CN114602607B - Positive pressure direct blowing coal mill inlet air quantity correction method - Google Patents
Positive pressure direct blowing coal mill inlet air quantity correction method Download PDFInfo
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- CN114602607B CN114602607B CN202210257699.4A CN202210257699A CN114602607B CN 114602607 B CN114602607 B CN 114602607B CN 202210257699 A CN202210257699 A CN 202210257699A CN 114602607 B CN114602607 B CN 114602607B
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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
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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
- 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
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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
- B02C25/00—Control arrangements specially adapted for crushing or disintegrating
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Abstract
The invention relates to a positive pressure direct blowing coal mill inlet air quantity correction method, which comprises the following steps of calculating the inlet air quantity of a coal mill; on-line measurement and analysis of coal quality; the inlet air quantity correction method of the coal mill based on theoretical calculation; a correction method based on coal mill inlet pressure; a correction method based on the resistance of a coal mill. The method for calculating the inlet air quantity of the coal mill calculates the inlet air quantity of the coal mill based on heat balance, compares the inlet air quantity of the coal mill with the measured air quantity of the coal mill, and calculates a correction coefficient of influence of wind pressure and resistance on the inlet air quantity of the coal mill; finally, the accuracy and long-period display of the measured air quantity of the inlet of the coal mill are realized, the method can be suitable for online correction of the air quantity of the inlet of the medium-speed coal mill in different types, the accuracy of the air quantity of the inlet of the coal mill is effectively improved, and the economical and stable operation of the coal mill is ensured.
Description
Technical Field
The invention relates to a positive pressure direct blowing coal mill inlet air quantity correction method.
Background
At present, energy conservation and consumption reduction of the coal-fired unit enter a critical period, the current situation of urgent need of optimization adjustment of the coal-fired unit is faced, the flexibility of the thermal power unit is improved, and the energy conservation potential of the coal-fired unit is further excavated to become an adjustment key point of an energy strategy. Only the problems of low boiler efficiency, higher station service and the like caused by disordered combustion coal quality, deep peak shaving, unscientific control of operation parameters are solved, the higher-level reasonable operation of the thermal generator set is promoted, and the power generation industry can reduce energy consumption, and the environmental protection performance and the economical efficiency are realized.
As an important auxiliary machine system for providing qualified fuel for boiler combustion, a pulverizing system is one of key factors for realizing flexible peak shaving. The operating condition of the pulverizing system has direct influence on the unit operation, and when the boiler operates under the steady-state working condition, the operating problem of the pulverizing system is not usually outstanding. However, under the ultralow load, the primary air temperature is low, and the fire extinguishment of a hearth is easily caused by overlarge air quantity deviation. The accuracy, timeliness and rationality of the primary air related parameter control of the pulverizing system directly affect the low-load combustion stability.
Therefore, it is very necessary to conduct intensive research on part of the pulverizing system, and timely perform inlet air quantity and correction on the coal mill when the air quantity is found to be deviated according to the operation characteristics and theoretical calculation.
Disclosure of Invention
Aiming at the situation, the invention aims to overcome the defects of the prior art, and the invention aims to provide the positive pressure direct blowing type coal mill inlet air quantity correction method which can effectively solve the problems of on-line correction of inlet air quantity of different types of medium speed coal mills and improvement of accuracy of inlet air quantity 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:
step one: the coal quality is obtained through rapid analysis of the coal quality of the laser-induced breakdown spectrum, and the DCS control system is used for collecting equipment running state information and parameters and used as boundary conditions for calculating the inlet air quantity of the coal mill;
step two: the inlet air quantity Q of the coal mill under a certain coal quantity is calculated according to the mass and heat conservation principle of the coal mill 1 ；
Step three: inlet air quantity Q of coal mill 1 And a display value Q of an air quantity measuring point on an inlet of a coal mill of a DCS control system m In contrast, if the deviation is>5, correcting;
step four: determining the correction coefficient K of the inlet air quantity of the coal mill 1 Air volume correction coefficient K 1 For coal mill inlet air quantity Q 1 And the display value Q of the air quantity measuring point on the DCS control system m Is a ratio of (2);
step five: determining a wind pressure correction coefficient K of an inlet of a coal mill 2 Wind pressure correction coefficient K 2 For different static pressures of the coal mill inlet, the air quantity Q is measured by the coal mill inlet Pi And the display value Q of the air quantity measuring point on the DCS control system m Is a ratio of (2);
step six: determining a resistance correction coefficient K of a coal mill 3 Resistance correction coefficient K 3 For different coal mill resistances, the inlet of the coal mill measures the air quantity Q Dj And the display value Q of the air quantity measuring point on the DCS control system m Is a ratio of (2);
step seven: determining a final correction coefficient K A For the air quantity correction coefficient K 1 Inlet wind pressure correction factor K 2 Resistance correction coefficient K of coal mill 3 Product of the three and original K A A ratio of values;
step eight: will finally correct coefficient K A Substituting the DCS air quantity expression to obtain the DCS air quantity expression capable of reflecting the real value of the inlet air quantity of the coal mill.
