CN115970865A - Method for controlling pulverized coal concentration of medium-speed coal mill in real time through variable-speed adjustment of rare earth motor - Google Patents
Method for controlling pulverized coal concentration of medium-speed coal mill in real time through variable-speed adjustment of rare earth motor Download PDFInfo
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Abstract
The invention relates to a method for controlling the concentration of pulverized coal of a medium-speed coal mill in real time by variable-speed adjustment of a rare earth motor, which comprises the following steps: carrying out operation tests of different rotating speeds and different coal mill inlet primary air quantities on the coal mills under the condition of the same coal type and the same coal feeding quantity; optimizing an original wind-coal ratio curve of a pulverizing system; and obtaining the wind-coal ratio curve of the coal mill at different rotating speeds. The invention has the beneficial effects that: aiming at different rotating speed states of the variable speed adjusting coal mill, an optimal wind-coal ratio curve corresponding to the coal mill at each rotating speed is provided, so that the real-time control of the coal powder concentration of the medium speed coal mill is realized, and the stability of ignition and combustion of the coal powder at each rotating speed is improved; the problem that pulverized coal combustion stability and burnout performance are poor when low-heat value and high-ash coal is combusted is effectively solved, the pulverized coal combustion stability and burnout performance can be improved, and the safety, stability and economy of unit operation are further improved.
Description
Technical Field
The invention belongs to the field of coal mill control, and particularly relates to a method for controlling the concentration of pulverized coal of a medium-speed coal mill in real time through variable speed adjustment of a rare earth motor.
Background
In recent years, domestic power plants begin to burn a large amount of low-calorific-value and high-ash coal types, the coal types inevitably cause the deterioration of the combustion stability and the burnout performance of pulverized coal, further cause the deterioration of the combustion efficiency of a boiler, and the unstable combustion of the pulverized coal can also influence the safe and stable operation of a unit under the low-load working condition.
One of the means for improving the combustion stability of the boiler is a method for improving the fineness of pulverized coal and the concentration of primary air and powder, and in order to solve the problems, power station boiler technicians have made a lot of efforts and works, such as improving the fineness of pulverized coal by adjusting an outlet separator of a coal mill, but the improvement of the fineness of pulverized coal causes the problems of reduced output of the coal mill, increased power consumption and the like; the coal powder burnout rate is improved by reducing the primary air quantity at the inlet of the coal mill, but the reduction of the primary air quantity at the inlet of the coal mill can cause the problems of increase of the discharge amount of pebble coal, powder accumulation of a coal powder pipe and the like.
The technical measures cannot fundamentally solve the problems of poor combustion stability and burnout performance of the pulverized coal when low-heat-value and high-ash coal is combusted, so that a novel method for controlling the concentration of the pulverized coal of the medium-speed coal mill in real time is urgently needed.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a method for controlling the concentration of pulverized coal of a medium-speed coal mill in real time by variable-speed adjustment of a rare earth motor.
The method for regulating the coal powder concentration of the medium-speed coal mill in real time by the rare earth motor in a variable speed manner comprises the following steps:
step one, carrying out operation tests of different rotating speeds and different coal mill inlet primary air quantities on the coal mills under the condition of the same coal type and the same coal feeding quantity, and stably operating the coal pulverizing system for a certain time period t 0 Then, measuring the time average value of the primary air speed and the coal powder fineness in a certain period t through a coal powder sampling hole, measuring the time average value of the discharge amount of pebble coal in the certain period t through a pebble coal discharge port, recording the operation parameters of a pulverizing system in the certain period through a DCS or PI system, and calculating the coal powder concentration; the design rotating speed of the coal mill is n, and the design maximum output coal supply is Q Max The rated current of the rare earth motor frequency converter of the variable speed coal mill is I;
step two, combining the coal powder concentration and coal powder fineness test results obtained in the step one, and optimizing an original wind-coal ratio curve of a coal pulverizing system; and obtaining the wind-coal ratio curve of the coal mill at different rotating speeds.
