key to solving or relieving the problems is the fineness of the pulverized coal. The specific surface area of solid particles is increased by the finer pulverized coal, each process of precipitation, ignition, stable combustion and burnout is strengthened, and the pulverized coal is beneficial to reducing carbon content of the fly ash and low-nitrogen combustion; more coke in the main combustion zone contacts oxygen more quickly, so that the generation of NOx through nitrogen-oxygen reaction is reduced, the physical probability and chemical kinetic energy for converting the NOx into N2 are enhanced, namely, anoxic combustion under the condition of constant excess air coefficient is further realized, and the reduction of NOx is facilitated; the pulverized coal particles have smaller inertia, the intensity of pyrolysis and combustion of the rotary flue gas thrown to the boundary is weakened, the reductive atmosphere of the wall surface of the hearth is improved, and the high-temperature corrosion is favorably reduced. The research on the reasonable selection of the fineness of the pulverized coal has practical value for solving the problems of combustion.
Disclosure of Invention
The invention aims to solve the defects in the prior art and provide a method for guiding a front-wall and rear-wall combustion boiler to adjust the fineness of pulverized coal when high-ash bituminous coal is used, so that the fineness of the pulverized coal is reduced, the carbon content of boiler fly ash is reduced, and NO at an outlet of an economizer is reducedXConcentration, and improves boiler efficiency and unit economy.
In order to achieve the above object, the present invention provides a combustion control method for a front and rear wall combustion type boiler, which combusts high ash bituminous coal and controls the fineness of pulverized coal R90 to be 8% to 15%, preferably 10.8% to 11.3%.
The specific guiding steps are as follows:
the first step is as follows: under the low-nitrogen combustion state of the boiler, the proportion of over-fire air, the running oxygen amount, the running number of coal mills and the like are kept unchanged, and the influence of different coal powder fineness on the combustion of the boiler is analyzed through numerical simulation.
The second step is that: and carrying out field test research according to the numerical simulation result of the first step, keeping the over-fire air ratio, the secondary air distribution mode, the running oxygen amount, the number of running coal mills and the like unchanged in the low-nitrogen combustion state of the boiler, and analyzing the influence of different coal powder fineness on the combustion of the boiler through tests.
The third step: and determining the optimal coal powder fineness control value according to the numerical simulation and experimental research results.
The optimal pulverized coal fineness control value of the high-ash bituminous coal for combustion of the front-wall and rear-wall combustion boilers can be determined through the adjustment, the carbon content of the bituminous coal and the NOx concentration at the outlet of the economizer are reduced, and the boiler efficiency and the unit economy are improved.
More specifically:
(1) in a low-nitrogen combustion state of the boiler, loads of 330MW and 165MW of a unit are kept unchanged, the proportion (30%) of over-fire air, the running oxygen amount (3.6% -3.75% in the case of 330MW load and 4.5% -4.75% in the case of 165MW load), the running number of coal mills (ABCD mill in the case of 330MW load and ABD mill in the case of 165MW load) and the like are kept unchanged, and the influence of different coal powder fineness on the combustion of the boiler is analyzed through numerical simulation. Numerical simulation calculation of coal powder fineness R90 of 23%, 15%, 11% and 8% is carried out by using FLUENT numerical simulation software to suggest a model and grid division;
(2) according to the numerical simulation result of the first step, field test research is carried out, the proportion (30%) of over-fired air, the running oxygen amount (3.6% -3.75% under 330MW load and 4.5% -4.75% under 165MW load), the running number of coal mills (ABCD mill under 330MW load and ABD mill under 165MW load) and the like are maintained unchanged under the low-nitrogen combustion state of the boiler, and the influence of different coal powder fineness on the combustion of the boiler is analyzed through tests.
The control method for the fineness of the high-ash bituminous coal powder finally used for the front-wall and rear-wall combustion boilers and obtained according to the guiding steps comprises the following steps:
in a low-nitrogen combustion state of the boiler, the proportion (30%) of over-fire air, the running oxygen amount (3.6% -3.75% under 330MW load and 4.5% -4.75% under 165MW load), the running number of coal mills (ABCD mill under 330MW load and ABD mill under 165MW load) and the like are maintained unchanged, and the influence of different coal powder fineness on the boiler combustion is analyzed through tests:
at 330MW load, the grinding output of A is 45t/h, the loading force is 10MPa, the primary air pressure of a grinding inlet is 6.1kPa, the air temperature of the grinding inlet is 266 ℃, the opening of hot air is 100%, the opening of cold air door is 0%, the frequency of a dynamic separator is 25Hz, the differential pressure of an inlet and an outlet of a coal mill is 4.7kPa, and the fineness R90 of coal powder is 11%. B, mill output 42t/h, loading force 10MPa, mill inlet primary air pressure 6.1kPa, mill inlet air temperature 266 ℃, hot air opening 100%, cold air opening 0%, dynamic separator frequency 25Hz, coal mill inlet and outlet differential pressure 4.8kPa, and coal dust fineness R90 is 11.3%. C, mill output force of 48t/h, loading force of 10.5MPa, mill inlet primary air pressure of 6.1kPa, mill inlet air temperature of 264 ℃, hot air opening of 100%, cold air opening of 0%, dynamic separator frequency of 27Hz, coal mill inlet and outlet differential pressure of 4.7kPa, and coal powder fineness R90 of 11.3%.
At 165MW load, the grinding output A is 48t/h, the loading force is 10.5MPa, the primary air pressure at the grinding inlet is 6.2kPa, the air temperature at the grinding inlet is 268 ℃, the opening degree of hot air is 100%, the opening degree of cold air door is 0%, the frequency of a dynamic separator is 28Hz, the differential pressure at the inlet and the outlet of a coal grinding mill is 4.8kPa, and the fineness R90 of coal powder is 10.8%. B, mill output force is 46t/h, loading force is 10.5MPa, mill inlet primary air pressure is 6.2kPa, mill inlet air temperature is 270 ℃, hot air opening is 100%, cold air opening is 0%, dynamic separator frequency is 28Hz, coal mill inlet and outlet differential pressure is 4.8kPa, and coal powder fineness R90 is 11.2%.
Compared with the prior art, the invention has the following advantages:
the control method of the invention is adopted to control the fineness of the pulverized coal of the front and rear wall combustion boilers burning high ash content bituminous coal, which can effectively reduce the fineness of the pulverized coal, reduce the carbon content of the boiler fly ash and reduce NO at the outlet of the economizerXConcentration, and improves boiler efficiency and unit economy.
Drawings
FIG. 1 is a three-dimensional and grid diagram of numerical simulation of a No. 1 furnace of a national calcium carbide zui mountain power plant according to the present invention;
FIG. 2 is a comparison graph of hearth temperature field distribution under different pulverized coal fineness of 330MW load;
FIG. 3 is a comparison graph of the distribution of the volatile components at the nozzle of the burner under different coal powder fineness of 330MW load;
FIG. 4 is a comparison graph of the CO concentration distribution in a hearth under different coal powder fineness of 330MW load;
FIG. 5 shows NO in a hearth under different 330MW loads and different coal powder finenessxA concentration profile comparison plot;
FIG. 6 is a comparison graph of the residence time of coal dust in a hearth under different coal dust fineness of 330MW load;
FIG. 7 is a comparison graph of hearth temperature field distribution under different pulverized coal fineness of 165MW load;
FIG. 8 is a comparison graph of burner nozzle volatile component distribution under different coal powder fineness of 165MW load;
FIG. 9 is a comparison graph of the CO concentration distribution in the hearth under different coal powder fineness of 165MW load;
FIG. 10 shows NO in hearth under different coal powder fineness of 165MW loadxA concentration profile comparison plot;
FIG. 11 is a graph comparing the residence time of coal fines in a furnace at different coal fines fineness under 165MW load.
Detailed Description
The present invention will be described in detail with reference to specific examples.
The embodiment of the invention relates to a subcritical natural circulation drum boiler produced and manufactured by Wuhan boiler factory, wherein the model number of the national calcium carbide Yaoshan Power Generation Co., Ltd.1 # boiler is WGZ 1004-18.4-2. The boiler adopts the intermediate speed to grind and directly blows powder process system, and the afterbody is two flues, and the superheated steam temperature is adjusted to the gas baffle, and the superheated steam temperature is adjusted to the water spray desuperheating, and middle once is reheat, balanced ventilation, three fens storehouse capacitance gram formula air heater, the continuous solid state row sediment of scraper blade dragveyer, all steel framework, the structure of suspending, for close-fitting closed island formula arrangement above the boiler operation layer, use high ash content bituminous coal.
18 double-air-regulation axial cyclone burners are arranged on the front wall of the hearth in three layers, 6 double-air-regulation axial cyclone burners are arranged on the rear wall, A, B, C layers of six front walls on each layer are sequentially arranged from bottom to top, the D layer of the rear wall is arranged opposite to the A layer, four MPS225 medium-speed coal mills correspond to each other, and each mill is provided with an electronic weighing belt type coal feeder. In actual operation, only ABC3 mills run with pulverized coal, and the D mill runs without pulverized coal only by cooling with central wind. The main design parameters of the boiler are shown in table 1.
The main design parameters of the boiler are shown in table 1 below.
TABLE 1 boiler main parameter table (design coal type)
Figure BDA0001820429150000031
Figure BDA0001820429150000041
In the numerical simulation and experimental research of the control method for the fineness of the high-ash bituminous coal powder for the front-wall and rear-wall combustion boilers, the coal type is designed for a power plant and is shown in the table 2.
TABLE 2 boiler design coal data
Figure BDA0001820429150000042
Example 1(330MW load)
The coal mill specifically put into operation in this example was an ABCD4 coal mill.
