CN114602607A - Positive pressure direct blowing type coal mill inlet air volume correction method - Google Patents

Positive pressure direct blowing type coal mill inlet air volume correction method Download PDF

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CN114602607A
CN114602607A CN202210257699.4A CN202210257699A CN114602607A CN 114602607 A CN114602607 A CN 114602607A CN 202210257699 A CN202210257699 A CN 202210257699A CN 114602607 A CN114602607 A CN 114602607A
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coal mill
coal
inlet
air volume
heat
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CN114602607B (en
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杨彬
罗雪娇
赵瑞松
虞昊天
绳冉冉
张素丽
安敬学
程金武
王礼鹏
逯朝锋
张天桦
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Zhongnan Electric Power Test and Research Institute of China Datang Group Science and Technology Research Institute Co Ltd
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Zhongnan Electric Power Test and Research Institute of China Datang Group Science and Technology Research Institute Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C15/00—Disintegrating by milling members in the form of rollers or balls co-operating with rings or discs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C23/00—Auxiliary methods or auxiliary devices or accessories specially adapted for crushing or disintegrating not provided for in preceding groups or not specially adapted to apparatus covered by a single preceding group
    • B02C23/18—Adding fluid, other than for crushing or disintegrating by fluid energy
    • B02C23/24—Passing gas through crushing or disintegrating zone
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C25/00—Control arrangements specially adapted for crushing or disintegrating

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Abstract

The invention relates to a positive pressure direct blowing type coal mill inlet air volume correction method, which adopts the technical scheme that the method comprises a coal mill inlet air volume calculation method; coal quality on-line measurement and analysis; a coal mill inlet air quantity correction method based on theoretical calculation; a correction method based on the inlet pressure of the coal mill; a coal mill resistance based correction method. The coal mill inlet air quantity calculation method calculates the coal mill inlet air quantity based on thermal balance, compares the coal mill inlet air quantity with the coal mill inlet measured air quantity, and calculates correction coefficients of the influence of air pressure and resistance on the coal mill inlet air quantity; finally, the accuracy and long-period display of the measured air volume at the inlet of the coal mill are realized, the method can be suitable for online correction of the air volumes at the inlets of medium-speed coal mills of different types, the accuracy of the air volume at the inlet of the coal mill is effectively improved, and the economical and stable operation of the coal mill is ensured.

Description

Positive pressure direct blowing type coal mill inlet air volume correction method
Technical Field
The invention relates to a method for correcting the air quantity at an inlet of a positive-pressure direct-blowing coal mill.
Background
At present, the energy conservation and consumption reduction of the coal-fired unit enter a key period, the flexibility of the thermal power unit is improved in the face of the current situation that the coal-fired unit needs to be optimized and adjusted urgently, and the energy conservation potential of the coal-fired unit is further exploited to become the key point of the adjustment of the energy strategy. Only by solving the problems of low boiler efficiency, high station service power and the like caused by mixed coal burning quality, deep peak regulation and unscientific operation parameter control and pushing the higher-level reasonable operation of a thermal power generation unit, the power generation industry can reduce energy consumption and improve environmental protection and economy.
As an important auxiliary engine system for providing qualified fuel for boiler combustion, the pulverizing system is one of key factors for realizing flexible peak shaving. The running condition of the pulverizing system has direct influence on the running of the unit, and when the boiler runs under the steady-state working condition, the running problem of the pulverizing system is not obvious generally. However, under the ultra-low load, the primary air temperature is low, and the fire extinguishing of the hearth is easily caused by the overlarge air quantity deviation. The accuracy, timeliness and reasonability of the primary air related parameter control of the powder preparation system directly influence the low-load combustion stability.
Therefore, it is necessary to conduct an intensive study on a part of pulverizing systems, and timely correct the inlet air quantity of the coal mill when the air quantity is found to be deviated according to the operating characteristics and theoretical calculation.
Disclosure of Invention
In view of the above situation, in order to overcome the defects of the prior art, the invention aims to provide a method for correcting the inlet air volume of a positive pressure direct-blowing coal mill, which can effectively solve the problems of online correction of the inlet air volume of different types of medium-speed coal mills and improvement of the accuracy of the inlet air volume of the coal mill.
