CN115305125A - Full negative pressure coal powder preparation system and method capable of self-circulating flue gas - Google Patents

Abstract

The invention belongs to the field of metallurgy and coal carbon, and relates to a system and a method for preparing full negative pressure coal powder capable of self-circulating flue gas, which comprises a raw coal bin communicated with a raw coal conveying belt, a coal feeder and a coal mill sequentially communicated with the raw coal bin, and a drying furnace and a cloth bag powder collecting device respectively communicated with the coal mill, wherein a blast furnace hot blast furnace waste gas pipeline is arranged on the drying furnace, and a waste gas stop valve, a waste gas fan inlet regulating valve, a waste gas induced draft fan and a waste gas fan outlet regulating valve are sequentially arranged on the blast furnace hot blast furnace waste gas pipeline; the cloth bag powder collecting device is communicated with a pulverized coal fan through a system air volume regulating valve, the other end of the pulverized coal fan is communicated with a blast furnace hot blast stove waste gas pipeline through a circulating waste gas stop valve, and a communication port is formed between a waste gas draught fan and a waste gas fan outlet regulating valve. The invention recycles the heat in the tail gas discharged by the coal powder preparation system and reduces the tail gas quantity discharged into the atmosphere by the coal powder preparation system.

Description

A full negative pressure pulverized coal preparation system and method capable of self-circulating flue gas

technical field

The invention belongs to the fields of metallurgy and coal, and relates to a full negative pressure pulverized coal preparation system and method capable of self-circulating flue gas.

Background technique

The existing safety devices for nitrogen filling in the pulverizing system are not well set up. Because most of the raw coal in the pulverized coal preparation system is mixed with a relatively high proportion of bituminous coal, the bituminous coal has a high volatile content and is easy to burn and explode, which brings great harm to the safety of pulverizing. a certain degree of difficulty. Most of the pulverized coal preparation systems rely on the exhaust gas of the blast furnace hot blast stove. Once the blast furnace shutdown that provides the exhaust gas cannot provide exhaust gas or the amount of exhaust gas is greatly reduced, the system has to be shut down and unable to make powder. The exhaust gas checked by the pulverized coal preparation system has not been recycled, resulting in heat loss in the system and air pollution.

Contents of the invention

In view of this, the object of the present invention is to provide a full negative pressure pulverized coal preparation system and method capable of self-circulating flue gas, which can recycle the heat in the tail gas discharged from the pulverized coal preparation system, and reduce the amount of waste generated by the pulverized coal preparation system Exhaust gas into the atmosphere.

In order to achieve the above object, the present invention provides the following technical proposal: a full negative pressure pulverized coal preparation system capable of self-circulating flue gas, including a raw coal bunker connected with the raw coal transport belt, a coal feeder and a coal grinding machine connected with the raw coal bunker in sequence machine, and the drying furnace and bag powder collection device respectively connected with the coal mill. The drying furnace is equipped with a blast furnace hot blast stove exhaust gas pipeline, and the blast furnace hot blast stove exhaust gas pipeline is sequentially equipped with a waste gas shut-off valve and a waste gas fan inlet regulating valve. , the exhaust gas induced draft fan and the outlet regulating valve of the exhaust gas fan; the bag powder collection device is connected with a pulverized coal fan through the system air volume regulating valve, and the other end of the pulverized coal fan is connected with the exhaust gas pipeline of the blast furnace hot blast stove through the circulating waste gas shut-off valve, and the connection port It is arranged between the exhaust gas induced draft fan and the outlet regulating valve of the exhaust gas fan.

Optionally, an ignition device is connected to the top of the drying furnace, and coke oven gas pipelines, blast furnace gas inner ring pipelines and blast furnace gas outer ring pipelines are sequentially arranged on the top of the drying furnace along the ignition device to the bottom.