The coal mill generally adopts hot primary air to dry and convey coal dust, the hot primary air is used for sending air taken from the environment into an air preheater by a primary air fan to heat, and the heated hot air is sent into the coal mill. The hot primary air generally has a problem of high ash content because it passes through the air preheater. The air duct, the guide plate and the air quantity measuring device of the coal mill can be worn and accumulated ash under the action of the ash-containing primary air, and finally the deviation between the measured air quantity of the inlet of the coal mill and the actual air quantity is caused, so that the stable operation of the coal mill is influenced.
The invention provides a coal mill inlet air quantity correction method, which comprises a coal mill inlet air quantity calculation method; on-line measurement and analysis of coal quality; the inlet air quantity correction method of the coal mill based on theoretical calculation; a correction method based on coal mill inlet pressure; a correction method based on the resistance of a coal mill. The method for calculating the inlet air quantity of the coal mill calculates the inlet air quantity of the coal mill based on heat balance, compares the inlet air quantity of the coal mill with the measured air quantity of the coal mill, and calculates a correction coefficient of influence of wind pressure and resistance on the inlet air quantity of the coal mill; finally, the accuracy and long-period display of the measured air quantity of the coal mill inlet are realized.
The inlet air quantity of the coal mill is calculated from the inlet and outlet temperatures of the coal mill and the raw coal temperature, and the inlet air quantity of the coal mill is calculated as the starting point of air quantity correction through balancing the input heat and the output heat of the coal mill. On the basis of calculating the air quantity, the influence of the static pressure working conditions of different inlets of the coal mill on the inlet air quantity is evaluated, the measured air quantity of the coal mill under the static pressure working conditions of different inlets is collected, and the data are analyzed to obtain a static pressure correction coefficient. The resistance of the coal mill is an important parameter affecting the flow field, so that the resistance correction is of great significance, and the resistance correction adopts the comparison of the average value of multiple groups of data air volumes under different resistances (other conditions are the same) and the calculated air volume of the inlet of the coal mill to obtain a resistance correction coefficient. The correction method combining resistance correction, inlet static pressure and coal mill inlet air quantity calculation realizes multi-parameter correction of the coal mill inlet air quantity, and is closer to an accurate value.
Aiming at the problem of distortion of inlet air quantity of a coal mill, the invention provides an effective solution, and the method can be suitable for on-line correction of the inlet air quantity of different types of medium-speed coal mills, effectively improves the accuracy of the inlet air quantity of the coal mill, ensures economical and stable operation of the coal mill, and has the following advantages compared with the prior art:
(1) According to the heat balance theory and by combining with the design principle of the pulverizing system, the invention provides a coal mill inlet air quantity calculation method, which can quickly obtain the theoretical air quantity of the coal mill inlet under the working condition by only relying on conventional parameters such as inlet and outlet temperatures of the coal mill, coal quality and the like, and is more rapid and more convenient compared with a conventional air quantity calibration test;
(2) The conventional correction only obtains correction coefficients under a single or a few working conditions, and the correction coefficients lack of the change of the air quantity of the coal mill under different resistances and different pressures, so that the air quantity of the coal mill under a specific working condition is high in accuracy, and when the air quantity deviates from the working condition, the distortion phenomenon of the inlet air quantity of the coal mill is easy to occur. On the basis of air quantity correction, the method considers the influence of the static pressure of the inlet of the coal mill and the resistance of the coal mill on the air quantity of the coal mill, and obtains the correction coefficient of the static pressure and the resistance on the air quantity through linear fitting;
(3) The conventional correction method is used for acquiring air volume data by adopting a calibration test when correcting air volume, resistance and other parameters, and the method can correct the air volume of the inlet of the coal mill in the running state of the coal mill without measuring the air volume data of the inlet of the coal mill through the test in the whole correction process;
(4) The invention provides a method for judging the correction of the inlet air quantity of a coal mill, which can judge whether correction is carried out or not by judging the deviation between the theoretical air quantity and the measured air quantity, and simultaneously adopts multiple parameters to correct the inlet air quantity of the coal mill, thereby improving the accuracy of the measured air quantity.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
FIG. 2 is a graph showing the analysis of coal quality according to an embodiment of the present invention.