The technical scheme of the invention is as follows:
a positive pressure direct-blowing coal mill inlet air quantity correction method comprises the following steps:
the method comprises the following steps: the coal quality is obtained through the rapid analysis of the coal quality of the laser-induced breakdown spectroscopy, and the operation state information and parameters of the equipment are collected through a DCS control system and are used as boundary conditions for calculating the inlet air quantity of the coal mill;
step two: calculating the inlet air quantity Q of the coal mill under a certain coal quantity through the principle of conservation of mass and heat of the coal mill1；
Step three: inlet air quantity Q of coal mill1And a display value Q of an air flow measuring point on the inlet of a coal mill of a DCS (distributed control System)mContrast, if the deviation amount>5%, correcting;
step four: determining coal mill inlet air volume correction coefficient K1Correction coefficient of air volume K1For inlet air quantity Q of coal mill1And a wind measurement point display value Q on the DCS control systemmThe ratio of (A) to (B);
step five: determining coal mill inlet wind pressure correction coefficient K2Wind pressure correction factor K2For the coal mill inlet under different static pressures, the coal mill inlet measures the air quantity QPiAnd a wind measurement point display value Q on the DCS control systemmThe ratio of (A) to (B);
step six: determining coal mill resistance correction coefficient K3Coefficient of resistance correction K3For measuring air quantity Q at the inlet of the coal mill under different coal mill resistancesDjAnd a wind measurement point display value Q on the DCS control systemmThe ratio of (A) to (B);
step seven: determining a final correction factor KACorrection coefficient K for air quantity1And an inlet wind pressure correction coefficient K2Coal mill resistance correction coefficient K3The product of the three and the original KAA ratio of values;
step eight: will finally correct the coefficient KASubstituting the DCS air volume expression into the DCS air volume expression to obtain the DCS air volume expression capable of reflecting the true value of the coal mill inlet air volume.
The coal mill generally adopts hot primary air to dry and convey coal powder, the air taken from the environment is sent to an air preheater by a primary air fan to be heated, and the heated hot air is sent to the coal mill. The hot primary air generally has a problem of large ash content due to passing through the air preheater. The coal mill can appear wearing and tearing, deposition under the effect of ash-containing primary air duct, guide plate and amount of wind measuring device, finally leads to the coal mill entry to measure the amount of wind and there is the deviation with actual amount of wind, influences the coal mill steady operation.
The invention provides a coal mill inlet air volume correction method, which comprises a coal mill inlet air volume calculation method; coal quality is measured and analyzed on line; a coal mill inlet air quantity correction method based on theoretical calculation; a correction method based on the inlet pressure of the coal mill; a coal mill resistance based correction method. The coal mill inlet air quantity calculation method calculates the coal mill inlet air quantity based on thermal balance, compares the coal mill inlet air quantity with the coal mill inlet measured air quantity, and calculates correction coefficients of the influence of air pressure and resistance on the coal mill inlet air quantity; finally, the accuracy and long-period display of the measured air quantity at the inlet of the coal mill are realized.
And calculating the inlet air quantity of the coal mill from the inlet temperature and the outlet temperature of the coal mill and the raw coal temperature, and calculating the inlet air quantity of the coal mill as a starting point of air quantity correction by balancing the input heat quantity and the output heat quantity of the coal mill. On the basis of calculating the air volume, the influence of different inlet static pressure working conditions of the coal mill on the inlet air volume is evaluated, the measured air volume of the coal mill under the different inlet static pressure working conditions is collected, and the data are analyzed to obtain a static pressure correction coefficient. The resistance of the coal mill is an important parameter influencing a flow field, so that the resistance correction is significant, the resistance correction adopts the averaging of multiple groups of data air volume under different resistances (same other conditions) to be compared with the calculated air volume at the inlet of the coal mill, and the resistance correction coefficient is obtained. The correction method combining resistance correction and inlet static pressure calculation with coal mill inlet air quantity calculation realizes multi-parameter correction of coal mill inlet air quantity, and is closer to an accurate value.
