Flue gas purification process for preparing anode carbon block

Abstract

The invention belongs to the technical field of flue gas purification, and particularly relates to a flue gas purification process for preparing an anode carbon block, which comprises the following steps: step 1, high-temperature flue gas with the volume percentage of 15-35% is extracted from a main flue of a roasting furnace as circulating flue gas, and the temperature range of the high-temperature flue gas is 800-1000 DEG C; 2, the circulating flue gas is introduced into a cyclone dust collector to be pretreated, and particulate matter with the particle size larger than 10 micrometers is removed; thirdly, the pretreated circulating flue gas is conveyed to a combustion-supporting air pipeline through a high-temperature-resistant and corrosion-resistant induced draft fan; compared with a traditional process, the flue gas purification efficiency is improved by 25%-35%, the emission concentration of organic pollutants (such as asphalt fume) is lower than 3 mg / m, the emission concentration of particulate matter is lower than 5 mg / m, and the emission concentration of SOs is lower than 35 mg / m. By means of the effect, emission of atmospheric pollutants in the anode carbon block production process is remarkably reduced, the national environmental protection standard is met or even superior, and enterprises are assisted to achieve green production and sustainable development.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas purification, and in particular to a flue gas purification process for preparing anode carbon blocks. Background Art

[0002] The roasting furnace is a core piece of equipment in the anode carbon block production process. Its operation generates large amounts of high-temperature flue gas (typically 800-1000°C). This flue gas contains high concentrations of organic pollutants (such as asphalt fumes and benzopyrene), particulate matter (such as tar dust), and acidic gases (such as SO2 and HF). If discharged without effective treatment, these gases pose serious risks to the atmospheric environment and human health. Traditional flue gas purification processes (such as single wet desulfurization or electrostatic precipitation) have low removal efficiency for organic pollutants. Emission concentrations of refractory substances such as asphalt fumes and benzopyrene often exceed national environmental standards (for example, the asphalt fume emission limit is typically ≤5 mg / m³, but can still reach 10-20 mg / m³ after treatment), posing environmental compliance risks to companies. Traditional processes fail to effectively recycle waste heat from the flue gas, requiring the roasting furnace's combustion air to be heated using additional heating equipment, increasing fuel consumption by 15-25%. In addition, equipment maintenance cycles are short (e.g., electrostatic precipitators and desulfurization towers require frequent shutdowns for cleaning), and operating and maintenance costs remain high, restricting the company's economic benefits. Traditional processes lack real-time monitoring and dynamic regulation of key parameters such as temperature and oxygen content in the roasting furnace flue, resulting in large fluctuations in the thermal cracking efficiency of organic pollutants (usually only 80%-85%), which is prone to incomplete combustion or local overheating, thereby affecting the product quality of anode carbon blocks and increasing the risk of equipment corrosion and wear. In traditional processes, pretreatment equipment such as cyclone dust collectors have limited removal effects on fine particulate matter (such as asphalt smoke particles with a particle size of <10μm), resulting in overloading of subsequent purification equipment (such as desulfurization towers) and prone to secondary pollution (such as improper treatment of desulfurization wastewater and waste residue). Summary of the Invention

[0003] In order to solve the above problems, the present invention proposes a flue gas purification process for preparing anode carbon blocks, so as to more accurately solve the problems raised in the above background technology.

[0004] The present invention is achieved through the following technical solutions: The present invention provides a flue gas purification process for the preparation of anode carbon blocks, comprising the following steps: Step 1, extracting 15%-35% by volume of high-temperature flue gas from the main flue of the roasting furnace as recycled flue gas, the temperature range of the high-temperature flue gas being 800°C - 1000°C; Step 2, introducing the recycled flue gas into a cyclone dust collector for pretreatment to remove particulate matter with a particle size greater than 10μm; Step 3, using a high-temperature and corrosion-resistant induced draft fan to transport the pretreated recycled flue gas to the combustion air pipeline, mixing it with the combustion air and then introducing it into the roasting furnace flue; Step 4, in the roasting furnace flue, using a high-temperature environment of 1200°C - 1400°C to cause thermal cracking of the organic pollutants in the recycled flue gas; Step 5, the remaining flue gas is cooled by a spray cooling tower, tar and dust are captured by an electrostatic tar precipitator, and acidic gases are removed by a desulfurization tower before being discharged up to the standard.

