Blast furnace coal injection system and powder returning method

Abstract

The invention relates to a blast furnace coal injection system and a powder returning method, and belongs to the technical field of blast furnace ironmaking. The blast furnace coal injection system comprises a raw coal bunker, a coal feeder, a coal mill, a pulverized coal collector, a pulverized coal bunker, an injection tank and a pulverized coal distributor which are connected in sequence. The system is characterized in that a pulverized coal return header pipe is arranged between the injection tank and the coal feeder, a stop valve is arranged on the pulverized coal return header pipe, and the pulverized coal return header pipe enables an outlet of the injection tank to be communicated with the coal feeder and is used for returning stored pulverized coal in the pulverized coal bunker to the coal mill to be ground and heated again, so that good flowability of the pulverized coal is ensured. According to the powder returning method, when the blast furnace stops coal injection (such as blast furnace damping down maintenance), stored coal powder in the coal powder bin is returned to the coal feeder in a pneumatic conveying mode, and the fluidity of the coal powder and stable operation of the system are guaranteed. The system and the method effectively solve the problem of unstable conveying caused by low temperature and poor fluidity of the pulverized coal, prevent pipeline blockage, improve the utilization rate of the pulverized coal and the safety of the system, and are simple to operate and easy to realize automatic transformation.

Description

Technical Field

[0001] The invention belongs to the technical field of blast furnace ironmaking and relates to a blast furnace coal injection system and a coal powder returning method. Background Art

[0002] As the most effective way to replace metallurgical coke in the blast furnace smelting process, blast furnace coal injection is widely used by steel companies. This technology can not only reduce the consumption of blast furnace coke, but also improve the blast furnace working conditions as a means of adjusting the lower part of the blast furnace smelting, providing favorable conditions for the blast furnace to use high wind temperature and high oxygen enrichment.

[0003] Blast furnace coal injection adopts pneumatic conveying to transport the coal powder in the injection tank to the spray gun at the blast furnace tuyere through nitrogen or compressed air. Production practice shows that in the process of pneumatic conveying, the fluidity of coal powder determines the stability of the conveying process, and the temperature of coal powder has a significant effect on its fluidity. Studies have shown that changes in coal powder temperature will affect the evaporation and condensation of water in coal powder, and the water in coal powder will form a thin film, increase the cohesion between coal powder particles, thereby reducing the fluidity of coal powder, so the water content of coal powder has a significant effect on its fluidity. When the temperature of coal powder is high, the water in coal powder is easy to evaporate, which can improve its fluidity; when the temperature of coal powder is low or in a humid environment, the water is easy to condense and precipitate, increasing the water content in coal powder, thereby reducing its fluidity.

[0004] At present, in the production process of the blast furnace coal injection system, the coal powder produced by the pulverizer is stored in the coal powder bin, and its temperature is controlled between 75 and 100 ° C, and the minimum temperature must be higher than the dew point temperature, so as to ensure that moisture does not condense and precipitate, and to ensure the fluidity of the coal powder. However, in the actual production process, if the blast furnace is shut down for a long time for maintenance, the qualified coal powder produced by the coal injection system will be stored in the coal powder bin for a long time. When the blast furnace is re-blown, the coal powder may be in a low temperature and poor fluidity and cannot be stably transported to the blast furnace. In severe cases, it will cause the coal powder pipeline to be blocked and cause certain environmental pollution. By consulting relevant literature, it can be seen that the patent "A Coal Powder Returning Process and System" (Application No. 201710273453.5) mainly solves the scheduling problem of surplus coal powder between various coal injection systems, but does not involve the problem of poor transportation caused by the low temperature and poor fluidity of the stock coal powder. Summary of the invention

[0005] In view of this, the object of the present invention is to solve the above-mentioned problems and provide a blast furnace coal injection system and a coal powder return method.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A blast furnace coal injection system comprises a raw coal bunker, a coal feeder, a coal mill, a coal powder collector, a coal powder bunker, a blowing tank and a coal powder distributor which are connected and arranged in sequence along the flow direction of the coal powder medium; the coal mill is also connected to a flue gas furnace, the coal powder collector is connected to a coal powder blower, the blowing tank is connected to a pressurization main pipe, and the outlet of the blowing tank is connected to an air replenisher, characterized in that a powder return main pipe is also provided between the blowing tank and the coal feeder, and a powder return main pipe cut-off valve is provided on the powder return main pipe; the powder return main pipe connects the outlet of the blowing tank with the coal feeder, and is used to transport the stock coal powder in the coal powder bunker to the coal feeder by pneumatic conveying, and then enters the coal mill for further grinding and heating to ensure good fluidity of the coal powder.

