Coal-based activated carbon and preparation method and preparation device thereof

Abstract

This invention belongs to the field of coal-based activated carbon technology, and discloses a coal-based activated carbon preparation method and apparatus. The preparation method comprises: Step 1, pre-treating coal and then removing ash to obtain ash-removed coal powder; Step 2, uniformly dispersing the ash-removed coal powder, powdered activated carbon, and binder in an aqueous solvent to obtain a mixture; Step 3, microwaving the mixture, and alternately injecting preheated and vaporized acid and alkali solutions during the microwave heating process to obtain a gaseous component and a solid component, the obtained solid component being the coal-based activated carbon. The preparation method of this invention not only produces high-performance powdered activated carbon but also achieves low-energy consumption and short-cycle preparation, and enables the recovery and utilization of tail gas.

Description

Technical Field

[0001] This invention relates to the field of coal-based activated carbon technology, and more particularly to a coal-based activated carbon, its preparation method, and preparation apparatus. Background Technology

[0002] Powdered activated carbon is widely used in chemical, petroleum, metallurgical, and environmental fields, finding extensive applications in water treatment, liquid-phase recovery and separation, gas-phase adsorption, industrial catalysts or catalyst supports, and contaminated soil remediation. General quality requirements for ordinary powdered activated carbon products: specific surface area of ​​700–1200 m² / g. 2 / g, methylene blue adsorption value is 100-150 mg / g, iodine value is 800-1050 mg / g. In my country, coal is the main raw material for powdered activated carbon production, accounting for over 70% of total powdered activated carbon production. Production methods fall into two categories: chemical activation using acids, alkalis, or salts as activating agents, and physical activation using steam or CO2 as activating agents. Raw coal typically requires a moisture content below 5%, ash content below 6%, volatile matter of 7-8%, and high reactivity; therefore, coal-based powdered activated carbon manufacturers generally choose anthracite as raw material.

[0003] Chemical activation methods are divided into two-step and one-step methods. The two-step method involves carbonizing coal in an inert gas atmosphere at a specific temperature, followed by activation treatment of the coal with an activating agent under specific conditions. The one-step method involves heating the coal under an inert gas atmosphere, with carbonization and activation occurring simultaneously. Currently, the main activating agents used include zinc chloride, potassium hydroxide, and sodium hydroxide. The activation mechanism is generally believed to be that the activating agent dehydrates the coal during pyrolysis, inhibits tar production, promotes pyrolysis, and simultaneously undergoes aromatization during carbonization, thus forming a rich porous structure. However, because the activating agents are toxic and easily volatilize at high temperatures, they pose serious threats to the environment and human health. 2+ Residues left in powdered activated carbon affect water quality, and the activator is difficult to recover. Due to the pollution problems caused by chemical activation, its industrial application has been gradually restricted, and this method has been banned in many countries abroad.

[0004] Physical activation, also known as gas activation, involves two stages: carbonization and activation. Carbonization is the process of heating coal to 500–650°C in the absence of air. Carbonization is a low-temperature dry distillation process that also involves the thermal decomposition and condensation of coal, typically lasting 1–2 hours. Activation temperature is usually between 600–1000°C, and activation time is typically 2–4 hours. Generally, oxygen-containing gases such as steam, carbon dioxide, and air, or mixtures of these gases, are used as activators. These gases are brought into contact with the carbonized material under high-temperature conditions, or two activators are used alternately, to produce powdered activated carbon products with a large specific surface area and abundant pores. The activation process involves the activation gas reacting with carbon in a redox reaction, eroding the surface of the carbonized material and simultaneously removing tar-like substances and uncarbonized materials, resulting in a well-developed microporous structure. Through gas activation, the previously closed pores of the carbonized material are opened, existing pores expand, and new pores are formed. Reactions such as C + H₂O = H₂ + CO and C + CO₂ = 2CO typically occur. Different activators have different chemical properties, and their reaction rates with carbon also differ. When air is used as the activator, the reaction rate between carbon and oxygen is relatively fast, requiring only around 600℃ for activation, but the reaction is uneven. Activation with steam requires 750–1000℃. Because steam can fully diffuse into the micropores of the carbon, the activation reaction can proceed uniformly throughout the entire carbon particle, resulting in powdered activated carbon with a large specific surface area and strong adsorption capacity. CO2 activation is currently mostly used in laboratories because the molecular size of H2O is smaller than that of CO2, and the diffusion rate of H2O within the particles is greater than that of CO2, resulting in a shorter activation reaction time. Generally speaking, for physical activation, steam is considered to be the most effective activator.

[0005] Since the physical activation method does not introduce chemical activators, it causes less environmental pollution. However, the activation reactions all occur at high temperatures, which has disadvantages such as high energy consumption of high-temperature furnaces, strict requirements on particle size (usually around 200 mesh), long activation time, high equipment requirements, low product yield, poor uniformity, and low adsorption performance.

[0006] How can we solve the current problems of limited coal-based powdered activated carbon production methods, high energy consumption, limited coal types, low adsorption performance, and difficulty in recovering and utilizing tail gas, while achieving strong adaptability to different coal types, low energy consumption, rapid preparation of powdered activated carbon with high adsorption performance, and recovery and utilization of tail gas?

[0007] Therefore, the present invention provides a method and apparatus for preparing coal-derived activated carbon. Summary of the Invention

[0008] To address the challenges of existing technologies, such as the limited availability of coal-based powdered activated carbon, high energy consumption, restricted coal types, low adsorption performance, and difficulty in recovering and utilizing tail gas, this invention provides a coal-based activated carbon preparation method and apparatus that achieves strong adaptability to different coal types, low energy consumption, rapid preparation of high-adsorption-performance powdered activated carbon, and tail gas recovery and utilization.

[0009] The present invention provides a method and apparatus for preparing coal-derived activated carbon, which is achieved through the following technical solutions:

[0010] The first objective of this invention is to provide a method for preparing coal-derived activated carbon, comprising the following steps:

[0011] Step 1: After pre-treating the coal, perform ash removal treatment to obtain ash-removed coal powder;

[0012] Step 2: Disperse the ash-removing coal powder, powdered activated carbon, and binder evenly in an aqueous solvent to obtain a mixture.

[0013] Step 3: The mixture is activated by microwave heating, and acid and alkali solutions that have been preheated and vaporized by microwave are alternately injected during the microwave heating process. After the activation treatment is completed, gaseous components and solid components are obtained; wherein the obtained solid components are the coal-derived activated carbon.