The invention provides an effective solution for the problem of distortion of the air volume at the inlet of the coal mill, the method can be suitable for online correction of the air volume at the inlet of medium-speed coal mills of different types, the accuracy of the air volume at the inlet of the coal mill is effectively improved, and the economical and stable operation of the coal mill is ensured, compared with the prior art, the method has the following advantages:
(1) the invention provides a coal mill inlet air quantity calculation method according to a heat balance theory and in combination with a design principle of a coal pulverizing system, the method can quickly obtain the coal mill inlet theoretical air quantity under the working condition only by depending on conventional parameters such as inlet and outlet temperatures, coal quality and the like of a coal mill, and compared with a conventional air quantity calibration test, the method is quicker and more convenient;
(2) the conventional correction only obtains correction coefficients under a single or a plurality of working conditions, and the change of the air volume of the coal mill under different resistances and different pressures is lacked, so that the accuracy of the air volume of the coal mill under a specific working condition is stronger, and when the air volume deviates from the working condition, the distortion phenomenon of the air volume at the inlet of the coal mill is easy to occur. According to the method, on the basis of air volume correction, the influences of static pressure at the inlet of the coal mill and resistance of the coal mill on the air volume of the coal mill are considered, and correction coefficients of the static pressure and the resistance on the air volume are obtained through linear fitting;
(3) according to the conventional correction method, when the air volume, the resistance and other parameters are corrected, a calibration test is required to obtain air volume data, the method can correct the air volume at the inlet of the coal mill in the running state of the coal mill, and the air volume data at the inlet of the coal mill is not required to be measured through the test in the whole correction process;
(4) the invention provides a coal mill inlet air volume correction judgment method which can judge whether correction is carried out or not by judging the deviation of theoretical air volume and measured air volume, and meanwhile, the coal mill inlet air volume is corrected by adopting multiple parameters, so that the accuracy of measured air volume is improved.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
FIG. 2 is a coal quality analysis diagram of an application example of the present invention.
Detailed Description
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
As shown in fig. 1, the method for correcting the inlet air volume of the positive pressure direct-blowing coal mill of the invention comprises the following steps:
the method comprises the following steps: the coal quality is obtained through the rapid analysis of the coal quality of the laser-induced breakdown spectroscopy, and the operation state information and parameters of the equipment are collected through a DCS control system and are used as boundary conditions for calculating the inlet air quantity of the coal mill;
step two: calculating the inlet air quantity Q of the coal mill under a certain coal quantity through the principle of conservation of mass and heat of the coal mill1；
Step three: inlet air quantity Q of coal mill1And a display value Q of an air flow measuring point on the inlet of a coal mill of a DCS (distributed control System)mContrast, if the deviation amount>5%, correcting;
step four: determining coal mill inlet air volume correction coefficient K1Correction coefficient of air volume K1For inlet air quantity Q of coal mill1And a wind measurement point display value Q on the DCS control systemmThe ratio of (A) to (B);
step five: determining coal mill inlet wind pressure correction coefficient K2Wind pressure correction factor K2For different static pressures P at coal mill inletsiUnder the same conditions, the inlet of the coal mill measures the air quantity QPiAnd a wind measurement point display value Q on the DCS control systemmThe ratio of (A) to (B);
step six: determining coal mill resistance correction coefficient K3Coefficient of resistance correction K3For different coal mill resistances delta PsjUnder the same conditions, the inlet of the coal mill measures the air quantity QDjAnd a wind measurement point display value Q on the DCS control systemmThe ratio of (A) to (B);
step seven: determining a final correction factor KACorrection coefficient K for air quantity1And an inlet wind pressure correction coefficient K2Coal mill resistance correction coefficient K3The product of the three and the original KAA ratio of values;
step eight: will finally correct the coefficient KASubstituting the DCS air volume expression into the DCS air volume expression to obtain the DCS air volume expression capable of reflecting the true value of the coal mill inlet air volume.
The first step is specifically as follows: fast coal quality analysis based on laser-induced breakdown spectroscopy to obtain coal quality and obtain raw coal received base moisture MarAnd as basic data for calculating the air volume of the positive pressure direct-blowing coal mill, acquiring equipment operation state information and parameters through a DCS (distributed control system) and obtaining the following information: coal feeding quantity B of coal millMInitial temperature t of drying agent after mixing of coal mill1Power consumption e of coal mill, mass flow Q of sealing air of coal millSSealing air temperature tsTemperature t of leaked cold airlaOutlet temperature t of coal mill2Temperature t of raw coalrcStatic pressure at coal mill inlet is PSi(same other conditions) coal mill inlet air quantity QPiCoal mill resistance of Δ Psj(other conditions are the same) time coal mill inlet air quantity QDjAnd the coal mill measures the air quantity Qm.