[0008] Furthermore, the spray tanks are arranged in parallel with one or more of them, and the outlet of each spray tank is connected to the powder return main pipe via a powder return branch pipe, and each powder return branch pipe is provided with a powder return branch pipe cut-off valve.

[0009] Furthermore, the injection tank outlet shut-off valve, the air supply device, and the injection main pipe shut-off valve are sequentially arranged on the connecting pipeline between the injection tank and the coal powder distributor along the coal powder conveying direction; the return powder branch pipe is connected between the air supply device and the injection main pipe shut-off valve; the air supply device is connected to the air supply main pipe through the air supply branch pipe, and the air supply branch pipe is provided with an air supply branch pipe shut-off valve.

[0010] Furthermore, the pressurized main pipe is connected to the spray tank via a pressurized branch pipe; a pressurized main pipe flow regulating valve is provided on the pressurized main pipe, and a pressurized branch pipe cut-off valve is provided on the pressurized branch pipe.

[0011] Furthermore, pressure gauges are provided on the pulverized coal return main pipe and the injection tank; a thermometer is provided on the cone of the pulverized coal bin; and a coal cut-off valve under the injection tank is provided between the outlet of the pulverized coal bin and the inlet of the injection tank.

[0012] A method for returning pulverized coal to a blast furnace coal injection system. When the blast furnace is not in a coal injection state (such as a blast furnace shutdown for maintenance), when the temperature of the pulverized coal bin cone meets TE X -TE Set When ≤ΔT, the outlet of the injection tank is connected to the coal feeder, and the stored pulverized coal in the pulverized coal bin is transported to the coal feeder by pneumatic conveying, and then enters the coal mill for re-grinding and heating, and the pulverizing operation is performed to ensure good fluidity of the pulverized coal;

[0013] Among them, TE X is the measured temperature of the cone of the pulverized coal bin; TE Set is the temperature setting value of the cone of the pulverized coal bin, and ΔT is the manually set value.

[0014] Further, using the blast furnace coal injection system as described above, the powder return operation steps are as follows:

[0015] The first step is to open the coal shut-off valve at the bottom of the injection tank, load the pulverized coal in the pulverized coal bin into the injection tank, and then close the coal shut-off valve at the bottom of the injection tank after the pulverized coal in the injection tank is loaded;

[0016] The second step is to open the pressure branch pipe cut-off valve and the pressure main pipe flow regulating valve to pressurize the spray tank after the powder is loaded. Wait until the pressure reaches the initial set pressure PT. Set When the pressure branch pipe cut-off valve and the pressure main pipe flow regulating valve of the spray tank are closed;

[0017] The third step is to sequentially close the shut-off valve of the injection main corresponding to the injection tank, open the shut-off valve of the return powder branch pipe, open the shut-off valve of the return powder main pipe, open the shut-off valve of the air supply branch pipe, and open the shut-off valve of the injection tank outlet, and return the pulverized coal in the injection tank to the turbine housing of the running coal feeder by pneumatic conveying.

[0018] Further, in the third step, when the pressure at the end of the powder return main pipe meets |PT CX -PT CSet When ∣<ΔP, open the cut-off valve of the pressurized branch pipe and linearly adjust the opening degree K of the flow regulating valve of the pressurized main pipe PN =K PNi +αU P , gradually open the flow regulating valve of the pressurized main pipe; when the pressure at the end of the return powder main pipe ∣PT CX -PT CSet When ∣=ΔP, the opening degree K of the pressure main flow regulating valve is maintained PN unchanged; when the pressure at the end of the powder return main pipe ∣PT CX -PT CSet When ∣>ΔP, the opening degree K of the pressure main flow control valve is linearly adjusted. PN =K PNi -αU P , gradually reduce the opening of the flow regulating valve of the pressurized main pipe until the pressure at the end of the return powder main pipe reaches PT CX -PT CSet When ∣=ΔP, the opening degree K of the pressure main flow regulating valve is maintained PN constant;

[0019] Among them, ΔP is the manually set value; PT, PT C They are the measured pressure values ​​at the end of the spray tank and the powder return main pipe; PT CSet K is the set value of the pressure at the end of the powder return main pipe; PN K is the measured value of the opening of the flow control valve of the pressurized main pipe; PNi is the initial value of the opening of the pressure main flow control valve; α is the valve opening adjustment coefficient of the pressure main flow control valve, which is manually set according to the actual working conditions and has a value range of 0 to 100 integers; U P It is the smallest regulating unit of the pressurized main flow control valve.