Preferably, in the step one: controlling the primary air quantity at the inlet and the outlet temperature of the coal mill through a primary cold air adjusting door and a primary hot air adjusting door; determining a reference value of primary air volume at the inlet of the coal mill according to the coal feeding volume and the original air-coal ratio curve;
the original wind-coal ratio curve is specifically that when the coal feeding amount is [0,a) t/h, the primary wind volume at the inlet of the coal mill is qt/h; when the coal feeding amount is [ a, b ] t/h, the primary air volume at the inlet of the coal mill is,
Q＝q+K×(m-a)
wherein Q is the primary air volume at the inlet of the coal mill and the unit is t/h; q is the lowest ventilation quantity designed for the coal mill, and the unit t/h; m represents the coal feeding amount and is unit t/h; a is the lowest coal feeding amount of the coal mill, and the unit t/h; b, designing the maximum output of the coal mill in a unit of t/h; k is a constant and is provided by a coal mill manufacturer.
Preferably, in the step one: controlling the fineness standard of the pulverized coal to be R90 through the opening degree of a baffle of the static separator; the loading force of the coal mill is determined by the original loading curve of the coal mill.
Preferably, in the step one: the primary air speed and the coal powder fineness are obtained by weighted average calculation of measurement results of coal powder sampling holes 11 on outlet powder pipes of a plurality of coal mills.
Preferably, in the step one, tests of five working conditions are respectively carried out, and the setting of the rotating speed and the primary air volume at the inlet of the coal mill in the five working conditions is respectively as follows:
the rotating speed of the coal mill is 0.75n, and the offset of the primary air volume of the inlet of the coal mill relative to a reference value is +5t/h;
the rotating speed is 0.9n, and the offset of the primary air volume of the inlet of the coal mill relative to a reference value is +2t/h;
the rotating speed is n, and the bias of the primary air volume of the inlet of the coal mill relative to a reference value is 0t/h;
the rotating speed is 1.1n, and the offset of the primary air volume of the inlet of the coal mill relative to a reference value is-2 t/h;
the rotating speed is 1.25n, and the offset of the primary air volume of the inlet of the coal mill relative to a reference value is-5 t/h.
Preferably, in the step one: t is t 0 30min, t is more than or equal to 2h.
Preferably, the calculation formula of the coal dust concentration c is as follows:
wherein c is the concentration of coal powder, kg/kg; m is the time average value of coal feeding amount, t/h; m is the time average value of the discharge amount of the pebble coal, kg/h; and q is the time average value of the primary air volume at the inlet of the coal mill, and t/h.
Preferably, in step two: and gradually reducing the coefficient K of the air-coal ratio curve of the coal mill along with the increase of the rotating speed to obtain the air-coal ratio curve of the coal mill at different rotating speeds.
The invention has the beneficial effects that:
1) The invention provides a method for improving the pulverized coal concentration of a pulverized coal pipe at the outlet of a coal mill based on variable speed adjustment of a rare earth motor, which aims at different rotating speed states of the coal mill with variable speed adjustment, provides an optimal wind-coal ratio curve corresponding to the coal mill at each rotating speed, realizes real-time control of the pulverized coal concentration of a medium-speed coal mill, and improves the ignition combustion stability of the pulverized coal at each rotating speed.
2) The invention can not only effectively solve the problems of poor combustion stability and burnout performance of the pulverized coal when the coal with low heat value and high ash content is used, but also improve the combustion stability and burnout performance of the pulverized coal for the conventional coal used for combustion, and further improve the safety stability and the economical efficiency of the unit operation.
Drawings
FIG. 1 is a schematic diagram of a pulverizing system;
FIG. 2 is a schematic illustration of coal mill outlet dust tube sampling and coal mill bottom pebble coal sampling;
FIG. 3 is an original wind-coal ratio curve of a pulverizing system;
FIG. 4 is a line graph showing variation of coal dust concentration and pebble coal discharge under different working conditions;
FIG. 5 is a graph of the air-coal ratio of the pulverizing system of the optimized variable speed coal mill.
Description of the reference numerals: the device comprises a coal bunker 1, a coal feeder 2, a coal mill 3, a variable speed motor 4, a variable frequency control unit 5, a static separator 6, a cold primary air adjusting door 7, a hot primary air adjusting door 8, a coal mill outlet powder pipe 9, a boiler 10, a coal mill outlet powder pipe coal powder sampling hole 11 and a pebble coal discharge port 12.