The method for controlling the fineness of the high-ash bituminous coal powder for the boiler in the front-wall and rear-wall combustion mode comprises the following specific steps:
(1) in a low-nitrogen combustion state of the boiler, the load of a unit is kept unchanged at 330MW, the proportion of over-fire air (30%), the running oxygen (3.6% -3.75%), the running number of coal mills (ABCD mill) and the like are kept unchanged, and the influence of different coal powder fineness on the combustion of the boiler is analyzed through numerical simulation. Numerical simulation calculation of coal powder fineness R90 of 23%, 15%, 11% and 8% is carried out by using FLUENT numerical simulation software to suggest a model and grid division;
(2) according to the numerical simulation result of the first step, field test research is carried out, the proportion of over-fire air (30%), the running oxygen (3.6% -3.75% under 330MW load), the running number of coal mills (ABCD grinding under 330MW load) and the like are kept unchanged under the low-nitrogen combustion state of the boiler, and the influence of different coal powder fineness on the boiler combustion is analyzed through tests.
At 330MW load, the grinding output of A is 45t/h, the loading force is 10MPa, the primary air pressure of a grinding inlet is 6.1kPa, the air temperature of the grinding inlet is 266 ℃, the opening degree of hot air is 100%, the opening degree of cold air door is 0%, the frequency of dynamic separator is 15Hz, 20Hz, 25Hz and 28Hz, the differential pressure of an inlet and an outlet of a coal grinding machine is 4.0kPa, 4.3kPa, 4.7kPa and 4.9kPa, and the fineness R90 of coal powder is respectively (23.4%, 15.5%, 11% and 8.2%). B, mill output 42t/h, loading force 10MPa, mill inlet primary air pressure 6.1kPa, mill inlet air temperature 266 ℃, hot air opening 100%, cold air door opening 0%, dynamic separator frequency (15Hz, 19Hz, 25Hz, 29Hz), coal mill inlet and outlet differential pressure (4.2kPa, 4.5kPa, 4.8kPa, 5.0kPa), and coal powder fineness R90 is (23.1%, 15.0%, 11.3%, 8.3%). C mill output force is 48t/h, loading force is 10.5MPa, mill inlet primary air pressure is 6.1kPa, mill inlet air temperature is 264 ℃, hot air opening is 100%, cold air opening is 0%, dynamic separator frequency (17Hz, 21Hz, 27Hz, 30Hz), coal mill inlet and outlet differential pressure (4.0kPa, 4.5kPa, 4.7kPa, 5.0kPa), and coal dust fineness R90 is (23.2%, 15.2%, 11.3%, 8.0%).
(3) By combining numerical simulation and experimental research, the optimal control value of the fineness (R90) of the coal powder of the burning high-ash bituminous coal is about 11% when the front and rear wall combustion mode is in a low-nitrogen combustion state of the boiler.
1. Numerical simulation analysis process and results
The simulation is carried out by modeling and simulating the whole furnace. FIG. 1 shows the gridding of a boiler model, wherein the gridding of each burner position in the main combustion area is encrypted in order to reflect the combustion condition of the main combustion area more accurately.
The simulation mainly researches the center of combustion flame and the temperature change of the hearth before and after the transformation, so that the heat absorption condition of the heating surface is not studied in detail in the simulation.
Under 330MW load, the ABCD mill runs, and only the ABC mill carries pulverized coal and the D mill carries out cooling operation only by central air without pulverized coal in actual running after the low-nitrogen combustor is transformed. After the low-nitrogen combustion of the boiler is improved, the proportion of over-fire air is maintained to be about 30%, the secondary air distribution mode, the running oxygen amount, the number of running coal mills and the like are kept unchanged, the fineness of the coal powder is changed (R90 is 23%, 15%, 11% and 8% respectively), and the influence of the change of the fineness of the coal powder on the combustion is analyzed. Wherein 23% of R90 is calculated according to a calculation formula recommended in DL/T5145-2012 in design and calculation technical Specification of powder making systems of thermal power plants of 2012 edition, and R90 is 0.5nVdafWherein n is the coal powder uniformity index, VdafIs the dry ash-free base volatile component of the coal. The numerical simulation conditions are shown in Table 3. The simulation results are shown in table 4, fig. 2-6.
Numerical simulation working condition of different coal powder fineness under table 3330 MW
Figure BDA0001820429150000051
Figure BDA0001820429150000061
Numerical simulation results of different coal powder fineness under table 4330 MW
Figure BDA0001820429150000062
As can be seen from tables 3-4 and FIGS. 2-6, the influence of changing the fineness of the pulverized coal on combustion is obvious under the conditions of 330MW load, about 30% of over-fire air ratio and low-nitrogen combustion mode of the unit.
(1) Along with the reduction of the thinning of the coal powder, the specific surface area of the coal powder in unit mass in contact with oxygen and hot smoke in the furnace is increased, the ignition is earlier, the burnout is more thorough, the heat release is more under the condition of the same coal powder amount, and therefore the water average of the overall temperature of the hearth is slightly higher than that of the original working condition.
(2) Reducing the granularity of the coal powder is beneficial to burn out, and the carbon content of the fly ash is gradually reduced from the working condition 1 to the working condition 4. When the fineness of the coal dust is reduced from 23% to 11%, the carbon content of the fly ash is reduced from 4.41% to 1.5%, and the carbon content is reduced by about 2.9%.