[0020] Furthermore, the pressure setting value PT of the spray tank Set , manually input and set on the control system, the value range is 100kPa ~ 500kPa; the pressure setting value PT at the end of the return powder main pipe CSet , is manually input and set on the control system, and the value range is 0kPa~100kPa; the difference ΔP between the actual measured value of the pressure at the end of the return powder main pipe and the set pressure is manually input and set on the control system, and the value range is 0kPa~50kPa.

[0021] Furthermore, the temperature setting value TE of the cone of the pulverized coal bin is Set , which is manually input and set on the control system, and the value range is 45℃~90℃; the difference ΔT between the actual temperature of the cone of the pulverized coal bin and the set temperature is manually input and set on the control system, and the value range is 0℃~20℃.

[0022] The beneficial effects of the present invention are:

[0023] 1) The present invention utilizes the pneumatic conveying system of the coal injection system itself to return the stock pulverized coal in the pulverized coal bin to the coal feeder, which can effectively solve the problem that the stock pulverized coal cannot be stably conveyed due to poor fluidity due to low temperature, thereby improving the utilization efficiency of pulverized coal;

[0024] 2) The present invention can effectively prevent the phenomenon of coal powder main pipe being blocked due to poor coal powder fluidity, thereby improving the safety of system equipment;

[0025] 3) The system of the present invention is simple, technically reliable, easy to implement, and has low investment cost;

[0026] 4) The present invention is easy to transform the existing blast furnace coal injection system and has a wide range of applications.

[0027] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0029] Figure 1 It is the principle diagram of the blast furnace coal injection system in the present invention.

[0030] Figure numerals: 1-raw coal bunker; 2-coal feeder; 3-pressure gauge at the end of the return coal main pipe; 4-shut-off valve of the return coal main pipe; 5-return coal main pipe; 6-flue gas furnace; 7-coal pulverizer; 8-coal powder collector; 9-coal powder bunker; 10-A spray tank lower coal shut-off valve; 11-A spray tank pressure gauge; 12-A spray tank; 13-A spray tank pressurization branch shut-off valve; 14-pressurization main pipe flow regulating valve; 15-A spray tank air supply branch shut-off valve; 16-A spray tank return coal branch shut-off valve; 17-A spray tank return coal branch; 18-A spray tank outlet Inlet cut-off valve; 19-A injection tank air replenisher; 20-A injection main pipe cut-off valve; 21-B injection tank air replenishment branch pipe cut-off valve; 22-B injection tank pressurization branch pipe cut-off valve; 23-B injection tank return powder branch pipe cut-off valve; 24-B injection tank return powder branch; 25-B injection main pipe cut-off valve; 26-B injection tank air replenisher; 27-B injection tank outlet cut-off valve; 28-B injection tank; 29-B injection tank pressure gauge; 30-B injection tank lower coal cut-off valve; 31-coal powder bin cone thermometer; 32-coal powder fan; 33-coal powder distributor. DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0032] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0033] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0034] See also Figure 1 , which is a blast furnace coal injection system, including a raw coal bunker 1, a coal feeder 2, a coal mill 7, a coal powder collector 8, a coal powder bunker 9, a blowing tank, and a coal powder distributor 33 which are sequentially connected and arranged along the coal powder conveying direction; the coal mill 7 is also connected to a flue gas furnace 6, the coal powder collector 8 is connected to a coal powder fan 32, the blowing tank is connected to a pressurization main pipe, and the outlet of the blowing tank is connected to an air replenisher, characterized in that: a powder return main pipe 5 is also provided between the blowing tank and the coal feeder 2, and a powder return main pipe cut-off valve 4 is provided on the powder return main pipe 5; the powder return main pipe 5 connects the outlet of the blowing tank with the coal feeder 2, and is used to transport the stock coal powder in the coal powder bunker 9 to the coal feeder 2 by pneumatic conveying, and then enters the coal mill 7 for grinding and heating again, so as to ensure good fluidity of the coal powder.