The specific method of the second step is as follows:
the positive pressure direct-blowing coal mill generally adopts primary air to heat and dry coal powder, so that the coal powder is heated to a certain temperature, and the energy utilization rate is improved. For the condition that the input medium of the whole coal mill is hot primary air, the heated substance is coal powder, and the output power and the inlet and outlet temperature of the coal mill are known, the inlet air quantity Q of the coal mill can be calculated by the equal input heat quantity and the output heat quantity of the coal mill1The input heat of the direct-blowing coal mill mainly comprises four parts of mechanical heat generated by the physical heat engine coal mill working of drying agent physical heat, cold air leakage physical heat and sealing air, and the output heat comprises heat consumed by evaporating water in raw coal, heat brought out by initiating the drying agent, heat consumed by heating fuel and equipment heat dissipation loss. Final calculation by heat balanceAnd (4) the air quantity of the inlet of the coal mill is output.
A. Calculating input heat q of coal millin
Total heat q input by coal mill for drying 1kg coalin：
qin＝qag1+qla+qs+qmac
In the formula: q. q.sag1: physical heat of the desiccant, kJ/kg;
qla: the physical heat of cold air leaks into the furnace, kJ/kg;
qs: physical heat of the sealing wind, kJ/kg;
qmac: mechanical heat generated by the coal mill during operation, kJ/kg;
(1) physical heat of drying agent qag1：
qag1＝cag1g1t1 kJ/kg
In the formula: c. Cag1: is at t1The weighted average mass specific heat of each component of the drying agent at the temperature, kJ/kg DEG C;
t1: the initial temperature of the drying agent after mixing by a coal mill is lower than DEG C;
g1: the dry dosage, kg/kg, of the coal mill inlet is calculated according to the following formula:
Figure BDA0003549425500000051
in the formula: q1: the inlet air quantity of the coal mill is kg/s;
BMcoal feeding amount of a coal mill, t/h;
(2) heat q generated by grinding partsmac：
qmac＝3.6×0.6e kJ/kg
In the formula: e is the unit power consumption of the coal mill, kW.h/t;
(3) physical heat q of sealed winds：
Figure BDA0003549425500000052
In the formula: qSThe mass flow of the sealing air is kg/s;
csthe specific heat of sealing wind is kJ/kg DEG C;
tsthe temperature of sealing air is DEG C;
(4) physical heat q of leaked cold airla：
qla＝Kle×cla×tla×g1 kJ/kg
In the formula: kle: the air leakage rate of the pulverizing system is the share of the air leakage rate of the coal mill in the drying agent amount of the inlet, and can be determined according to the specification of the coal mill;
tla: the temperature of the leaked cold air is lower than the temperature of the leaked cold air;
cla: corresponding to tlaThe specific heat capacity of the wet air, kJ/kg DEG C;
B. calculating output heat q of coal millou
Total heat q taken out and consumed by coal mill for drying 1kg of coalou：
Figure BDA0003549425500000053
In the formula: q. q.sevHeat consumed by evaporating water in the raw coal, kJ/kg;
qag2: the heat brought out by the exhaust gas drying agent is kJ/kg;
qf: heat consumed by heating fuel, kJ/kg;
q5: equipment heat dissipation loss, kJ/kg;
(1) heat q consumed by evaporating water from raw coalev：
Figure BDA0003549425500000061
In the formula: c. CH2O: steam at t2The average specific heat capacity at constant pressure at temperature, kJ/(kg. DEG C);
trc: raw coal temperature, deg.C;
t2the outlet temperature of the coal mill is DEG C;
Δ M: the amount of water evaporated by the drying agent per kg of raw coal, kg/kg, was calculated according to the following formula:
Figure BDA0003549425500000062
in the formula: marRaw coal receives base moisture,%;
Mpcmoisture content of coal dust,%;
(2) heat q brought out by the exhaust gas drying agentag2：
Figure BDA0003549425500000063
In the formula: c. Ca2: at t2Specific heat capacity of moist air, kJ/(kg. DEG C);
t2: coal mill outlet media temperature, deg.C;
(3) heat of consumption q of heating fuelf：
Figure BDA0003549425500000064
Figure BDA0003549425500000065
In the formula: c. Cdc: specific heat capacity of the dried coal, kJ/(kg. DEG C);
qunf: the heat for unfreezing the raw coal, wherein the unfreezing heat is considered when the daily average temperature is lower than 0 ℃;
ta,min: minimum daily average temperature, ° c;
ci: specific heat capacity of ice, kJ/(kg. DEG C);
Id: heat of solution of ice, kJ/kg;
trc: raw coal temperature, deg.C;
(4) equipment heat dissipation loss q5：
q5＝0.02×qin kJ/kg
C. Calculating inlet air quantity Q of coal mill1