Detailed Description
The following describes the embodiments of the present invention in further detail with reference to the drawings.
As shown in FIG. 1, the method for correcting the inlet air quantity of the positive pressure direct blowing coal mill comprises the following steps:
step one: the coal quality is obtained through rapid analysis of the coal quality of the laser-induced breakdown spectrum, and the DCS control system is used for collecting equipment running state information and parameters and used as boundary conditions for calculating the inlet air quantity of the coal mill;
step two: the inlet air quantity Q of the coal mill under a certain coal quantity is calculated according to the mass and heat conservation principle of the coal mill 1 ；
Step three: inlet air quantity Q of coal mill 1 And a display value Q of an air quantity measuring point on an inlet of a coal mill of a DCS control system m In contrast, if the deviation is>5, correcting;
step four: determining the correction coefficient K of the inlet air quantity of the coal mill 1 Air volume correction coefficient K 1 For coal mill inlet air quantity Q 1 And the display value Q of the air quantity measuring point on the DCS control system m Is a ratio of (2);
step five: determining a wind pressure correction coefficient K of an inlet of a coal mill 2 Wind pressure correction coefficient K 2 For different static pressure P at coal mill inlet si Under (other conditions are the same), the inlet of the coal mill measures the air quantity Q Pi And the display value Q of the air quantity measuring point on the DCS control system m Is a ratio of (2);
step six: determining a resistance correction coefficient K of a coal mill 3 Resistance correction coefficient K 3 For different coal mill resistances DeltaP sj Under (other conditions are the same), the inlet of the coal mill measures the air quantity Q Dj And the display value Q of the air quantity measuring point on the DCS control system m Is a ratio of (2);
step seven: determining a final correction coefficient K A For the air quantity correction coefficient K 1 Inlet wind pressure correction factor K 2 Resistance correction coefficient K of coal mill 3 Product of the three and original K A A ratio of values;
step eight: will finally correct coefficient K A Substituting DCS windAnd the DCS air quantity expression which can reflect the real value of the air quantity of the inlet of the coal mill can be obtained by the quantitative expression.
The first step is specifically as follows: coal quality is obtained by rapid analysis of coal quality based on laser-induced breakdown spectroscopy, and raw coal is obtained to receive base moisture M ar As basic data of air volume calculation of the positive pressure direct blowing coal mill, acquiring equipment running state information and parameters through a DCS control system and obtaining the following information: coal feeding quantity B of coal mill M Initial temperature t of drying agent after mixing coal mill 1 Power consumption e of coal mill and sealing air mass flow Q of coal mill S Sealing wind temperature t s Temperature t of cold air leakage la Outlet temperature t of coal mill 2 Raw coal temperature t rc The inlet static pressure of the coal mill is P Si (other conditions are the same) coal mill inlet air quantity Q Pi Coal mill resistance ΔPs j (other conditions are the same) the inlet air quantity Q of the coal mill Dj 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, heats the coal powder to a certain temperature, and improves the energy utilization rate. The input medium of the whole coal mill is hot primary air, the heated material is coal powder, the output and inlet and outlet temperatures of the coal mill are known, and the inlet air quantity Q of the coal mill can be calculated by the equality of the input heat and the output heat of the coal mill 1 For the positive pressure direct blowing coal mill, the input heat mainly comprises four parts of drying agent physical heat, cold air leakage physical heat and mechanical heat generated by the operation of a physical heat engine coal mill with sealed air, and the output heat comprises the heat consumed by evaporating water in raw coal, the heat brought by the drying agent, the heat consumed by heating fuel and the heat dissipation loss of equipment. And finally calculating the inlet air quantity of the coal mill through thermal balance.