[0014] Furthermore, the binder is coal tar, and the mass ratio of the ash-removing coal powder, powdered activated carbon, binder and water solvent is 10-30:1:1:2-5.

[0015] Furthermore, the microwave heating is carried out under vacuum conditions with an absolute pressure of 0.1 to 92 kPa, and the microwave frequency of the microwave heating is 2450 MHz, and the power is 0.2 to 10 kW.

[0016] Furthermore, during microwave heating, the activation temperature in the activation device is 450–650°C, and the activation time is 0.2–0.6 h.

[0017] Furthermore, the acid solution is nitric acid with a mass concentration of 50% to 68%; the alkaline solution is ammonia water with a mass concentration of 2% to 5%.

[0018] Furthermore, when alternating between the acid and alkali solutions that have been preheated and vaporized by microwave, the acid and alkali solutions are injected continuously at intervals of 5 to 10 seconds.

[0019] Furthermore, the ash-removed coal powder is obtained through the following steps:

[0020] S1. After crushing the coal to 40-200 mesh, coal powder is obtained;

[0021] S2. Mix hydrochloric acid, fluorosilicic acid and water in a mass ratio of 1:1:7 to obtain a descaling agent;

[0022] S3. Add the coal powder to the ash removal agent, stir, filter and dry to obtain the ash removal coal powder;

[0023] The liquid-to-solid mass ratio of the ash remover to the coal powder is 4-8:1.

[0024] The stirring rate of the stirring process is 300-1000 r / min, and the stirring time is 0.5-1 h.

[0025] Furthermore, it also includes step 4, which involves initial cooling the gas phase component at a temperature of 60-75°C to obtain condensed coal tar and tail gas component A;

[0026] The exhaust gas component A is subjected to final cooling at a temperature of 15-20°C to obtain condensed alkaline solution and exhaust gas component B.

[0027] A second objective of this invention is to provide a coal-derived activated carbon prepared by the above-described preparation method.

[0028] A third objective of this invention is to provide an apparatus for preparing coal-derived activated carbon, comprising an activation device, an activator supply device, a tail gas treatment device, and a microwave heater.

[0029] The microwave heater is used to provide microwave energy to the activation device; the activator supply device is connected to the feed end of the activation device, and the exhaust gas treatment device is connected to the discharge end of the activation device.

[0030] The activator supply device includes:

[0031] An acid supply device, which contains acid;

[0032] An alkaline solution supply device, which contains alkaline solution;

[0033] A spiral hollow tube A is installed inside the microwave heater. One end of the tube is connected to the outlet of the acid supply device through a feed pipe A, and the other end is connected to the inlet of the activation device through a feed pipe B, so as to introduce the acid in the acid supply device into the activation device.

[0034] A spiral hollow tube B is installed inside the microwave heater. One end of the tube is connected to the outlet of the alkali supply device through a feed pipe C, and the other end is connected to the inlet of the activation device through a feed pipe D, so as to introduce the alkali solution in the alkali supply device into the activation device.

[0035] Along its conveying direction, the conveying pipe A is sequentially equipped with a pump body A, a rotor flow meter A, a solenoid valve A, and a syringe A. The pump body A pumps the acid from the acid supply device into the conveying pipe A, and with the solenoid valve A open, the acid is introduced into the syringe A. Then, the syringe 4 injects the acid into the spiral hollow tube A. The acid entering the spiral hollow tube A is vaporized into acid vapor under microwave action. The acid vapor then enters the activation device and reacts with the raw materials in the activation device under microwave action.

[0036] Along its conveying direction, the conveying pipe C is sequentially equipped with a pump body B, a rotor flow meter B, a solenoid valve B, and a syringe B. The pump body B pumps the alkali solution from the alkali supply device into the conveying pipe B. With the solenoid valve B open, the alkali solution is introduced into the syringe B, and then injected into the spiral hollow tube B. The alkali solution entering the spiral hollow tube B is vaporized into alkali vapor under microwave action. The alkali vapor then enters the activation device and reacts with the raw materials in the activation device under microwave action.

[0037] The rotor flowmeters A and B are used to accurately calculate the amount of acid and alkali injected into the activation device. In order to facilitate alternating injection, a shut-off valve A is provided on the feed pipe B and a shut-off valve B is provided on the feed pipe D. The shut-off valves A and B control the start or stop of injecting the acid in the spiral hollow tube A and the alkali in the spiral hollow tube B into the activation device, respectively.

[0038] Furthermore, the activation device includes an activator, which has a cylindrical structure with openings at both ends, and inside it, along its feeding direction, are arranged sequentially a sealing plug A, a quartz glass plate A, a quartz glass plate B, and a sealing plug B.

[0039] The quartz glass plate A and the quartz glass plate B are both vertically arranged inside the activator, and a cavity structure is formed between the quartz glass plate A and the quartz glass plate B. The cavity structure is used to place the raw materials for the preparation of coal-based activated carbon.

[0040] The quartz glass plate is provided with a through hole A, and the sealing plug A is provided with a through hole B. The through hole B and the through hole A are located on the same horizontal plane. The feed pipe passes through the through hole B and the through hole A in sequence. The discharge end of the feed pipe is connected to the cavity structure. The feed end of the feed pipe is connected to the discharge ends of the conveying pipe B and the conveying pipe D. It is used to inject acid and / or alkali solution into the cavity structure inside the activator through the through hole A.

[0041] A discharge channel is formed between the quartz glass plate B and the sealing plug B. The quartz glass plate B is provided with multiple through holes C, and the sealing plug B is provided with through holes D. The through holes D are connected to the inlet end of the discharge pipe, and the outlet end of the discharge pipe is connected to the tail gas treatment device, so that the gas generated during the reaction in the activator enters the discharge channel through the through holes C, then enters the discharge pipe through the through holes D, and is discharged into the tail gas treatment device for tail gas treatment.

[0042] Furthermore, the exhaust gas treatment device includes:

[0043] A primary cooler is connected to the discharge end of the discharge pipe. The outlet temperature of the primary cooler is 60-75°C. It is used to condense the coal tar in the exhaust gas so as to facilitate the recovery of coal tar.

[0044] The final cooler is connected to the outlet of the primary cooler through a gas guide pipe. The outlet temperature of the final cooler is 15-20°C. It is used to condense the ammonia water in the tail gas so that the condensed ammonia water can be returned to the alkali supply device to realize the repeated recycling of alkali.