Optionally, a coke oven gas cut-off valve, a coke oven gas regulating valve and a coking coal air-conditioning regulating valve are arranged in sequence along the coke oven gas inlet on the coke oven gas pipeline; Inner ring cut-off valve, blast furnace gas inner ring regulating valve and high coal inner ring air-assisted regulating valve; blast furnace gas outer ring pipeline along the blast furnace gas inlet is provided with blast furnace gas outer ring stop valve, blast furnace gas outer ring regulating valve and high coal Outer ring air-assisted regulating valve; coking coal air-assisted regulating valve, high-coal inner-ring air-assisted regulating valve and high-coal outer ring air-assisted regulating valve are set in parallel and are connected with combustion-supporting fans.

Optionally, the drying furnace and the coal mill are connected to the coal mill through the hot air valve, cold air inlet, nitrogen inlet, oxygen content monitoring point, and temperature monitoring point in turn. The drying furnace is also equipped with a pressure gauge, a peephole and a vent Valve; the cold air inlet is provided with a cold air inlet pipe, which is provided with a cold air regulating valve and a cold air stop valve in sequence along the cold air inlet direction, and a nitrogen inlet pipe is arranged on the nitrogen inlet, and the pipe is provided with a grinding coal Machine inlet nitrogen filling valve.

Optionally, a coal feeder inlet valve is set between the raw coal bunker and the coal feeder, a coal mill inlet valve is set between the coal feeder and the coal mill, and a sealed fan is connected to the coal feeder and the coal mill; The coal mill is connected to the bag powder collection device through the nitrogen inlet, temperature monitoring point, and oxygen content monitoring point in sequence. The nitrogen inlet is equipped with a nitrogen pipeline with a nitrogen pump at the outlet of the coal mill, and an ammeter is also installed on the coal mill.

Optionally, the top of the bag powder collection device is equipped with a pulse powder device for feeding nitrogen gas, and the bottom is connected to the coal powder bin through the unloading motor and the coal powder vibrating screen in turn; between the bag powder collection device and the system air volume regulating valve There are also aerobic content monitoring points and temperature monitoring points respectively, and a nitrogen filling valve for filling nitrogen is also set on the bag powder collecting device.

A full negative pressure pulverized coal preparation method capable of self-circulating flue gas, using the above-mentioned full negative pressure pulverized coal preparation system capable of self-circulating flue gas, comprising the following steps:

A. Preparations before milling,

A1, start the raw coal transport belt, fill the raw coal bunker with raw coal, and ensure that raw coal enters the coal mill;

A2, the drying furnace is ignited and kept warm to provide heat for the entire system to dry raw coal;

A21, Furnace purging: Turn on the combustion-supporting fan and the coking coal-assisted air-conditioning valve, and use combustion-supporting air to purge the drying furnace furnace. The time for purging the furnace is not less than 3 minutes, and the ignition is officially carried out after purging;

A22, ignition procedure: open the coke oven gas regulating valve, open the coking coal air-conditioning regulating valve, and start the ignition device; at this time, the ignition device is pushed into the drying furnace, and the coke oven gas stop valve is opened to supply coke oven gas to start ignition;

A23, confirm that the ignition is successful: observe the flame situation through the peephole on the drying furnace or the on-site remote furnace monitoring camera, and the light blue flame indicates that the ignition is successful;

A24, Furnace body heat preservation: Open the blast furnace gas inner ring stop valve, blast furnace gas inner ring regulating valve, high coal inner ring auxiliary air conditioning valve to burn blast furnace gas to keep the drying furnace warm;

B. The pulverized coal preparation system starts,

B1, open the hot air valve, close the release valve;

B2, turn on the pulverized coal fan, the whole process of the pulverized coal preparation system is in full negative pressure operation, and the pulverized coal fan provides negative pressure for the whole system;

B3, open the system air volume control valve;

B4, turn on the exhaust gas induced draft fan, open the exhaust gas shut-off valve and the exhaust gas fan inlet regulating valve, and the exhaust gas fan outlet regulating valve, and introduce the blast furnace hot blast stove exhaust gas into the drying furnace to mix with the high-temperature gas in the drying furnace;

