Dry quenching tail gas purification chemical control method

Abstract

The invention relates to a dry quenching tail gas purification chemical engineering control method. The method comprises the following steps: step 1, carrying out grinding and conveying by a grinding and conveying system; step 2, controlling flue gas; step 3, carrying out desulfurization treatment on tail gas; according to the scheme, sodium bicarbonate powder and SO2 in coke oven dry quenching tail gas react, and the problems that in the dry quenching tail gas purification process, the flue gas temperature is unstable, the given amount of sodium bicarbonate fluctuates, and the recycling controllability of solid waste in a bag-type dust collector is not high are solved. And finally, the components of the dry quenching tail gas meet the requirement of environment-friendly emission.

Description

Technical Field

[0001] The present invention relates to a control method. During the process of cooling coke by the coke dry quenching process in a coke oven, tail gas containing pollutant sulfur components and other particulate matters is generated. In order to achieve environmental protection emissions, a tail gas treatment process is developed, which belongs to the technical field of coke oven processes. Background Art

[0002] Coke dry quenching in a coke oven is an environmental protection and energy-saving process for coke ovens. After the hot coke is pushed out of the coke oven carbonization chamber, the 1200°C coke is charged into the coke dry quenching furnace. Low-temperature inert gas is introduced into the red coke layer from the cooling section of the coke dry quenching furnace, absorbing the heat of the red coke. The cooled coke is discharged from the bottom of the coke dry quenching furnace. The inert gas heated to 700°C after absorbing heat flows through the coke dry quenching boiler for heat exchange to generate steam for power generation. The cooled inert gas is re-injected into the coke dry quenching furnace by a circulation fan to realize the recycling of inert gas in a closed system. In actual production, the overall pressure is balanced during the circulation of the inert gas. However, when the inert gas cools the red coke from 1200°C to 130°C, various gases are generated, and the generated gases must be discharged from the circulation system to ensure the pressure balance of the system. This is the emission of the coke dry quenching tail gas.

[0003] The main components of the coke dry quenching tail gas are: SO2 500 mg / Nm3 and dust 1000 mg / Nm3. The requirements for environmental protection emission limits are: SO2 < 35 mg / Nm3 and dust < 10 mg / Nm3. In this method for purifying the tail gas, sodium bicarbonate powder reacts with the SO2 component in the tail gas under high-temperature conditions to produce solid sodium sulfate powder, and then the bag dust removal process is used to recover the generated sodium sulfate powder and other dust in the tail gas, realizing the coke dry quenching tail gas purification process.

[0004] In actual retrieval:

[0005] A sodium bicarbonate dry flue gas desulfurization system (Patent No.: 201922120438.4) mainly introduces a sodium bicarbonate desulfurization process system. Although both use sodium bicarbonate for desulfurization, its equipment and system cannot be used for the purification of coke dry quenching tail gas. The key of this technical solution is not only to use the sodium bicarbonate desulfurization process, but also to improve the reaction efficiency at the low-temperature state of coke dry quenching through the control scheme.

[0006] A coke dry quenching dust removal and flue gas desulfurization device (Patent No.: 202121843692.8) mainly introduces a device for wet treatment of the tail gas in pipelines such as the flue gas pipeline of the coke dry quenching pre-storage chamber, the flue gas pipeline of the discharge vibrating feeder, and the flue gas pipeline of the charging device generated by the coke dry quenching tail gas. This technical solution mainly adopts the sodium bicarbonate dry desulfurization scheme, and the treated tail gas is not pipeline gas, but the gas generated by the coke dry quenching reaction.

[0007] In actual production, the method of reacting sodium bicarbonate with the SO2 component in the tail gas is also adopted in many areas. However, the actual reaction efficiency is about 25%. The reason is that the system reaction temperature is low and the control method is rough. Therefore, there is an urgent need for a new solution to solve the above technical problems. Summary of the Invention

[0008] The present invention precisely aims at the problems existing in the prior art and provides a control method for the purification of the tail gas of coke dry quenching. This technical solution uses sodium bicarbonate powder to react with the SO2 component in the tail gas of coke oven dry quenching, solves the problems such as unstable flue gas temperature, fluctuating sodium bicarbonate feeding amount, and weak controllability of the recovery of solid waste in the bag filter in the purification process of the tail gas of coke dry quenching. Through the solution of the problems, the components of the tail gas of coke dry quenching finally meet the requirements of environmental protection emissions.

[0009] In order to achieve the above object, the technical solution of the present invention is as follows. A control method for the purification of the tail gas of coke dry quenching, the method comprising the following steps:

[0010] Step 1: Conduct grinding and conveying through the grinding and conveying system.

[0011] Step 2: Control the flue gas.

[0012] Step 3: Conduct desulfurization treatment on the tail gas.

[0013] Step 4: Conduct dust removal and then desulfurization treatment.