Detailed Description
The present invention will be further described with reference to the following examples. The following examples are set forth merely to aid in the understanding of the invention. It should be noted that, for a person skilled in the art, several modifications can be made to the invention without departing from the principle of the invention, and these modifications and modifications also fall within the protection scope of the claims of the present invention.
Example one
As an example, as shown in fig. 1, the pulverizing system includes: the system comprises a coal bunker 1, a coal feeder 2, a coal mill 3, a variable speed coal mill motor 4, a variable frequency control unit 5, a static separator 6, a cold primary air adjusting door 7, a hot primary air adjusting door 8, a coal mill outlet powder pipe 9 and a boiler 10; a coal mill outlet powder pipe coal powder sampling hole 11 is arranged on the coal mill outlet powder pipe 9; the variable-frequency control unit 5 is electrically connected with the variable-speed coal mill motor 4, and the variable-speed coal mill motor 4 is electrically connected with the coal mill 3; the coal bunker 1 is connected with a coal feeder 2, and the coal feeder 2 is connected with a coal mill 3; a static separator 6 is arranged at the outlet of the coal mill 3, the static separator 6 is connected with a coal mill outlet powder pipe 9, and the coal mill outlet powder pipe 9 is connected to a boiler 10; a pebble coal discharge port is formed in the bottom of the coal mill 3; the coal mill 3 is also provided with a cold primary air adjusting door 7 and a hot primary air adjusting door 8. The powder making system is provided with a frequency converter, and a remote control signal interface is arranged on the frequency converter; the frequency conversion control unit 5 controls the frequency converter, the variable speed coal mill motor 4 is driven by the frequency converter, and the variable speed coal mill motor 4 drives the coal mill 3 to rotate.
When the coal pulverizing system operates, raw coal enters a coal feeder 2 from a coal bunker 1, enters a coal mill 3 from a coal feeder down pipe, the coal mill 3 drives the coal mill 3 to rotate through a variable speed coal mill motor 4 and a variable frequency control unit 5, after raw coal particles are ground into coal powder, the coal powder is separated through a folding baffle of a static separator 6, the coal powder with proper fineness enters a boiler 10, the coal powder with slightly coarse fineness enters the coal mill 3 again to be ground, the power for the coal powder to enter the boiler 10 mainly comes from primary air at an inlet of the coal mill, the primary air enables the coal powder to enter the boiler 10, the coal powder heating effect is achieved, and ignition and combustion of the coal powder after entering the boiler 10 are facilitated.
The method for controlling the concentration of the pulverized coal of the medium-speed coal mill in real time by the variable-speed adjustment of the rare earth motor of the pulverizing system comprises the following steps:
the method comprises the following steps that firstly, five running tests of different rotating speeds and different coal mill inlet primary air quantities are carried out on a coal mill 3 under the condition of the same coal type and the same coal feeding quantity, and the fineness standard of coal powder is controlled to be R90 through the opening degree of a baffle of a static separator 6; the loading force of the coal mill 3 is determined by the original loading curve of the coal mill 3. The primary air quantity and the outlet temperature of the inlet of the coal mill are controlled by a primary air adjusting door 7 and a primary air adjusting door 8; determining a reference value of primary air volume at the inlet of the coal mill according to the coal feeding volume and the original air-coal ratio curve;
the original wind-coal ratio curve is specifically that when the coal feeding amount is [0,a) t/h, the primary wind volume at the inlet of the coal mill is qt/h; when the coal feeding amount is [ a, b ] t/h, the reference value of the primary air volume at the inlet of the coal mill is
Q＝q+K×(m-a)
Wherein Q is the primary air volume at the inlet of the coal mill and the unit is t/h; q is the lowest ventilation quantity designed for the coal mill, and the unit t/h; m represents the coal feeding amount, and the unit t/h; a is the lowest coal feeding amount of the coal mill, and the unit t/h; b, designing the maximum output of the coal mill in unit of t/h; k is a constant and is provided by a coal mill manufacturer.