(3) The reduction of the particle size of the pulverized coal is beneficial to the pulverized coal particles entering the interior of the hearth in the early stage to be separated out more quickly and thoroughly to participate in the combustion reaction, so that the concentration of the volatile components and the concentration of CO in the main combustion area of the hearth are increased along with the reduction of the particle size of the pulverized coal.
(4) Along with the reduction of the particle size of the pulverized coal, the concentration of NOx at the outlet of the hearth is gradually reduced. The NOx concentration at the outlet of the hearth under the working conditions 2, 3 and 4 is reduced by about 17.41 percent, 22.67 percent and 24.34 percent respectively compared with that under the working condition 1.
2. Test procedure and results
The total coal quantity, the running oxygen quantity, the SOFA air proportion, the output force of a coal mill, the loading force, the inlet primary air pressure and the like are kept unchanged, and 4 working conditions of the frequency of the variable-state separator are developed.
In a low-nitrogen combustion state of the boiler, the proportion (30%) of over-fired air, the running oxygen amount (3.6% -3.75% under 330MW load and 4.5% -4.75% under 165MW load), the running number of coal mills (ABCD mill under 330MW load and ABD mill under 165MW load) and the like are maintained unchanged, and the influence of different coal powder fineness on the boiler combustion is analyzed through tests.
In a low-nitrogen combustion state of the boiler, the proportion (30%) of over-fired air, the running oxygen amount (3.6% -3.75% under 330MW load and 4.5% -4.75% under 165MW load), the running number of coal mills (ABCD mill under 330MW load and ABD mill under 165MW load) and the like are maintained unchanged, and the influence of different coal powder fineness on the boiler combustion is analyzed through tests.
And testing the heat efficiency of the boiler and the power consumption of the auxiliary machine under different working conditions. The unit operation is shown in table 5. The furnace efficiency calculation parameters under various working conditions are shown in Table 6.
Running mode of rotating speed unit of separator in 5330 MW load variation state
Figure BDA0001820429150000071
Figure BDA0001820429150000081
Test result table for thermal efficiency of boiler with different load of 6330 MW and different working conditions of rotating speed of separator
Figure BDA0001820429150000082
Figure BDA0001820429150000091
3. Determining the optimum coal fines fineness
As can be seen from tables 5 to 6, the fineness of the pulverized coal is changed under the conditions of 330MW load, about 30% of over-fire air proportion and low-nitrogen combustion mode of the unit, and the influence on combustion is obvious through tests.
(1) Reducing the granularity of the coal powder is beneficial to burn out, and the carbon content of the fly ash is gradually reduced from the working condition 1 to the working condition 4. When the fineness of the coal dust is reduced from 23% to 11%, the carbon content of fly ash is reduced from 4.58% to 1.35%, the carbon content of fly ash is reduced by about 3.23%, the carbon content of large slag is reduced from 4.1% to 3%, the carbon content of large slag is reduced by 1.1%, the boiler efficiency is improved from 90.9% to 93.2%, and the boiler efficiency is improved by 2.3%.
(2) Along with the reduction of the particle size of the pulverized coal, the amount of superheated desuperheating water is gradually reduced. When the fineness of the coal dust is reduced from 23% to 11%, the amount of the superheated desuperheating water is reduced from 16t/h to 10t/h, and the reduction range is 37.5%.
(3) Along with the reduction of the particle size of the pulverized coal, the power consumption of the coal mill tends to increase. When the fineness of the coal powder is reduced from 23% to 11%, the power consumption of the coal mill is increased by 152kW.h, and the amplification is increased by about 11.7%.
(4) Along with the reduction of the particle size of the pulverized coal, the concentration of NOx at the outlet of the hearth is gradually reduced. The NOx concentration at the outlet of the hearth under the working conditions 2, 3 and 4 is respectively reduced by about 15.21 percent, 23.91 percent and 26.95 percent compared with that under the working condition 1.
Tests show that the carbon content of the numerical simulation fly ash and the carbon content of the large slag at the outlet of the economizer are different from the actual field test result under the working conditions of different coal powder fineness under the load of 330MW, which indicates that the numerical simulation is more accurate. When the fineness R90 of the coal powder is reduced from 23% to 11%, the carbon content of fly ash and large slag is reduced more, the boiler efficiency is improved by 2.3%, the nitrogen oxides are reduced, the amount of overheat desuperheating water is reduced, and the unit economy and environmental protection are obviously improved.