[0014] Among them, the grinding and conveying system in Step 1 includes a sodium bicarbonate particle inlet, a storage tank, a radar level gauge, a hopper, a screw conveyor, a grinding motor, a grinder, a pneumatic conveying fan, a sodium bicarbonate powder heating device, and a sodium bicarbonate powder classifier. The sodium bicarbonate particle inlet is arranged above the storage tank. Below the storage tank, a hopper, a screw conveyor, and a grinder are sequentially arranged. Among them, the grinding motor is arranged on one side of the grinder to drive the grinder to work. Above the grinder, a pneumatic conveying fan is arranged. The pneumatic conveying fan is connected to the purification reactor through a pipeline. A sodium bicarbonate powder heating device is arranged between the pneumatic conveying fan and the purification reactor. The chambers of the grinder, the pneumatic conveying fan, and the sodium bicarbonate powder classifier 21 are connected as a whole.

[0015] Among them, the specific process of Step 1 is as follows: Sodium bicarbonate is added through the sodium bicarbonate particle inlet 1. After passing through the storage tank 2, it enters the hopper 4. The radar level gauge 3 is used to detect the change in its level. After being conveyed by the screw conveyor 5 into the grinder 7 for grinding, and then screened by the sodium bicarbonate powder classifier 21, the ultrafine sodium bicarbonate powder is sprayed into the purification reactor 10 through the pneumatic conveying fan 8 and the pipeline 18. In order to ensure the reaction efficiency, a sodium bicarbonate powder heating device 9 is arranged at the front end of entering the purification reactor to heat the ultrafine sodium bicarbonate powder to 170°C.

[0016] Among them, the flue gas control system in step 2 includes

[0017] a purification reactor, an SO content meter at the inlet of the dust collector, 2 , 2 an SO content detector at the chimney outlet of the dust collector, the gas discharged from the chimney of the dust collector, a dust bin collector of the dust collector, an induced draft fan for tail gas, an input of dry quenching coke tail gas, an inhalation of dry quenching coke tail gas, an output of the gas after desulfurization reaction, a dry-type dust collector, a cut-off valve for the dry quenching coke tail gas introduction pipeline, a pipeline regulating valve, a flow meter, a first temperature meter, a pressure meter, a cut-off valve for the connecting pipe, a regulating valve for the connecting pipe, a second temperature meter, and a connecting pipe

[0018] There is an input of dry quenching coke tail gas between the purification reactor and the induced draft fan for tail gas. The inhalation of dry quenching coke tail gas is connected to the induced draft fan for tail gas. There is an output of the gas after desulfurization reaction between the purification reactor and the dry-type dust collector. A cut-off valve for the dry quenching coke tail gas introduction pipeline, a pipeline regulating valve, and a flow meter are configured from the flue gas inlet. A temperature detection element is added in front of the purification reactor. A connecting pipe is added between the tail gas introduction pipelines of two coke ovens, and a regulating valve for the connecting pipe is installed, which can realize the flow regulation between the two pipelines. And a pressure meter is configured at the inlet of the connecting pipe. After passing through the purification reactor, there is a system induced draft fan for tail gas. Using such a configuration, a closed-loop control of the introduced air volume and the mixed air temperature can be established.

[0019] Among them, in step 2: controlling the flue gas is as follows: Usually, more than two coke ovens are used for simultaneous production, mainly to ensure that the coke oven gas generated by the coking of the coke oven does not stop during the use in other processes. For each coke oven 30, the dry quenching coke tail gas is led out from the flue gas inlet. On the conveying pipeline, a cut-off valve 22 for the dry quenching coke tail gas introduction pipeline, a pipeline regulating valve 23, a flow meter 24, and a first meter 25 are configured; a connecting pipe 31 is added between the tail gas introduction pipelines of two coke ovens, and a regulating valve 28 for the connecting pipe and a cut-off valve 27 for the connecting pipe are installed on the connecting pipe to realize the flow regulation between the two pipelines. And a pressure meter 26 is configured at the inlet of the connecting pipe. After the dry quenching coke tail gas passes through the introduction pipeline, it is introduced into the purification reactor 10 from the inhalation 17 of the dry quenching coke tail gas by the induced draft fan 15 through the pipeline.

[0020] Among them, in step 3 for desulfurizing the tail gas, 20-μm sodium bicarbonate powder is heated at 170°C by a heating tape under the action of a pneumatic conveying fan 8 through a conveying pipeline 18 before passing through the Venturi atomization, so that NaHCO 3 ​​When the powder temperature is 150°C, it can greatly make up for the insufficient flue gas temperature. The 20-μm sodium bicarbonate powder is mixed with the coke dry quenching tail gas and enters the sodium bicarbonate powder classifier. Under high-temperature conditions, the sodium bicarbonate powder is activated and reacts with the SO2 component in the high-temperature coke oven tail gas in the purification reactor. There is no physical structure in the tail gas reactor, mainly realizing the spray-like mixing reaction of the high-temperature tail gas and the sodium bicarbonate powder. The reaction time is directly determined by the flow rate of the tail gas induced draft fan for the tail gas.

[0021] Among them, step 4: dust removal and desulfurization treatment is as follows:

[0022] Under the action of the tail gas induced draft fan, the coke dry quenching tail gas and the 20-μm sodium bicarbonate powder are mixed in the purification reactor 10. Under high-temperature conditions, the sodium bicarbonate powder is activated and reacts with the SO 2 component in the reactor to form Na 2 SO 4 dust. Under the action of the tail gas induced draft fan 15, the reactants and other components in the coke dry quenching tail gas are adsorbed and purified by the bag filter 20. The particulate matter in the reactants and the tail gas realizes dust removal separation, and the purification and discharge of the tail gas are realized. After all the reactions are completed, Na 2 SO 4 , the particulate matter of the coke dry quenching flue gas, etc. are dust-removed and settled by the dust collector, and finally discharged and collected through the dust collector ash bin collector, realizing recycling, and the reaction efficiency reaches more than 65%.