[0005] Preferably, the inner wall of the cyclone dust collector is coated with a high-temperature and corrosion-resistant coating, and the inside is filled with an adsorption material with a particle size of 150 - 250 mesh. The adsorption material is calcined coke powder, its specific surface area is not less than 200 m² / g, and the dosage is 150 - 250 mg per cubic meter of flue gas, which is used to pre-adsorb the pitch fume and benzo[a]pyrene in the flue gas.

[0006] Preferably, the connection between the recycled flue gas extraction pipeline and the main flue is provided with a high-temperature metal expansion joint. An on-line oxygen content analyzer and a temperature sensor are arranged on the extraction pipeline, and the recycled flue gas flow rate is adjusted through a PID control system to ensure that the oxygen content by volume of the combustion air after mixing is not less than 18%.

[0007] Preferably, before the recycled flue gas is introduced into the combustion air pipeline, 3%-8% of pure oxygen by its volume is supplemented through an oxygen supplementation device. The oxygen supplementation device is a membrane separation oxygen production equipment, the oxygen purity is not less than 95%, and the oxygen supplementation amount is dynamically adjusted according to the feedback signal of the on-line oxygen content analyzer.

[0008] Preferably, multiple groups of temperature sensors and pressure sensors are arranged in the roasting furnace flue to monitor the temperature field and air flow distribution in the flue in real time. The flue temperature is controlled within the range of 1250°C - 1350°C by adjusting the fuel supply amount to ensure that the thermal cracking efficiency of the organic pollutants is not less than 95%.

[0009] Preferably, the spray cooling tower is a countercurrent spray empty tower. Three layers of atomizing spray devices are arranged in the tower. The spray liquid is recycled cooling water, and the spray density is 10 - 15 m³ / (m²·h). The temperature of the flue gas is reduced to 80°C - 90°C after spraying. A scraper conveyor is arranged at the bottom of the tower to discharge the condensed tar and dust.

[0010] Preferably, the electrostatic tar precipitator adopts a honeycomb structure, the plate spacing is 200 - 300 mm, the corona wire is a spike wire, the operating voltage is 40 - 60 kV, the flue gas flow rate is 0.8 - 1.2 m / s, the tar capture efficiency is not less than 98%, and the tar deposited on the plate surface automatically falls off to the oil sump through steam heating.

[0011] Preferably, the desulfurization tower is a packed tower, the packing is regular ceramic corrugated plates, the spraying liquid is a sodium hydroxide solution with a mass concentration of 5% - 10%, the liquid-gas ratio is 3 - 5 L / m³, the flue gas and the spraying liquid are in countercurrent contact, the desulfurization efficiency is not less than 90%, and the SO2 concentration in the flue gas at the outlet of the desulfurization tower is lower than 35 mg / m³.

[0012] Preferably, the process further includes a flue gas waste heat recovery step. By setting a heat exchanger on the circulating flue gas pipeline, the waste heat of the flue gas is used to preheat the combustion-supporting air, raising the temperature of the combustion-supporting air to 150°C - 200°C, while reducing the fuel consumption by 10% - 20%.

[0013] Preferably, the flue gas purification efficiency of the process is increased by 25% - 35% compared with the traditional process, the emission concentration of organic pollutants (calculated as asphalt fume) is lower than 3 mg / m³, the emission concentration of particulate matter is lower than 5 mg / m³, and the energy consumption of the system operation is reduced by 15% - 25%.

[0014] Compared with the prior art, the present invention provides a flue gas purification process for anode carbon block preparation, which has the following beneficial effects: This flue gas purification process for anode carbon block preparation increases the flue gas purification efficiency by 25% - 35% compared with the traditional process, with the emission concentration of organic pollutants (such as asphalt fume) lower than 3 mg / m³, the emission concentration of particulate matter lower than 5 mg / m³, and the SO2 emission concentration lower than 35 mg / m³. This effect significantly reduces the atmospheric pollutant emissions during the production of anode carbon blocks, meeting or even exceeding the national environmental protection standards, and helping enterprises achieve green production and sustainable development.

