A method and device for classified dust removal of a converter dry dust removal system

Abstract

The present invention belongs to the technical field of gas dust removal, and relates to a method and device for classified dust removal of a converter dry dust removal system. The classified dust removal device includes a converter, an evaporation cooler, a second-stage coarse dust collector, and a dry fine dust removal device connected in series through a flue gas pipeline in sequence; during the oxygen blowing of the converter, water mist is sprayed for cooling, and the outlet temperature of the evaporation cooler is controlled at 250°C to 300°C, and the first-stage cooling and coarse dust removal of the flue gas is completed in the evaporation cooler; after the flue gas is naturally cooled through the pipeline, it enters the second-stage coarse dust collector, and spray dust suppression is carried out. According to the principle of heat balance, an appropriate amount of water is sprayed to control the outlet temperature of the second-stage coarse dust collector above 150°C, and then it enters the subsequent fine dust removal device. Compared with the traditional method of spraying water in the evaporation cooler where the flue gas temperature drops to the required level in one step, on the basis of maintaining the total amount of sprayed water for cooling unchanged, the present invention can effectively improve the classified dust removal efficiency of the coarse dust removal, reduce the load of the subsequent fine dust removal, thereby extending the service life of the fine dust removal device and reducing the maintenance workload.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas dust removal, and relates to a classification dust removal method and device for a converter dry dust removal system. Background Art

[0002] In the existing converter dry dust removal system, the high-temperature dust-containing flue gas from the converter, after passing through the vaporization cooling flue, enters the evaporation cooler for spraying water to cool down and remove dust, and then enters the dry fine dust collector for purification. The evaporation cooler is arranged in the steelmaking workshop. Limited by the space, the equipment volume should not be too large. The flue gas velocity is as high as 20 m / s, and the rough dust removal efficiency in the evaporation cooler is only about 30%. During the oxygen blowing period, the moisture content of the outlet flue gas is generally 200 - 500 g / Nm 3 , and the dust content of the flue gas is generally 70 - 120 g / Nm 3 , and in extreme cases, it can reach 150 g / Nm 3 , resulting in a very heavy filtration load on the subsequent fine dust collector, a high failure rate, and high operation and maintenance costs. Therefore, how to improve the classification dust removal efficiency of the rough and fine dust collectors at a low cost, the core lies in improving the classification dust removal effect of the rough dust removal. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a classification dust removal method and device for a converter dry dust removal system. Compared with spraying water in the evaporation cooler where the flue gas temperature drops to the required level in one step, on the basis of maintaining the total amount of spray cooling water unchanged, it can effectively improve the classification dust removal efficiency of the rough dust removal, reduce the subsequent fine dust removal load, thereby prolong the service life of the fine dust removal device and reduce the maintenance workload.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] A classification dust removal device for a converter dry dust removal system, comprising a converter, an evaporation cooler, a second-stage rough dust collector, and a dry fine dust removal device connected in series through a flue gas pipeline in sequence;

[0006] The second-stage rough dust collector includes a tower body and a liquid spraying device; a conical ash storage tank is arranged at the bottom of the tower body; an air inlet channel and an air outlet channel are arranged on the side wall of the tower body; the air inlet channel is in an L shape and includes an air inlet horizontal section and an air inlet vertical section; the air inlet horizontal section extends from outside the tower body into the tower body and is connected to the air inlet vertical section. The air inlet vertical section is arranged inside the tower body. An expanding tube in a conical shape is arranged at the upper part of the air inlet vertical section. A dust discharge hopper is arranged at the bottom of the connection between the air inlet vertical section and the air inlet horizontal section, and the dust discharge hopper extends into the ash storage tank; the liquid spraying device extends from outside the tower body into the air inlet vertical section to spray and dust the flue gas in the air inlet vertical section; the flue gas flow direction changes from horizontal to vertically upward in the air inlet channel, and under the action of gravity, part of the dust drops into the dust discharge hopper;

[0007] The opening of the diameter-expanding pipe faces the top of the tower body, and the height of the gas outlet channel is lower than the outlet height of the diameter-expanding pipe; after the flue gas is discharged from the diameter-expanding pipe at a reduced speed, it turns back downward and is discharged through the gas outlet channel. During this process, part of the dust is separated from the flue gas and falls into the ash storage tank.