The setting of the rotating speed and the primary air quantity at the inlet of the coal mill in five working conditions is respectively
The rotating speed of the coal mill is 0.75n, and the offset of the primary air volume of the inlet of the coal mill relative to a reference value is +5t/h;
the rotating speed is 0.9n, and the offset of the primary air volume of the inlet of the coal mill relative to a reference value is +2t/h;
the rotating speed is n, and the offset of the primary air volume of the inlet of the coal mill relative to a reference value is 0t/h;
the rotating speed is 1.1n, and the bias of the primary air volume of the inlet of the coal mill relative to a reference value is-2 t/h;
the rotating speed is 1.25n, and the offset of the primary air volume of the inlet of the coal mill relative to a reference value is-5 t/h.
After the pulverizing system stably operates for 30 minutes in a certain period of time, measuring the time average value of the primary air speed and the pulverized coal fineness in at least two hours in the certain period of time through the pulverized coal sampling hole 11, measuring the time average value of the discharge amount of pebble coal in the certain period of time t through the pebble coal discharge port 12, recording the operating parameters of the pulverizing system in the certain period of time through a DCS or PI system, and calculating the pulverized coal concentration; the design rotating speed of the coal mill 3 is n, and the design maximum output coal supply is Q Max The rated current of the rare earth motor frequency converter of the variable speed coal mill is I;
the primary air speed and the coal powder fineness are obtained by weighted average calculation of the measurement results of coal powder sampling holes 11 on a plurality of coal mill outlet powder pipes 9.
The coal dust concentration c is calculated by the formula
Wherein c is the concentration of coal powder, kg/kg; m is the time average value of coal feeding amount, t/h; m is the time average value of the discharge amount of the pebble coal, kg/h; and q is the time average value of the primary air volume at the inlet of the coal mill, and t/h.
And step two, combining the coal powder concentration and coal powder fineness test results obtained in the step one, optimizing the original wind-coal ratio curve of the coal pulverizing system, specifically, gradually reducing the coefficient K of the wind-coal ratio curve of the coal mill 3 along with the increase of the rotating speed, and obtaining the wind-coal ratio curve of the coal mill 3 at different rotating speeds.
Example two
On the basis of the first embodiment, the second embodiment of the present application provides an application of the method for increasing the concentration of pulverized coal in the outlet pulverized coal pipe of the coal mill based on the variable speed coal mill in the first embodiment to a certain coal mill of a certain power plant:
the design rotating speed of the coal mill is 24r/min, and the design minimum output coal quantity is 15.18t/h; specific coal mill parameters are shown in the following table:
the parameters of the motor of the matched variable speed coal mill are shown in the following table:
a method for improving the concentration of coal powder in a coal mill outlet powder pipe for a variable speed coal mill is provided. For the coal mill with the design rotating speed of n and the design output coal quantity of Q, coal dust concentration and coal dust fineness test tests are carried out under different rotating speeds under the same coal type and the same coal quantity, and 4 test working conditions are totally obtained.
And acquiring the coal feeding quantity parameter through the operation parameter of the coal feeder. The coal feeder can control the coal feeding amount through the belt rotating speed, and the coal feeding amount is calibrated periodically; to obtain a large coal feed rate, a fast belt speed is required. In the embodiment, the coal feeding amount is selected to be 45t/h.
The outlet temperature and the inlet primary air quantity of the coal mill are controlled through a cold primary air adjusting door 7 and a hot primary air adjusting door 8 at the inlet of the coal mill, wherein the outlet temperature of the coal mill is controlled through the opening degree of the cold primary air adjusting door 7, and the temperature is reduced when the cold primary air adjusting door 7 is opened; the hot primary air adjusting door 8 controls the primary air quantity at the inlet of the coal mill through the opening degree of the air door baffle; the cold air adjusting door at the inlet of the coal mill adjusts the temperature, and the hot air door adjusts the primary air quantity. In the embodiment, the primary air volume of the inlet of the coal mill is adjusted by changing the opening of the damper through setting offset of the control panel of the hot air adjusting door at the inlet of the coal mill on the basis of the air-coal ratio control logic, and the outlet temperature of the coal mill is automatically adjusted to be kept unchanged at 75 ℃ through the opening of the damper at the inlet of the coal mill.