A. Calculating the input heat q of the coal mill in
Total heat q input by coal mill for drying 1kg coal in ：
q in ＝q ag1 +q la +q s +q mac
Wherein: q ag1 : physical heat of the desiccant, kJ/kg;
q la : physical heat leaking into cold air, kJ/kg;
q s : sealing the physical heat of wind, kJ/kg;
q mac : mechanical heat generated by the operation of the coal mill, kJ/kg;
(1) Physical heat q of desiccant ag1 ：
q ag1 ＝c ag1 g 1 t 1 kJ/kg
Wherein: c ag1 : at t 1 The weighted average mass specific heat of each component of the drying agent at the temperature, kJ/kg DEG C;
t 1 : the initial temperature of the drying agent after mixing of the coal mill is set at DEG C;
g 1 : the inlet drying dose of the coal mill, kg/kg, is calculated according to the following formula:
wherein: q (Q) 1 : inlet air quantity of the coal mill, kg/s;
B M the coal feeding amount of the coal mill is t/h;
(2) Heat q generated by milling members mac ：
q mac ＝3.6×0.6e kJ/kg
Wherein: e is the unit power consumption of the coal mill, kW.h/t;
(3) Physical heat q of seal wind s ：
Wherein: q (Q) S Kg/s for sealing the wind mass flow;
c s for sealing the specific heat of wind, kJ/kg DEG C;
t s sealing the air temperature, and the temperature is DEG C;
(4) Physical heat q of cold air leakage la ：
q la ＝K le ×c la ×t la ×g 1 kJ/kg
Wherein: k (K) le : the air leakage rate of the pulverizing system is the proportion of the air leakage rate of the coal mill to the amount of the inlet drying agent, and can be determined according to the specification of the coal mill;
t la : the temperature of the cold air is leaked in, and the temperature is lower than the temperature;
c la : corresponding to t la The specific heat capacity of the wet air of (3) kJ/kg DEG C;
B. calculating the output heat q of the coal mill ou
Total heat q carried out and consumed by coal mill drying 1kg of coal ou ：
Wherein: q ev Evaporating heat consumed by moisture in raw coal, kJ/kg;
q ag2 : the heat quantity carried by the exhaust gas dryer is kJ/kg;
q f : heating the heat consumed by the fuel, kJ/kg;
q 5 : heat dissipation loss of equipment, kJ/kg;
(1) Heat q of evaporation of water consumption in raw coal ev ：
Wherein: c H2O : steam at t 2 Average constant pressure specific heat capacity at temperature, kJ/(kg. DEG C);
t rc : raw coal temperature, DEG C;
t 2 the outlet temperature of the coal mill is DEG C;
Δm: the amount of water evaporated by the desiccant per kg of raw coal, kg/kg, is calculated according to the following formula:
wherein: m is M ar Raw coal receives base water,%;
M pc coal dust moisture,%;
(2) Heat quantity q carried by exhaust gas drier ag2 ：
Wherein: c a2 : at t 2 Specific heat capacity of humid air, kJ/(kg. Deg.C);
t 2 : the temperature of the medium at the outlet of the coal mill, and the temperature of the medium at the outlet of the coal mill;
(3) Heat q of heating fuel consumption f ：
Wherein: c dc : specific heat capacity of the dry coal, kJ/(kg. DEG C);
q unf : the heat for thawing raw coal is considered when the daily average temperature is lower than 0 ℃;
t a,min : average temperature of the lowest day, DEG C;
c i : specific heat capacity of ice, kJ/(kg. Deg.C);
I d : ice heat of solution, kJ/kg;
t rc : raw coal temperature, DEG C;
(4) Heat dissipation loss q of equipment 5 ：
q 5 ＝0.02×q in kJ/kg
C. Calculating inlet air quantity Q of coal mill 1
Computing mill by heat balanceInlet air quantity Q of coal machine 1 :
q in ＝q ou
The specific method of the third step is as follows: the coal mill measuring air quantity is that the dynamic pressure of the coal mill inlet is measured by a measuring device to calculate the air quantity of the coal mill inlet and display the air quantity value in a DCS control system, the air quantity is calculated in the DCS control system, and the air quantity is calculated by a correction coefficient K A The deviation from the actual air quantity is regulated, and the specific formula is as follows:
wherein:
f is the measured cross-sectional area, m 2 ；
Kd is the calibration coefficient of the speed measuring element;
ρ is the air flow density, kg/m 3 ；
Δp is the measurement device differential pressure, pa;
t is the temperature of the mixed wind and the temperature is lower than the temperature;
ps is the static pressure of the grinding inlet and kPa;
c is the flow measurement device coefficient;
K A k is the total correction coefficient of the coal mill A The original correction coefficient is set as a preset value;
whether the inlet air quantity of the coal mill is corrected or not is judged according to the following conditions:
and if the deviation between the calculated air quantity and the air quantity of the DCS control system is more than 5%, correcting.