When the fineness of the coal powder R90 is reduced to 8%, the carbon content of fly ash is reduced to 0.85%, the carbon content of large slag is reduced to 2.4%, the boiler efficiency is improved by about 0.3% compared with that of the coal powder with the fineness of 11%, meanwhile, the power consumption of a coal mill is increased by about 200kW.h, the more the fineness of the coal powder is reduced, the larger the differential pressure of the coal mill is found in the test process, the risk also exists in the safe and stable operation of the coal mill, and when the fineness of the coal powder is reduced to 8%, the more advanced combustion of the coal powder is realized, and the risk of burning a nozzle of. Comprehensive analysis shows that when high-ash bituminous coal is combusted, the selection of about 11% of coal powder fineness R90 is reasonable.
Example 2(165MW load)
The coal mill specifically put into operation in this example was an ABD3 coal mill.
The method for controlling the fineness of the high-ash bituminous coal powder for the boiler in the front-wall and rear-wall combustion mode comprises the following specific steps:
(1) in a low-nitrogen combustion state of the boiler, 165MW load of a unit is kept unchanged, the proportion of over-fire air (30%), the running oxygen amount (4.5% -4.75%), the number of running coal mills (ABD mills) and the like are kept unchanged, and the influence of different coal powder fineness on the combustion of the boiler is analyzed through numerical simulation. Numerical simulation calculation of coal powder fineness R90 of 23%, 15%, 11% and 8% is carried out by using FLUENT numerical simulation software to suggest a model and grid division;
(2) and (3) carrying out field test research according to the numerical simulation result of the first step, keeping the proportion of over-fired air (30%), the running oxygen (4.5-4.75%), the running number of coal mills (ABD mills) and the like unchanged in the low-nitrogen combustion state of the boiler, and analyzing the influence of different coal powder fineness on the boiler combustion through tests.
At 165MW load, the grinding output A is 48t/h, the loading force is 10.5MPa, the primary air pressure at the grinding inlet is 6.2kPa, the air temperature at the grinding inlet is 268 ℃, the opening degree of hot air is 100%, the opening degree of cold air door is 0%, the frequency of a dynamic separator is 28Hz, the differential pressure at the inlet and the outlet of a coal grinding mill is 4.8kPa, and the fineness R90 of coal powder is 10.8%. B, mill output force is 46t/h, loading force is 10.5MPa, mill inlet primary air pressure is 6.2kPa, mill inlet air temperature is 270 ℃, hot air opening is 100%, cold air opening is 0%, dynamic separator frequency is 28Hz, coal mill inlet and outlet differential pressure is 4.8kPa, and coal powder fineness R90 is 11.2%.
(3) By combining numerical simulation and experimental research, the optimal control value of the fineness (R90) of the coal powder of the high-ash bituminous coal for combustion in the low-nitrogen combustion state of the boiler in the front-and-back wall combustion mode is 11%.
1. Numerical simulation analysis process and results
Under 165MW load, the ABD mill runs, and only the AB mill carries pulverized coal and the D mill does not carry the pulverized coal and only the central air is used for cooling during actual running after the low-nitrogen combustor is modified. After the low-nitrogen combustion of the boiler is improved, the proportion of over-fire air is maintained to be about 30%, the secondary air distribution mode, the running oxygen amount, the number of running coal mills and the like are kept unchanged, the fineness of the coal powder is changed (R90 is 23%, 15%, 11% and 8% respectively), and the influence of the change of the fineness of the coal powder on the combustion is analyzed. The numerical simulation conditions are shown in Table 7. The simulation results are shown in table 8, fig. 7-11.
Numerical simulation working condition of different coal powder fineness under table 7165 MW
Figure BDA0001820429150000101
Figure BDA0001820429150000111
Numerical simulation results of different coal powder fineness under table 8165 MW
Figure BDA0001820429150000112
As can be seen from tables 7 to 8 and FIGS. 7 to 11, the influence of changing the fineness of the pulverized coal on combustion is obvious under the conditions of 165MW load, about 30% of over-fire air ratio and low-nitrogen combustion mode of the unit.
(1) Along with the reduction of the thinning of the coal powder, the specific surface area of the coal powder in unit mass in contact with oxygen and hot smoke in the furnace is increased, the ignition is earlier, the burnout is more thorough, the heat release is more under the condition of the same coal powder amount, and therefore the water average of the overall temperature of the hearth is slightly higher than that of the original working condition.
(2) Reducing the granularity of the coal powder is beneficial to burn out, and the carbon content of the fly ash is gradually reduced from the working condition 5 to the working condition 8. When the fineness of the coal dust is reduced from 23% to 11%, the carbon content of the fly ash is reduced from 2.60% to 0.4%, and the carbon content is reduced by about 2.2%.
(3) The reduction of the particle size of the pulverized coal is beneficial to the pulverized coal particles entering the interior of the hearth in the early stage to be separated out more quickly and thoroughly to participate in the combustion reaction, so that the concentration of the volatile components and the concentration of CO in the main combustion area of the hearth are increased along with the reduction of the particle size of the pulverized coal.