[0015] This flue gas purification process for anode carbon block preparation, through the flue gas waste heat recovery step, raises the temperature of the combustion-supporting air to 150°C - 200°C, reduces the fuel consumption by 10% - 20%, and at the same time reduces the overall energy consumption of the system by 15% - 25%. In addition, the adsorption effect of calcined coke powder in the cyclone dust collector reduces the load of subsequent purification equipment and extends the equipment maintenance cycle.

[0016] This flue gas purification process for anode carbon block preparation, through real-time monitoring and intelligent control system, realizes the precise regulation of the temperature and oxygen content in the roasting furnace flue, ensuring the efficient thermal cracking of organic pollutants. At the same time, the optimized design of equipment such as high-temperature-resistant metal expansion joints and high-temperature-resistant anti-corrosion coatings effectively reduces the corrosion and wear of high-temperature flue gas on the equipment and extends the service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 FIG. 1 is a schematic flow chart of a flue gas purification process for the preparation of anode carbon blocks proposed by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] In order to more clearly and completely illustrate the technical solution of the present invention, the present invention will be further described below with reference to the accompanying drawings. Embodiment

[0019] As Figure 1 shown, during the operation of the anode carbon block roasting furnace, 25% of the high-temperature flue gas by volume is extracted from the main flue as circulating flue gas, and the temperature of the flue gas is 900 °C. After the circulating flue gas is pretreated by a cyclone dust collector, it is transported to the combustion-supporting air pipeline through a high-temperature-resistant induced draft fan, mixed with the combustion-supporting air and then introduced into the roasting furnace flue. The temperature in the flue is 1300 °C, and organic pollutants such as pitch fume and benzo[a]pyrene in the circulating flue gas undergo thermal cracking or oxidation reactions at high temperatures. The remaining flue gas is sequentially treated by a spray cooling tower (the temperature is reduced to 85 °C), an electric tar precipitator (the tar capture efficiency is 98.5%), and a desulfurization tower (the SO2 concentration is reduced to 30 mg / m³) and then discharged up to the standard. The flue gas purification efficiency is increased by 30% compared with the traditional process. The emission concentration of organic pollutants is 2.5 mg / m³, and the emission concentration of particulate matter is 4.2 mg / m³.

[0020] In the present invention, the inner wall of the cyclone dust collector is coated with a high-temperature-resistant ceramic coating, and calcined coke powder with a particle size of 200 mesh (specific surface area 220 m² / g) is filled inside, and the dosage is 200 mg per cubic meter of flue gas. After the circulating flue gas is pretreated, the adsorption rates of pitch fume and benzo[a]pyrene reach 85% and 78% respectively. The concentration of pitch fume in the flue gas at the outlet of the cyclone dust collector is reduced from 120 mg / m³ to 18 mg / m³, and the concentration of benzo[a]pyrene is reduced from 5 mg / m³ to 1.1 mg / m³.

[0021] In the present invention, a high-temperature-resistant metal expansion joint is used at the connection between the circulating flue gas extraction pipeline and the main flue, and an on-line oxygen content analyzer and a temperature sensor are arranged on the extraction pipeline. The flow rate of the circulating flue gas is adjusted through a PID control system to make the oxygen content of the combustion-supporting air after mixing stable at 19% (volume fraction), the combustion efficiency in the roasting furnace flue is increased by 12%, and the fuel consumption is reduced by 8%.

[0022] In the present invention, before the circulating flue gas is introduced into the combustion-supporting air pipeline, 5% of pure oxygen (oxygen purity 96%) of its volume is supplemented through a membrane separation oxygen production device. The oxygen supplement amount is dynamically adjusted according to the feedback signal of the on-line oxygen content analyzer to ensure the stability of the oxygen content after mixing. The temperature fluctuation range in the roasting furnace flue is reduced from ±50 °C to ±20 °C, and the thermal cracking efficiency of organic pollutants is increased to 96%.