[0045] A gas collection device is connected to the outlet of the final cooler and is used to collect the gas components in the remaining exhaust gas.

[0046] A vacuum pump is also installed on the gas guide pipe. The vacuum pump is used to perform vacuuming to provide a vacuum environment for the activator, and is also used to introduce the exhaust gas after the primary cooler into the final cooler.

[0047] Compared with the prior art, the present invention has the following advantages:

[0048] This invention uses microwaves as a heat source to provide heat for activating raw materials to prepare coal-based activated carbon. Specifically, coal is used as the raw material, powdered activated carbon as the microwave absorber and heat transfer medium, concentrated nitric acid and dilute ammonia as activators, and coal tar as a binder to prepare the powdered activated carbon. After ash removal, the coal is mixed with the powdered activated carbon, binder, and water to form a mixture. Activation is then performed using microwave heating. During microwave heating, concentrated nitric acid and dilute ammonia are injected alternately at regular intervals. The injected concentrated nitric acid and dilute ammonia vaporize and contact the mixture, thereby activating the coal raw material under microwave conditions. Furthermore, the coal-based activated carbon prepared by this method has a specific surface area exceeding 1400 m². 2 / g, with an adsorption value of methylene blue exceeding 180mg / g.

[0049] Conventional methods for preparing powdered activated carbon involve two steps: carbonization and activation. Carbonization takes 1–2 hours, and activation takes 2–4 hours. The method of this invention completes carbonization and activation in one step, with a time not exceeding 0.6 hours, significantly shortening the preparation time of powdered activated carbon. The activation reaction generates a large number of small gas molecules, greatly improving the specific surface area and adsorption capacity of the powdered activated carbon, with a yield exceeding 50%. It has strong adaptability to various coal types; anthracite, bituminous coal, lignite, and other typical coal types and their mixtures can all be used as raw materials for preparing powdered activated carbon. Furthermore, the process is simple and energy-efficient.

[0050] The vacuum conditions of this invention greatly improve the volatilization rate of coal tar. At the same time, due to the stripping effect of concentrated nitric acid and dilute ammonia vaporization, the coal tar can be completely volatilized at a relatively low activation temperature (450-650°C) in the activator, and carbonization is completed in the early stage of activation. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the coal-to-activated carbon preparation process of the present invention;

[0052] Figure 2 This is a schematic diagram of the preparation device of the present invention, wherein the arrows indicate the direction of material flow. Detailed Implementation

[0053] The technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0054] This invention provides coal-derived activated carbon, which is prepared by the following steps:

[0055] Step 1: After pre-treating the coal, perform ash removal treatment to obtain ash-removed coal powder;

[0056] It should be noted that this invention does not limit the type of coal raw material and has strong adaptability to different coal types. It can be selected according to actual conditions, such as one or more of anthracite, bituminous coal, and lignite. However, this invention considers that the coal raw material may contain ash, which increases the amount of activator and heat consumption, and reduces the specific surface area and adsorption performance of activated carbon. Therefore, to improve the subsequent activation effect, this invention requires ash removal treatment of the coal raw material before use. This ash removal reduces the inorganic mineral content, increases the carbon content, and improves the performance of the activated carbon product. Furthermore, this invention considers that existing technologies typically use mixed solutions of single acids such as hydrochloric acid, fluorosilicic acid, and hydrofluoric acid with water for ash removal. However, this method has poor ash removal efficiency, only reaching 20%–50%, which cannot meet the requirement of increasing the carbon content of the activated carbon product. Therefore, this invention preferably uses a mixed solution of hydrochloric acid, fluorosilicic acid, and water as the ash removal agent. Hydrochloric acid mainly removes acid-soluble components from the ash, while fluorosilicic acid mainly removes components that hydrochloric acid cannot dissolve, achieving an ash removal rate of over 80%. Furthermore, the present invention can specifically perform ash removal treatment through the following steps (S1-S2):

[0057] S1. After crushing the coal to 40-200 mesh, coal powder is obtained;

[0058] S2. Mix hydrochloric acid, fluorosilicic acid and water in a mass ratio of 1:1:7 to obtain a descaling agent;

[0059] S3. According to the liquid-solid mass ratio of the ash remover to the coal powder of 4 to 8:1, the coal powder is added to the ash remover, and then stirred at a temperature of 10 to 30°C for 0.5 to 1 hour. After filtration and drying, the ash-removed coal powder is obtained.

[0060] Step 2: Disperse the ash-removing coal powder, powdered activated carbon, and binder evenly in an aqueous solvent to obtain a mixture.

[0061] It should be noted that this invention takes into account the limited microwave absorption capacity of ash-removed coal powder, making it difficult to heat up to the activation temperature in a microwave field. Therefore, powdered activated carbon is added as a microwave absorber and heat transfer medium in the microwave field. The powdered activated carbon rapidly generates high-temperature "hot spots" in the microwave field and transfers heat to the ash-removed coal powder, rapidly heating it to the activation temperature in the activator. Using powdered activated carbon as the microwave absorber and heat transfer medium offers advantages such as good microwave absorption performance, fast heat transfer, and low dosage. Furthermore, since both the product and the microwave absorber are powdered activated carbon, no new impurities are introduced, and separation is not required after activation.

[0062] Furthermore, this invention uses coal tar as a binder and powdered activated carbon as a microwave absorber and heat transfer medium. The ash-removing coal powder, powdered activated carbon, binder and water are mixed in a mass ratio of 10-30:1:1:2-5 to obtain a mixture.

[0063] Step 3: Microwave heating is performed on the mixture, and acid and alkali solutions that have been preheated and vaporized by microwave are alternately injected during the microwave heating process to obtain gaseous components and solid components. The obtained solid components are the coal-derived activated carbon.

[0064] It should be noted that the present invention preferably uses concentrated nitric acid and dilute ammonia as activators, which not only has a lower raw material cost than zinc chloride activator conventionally used in the field, but also leaves no zinc ion residue. Furthermore, the present invention considers that increasing the mass fraction of concentrated nitric acid is beneficial to increasing the specific surface area and yield of powdered activated carbon. However, when the nitric acid concentration is higher than 68%, further increasing the concentration of concentrated nitric acid does not significantly improve the specific surface area and yield of powdered activated carbon. Therefore, concentrated nitric acid with a mass concentration of 50%–68% is selected as the acid solution. The present invention also considers that increasing the mass fraction of dilute ammonia is beneficial to increasing the specific surface area and yield of powdered activated carbon. However, when the mass fraction of dilute ammonia is higher than 5%, further increasing the concentration of dilute ammonia does not significantly improve the specific surface area and yield of powdered activated carbon. Therefore, dilute ammonia with a mass concentration of 2%–5% is used as the alkaline solution, and both are used as activators, alternately injected during microwave heating.