B5, open the cold air cut-off valve and adjust the temperature of the entire system by adjusting the opening of the cold air regulating valve and the combustion volume of blast furnace gas, keep the outlet temperature of the coal mill within 95°C, and gradually increase the outlet temperature of the bag powder collecting device;

B6, by adjusting the opening of the air volume regulating valve of the system, the negative pressure of the whole system can be well controlled, and the pressure of the furnace chamber of the drying furnace can be kept at a slight negative pressure, so as to ensure that the system has a certain suction force and the entire gas path is unobstructed;

B7, when the outlet temperature of the bag powder collection device reaches about 70°C, start the coal mill, unloading motor, coal powder vibrating screen and pulse powder blowing device;

B8. Open the inlet valve of the coal mill and the inlet valve of the coal feeder, start the coal feeder and set the coal feeding amount. The initial setting value of the coal feeding amount should not be too large. By observing the coal mill ammeter, when the current When the increase is obvious, it is judged that the coal mill has bitten coal. At this time, the cold air stop valve and the cold air regulating valve are closed, and the formal coal pulverization begins;

B9. Gradually and slowly increase the coal feed rate of the coal feeder, and gradually increase the blast furnace gas combustion rate, and keep the outlet temperature of the coal mill at 85°C-93°C;

B10, when the temperature at the inlet and outlet of the coal mill and the oxygen content are determined to be stable and within the specified range, the system is started; at this time, the waste gas circulation valve can be opened to reintroduce the waste gas from the pulverized coal fan to the drying furnace for preheating and recycling.

Optionally, in step B3, the initial opening should not be too large, which is 30%-40%, because coal has not been formally pulverized at the initial stage of operation, and the initial opening should not be too large, which is 30%-40%. The opening of the blast furnace gas inner ring regulating valve controls the gas combustion volume.

Optionally, in step B9, when the inner ring blast furnace gas is insufficient, the outer ring blast furnace gas is turned on.

Optionally, during system start-up, if the temperature at the inlet and outlet of the coal mill and the oxygen content, and the outlet temperature and oxygen content of the cloth bag powder collection device exceed the standard, immediately open the nitrogen filling valve set at the corresponding place to open and flush nitrogen to cool down or reduce the oxygen content to ensure system security.

The beneficial effect of the present invention is that: the present invention is fully enclosed and fully negative pressure operation, the air is effectively isolated in the pulverizing process, and nitrogen-filled safety devices are installed in multiple places in the system, so that the raw coal can be safely, quickly and efficiently processed into quality (moisture, particle size etc.) Qualified pulverized coal. Reduce the dependence of the pulverized coal preparation system on the exhaust gas of the blast furnace hot blast stove, and avoid the dilemma that the hot blast stove cannot provide exhaust gas or the amount of exhaust gas is greatly reduced when the blast furnace is shut down. At the same time, the heat in the tail gas discharged from the pulverized coal preparation system is recycled to reduce heat loss, reduce the consumption of blast furnace gas, and save energy. And effectively reduce the amount of tail gas discharged into the atmosphere by the pulverized coal preparation system, and reduce the pollution to the environment.

Other advantages, objects and features of the present invention will be set forth in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the investigation and research below, or can be obtained from It is taught in the practice of the present invention. The objects and other advantages of the invention may be realized and attained by the following specification.

Description of drawings

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

Figure 1 is a schematic diagram of the overall system of the present invention.

