Method for controlling SCR inlet smoke temperature based on variable frequency regulation coal mill

Abstract

The invention discloses a method for controlling SCR (selective catalytic reduction) inlet smoke temperature based on a variable-frequency adjusting coal mill, which comprises the following steps of: 1, designing the reference rotating speed of the coal mill as n, designing the coal quantity of the coal mill under a specific load as M, acquiring the value of the coal quantity M according to the operating parameters of a coal feeder, and designing the rotating speed of a dynamic separator as R; 2, under the condition that the boundary conditions are consistent, coal mill pulverized coal fineness testing experiments under different rotating speeds n are conducted on the coal pulverizing system, and meanwhile recommended rotating speeds NM under different coal quantities are given; 3, under the condition that the boundary conditions are consistent, coal mill pulverized coal fineness testing experiments are conducted on the coal pulverizing system at different dynamic separator rotating speeds; and 4, under the low-load working condition of the boiler, different coal mill combinations are switched, the rotating speed of the dynamic separator is changed, and SCR inlet smoke temperature curves under different coal quantities and different rotating speeds of the dynamic separator are obtained. The combustion efficiency of the boiler under the low load of the unit can be improved, and the whole system can operate more efficiently.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal mill control, and particularly relates to a method for controlling the SCR inlet flue gas temperature of a coal mill based on a rare earth motor variable frequency regulation during unit deep peak shaving. BACKGROUND

[0002] With the continuous optimization of energy structure, in recent years, new energy such as photovoltaic and wind power has developed rapidly. In order to effectively alleviate the new energy consumption problem and further tap the deep peak shaving potential of traditional coal-fired units which occupy the main position of power generation, it has become the most convenient, rapid and efficient way to solve the new energy consumption dilemma. The energy saving and consumption reduction of thermal power plants is of great social significance to low-carbon development, so a series of economic and safety problems need to be solved during the low-load deep peak shaving operation of thermal power units, such as the low SCR inlet temperature affecting the denitration efficiency, the poor stability of the boiler coal burner without oil combustion, and other difficult problems that need to be solved.

[0003] In view of the problem that the low SCR inlet flue gas temperature affects the denitration efficiency during the low-load deep peak shaving operation of the unit, domestic research scholars have made a lot of efforts and work, such as low-load fine combustion adjustment, optimization and transformation of the pre-combustion chamber burner, dynamic separator, coal powder distributor and other components in the pulverizing system, and reduction of the effective temperature of the SCR catalyst. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a method for improving the SCR inlet temperature based on a rare earth motor and a dynamic separator during the deep peak shaving of a unit.