[0065] The present invention also considers that by pre-treating concentrated nitric acid and dilute ammonia with microwave and then mixing them with the above-mentioned mixture, and by alternately injecting the microwave-preheated and vaporized acid and alkali solutions, the cycle can be shortened, which is beneficial to improving the specific surface area and yield of powdered activated carbon. However, when the cycle is shortened to less than 5 seconds, the improvement in the specific surface area and yield of powdered activated carbon is not significant. Therefore, it is preferable that the acid and alkali solutions are injected continuously at intervals of 5 to 10 seconds to ensure that the gas phase concentration of concentrated nitric acid and dilute ammonia in the reactor is uniform and that the reaction rate of carbon and nitric acid is guaranteed. On the other hand, it promotes the reaction of ammonia and nitrogen dioxide, which greatly improves the degree of reaction.

[0066] To ensure sufficient activation of the coal raw material, this invention utilizes microwave heating under vacuum conditions with an absolute pressure of 0.1–92 kPa, with a microwave frequency of 2450 MHz and a power of 0.2–10 kW. During microwave heating, the inventors discovered that increasing the activation temperature is beneficial for improving the specific surface area and yield of the powdered activated carbon. However, when the activation temperature exceeds 650°C, further increases in temperature actually decrease the specific surface area and yield of the powdered activated carbon. Therefore, the microwave frequency of the microwave heater 1 is set to 2450 MHz, and the activation reaction temperature is set to 450–650°C. It was also found that extending the activation time is beneficial for improving the specific surface area and yield of the powdered activated carbon, but when the activation time exceeds 0.6 hours, the specific surface area and yield of the powdered activated carbon actually decrease. Therefore, the activation time is controlled at 0.2–0.6 hours. Furthermore, the activation temperature of this invention is significantly lower than the conventional activation temperature of 750–1100°C, and the activation time is also significantly lower than the conventional carbonization-activation time of 3–6 hours, greatly reducing energy consumption and production cycle.

[0067] Furthermore, during microwave heating, concentrated nitric acid vapor and dilute ammonia vapor undergo an activation reaction with high-temperature pulverized coal under vacuum conditions in the activator. The main reactions in the activation process are:

[0068] 1) C + 4HNO3 (conc.) = CO2 + 4NO2 + 2H2O;

[0069] 2) 6NO₂ + 8NH₃ = 7N₂ + 12H₂O;

[0070] 3) 2C + 2NO2 = 2CO2 + N2;

[0071] 4) C + H₂O = CO + H₂;

[0072] 5) C + 2H₂O = CO₂ + 2H₂;

[0073] Side reactions during the activation process include:

[0074] 1) 3C + 2HNO3 (conc.) = 3CO + 2NO + H2O;

[0075] 2) 3C + 4HNO3 (conc.) = 3CO2 + 4NO + 2H2O;

[0076] 3) 2C + 2H₂O = CH₄ + CO₂;

[0077] 4) 3C + 2H2O = CH4 + 2CO.

[0078] All nine reactions described above are gas expansion reactions that occur inside the mixture during the activation process, which greatly increases the amount and rate of small molecule gas generation and shortens the activation time.

[0079] After microwave heating, the obtained solid phase is coal-derived activated carbon, and tests show that the specific surface area of ​​the coal-derived activated carbon prepared by this invention exceeds 1400 m². 2 / g, with an adsorption value of methylene blue exceeding 180mg / g.

[0080] This invention takes into account the large amount of gas generated during microwave heating. To avoid environmental and resource waste caused by the chemical components in the gas, the following post-processing is performed on the gas components generated during microwave heating:

[0081] The gaseous components are initially cooled at 60–75°C to obtain condensed coal tar and tail gas component A. Then, tail gas component A is finally cooled at 15–20°C to obtain condensed alkaline solution and tail gas component B. A small portion of the condensed coal tar is recycled, while the majority is used as a byproduct. The condensed ammonia water can be returned to step 3 for recycling as an activator. Tail gas component B contains 20%–30% CO2, 10%–20% CO, 5%–15% H2, 10%–30% N2, 5%–15% NO, 5%–15% O2, and 5%–15% CH4. The treated tail gas can be used as syngas, a hydrogen source, or manufactured gas.

[0082] Therefore, the preparation method of this invention can not only prepare high-performance powdered activated carbon, but also achieve low-energy consumption and short-cycle preparation, and can also realize the recovery and utilization of tail gas. This allows the coal tar volatilized during the activation process and the coal tar used as a binder to be condensed after initial cooling treatment, with a portion used as a byproduct and the remainder recycled as a binder; the ammonia water condensed after final cooling treatment is recycled after replenishing ammonia, further reducing costs.

[0083] To facilitate the preparation of coal-derived activated carbon according to the above method, the present invention also provides a preparation apparatus based on the above preparation method. The preparation apparatus of the present invention includes an activation device, an activator supply device, a tail gas treatment device, and a microwave heater 1. The microwave heater 1 is used to provide microwave energy to the activation device, using microwaves as a heat source. The activator supply device is connected to the feed end of the activation device, and the tail gas treatment device is connected to the discharge end of the activation device.

[0084] The activator supply device of the present invention includes an acid supply device 2, an alkali supply device 3, a spiral hollow tube A4, and a spiral hollow tube B7.

[0085] The acid supply device 2 contains acid, specifically concentrated nitric acid with a mass concentration of 50% to 68%; the alkali supply device 3 contains alkali, specifically dilute ammonia with a mass concentration of 2% to 5%.