Calculating the inlet air quantity Q of the coal mill through heat balance1:
qin＝qou
Figure BDA0003549425500000071
The third step is specifically as follows: the coal mill air volume measurement is that the dynamic pressure of the coal mill inlet is measured through a measuring device to calculate the coal mill inlet air volume and display the air volume value in a DCS (distributed control System), the air volume value is calculated in the DCS, and the correction coefficient K is used for correcting the air volume valueAAnd adjusting the deviation from the actual air volume, wherein the specific formula is as follows:
Figure BDA0003549425500000072
in the formula:
f is the area of the measured cross section, m2；
Kd is a calibration coefficient of the velocity measurement element;
rho is the density of the air flow, kg/m3；
Δ P is the measurement device differential pressure, Pa;
t is the mixed air temperature, DEG C;
ps is mill inlet static pressure, kPa;
c is the flow measurement device coefficient;
KAas total correction factor of coal mill, KAThe preset value is the original correction coefficient;
and (3) whether the air quantity at the inlet of the coal mill is corrected or not, and the condition judgment conditions are as follows:
Figure BDA0003549425500000073
and if the deviation between the calculated air volume and the DCS air volume is more than 5%, correcting.
Correcting coefficient K of inlet air volume of coal mill in step four1The calculation method comprises the following steps:
Figure BDA0003549425500000074
in the formula: q1The air quantity is the inlet air quantity of the coal mill; qmAnd displaying the value for the air flow point on the DCS control system.
And step five, correcting coefficient K of air pressure at inlet of coal mill2The calculation method comprises the following steps:
Figure BDA0003549425500000075
in the formula: qPiAt the ith working condition, the static pressure at the inlet of the coal mill is PSi(other conditions are the same) inlet air volume of the coal mill.
The resistance correction coefficient K of the coal mill in the sixth step3The calculating method comprises the following steps:
Figure BDA0003549425500000081
in the formula: qDjAt j operating mode, the resistance of the coal mill is delta PSj(other conditions are the same) coal mill inlet air flow.
The specific calculation method of the seventh step comprises the following steps:
Figure BDA0003549425500000082
the concrete calculation method of the step eight comprises the step of correcting the final coal mill inlet air volume correction coefficient KASubstituting into an air quantity calculation formula of a measurement device of the DCS:
Figure BDA0003549425500000083
and the air quantity correction of the inlet of the coal mill can be finished.
The invention obtains good technical effect through practical application, and the application is as follows:
the application example corrects the inlet air quantity of an HP863dye coal mill (a direct-blowing coal mill).
Step one, obtaining calculation parameters
The coal quality is obtained through the rapid analysis of the coal quality of the laser-induced breakdown spectroscopy, the operation state information and parameters of the equipment are collected through a DCS control system, and the calculation parameters are as follows:
serial number Item (symbol) Unit of Numerical value
1 Receiving base water Mar ％ 8.10
2 Coal feeding amount of coal mill BM t/h 36.94
3 Initial temperature of drying agent after mixing of coal mill t1 ℃ 271.67
4 Electricity consumption of coal mill e kW·h/t 7.21
5 Sealing air flow of coal mill QS kg/s 2.58
6 Temperature of sealing air ts ℃ 18.86
7 Temperature of leaked cold air tla ℃ 20.00
8 Outlet temperature of coal mill t2 ℃ 94.71
9 Temperature of raw coal trc ℃ 14.70
10 On-line air quantity of coal mill Qm t/h 43.45
Step two, calculating the inlet air quantity Q of the coal mill under a certain coal quantity through the mass and heat conservation principle of the coal mill1
a) Heat generated by grinding parts
qmac＝3.6×0.6e＝15.57
b) Physical heat of sealed wind
Figure BDA0003549425500000091
In the formula, csFor sealing specific heat of wind, t can be givensThe specific heat of air at temperature is selected.
c) Physical heat of leaked cold air
qla＝Kle×cla×tla×g1＝0
The HP863dye coal mill is a positive pressure direct-blowing coal mill, and the air leakage coefficient is KleTake 0. Corresponding to tlaSpecific heat capacity of humid air claThe air properties can be looked up.The air leakage coefficient can be selected according to the following table.