[0008] A steam flow meter is provided on the steam supply device of the evaporation cooler to measure the mass flow rate of the steam introduced into the flue gas. Water flow meters are respectively provided on the liquid spraying devices of the evaporation cooler and the second-stage rough dust collector to measure the total mass flow rate of the water sprayed into the flue gas; regulating valves and on-off valves for dynamically adjusting the water flow rate are provided on the liquid spraying devices.

[0009] Furthermore, a cyclone is provided at one end of the intake vertical section close to the diameter-expanding pipe, and dust is separated through the cyclone.

[0010] Furthermore, a ring baffle is also provided inside the tower body. The ring baffle is located between the gas outlet channel and the ash storage tank; an opening is provided at the center of the ring baffle; the ash discharge hopper extends into the ash storage tank through the opening of the ring baffle.

[0011] Furthermore, the angle between the ring baffle and the horizontal plane is ≥40°, and is greater than the angle of repose of the dust to avoid dust accumulation; the diameter of the opening of the ring baffle is ≤ the diameter of the intake channel.

[0012] Furthermore, a gas lock valve is provided at the bottom of the ash discharge hopper, and the gas lock valve is used to discharge the settled dust into the ash storage tank.

[0013] Furthermore, an ash level monitor is provided inside the ash storage tank to monitor the ash accumulation amount in the ash storage tank.

[0014] Furthermore, temperature detection units and pressure detection units are respectively provided at the inlets and outlets of the evaporation cooler, the second-stage rough dust collector, and the dry fine dust removal device to measure the flue gas temperature and the relative pressure of the flue gas.

[0015] Furthermore, the dry fine dust removal device is a dry electrostatic precipitator and / or a dry bag filter and / or a ceramic filter cartridge dust collector.

[0016] A classification dust removal method for a converter dry dust removal system uses the classification dust removal device of the above-mentioned converter dry dust removal system to perform classification dust removal treatment on the flue gas;

[0017] During the oxygen blowing in the converter, according to the principle of heat balance, primary water spray cooling is carried out, and at the same time, part of the fine dust is coagulated and removed. The outlet temperature of the evaporation cooler is controlled at 250°C to 300°C, and the flue gas is in a superheated unsaturated state. The first-stage cooling and rough dust removal are completed in the evaporation cooler; after the flue gas is naturally cooled through the pipeline, it enters the second-stage rough dust collector. According to the principle of heat balance, water mist with a flow rate not exceeding 20% of the primary water spray flow rate in the evaporation cooler is sprayed in, and part of the fine dust is coagulated and removed again. The outlet temperature of the second-stage rough dust collector is controlled above 150°C, and the flue gas is in a superheated unsaturated state, and then it enters the subsequent dry fine dust removal device; the second-stage rough dust collector is interlocked with the inlet flue gas temperature of the fine dust removal device to adapt to different temperature drops along the pipeline, ensuring that the wet flue gas in each stage of the dry dust removal device is also in a superheated unsaturated state, and the flue gas temperature is at least 10°C higher than the dew point;

[0018] During the non-oxygen blowing period of the converter, the flue gas is only cooled by spraying water in the evaporation cooler, and no water is sprayed in the second-stage rough dust collector, which is only used as a rough dust collector; the spray device of the evaporation cooler is interlocked with the inlet flue gas temperature of the dry fine dust removal device to adapt to different temperature drops along the pipeline, ensuring that the wet flue gas in each stage of the dry dust removal device is also in a superheated unsaturated state, and the flue gas temperature is at least 10°C higher than the dew point.