Reference signs: raw coal transport belt 1, raw coal bunker 2, coal feeder inlet valve 3, coal feeder 4, coal mill inlet valve 5, sealing fan 6, coal mill 7, ammeter 8, coal mill outlet nitrogen filling Valve 9, cloth bag powder collection device 10, pulse powder blowing device 11, nitrogen filling valve 12, unloading motor 13, coal powder vibrating screen 14, coal powder bin 15, system air volume regulating valve 16, coal powder fan 17, cycle exhaust gas cut-off Valve 18, waste gas shut-off valve 19, waste gas fan inlet regulating valve 20, waste gas induced draft fan 21, waste gas blower outlet regulating valve 22, drying oven 23, pressure gauge 24, peephole 25, combustion-supporting fan 26, ignition device 27, high coal outside Ring auxiliary air conditioning valve 28, high coal inner ring air conditioning adjusting valve 29, coking coal air conditioning adjusting valve 30, coke oven gas stop valve 31, coke oven gas regulating valve 32, blast furnace gas inner ring stop valve 33, blast furnace gas inner ring Regulating valve 34, blast furnace gas outer ring shut-off valve 35, blast furnace gas outer ring regulating valve 36, relief valve 37, hot air valve 38, coal mill inlet nitrogen filling valve 39, cold air shut-off valve 40, cold air regulating valve 41, temperature monitoring point 42. Oxygen content monitoring point 43.

Detailed ways

Embodiments of the present invention are described below through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes, and various modifications or changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following embodiments are only schematically illustrating the basic concept of the present invention, and the following embodiments and the features in the embodiments can be combined with each other in the case of no conflict.

Wherein, the accompanying drawings are for illustrative purposes only, and represent only schematic diagrams, rather than physical drawings, and should not be construed as limiting the present invention; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, Enlargement or reduction does not represent the size of the actual product; for those skilled in the art, it is understandable that certain known structures and their descriptions in the drawings may be omitted.

In the drawings of the embodiments of the present invention, the same or similar symbols correspond to the same or similar components; , "front", "rear" and other indicated orientations or positional relationships are based on the orientations or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred devices or elements must It has a specific orientation, is constructed and operated in a specific orientation, so the terms describing the positional relationship in the drawings are for illustrative purposes only, and should not be construed as limiting the present invention. For those of ordinary skill in the art, the understanding of the specific meaning of the above terms.

Please refer to Figure 1, which is a self-circulating flue gas full negative pressure pulverized coal preparation system, including a raw coal bunker 2 connected to the raw coal transportation belt 1, a coal feeder 4 and a coal mill 7 connected to the raw coal bunker 2 in sequence , and the drying furnace 23 and the bag powder collecting device 10 which are respectively communicated with the coal mill 7, the drying furnace 23 is provided with a blast furnace hot blast stove exhaust gas pipeline, and the blast furnace hot blast stove exhaust gas pipeline is successively provided with a waste gas shut-off valve 19, a waste gas Fan inlet regulating valve 20, waste gas induced draft fan 21 and waste gas fan outlet regulating valve 22; the cloth bag powder collection device 10 is connected with a pulverized coal fan 17 through a system air volume regulating valve 16, and the other end of the pulverized coal fan 17 is passed through a circulating waste gas stop valve 18 is connected with the exhaust gas pipeline of the blast furnace hot blast stove, and the connection port is set between the exhaust gas induced draft fan 21 and the exhaust gas fan outlet regulating valve 22. The top of the drying furnace 23 is connected with an ignition device 27, and the top of the drying furnace 23 is arranged in sequence along the ignition device 27 to the bottom There are coke oven gas pipelines, blast furnace gas inner loop pipelines and blast furnace gas outer loop pipelines. Coke oven gas shut-off valves 31, coke oven gas regulating valves 32 and coking coal auxiliary valves are arranged in sequence along the coke oven gas inlets on the coke oven gas pipelines. Air-conditioning control valve 30; the blast furnace gas inner ring pipeline is provided with a blast furnace gas inner ring shut-off valve 33, a blast furnace gas inner ring control valve 34 and a high coal inner ring air conditioning control valve 29 along the blast furnace gas inlet; the blast furnace gas outer ring pipeline Along the blast furnace gas inlet, there are blast furnace gas outer ring cut-off valve 35, blast furnace gas outer ring regulating valve 36 and high-coal outer ring air-assisted regulating valve 28; coking coal air-assisted regulating valve 30, high-coal inner ring air-assisted regulating valve 29 and The high-coal outer ring air-conditioning control valve 28 is set in parallel and is connected with a combustion-supporting fan 26. The drying furnace 23 and the coal mill 7 pass through the hot air valve 38, the cold air inlet, the nitrogen inlet, the oxygen content monitoring point 43, and the temperature monitoring point in sequence. 42 communicates with the coal mill 7, and the drying furnace 23 is also provided with a pressure gauge 24, a peep hole 25 and a release valve 37; The regulating valve 41 and the cold air cut-off valve 40, the nitrogen inlet is provided with a nitrogen inlet pipe, the pipe is provided with a coal mill inlet nitrogen filling valve 39, and a coal feeder inlet is arranged between the raw coal bunker 2 and the coal feeder 4 A coal mill inlet valve 5 is set between the valve 3, the coal feeder 4 and the coal mill 7, and the coal feeder 4 and the coal mill 7 are jointly connected with a sealed fan 6; the coal mill 7 passes through the nitrogen inlet in turn , the temperature monitoring point 42, the oxygen content monitoring point 43 are connected with the bag powder collection device 10, the nitrogen gas inlet is provided with a nitrogen pipeline with a coal mill outlet nitrogen charging pump 9, and an ammeter 8 is also arranged on the coal mill 7, and the cloth bag The top of the powder collection device 10 is equipped with a pulse powder punching device 11 for feeding nitrogen gas, and the bottom is connected with the coal powder vibrating screen 14 through the unloading motor 13 to have a coal powder bin 15; the bag powder collection device 10 is connected with the system air volume regulating valve 16 An oxygen content monitoring point 43 and a temperature monitoring point 42 are respectively arranged between them, and a nitrogen charging valve 12 for charging nitrogen gas is also arranged on the bag powder collecting device 10 .