The fourth step is to correct the coefficient K of the inlet air quantity of the coal mill 1 The calculation method of (1) is as follows:
wherein: q (Q) 1 The inlet air quantity of the coal mill; q (Q) m The display value of the air quantity measuring point on the DCS control system is obtained.
In the fifth step, the wind pressure correction coefficient K of the inlet of the coal mill 2 The calculation method of (1) is as follows:
wherein: q (Q) Pi For the ith working condition, the inlet static pressure of the coal mill is P Si (other conditions are the same) the inlet air quantity of the coal mill.
The resistance correction coefficient K of the coal mill in the step six 3 The calculation method of (1) is as follows:
wherein: q (Q) Dj For the j-th working condition, the resistance of the coal mill is delta P Sj (other conditions are the same) the inlet air quantity of the coal mill.
The specific calculation method in the step seven is as follows:
the eighth concrete calculation method comprises the steps of correcting the final coal mill inlet air quantity correction coefficient K A Substituting the formula into a measuring device air volume calculation of a DCS control system:
the inlet air quantity correction of the coal mill can be completed.
The invention has good technical effect through practical application, and the application is as follows:
the application example is corrected for inlet air quantity of an HP863dye coal mill (a direct-blowing coal mill).
Step one, obtaining calculation parameters
The coal quality is obtained through rapid analysis of the coal quality of the laser-induced breakdown spectroscopy, and the DCS control system is used for collecting equipment running state information and parameters, wherein the calculated parameters are as follows:
| sequence number | Project | (symbol) | Unit (B) | Numerical value |
| 1 | The water content is received | M ar | ％ | 8.10 |
| 2 | Coal feeding amount of coal mill | B M | t/h | 36.94 |
| 3 | Initial temperature of drying agent after mixing coal mill | t 1 | ℃ | 271.67 |
| 4 | Power consumption of coal mill | e | kW·h/t | 7.21 |
| 5 | Sealing air flow rate of coal mill | Q S | kg/s | 2.58 |
| 6 | Sealing wind temperature | t s | ℃ | 18.86 |
| 7 | The temperature of the cold air is leaked in | t la | ℃ | 20.00 |
| 8 | Outlet temperature of coal mill | t 2 | ℃ | 94.71 |
| 9 | Raw coal temperature | t rc | ℃ | 14.70 |
| 10 | Online air quantity of coal mill | Q m | t/h | 43.45 |
Step two, calculating the inlet air quantity Q of the coal mill under a certain coal quantity according to the mass and heat conservation principle of the coal mill 1
a) Heat generated by the milling member
q mac ＝3.6×0.6e＝15.57
b) Physical heat of seal wind
Wherein, c s To seal the specific heat of wind, the heat can be measured according to t s The specific heat of air at temperature is selected.
c) Physical heat leaking into cold air
q la ＝K le ×c la ×t la ×g 1 ＝0
The HP863dye coal mill is a positive pressure direct blowing coal mill, and the air leakage coefficient is K le Taken as 0. Corresponding to t la Specific heat capacity c of wet air of (2) la The air properties can be checked. The air leakage coefficient can be selected according to the following table.