[0019] Furthermore, the flue gas state and dew point temperature of the wet flue gas are calculated and determined in the following ways:

[0020] 1) The known dry flue gas flow rate under standard conditions , g / h; the dry flue gas density under standard conditions , kg / m 3 ; the atmospheric pressure , kPa;

[0021] 2) Measured by the detection unit: the flue gas temperature t r , the relative pressure of the flue gas P r and the total water mass flow rate sprayed into the flue gas before the measurement point m w , the steam mass flow rate introduced into the flue gas m v , then there is:

[0022] The absolute pressure of the flue gas , kPa;

[0023] The total moisture content of the flue gas m = m v + m w ， g / h;

[0024] The moisture content per standard cubic meter of dry flue gas = m / , g / m 3 ;

[0025] corresponding t r According to the thermodynamic water vapor property chart, the saturated gas partial pressure of water vapor under standard pressure is obtained as and the saturated moisture content of the flue gas can be calculated , g / m 3 ;

[0026] corresponding t r 、 P 、 Under the conditions of, according to the thermodynamic water vapor property chart, there is a uniquely determined dew point temperature corresponding to it; or it can be calculated by the following formula:

[0027] When 3.8 g / kg to 160 g / kg:

[0028]

[0029] When 160 g / kg to 600 g / kg:

[0030]

[0031] When the flue gas is in the superheated unsaturated state, that is < d c , it is defined as the first control condition; when t r > +10 °C, it is defined as the second control condition;

[0032] When any one of the first control condition and the second control condition is not satisfied, the following operations are performed:

[0033] 1) During the oxygen blowing period of the converter, first perform dynamic reduction adjustment on the water spray amount of the second-stage rough dust collector. If closing the water spray still cannot meet the control conditions, perform dynamic reduction adjustment on the water spray amount in the evaporation cooler until the corresponding total moisture content of the flue gas meets the first control condition and the flue gas temperature t r meets the second control condition;

[0034] 2) During the non-oxygen blowing period of the converter, perform dynamic reduction adjustment on the water spray amount in the evaporation cooler until the corresponding total moisture content of the flue gas and the flue gas temperaturet r Meet the first control condition and the second control condition respectively.

[0035] The beneficial effects of the present invention are as follows:

[0036] 1. Compared with spraying water in the evaporative cooler where the flue gas temperature drops to the target value in one step, the grading dust removal method and device provided by the present invention can effectively improve the grading dust removal efficiency of rough dust removal on the basis of maintaining the total amount of spray cooling water unchanged, reduce the load of subsequent fine dust removal, thereby extending the service life of the fine dust removal device and reducing the maintenance workload.

[0037] 2. In the second-stage rough dust collector of the present invention, the dusty flue gas from the evaporative cooler enters through the intake channel. Along the intake channel, fine liquid mist is sprayed through the liquid spraying device to coagulate and remove some fine dust. Then, it passes through a cyclone to further strengthen the dust-gas separation effect and remove some dust. The dust naturally falls into the ash discharge hopper at the bottom of the intake channel. When the flue gas flows through the enlarged-diameter pipe at the outlet and its velocity decreases, and the flue gas flows back at a low speed towards the outlet channel, dust-gas separation is completed again, and some dust is removed again. The dust naturally settles and falls into the ash storage tank at the bottom of the tower body. The flue gas then flows into the subsequent dry fine dust removal device through the outlet of the outlet channel. Three times of dust-gas separation are achieved in the second rough dust collector, improving the dust removal efficiency.

[0038] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be learned from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. Brief Description of the Drawings

[0039] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in preferred detail below in conjunction with the drawings, where:

[0040] Figure 1 is the overall schematic diagram of the grading dust removal device of the converter dry dust removal system of the present invention.

[0041] Figure 2 is the structural schematic diagram of the second-stage rough dust collector of the present invention.