[0023] Compared with the prior art, the present invention has the following advantages. The scheme is ingeniously designed. After all the reactions are completed, Na 2 SO 4 , the particulate matter of the coke dry quenching flue gas, etc. are dust-removed and settled by the dust collector, and finally discharged and collected through the dust collector ash bin collector ( Figure 1 12 in it) to realize recycling, and the reaction efficiency reaches more than 65%. This scheme solves the problems such as unstable flue gas temperature, fluctuating sodium bicarbonate feeding amount, and poor controllability of solid waste recovery in the coke dry quenching tail gas purification process. Through the solution of the problems, the components of the coke dry quenching tail gas finally meet the requirements of environmental protection emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of the dry desulfurization process for coke dry quenching tail gas;

[0025] Figure 2 is a schematic diagram of the process for introducing coke dry quenching tail gas;

[0026] Figure 3 is a schematic diagram of the circulation and extraction of coke dry quenching tail gas;

[0027] Figure 4 is a flow chart of the purification of coke dry quenching tail gas.

[0028] In the figure: 1. Sodium bicarbonate granule inlet; 2. Storage tank; 3. Radar level gauge; 4. Hopper; 5. Screw conveyor; 6. Grinding motor; 7. Grinder; 8. Pneumatic conveying fan; 9. Sodium bicarbonate powder heating device; 10. Purification reactor; 11. SO 2 content meter at the dust collector inlet; 12. SO 2 content detector at the chimney of the dust collector; 13. Exhaust gas discharged from the chimney of the dust collector; 14. Dust collector ash bin collector; 15. Tail gas induced draft fan; 16. Input of coke dry quenching tail gas; 17. Inhalation of coke dry quenching tail gas; 18. Input of sodium bicarbonate powder; 19. Output of gas after desulfurization reaction; 20. Dry dust collector; 21. Sodium bicarbonate powder classifier; 22. Cut-off valve for the pipeline introducing coke dry quenching tail gas; 23. Pipeline regulating valve; 24. Flow meter; 25. First thermometer; 26. Pressure gauge; 27. Cut-off valve for the connecting pipe; 28. Connecting pipe regulating valve; 29. Second thermometer; 30. Schematic diagram of coke oven; 31. Connecting pipe; 32. Position where the tail gas of the traditional tail gas purification process is led out. Specific implementation mode

[0029] To deepen the understanding of the present invention, the following detailed description is given to this embodiment in conjunction with the attached drawings.

[0030] Embodiment 1: Refer to Figure 1 , a control method for purifying coke dry quenching tail gas, the method comprising the following steps:

[0031] Step 1: Conduct grinding and conveying by the grinding and conveying system,

[0032] Step 2: Control the flue gas,

[0033] Step 3: Conduct desulfurization treatment on the tail gas,

[0034] Step 4: Conduct dust removal and then desulfurization treatment.

[0035] Among them, the grinding and conveying system in Step 1 includes a sodium bicarbonate granule inlet 1, a storage tank 2, a radar level gauge 3, a hopper 4, a screw conveyor 5, a grinding motor 6, a grinder 7, a pneumatic conveying fan 8, a sodium bicarbonate powder heating device 9, and a sodium bicarbonate powder classifier 21. The sodium bicarbonate granule inlet 1 is arranged above the storage tank 2. Below the storage tank 2, a hopper 4, a screw conveyor 5, and a grinder 7 are arranged in sequence. Among them, the grinding motor 6 is arranged on one side of the grinder 7 to drive the grinder 7 to work. Above the grinder 7, a pneumatic conveying fan 8 is arranged. The pneumatic conveying fan 8 is connected to the purification reactor 10 through a pipeline. A sodium bicarbonate powder heating device 9 is arranged between the pneumatic conveying fan 8 and the purification reactor 10. The chambers of the grinder 7, the pneumatic conveying fan 8, and the sodium bicarbonate powder classifier 21 are connected as a whole.

[0036] The specific process of step 1 is as follows: sodium bicarbonate is added through the sodium bicarbonate particle addition port 1, passes through the material tank 2, enters the hopper 4, and uses the radar level meter 3 to detect the material level change. It is conveyed to the grinder 7 for grinding through the screw conveyor 5, and then screened by the sodium bicarbonate powder classifier 21. After passing through the pneumatic conveying fan 8, the sodium bicarbonate ultrafine powder is sprayed into the purification reactor 10 through the pipeline 18. In order to ensure the reaction efficiency, a sodium bicarbonate powder heating device 9 is set at the front end of the purification reactor to heat the sodium bicarbonate ultrafine powder to 170°C.

