A slag micro-powder low-temperature flue gas circulating energy-saving drying process based on negative pressure control

Abstract

This invention discloses a low-temperature flue gas circulation energy-saving drying process for slag micron powder based on negative pressure control, comprising the following steps: (1) adding a circulating flue gas electric regulating valve, a flue gas flow meter, and a flue gas temperature sensor to the main exhaust fan outlet pipeline of the micron powder mill; installing a negative pressure transmitter in the furnace of the hot blast stove; and configuring a gas flow regulating valve and a gas meter in the gas inlet pipeline of the hot blast stove; (2) collecting the instantaneous flow rate of the circulating flue gas, the circulating flue gas temperature, the negative pressure of the furnace of the hot blast stove, and the gas consumption of the hot blast stove in real time; (3) automatically adjusting the opening of the circulating flue gas electric regulating valve; (4) sending the circulating flue gas into the drying system and automatically reducing the gas supply of the hot blast stove according to the residual heat it brings in; (5) recording the negative pressure data, the flue gas blending ratio, the circulating flue gas temperature, the instantaneous gas consumption, and the daily output of micron powder in real time; and (6) dynamically correcting the upper limit of the circulating flue gas blending ratio according to the amount of blast furnace slag supplied. This invention achieves a significant reduction in gas consumption per ton of pulverized coal.

Description

Technical Field

[0001] This invention relates to the field of slag powder production technology, specifically to a low-temperature flue gas circulation energy-saving drying process for slag powder based on negative pressure control. Background Technology

[0002] In the production of slag powder, the raw material, slag, has a high moisture content, requiring a hot blast stove to burn blast furnace gas to generate a high-temperature heat source for drying. Current processes only incorporate 30% of the mill exhaust gas for recycling, while the remaining 85-95°C mill exhaust gas is directly vented, resulting in a significant waste of low-temperature waste heat. To supplement the drying heat, the hot blast stove continuously consumes a large amount of blast furnace gas, leading to high production costs. Blindly increasing the proportion of recycled flue gas would cause excessive flue gas to flood the hot blast system, disrupting the furnace negative pressure and causing problems such as the hot blast stove negative pressure dropping below -100Pa, furnace depressurization and flameout, and production interruptions. The industry generally faces limitations due to the negative pressure, making it impossible to further increase the flue gas recycling rate. Therefore, developing an intelligent control process that uses the hot blast stove negative pressure range as a control benchmark and precisely matches the circulating air volume to maximize the recovery of low-temperature waste heat from the mill while ensuring equipment safety and reducing the high gas consumption per unit area has become an urgent problem to solve. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide a low-temperature flue gas circulation energy-saving drying process for slag micronized powder based on negative pressure control. This process overcomes the shortcomings of existing flue gas blending, low waste heat utilization, and high coal gas consumption. Under the condition that the negative pressure of the hot blast stove is stably controlled within the safe range of -100Pa to -120Pa, the blending ratio of the low-temperature circulating flue gas at the outlet of the micronized powder mill at 85-95℃ is increased from the original 30% to 40%. By relying on the low-temperature waste heat to replace the coal gas generated by the hot blast stove, the coal gas consumption per ton of pulverized coal is significantly reduced.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: The present invention provides a low-temperature flue gas circulation energy-saving drying process for slag micron powder based on negative pressure control, the innovation of which lies in including the following steps: (1) A circulating flue gas electric regulating valve, a flue gas flow meter and a flue gas temperature sensor are sequentially and spaced on the main exhaust fan outlet pipe of the micro powder mill. A negative pressure transmitter is installed in the furnace of the hot blast stove, and a gas flow regulating valve and a gas meter are installed on the gas inlet pipe of the hot blast stove. (2) The instantaneous flow rate of circulating flue gas, the temperature of circulating flue gas T, the negative pressure P of the hot blast stove furnace and the gas consumption of the hot blast stove are collected in real time by the flue gas flow meter, the flue gas temperature sensor, the negative pressure transmitter and the gas meter, respectively, and the collected data are transmitted to the DCS / PLC control system. (3) The DCS / PLC control system presets a negative pressure safety threshold and automatically adjusts the opening of the circulating flue gas electric regulating valve according to the negative pressure safety threshold to achieve negative pressure closed-loop interlock control. (4) 40% of the circulating flue gas is sent into the drying system to replace the original hot air furnace high-temperature gas heat source. The DCS / PLC control system automatically adjusts the hot air furnace gas supply according to the waste heat brought in by the circulating flue gas, so as to realize the precise replacement of gas with waste heat. (5) The DCS / PLC control system records negative pressure data, flue gas blending ratio, circulating flue gas temperature, instantaneous coal gas consumption and daily output of micro powder in real time. (6) The upper limit ratio of circulating flue gas is dynamically adjusted according to the amount of blast furnace slag. When the amount of slag is reduced, the flue gas ratio is automatically reduced to avoid negative pressure disturbance in the system.