[0042] Reference numerals: 1 - converter; 2 - vaporization cooling flue; 3 - evaporation cooler; 4 - second-stage rough dust collector; 5 - dry electrostatic precipitator; 6 - fan; 7 - three-way valve; 8 - chimney; 9 - gas cooler; 10 - gas holder; 11 - steam flowmeter; 12 - water flowmeter; 13 - water flowmeter; 14 - temperature measuring device; 15 - pressure measuring device; 41 - tower body; 42 - intake horizontal section; 43 - intake vertical section; 44 - outlet channel; 45 - diameter-expanding pipe; 46 - liquid spraying device; 47 - cyclone; 48 - ash discharge hopper; 49 - air-lock valve; 50 - annular baffle; 51 - ash storage tank; 52 - ash discharge valve; 53 - ash level monitor. Detailed implementation manners

[0043] The following uses specific specific examples to illustrate the implementation manners of the present invention. 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 manners. Various details in this specification can also be modified or changed 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 only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0044] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation on the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0045] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings. It 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 operated in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only for illustrative purposes and should not be construed as a limitation on the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0046] Please refer to Figures 1-2, it is a classification dust removal device for a converter dry dust removal system, including a converter 1, an evaporation cooler 3, a second-stage coarse dust collector 4, and a dry electrostatic precipitator 5 connected in series through a flue gas pipeline 2 in sequence. The outlet of the dry electrostatic precipitator 5 is connected to a fan 6, and the fan 6 is respectively connected to a chimney 8 and a gas cooler 9 through a three-way valve 7. The gas cooler 9 is connected to a gas holder 10 and leads to the user side.

[0047] Among them, the second-stage coarse dust collector 4 includes a tower body 41 and a liquid spraying device 46; a conical ash storage tank 51 is arranged at the bottom of the tower body 41; an air inlet channel and an air outlet channel 44 are arranged on the side wall of the tower body 41; the air inlet channel is L-shaped and includes an air inlet horizontal section 42 and an air inlet vertical section 43; the air inlet horizontal section 42 extends into the tower body 41 from outside the tower body 41 and is connected to the air inlet vertical section 43. The air inlet vertical section 43 is installed inside the tower body 41. An expanding pipe 45 in the shape of a cone is arranged at the upper part of the air inlet vertical section 43. A dust discharge hopper 48 is arranged at the bottom of the connection between the air inlet vertical section 43 and the air inlet horizontal section 42, and the dust discharge hopper 48 extends into the ash storage tank 51; the liquid spraying device 46 extends from outside the tower body 41 into the air inlet vertical section 43 to spray and dust-remove the flue gas in the air inlet vertical section 43; the flow direction of the flue gas changes from horizontal to vertically upward in the air inlet channel, and part of the dust drops into the dust discharge hopper 48 under the action of gravity; a cyclone 47 is arranged at one end of the air inlet vertical section 43 close to the expanding pipe 45 for separating soot and dust. A lock gas valve 49 is arranged at the bottom of the dust discharge hopper 48, and the lock gas valve 49 is used to unload the settled dust into the ash storage tank 51. The lock gas valve 49 can be a mechanical elastic diaphragm, and the diaphragm can be kept within the elastic range, opened under the action of the ash pressure in the dust discharge hopper 48, and automatically rebound and close under the action of elasticity after discharging the ash.

[0048] Among them, the opening of the expanding pipe 45 faces the top of the tower body 41, and the height of the air outlet channel 44 is lower than the outlet height of the expanding pipe 45; after the flue gas is discharged slowly through the expanding pipe 45, it turns back downward and is discharged through the air outlet channel 44 at the lower part of the tower body, and the dust drops into the ash storage tank 51 after decelerating; a ring baffle 50 is also arranged inside the tower body 41, and the ring baffle 50 is located between the air outlet channel 44 and the ash storage tank 51; an opening is arranged at the center of the ring baffle 50; the dust discharge hopper 48 extends into the ash storage tank 51 through the opening of the ring baffle 50. The included angle between the ring baffle 50 and the horizontal plane is ≥40°, and is greater than the angle of repose of the dust to avoid dust accumulation; the opening diameter of the ring baffle 50 ≤ the diameter of the air inlet channel. The dust drops onto the ring baffle 50 and slides into the ash storage tank 51. At the same time, the ring baffle 50 can prevent the airflow from impacting the accumulated ash in the ash storage tank 51 and prevent secondary dust generation.