[0005] The technical scheme of the present application is as follows: A method for controlling the SCR inlet flue gas temperature of a coal mill based on variable frequency regulation, comprising the following steps: Step 1, the design reference speed of the coal mill is n, and the coal quantity under a specific load of the coal mill is M; wherein the coal quantity M value is obtained from the operating parameters of the coal feeder 3, and the design speed of the dynamic separator is R; Step 2, under the condition that the boundary conditions are consistent, test the coal fineness of the pulverizing system under different speeds n of the coal mill, and give the recommended speed under different coal quantities; Step 2.1, for the design speed n, the design coal quantity M, and the design speed R of the dynamic separator, the loading mode is spring loading, the total primary air quantity of the coal mill is controlled by the hot primary air damper of the coal mill, the outlet temperature of the coal mill is controlled by the cold primary air damper of the coal mill, and the coal fineness of the coal mill outlet is controlled by the speed of the coal mill and the speed of the dynamic separator at the outlet of the coal mill; Step 2.2: After the adjustments in Step 2.1, conduct variable speed tests with different coal quantities for the same type of coal to determine the recommended speed for that coal quantity. The purpose of the tests is to set the recommended speed N for different coal quantities. M ; Step 2.2.1: Under each operating condition, the normal state of the coal mill is determined by monitoring the magnitude of the local vibration value and the amount of stone coal discharged. Step 2.2.2: Under various operating conditions, record the operating parameters of the pulverizing system during that period using a DCS or PI system; the mill speed is always maintained at the recommended speed N. M ; Step 3: Under consistent boundary conditions, conduct coal powder fineness tests on the pulverizing system at different dynamic separator speeds. Step 3.1: For a design coal quantity of M and a recommended rotational speed of N... M The dynamic separator is designed with a rotational speed of R, and is spring-loaded. The total primary air volume of the coal mill is controlled by the hot primary air regulating damper, while the outlet temperature of the coal mill is controlled by the cold primary air damper. The rotational speed of the coal mill and the rotational speed of the dynamic separator at the coal mill outlet jointly control the fineness of the pulverized coal at the coal mill outlet. Step 3.2: After the adjustments in Step 3.1, conduct dynamic separator speed variation tests for the same type of coal with different coal quantities. The purpose of the tests is to explore the recommended mill speed N for different coal quantities M. M The relationship between pulverized coal fineness and dynamic separator rotation speed under certain conditions; Step 3.2.1: Under each operating condition, the normal state of the coal mill is determined by monitoring the magnitude of the local vibration value and the amount of stone coal discharged. Step 3.2.2: Under each operating condition, slowly adjust the rotation speed R of the dynamic separator and test the fineness of the pulverized coal; calculate the fineness of the pulverized coal under this operating condition by weighted average (the fineness of each pulverized coal tube is tested separately and then the weighted average is taken), and record the operating parameters of the pulverizing system during this period through the DCS or PI system. Step 4: Under low-load boiler operation (deep peak shaving), switch between different coal mill combinations, and based on the coal quantity of the coal mills, adjust the recommended speed N. M Based on the coal powder fineness test results in step 3, the rotation speed R of the dynamic separator was changed to obtain the SCR inlet flue gas temperature curves under different coal quantities and different dynamic separator rotation speeds, and the operating parameters of the pulverizing system during this period were recorded by the DCS or PI system.

[0006] Furthermore, step 2 specifically includes: For the same type of coal, variable speed tests were conducted under different coal quantities. The speeds were set to 0.8n, 0.9n, 1.0n, 1.1n, and 1.2n. The purpose of the tests was to determine the recommended speed N for different coal quantities. M At the corresponding coal mill speed N M Under these conditions, the fineness R of pulverized coal 90 When the rotational speed is maintained within the range of 18% to 25%, it is considered to be the recommended rotational speed under the current coal quantity.

[0007] Furthermore, step 3 specifically involves: For the same type of coal, the mill speed is set to the recommended speed N for the current coal quantity. M A dynamic separator speed R test was conducted, with the dynamic separator speeds set to 0.8R, 0.9R, 1.0R, 1.1R, and 1.2R. The purpose of the test was to determine the optimal speeds (N, N) at which the dynamic separator could operate at the corresponding coal mill speeds. M Under these circumstances, the relationship between pulverized coal fineness and dynamic separator rotation speed was investigated to establish a theoretical basis for subsequent adjustments.

[0008] Furthermore, step 4 specifically involves: For the same type of coal, under low boiler load conditions (deep peak shaving), the average coal quantity of the grinding group and coal mill is determined first, and the coal mill speed is set to the recommended speed N under the current coal quantity. M The relationship between the SCR inlet flue gas temperature and the dynamic separator speed was explored by changing the dynamic separator speed. The dynamic separator speed was initially set to a speed range corresponding to a coal powder fineness R90 of 18% to 20%, and then the speed was slowly reduced to establish a curve showing the relationship between the dynamic separator speed and the SCR inlet flue gas temperature, and to find the highest point of flue gas temperature.

[0009] Furthermore, in steps 2, 3, and 4, the outlet temperature of the coal mill is set to 80℃ by adjusting the cold primary air at the inlet of the coal mill.