[0086] A spiral hollow tube A4 is installed inside the microwave heater 1. One end of the tube is connected to the outlet of the acid supply device 2 through a feed pipe A5, and the other end is connected to the inlet of the activation device through a feed pipe B6. This allows the concentrated nitric acid to be preheated by microwaves in the spiral hollow tube A4 under the action of microwaves provided by the microwave heater 1 to vaporize the concentrated nitric acid. The vaporized concentrated nitric acid vapor is then introduced into the activation device. To facilitate control over the process and amount of concentrated nitric acid vapor introduced into the activation device, a pump body A10, a rotor flowmeter A11, a solenoid valve A12, and a syringe A13 are sequentially installed along the conveying direction of the feed pipe A5. The pump body A10 pumps the acid from the acid supply device 2 into the feed pipe A5, and with the solenoid valve A12 open, the acid is introduced into the syringe A13. Then, the syringe 4 injects the acid into the spiral hollow tube A4. The acid entering the spiral hollow tube A4 is vaporized into acid vapor under microwave action. The acid vapor then enters the activation device and reacts with the raw materials in the activation device under microwave action.

[0087] The spiral hollow tube B7 is also installed inside the microwave heater 1. One end of it is connected to the outlet end of the alkali supply device 3 through the feed pipe C8, and the other end is connected to the inlet end of the activation device through the feed pipe D9, so as to introduce the dilute ammonia water in the alkali supply device 3 into the activation device, so that the dilute ammonia water can be microwave preheated in the spiral hollow tube A4 under the action of microwave provided by the microwave heater 1 to realize the vaporization of dilute ammonia water, and then the vaporized dilute ammonia water vapor is introduced into the activation device. Furthermore, to facilitate control over the process and amount of dilute ammonia water vapor introduced into the activation device, a pump body B14, a rotor flowmeter B15, a solenoid valve B16, and a syringe B17 are sequentially installed along the conveying direction of the conveying pipe C8. The pump body B14 pumps the dilute ammonia water from the alkali supply device 3 into the conveying pipe B6, and with the solenoid valve B16 open, the dilute ammonia water is introduced into the syringe B17. Then, the syringe B17 injects the dilute ammonia water into the spiral hollow tube B7. The dilute ammonia water entering the spiral hollow tube B7 is vaporized into dilute ammonia water vapor under the action of microwaves. The dilute ammonia water vapor then enters the activation device and reacts with the raw materials in the activation device under the action of microwaves.

[0088] The rotor flowmeters A11 and B15 are used to accurately calculate the amounts of concentrated nitric acid and dilute ammonia injected into the activation device. To facilitate alternating injection, a shut-off valve A18 is installed on the feed pipe B6, and a shut-off valve B19 is installed on the feed pipe D9. Shut-off valves A18 and B19 respectively control the start or stop of injecting the acid solution from the spiral hollow tube A4 and the alkali solution from the spiral hollow tube B7 into the activation device. To ensure the activation effect of concentrated and dilute nitric acid on the raw materials, preferably, the mass flow rate of concentrated nitric acid is controlled at 2.4–8 kg / (kg microwave absorber·h) using rotor flowmeters A11 and B15, and the mass flow rate of dilute ammonia is 18–58 kg / (kg microwave absorber·h). In this case, the space-time yield of the microwave absorber is 6.25–30 kg of powdered activated carbon / (kg microwave absorber·h).

[0089] It should also be noted that, to further ensure the vaporization effect of concentrated and dilute nitric acid, the length and size of the spiral hollow tubes A4 and B7 can be adjusted to limit the microwave preheating effect of the concentrated and dilute nitric acid, thereby ensuring their vaporization effect. The spiral hollow tube A4 used in this invention has 2-10 turns, a spiral diameter of 3-32 cm, and an inner diameter of 4-40 mm. The spiral hollow tube B7 has 5-60 turns, a spiral diameter of 3-60 cm, and an inner diameter of 4-40 mm. When placing the spiral hollow tubes A4 and B7, after the microwave is started, the inlet temperatures of the spiral hollow tubes A4 and B7 should be 95-120°C and 95-105°C, respectively, to ensure the vaporization effect of the concentrated and dilute nitric acid.

[0090] Furthermore, the activation device of the present invention includes an activator 20, which is a cylindrical structure with open ends, and a sealing plug A21, a quartz glass plate A22, a quartz glass plate B23 and a sealing plug B24 are arranged sequentially inside it along its feeding direction.

[0091] The quartz glass plate A22 and the quartz glass plate B23 are both vertically arranged inside the activator 20, and a cavity structure A is formed between the quartz glass plate A22 and the quartz glass plate B23. The cavity structure A is used to place the raw materials for preparing coal-based activated carbon, namely the mixture obtained by uniformly dispersing ash-removing coal powder, powdered activated carbon, and binder in an aqueous solvent.

[0092] The quartz glass plate has a through hole A, and the sealing plug A21 has a through hole B. The through hole B and the through hole A are located on the same horizontal plane. The feed pipe 25 is sequentially inserted into the through hole B and the through hole A. The discharge end of the feed pipe 25 is connected to the cavity structure A. The feed end of the feed pipe 25 is connected to the discharge ends of the conveying pipe B6 and the conveying pipe D9. It is used to inject acid and / or alkali solution into the cavity structure A in the activator 20 through the through hole A. To further ensure sufficient contact between the activator (i.e., concentrated nitric acid vapor and dilute nitric acid vapor) and the raw materials prepared in the activator 20, the feed pipe 25 of this invention has an inner diameter of 4-40 mm and a length of 5-95 cm in contact with the material. Circular holes are opened at 2-5 mm intervals along the length, with 2-10 holes per cycle. The diameter of the holes is 0.5-1 mm, allowing the activator (concentrated nitric acid and dilute ammonia) to be dispersed through these holes, ensuring a full reaction between the activator and carbon. Simultaneously, the activation reaction produces a large number of small gaseous molecules, significantly increasing the micropore (less than 2 nanometers) ratio and specific surface area of ​​the powdered activated carbon, and raising the yield of powdered activated carbon from approximately 40% to 50%-60%. The purified exhaust gas can be used as syngas, hydrogen source, or manufactured gas.

[0093] A discharge channel B is formed between the quartz glass plate B23 and the sealing plug B24. The quartz glass plate B23 has multiple through holes C, and the sealing plug B24 has a through hole D. The through hole D communicates with the inlet end of the discharge pipe 26, and the outlet end of the discharge pipe 26 communicates with the exhaust gas treatment device. This allows the gas generated during the reaction in the activator 20 to enter the discharge channel B through the through holes C, then enter the discharge pipe 26 through the through hole D, and finally be discharged into the exhaust gas treatment device for exhaust gas treatment. To ensure smooth gas discharge, preferably, the multiple through holes C are arranged in an equilateral triangle on the quartz glass plate B23, with a diameter r = 0.5–3 mm and a center distance d = 10–20r.