Figure BDA0003549425500000092
d) Heat consumed by evaporating water from raw coal
Figure BDA0003549425500000093
Figure BDA0003549425500000094
MpcThe selection is made according to fig. 2, and the present application example is selected to be 1.28. Steam at t2Average specific heat capacity at constant pressure cH2OLook-up steam property table, raw coal temperature trcAmbient temperature may be taken.
e) Heat consumed by heating fuel
Figure BDA0003549425500000095
Specific heat capacity c of dried coaldcThe heat q for unfreezing the raw coal can be selected according to the properties of the raw coalunfThe temperature was greater than 0 ℃ this time, and this time was calculated to be 0. If the heat quantity is calculated, the specific heat capacity c of the iceiHeat of solution with ice IdCan be obtained by directly searching the water property.
f) Coal mill inlet calculated air quantity Q1
Figure BDA0003549425500000096
Step three, the inlet air quantity Q of the coal mill is adjusted1And a wind measurement point display value Q on the DCS control systemmAnd comparing and calculating deviation.
Figure BDA0003549425500000097
This coal pulverizer DCS control system is former KAThe value was 1.023.
Figure BDA0003549425500000098
And (5) correcting the deviation amount by more than 5%.
Step four, determining an air volume correction coefficient K1。
Figure BDA0003549425500000101
Step five, determining an inlet wind pressure correction coefficient K2。
Coal mill inlet different static pressures PS(same other conditions), coal mill inlet air quantity QPiThe table below shows 5 statistical groups of data.
Serial number Item (symbol) Unit of Operating mode QP1 Operating mode QP2 Operating mode QP3 Operating mode QP4 Operating mode QP5
1 Inlet wind pressure PSi kPa 6.32 6.30 6.32 6.33 6.31
2 Measuring air quantity of coal mill QPi t/h 41.95 44.33 42.36 46.71 40.12
Figure BDA0003549425500000102
Step six, determining a resistance correction coefficient K of the coal mill3。
Delta P under different coal mill resistancesSj(same other conditions), coal mill inlet air quantity QDjThe statistical 5 data are shown in the following table.
Serial number Item (symbol) Unit of Operating mode QD1 Operating mode QD2 Operating mode QD3 Operating mode QD4 Operating mode QD5
1 Resistance of coal mill ΔPSj kPa 3.55 3.49 3.31 3.99 3.12
2 Measuring air quantity of coal mill QDj t/h 46.72 45.15 43.89 41.12 48.01
Figure BDA0003549425500000103
Step seven, determining a final correction coefficient KA。
Figure BDA0003549425500000104
Step eight, the final correction coefficient K is obtainedASubstituting DCS air volume expression.
Figure BDA0003549425500000105
And (3) verification: under 3 working conditions, the air quantity at the inlet of the coal mill is tested, and the test results are as follows
Figure BDA0003549425500000106
After the air volume is corrected, an inlet of the coal mill is tested, and the test result shows that the air volume deviation is less than 5 percent, the maximum deviation is only 2.1 percent, and the correction method is high in feasibility.

Claims (9)

1. A positive pressure direct-blowing coal mill inlet air quantity correction method is characterized by comprising the following steps:
the method comprises the following steps: the coal quality is obtained through the rapid analysis of the coal quality of the laser-induced breakdown spectroscopy, and the operation state information and parameters of the equipment are collected through a DCS control system and are used as boundary conditions for calculating the inlet air volume of the coal mill;
step two: calculating the inlet air quantity Q of the coal mill under a certain coal quantity through the principle of conservation of mass and heat of the coal mill1；
Step three: inlet air quantity Q of coal mill1And a display value Q of an air flow measuring point on the inlet of a coal mill of a DCS (distributed control System)mContrast, if the deviation amount>5%, correcting;
step four: determining coal mill inlet air volume correction coefficient K1Correction coefficient of air volume K1For inlet air quantity Q of coal mill1And a wind measurement point display value Q on the DCS control systemmThe ratio of (A) to (B);
step five: determining coal mill inlet wind pressure correction coefficient K2Wind pressure correction factor K2For the coal mill inlet under different static pressures, the coal mill inlet measures the air quantity QPiAnd a wind measurement point display value Q on the DCS control systemmThe ratio of (A) to (B);
step six: determining coal mill resistance correction coefficient K3Coefficient of resistance correction K3For measuring air quantity Q at inlet of coal mill under different coal mill resistancesDjAnd a wind measurement point display value Q on the DCS control systemmThe ratio of (A) to (B);
step seven: determining a final correction factor KACorrecting coefficient K for air volume1And an inlet wind pressure correction coefficient K2Coal mill resistance correction coefficient K3The product of the three and the original KAA ratio of values;
step eight: will finally correct the coefficient KASubstituting the DCS air volume expression into the DCS air volume expression to obtain the DCS air volume expression capable of reflecting the true value of the coal mill inlet air volume.