[0010] Furthermore, in steps 2, 3, and 4, the outlet air volume of the coal mill is adjusted to the corresponding operating value of the air-coal ratio curve by adjusting the hot primary air regulating valve at the inlet of the coal mill, while the primary air volume offset at the inlet of the coal mill is set to 0t / h.

[0011] Furthermore, when slowly adjusting the coal feed rate of the coal feeder in steps 2, 3, and 4, the small adjustment indication in the coal feed rate adjustment control panel is used, and each adjustment of the coal feed rate is approximately 0.5 t / h; the coal feed rate of the coal feeder is calibrated periodically.

[0012] Furthermore, the stable operating parameters of the pulverizing system set in steps 2, 3, and 4 shall be stable for at least 1 hour, the coal powder fineness test time shall be no less than 2 hours, and the coal powder fineness standard shall be R90.

[0013] Furthermore, the operating parameters of the pulverizing system in steps 2, 3, and 4 include the coal feed rate, pulverizer current, mill bowl differential pressure, primary air volume, primary air temperature, hot and cold air damper opening, pulverizer outlet temperature, and average hourly value of stone coal discharge.

[0014] Compared with existing technologies, the beneficial effects of this solution are: 1) This invention provides a method for controlling and adjusting the fineness of coal powder in a coal mill based on a rare earth motor and a dynamic separator during deep peak shaving of a power unit. This method can not only effectively solve the problem that the fineness of coal powder in the coal mill affects boiler combustion during the operation of the unit, but also reduce the power consumption of the coal mill by using the frequency conversion regulation method of the rare earth motor, thus playing a role in energy saving and emission reduction. 2) By coupling the frequency conversion regulation of the rare earth motor and the speed regulation of the dynamic separator, not only can the fineness of the coal powder in the coal mill be adjusted efficiently, but the denitrification efficiency can also be improved by adjusting the flue gas temperature at the SCR inlet. Furthermore, this measure can improve the boiler combustion efficiency under low load, making the entire system operate more efficiently. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the powder-making system of the present invention; Figure 2 The curves showing the relationship between SCR inlet flue gas temperature and dynamic separator rotation speed under different grinding groups according to the present invention are shown. Detailed Implementation

[0016] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0017] like Figure 1 As shown, the pulverizing system includes: a frequency converter control unit 1, a rare earth motor 2, a coal feeder 3, a coal mill 4, a dynamic separator 5, a coal mill outlet pulverized coal pipe 6, a cold primary air regulating valve 7, a hot primary air regulating valve 8, and a pulverized coal sampling hole 9; the coal mill outlet pulverized coal pipe 6 is equipped with a coal pulverized coal sampling hole 9; the frequency converter control unit 1 is electrically connected to the rare earth motor 2, and the rare earth motor 2 is electrically connected to the coal mill 4; the coal feeder 3 is connected to the coal mill 4; a dynamic separator 5 is arranged at the outlet of the coal mill 4, and the dynamic separator 5 is connected to the coal mill outlet pulverized coal pipe 6, which is equipped with a coal pulverized coal sampling hole 9; primary air is regulated and blown into the coal mill 4 through the cold primary air regulating valve 7 and the hot primary air regulating valve 8, driving pulverized coal into the coal mill outlet, and after being screened by the dynamic separator, it enters the outlet pulverized coal pipe 6. The pulverizing system is equipped with a frequency converter, which has a remote control signal interface. The frequency converter control unit 1 controls the frequency converter, which drives the rare earth motor 2, which in turn drives the coal mill 4 to rotate.