(4) Along with the reduction of the particle size of the pulverized coal, the concentration of NOx at the outlet of the hearth is gradually reduced. The NOx concentration at the outlet of the hearth under the working conditions 6, 7 and 8 is reduced by about 16.5 percent, 24.6 percent and 30.8 percent respectively compared with that under the working condition 5.
When the power station boiler is in a deep low-nitrogen combustion state and burns high-ash bituminous coal, the change of the fineness of the coal powder causes the carbon content of fly ash of the boiler and NO at the outlet of the economizerXThe concentration, the temperature field of the hearth and the CO concentration of the hearth have obvious influence. When the fineness of the coal powder is reduced from 23% to 11%, the carbon content of the fly ash is reduced by 2.2-2.9%, and NO is discharged from an economizerXThe concentration decreases by about 25%. When the power station boiler is in a deep low-nitrogen combustion state and burns high-ash bituminous coal, the operation of the fineness of the pulverized coal is reduced as much as possible on the premise that the operation of a pulverized coal making system is safe and allowable in order to achieve the best economy and environmental protection of a unit. In order to ensure the long-term safety of a pulverizing system and the safety of a burner nozzle, the fineness R90 of the pulverized coal is controlled to be about 11 percent better when high-ash bituminous coal is combusted in a boiler at the front and rear stages through numerical simulation
2. Experimental study procedure and results
The total coal quantity, the running oxygen quantity, the SOFA air proportion, the output force of a coal mill, the loading force, the inlet primary air pressure and the like are kept unchanged, and 4 working conditions of the frequency of the variable-state separator are developed.
And testing the heat efficiency of the boiler and the power consumption of the auxiliary machine under different working conditions. The unit operation is shown in table 9. The furnace efficiency calculation parameters under each working condition are shown in the table 10.
Running mode of rotating speed unit of table 9165 MW load variable-state separator
Figure BDA0001820429150000121
TABLE 10165 MW load-different separator rotation speed working condition boiler thermal efficiency test result table
Figure BDA0001820429150000122
Figure BDA0001820429150000131
Figure BDA0001820429150000141
3. Determining the optimum coal fines fineness
As can be seen from tables 9 to 10, the fineness of the pulverized coal is changed under the conditions of 165MW load, about 30% of over-fire air proportion and low-nitrogen combustion mode of the unit, and tests show that the influence on combustion is obvious.
(1) Reducing the granularity of the coal powder is beneficial to burn out, and the carbon content of the fly ash is gradually reduced from the working condition 5 to the working condition 8. When the fineness of the coal dust is reduced from 23% to 11%, the carbon content of fly ash is reduced from 2.85% to 0.6% by about 2.25%, the carbon content of large slag is reduced from 3.8% to 2.4% by 1.4%, and the boiler efficiency is improved from 90.02% to 93.65% and is improved by 3.63%.
(2) Along with the reduction of the particle size of the pulverized coal, the amount of superheated desuperheating water is gradually reduced. When the fineness of the coal dust is reduced from 23% to 11%, the amount of the superheated desuperheating water is reduced from 9t/h to 5t/h, and the reduction range is 44.4%.
(3) Along with the reduction of the particle size of the pulverized coal, the power consumption of the coal mill tends to increase. When the fineness of the coal powder is reduced from 23% to 11%, the power consumption of the coal mill is increased by 100kW.h, and the amplification is increased by about 10%.
(4) Along with the reduction of the particle size of the pulverized coal, the concentration of NOx at the outlet of the hearth is gradually reduced. The furnace outlet NOx concentrations of the working conditions 6, 7 and 8 are respectively reduced by about 11.01%, 18.42% and 23.68% compared with the working condition 5.
Tests show that under the load of 165MW, the carbon content of the numerical simulation fly ash and the carbon oxide concentration at the outlet of the economizer are different from the actual field test result under the working conditions of different coal powder fineness, and the numerical simulation is more accurate. When the fineness R90 of the coal powder is reduced from 23% to 11%, the carbon content of fly ash and large slag is reduced more, the boiler efficiency is improved by 3.63%, the nitrogen oxides are reduced, the amount of overheat desuperheating water is reduced, and the unit economy and environmental protection are obviously improved.
When the fineness of the coal powder R90 is reduced to 8%, the carbon content of fly ash is reduced to 0.60%, the carbon content of large slag is reduced to 2.0%, the boiler efficiency is improved by about 0.06 percentage point when being compared with that of the coal powder with the fineness of 11%, meanwhile, the power consumption of a coal mill is also increased by about 200kW.h, the more the fineness of the coal powder is reduced, the larger the differential pressure of the coal mill is found in the test process, the risk also exists in the safe and stable operation of the coal mill, and when the fineness of the coal powder is reduced to 8%, the coal powder is combusted more ahead, and the risk of burning a nozzle. Comprehensive analysis shows that when high-ash bituminous coal is combusted, the selection of about 11% of coal powder fineness R90 is reasonable.