[0094] It should also be noted that, in order to ensure the activation effect within the activator 20, the diameter of the activator 20 is 2 to 20 cm, the length is 10 to 100 cm, the loading coefficient is controlled at 0.65 to 0.85, and the total resistance in the activator 20 is maintained at 0.2 to 90 kPa, wherein the inlet absolute pressure is 0.3 to 92 kPa, and the outlet absolute pressure is 0.1 to 2 kPa.

[0095] Furthermore, the activation reaction is carried out under vacuum, creating a pressure difference between the inlet and outlet of the activator 20. This has the following advantages: 1) It lowers the boiling point of coal tar, creating conditions for steam stripping, allowing the coal tar, acting as a binder, and other coal tar in the coal to volatilize completely at a lower activation temperature. 2) It creates a pressure gradient between the reactor and the gas outlet, promptly carrying steam, coal tar, and reactant gases out of the reactor. 3) The activation process involves gas expansion; timely gas extraction can shift the reaction to the right. On one hand, this significantly increases the activation rate and shortens the preparation cycle. On the other hand, it prevents the accumulation and expansion of small gas molecules in the micropores, increasing the micropore ratio.

[0096] The exhaust gas treatment device of the present invention includes a primary cooler 27, a final cooler 28, and a gas collection device 30, sequentially arranged at the discharge end of the discharge pipe 26. The primary cooler 27 is connected to the discharge end of the discharge pipe 26, and its outlet temperature is 60-75°C. It is used to condense coal tar in the exhaust gas for recovery. The final cooler 28 is connected to the outlet end of the primary cooler 27 via a gas guide pipe 29, and its outlet temperature is 15-20°C. It is used to condense ammonia in the exhaust gas, allowing the condensed ammonia to be returned to the alkali supply device 3 for repeated recycling of the alkali. The gas collection device 30 is connected to the outlet end of the final cooler 28 and is used to collect the remaining gas components in the exhaust gas. Furthermore, a vacuum pump 31 is installed on the gas duct 29. The vacuum pump 31 is used to perform vacuuming to provide a vacuum environment for the activator 20, so as to ensure that the activator 20 performs microwave heating under vacuum conditions with an absolute pressure of 0.1 to 92 kPa. The vacuum pump 31 can also introduce the exhaust gas after being processed by the primary cooler 27 into the final cooler 28.

[0097] It should also be noted that, in order to ensure the successful preparation of the coal-based activated carbon of this invention via microwave heating, and considering that the microwave transmittance of ceramic, plastic, and other materials is not as good as that of quartz glass, the present invention...

[0098] Therefore, the activator 20, the spiral hollow tube A4, and the spiral hollow tube B7 in the preparation apparatus of the present invention are preferably made of quartz glass. Quartz glass has good microwave transmittance, which allows the material inside the quartz glass to absorb microwaves and react effectively. Furthermore, the connecting components in the preparation apparatus of the present invention that connect to the activator 20, the spiral hollow tube A4, and the spiral hollow tube B7, namely, the feed pipe A5, the feed pipe C8, the feed pipe D9, the feed pipe B6, the inlet pipe 25, and the outlet pipe 26, are also preferably made of quartz glass.

[0099] Furthermore, when preparing activated carbon using the apparatus of this invention, the prepared raw materials for coal-based activated carbon, namely the mixture obtained by mixing the above-mentioned ash-removing coal powder with powdered activated carbon, binder, and water, are first placed in the activator 20, and then processed according to the following steps... Figure 2 The structure shown is used to install and connect the various components in sequence. After installation, the microwave heater 1 is turned on. At this time, the raw materials in the activator 20 are subjected to instantaneous and uniform heating by microwaves and stripping under vacuum conditions. Carbonization is completed in the early stage of activation. At the same time, the concentrated nitric acid and dilute ammonia water entering the spiral hollow tube A4 and spiral hollow tube B7 are vaporized under the action of microwaves. That is to say, before the concentrated nitric acid and dilute ammonia water are mixed with the raw materials, the concentrated nitric acid and dilute ammonia water have already been vaporized under the action of microwaves, and the raw materials are carbonized. Activation will begin after the concentrated nitric acid vapor and dilute ammonia water vapor come into contact with the carbonized raw materials. Thus, the activation process and carbonization process are completed in one step by microwave heating alone, which greatly reduces the energy consumption and production cycle of carbonization-activation.

[0100] The BET specific surface area of ​​the prepared powdered activated carbon is 1400–2100 m². 2 / g, methylene blue adsorption value is 180-260 mg / g, iodine value is 1200-1700 mg / g. A small portion of the powdered activated carbon is recycled as a microwave absorber, and the remainder is used as the main product of powdered activated carbon. The outlet gas of activator 20 undergoes two-stage condensation. The outlet temperature of the primary cooler is 60-75℃, which condenses coal tar, etc. A small portion of the recovered coal tar is recycled, and most of it is used as a by-product. The outlet temperature of the final cooler 28 is 15-20℃, which condenses ammonia, etc. The condensed ammonia is recycled after replenishment with ammonia. The heat of the hot water and steam generated by the primary cooler and final cooler 28 is recovered and utilized. The content of CO2 in the condensed tail gas is 20%-30%; CO content is 10%-20%; H2 content is 5%-15%; N2 content is 10%-30%; NO content is 5%-15%; O2 content is 5%-15%; CH4 content is 5%-15%. After treatment, the exhaust gas can be used as syngas, hydrogen source, or manufactured gas. This process provides a new approach for the low-energy, short-cycle preparation of high-performance powdered activated carbon and the recovery and utilization of exhaust gas.

[0101] The industrial analysis and elemental analysis of the raw coal used in the following embodiments of the present invention are shown in Table 1.

[0102] Table 1. Industrial and elemental analysis of coal

[0103]

[0104] Example 1

[0105] This embodiment provides a coal-based activated carbon, which is prepared using the above-described preparation apparatus through the following steps:

[0106] Two kilograms of anthracite were crushed to 80 mesh. Concentrated hydrochloric acid, fluorosilicic acid and water were mixed in a mass ratio of 1:1:7 and then added to the anthracite powder in a liquid-solid mass ratio of 5:1. After stirring for 0.5 hours, the mixture was filtered and dried to obtain ash-removed coal powder.