[0018] When the pulverizing system is running, raw coal enters the coal mill 4 from the coal feeder 3, the coal mill 4 is driven to rotate by the rare earth motor 2 and the frequency conversion control unit 1, the cold primary air adjusting door 7 and the hot primary air adjusting door 8 adjust the primary air blown into the coal mill 4, wherein the cold primary air adjusting door 7 controls the mixed air temperature of the primary air, and the hot primary air adjusting door 8 controls the amount of primary air entering the coal mill. After the raw coal is ground into coal powder by the grinding roller of the coal mill 4, the coal powder is carried by the primary air to pass through the dynamic separator 5, and the coal powder with a suitable fineness passes through the screening of the dynamic separator 5, enters the outlet pipeline of the coal mill, and enters the furnace with the primary air, while the coal powder with a coarse fineness is blocked by the dynamic separator 5 and re-enters the coal mill 4 for grinding.

[0019] The embodiment one of the application provides a method for controlling the SCR inlet flue gas temperature based on frequency conversion adjustment of a coal mill. Step 1, the reference speed of the coal mill 4 is designed as n, and the coal amount under a specific load of the coal mill 3 is designed as M; wherein the coal amount M value is obtained from the operation parameters of the coal feeder 3, and the dynamic separator speed is designed as R; Step 2, under the condition that the boundary conditions are consistent, the coal mill coal fineness test experiment of the pulverizing system under different speeds n is performed, and the recommended speed under different coal amounts is given; Step 2.1, for the design speed n, the design coal amount M, and the design dynamic separator speed R, the loading mode is spring loading, the total primary air amount of the coal mill is controlled by the hot primary air adjusting door 8 of the coal mill, and the outlet temperature of the coal mill 4 is controlled by the cold primary air adjusting door 7 of the coal mill. The coal mill coal fineness is controlled according to the speed of the coal mill and the speed of the dynamic separator 5 at the outlet of the coal mill. Step 2.2, after the adjustment in step 2.1, the variable speed test under different coal amounts is performed for the same coal, the speed is set as 0.8n, 0.9n, 1.0n, 1.1n, 1.2n, and the test purpose is to set the recommended speed N under different coal amounts. M When the coal fineness R90 is kept in the range of 18% to 25% under the corresponding coal mill speed, it is considered that the speed is the recommended speed under the current coal amount; Step 2.2.1, under each working condition, whether the coal mill reaches the normal state is judged by monitoring the in-situ vibration value and the stone coal discharge amount of the coal mill. Step 2.2.2, under each working condition, the operation parameters of the pulverizing system in the period are recorded by the DCS or PI system; wherein the speed of the coal mill is always kept as the recommended speed N. M ; Step 3, under the condition that the boundary conditions are consistent, the coal mill coal fineness test experiment of the pulverizing system under different dynamic separator speeds is performed. Step 3.1: For a design coal quantity of M and a recommended rotational speed of N... M The dynamic separator is designed with a rotational speed of R, and the loading method is spring loading. The total primary air volume of the coal mill is controlled by the hot primary air regulating baffle 8; the outlet temperature of the coal mill 4 is controlled by the cold primary air baffle 7. The fineness of the coal powder in the coal mill is controlled according to the rotational speed of the coal mill and the rotational speed of the dynamic separator 5 at the coal mill outlet. Step 3.2: After the adjustments in Step 3.1, conduct dynamic separator speed variation tests for the same coal type under different coal quantities. The speeds are set to 0.8R, 0.9R, 1.0R, 1.1R, and 1.2R. The purpose of the tests is to explore the recommended mill speed N for different coal quantities. M The relationship between pulverized coal fineness and dynamic separator rotation speed under certain conditions; Step 3.2.1: Under each operating condition, the normal state of the coal mill is determined by monitoring the magnitude of the local vibration value and the amount of stone coal discharged. Step 3.2.2: Under each operating condition, slowly adjust the rotational speed R of the dynamic separator 5. At five speed levels (0.8R, 0.9R, 1.0R, 1.1R, and 1.2R), sequentially sample the coal powder at the coal powder sampling port 6 at the coal mill outlet pipe to test the fineness of the coal powder. Calculate the fineness of the coal powder under this operating condition using a weighted average, and record the operating parameters of the pulverizing system during this period using a DCS or PI system. The coal mill speed should always be maintained at the recommended speed N. M ; Step 4: Under low-load boiler operation (deep peak shaving), switch between different coal mill combinations, and based on the coal quantity of the coal mills, adjust the recommended speed N. M Based on the coal powder fineness test results in step 3, the rotation speed R of the dynamic separator 5 was changed to obtain the SCR inlet flue gas temperature curves under different coal quantities and different dynamic separator rotation speeds.