2. The method for correcting the inlet air volume of the positive pressure direct coal pulverizer as claimed in claim 1, wherein the first step is specifically: fast coal quality analysis based on laser-induced breakdown spectroscopy to obtain coal quality and obtain raw coal received base moisture MarAnd as basic data for calculating the air volume of the positive pressure direct-blowing coal mill, acquiring equipment running state information and parameters through a DCS (distributed control system) and obtaining the following information: coal feeding amount B of coal millMDrying agent after mixing of coal millTemperature t1Power consumption e of coal mill, mass flow Q of sealing air of coal millSSealing air temperature tsTemperature t of leaked cold airlaOutlet temperature t of coal mill2Temperature t of raw coalrcStatic pressure at coal mill inlet is PSiCoal mill inlet air quantity QPiCoal mill resistance of Δ PsjInlet air quantity Q of time coal millDjAnd the coal mill measures the air quantity Qm.
3. The method for correcting the inlet air volume of the positive pressure direct coal mill according to claim 1, wherein the specific method in the second step is as follows:
A. calculating input heat q of coal millin
Total heat q input by coal mill for drying 1kg coalin：
qin＝qag1+qla+qs+qmac
In the formula: q. q.sag1: physical heat of the desiccant, kJ/kg;
qla: the physical heat of cold air leaks into the furnace, kJ/kg;
qs: physical heat of the sealing wind, kJ/kg;
qmac: mechanical heat generated by the coal mill during operation, kJ/kg;
(1) physical heat of drying agent qag1：
qag1＝cag1g1t1 kJ/kg
In the formula: c. Cag1: is at t1The weighted average mass specific heat of each component of the drying agent at the temperature, kJ/kg DEG C;
t1: the initial temperature of the drying agent is DEG C after mixing with a coal mill;
g1: the dry dosage, kg/kg, of the coal mill inlet is calculated according to the following formula:
Figure RE-FDA0003594160160000021
in the formula: q1: coal millInlet air volume, kg/s;
BMcoal feeding amount of a coal mill, t/h;
(2) heat q generated by grinding partsmac：
qmac＝3.6×0.6e kJ/kg
In the formula: e is the unit power consumption of the coal mill, kW.h/t;
(3) physical heat q of sealed winds：
Figure RE-FDA0003594160160000022
In the formula: qSThe mass flow of the sealing wind is kg/s;
cskJ/kg DEG C for specific heat of sealing air;
tssealing air temperature, deg.C;
(4) physical heat q of leaked cold airla：
qla＝Kle×cla×tla×g1 kJ/kg
In the formula: kle: the air leakage rate of the pulverizing system is the share of the air leakage rate of the coal mill in the drying agent amount of the inlet, and can be determined according to the specification of the coal mill;
tla: the temperature of the leaked cold air is lower than the temperature of the leaked cold air;
cla: corresponding to tlaThe specific heat capacity of the wet air, kJ/kg DEG C;
B. calculating output heat q of coal millou
Total heat q taken out and consumed by coal mill for drying 1kg of coalou：
qou＝qev+qag2+qf+q5 kJ/kg
In the formula: q. q.sevHeat consumed by evaporating water in the raw coal, kJ/kg;
qag2: the heat brought out by the exhaust gas drying agent is kJ/kg;
qf: heat consumed by heating fuel, kJ/kg;
q5: is provided withThe standby heat dissipation loss is kJ/kg;
(1) heat q consumed by evaporating water from raw coalev：
Figure RE-FDA0003594160160000031
In the formula: c. CH2O: steam at t2The average specific heat capacity at constant pressure at temperature, kJ/(kg. DEG C);
trc: raw coal temperature, deg.C;
t2the outlet temperature of the coal mill is DEG C;
Δ M: the amount of water evaporated by the drying agent per kg of raw coal, kg/kg, was calculated according to the following formula:
Figure RE-FDA0003594160160000032
in the formula: marRaw coal receives base moisture,%;
Mpcwater content of coal dust,%;
(2) heat q brought out by the exhaust gas drying agentag2：
Figure RE-FDA0003594160160000033
In the formula: c. Ca2: at t2Specific heat capacity of wet air, kJ/(kg. DEG C);
t2: coal mill outlet media temperature, deg.C;
(3) heat of consumption q of heating fuelf：