[0005] Preferably, in step (1) above, the circulating flue gas electric regulating valve, flue gas flow meter, flue gas temperature sensor, negative pressure transmitter, gas flow regulating valve and gas meter are all electrically connected to the DCS / PLC control system, and the flue gas flow meter has an accuracy of ±1%, the flue gas temperature sensor has an accuracy of ±0.5℃, and the negative pressure transmitter has an accuracy of ±0.5%.

[0006] Preferably, in step (3) above, the preset negative pressure safety threshold of the DCS / PLC control system is -120Pa≤P≤-100Pa.

[0007] Preferably, in step (3) above, the specific reference for automatically adjusting the opening of the circulating flue gas electric regulating valve based on the negative pressure safety threshold is as follows: (3.1) When the furnace negative pressure is > -100Pa, the DCS / PLC control system automatically increases the opening of the circulating flue gas electric regulating valve to increase the proportion of flue gas blending. (3.2) When the furnace negative pressure is less than -120Pa, the DCS / PLC control system automatically reduces the opening of the circulating flue gas electric regulating valve to reduce the flue gas flow rate.

[0008] Preferably, in step (3.1) above, the proportion of flue gas blending is calculated based on the total flow rate of flue gas at the outlet of the micro powder mill, and the maximum value of the proportion of flue gas blending is limited to 40%.

[0009] Preferably, in step (3.2) above, the DCS / PLC control system uses a 4-20mA analog signal + PID algorithm to finely adjust the opening of the circulating flue gas electric regulating valve in real time, and the control cycle of the PID algorithm is 1-5 seconds, and dynamically locks the upper limit of the circulating flue gas ratio to 40%.

[0010] Preferably, in step (4) above, the DCS / PLC control system calculates the waste heat brought in by the flue gas based on the product of the flue gas temperature T and the instantaneous flow rate of the flue gas, and determines the reduction range of the hot blast stove gas supply based on the difference between the waste heat and the hot blast stove heat load, and stabilizes the hot blast stove gas consumption at 22000~24000m³ through the gas flow regulating valve. 3 / h.

[0011] Preferably, in step (5) above, the data continuously recorded by the DCS / PLC control system must be stored for a period of ≥1 year in order to achieve full traceability of energy consumption.

[0012] Preferably, in step (6) above, the baseline value of the blast furnace slag feed is 6000t per day and 5700t per day of micro powder production.

[0013] The beneficial effects of this invention are: (1) This invention overcomes the shortcomings of existing flue gas blending, low waste heat utilization rate and large coal gas consumption. Under the condition that the negative pressure of the hot blast stove is stably controlled in the safe range of -100Pa to -120Pa, the blending ratio of the low temperature circulating flue gas at 85 to 95°C at the outlet of the micro powder mill is increased from the original 30% to 40%. By relying on the low temperature waste heat to replace the coal gas in the hot blast stove to generate heat, the coal gas consumption per ton of pulverized coal is greatly reduced. (2) This invention significantly reduces gas consumption, resulting in significant cost reduction and efficiency improvement; (3) The equipment of the present invention is safe and controllable in operation, and through negative pressure closed-loop interlock control, the hot air furnace is prevented from losing pressure and shutting down due to excessive flue gas. (4) This invention reduces the emission of waste gas by utilizing waste heat resources, thus achieving both energy-saving and environmental protection benefits. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of a low-temperature flue gas circulation energy-saving drying process for slag micro powder based on negative pressure control, according to the present invention. Detailed Implementation

[0016] The technical solution of the present invention will be clearly and completely described below through specific embodiments.

[0017] This invention provides an energy-saving drying process for slag powder using low-temperature flue gas circulation based on negative pressure control, such as... Figure 1As shown, it includes the following steps: (1) A circulating flue gas electric regulating valve, a flue gas flow meter and a flue gas temperature sensor are sequentially and intermittently installed on the main exhaust fan outlet pipe of the micro powder mill. A negative pressure transmitter is installed in the furnace of the hot blast stove, and a gas flow regulating valve and a gas meter are installed on the gas inlet pipe of the hot blast stove.

[0018] The circulating flue gas electric regulating valve, flue gas flow meter, flue gas temperature sensor, negative pressure transmitter, gas flow regulating valve, and gas meter of this invention are all electrically connected to the DCS / PLC control system. The flue gas flow meter has an accuracy of ±1%, the flue gas temperature sensor has an accuracy of ±0.5℃, and the negative pressure transmitter has an accuracy of ±0.5%.