[0107] The ash-removing coal powder, powdered activated carbon, coal tar, and water were mixed in a mass ratio of 10:1:1:2 and then loaded into a quartz glass activator 20, with a loading coefficient of 0.8. The microwave power was controlled at 3kW, the activation temperature at 650℃, the activator inlet absolute pressure at 30kPa, and the outlet absolute pressure at 0.5kPa. The concentrated nitric acid had a mass fraction of 65%, and its inlet mass flow rate was controlled at 4kg / (kg absorber·h), with an activator inlet temperature of 110℃. The dilute ammonia solution had a mass fraction of 3%, and its inlet mass flow rate was controlled at 20kg / (kg absorber·h), with an activator inlet temperature of 100℃.

[0108] Concentrated nitric acid and dilute ammonia were alternately injected into the activator at 10-second intervals, and the activation time was 0.6 hours. The resulting powdered activated carbon had a BET specific surface area of ​​1844 m². 2 / g, methylene blue adsorption value is 249m 2 The iodine value is 1546 mg / g, and the yield is 58%. The composition of the tail gas after passing through the primary cooler 27 and the final cooler 28 is shown in Table 2. After purification, the tail gas can be used as syngas, hydrogen source, manufactured gas, etc. Ammonia water is recycled after ammonia replenishment; coal tar is partially recycled, and the remainder is used as a by-product.

[0109] Table 2. Composition and content of exhaust gas after treatment in Example 1

[0110] Exhaust gas composition <![CDATA[CO2]]> CO <![CDATA[H2]]> <![CDATA[N2]]> NO <![CDATA[O2]]> <![CDATA[CH4]]> Volume fraction 30.5％ 19.4％ 8.6％ 16.1％ 7.6％ 7.9％ 9.9％

[0111] Example 2

[0112] This embodiment provides a coal-based activated carbon, which is prepared using the above-described preparation apparatus through the following steps:

[0113] 1 kg of bituminous coal was crushed to 100 mesh. Concentrated hydrochloric acid, fluorosilicic acid, and water were mixed at a mass ratio of 1:1:7 and added to the coal powder at a liquid-to-solid mass ratio of 5:1. After stirring for 0.5 h, the mixture was filtered and dried to obtain ash-removed coal powder. The ash-removed coal powder was mixed with powdered activated carbon, coal tar, and water at a mass ratio of 20:1:1:4 and then loaded into a quartz glass activator with a loading coefficient of 0.7. The microwave power was controlled at 1.5 kW, the activation temperature at 550 °C, the activator inlet absolute pressure at 20 kPa, and the outlet absolute pressure at 0.5 kPa. Concentrated nitric acid had a mass fraction of 65%, with an inlet mass flow rate of 6 kg / (kg absorber·h) and an activator inlet temperature of 110 °C. Dilute ammonia had a mass fraction of 3%, with an inlet mass flow rate of 30 kg / (kg absorber·h) and an activator inlet temperature of 100 °C. Concentrated nitric acid and dilute ammonia were alternately injected into the activator at 5-second intervals, and the activation time was 0.5 hours. The resulting powdered activated carbon had a BET specific surface area of ​​1562 m². 2 / g, methylene blue adsorption value is 224m 2 The iodine value is 1315 mg / g, and the yield is 55%. The composition of the tail gas after passing through the primary cooler 27 and the final cooler 28 is shown in Table 3. After purification, the tail gas can be used as syngas, hydrogen source, manufactured gas, etc. Ammonia water is recycled after ammonia replenishment; coal tar is partially recycled, and the remainder is used as a by-product.

[0114] Table 3. Composition and content of exhaust gas after treatment in Example 2

[0115] Exhaust gas composition <![CDATA[CO2]]> CO <![CDATA[H2]]> <![CDATA[N2]]> NO <![CDATA[O2]]> <![CDATA[CH4]]> Volume fraction 24.6％ 18.9％ 9.8％ 18.9％ 8.8％ 6.6％ 10.9％

[0116] Example 3

[0117] This embodiment provides a coal-based activated carbon, which is prepared using the above-described preparation apparatus through the following steps:

[0118] 0.5 kg of lignite was crushed to 120 mesh. Concentrated hydrochloric acid, fluorosilicic acid and water were mixed in a mass ratio of 1:1:7 and then added to the lignite powder in a liquid-solid mass ratio of 5:1. After stirring for 0.5 h, the mixture was filtered and dried to obtain ash-removed coal powder.

[0119] The ash-removing coal powder, powdered activated carbon, coal tar, and water were mixed in a mass ratio of 30:1:1:5 and then loaded into a quartz glass activator with a loading coefficient of 0.6. The microwave power was controlled at 1kW, the activation temperature at 450℃, the absolute pressure at the activator inlet at 15kPa, and the absolute pressure at the outlet at 0.5kPa.

[0120] The concentrated nitric acid had a mass fraction of 65%, with an inlet mass flow rate of 8 kg / (kg absorber·h) and an activator inlet temperature of 110℃. The dilute ammonia had a mass fraction of 3%, with an inlet mass flow rate of 40 kg / (kg absorber·h) and an activator inlet temperature of 100℃. The concentrated nitric acid and dilute ammonia were alternately injected into the activator at 5-second intervals, with an activation time of 0.4 h. The resulting powdered activated carbon had a BET specific surface area of ​​1488 m². 2 / g, methylene blue adsorption value is 210m 2 The iodine value is 1284 mg / g, and the yield is 52%. The composition of the tail gas after passing through the primary cooler 27 and the final cooler 28 is shown in Table 4. After purification, the tail gas can be used as a hydrogen source, manufactured gas, syngas, etc. Ammonia water is recycled after replenishment; coal tar is partially recycled, and the remainder is used as a by-product.

[0121] Table 4. Composition and content of exhaust gas after treatment in Example 3

[0122] Exhaust gas composition <![CDATA[CO2]]> CO <![CDATA[H2]]> <![CDATA[N2]]> NO <![CDATA[O2]]> <![CDATA[CH4]]> Volume fraction 21.7％ 16.3％ 10.8％ 19.9％ 11.9％ 5.7％ 11.5％

[0123] This invention utilizes typical coal types such as anthracite, bituminous coal, and lignite as raw materials, employs microwaves as a heat source, and uses concentrated nitric acid and dilute ammonia as activating agents to rapidly prepare high-adsorption-performance powdered activated carbon in a one-step process, while simultaneously recovering tail gas containing CO, H2, N2, NO2, and NO as main components. The main product, powdered activated carbon, has a specific surface area exceeding 1400 m². 2 / g, with methylene blue adsorption values ​​reaching 180-260 mg / g, and yields exceeding 50%.