d) Heat of evaporation of water consumption in raw coal
M pc The selection is made according to fig. 2, the example of application being 1.28. Steam at t 2 Average constant pressure specific heat capacity c at temperature H2O Can check steam property table, raw coal temperature t rc Ambient temperature may be taken.
e) Heat of heating fuel consumption
Specific heat capacity c of dry coal dc Can be selected according to the properties of raw coal, and the heat q for thawing the raw coal unf The temperature is greater than 0 ℃, this time calculated as 0. If the heat of the part is calculated, the specific heat capacity c of the ice i Heat of solution with ice I d Can directly find the water property.
f) Air quantity Q is calculated to coal pulverizer entry 1
Step three, the inlet air quantity Q of the coal mill 1 And the display value Q of the air quantity measuring point on the DCS control system m In contrast, the deviation is calculated.
Original K of DCS control system of coal mill A The value was 1.023.
The deviation amount is more than 5%, and correction is performed.
Step four, determining an air quantity correction coefficient K 1 。
Step five, determining an inlet wind pressure correction coefficient K 2 。
P under different static pressures at coal mill inlet S (other conditions are the same) the inlet air quantity Q of the coal mill Pi The following table, the statistics of group 5 data are as follows.
| Sequence number | Project | (symbol) | Unit (B) | Operating condition Q P1 | Operating condition Q P2 | Operating condition Q P3 | Operating condition Q P4 | Operating condition Q P5 |
| 1 | Inlet wind pressure | P Si | kPa | 6.32 | 6.30 | 6.32 | 6.33 | 6.31 |
| 2 | Air quantity measurement of coal mill | Q Pi | t/h | 41.95 | 44.33 | 42.36 | 46.71 | 40.12 |
Step six, determining a resistance correction coefficient K of the coal mill 3 。
ΔP under different coal mill resistances Sj (other conditions are the same) the inlet air quantity Q of the coal mill Dj The data for the 5 groups are shown in the following table.
| Sequence number | Project | (symbol) | Unit (B) | Operating condition Q D1 | Operating condition Q D2 | Operating condition Q D3 | Operating condition Q D4 | Operating condition Q D5 |
| 1 | Resistance of coal mill | ΔP Sj | kPa | 3.55 | 3.49 | 3.31 | 3.99 | 3.12 |
| 2 | Air quantity measurement of coal mill | Q Dj | t/h | 46.72 | 45.15 | 43.89 | 41.12 | 48.01 |
Step seven, determining a final correction coefficient K A 。
Step eight, final correction coefficient K A Substituting into DCS air quantity expression.
And (3) verification: under 3 working conditions, the inlet air quantity of the coal mill is tested, and the test result is as follows
After the air quantity is corrected, the inlet of the coal mill is tested, and test results show that the air quantity deviation is less than 5%, the maximum deviation is only 2.1%, and the correction method is high in feasibility.
Claims (8)
1. The method for correcting the inlet air quantity of the positive pressure direct blowing coal mill is characterized by comprising the following steps of:
step one: the coal quality is obtained through rapid analysis of the coal quality of the laser-induced breakdown spectrum, and the DCS control system is used for collecting equipment running state information and parameters and used as boundary conditions for calculating the inlet air quantity of the coal mill;
step two: the inlet air quantity Q of the coal mill under a certain coal quantity is calculated according to the mass and heat conservation principle of the coal mill 1 ；
Step three: inlet air quantity Q of coal mill 1 And a display value Q of an air quantity measuring point on an inlet of a coal mill of a DCS control system m In contrast, if the deviation is>5, correcting;
step four: determining the correction coefficient K of the inlet air quantity of the coal mill 1 Air volume correction coefficient K 1 For coal mill inlet air quantity Q 1 And the display value Q of the air quantity measuring point on the DCS control system m Is a ratio of (2);
step five: determining a wind pressure correction coefficient K of an inlet of a coal mill 2 Wind pressure correction coefficient K 2 For different static pressures of the coal mill inlet, the air quantity Q is measured by the coal mill inlet Pi And the display value Q of the air quantity measuring point on the DCS control system m Is a ratio of (2);