[0023] In the present invention, multiple groups of temperature sensors and pressure sensors are arranged in the flue of the roasting furnace to monitor the temperature field and air flow distribution in real time. By adjusting the fuel supply, the flue temperature is controlled within the range of 1280°C - 1320°C. The thermal cracking efficiency of organic pollutants is 97%. The concentration of pitch fume in the flue gas is reduced from 15 mg / m³ to 0.45 mg / m³, and the concentration of benzo[a]pyrene is reduced from 0.8 mg / m³ to 0.02 mg / m³.

[0024] In the present invention, the spray cooling tower is a countercurrent spray empty tower. Three layers of atomizing spray devices are arranged in the tower. The spray liquid is circulating cooling water, and the spray density is 12 m³ / (m²·h). After the flue gas is sprayed, the temperature drops to 82°C. The scraper conveyor at the bottom of the tower discharges condensed tar and dust. The temperature of the flue gas at the outlet of the spray cooling tower drops from 900°C to 82°C, the tar capture rate reaches 92%, and the dust emission concentration is 6.5 mg / m³.

[0025] In the present invention, the electric tar precipitator adopts a honeycomb structure, the plate spacing is 250 mm, the corona wire is a spike wire, the working voltage is 50 kV, and the flue gas flow rate is 1.0 m / s. The tar deposited on the plate surface automatically falls off to the oil sump through steam heating. The tar capture efficiency is 98.8%, and the tar concentration in the flue gas at the outlet of the electric tar precipitator is 0.15 mg / m³.

[0026] In the present invention, the desulfurization tower is a packed tower, the packing is regular ceramic corrugated plate, the spray liquid is sodium hydroxide solution with a mass concentration of 8%, and the liquid-gas ratio is 4 L / m³. The flue gas contacts the spray liquid countercurrently, the desulfurization efficiency is 92%, the SO2 concentration in the flue gas at the outlet of the desulfurization tower is 28 mg / m³, and the HF concentration is 1.2 mg / m³.

[0027] In the present invention, a heat exchanger is arranged on the circulating flue gas pipeline to use the waste heat of the flue gas to preheat the combustion-supporting air, so that the temperature of the combustion-supporting air is raised from room temperature to 180°C. The fuel consumption is reduced by 15%, the system thermal efficiency is increased by 18%, and the unit product energy consumption is reduced by 12%.

[0028] In the present invention, the flue gas purification efficiency is increased by 32% compared with the traditional process. The emission concentration of organic pollutants (calculated as pitch fume) is 2.2 mg / m³, the particulate matter emission concentration is 3.8 mg / m³, the system operation energy consumption is reduced by 18%, the process operation stability is improved, the equipment maintenance cycle is extended by 30%, and the production cost is reduced by 15%.

[0029] Finally, it should be noted that: The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only an example and does not constitute a limitation to this specification. Although not explicitly stated here, those skilled in the art may make various modifications, improvements, and corrections to this specification. Such modifications, improvements, and corrections are suggested in this specification, so such modifications, improvements, and corrections still fall within the spirit and scope of the exemplary embodiments of this specification. At the same time, this specification uses specific terms to describe the embodiments of this specification. Such as "one embodiment", "an embodiment", and / or "some embodiments" mean a certain feature, structure, or characteristic related to at least one embodiment of this specification. Therefore, it should be emphasized and noted that the "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more at different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this specification can be appropriately combined. In addition, unless clearly stated in the claims, the order of the processing elements and sequences described in this specification, the use of numerical letters, or the use of other names are not used to limit the order of the processes and methods in this specification.

[0030] Finally, it should be noted that: The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A flue gas purification process for the preparation of anode carbon blocks, characterized in that, It includes the following steps: Step 1: Extract high-temperature flue gas with a volume percentage of 15%-35% from the main flue of the roasting furnace as recycled flue gas, and the temperature range of the high-temperature flue gas is 800°C - 1000°C; Step 2: Introduce the recycled flue gas into a cyclone dust collector for pretreatment to remove particulate matter with a particle size greater than 10μm; Step 3: Use a high-temperature and corrosion-resistant induced draft fan to transport the pretreated recycled flue gas to the combustion air pipeline, mix it with combustion air, and then introduce it into the roasting furnace flue; Step 4: In the roasting furnace flue, use a high-temperature environment of 1200°C - 1400°C to cause thermal cracking of organic pollutants in the recycled flue gas; Step 5: The remaining flue gas is cooled by a spray cooling tower, tar and dust are collected by an electrostatic tar precipitator, and acidic gases are removed by a desulfurization tower before being discharged up to standard.