[0049] Among them, an ash level monitor 53 is installed in the ash storage tank 51 to monitor the ash accumulation amount in the ash storage tank 51; a discharge valve 52 is installed at the bottom of the ash storage tank 51, and the discharge valve 52 is connected to a discharge pipe.

[0050] In this embodiment, a steam flowmeter 11 is provided on the steam supply device of the evaporative cooler 3 to measure the mass flow rate of the steam introduced into the flue gas. A water flowmeter 12 is installed on the liquid spraying device of the evaporative cooler 3, and a water flowmeter 13 is installed on the liquid spraying device 46 of the second-stage rough dust collector 4 to measure the total mass flow rate of the water sprayed into the flue gas. A regulating valve and a shut-off valve for dynamically adjusting the water flow rate are provided on the liquid spraying device. Temperature measuring devices 14 and pressure measuring devices 15 are provided at the inlets and outlets of the evaporative cooler 3, the second-stage rough dust collector 4, and the dry electrostatic precipitator 5 to measure the flue gas temperature and the relative pressure of the flue gas.

[0051] In this embodiment, the dry electrostatic precipitator 5 can also be replaced with a dry bag filter or a ceramic filter cartridge dust collector.

[0052] A method for classified dust removal of a converter dry dust removal system uses the classified dust removal device of the converter dry dust removal system in this embodiment to perform classified dust removal treatment on the flue gas;

[0053] During the oxygen blowing period of the converter 1, according to the principle of heat balance, primary spray water cooling is carried out, and at the same time, part of the fine dust is coagulated and removed. The outlet temperature of the evaporative cooler 3 is controlled at 250°C to 300°C, and the flue gas is in a superheated unsaturated state. The first-stage cooling and rough dust removal are completed in the evaporative cooler 3. After the flue gas naturally cools through the pipeline, it enters the second-stage rough dust collector 4. According to the principle of heat balance, water mist not exceeding 20% of the primary spray water flow rate of the evaporative cooler 3 is sprayed, and part of the fine dust is coagulated and removed again. The outlet temperature of the second-stage rough dust collector 4 is controlled above 150°C, and the flue gas is in a superheated unsaturated state, and then it enters the subsequent dry fine dust removal device. The second-stage rough dust collector 4 is interlocked with the inlet flue gas temperature of the fine dust removal device to adapt to different temperature drops along the pipeline, ensuring that the wet flue gas in each stage of the dry dust removal device is also in a superheated unsaturated state, and the flue gas temperature is at least 10°C higher than the dew point;

[0054] During the non-oxygen blowing period of the converter 1, the flue gas is only cooled by spraying water in the evaporative cooler 3, and no water is sprayed in the second-stage rough dust collector 4, which is only used as a rough dust collector. The spray device of the evaporative cooler 3 is interlocked with the inlet flue gas temperature of the dry fine dust removal device to adapt to different temperature drops along the pipeline, ensuring that the wet flue gas in each stage of the dry dust removal device is also in a superheated unsaturated state, and the flue gas temperature is at least 10°C higher than the dew point.

[0055] Among them, the flue gas state and the dew point temperature of the wet flue gas are calculated and determined by the following methods:

[0056] 1) The known dry flue gas flow rate under standard conditions , g / h; the dry flue gas density under standard conditions , kg / m 3 ; the atmospheric pressure , kPa;

[0057] 2) Measured by the detection unit: flue gas temperature t r , relative pressure of the flue gas P r and the total mass flow rate of water sprayed into the flue gas before the measuring point m w , mass flow rate of steam introduced into the flue gas m v , then there is:

[0058] Absolute pressure of the flue gas , kPa;

[0059] Total moisture content of the flue gas m = m v + m w ， , g / h;

[0060] Moisture content per standard cubic meter of dry flue gas = m / , g / m 3 ;

[0061] Corresponding to t r , according to the thermodynamic water vapor property chart, the saturated gas partial pressure of water vapor under standard pressure is , and the saturated moisture content of the flue gas can be calculated , g / m 3 ;

[0062] Corresponding to t r , P , Under the conditions, according to the thermodynamic water vapor property chart, there is a uniquely determined dew point temperature corresponding to it; or calculated by the following formula:

[0063] When 3.8 g / kg ~ 160 g / kg:

[0064]

[0065] When 160 g / kg ~ 600 g / kg:

[0066]

[0067] When the flue gas is in the superheated unsaturated state, that is < d c , defined as the first control condition; whent r > +10 °C, which is defined as the second control condition.