step six: determining a resistance correction coefficient K of a coal mill 3 Resistance correction coefficient K 3 For different coal mill resistances, the inlet of the coal mill measures the air quantity Q Dj And the display value Q of the air quantity measuring point on the DCS control system m Is a ratio of (2);
step seven: determining a final correction coefficient K A For the air quantity correction coefficient K 1 Inlet wind pressure correction factor K 2 Resistance correction coefficient K of coal mill 3 Product of the three and original K A A ratio of values;
step eight: will finally correct coefficient K A Substituting the DCS air quantity expression to obtain the DCS air quantity expression capable of reflecting the real value of the inlet air quantity of the coal mill;
the specific method of the second step is as follows:
A. calculating the input heat q of the coal mill in
Total heat q input by coal mill for drying 1kg coal in ：
q in ＝q ag1 +q la +q s +q mac
Wherein: q ag1 : physical heat of the desiccant, kJ/kg;
q la : physical heat leaking into cold air, kJ/kg;
q s : sealing the physical heat of wind, kJ/kg;
q mac : mechanical heat generated by the operation of the coal mill, kJ/kg;
(1) Physical heat q of desiccant ag1 ：
q ag1 ＝c ag1 g 1 t 1 kJ/kg
Wherein: c ag1 : at t 1 At each temperatureThe component drying agent has the weight average mass specific heat, kJ/kg DEG C;
t 1 : the initial temperature of the drying agent after mixing of the coal mill is set at DEG C;
g 1 : the inlet drying dose of the coal mill, kg/kg, is calculated according to the following formula:
wherein: q (Q) 1 : inlet air quantity of the coal mill, kg/s;
B M the coal feeding amount of the coal mill is t/h;
(2) Heat q generated by milling members mac ：
q mac ＝3.6×0.6e kJ/kg
Wherein: e is the unit power consumption of the coal mill, kW.h/t;
(3) Physical heat q of seal wind s ：
Wherein: q (Q) S Kg/s for sealing the wind mass flow;
c s for sealing the specific heat of wind, kJ/kg DEG C;
t s sealing the air temperature, and the temperature is DEG C;
(4) Physical heat q of cold air leakage la ：
q la ＝K le ×c la ×t la ×g 1 kJ/kg
Wherein: k (K) le : the air leakage rate of the pulverizing system is the proportion of the air leakage rate of the coal mill to the amount of the inlet drying agent, and can be determined according to the specification of the coal mill;
t la : the temperature of the cold air is leaked in, and the temperature is lower than the temperature;
c la : corresponding to t la The specific heat capacity of the wet air of (3) kJ/kg DEG C;
B. calculating the output heat q of the coal mill ou
Coal mill drying 1kg coalTotal heat q carried out and consumed ou ：
q ou ＝q ev +q ag2 +q f +q 5 kJ/kg
Wherein: q ev Evaporating heat consumed by moisture in raw coal, kJ/kg;
q ag2 : the heat quantity carried by the exhaust gas dryer is kJ/kg;
q f : heating the heat consumed by the fuel, kJ/kg;
q 5 : heat dissipation loss of equipment, kJ/kg;
(1) Heat q of evaporation of water consumption in raw coal ev ：
q ev ＝ΔM×(2500+c H2O ×t 2 -4.187t rc )kJ/kg
Wherein: c H2O : steam at t 2 Average constant pressure specific heat capacity at temperature, kJ/(kg. DEG C);
t rc : raw coal temperature, DEG C;
t 2 the outlet temperature of the coal mill is DEG C;
Δm: the amount of water evaporated by the desiccant per kg of raw coal, kg/kg, is calculated according to the following formula:
wherein: m is M ar Raw coal receives base water,%;
M pc coal dust moisture,%;
(2) Heat quantity q carried by exhaust gas drier ag2 ：
Wherein: c a2 : at t 2 Specific heat capacity of humid air, kJ/(kg. Deg.C);
t 2 : the temperature of the medium at the outlet of the coal mill, and the temperature of the medium at the outlet of the coal mill;
(3) Heat q of heating fuel consumption f ：
Wherein: c dc : specific heat capacity of the dry coal, kJ/(kg. DEG C);
q unf : the heat for thawing raw coal is considered when the daily average temperature is lower than 0 ℃;
t a,min : average temperature of the lowest day, DEG C;
c i : specific heat capacity of ice, kJ/(kg. Deg.C);
I d : ice heat of solution, kJ/kg;
t rc : raw coal temperature, DEG C;
(4) Heat dissipation loss q of equipment 5 ：
q 5 ＝0.02×q in kJ/kg
C. Calculating inlet air quantity Q of coal mill 1
Calculating inlet air quantity Q of coal mill through heat balance 1 :
q in ＝q ou