The fineness standard of the coal powder is adjusted by the opening of a baffle of the static separator 6 at the outlet of the coal mill. The opening adjusting range of the baffle of the static separator 6 is 10-80 degrees, the larger the opening of the baffle of the static separator 6 is, the larger the fineness standard of the coal powder is, and the smaller the opening of the baffle of the static separator 6 is, the smaller the fineness standard of the coal powder is. The large fineness standard means that the particle size of the pulverized coal is large, and the small fineness standard means that the particle size of the pulverized coal is small. In the embodiment, the opening degree of the static separator at the outlet of the coal mill is kept unchanged at 55 degrees.
The hydraulic loading force of the grinding roller of the coal mill is 4MPa when the coal feeding amount is 0, 20 t/h; when the coal feeding amount is (20, 60) t/h, the hydraulic loading force of the grinding roller of the coal mill is y =0.3x-2 (MPa), and when the coal feeding amount is (60, 70) t/h, the hydraulic loading force of the grinding roller of the coal mill is 16MPa.
The variable speed coal mill motor rotating speed of the coal mill is controlled through the variable frequency control unit 5, and then the coal mill grinding roller is driven to operate at different rotating speeds. Determining a reference value of primary air volume at the inlet of the coal mill according to the coal feeding volume and the original air-coal ratio curve; in the embodiment, the coal feeding amount is selected to be 45t/h, and as the maximum output of the coal mill cannot reach 45t/h when the rotating speed is 0.75n, the rotating speed is only 0.9n, and the primary air volume deviation of the inlet of the coal mill is +2t/h; the rotating speed is n, and the primary air volume offset of the inlet of the coal mill is 0t/h; the rotating speed is 1.1n, and the primary air quantity deviation of the inlet of the coal mill is-2 t/h; the test is carried out under four working conditions that the rotating speed is 1.25n and the primary air quantity deviation of the inlet of the coal mill is-5 t/h.
And (3) under the boundary conditions of the steps 102, 103 and 104, after the operation parameters are stabilized for 30min, carrying out primary air speed, coal powder fineness and pebble coal discharge test tests, and simultaneously recording relevant operation parameters including coal feeding quantity, coal mill current, primary air quantity and time average value of coal mill outlet temperature during the test period through a DCS and a PI system, wherein the test time after stabilization is not less than 2h.
As shown in fig. 2, which is a schematic diagram of coal pulverizer outlet pulverized coal sampling and coal pulverizer bottom pulverized coal sampling in this embodiment, under different working conditions, primary air speed and pulverized coal fineness tests are sequentially performed on 6 pulverized coal pipes at the coal pulverizer outlet, and weighted average is performed to obtain the pulverized coal fineness R90 under the working condition, and coal pulverizer bottom pulverized coal sampling is performed at a coal pulverizer bottom pulverized coal discharge port, and calculated to obtain an average value.
The coal powder concentration calculation process is as follows:
in the formula: c is the concentration of coal powder, kg/kg;
m is the average value of coal feeding amount, t/h;
m is the average value of the discharge amount of the pebble coal, kg/h;
and q is the time average value of the primary air volume at the inlet of the coal mill, t/h.
The following table shows the calibration results of the primary wind speed of the pulverized coal pipe at the outlet of the variable speed coal mill according to the different working conditions measured in step 106 in this embodiment:
the following table shows the results of parameters such as coal powder concentration and coal powder fineness at the outlet of the coal mill at different rotating speeds, and the change broken line graphs of coal powder concentration and pebble coal emission under different working conditions are obtained as shown in fig. 4.
From the above table we find: under the working condition of 45t/h, the coal feeding quantity of the rare earth motor variable speed coal mill is increased along with the increase of the rotating speed, the primary air quantity of the inlet of the coal mill is properly reduced, namely the air-coal ratio is properly reduced, and the air speed of each powder pipe at the outlet of the coal mill is not greatly changed and is larger than 18m/s; the fineness R90 of the coal powder at the outlet of the coal mill is not greatly changed and is within the design range; the discharge amount of pebble coal of the coal mill is not obviously changed, and the concentration of coal dust at the outlet of the coal mill is increased.