[0035] There are two spray tanks, A spray tank 12 and B spray tank 28, which are arranged in parallel. The outlet of A spray tank 12 is connected to the powder return main pipe 5 through A spray tank powder return branch pipe 17, and A spray tank powder return branch pipe 17 is provided with A spray tank powder return branch pipe cut-off valve 16. The outlet of B spray tank 28 is connected to the powder return main pipe 5 through B spray tank powder return branch pipe 24, and B spray tank powder return branch pipe 24 is provided with B spray tank powder return branch pipe cut-off valve 23.

[0036] On the connecting pipeline between the A blowing tank 12 and the coal powder distributor 33, the A blowing tank outlet shut-off valve 18, the A blowing tank air replenisher 19, and the A blowing main pipe shut-off valve 20 are arranged in sequence along the coal powder conveying direction; the A blowing tank powder return branch pipe 17 is connected between the A blowing tank air replenisher 19 and the A blowing main pipe shut-off valve 20; the A blowing tank air replenisher 19 is connected to the air replenishment main pipe through the A blowing tank 12 air replenishment branch pipe, and the A blowing tank 12 air replenishment branch pipe is installed with the A blowing tank air replenishment branch pipe shut-off valve 15. On the connecting pipeline between the B blowing tank 28 and the coal powder distributor 33, the B blowing tank outlet shut-off valve 27, the B blowing tank air replenisher 26, and the B blowing injection main shut-off valve 25 are arranged in sequence along the coal powder conveying direction; the B blowing tank powder return branch pipe 24 is connected between the B blowing tank air replenisher 26 and the B blowing main shut-off valve 25; the B blowing tank air replenisher 26 is connected to the air replenishment main pipe through the B blowing tank 28 air replenishment branch pipe, and the B blowing tank 28 air replenishment branch pipe is installed with a B blowing tank air replenishment branch shut-off valve 21.

[0037] The pressure main pipe is connected to the A spray tank 12 through the pressure branch pipe of the A spray tank 12; a pressure main pipe flow regulating valve 14 is installed on the pressure main pipe, and an A spray tank pressure branch pipe cut-off valve 13 is installed on the pressure branch pipe of the A spray tank 12. The pressure main pipe is connected to the B spray tank 28 through the pressure branch pipe of the B spray tank 28; a B spray tank pressure branch pipe cut-off valve 22 is installed on the pressure branch pipe of the B spray tank 28.

[0038] A pressure gauge 3 at the end of the powder return main pipe 5 is installed, an A blowing tank pressure gauge 11 is installed on the A blowing tank 12, and a B blowing tank pressure gauge 29 is installed on the B blowing tank 28; a pulverized coal bin cone thermometer 31 is installed at the cone of the pulverized coal bin 9; an A blowing tank lower coal shut-off valve 10 is installed between the outlet of the pulverized coal bin 9 and the inlet of the A blowing tank 12, and a B blowing tank lower coal shut-off valve 30 is installed between the outlet of the pulverized coal bin 9 and the inlet of the B blowing tank 28.

[0039] A method for returning coal powder to the blast furnace coal injection system based on the present embodiment, when the blast furnace is in a state of wind down maintenance for ≥ 10 hours, and the flue gas furnace 6, coal feeder 2, coal mill 7, coal powder collector 8 and coal powder fan 32 of the pulverizing system are in normal operation, if the measured temperature value TE of the cone of the coal powder bin is X Set the temperature to 55°C. Set The temperature is 50°C, and the temperature difference ΔT is set to 5°C. At this time, 55-50=5≤ΔT, and the pulverized coal in the pulverized coal bin 9 is returned to the pulverized coal. The pulverized coal is pneumatically conveyed to the coal feeder 2 and then enters the coal mill 7 for grinding and heating again to ensure its good fluidity.

[0040] Taking the powder return of spray tank A as an example, the specific operation steps are as follows:

[0041] The first step is to open the lower coal shut-off valve 10 of the lower A injection tank, and load the pulverized coal in the pulverized coal bin 9 into the A injection tank 12. After the A injection tank 12 is loaded with pulverized coal, close the lower coal shut-off valve 10 of the A injection tank;

[0042] The second step is to open the A spray tank pressurized branch pipe cut-off valve 13 and the pressurized main pipe flow regulating valve 14 to pressurize the A spray tank 12 after the powder is loaded. When the pressure reaches the initial set pressure PTA, Set =400kPa, close the A spray tank pressurized branch pipe cut-off valve 13 and the pressurized main pipe flow regulating valve 14;

[0043] The third step is to close the A injection main shut-off valve 20, open the A injection tank return powder branch shut-off valve 16, open the A injection tank return powder main shut-off valve 4, open the A injection tank air supply branch shut-off valve 15, and open the A injection tank outlet shut-off valve 18 in sequence, and return the pulverized coal in the A injection tank to the turbine housing of the running coal feeder 2 by pneumatic conveying.