A full negative pressure pulverized coal preparation method capable of self-circulating flue gas, using the above-mentioned full negative pressure pulverized coal preparation system capable of self-circulating flue gas, comprising the following steps:

1. Start-up steps and related process flow of pulverized coal preparation system;

(1) The raw coal transport belt 1 is started, and the raw coal bunker 2 is filled with raw coal (to ensure that there is a continuous flow of raw coal to enter in the coal mill 7).

(2) Ignition and heat preservation process of drying furnace 23 (providing the heat of drying raw coal for the whole system):

① Furnace purging: Turn on the combustion-supporting fan 26 and the coking coal-assisted air-conditioning valve 30, and use the combustion-supporting air to purge the furnace 23 of the drying furnace. .) After the purging is completed, the ignition is officially carried out.

②Ignition procedure: open the coke oven gas control valve 32, open the coking coal air conditioning control valve 30, and start the ignition device 27. At this time, the ignition device 27 is pushed into the drying oven 23, and the coke oven gas shut-off valve 31 is opened to feed the coke oven gas to start ignition.

③Confirm that the ignition is successful: observe the flame situation through the peep hole 25 on the drying furnace 23 or the installed on-site remote monitoring camera in the furnace, and the appearance of a light blue flame indicates that the ignition is successful.

④ Heat preservation of the furnace body: open the blast furnace gas inner ring shut-off valve 33, the blast furnace gas inner ring regulating valve 34, the high coal inner ring air conditioning regulating valve 29 to burn the blast furnace gas to carry out the drying furnace 23 heat preservation.

2. Start-up steps and related process flow of pulverized coal preparation system;

(1) Open the hot air valve 38 and close the release valve 37.

(2) Turn on the pulverized coal fan 17 (the whole process of the pulverized coal preparation system is full negative pressure operation, and the pulverized coal fan 17 provides negative pressure for the whole system).

(3) Open the system air volume regulating valve 16 (due to the lack of formal coal grinding in the initial stage of start-up, the entire pulverizing system has no load, and the initial opening should not be too large, 30%-40% is appropriate.)

(4) Turn on the waste gas induced draft fan 21, open the waste gas shut-off valve 19 and the waste gas blower inlet regulating valve 20, the waste gas blower outlet regulating valve 22, and the blast furnace hot blast stove waste gas is introduced into the drying furnace 23 furnace and the high-temperature gas in the drying furnace 23 furnace to mix.