[0068] When any one of the first control condition and the second control condition is not satisfied, the following operations are performed:

[0069] 1) During the oxygen blowing period of the converter 1, first, the water spray amount of the secondary rough dust collector 4 is dynamically reduced. If closing the water spray still cannot meet the control conditions, the water spray amount in the evaporation cooler 3 is dynamically reduced until the corresponding total moisture content of the flue gas meets the first control condition and the flue gas temperature t r meets the second control condition;

[0070] 2) During the non-oxygen blowing period of the converter 1, the water spray amount in the evaporation cooler 3 is dynamically reduced until the corresponding total moisture content of the flue gas and the flue gas temperature t r respectively meet the first control condition and the second control condition.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. 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 modified or equivalently replaced without departing from the spirit and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for classified dust removal in a converter dry dust removal system, characterized in that: The flue gas is subjected to classified dust removal treatment by the classified dust removal device of the converter dry dust removal system; The classified dust removal device of the converter dry dust removal system includes a converter, an evaporation cooler, a second-stage rough dust collector, and a dry fine dust removal device connected in series through a flue gas pipeline in sequence; The second-stage rough dust collector includes a tower body and a liquid spraying device; a conical ash storage tank is provided at the bottom of the tower body; an air inlet channel and an air outlet channel are provided on the side wall of the tower body; the air inlet channel is L-shaped and includes an air inlet horizontal section and an air inlet vertical section; the air inlet horizontal section extends into the tower body from outside the tower body and is connected to the air inlet vertical section, the air inlet vertical section is arranged inside the tower body, a conical diameter-expanding pipe is provided at the upper part of the air inlet vertical section, a dust discharge hopper is provided at the bottom of the connection between the air inlet vertical section and the air inlet horizontal section, and the dust discharge hopper extends into the ash storage tank; the liquid spraying device extends from outside the tower body into the air inlet vertical section to spray and dust-remove the flue gas in the air inlet vertical section; The flow direction of the flue gas changes from horizontal to vertically upward in the air inlet channel, and part of the dust drops into the dust discharge hopper under the action of gravity; The opening of the diameter-expanding pipe faces the top of the tower body, and the height of the air outlet channel is lower than the outlet height of the diameter-expanding pipe; after the flue gas is discharged through the diameter-expanding pipe and decelerated, it turns back downward and is discharged through the air outlet channel. During this process, part of the dust is separated from the flue gas and drops into the ash storage tank; A steam flow meter is provided on the steam supply device of the evaporation cooler to measure the steam mass flow rate introduced into the flue gas, and water flow meters are respectively provided on the liquid spraying devices of the evaporation cooler and the second-stage rough dust collector to measure the total water mass flow rate sprayed into the flue gas; a regulating valve and a switch valve for dynamically adjusting the water flow rate are provided on the liquid spraying device; During the oxygen blowing period of the converter, according to the principle of heat balance, primary water spray cooling is carried out, and at the same time, part of the fine dust is coagulated and removed. The outlet temperature of the evaporation cooler is controlled at 250°C to 300°C, and the flue gas is in a superheated unsaturated state. The first-stage cooling and rough dust removal are completed in the evaporation cooler; the flue gas naturally cools through the pipeline and then enters the second-stage rough dust collector. According to the principle of heat balance, water mist not exceeding 20% of the primary water spray flow rate of the evaporation cooler is sprayed to coagulate and remove part of the fine dust again. The outlet temperature of the second-stage rough dust collector is controlled above 150°C, and the flue gas is in a superheated unsaturated state, and then it enters the subsequent dry fine dust removal device; The second-stage rough dust collector is interlocked with the inlet flue gas temperature of the fine dust removal device to adapt to different temperature drops along the pipeline, and ensure that the wet flue gas in each stage of the dry dust removal device is also in a superheated unsaturated state, and the flue gas temperature is at least 10°C higher than the dew point; During the non-oxygen blowing period of the converter, the flue gas is only sprayed with water for cooling in the evaporation cooler, and no water is sprayed in the second-stage rough dust collector, which is only used as a rough dust collector; the spray device of the evaporation cooler is interlocked with the inlet flue gas temperature of the dry fine dust removal device to adapt to different temperature drops along the pipeline, and ensure that the wet flue gas in each stage of the dry dust removal device is also in a superheated unsaturated state, and the flue gas temperature is at least 10°C higher than the dew point.