[0044] If the actual measured pressure at the end of the powder return main pipe is PT CX =80kPa, the end pressure setting value of the powder return main pipe PT CSet =100kPa, the pressure difference ΔP is set to 50kPa, at this time |80-100|=20<ΔP, at this time open the A spray tank pressurized branch pipe cut-off valve 13, linearly adjust the opening K of the pressurized main pipe flow regulating valve 14 PN =K PNi +αU P , gradually open the flow regulating valve of the pressurized main pipe; if the measured pressure value at the end of the return powder main pipe is PT CX =50kPa, the end pressure setting value of the powder return main pipe PT CSet =100kPa, the pressure difference ΔP is set to 50kPa, at this time |50-100|=50=ΔP, then the pressure main flow regulating valve opening K is maintained PN If the measured value of the pressure at the end of the powder return main pipe is PT CX =20kPa, the pressure setting value of the powder return main pipe end is PT CSet =100kPa, the pressure difference ΔP is set to 50kPa, at this time |20-100|=80>ΔP, then the opening K of the flow control valve of the pressurized main pipe is linearly adjusted PN =K PNi -αU P , gradually reduce the opening of the flow regulating valve of the pressurized main pipe until the pressure at the end of the return powder main pipe reaches PT CX -PT CSet When ∣=ΔP, the opening degree K of the pressure main flow regulating valve is maintained PN constant.

[0045] Among them: TE Xis the measured temperature of the cone of the pulverized coal bin; TE Set PT is the set value of the cone temperature of the pulverized coal bin; A PT C They are the measured pressure values ​​at the end of the A spray tank and the powder return main pipe; PT CSet K is the set value of the pressure at the end of the powder return main pipe; PN K is the measured value of the flow control valve opening; PNi is the initial value of the flow control valve opening; α is the flow control valve opening adjustment coefficient, which can be set manually according to the actual working conditions and has a value range of 0 to 100 integers; U P It is the smallest regulating unit of the flow control valve.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A blast furnace coal injection system, comprising a raw coal bunker, a coal feeder, a coal mill, a coal powder collector, a coal powder bunker, a spray tank, and a coal powder distributor which are sequentially connected and arranged along the flow direction of the coal powder medium; the coal mill is also connected to a flue gas furnace, the coal powder collector is connected to a coal powder fan, the spray tank is connected to a pressurized main pipe, and the outlet of the spray tank is connected to an air replenisher, characterized in that: A powder return main pipe is also provided between the injection tank and the coal feeder, and a powder return main pipe cut-off valve is provided on the powder return main pipe; the powder return main pipe connects the outlet of the injection tank with the coal feeder, and is used to transport the stored coal powder in the coal powder bin to the coal feeder by pneumatic conveying, and then enters the coal mill for further grinding and heating to ensure good fluidity of the coal powder.

2. The blast furnace coal injection system according to claim 1, characterized in that: The spray tanks are arranged in parallel in one or more ways, and the outlet of each spray tank is connected to the powder return main pipe through a powder return branch pipe, and each powder return branch pipe is provided with a powder return branch pipe cut-off valve.

3. The blast furnace coal injection system according to claim 2, characterized in that: The injection tank outlet shut-off valve, the air supply device and the injection main pipe shut-off valve are arranged in sequence on the connecting pipeline between the injection tank and the coal powder distributor along the coal powder conveying direction; the powder return branch pipe is connected between the air supply device and the injection main pipe shut-off valve; the air supply device is connected to the air supply main pipe through the air supply branch pipe, and the air supply branch pipe is provided with an air supply branch pipe shut-off valve.

4. The blast furnace coal injection system according to claim 3, characterized in that: The pressurized main pipe is connected to the injection tank through a pressurized branch pipe; a thermometer is provided at the cone of the pulverized coal bin; a pressurized main pipe flow regulating valve is provided on the pressurized main pipe, and a pressurized branch pipe cut-off valve is provided on the pressurized branch pipe.