(5) Open the cold wind shut-off valve 40 and by adjusting the opening degree of the cold air control valve 41, the blast furnace gas combustion rate (by controlling the blast furnace gas outer ring control valve 36 and the blast furnace gas inner ring control valve 34 openings, the gas combustion rate is controlled), Adjust the temperature of the entire system, keep the outlet temperature of the coal mill 7 within 95°C, and gradually increase the outlet temperature of the bag powder collecting device 10.

(6) Control the negative pressure of the whole system (by observing the pressure gauge 24 on the drying furnace 23) by adjusting the opening degree of the system air volume regulating valve 16, and keep the furnace pressure of the drying furnace 23 at a slight negative pressure (about -200pa), so as to ensure The system has a certain pumping force, and the entire gas path is unobstructed.

(7) When the outlet temperature of the cloth bag powder collection device 10 reaches about 70°C, start the coal mill 7, the unloading motor 13, the coal powder vibrating screen 14 and the pulse powder blowing device 11.

(8) Open the inlet valve 5 of the coal mill and the inlet valve 3 of the coal feeder, start the coal feeder 4 and set the coal feeding amount. The initial setting value of the coal feeding amount should not be too large (about 10t/h). Observe the ammeter 8 of the coal mill 7. When the current increases significantly compared with that before the coal supply, it is judged that the coal mill 7 has bitten coal. At this time, close the cold air stop valve 40 and the cold air regulating valve 41 (to prevent air from entering the system and the coal mill 7 Contact with the raw coal within), and formally grind coal into pulverized coal.

(9) Gradually and slowly increase the coal feed rate of the coal feeder 4, and gradually increase the blast furnace gas combustion rate (when the inner ring blast furnace gas is insufficient, the outer ring blast furnace gas is turned on), and keep the outlet temperature of the coal mill 7 at 85°C-93°C .

(10) When it is determined that the temperature at the inlet and outlet of the coal mill 7 and the oxygen content are stable and within the specified range, the system starts up. At this time, the circulating waste gas cut-off valve 1918 can be opened to reintroduce the waste gas extracted by the pulverized coal fan 17 to the drying furnace 23 for preheating and recycling.

(11) During system start-up, if the temperature and oxygen content at the inlet and outlet of the coal mill 7 and the outlet temperature and oxygen content of the cloth bag powder collection device 10 exceed the standard, immediately open the nitrogen filling valve set at the corresponding place to open and flush nitrogen to cool down or lower the oxygen content Ensure system security.

The invention is fully enclosed and fully negative pressure operation, the air is effectively isolated during the pulverization process, and nitrogen-filled safety devices are installed in multiple places in the system, so that the raw coal can be safely, quickly and efficiently processed into coal powder with qualified quality (moisture, particle size, etc.). Reduce the dependence of the pulverized coal preparation system on the exhaust gas of the blast furnace hot blast stove, and avoid the dilemma that the hot blast stove cannot provide exhaust gas or the amount of exhaust gas is greatly reduced when the blast furnace is shut down. At the same time, the heat in the tail gas discharged from the pulverized coal preparation system is recycled to reduce heat loss, reduce the consumption of blast furnace gas, and save energy. And effectively reduce the amount of tail gas discharged into the atmosphere by the pulverized coal preparation system, and reduce the pollution to the environment.

Finally, it is noted that the above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out Modifications or equivalent replacements, without departing from the spirit and scope of the technical solution, should be included in the scope of the claims of the present invention.