2. The flue gas purification process for preparing anode carbon blocks according to claim 1, characterized in that, The inner wall of the cyclone dust collector is coated with a high-temperature and corrosion-resistant coating, and the inside is filled with an adsorption material with a particle size of 150 - 250 mesh. The adsorption material is calcined coke powder, its specific surface area is not less than 200m² / g, and the dosage is 150 - 250mg per cubic meter of flue gas, which is used to pre-adsorb pitch fume and benzo[a]pyrene in the flue gas.

3. The flue gas purification process for preparing anode carbon blocks according to claim 1, characterized in that, The connection between the recycled flue gas extraction pipeline and the main flue uses a high-temperature metal expansion joint. An on-line oxygen content analyzer and a temperature sensor are set on the extraction pipeline. The flow rate of the recycled flue gas is adjusted through a PID control system to ensure that the oxygen content by volume of the combustion air after mixing is not less than 18%.

4. A flue gas purification process for the preparation of anode carbon blocks according to claim 1, characterized in that, Before the recycled flue gas is introduced into the combustion air pipeline, pure oxygen with a volume of 3% - 8% of its volume is supplemented through an oxygen supplementation device. The oxygen supplementation device is a membrane separation oxygen production equipment, the oxygen purity is not less than 95%, and the oxygen supplementation amount is dynamically adjusted according to the feedback signal of the on-line oxygen content analyzer.

5. A flue gas purification process for the preparation of anode carbon blocks according to claim 1, characterized in that, Multiple groups of temperature sensors and pressure sensors are set in the roasting furnace flue to monitor the temperature field and gas flow distribution in the flue in real time. The temperature of the flue is controlled within the range of 1250°C - 1350°C by adjusting the fuel supply amount to ensure that the thermal cracking efficiency of organic pollutants is not less than 95%.

6. A flue gas purification process for preparing anode carbon blocks according to claim 1, characterized in that, The spray cooling tower is a countercurrent spray empty tower. Three layers of atomizing spray devices are set in the tower. The spray liquid is circulating cooling water, and the spray density is 10 - 15m³ / (m²·h). The temperature of the flue gas is reduced to 80°C - 90°C after spraying. A scraper conveyor is set at the bottom of the tower to discharge the condensed tar and dust.

7. A flue gas purification process for the preparation of anode carbon blocks according to claim 1, characterized in that, The electrostatic tar precipitator adopts a honeycomb structure, the plate spacing is 200 - 300mm, the corona wire is a spike wire, the working voltage is 40 - 60kV, the flue gas flow rate is 0.8 - 1.2m / s, the tar collection efficiency is not less than 98%, and the tar deposited on the plate surface automatically falls off to the oil collection tank through steam heating.

8. A flue gas purification process for preparing anode carbon blocks according to claim 1, characterized in that, The desulfurization tower is a packed tower, the packing is a regular ceramic corrugated plate, the spray liquid is a sodium hydroxide solution with a mass concentration of 5% - 10%, the liquid-gas ratio is 3 - 5L / m³, the flue gas and the spray liquid contact countercurrently, the desulfurization efficiency is not less than 90%, and the SO2 concentration in the flue gas at the outlet of the desulfurization tower is lower than 35mg / m³.

9. A flue gas purification process for the preparation of anode carbon blocks according to claim 1, characterized in that, The process further includes a step of recovering waste heat from flue gas. By installing a heat exchanger on the circulating flue gas pipeline, the waste heat of the flue gas is used to preheat the combustion-supporting air, raising the temperature of the combustion-supporting air to 150°C - 200°C, while reducing the fuel consumption by 10% - 20%.

10. A flue gas purification process for preparing anode carbon blocks according to claim 1, characterized in that, The flue gas purification efficiency of the process is increased by 25% - 35% compared with the traditional process. The emission concentration of organic pollutants (calculated as asphalt fume) is lower than 3 mg / m³, and the emission concentration of particulate matter is lower than 5 mg / m³. Moreover, the energy consumption of the system operation is reduced by 15% - 25%.

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