Claims (1)

1. A front and back wall combustion mode boiler combustion control method, the boiler adopts the powder making system of direct blowing of the medium speed mill, the front wall of the burner hearth is divided into three layers and arranged 18 dual air-adjusting axial cyclone burners, the back wall is arranged 6 dual air-adjusting axial cyclone burners, six front walls of each layer are A, B, C layers from bottom to top in turn, the D layer of the back wall is arranged opposite to the A layer, four MPS225 medium speed coal mills are corresponding; the method is characterized in that: the boiler is used for combusting high-ash bituminous coal, and the fineness R90 of the pulverized coal is controlled to be 10.8-11.3%;
the combustion control method comprises the following steps: under the low-nitrogen combustion state of the boiler, the load of the unit is maintained to be 330MW, the overfire air proportion is maintained to be 30%, the running oxygen amount is maintained to be 3.6% -3.75%, the ABCD grinding is not changed when the coal mills run for a plurality of times, and the running mode of the coal mills is controlled to be as follows: the grinding output force of A is 45t/h, the loading force is 10MPa, the primary air pressure of a grinding inlet is 6.1kPa, the air temperature of the grinding inlet is 266 ℃, the opening degree of hot air is 100 percent, the opening degree of cold air door is 0 percent, the frequency of a dynamic separator is 25Hz, the differential pressure of an inlet and an outlet of a coal grinding mill is 4.7kPa, and the fineness R90 of coal powder is 11 percent; b, mill output force of 42t/h, loading force of 10MPa, mill inlet primary air pressure of 6.1kPa, mill inlet air temperature of 266 ℃, hot air opening of 100 percent, cold air opening of 0 percent, dynamic separator frequency of 25Hz, coal mill inlet and outlet differential pressure of 4.8kPa, and coal powder fineness R90 of 11.3 percent; c, grinding output force of 48t/h, loading force of 10.5MPa, primary air pressure of a grinding inlet of 6.1kPa, air temperature of a grinding inlet of 264 ℃, opening degree of hot air of 100%, opening degree of cold air door of 0%, frequency of a dynamic separator of 27Hz, differential pressure of an inlet and an outlet of a coal mill of 4.7kPa, and fineness R90 of coal powder of 11.3%; d, only cooling by central wind and running without coal powder;
or in the low-nitrogen combustion state of the boiler, the load of the unit is kept unchanged at 165MW, the overfire air proportion is kept at 30%, the running oxygen amount is kept at 4.5% -4.75%, the ABD mill is unchanged when the number of the coal mills runs, and the running mode of the coal mill is controlled as follows: a, mill output force is 48t/h, loading force is 10.5MPa, mill inlet primary air pressure is 6.2kPa, mill inlet air temperature is 268 ℃, hot air opening is 100%, cold air opening is 0%, dynamic separator frequency is 28Hz, coal mill inlet and outlet differential pressure is 4.8kPa, and coal powder fineness R90 is 10.8%;
b, grinding output force is 46t/h, loading force is 10.5MPa, primary air pressure at a grinding inlet is 6.2kPa, air temperature at the grinding inlet is 270 ℃, opening degree of hot air is 100%, opening degree of cold air door is 0%, frequency of dynamic separator is 28Hz, differential pressure at inlet and outlet of coal grinding mill is 4.8kPa, and fineness R90 of coal powder is 11.2%; the D mill is cooled only by central wind and operates without pulverized coal.
CN201811163008.4A 2018-09-30 2018-09-30 Boiler combustion control method adopting front-wall and rear-wall combustion mode Active CN109268824B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201811163008.4A CN109268824B (en) 2018-09-30 2018-09-30 Boiler combustion control method adopting front-wall and rear-wall combustion mode