Claims (10)

1. A full negative pressure pulverized coal preparation system capable of self-circulating flue gas, characterized in that: it includes a raw coal bunker connected with the raw coal transport belt, a coal feeder and a coal mill connected with the raw coal bunker in sequence, and respectively connected to the raw coal bunker The drying furnace connected to the coal mill is connected to the bag powder collection device. The blast furnace hot blast stove exhaust gas pipeline is installed on the drying furnace. Fan outlet regulating valve; The cloth bag powder collection device is connected with a pulverized coal fan through the system air volume regulating valve, and the other end of the pulverized coal fan is connected with the exhaust gas pipeline of the blast furnace hot blast stove through the circulating waste gas stop valve, and the connection port is set at the exhaust gas induced draft fan and the exhaust gas fan outlet regulating valve between. 2. A self-circulating flue gas full negative pressure pulverized coal preparation system according to claim 1, characterized in that: the top of the drying furnace is connected with an ignition device, and the top of the drying furnace is sequentially provided with coke ovens along the ignition device to the bottom Gas pipeline, blast furnace gas inner ring pipeline and blast furnace gas outer ring pipeline. 3. A self-circulating flue gas full negative pressure pulverized coal preparation system according to claim 2, characterized in that: on the coke oven gas pipeline along the coke oven gas inlet, coke oven gas shut-off valves, coke oven gas Gas regulating valve and coking coal air-aiding regulating valve; blast furnace gas inner ring pipeline along the blast furnace gas inlet is provided with blast furnace gas inner ring stop valve, blast furnace gas inner ring regulating valve and high coal inner ring air-aiding regulating valve; blast furnace gas outer ring Along the blast furnace gas inlet, the pipeline is provided with a blast furnace gas outer ring stop valve, a blast furnace gas outer ring regulating valve and a high coal outer ring air-conditioning regulating valve; The coking coal air-assisted regulating valve, the high-coal inner ring air-assisted regulating valve and the high-coal outer ring air-assisted regulating valve are arranged in parallel and are connected with a combustion-supporting fan. 4. A self-circulating flue gas full negative pressure pulverized coal preparation system according to claim 1, characterized in that: the drying furnace and the coal mill pass through the hot air valve, the cold air inlet, the nitrogen inlet, and the oxygen content in sequence. The monitoring point and temperature monitoring point are connected to the coal mill, and the drying furnace is also equipped with a pressure gauge, a peephole and a relief valve; The cold air inlet is provided with a cold air inlet pipe, which is provided with a cold air regulating valve and a cold air stop valve in sequence along the cold air inlet direction, and a nitrogen inlet pipe is arranged on the nitrogen inlet, and the coal mill inlet is arranged on the pipe Nitrogen filling valve. 5. A self-circulating flue gas full negative pressure pulverized coal preparation system according to claim 1, characterized in that: a coal feeder inlet valve is arranged between the raw coal bunker and the coal feeder, and the coal feeder and the mill There is a coal mill inlet valve between the coal machines, and a sealed fan is connected to the coal feeder and the coal mill; The coal mill is connected to the bag powder collection device through the nitrogen inlet, temperature monitoring point, and oxygen content monitoring point in sequence. The nitrogen inlet is equipped with a nitrogen pipeline with a nitrogen pump at the outlet of the coal mill, and an ammeter is also installed on the coal mill. 6. A self-circulating flue gas full negative pressure pulverized coal preparation system according to claim 1, characterized in that: the top of the bag powder collecting device is equipped with a pulse powdering device for feeding nitrogen gas, and the bottom is successively unloaded The feed motor is connected with the pulverized coal vibrating screen to have a pulverized coal bin; There are oxygen content monitoring points and temperature monitoring points respectively set between the bag powder collecting device and the system air volume regulating valve, and the bag powder collecting device is also equipped with a nitrogen filling valve for charging nitrogen. 