[0019] (2) The instantaneous flow rate of circulating flue gas, the temperature of circulating flue gas T, the negative pressure P of the hot blast stove furnace and the gas consumption of the hot blast stove are collected in real time by the flue gas flow meter, the flue gas temperature sensor, the negative pressure transmitter and the gas meter, respectively, and the collected data are transmitted to the DCS / PLC control system.

[0020] (3) The DCS / PLC control system presets a negative pressure safety threshold and automatically adjusts the opening of the circulating flue gas electric regulating valve according to the negative pressure safety threshold to achieve negative pressure closed-loop interlock control.

[0021] The preset negative pressure safety threshold of the DCS / PLC control system of this invention is -120Pa≤P≤-100Pa.

[0022] The specific criteria for automatically adjusting the opening of the circulating flue gas electric regulating valve based on the negative pressure safety threshold in this invention are as follows: (3.1) When the furnace negative pressure is > -100Pa, the DCS / PLC control system automatically increases the opening of the circulating flue gas electric regulating valve to increase the proportion of flue gas blending. The proportion of flue gas blending is calculated based on the total flow rate of flue gas at the outlet of the micro powder mill, and the maximum value of the proportion of flue gas blending is limited to 40%.

[0023] (3.2) When the furnace negative pressure is <-120Pa, the DCS / PLC control system automatically reduces the opening of the circulating flue gas electric regulating valve to reduce the flue gas flow rate, ensure that the hot blast stove negative pressure is within a safe range, and prevent flameout failure. The DCS / PLC control system uses a 4-20mA analog signal and a PID algorithm to finely adjust the opening of the circulating flue gas electric regulating valve in real time. The control cycle of the PID algorithm is 1-5 seconds, and it dynamically locks the upper limit of the circulating flue gas ratio to 40%.

[0024] (4) 40% of the circulating flue gas is sent into the drying system to replace the original high-temperature gas heat source of the hot air furnace, and the DCS / PLC control system automatically adjusts the gas supply of the hot air furnace according to the waste heat brought in by the circulating flue gas, so as to realize the precise replacement of gas with waste heat.

[0025] The DCS / PLC control system of this invention calculates the waste heat brought in by the circulating flue gas based on the product of the circulating flue gas temperature T and the instantaneous flow rate of the circulating flue gas. It then determines the reduction range of the hot blast stove gas supply based on the difference between this waste heat and the hot blast stove heat load, and uses a gas flow regulating valve to stably control the hot blast stove gas consumption between 22000 and 24000 m³ / h. 3 / h.

[0026] (5) The DCS / PLC control system records negative pressure data, flue gas blending ratio, circulating flue gas temperature, instantaneous coal gas consumption and daily output of micro powder in real time.

[0027] The data continuously recorded by the DCS / PLC control system of this invention must be stored for at least one year to achieve full traceability of energy consumption.

[0028] (6) The upper limit ratio of circulating flue gas is dynamically adjusted according to the amount of blast furnace slag. When the amount of slag is reduced, the flue gas ratio is automatically reduced to avoid negative pressure disturbance in the system.

[0029] The baseline values ​​for the blast furnace slag feed rate in this invention are 6000t of daily feed and 5700t of daily micro powder production.

[0030] The beneficial effects of this invention are: (1) This invention overcomes the shortcomings of existing flue gas blending, low waste heat utilization rate and large coal gas consumption. Under the condition that the negative pressure of the hot blast stove is stably controlled in the safe range of -100Pa to -120Pa, the blending ratio of the low temperature circulating flue gas at 85 to 95°C at the outlet of the micro powder mill is increased from the original 30% to 40%. By relying on the low temperature waste heat to replace the coal gas in the hot blast stove to generate heat, the coal gas consumption per ton of pulverized coal is greatly reduced. (2) This invention significantly reduces gas consumption, resulting in significant cost reduction and efficiency improvement; (3) The equipment of the present invention is safe and controllable in operation, and through negative pressure closed-loop interlock control, the hot air furnace is prevented from losing pressure and shutting down due to excessive flue gas. (4) This invention reduces the emission of waste gas by utilizing waste heat resources, thus achieving both energy-saving and environmental protection benefits.

[0031] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, all modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope of the present invention. The technical content for which protection is sought in the present invention has been fully described in the technical requirements.