[0037] Among them, the smoke control system in step 2 includes

[0038] Purification reactor 10, dust collector inlet SO 2 Content meter 11, dust collector chimney outlet SO 2 Content detector 12, dust collector chimney exhaust gas 13, dust collector ash bin collector 14, tail gas induced draft fan 15, dry coke quenching tail gas input 16, dry coke quenching tail gas suction 17, desulfurization reaction gas output 19, dry dust collector 20, dry coke quenching tail gas introduction pipeline shut-off valve 22, pipeline regulating valve 23, flow meter 24, first temperature meter 25, pressure meter 26, connecting pipe shut-off valve 27, connecting pipe regulating valve 28, second temperature meter 29 and connecting pipe 31,

[0039] A dry coke quenching tail gas input 16 is provided between the purification reactor 10 and the tail gas induced draft fan 15, and the dry coke quenching tail gas suction 17 is connected to the tail gas induced draft fan 15. A post-desulfurization reaction gas output 19 is provided between the purification reactor 10 and the dry dust collector 20. A dry coke quenching tail gas introduction pipeline cut-off valve 22, a pipeline regulating valve 23, and a flow meter 24 are arranged from the flue gas inlet. A temperature detection element is added in front of the purification reactor. A connecting pipe 31 is added between the tail gas introduction pipelines of the two coke ovens, and a connecting pipe regulating valve 28 is installed to realize flow regulation between the two pipelines. A pressure gauge 26 is arranged at the inlet of the connecting pipe. After passing through the purification reactor, there is a system tail gas induced draft fan. Such a configuration can establish a closed-loop control of the introduced air volume and mixed air temperature.

[0040] Among them, Step 2: Control the flue gas as follows: Usually, more than two coke ovens are used for simultaneous production, mainly to ensure that the coke oven gas produced by the dry distillation of the coke oven does not stop during use in other processes. For each coke oven 30, the dry quenching tail gas is led out from the flue gas inlet. On the conveying pipeline, a dry quenching tail gas inlet pipeline cut-off valve 22, a pipeline regulating valve 23, a flow meter 24, and a first meter 25 are configured; A connecting pipe 31 is added between the tail gas inlet pipelines of the two coke ovens. A connecting pipe regulating valve 28 and a connecting pipe cut-off valve 27 are installed on the connecting pipe to realize the flow regulation between the two pipelines. And a pressure gauge 26 is configured at the inlet of the connecting pipe. After the dry quenching tail gas passes through the inlet pipeline, it is introduced into the purification reactor 10 from the dry quenching tail gas suction 17 by the tail gas induced draft fan 15 through the pipeline.

[0041] Among them, in Step 3 for desulfurization treatment of the tail gas, 20μm sodium bicarbonate powder is under the action of the pneumatic conveying fan 8, and through the conveying pipeline 18, before passing through the Venturi atomization, it is heated by a heat tracing belt at 170°C, so that the temperature of the NaHCO 3 powder is 150°C, which can greatly make up for the insufficient flue gas temperature. The 20μm sodium bicarbonate powder is mixed with the dry quenching tail gas and enters the sodium bicarbonate powder classifier. Under high-temperature conditions, the sodium bicarbonate powder is activated and reacts with the SO2 component in the high-temperature coke oven tail gas in the purification reactor. There is no physical structure in the tail gas reactor, mainly to realize the spray mixing reaction of the high-temperature tail gas and the sodium bicarbonate powder. The reaction time is directly determined by the flow rate of the tail gas induced draft fan for the tail gas.

[0042] Among them, Step 4: Dust removal and desulfurization treatment are as follows: Under the action of the tail gas induced draft fan, the dry quenching tail gas and 20μm sodium bicarbonate powder are mixed in the purification reactor 10. Under high-temperature conditions, the sodium bicarbonate powder is activated and reacts with the SO 2 component in the high-temperature coke oven tail gas to form Na 2 SO 4 dust. Under the action of the tail gas induced draft fan 15, the reactants and other components in the dry quenching tail gas are adsorbed and purified by the bag filter 20. The particulate matter in the reactants and the tail gas is separated by dust removal, realizing the purification and discharge of the tail gas. After all reactions are completed, Na 2 SO 4 , dry quenching flue gas particulate matter, etc. are dust-removed and settled by the dust collector, and finally discharged and collected through the dust collector ash bin collector to realize recycling, and the reaction efficiency reaches more than 65%.

[0043] Example 2: In order to exert the energy efficiency of purifying the dry quenching tail gas, basically each coke oven corresponds to a set of dry desulfurization equipment and process. For the convenience of centralized control, usually several sets of dry desulfurization equipment are concentrated in one place. This technical solution is described according to the two tail gas purification processes corresponding to two dry quenching coke ovens, and its control process is as follows in the flowFigure 4 。

[0044] Grinding and conveying system

[0045] This system is the operation process of producing sodium bicarbonate powder with a particle size of 20 μm and feeding it into the purification reactor. In the technological process, there are two aspects of core control: 1. In order to realize the addition of sodium bicarbonate from the particle feed inlet to the output of 20-μm ultrafine powder, screening sodium bicarbonate powder smaller than 20 μm is the key to the desulfurization process; 2. The ratio of the reaction amount between sodium bicarbonate powder and flue gas, that is, the calculation of the accurate dosage of sodium bicarbonate powder.