[0020] Based on Embodiment 1, Embodiment 2 of this application provides an application of the method for controlling the SCR inlet flue gas temperature of a coal mill based on rare earth motor frequency conversion regulation in Embodiment 1 in a power plant: The boiler is a 1000MW ultra-supercritical opposed-flow boiler, and the corresponding coal mill has a design speed of 25.6 r / min and a design minimum coal output of 25.1 t / h. Specific coal mill parameters are shown in Table 1 below. Table 1. Coal Mill Parameter Table ; The parameters of the rare-earth permanent magnet motor used are shown in Table 2 below: Table 2 Parameter Table of Rare Earth Permanent Magnet Motor ; Step 1, the reference speed of the coal mill is designed to be 30.8 r / min, and the coal quantity of the coal mill during the deep peak regulation period (load rate 20%~30%) is designed to be 40t / h~60t / h; wherein the coal quantity value is obtained from the running parameters of the coal feeder, and the dynamic separator speed is designed to be 25.6r / min; under the same coal, the coal fineness test under different speeds is carried out, and the recommended speed N M .

[0021] Further, the corresponding recommended speed N M is sought under the coal quantity of 40t / h, 50t / h and 60t / h. When the coal fineness R90 under the corresponding speed is in the interval of 18%~25%, and the coal mill does not appear abnormal, it is determined that the speed is the recommended speed under the current coal quantity. The recommended speed is not a specific value, that is, the speed under which the coal fineness R90 meets the requirements can be used as the recommended speed.

[0022] Table 3: Test results of coal quantity and coal fineness of the coal mill under different coal quantities ; Step 2, the coal quantity of the coal mill during the deep peak regulation period (load rate 20%~30%) is designed to be 40t / h~60t / h; wherein the coal quantity value is obtained from the running parameters of the coal feeder, and the speed of the coal mill refers to the recommended speed corresponding to the coal quantity in step 1, and the speed of the dynamic separator is initially 25.6r / min, which is slowly adjusted, and the coal fineness test is carried out in turn.

[0023] Table 4: Test results of coal quantity and coal fineness of the coal mill under different coal quantities ; Further, since the furnace heat load is low under the low load of the unit, which leads to the low SCR inlet flue gas temperature, the operation of the coal mill combination and the coal fineness need to be considered at the same time. Usually, the coal fineness is recommended to be set to a coarser state than the fineness during normal operation.

[0024] Step 3, based on the coal fineness test results in step 2, different coal mill combinations (bottom layer mill and middle layer mill combination) are switched, and based on the running coal quantity of the coal mill, the speed of the dynamic separator is changed under the recommended speed N M , to obtain the SCR inlet flue gas temperature curve. At the same time, combined with other running parameters, the most suitable coal mill combination and dynamic separator speed are selected.

[0025] As shown in Figure 2 , the relationship curve of the SCR inlet flue gas temperature based on the recommended speed N M of the coal mill with the coal mill combination and the dynamic separator is given when two coal mills are operated under 20% load, and the average coal quantity of each coal mill is about 60t / h.