Claims

1. A slag powder low-temperature flue gas circulating energy-saving drying process based on negative pressure management, characterized by Includes the following steps: (1) A circulating flue gas electric regulating valve, a flue gas flow meter and a flue gas temperature sensor are sequentially and spaced on the main exhaust fan outlet pipe of the micro powder mill. A negative pressure transmitter is installed in the furnace of the hot blast stove, and a gas flow regulating valve and a gas meter are installed on the gas inlet pipe of the hot blast stove. (2) The instantaneous flow rate of circulating flue gas, the temperature of circulating flue gas T, the negative pressure P of the hot blast stove furnace and the gas consumption of the hot blast stove are collected in real time by the flue gas flow meter, the flue gas temperature sensor, the negative pressure transmitter and the gas meter, respectively, and the collected data are transmitted to the DCS / PLC control system. (3) The DCS / PLC control system presets a negative pressure safety threshold and automatically adjusts the opening of the circulating flue gas electric regulating valve according to the negative pressure safety threshold to achieve negative pressure closed-loop interlock control. (4) 40% of the circulating flue gas is sent into the drying system to replace the original hot air furnace high-temperature gas heat source. The DCS / PLC control system automatically adjusts the hot air furnace gas supply according to the waste heat brought in by the circulating flue gas, so as to realize the precise replacement of gas with waste heat. (5) The DCS / PLC control system records negative pressure data, flue gas blending ratio, circulating flue gas temperature, instantaneous coal gas consumption and daily output of micro powder in real time. (6) The upper limit ratio of circulating flue gas is dynamically adjusted according to the amount of blast furnace slag. When the amount of slag is reduced, the flue gas ratio is automatically reduced to avoid negative pressure disturbance in the system.

2. The slag powder low-temperature flue gas circulating energy-saving drying process based on negative pressure control according to claim 1, characterized in that: In step (1) above, the circulating flue gas electric regulating valve, flue gas flow meter, flue gas temperature sensor, negative pressure transmitter, gas flow regulating valve and gas meter are all electrically connected to the DCS / PLC control system, and the flue gas flow meter has an accuracy of ±1%, the flue gas temperature sensor has an accuracy of ±0.5℃, and the negative pressure transmitter has an accuracy of ±0.5%.

3. The slag powder low-temperature flue gas circulating energy-saving drying process based on negative pressure control according to claim 1, characterized in that: In step (3) above, the preset negative pressure safety threshold of the DCS / PLC control system is -120Pa≤P≤-100Pa.

4. The slag powder low-temperature flue gas circulating energy-saving drying process based on negative pressure control according to claim 3, characterized in that: In step (3) above, the specific reference for automatically adjusting the opening of the circulating flue gas electric regulating valve based on the negative pressure safety threshold is as follows: (3.1) When the furnace negative pressure is > -100Pa, the DCS / PLC control system automatically increases the opening of the circulating flue gas electric regulating valve to increase the proportion of flue gas blending. (3.2) When the furnace negative pressure is less than -120Pa, the DCS / PLC control system automatically reduces the opening of the circulating flue gas electric regulating valve to reduce the flue gas flow rate.

5. The slag powder low-temperature flue gas circulating energy-saving drying process based on negative pressure control according to claim 4, characterized in that: In step (3.1) above, the proportion of flue gas blending is calculated based on the total flow rate of flue gas at the outlet of the micro powder mill, and the maximum value of the proportion of flue gas blending is limited to 40%.

6. The slag powder low-temperature flue gas circulating energy-saving drying process based on negative pressure control according to claim 4, characterized in that: In step (3.2) above, the DCS / PLC control system uses a 4-20mA analog signal + PID algorithm to finely adjust the opening of the circulating flue gas electric regulating valve in real time. The control cycle of the PID algorithm is 1-5 seconds, and the upper limit of the circulating flue gas ratio is dynamically locked to 40%.

7. The low-temperature flue gas circulation energy-saving drying process for slag micro powder based on negative pressure control according to claim 1, characterized in that: In step (4) above, the DCS / PLC control system calculates the waste heat brought in by the flue gas based on the product of the flue gas temperature T and the instantaneous flow rate of the flue gas, and determines the reduction range of the hot blast stove gas supply based on the difference between the waste heat and the hot blast stove heat load, and stabilizes the hot blast stove gas consumption at 22000~24000 m³ / h through the gas flow regulating valve. 3 / h.

8. The slag powder low-temperature flue gas circulating energy-saving drying process based on negative pressure control according to claim 1, characterized in that: In step (5) above, the data continuously recorded by the DCS / PLC control system must be stored for a period of ≥1 year in order to achieve full traceability of energy consumption.

9. The slag powder low-temperature flue gas circulating energy-saving drying process based on negative pressure control according to claim 1, characterized in that: In the above step (6), the reference value of the blast furnace slag feedstock amount is 6000 tons per day, and the reference value of the micro powder production is 5700 tons per day.

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