[0046] After industrial raw material sodium bicarbonate is added to the raw material tank from the raw material inlet, it enters the grinding hopper. The lower part of the grinding hopper feeds the grinding bin in a spiral manner. The radar level gauge detects the level of the grinding hopper. Since the radar level gauge performs continuous measurement, it not only detects the level but also calculates the actual grinding amount of the grinding bin. In the traditional grinding amount calculation scheme, the spiral feeding motor of the grinder is frequency-controlled, and the number of turns of the feeding screw is counted. There is an estimated value for the feeding value per turn. Number of turns × weight estimated value = grinding feeding amount. In actual control, once jamming occurs, there will be a large error in the grinding feeding weight.

[0047] After using the radar level gauge, because the detection of the material surface is continuous, according to the mathematical model of the bin and the change amount of the material surface in the hopper, accurate calculation of the grinding and feeding amount is realized.

[0048] The bin adopted is a combination of a cylinder and a cone. The volume of the lower cone: The height of the upper cylindrical bin: H′ 高 , then the volume of the upper bin: As the material is unloaded, according to the formula model, using the radar level gauge to detect the change of the material level, the unloading volume V = V 锥 +V 柱 per unit time can be calculated. Then, according to the density ρ of sodium bicarbonate, the weight G of baking soda conveyed to the grinder can be settled 总量 , and the change amount of the material surface per unit time can also be used to judge the blocking situation of sodium bicarbonate particles in the spiral feeding pipeline.

[0049] The grinder 7 grinds the sodium bicarbonate particles input from the grinding bin to achieve a powder effect of less than 20 μm, and then conveys them through a suction fan. The chambers of the grinder, classifier, and conveying fan are integrated. Under the action of the centrifugal force of the pneumatic conveying fan, the powder ground by the grinder is sucked through the classifier 21. The classifier fan blades have a standard mesh number of 20 μm and a closed interval state, and rotate under the action of the motor of the classifier 21, which not only avoids the deficiency of the fixed sieve mesh being easily adhered, ensures the particle size screening of sodium bicarbonate, but also determines the grinding time of the particulate matter in the grinding chamber. After the particle screening by the classifier, the sodium bicarbonate powder less than 20 μm is fed into the inlet of the purification reactor by the fan.

[0050] How to determine the amount of sodium bicarbonate required for the reaction with dry coke quenching flue gas SO 2 ? The theoretical dosage of sodium bicarbonate can be calculated by analyzing the SO 2 composition ratio in the flue gas. According to the main reaction formula of converting NaHCO 3 to Na 2 SO 4 , theoretical calculations are carried out. However, in practice, due to the influence of reaction efficiency, intensification degree, etc., there are large deviations in the theoretically derived values, and now the manual experience method is usually used for feeding. In this control process, a SO 2 content measuring instrument is installed at the inlet of the dust collector. The SO 2 content detected in this area is actually the SO 2 content value at the inlet of the solid waste separation after the reaction in the purification reactor. Using this data as a reference, based on the chemical reaction formula and the flue gas content to calculate the required theoretical value, and through manual experiments in proportion. After collecting multiple groups of data, a sodium bicarbonate feeding model with reference value is formed.

[0051] The classification and screening of the sodium bicarbonate powder by the classifier 21 form a balance between production and transportation by the conveying fan. In actual production, the production particle size of the powder is related to the classification rotation speed of the classifier. After long-term tracking and analysis, during normal feeding, the frequency conversion speed regulation of the classifier increases and decreases according to a slope curve of 17° between the given sodium bicarbonate dosage and the rotation speed. When reaching 70% to 85% of the classifier capacity, the classifier reduces the rotation speed from the peak rotation speed of 70% according to a slope of 25°, and finally maintains a constant rotation speed of 35% given. This mainly realizes that when the feeding amount is large, the sodium bicarbonate particles have sufficient grinding time in the grinding chamber to ensure that more than 90% of the fineness is <20 μm.

[0052] The spiral feeding motor and classification motor of the grinder both adopt frequency conversion control. In practical applications, the rotation speed of the spiral feeder determines the amount of granular sodium bicarbonate added per unit time, while the rotation speed of the classifier actually determines the grinding time of the sodium bicarbonate particles in the grinding chamber.

[0053] Flue gas control process

[0054] The reaction temperature between the dry quenching coke tail gas and sodium bicarbonate powder is the core of the desulfurization reaction efficiency. Therefore, ensuring the flue gas reaction temperature is the key point of the control process.

[0055] In traditional designs, the introduction of dry quenching coke flue gas is after the feed water preheater. According to the dry quenching coke process, the flue gas first preheats the steam water for power generation. After passing through the feed water preheater, the flue gas temperature drops from 200°C to 130°C, and then is directly introduced into the cooling section of the dry quenching furnace to realize the circulation of the flue gas. Therefore, the temperature of the flue gas introduced from this section is only 130°C. After passing through the pipeline to the purification reactor, the pipeline heat dissipation will further reduce the temperature, and the actual low temperature greatly affects the reaction efficiency. Many manufacturers use the method of secondary reheating for the flue gas, which wastes energy.

[0056] To ensure the reaction temperature, in this control scheme, the dry quenching coke tail gas is led out from the flue 17 in front of the existing secondary economizer and behind the circulation fan, which is different from the traditional scheme of introducing it behind the feed water preheater: it is introduced at the front end of the feed water preheater. After the flue gas passes through primary dust removal, superheat heat exchange, and secondary cyclone dust removal, it is taken out at the outlet of the fan, that is, at the front end of the feed water preheater. This extraction process has two advantages. Usually, the foundation at the fan outlet is generally not high, and the pipeline is in a straight-through area, which is convenient for maintenance and repair; secondly, the flue gas has not undergone heat exchange in the feed water preheater, and the flue gas temperature is relatively high, basically remaining at 170°C.