[0026] The results of the embodiment show that: 1) when the unit is running at 20% load with the bottom layer coal mill selected, the dynamic separator speed is set to about 21 r / min, the SCR inlet flue gas temperature can be raised to a maximum of about 298°C, and the pulverized coal fineness R90 is about 30% at this time; 2) when the unit is running at 20% load with the middle layer coal mill selected, the dynamic separator speed is set to about 23 r / min, the SCR inlet flue gas temperature can be raised to a maximum of about 310°C, and the pulverized coal fineness R90 is about 27% at this time; 3) the bottom layer mill needs to be set to a lower dynamic separator speed, i.e. coarser pulverized coal, than the middle layer mill, and too coarse pulverized coal fineness will affect the burnout and stable combustion of the pulverized coal to some extent, and it is suggested to run with the middle layer mill group under the premise of considering safety and economy.

[0027] At the same time, if the unit load and coal quantity are changed, the appropriate dynamic separator speed range can be retested according to the above steps.

[0028] The above embodiment is only a preferred embodiment of the present application, and is not a limitation on the technical solutions of the present application, and any technical solution that can be realized on the basis of the above embodiment without creative labor should be considered to fall within the protection scope of the present application patent.

Claims

1. A method for regulating the SCR inlet flue gas temperature based on frequency conversion of a coal mill, characterized in that, The coal fineness is coarsely adjusted by adjusting the rotating speed of the coal mill (4) and the rotating speed of the dynamic separator (5) through the rare earth motor (2) and the frequency control unit (1), so as to improve the SCR inlet flue gas temperature; the method comprises the following steps: Step 1: the reference rotating speed of the coal mill (4) is designed as n, the coal quantity of the coal mill is designed as M, wherein the coal quantity M is obtained from the operating parameters of the coal feeder (3), and the rotating speed of the dynamic separator is designed as R; Step 2, under the condition of consistent boundary conditions, the coal pulverizing system is tested for coal fineness at different rotational speeds n of the coal mill, and the recommended rotational speed N under different coal quantities is given M ; Step 3: under the condition that the boundary conditions are consistent, the coal mill coal fineness of the coal pulverizing system under different dynamic separator rotating speeds is tested; Step 4, under the boiler depth peak shaving, switch different mill combination, and based on the coal quantity of mill operation, recommend the speed N M Next, based on the test results of the coal fineness in step 3, change the speed of the dynamic separator (5), obtain the SCR inlet flue gas temperature curve under different coal quantities and different dynamic separator speeds, and record the operating parameters of the pulverizing system in this period of time through the DCS or PI system.

2. A method for regulating the SCR inlet flue gas temperature by varying the frequency of the coal mill as claimed in claim 1, wherein, The step 2 is specifically as follows: Step 2.1: for the design rotating speed n, the design coal quantity M and the design dynamic separator rotating speed R, the spring loading mode is adopted, the total primary air quantity of the coal mill (4) is controlled by the hot primary air damper (8) of the coal mill, the outlet temperature of the coal mill (4) is controlled by the cold primary air damper (7) of the coal mill, and the coal mill outlet coal fineness is controlled by the rotating speed of the coal mill and the rotating speed of the dynamic separator (5) at the outlet of the coal mill; Step 2.2: for the same coal, the dynamic separator rotating speed is set as the design rotating speed R, the variable rotating speed test under different coal quantities is carried out, the rotating speed is set as 0.8n, 0.9n, 1.0n, 1.1n and 1.2n, and when the coal fineness R90 is kept in the range of 18% to 25% under the corresponding coal mill rotating speed, the rotating speed is considered as the recommended rotating speed under the current coal quantity; Step 2.3, under each condition, whether the mill reaches the normal state is judged by monitoring the mill in-situ vibration value size and stone coal discharge, and the operation parameters of the pulverizing system in this period are recorded through DCS or PI system, wherein the mill speed is always kept at the recommended speed N M The normal state means that the in-situ vibration value and stone coal discharge do not exceed the alarm value.