2. The classification dust removal method according to claim 1, characterized in that: The flue gas state and dew point temperature of the wet flue gas are calculated and determined by the following method: 1) Known dry flue gas flow rate under standard conditions , g / h; Dry flue gas density under standard conditions , kg / m 3 ; Atmospheric pressure , kPa; 2) Measured by the detection unit: flue gas temperature t r , flue gas relative pressure P r and the total water mass flow rate injected into the flue gas before the measuring point m w , the steam mass flow rate introduced into the flue gas m v , then there is: Absolute pressure of flue gas , kPa; Total moisture content of flue gas m = m v + m w ， g / h; Moisture content of per standard cubic meter of dry flue gas = m / , g / m 3 ; corresponding t r , according to the thermodynamic water vapor property chart, the saturated gas partial pressure of water vapor under standard pressure is , and the saturated moisture content of the flue gas can be calculated , g / m 3 ; corresponding t r and P and Under the conditions, according to the thermodynamic water vapor property chart, there is a uniquely determined dew point temperature corresponding to it; When the flue gas is in a superheated unsaturated state, that is < d c , it is defined as the first control condition; when t r > +10°C, it is defined as the second control condition; When any one of the first control condition and the second control condition is not satisfied, the following operations are performed: 1) During the oxygen blowing period of the converter, first, dynamically reduce the water spray volume of the second-stage rough dust collector. If closing the water spray still cannot meet the control conditions, then dynamically reduce the water spray volume in the evaporation cooler until the total moisture content of the corresponding flue gas meets the first control condition and the flue gas temperature t r meets the second control condition; 2) During the period when the converter is not blowing oxygen, dynamically reduce the amount of water sprayed in the evaporative cooler until the total moisture content of the corresponding flue gas and the flue gas temperature t r respectively meet the first control condition and the second control condition.

3. The classification dust removal method according to claim 1, wherein: A cyclone is provided at one end of the intake vertical section close to the diameter-expanding pipe, and dust separation is carried out through the cyclone.

4. The grading dust removal method according to claim 1, characterized in that: A ring baffle is further provided in the tower body, and the ring baffle is located between the air outlet channel and the ash storage tank; an opening is provided at the center of the ring baffle; the ash discharge hopper extends into the ash storage tank through the opening of the ring baffle.

5. The classification dust removal method according to claim 4, wherein: The included angle between the ring baffle and the horizontal plane is ≥40°, and is greater than the angle of repose of the dust to avoid dust accumulation; the diameter of the opening of the ring baffle is ≤ the diameter of the intake channel.

6. The classification dust removal method according to claim 1, characterized in that: A gas locking valve is provided at the bottom of the ash discharge hopper, and the gas locking valve is used to discharge the settled dust into the ash storage tank.

7. The grading dust removal method according to claim 1, characterized in that: An ash level monitor is provided in the ash storage tank for monitoring the ash accumulation amount in the ash storage tank.

8. The classification dust removal method according to claim 1, characterized in that: Temperature detection units and pressure detection units are provided at the inlets and outlets of the evaporation cooler, the second-stage rough dust collector, and the dry fine dust removal device to measure the flue gas temperature and the relative pressure of the flue gas.

9. The classified dust removal method according to claim 1, characterized in that: The dry fine dust removal device is a dry electrostatic precipitator and / or a dry bag filter and / or a ceramic filter cartridge dust collector.

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