Therefore, the primary air quantity at the inlet of the coal mill is properly reduced along with the increase of the rotating speed, and the effect of increasing the concentration of the coal dust at the outlet of the coal mill is achieved. According to the conclusion, the wind-coal ratio curve of the variable-speed coal mill is optimized, and the wind-coal ratio is reduced by properly reducing the coefficient of the primary wind of the inlet of the coal mill, which is changed along with the coal feeding amount, when the rotating speed of the variable-speed coal mill is increased.
Obtaining an optimized wind-coal ratio curve schematic diagram as shown in fig. 5, specifically:
the rotating speed of the coal mill is 18r/min, and when the coal feeding amount is 0, 15.18) t/h, the primary air volume at the inlet of the coal mill is 72.16t/h; when the coal feeding amount is [15.18, 61.5] t/h, the primary air volume at the inlet of the coal mill is q =72.16+0.847 (m-15.18).
The rotating speed of the coal mill is 21r/min, and when the coal feeding amount is 0, 15.18) t/h, the primary air volume at the inlet of the coal mill is 72.16t/h; when the coal feeding amount is [15.18, 61.5] t/h, the primary air volume at the inlet of the coal mill is q =72.16+0.782 (m-15.18).
The rotating speed of the coal mill is 24r/min, the wind-coal ratio curve is consistent with the original designed wind-coal ratio curve, namely when the coal feeding amount is 0, 15.18) t/h, the primary wind volume at the inlet of the coal mill is 72.16t/h; when the coal feeding amount is [15.18, 61.5] t/h, the primary air volume at the inlet of the coal mill is q =72.16+0.739 (m-15.18).
The rotating speed of the coal mill is 27r/min, and when the coal feeding amount is 0, 15.18) t/h, the primary air volume at the inlet of the coal mill is 72.16t/h; when the coal feeding amount is [15.18, 61.5] t/h, the primary air volume at the inlet of the coal mill is q =72.16+0.696 (m-15.18).
The rotating speed of the coal mill is 30r/min, and when the coal feeding amount is 0, 15.18) t/h, the primary air volume at the inlet of the coal mill is 72.16t/h; when the coal feeding amount is [15.18, 61.5] t/h, the primary air volume at the inlet of the coal mill is q =72.16+0.631 (m-15.18).
Wherein q represents the primary air volume at the inlet of the coal mill and the unit is t/h; m represents the coal feeding amount and has the unit of t/h.
Through the optimization, the problem of poor combustion stability and burnout performance of the pulverized coal during the combustion of low-heat-value and high-ash coal can be effectively solved, the combustion stability and burnout performance of the pulverized coal can be improved for conventional coal for combustion, and the safety, stability and economy of unit operation are further improved. Meanwhile, 2-3 constant-speed coal mills can be changed into the rare earth motor variable-speed adjustment coal mill by each unit.
Claims (8)
1. A method for adjusting the coal powder concentration of a medium-speed coal mill in real time through variable speed regulation by a rare earth motor is characterized by comprising the following steps:
step one, carrying out operation tests of different rotating speeds and different coal mill inlet primary air quantities on the coal mill (3) under the condition of the same coal type and the same coal feeding quantity, and stably operating the coal pulverizing system for a certain time period t 0 Then, measuring the time average value of the primary air speed and the coal powder fineness in a certain period of time t through a coal powder sampling hole (11), measuring the time average value of the discharge amount of pebble coal in the certain period of time t through a pebble coal discharge port (12), recording the operating parameters of a pulverizing system in the period of time through a DCS or PI system, and calculating the coal powder concentration; the design rotating speed of the coal mill (3) is n, and the design maximum output coal supply is Q Max The rated current of the rare earth motor frequency converter of the variable speed coal mill is I;
step two, combining the coal powder concentration and coal powder fineness test results obtained in the step one, and optimizing an original wind-coal ratio curve of a coal pulverizing system; and obtaining the wind-coal ratio curve of the coal mill (3) at different rotating speeds.