2. The method for correcting the inlet air quantity of the positive pressure direct-blowing coal mill according to claim 1, wherein the first step is specifically as follows: coal quality is obtained by rapid analysis of coal quality based on laser-induced breakdown spectroscopy, and raw coal is obtained to receive base moisture M ar As basic data of air volume calculation of the positive pressure direct blowing coal mill, acquiring equipment running state information and parameters through a DCS control system and obtaining the following information: coal feeding quantity B of coal mill M Initial temperature t of drying agent after mixing coal mill 1 Power consumption e of coal mill and sealing air mass flow Q of coal mill S Sealing wind temperature t s Temperature t of cold air leakage la Outlet temperature t of coal mill 2 Raw coal temperature t rc The inlet static pressure of the coal mill is P Si Coal mill inlet air quantity Q Pi Coal mill resistance ΔPs j Inlet air quantity Q of coal mill Dj The coal mill measures the air quantity Qm.
3. The method for correcting the inlet air quantity of the positive pressure direct-blowing coal mill according to claim 1, wherein the specific method in the third step is as follows: the coal mill measuring air quantity is that the dynamic pressure of the coal mill inlet is measured by a measuring device to calculate the air quantity of the coal mill inlet and display the air quantity value in a DCS control system, the air quantity is calculated in the DCS control system, and the air quantity is calculated by a correction coefficient K A The deviation from the actual air quantity is regulated, and the specific formula is as follows:
wherein:
f is the measured cross-sectional area, m 2 ；
Kd is the calibration coefficient of the speed measuring element;
ρ is the air flow density, kg/m 3 ；
Δp is the measurement device differential pressure, pa;
t is the temperature of the mixed wind and the temperature is lower than the temperature;
ps is the static pressure of the grinding inlet and kPa;
c is the flow measurement device coefficient;
K A k is the total correction coefficient of the coal mill A The original correction coefficient is set as a preset value;
whether the inlet air quantity of the coal mill is corrected or not is judged according to the following conditions:
and if the deviation between the calculated air quantity and the air quantity of the DCS control system is more than 5%, correcting.
4. The method for correcting the inlet air quantity of the positive pressure direct-blowing coal mill according to claim 1, wherein in the fourth step, the inlet air quantity correction coefficient K of the coal mill is 1 The calculation method of (1) is as follows:
wherein: q (Q) 1 The inlet air quantity of the coal mill; q (Q) m The display value of the air quantity measuring point on the DCS control system is obtained.
5. The method for correcting the inlet air quantity of the positive pressure direct-blowing coal mill according to claim 1, wherein in the fifth step, the air pressure correction coefficient K of the inlet of the coal mill is 2 The calculation method of (1) is as follows:
wherein: q (Q) Pi For the ith working condition, the inlet static pressure of the coal mill is P Si Inlet air quantity of the lower coal mill.
6. The method for correcting the inlet air quantity of the positive pressure direct-blowing coal mill according to claim 1, wherein in the sixth step, the resistance correction coefficient K of the coal mill is 3 The calculation method of (1) is as follows:
wherein: q (Q) Dj For the j-th working condition, the resistance of the coal mill is delta P Sj Inlet air quantity of coal mill.
7. The method for correcting the inlet air quantity of the positive pressure direct-blowing coal mill according to claim 1, wherein the specific calculation method in the step seven is as follows:
final correction coefficient
8. The method for correcting the inlet air quantity of the positive pressure direct-blowing coal mill according to claim 1, wherein the step eight concrete calculation method is that the final inlet air quantity correction coefficient K of the coal mill A Substituting the formula into a measuring device air volume calculation of a DCS control system:
the inlet air quantity correction of the coal mill can be completed.
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