3. A method for regulating the SCR inlet flue gas temperature by adjusting the coal mill based on frequency conversion according to claim 2, characterized in that, The step 3 is specifically as follows: Step 3.1, for the design coal amount M, the recommended rotating speed N M , the design dynamic separator rotating speed R, the loading mode is spring loading, the total primary air amount of the coal mill is controlled by the hot primary air damper (8) of the coal mill, the outlet temperature of the coal mill (4) is controlled by the cold primary air damper (7) of the coal mill, and the coal powder fineness of the coal mill outlet is controlled by the rotating speed of the coal mill and the rotating speed of the dynamic separator (5) at the outlet of the coal mill. Step 3.2, for the same coal type, set the speed of the coal mill to the recommended speed N under the current coal amount M , perform the dynamic separator speed R test, and set the dynamic separator speed to 0.8R, 0.9R, 1.0R, 1.1R, 1.2R; Step 3.3: under each working condition, whether the coal mill reaches the normal state is judged by monitoring the local vibration value and the stone coal emission quantity of the coal mill; the rotating speed R of the dynamic separator (5) is slowly adjusted, the coal fineness is tested, the coal fineness under the working condition is obtained by weighted calculation, and the operating parameters of the coal pulverizing system in the period are recorded through the DCS or PI system, wherein the normal state refers to that the local vibration value and the stone coal emission quantity do not exceed the alarm value.

4. A method for regulating the SCR inlet flue gas temperature by adjusting the coal mill based on frequency conversion according to claim 3, characterized in that, The step 4 is specifically as follows: For the same coal, in the case of deep peak shaving of the boiler, the average coal quantity of the mill group and the coal mill is determined first, and the rotational speed of the coal mill is set as the recommended rotational speed N under the current coal quantity M The relationship between the SCR inlet flue gas temperature and the dynamic separator rotational speed is analyzed by changing the dynamic separator rotational speed, the dynamic separator rotational speed is initially set as the rotational speed interval corresponding to the pulverized coal fineness R90 of 18%~20%, then the rotational speed is slowly reduced, the relationship curve between the dynamic separator rotational speed and the SCR inlet flue gas temperature is established, and the highest point of the flue gas temperature is sought.

5. A method for regulating the SCR inlet flue gas temperature by varying the frequency of the coal pulverizer as claimed in claim 1, wherein, In the steps 2, 3 and 4, the outlet temperature of the coal mill (4) is set at 80 DEG C through the coal mill inlet cold primary air adjusting door (7), and the outlet air quantity of the coal mill (4) is adjusted to the corresponding air-coal ratio curve operating value through the coal mill inlet hot primary air adjusting door (8), and meanwhile, the coal mill inlet primary air quantity is set as 0 t / h.

6. A method of regulating the SCR inlet flue gas temperature by varying the frequency of the coal mill as claimed in claim 1, wherein, In the steps 2, 3 and 4, when the coal quantity of the coal feeder (3) is slowly adjusted, the small adjustment instruction in the coal quantity adjusting control panel is adopted, the coal quantity is adjusted by 0.5 t / h each time, the coal quantity of the coal feeder (3) is periodically calibrated, the stable length of the set operating parameters of the coal pulverizing system is at least 1 h, the coal fineness testing length is not less than 2 h, and the coal fineness standard is R90.

7. A method of regulating the SCR inlet flue gas temperature by varying the frequency of the coal mill as claimed in claim 1, wherein, In the steps 2, 3 and 4, the operating parameters of the coal pulverizing system include the coal quantity, the coal mill current, the bowl differential pressure, the primary air quantity, the primary air temperature, the cold and hot air door opening degree, the coal mill outlet temperature and the stone coal emission quantity average value.

8. A method of regulating the SCR inlet flue gas temperature by varying the frequency of the coal mill as claimed in claim 1, wherein, The pulverizing system comprises a frequency conversion control unit (1), a rare earth motor (2), a coal feeder (3), a coal mill (4), a dynamic separator (5), a coal mill outlet powder pipe (6), a cold primary air adjusting door (7), a hot primary air adjusting door (8) and a coal powder sampling hole (9).

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