[0057] Taking two coke ovens as an example, usually for two coke ovens, due to different smelting processes and control processes, the tail gas temperatures of each coke oven are also different. To ensure the maximum utilization value of the tail gas temperature, the method of flue gas mixing is used to ensure that the flue gas of both coke ovens is at a temperature of 140°C at the inlet of the purification reactor.

[0058] For each coke oven, from the flue gas inlet, a cut-off valve, a regulating valve, and a flow meter are configured. A temperature detection element is added in front of the purification reactor. A connecting pipe is added between the tail gas introduction pipelines of the two coke ovens, and a regulating valve is installed to realize the flow regulation between the two pipelines. And a pressure feedback device is configured at the inlet of the connecting pipe. After passing through the purification reactor, there is a system tail gas induced draft fan. With such a configuration, a closed-loop control of the introduced air volume and the mixing air temperature can be established.

[0059] Such a system configuration realizes three functions: 1. When the coke oven or the desulfurization equipment needs to be repaired, using the cut-off valve ( Figure 2When the main valve (12) in the bypass pipe and the cut-off valve in the connecting pipe are closed, the system can achieve physical isolation safely and effectively. 2. Adjust the amount of flue gas introduced. When it is necessary to change the amount of flue gas introduced, it can be achieved by the variable frequency speed regulation of the tail gas induced draft fan of the system in cooperation with the regulating valve. During production, the coke oven PLC calculates the amount of flue gas that needs to be discharged from the coke oven, and the data is sent to the PLC of the tail gas purification system. For any coke oven, in actual application, by adjusting the regulating valve or the speed of the flue gas tail gas induced draft fan and using the detection of the flow rate, ensure the purification amount that needs to be discharged from the dry quenching coke tail gas; 3. The system is provided with a connecting pipe and a regulating valve, and the variable frequency speed regulation of the tail gas induced draft fans of the two tail gas purifications is also used. The main purpose is to realize the mixing of the flue gases of the two coke ovens. Using the temperature as the feedback quantity, the tail gas temperature of the low-temperature coke oven is increased, so as to achieve a better activation effect. The high- and low-temperature flue gases of the two coke ovens are mixed. Its control principle is: First, establish a pressure closed-loop for the two fans. According to the actual experience value, set the pressure values of the tail gas induced draft fans of the high-temperature tail gas and the low-temperature tail gas. The pressure of the low-temperature tail gas is higher than that of the high-temperature tail gas by ΔP. The pressure is detected by the pressure sensors on both sides of the bypass pipe. Through the connection of the connecting pipe, the high-temperature tail gas flows to the low-temperature tail gas, forming the mixing of the tail gas; What is the mixing amount of the high- and low-temperature tail gases? Set the temperature in front of the flue gas reactor of the low-temperature coke oven as the feedback value. Through the opening of the regulating valve on the connecting pipe, the high-temperature flue gas is introduced into the low-temperature pipeline, realizing the increase of the low-temperature flue gas temperature, forming a temperature closed-loop; For each coke oven, the introduced amount of the dry quenching coke tail gas is the required value. Under the condition that the fan pressure is set in advance, the theoretical value of the flue gas and the feedback quantity are compared, and the closed-loop of the flue gas introduced amount is realized through the opening of the regulating valve of the flue gas introduction pipe of each coke oven; In the entire flue gas system, the pipelines are all connected. Therefore, any adjustment of data will cause the oscillation of the system. Therefore, the overshoot of each closed-loop is amplified according to the experience value to reduce the system oscillation. Finally, the flue gases of the two systems are mixed, and the reaction temperature of the dry quenching coke tail gas is increased.

[0060] Tail gas desulfurization reaction

[0061] Under the action of the pneumatic conveying fan, 20μm sodium bicarbonate powder is heated to 170℃ by the heating tape through the conveying pipeline before passing through the Venturi atomization, so that the temperature of the NaHCO 3 powder is 150℃, which can greatly make up for the insufficient flue gas temperature. The 20μm sodium bicarbonate powder is mixed with the dry quenching coke tail gas and enters the purification reactor. Under high-temperature conditions, the sodium bicarbonate powder is activated and reacts with the SO2 component in the high-temperature tail gas of the coke oven in the purification reactor. There is no physical structure in the tail gas reactor, mainly realizing the spray mixing reaction of the high-temperature tail gas and the sodium bicarbonate powder. The reaction time is directly determined by the flow rate of the tail gas induced draft fan for the tail gas.

[0062] Dust removal and desulfurization control

[0063] Under the action of the tail gas induced draft fan, the dry quenching coke tail gas and sodium bicarbonate powder with a particle size of 20 μm are mixed in the purification reactor ( Figure 1 No. 10). Under high-temperature conditions, the sodium bicarbonate powder is activated and reacts with the SO 2 components in the high-temperature coke oven tail gas in the reactor to form Na 2 SO 4 dust. Under the action of the tail gas induced draft fan ( Figure 1 No. 15), the reactants and other components in the dry quenching coke tail gas pass through the bag filter ( Figure 1 No. 20) for adsorption and purification. The particulate matter in the reactants and tail gas is separated by dust settling, realizing the purification and emission of the tail gas.