5. The blast furnace coal injection system according to claim 4, characterized in that: Pressure gauges are provided on the pulverized coal return main pipe and the injection tank; a coal cut-off valve under the injection tank is provided between the outlet of the pulverized coal bin and the inlet of the injection tank.

6. A method for returning coal powder in a blast furnace coal injection system, characterized in that: When the blast furnace is in the non-coal injection state, when the temperature of the pulverized coal bin cone meets TE X -TE Set When ≤ΔT, the outlet of the injection tank is connected to the coal feeder, and the stored pulverized coal in the pulverized coal bin is transported to the coal feeder by pneumatic conveying, and then enters the coal mill for re-grinding and heating, and the pulverizing operation is performed to ensure good fluidity of the pulverized coal; Among them, TE X is the measured temperature of the cone of the pulverized coal bin; TE Set is the temperature setting value of the cone of the pulverized coal bin, and ΔT is the manually set value.

7. The method for returning coal powder in a blast furnace coal injection system according to claim 6, characterized in that: Using the blast furnace coal injection system as claimed in any one of claims 1 to 5, the coal powder return operation steps are as follows: The first step is to open the coal shut-off valve at the bottom of the injection tank, load the pulverized coal in the pulverized coal bin into the injection tank, and then close the coal shut-off valve at the bottom of the injection tank after the pulverized coal in the injection tank is loaded; The second step is to open the pressure branch pipe cut-off valve and the pressure main pipe flow regulating valve to pressurize the spray tank after the powder is loaded. Wait until the pressure reaches the initial set pressure PT. Set When the pressure branch pipe cut-off valve and the pressure main pipe flow regulating valve of the spray tank are closed; The third step is to sequentially close the shut-off valve of the injection main corresponding to the injection tank, open the shut-off valve of the return powder branch pipe, open the shut-off valve of the return powder main pipe, open the shut-off valve of the air supply branch pipe, and open the shut-off valve of the injection tank outlet, and return the pulverized coal in the injection tank to the turbine housing of the running coal feeder by pneumatic conveying.

8. The method for returning coal powder in a blast furnace coal injection system according to claim 7, characterized in that: In the third step, when the pressure at the end of the powder return main pipe meets |PT CX -PT CSet When ∣<ΔP, open the cut-off valve of the pressurized branch pipe and linearly adjust the opening degree K of the flow regulating valve of the pressurized main pipe PN =K PNi +αU P , gradually open the flow regulating valve of the pressurized main pipe; when the pressure at the end of the return powder main pipe ∣PT CX -PT CSet When ∣=ΔP, the opening degree K of the pressure main flow regulating valve is maintained PN unchanged; when the pressure at the end of the powder return main pipe ∣PT CX -PT CSet When ∣>ΔP, the opening degree K of the pressure main flow control valve is linearly adjusted. PN =K PNi -αU P , gradually reduce the opening of the pressure main pipe flow control valve until the end pressure of the return powder main pipe reaches PT CX -PT CSet When ∣=ΔP, the opening degree K of the pressure main flow regulating valve is maintained PN constant; Among them, ΔP is the manually set value; PT, PT C They are the measured pressure values ​​at the end of the spray tank and the powder return main pipe; PT CSet K is the set value of the pressure at the end of the powder return main pipe; PN K is the measured value of the opening of the flow control valve of the pressurized main pipe; PNi is the initial value of the opening of the pressure main flow control valve; α is the valve opening adjustment coefficient of the pressure main flow control valve, which is manually set according to the actual working conditions and has a value range of 0 to 100 integers; U P It is the smallest regulating unit of the pressurized main flow control valve.

9. The method for returning coal powder in a blast furnace coal injection system according to claim 8, characterized in that: Pressure setting value PT of the spray tank Set , manually input and set on the control system, the value range is 100kPa ~ 500kPa; the pressure setting value PT at the end of the return powder main pipe CSet , is manually input and set on the control system, and the value range is 0kPa~100kPa; the difference ΔP between the actual measured value of the pressure at the end of the return powder main pipe and the set pressure is manually input and set on the control system, and the value range is 0kPa~50kPa.

10. The method for returning coal powder in a blast furnace coal injection system according to claim 6, characterized in that: Temperature setting value TE of the cone of the pulverized coal bin Set , which is manually input and set on the control system, and the value range is 45℃~90℃; the difference ΔT between the actual temperature of the cone of the pulverized coal bin and the set temperature is manually input and set on the control system, and the value range is 0℃~20℃.

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