[0124] Obviously, the above embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing coal-derived activated carbon, characterized in that, Includes the following steps: Step 1: After pre-treating the coal, perform ash removal treatment to obtain ash-removed coal powder; Step 2: Disperse the ash-removing coal powder, powdered activated carbon, and binder evenly in an aqueous solvent to obtain a mixture. Step 3: The mixture is activated by microwave heating, and acid and alkali solutions that have been preheated and vaporized by microwave are alternately injected during the microwave heating process. After the activation treatment is completed, gaseous components and solid components are obtained; wherein the obtained solid components are the coal-derived activated carbon. The microwave heating is carried out under vacuum conditions with an absolute pressure of 0.1~92kPa, and the microwave frequency of the microwave heating is 2450MHz, with a power of 0.2~10kW. Furthermore, during microwave heating, the activation temperature of the mixture is 450~650℃, and the activation time is 0.2~0.6h; The acid solution is nitric acid with a mass concentration of 50% to 68%; the alkaline solution is ammonia water with a mass concentration of 2% to 5%. Furthermore, when alternating between the acid and alkali solutions that have been preheated and vaporized by microwave, the acid and alkali solutions are injected continuously at intervals of 5 to 10 seconds.

2. The preparation method according to claim 1, characterized in that, The binder is coal tar, and the mass ratio of the ash-removing coal powder, powdered activated carbon, binder and water solvent is 10~30:1:1:2~5.

3. The preparation method according to claim 1, characterized in that, The ash-removed coal powder is obtained through the following steps: S1. After crushing the coal to 40-200 mesh, coal powder is obtained; S2. Mix hydrochloric acid, fluorosilicic acid and water in a mass ratio of 1:1:7 to obtain a descaling agent; S3. Add the coal powder to the ash removal agent, stir, filter and dry to obtain the ash removal coal powder; The liquid-to-solid mass ratio of the ash remover to the coal powder is 4~8:1; The stirring rate of the stirring process is 300~1000 r / min, and the stirring time is 0.5~1 h.

4. The preparation method according to claim 1, characterized in that, It also includes step 4, which involves initial cooling the gas phase component at a temperature of 60~75°C to obtain condensed coal tar and tail gas component A; The exhaust gas component A is subjected to final cooling at a temperature of 15~20°C to obtain condensed alkaline solution and exhaust gas component B.

5. A preparation apparatus for a method of preparing coal-derived activated carbon according to any one of claims 1-4, characterized in that, It includes an activation device, an activator supply device, an exhaust gas treatment device, and a microwave heater (1). The microwave heater (1) is used to provide microwave energy to the activation device; the activator supply device is connected to the feed end of the activation device, and the exhaust gas treatment device is connected to the discharge end of the activation device. The activator supply device includes: Acid supply device (2), which contains acid; Alkali supply device (3), which contains alkali solution; A spiral hollow tube A (4) is installed inside the microwave heater (1). One end of the tube is connected to the outlet end of the acid supply device (2) through a feed pipe A (5); the other end of the tube is connected to the inlet end of the activation device through a feed pipe B (6) to introduce the acid in the acid supply device (2) into the activation device. A spiral hollow tube B (7) is installed inside the microwave heater (1). One end of the tube is connected to the outlet end of the alkali supply device (3) through a feed pipe C (8); the other end of the tube is connected to the inlet end of the activation device through a feed pipe D (9) to introduce the alkali solution in the alkali supply device (3) into the activation device. Along its conveying direction, the conveying pipe A (5) is sequentially provided with a pump body A (10), a rotor flowmeter A (11), a solenoid valve A (12) and a syringe A (13). Along its conveying direction, the conveying pipe C (8) is sequentially equipped with a pump body B (14), a rotor flow meter B (15), a solenoid valve B (16) and a syringe B (17). The feed pipe B (6) is also equipped with a shut-off valve A (18), and the feed pipe D (9) is equipped with a shut-off valve B (19).

6. The preparation apparatus as described in claim 5, characterized in that, The activation device includes an activator (20), which is a cylindrical structure with open ends, and its interior is provided with a sealing plug A (21), a quartz glass plate A (22), a quartz glass plate B (23) and a sealing plug B (24) in sequence along its feeding direction. The quartz glass plate A (22) and the quartz glass plate B (23) are both vertically arranged inside the activator (20), and a cavity structure (A) is formed between the quartz glass plate A (22) and the quartz glass plate B (23). The cavity structure (A) is used to place the raw materials for the preparation of coal-based activated carbon. The quartz glass plate A (22) is provided with a through hole A, and the sealing plug A (21) is provided with a through hole B. The through hole B and the through hole A are located on the same horizontal plane. The feed pipe (25) is sequentially inserted into the through hole B and the through hole A. The discharge end of the feed pipe (25) is connected to the cavity structure (A). The feed end of the feed pipe (25) is connected to the discharge end of the conveying pipe B (6) and the conveying pipe D (9). It is used to inject acid and / or alkali through the through hole A into the cavity structure (A) in the activator (20). A discharge channel is formed between the quartz glass plate B (23) and the sealing plug B (24), and the quartz glass plate B (23) is provided with multiple through holes C, the sealing plug B (24) is provided with through holes D, the through holes D are connected to the feed end of the discharge pipe (26), and the discharge end of the discharge pipe (26) is connected to the exhaust gas treatment device.

7. The preparation apparatus according to claim 6, characterized in that, The exhaust gas treatment device includes: The primary cooler (27) is connected to the discharge end of the discharge pipe (26). The outlet temperature of the primary cooler (27) is 60~75℃, which is used to condense the coal tar in the tail gas. The final cooler (28) is connected to the outlet of the primary cooler (27) through the gas guide pipe (29). The outlet temperature of the final cooler (28) is 15~20℃. It is used to condense the ammonia water in the tail gas so that the condensed ammonia water can be returned to the alkaline solution supply device (3). A gas collection device (30) is connected to the outlet of the final cooler (28) and is used to collect the gas components in the remaining exhaust gas. A vacuum pump (31) is also provided on the gas guide pipe (29). The vacuum pump (31) is used to perform vacuuming to provide a vacuum environment for the activator (20) and to introduce the exhaust gas after the primary cooler (27) into the final cooler (28).

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