7. A method for preparing fully negative pressure pulverized coal capable of self-circulating flue gas, using a fully negative pressure pulverized coal preparation system capable of self-circulating flue gas as described in any one of claims 1 to 6, characterized in that, Include the following steps: A. Preparations before milling, A1, start the raw coal transport belt, fill the raw coal bunker with raw coal, and ensure that raw coal enters the coal mill; A2, the drying furnace is ignited and kept warm to provide heat for the entire system to dry raw coal; A21, Furnace purging: Turn on the combustion-supporting fan and the coking coal-assisted air-conditioning valve, and use combustion-supporting air to purge the drying furnace furnace. The time for purging the furnace is not less than 3 minutes, and the ignition is officially carried out after purging; A22, ignition procedure: open the coke oven gas regulating valve, open the coking coal air-conditioning regulating valve, and start the ignition device; at this time, the ignition device is pushed into the drying furnace, and the coke oven gas stop valve is opened to supply coke oven gas to start ignition; A23, confirm that the ignition is successful: observe the flame situation through the peephole on the drying furnace or the on-site remote furnace monitoring camera, and the light blue flame indicates that the ignition is successful; A24, Furnace body heat preservation: Open the blast furnace gas inner ring stop valve, blast furnace gas inner ring regulating valve, high coal inner ring auxiliary air conditioning valve to burn blast furnace gas to keep the drying furnace warm; B. The pulverized coal preparation system starts, B1, open the hot air valve, close the release valve; B2, turn on the pulverized coal fan, the whole process of the pulverized coal preparation system is in full negative pressure operation, and the pulverized coal fan provides negative pressure for the whole system; B3, open the system air volume control valve; B4, turn on the exhaust gas induced draft fan, open the exhaust gas shut-off valve and the exhaust gas fan inlet regulating valve, and the exhaust gas fan outlet regulating valve, and introduce the blast furnace hot blast stove exhaust gas into the drying furnace to mix with the high-temperature gas in the drying furnace; B5, open the cold air cut-off valve and adjust the temperature of the entire system by adjusting the opening of the cold air regulating valve and the combustion volume of blast furnace gas, keep the outlet temperature of the coal mill within 95°C, and gradually increase the outlet temperature of the bag powder collecting device; B6, by adjusting the opening of the air volume regulating valve of the system, the negative pressure of the whole system can be well controlled, and the pressure of the furnace chamber of the drying furnace can be kept at a slight negative pressure, so as to ensure that the system has a certain suction force and the entire gas path is unobstructed; B7, when the outlet temperature of the bag powder collection device reaches about 70°C, start the coal mill, unloading motor, coal powder vibrating screen and pulse powder blowing device; B8. Open the inlet valve of the coal mill and the inlet valve of the coal feeder, start the coal feeder and set the coal feeding amount. The initial setting value of the coal feeding amount should not be too large. By observing the coal mill ammeter, when the current When the increase is obvious, it is judged that the coal mill has bitten coal. At this time, close the cold air stop valve and cold air regulating valve, and start formal coal grinding; B9. Gradually and slowly increase the coal feed rate of the coal feeder, and gradually increase the blast furnace gas combustion rate, and keep the outlet temperature of the coal mill at 85°C-93°C; B10, when the temperature at the inlet and outlet of the coal mill and the oxygen content are determined to be stable and within the specified range, the system is started; at this time, the waste gas circulation valve can be opened to reintroduce the waste gas from the pulverized coal fan to the drying furnace for preheating and recycling. 8. A kind of full negative pressure pulverized coal preparation method capable of self-circulating flue gas according to claim 7, characterized in that: in the B3 step, because the coal is not formally pulverized at the beginning of the operation, the whole pulverizing system has no load, and the initial start The degree should not be too large, which is 30%-40%. In step B5, the gas combustion volume is controlled by controlling the opening of the blast furnace gas outer ring regulating valve and the blast furnace gas inner ring regulating valve. 9. A kind of self-circulating flue gas full negative pressure pulverized coal preparation method according to claim 7 is characterized in that: in the B9 step, when the inner ring blast furnace gas is not enough, the outer ring blast furnace gas is turned on. 10. A self-circulating flue gas full negative pressure pulverized coal preparation method according to claim 7, characterized in that: during the system start-up process, such as the temperature of the inlet and outlet of the coal mill and the oxygen content, the outlet of the bag powder collecting device If the temperature and oxygen content exceed the standard, immediately open the nitrogen filling valve set at the corresponding place to open and rush in nitrogen to cool down or reduce the oxygen content to ensure the safety of the system.

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