[0064] Conventional bag dust removal adopts the bag differential pressure control mode, that is, when the bag accumulates dust to a certain extent and the differential pressure inside and outside the bag reaches the set value, the pulse purge valve is controlled to act, and the filter bag surface dust is removed to the bottom ash hopper by using high-speed air flow. In actual production, due to the low temperature of the dry quenching coke flue gas desulfurization reaction, the reaction efficiency is relatively low, and the efficiency of the reaction of SO 2 to form Na 2 SO 4 is about 35%. The low reaction efficiency causes mixtures such as SO 2 , NaHCO 3 , Na 2 SO4, and flue gas dust to adhere to the bag surface, resulting in relatively serious bag adhesion during the long process of establishing differential pressure.

[0065] This control scheme adopts time control, allowing mixtures such as SO 2 , Na 2 CO 3 , and Na 2 SO4 to adhere to and react on the dust removal bag for a period of time. The effect can be determined by groping with the SO 2 content tester at the inlet and outlet of the dust collector. In actual operation, due to different ash discharge times of the dust removal system, the measured values of the SO 2 content tester in the flue gas discharged from the chimney show an obvious change trend. Therefore, through the operation and groping of the ash discharge time on the bag, the desulfurization effect of further re-reaction of the mixture in the dust collector can be achieved, ensuring that the measured value of the SO 2 content tester in the flue gas discharged from the chimney meets the national ultra-clean emission standard.

[0066] After all reactions are completed, Na 2 SO 4 , dry quenching coke flue gas particulate matter, etc. pass through the dust removal and sedimentation of the dust collector, and finally are discharged and collected through the dust collector ash bin collector for recycling, with a reaction efficiency of over 65%.

[0067] Working principle: Refer to Figure 1 — Figure 4 , and its control principle is:

[0068] 1. Dry desulfurization: The main pollutants in the coke dry quenching tail gas are SO 2 , and dust. The purification scheme uses sodium bicarbonate to react with the sulfur-containing components in the tail gas:

[0069] Main reaction: 2NaHCO 3 =Na 2 CO 3 +H 2 O + CO 2 (1)

[0070] 2SO 2 +2Na 2 CO 3 +O 2 (in an oxygen environment of 3.5%) = 2Na 2 SO 4 +2CO 2 (2)

[0071] 2. Particulate matter dust removal: After desulfurization, a bag filter is used to remove dust and recover the desulfurization reactants. The purified flue gas enters the chimney to achieve up-to-standard discharge.

[0072] 3. 3.3 The ultrafine sodium bicarbonate powder and the high-temperature flue gas interact in the purification reactor ( Figure 1 in 10) to decompose into highly active sodium carbonate and carbon dioxide. The highly active Na 2 CO 3 fully contacts with the SO 2 in the coke dry quenching tail gas in the flue duct and undergoes a chemical reaction.

[0073] 4. 3.4 When the SO 2 in the coke dry quenching flue gas and the NaHCO 3 powder fully react to form the Na 2 SO 4 powder, it is sent as a whole by the system tail gas induced draft fan into the bag filter ( Figure 1 in 20) for adsorption and sedimentation. The mixture and gas can be evenly distributed around the filter bag before entering the filter bag. The mixture powder will be blocked on the outer surface of the filter bag. The purified flue gas rises from the inside of the filter bag into the clean gas chamber and is discharged from the chimney through the clean gas chamber ( Figure 1 in 13), while the solid mixture is adsorbed and vibrated on the surface of the filter bag and finally collected through the ash bin collector ( Figure 1 in 14) to realize the recycling of the Na 2 SO 4 powder and achieve the purification and discharge of the coke dry quenching flue gas.

[0074] It should be noted that the above embodiments are not intended to limit the protection scope of the present invention, and equivalent transformations or substitutions made on the basis of the above technical solutions all fall within the protection scope of the claims of the present invention.

Claims

1. A control method for the purification of coke dry quenching tail gas, characterized in that, the method comprises the following steps: Step 1: Conduct grinding and conveying in the grinding and conveying system, Step 2: Control the flue gas, Step 3: Conduct desulfurization treatment on the tail gas, Step 4: Conduct dust removal and then desulfurization treatment.

2. The control method for the purification of coke dry quenching tail gas according to claim 1, characterized in that, the grinding and conveying system in Step 1 includes a sodium bicarbonate particle inlet, a storage tank, a radar level gauge, a hopper, a screw conveyor, a grinding motor, a grinder, a pneumatic conveying fan, a sodium bicarbonate powder heating device, and a sodium bicarbonate powder classifier. The sodium bicarbonate particle inlet is arranged above the storage tank. Below the storage tank, there are successively arranged a hopper, a screw conveyor, and a grinder. The grinding motor is arranged on one side of the grinder to drive the grinder to work. Above the grinder, there is a pneumatic conveying fan. The pneumatic conveying fan is connected to the purification reactor through a pipeline. A sodium bicarbonate powder heating device is arranged between the pneumatic conveying fan and the purification reactor. The chambers of the grinder, the pneumatic conveying fan, and the sodium bicarbonate powder classifier are connected as a whole.