2. The method for controlling the concentration of the pulverized coal of the medium-speed coal mill in real time through variable-speed adjustment of the rare earth motor according to claim 1 is characterized in that in the first step: the primary air quantity of the inlet of the coal mill and the outlet temperature are controlled through a primary cold air adjusting door (7) and a primary hot air adjusting door (8); determining a reference value of primary air volume at the inlet of the coal mill according to the coal feeding volume and the original air-coal ratio curve;
the original wind-coal ratio curve is specifically that when the coal feeding amount is [0,a) t/h, the primary wind volume at the inlet of the coal mill is qt/h; when the coal feeding amount is [ a, b ] t/h, the primary air volume at the inlet of the coal mill is,
Q＝q+K×(m-a)
wherein Q is the primary air volume at the inlet of the coal mill and the unit is t/h; q is the lowest ventilation quantity designed for the coal mill, and the unit t/h; m represents the coal feeding amount and is unit t/h; a is the lowest coal feeding quantity of the coal mill in unit t/h; b, designing the maximum output of the coal mill in a unit of t/h; k is a constant and is provided by a coal mill manufacturer.
3. The method for controlling the concentration of the pulverized coal of the medium-speed coal mill in real time through variable-speed adjustment of the rare earth motor according to claim 1 is characterized in that in the first step: the fineness standard of the pulverized coal is controlled to be R90 through the opening of a baffle of the static separator (6); the loading force of the coal mill (3) is determined by the original loading curve of the coal mill (3).
4. The method for controlling the concentration of the pulverized coal of the medium-speed coal mill in real time through variable-speed adjustment of the rare earth motor according to claim 1 is characterized in that in the first step: the primary air speed and the coal powder fineness are obtained by weighted average calculation of measurement results of coal powder sampling holes (11) on outlet powder pipes (9) of a plurality of coal mills.
5. The method for adjusting the pulverized coal concentration of the medium-speed coal mill in real time through the variable speed of the rare earth motor according to claim 2, wherein in the step one, five working conditions are respectively tested, and the rotating speed and the primary air volume at the inlet of the coal mill in the five working conditions are respectively set as follows:
the rotating speed of the coal mill is 0.75n, and the offset of the primary air volume of the inlet of the coal mill relative to a reference value is +5t/h;
the rotating speed is 0.9n, and the offset of the primary air volume of the inlet of the coal mill relative to a reference value is +2t/h;
the rotating speed is n, and the offset of the primary air volume of the inlet of the coal mill relative to a reference value is 0t/h;
the rotating speed is 1.1n, and the offset of the primary air volume of the inlet of the coal mill relative to a reference value is-2 t/h;
the rotating speed is 1.25n, and the offset of the primary air volume of the inlet of the coal mill relative to a reference value is-5 t/h.
6. The method for controlling the concentration of the pulverized coal of the medium-speed coal mill in real time through variable-speed adjustment of the rare earth motor according to claim 1 is characterized in that in the first step: t is t 0 30min, t is more than or equal to 2h.
7. The method for controlling the pulverized coal concentration of a medium speed coal mill in real time through variable speed adjustment of the rare earth motor according to claim 1, wherein in the step one, the calculation formula of the pulverized coal concentration c is as follows:
wherein c is the concentration of coal powder, kg/kg; m is the time average value of the coal feeding amount, t/h; m is the time average value of the discharge amount of the pebble coal, kg/h; and q is the time average value of the primary air volume at the inlet of the coal mill, and t/h.
8. The method for adjusting the pulverized coal concentration of the medium-speed coal mill in real time through variable speed of the rare earth motor according to claim 2 is characterized in that in the second step: and gradually reducing the coefficient K of the air-coal ratio curve of the coal mill (3) along with the increase of the rotating speed to obtain the air-coal ratio curve of the coal mill (3) at different rotating speeds.
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| CN202310087766.7A CN115970865A (en) | 2023-01-12 | 2023-01-12 | Method for controlling pulverized coal concentration of medium-speed coal mill in real time through variable-speed adjustment of rare earth motor |
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