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201811163008.4A CN109268824B (en) 2018-09-30 2018-09-30 Boiler combustion control method adopting front-wall and rear-wall combustion mode

Publications (2)

Publication Number Publication Date
CN109268824A CN109268824A (en) 2019-01-25
CN109268824B true CN109268824B (en) 2020-06-09

Family

ID=65196430

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201811163008.4A Active CN109268824B (en) 2018-09-30 2018-09-30 Boiler combustion control method adopting front-wall and rear-wall combustion mode

Country Status (1)

Country Link
CN (1) CN109268824B (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103574633A (en) * 2013-10-23 2014-02-12 广东电网公司电力科学研究院 Method for regulating combustion of high-volatile bituminous coal for lean coal boiler
CN107355774A (en) * 2016-06-02 2017-11-17 中国大唐集团科学技术研究院有限公司 The method for reducing W type flame boiler unburned carbon in flue dust

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103574633A (en) * 2013-10-23 2014-02-12 广东电网公司电力科学研究院 Method for regulating combustion of high-volatile bituminous coal for lean coal boiler
CN107355774A (en) * 2016-06-02 2017-11-17 中国大唐集团科学技术研究院有限公司 The method for reducing W type flame boiler unburned carbon in flue dust

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
李永华、杨卧龙、常建刚、魏刚、郑立国.电站锅炉经济煤粉细度的选择与优化分析.《锅炉技术》.2011,第42卷(第4期), *
电站锅炉燃用贫煤煤粉细度计算方法;蔡培;《锅炉技术》;20180728;第29卷(第4期);第12-16页 *
电站锅炉经济煤粉细度的选择与优化分析;李永华、杨卧龙、常建刚、魏刚、郑立国;《锅炉技术》;20110728;第42卷(第4期);第34-37页 *

Also Published As

Publication number Publication date
CN109268824A (en) 2019-01-25

Similar Documents

Publication Publication Date Title
Zhang et al. Combustion stability, burnout and NOx emissions of the 300-MW down-fired boiler with bituminous coal: Load variation and low-load comparison with anthracite
Li et al. Effects of the fuel-lean coal/air flow damper opening on combustion, energy conversion and emissions in a supercritical down-fired boiler
Qiao et al. Combustion and NOx formation characteristics from a 330 MWe retrofitted anthracite-fired utility boiler with swirl burner under deeply-staged-combustion
Hou et al. Numerical simulation on co-firing ultra-low volatile carbon-based fuels with bituminous coal under oxy-fuel condition
CN109268824B (en) Boiler combustion control method adopting front-wall and rear-wall combustion mode
CN215892366U (en) Smoke circulating heating device of incinerator grate
CN109681909B (en) Combustion control method of lean coal for combustion of boiler in W-shaped flame combustion mode
Wang et al. Experimental and Numerical Study on Co-combustion Behaviors and NO x Emission Characteristics of Semi-coke and Coal in a Tangentially Fired Utility Boiler
CN104806995A (en) Method for optimizing boiler operation under condition of varied coal quality
Purnomo et al. Numerical study on in-furnace blending coal combustion characteristics in a 625 MW tangentially fired pulverized coal boiler
Wang et al. Numerical simulation of NOx emission characteristics during combustion in 350 MW supercritical cogeneration tangentially boiler
CN102734833A (en) Boiler optimization method for reducing nitrogen oxide discharge
Ma et al. Combined operation mode of sub-critical W-flame boiler and coal mill optimized numerical simulation
CN107355803B (en) Method for improving boiler efficiency of W-shaped flame boiler
CN217154224U (en) Direct-blowing pulverizing system with primary cooling fan and flue gas fan
Wang et al. Research on Nox Formation and SCR Denitration System Control by Smoke Mixing Under Low Load
Li et al. Numerical simulation and combustion analysis of coal and biomass co-combustion
Xu et al. Experimental and numerical investigation of combustion system improvement on 600MW bituminous coal boiler for burning lignite coal
Wang et al. Experimental Study on Combustion Optimization of Supercritical 600MW Quadrangle Tangential Boiler
Razali et al. Impact of tangential burner firing angle on combustion characteristics of large scale coal-fired boiler
CN202032601U (en) Device used for ignite combustion of bituminous coal boiler of middle storage bin powder producing system
Peipei et al. Influence of Recirculated Flue Gas Distribution on Combustion and NOx Formation Characteristics in S-CO2 Coal-fired Boiler
Jiang et al. Research on boiler test and combustion optimization control after low-nitrogen burner transformation
Wang et al. Numerical Simulation of Oxy-Fuel Combustion of Predrying Lignite
Wang et al. Effect of large Scale of Coal-fired Units Directly Coupled to Biomass Power Generation on some Boiler Parameters

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant
CP01 Change in the name or title of a patent holder

Address after: 210023 fairyland Road, Qixia District, Nanjing, Jiangsu Province, No. 10

Patentee after: Guoneng Nanjing Electric Power Test Research Co.,Ltd.

Address before: 210023 fairyland Road, Qixia District, Nanjing, Jiangsu Province, No. 10

Patentee before: GUODIAN NANJING ELECTRIC POWER TEST RESEARCH Co.,Ltd.

CP01 Change in the name or title of a patent holder