3. The control method for the purification of coke dry quenching tail gas according to claim 2, characterized in that, the specific process of Step 1 is as follows: Sodium bicarbonate is added through the sodium bicarbonate particle inlet. After passing through the storage tank 2, it enters the hopper. The radar level gauge is used to detect the change in its level. After being conveyed by the screw conveyor into the grinder for grinding, and then screened by the sodium bicarbonate powder classifier, it is sprayed into the purification reactor as ultrafine sodium bicarbonate powder through the pneumatic conveying fan and the pipeline. In order to ensure the reaction efficiency, a sodium bicarbonate powder heating device is arranged at the front end of the purification reactor to heat the ultrafine sodium bicarbonate powder to 170 °C.

4. The control method for the purification of coke dry quenching tail gas according to claim 3, characterized in that, the flue gas control system in Step 2 includes Purification reactor, SO content meter at the inlet of the dust collector 2 Content detector, SO content detector at the chimney outlet of the dust collector 2 Exhaust gas discharged from the chimney of the dust collector, dust collector ash bin collector, tail gas induced draft fan, CDQ tail gas input, CDQ tail gas suction, gas output after desulfurization reaction, dry dust collector, CDQ tail gas inlet pipeline cut-off valve, pipeline regulating valve, flow meter, first thermometer, pressure gauge, connecting pipe cut-off valve, connecting pipe regulating valve, second thermometer and connecting pipe There is an input of coke dry quenching tail gas between the purification reactor and the tail gas induced draft fan. The coke dry quenching tail gas is inhaled and connected to the tail gas induced draft fan. There is an output of the gas after desulfurization reaction between the purification reactor and the dry dust collector. From the flue gas inlet, a cut-off valve, a pipeline regulating valve, and a flow meter for the coke dry quenching tail gas introduction pipeline are configured. A temperature detection element is added in front of the purification reactor. A connecting pipe is added between the tail gas introduction pipelines of two coke ovens, and a connecting pipe regulating valve is installed, which can realize the flow regulation between the two pipelines. And a pressure gauge is configured at the inlet of the connecting pipe. After passing through the purification reactor, there is a system tail gas induced draft fan. With such a configuration, a closed-loop control of the introduced air volume and the mixed air temperature can be established.

5. The control method for the purification of coke dry quenching tail gas according to claim 3 or 4, characterized in that, Step 2: Control the flue gas as follows: Usually, more than two coke ovens are used for simultaneous production, mainly to ensure that the coke oven gas generated by the dry distillation of the coke oven does not stop during use in other processes. For each coke oven, the dry quenching tail gas is led out from the flue gas inlet. On the conveying pipeline, a dry quenching tail gas inlet pipeline cut-off valve, a pipeline regulating valve, a flow meter, and a first thermometer are configured; A connecting pipe is added between the tail gas inlet pipelines of the two coke ovens, and a connecting pipe regulating valve and a connecting pipe cut-off valve are installed on the connecting pipe to achieve flow regulation between the two pipelines, and a pressure gauge is configured at the inlet of the connecting pipe. After the dry quenching tail gas passes through the inlet pipeline, it is sucked into the purification reactor by the tail gas induced draft fan through the pipeline.

6. The control method for the purification of dry quenching tail gas according to claim 5, characterized in that In step 3 of desulfurizing the tail gas, 20-μm sodium bicarbonate powder is heated to 170 °C by a heating tape through a conveying pipeline before Venturi atomization under the action of a pneumatic conveying fan, so that the temperature of the NaHCO 3 powder is 150 °C, which can greatly make up for the insufficient flue gas temperature. The 20-μm sodium bicarbonate powder is mixed with the coke dry quenching tail gas and enters a sodium bicarbonate powder classifier. Under high-temperature conditions, the sodium bicarbonate powder is activated and reacts with the SO2 component in the high-temperature coke oven tail gas in a purification reactor. There is no physical structure in the tail gas reactor, mainly realizing the spray-like mixing reaction of high-temperature tail gas and sodium bicarbonate powder. The reaction time is directly determined by the flow rate of the tail gas induced by the tail gas induced draft fan.

7. The control method for the purification of dry quenching tail gas according to claim 6, characterized in that Step 4: Dust removal and desulfurization treatment, specifically as follows: Under the action of the tail gas induced draft fan, the dry coke quenching tail gas and sodium bicarbonate powder with a particle size of 20 μm are mixed in the purification reactor 10. Under high-temperature conditions, the sodium bicarbonate powder is activated and reacts with the SO 2 components in the high-temperature coke oven tail gas to form Na 2 SO 4 dust. Under the action of the tail gas induced draft fan 15, the reactants and other components in the dry coke quenching tail gas are adsorbed and purified by the bag filter. The particulate matter in the reactants and the tail gas is separated by dust removal, and the purification and emission of the tail gas are realized. After all the reactions are completed, Na 2 SO 4 , particulate matter in the dry coke quenching flue gas, etc. are dust-removed and settled by the dust collector, and finally discharged and collected through the dust collector ash bin collector to realize recycling, and the reaction efficiency reaches more than 65%.

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