Figure RE-FDA0003594160160000034
Figure RE-FDA0003594160160000035
In the formula: c. Cdc: specific heat capacity of the dried coal, kJ/(kg. DEG C);
qunf: the heat for unfreezing the raw coal, wherein the unfreezing heat is considered when the daily average temperature is lower than 0 ℃;
ta,min: minimum daily average temperature, ° c;
ci: specific heat capacity of ice, kJ/(kg. DEG C);
Id: heat of solution of ice, kJ/kg;
trc: raw coal temperature, deg.C;
(4) equipment heat dissipation loss q5：
q5＝0.02×qin kJ/kg
C. Calculating inlet air quantity Q of coal mill1
Calculating the inlet air quantity Q of the coal mill through heat balance1:
qin＝qou
Figure RE-FDA0003594160160000041
4. The positive pressure direct coal mill inlet air volume correction method of claim 1, wherein the third step comprises the following specific steps: the coal mill air volume measurement is that the dynamic pressure of the coal mill inlet is measured through a measuring device to calculate the coal mill inlet air volume and display the air volume value in a DCS (distributed control System), the air volume value is calculated in the DCS, and the correction coefficient K is used for correcting the air volume valueAAnd adjusting the deviation from the actual air volume, wherein the specific formula is as follows:
Figure RE-FDA0003594160160000042
in the formula:
f is the area of the measured cross section, m2；
Kd is a calibration coefficient of the velocity measurement element;
rho is the density of the air flow, kg/m3；
Δ P is the measurement device differential pressure, Pa;
t is the mixed air temperature, DEG C;
ps is mill inlet static pressure, kPa;
c is the flow measurement device coefficient;
KAfor the total correction factor, K, of the coal millAThe preset value is the original correction coefficient;
and (3) whether the air quantity at the inlet of the coal mill is corrected or not, and the condition judgment conditions are as follows:
Figure RE-FDA0003594160160000043
and if the deviation between the calculated air volume and the DCS air volume is more than 5%, correcting.
5. The positive pressure direct coal pulverizer inlet air volume correction method of claim 1, wherein the coal pulverizer inlet air volume correction coefficient K in the fourth step1The calculation method comprises the following steps:
Figure RE-FDA0003594160160000051
in the formula: q1The air quantity is the inlet air quantity of the coal mill; qmAnd displaying the value for the air flow point on the DCS control system.
6. The method for correcting the inlet air volume of the positive pressure direct coal mill according to claim 1, wherein the correction coefficient K of the inlet air pressure of the coal mill in the fifth step2The calculation method comprises the following steps:
Figure RE-FDA0003594160160000052
in the formula: qPiUnder the ith working condition, the static pressure at the inlet of the coal mill is PSiThe inlet air quantity of the lower coal mill.
7. The positive pressure direct coal pulverizer inlet air volume correction method of claim 1, wherein the coal pulverizer resistance correction factor K in step six is the coal pulverizer resistance correction factor K3The calculating method comprises the following steps:
Figure RE-FDA0003594160160000053
in the formula: qDjFor the jth operating mode, the coal mill resistance is Δ PSjThe inlet air quantity of the coal mill is measured.
8. The method for correcting the inlet air volume of the positive pressure direct coal mill according to claim 1, wherein the specific calculation method in the seventh step is as follows:
Figure RE-FDA0003594160160000054
9. the method for correcting the inlet air volume of the positive pressure direct coal mill according to claim 1, wherein the step eight is specifically calculated by correcting the final inlet air volume correction coefficient K of the coal millASubstituting into an air quantity calculation formula of a measurement device of the DCS:
Figure RE-FDA0003594160160000055
and the air quantity correction of the inlet of the coal mill can be finished.
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