Electroplating waste gas treatment method

Abstract

The invention discloses an electroplating waste gas treatment method. The electroplating waste gas treatment method comprises the following steps: S1, collecting and conveying waste gas; s2, a pre-treatment stage: pre-treating the acid waste gas and the particulate matters through a high-efficiency turbulent flow spray tower; s3, a core treatment stage: under the working condition that the VOCs with medium and high concentrations are greater than 1.5 g / m < 3 >, the waste gas is thoroughly decomposed into CO2 and H2O at a high temperature (greater than or equal to 800 DEG C) based on a heat accumulating type thermal incinerator; in the working condition of low-concentration VOCs, a third-stage spray tower is additionally arranged based on the efficient turbulence spray tower in the step S2 to absorb trace VOCs; s4, a post-treatment stage: capturing trace particles or aerosol possibly escaping from the core treatment unit through a fine filter; and S5, an air inducing and discharging stage. According to the electroplating waste gas treatment method, acid waste gas and chromic acid mist are treated through the efficient turbulent flow spray tower, the gas-liquid contact area and the mass transfer efficiency are increased through the turbulent flow design, and compared with a traditional spray tower, the removal rate of acidic substances can be remarkably increased.

Description

Technical Field

[0001] This invention relates to the field of electroplating waste gas treatment technology, and in particular to a method for treating electroplating waste gas. Background Technology

[0002] Electroplating is an indispensable and fundamental link in the manufacturing industry, but it is also a heavily polluting industry. During its production process, especially in pretreatment (degreasing, pickling), electroplating tanks, and post-treatment, a large amount of complex waste gas pollutants are generated. These waste gases can be mainly divided into two categories: one is acidic waste gases, such as hydrochloric acid mist, sulfuric acid mist, chromic acid mist, and hydrogen cyanide; the other is volatile organic compounds (VOCs), originating from the volatilization of degreasing agents, solvents, and additives. If these waste gases are emitted directly without treatment, they will cause serious pollution to the atmospheric environment and harm human health. For example, acidic gases can lead to acid rain and corrode buildings; chromic acid mist and hydrogen cyanide are highly toxic and carcinogenic; VOCs are important precursors to PM2.5 and ozone, and some VOCs themselves are toxic and have a foul odor. Therefore, efficient purification of electroplating waste gases to meet emission standards is an environmental responsibility that electroplating companies must fulfill and a key focus of current environmental policies.

[0003] Currently, various technologies are used to treat electroplating waste gas, but all have certain limitations: alkaline spray absorption has limited efficiency in treating chromic acid mist, which is poorly soluble in water, is basically ineffective against VOCs, and cannot treat hydrogen cyanide. Activated carbon adsorption, when treating electroplating waste gas with high humidity, is quickly rendered ineffective and clogged by oil mist and dust, requiring frequent replacement and incurring high operating and maintenance costs. Thermal incineration / catalytic combustion is problematic for complex electroplating waste gas compositions, as halogens (such as hydrogen chloride) and sulfides can poison and deactivate the catalyst, and the combustion process may generate more dangerous secondary pollutants such as dioxins and NOx.

[0004] In summary, existing electroplating waste gas treatment technologies either suffer from low treatment efficiency and narrow applicability, or have problems such as high operating costs and the potential for secondary pollution or secondary hazards. Summary of the Invention

[0005] Therefore, it is necessary to provide a new electroplating waste gas treatment method to address the technical problems of low treatment efficiency and high operating costs of existing electroplating waste gas treatment methods.

[0006] A method for treating electroplating waste gas, comprising the following steps:

[0007] S1. Waste gas collection and transportation;

[0008] S2, Pretreatment stage: A high-efficiency turbulent spray tower is used to pretreat acidic waste gas and particulate matter;

[0009] S3, Core Treatment Stage: For medium to high concentrations of VOCs, >1.5g / m³ 3 In operation: Based on the regenerative thermal incinerator, the exhaust gas is completely decomposed into CO2 and H2O at high temperature (≥800℃); In low concentration VOCs operation: Based on the high efficiency turbulent spray tower in step S2, a third-stage spray tower is added to absorb trace amounts of VOCs.

[0010] S4. In the post-processing stage, a fine filter is used to capture trace particles or aerosols that may escape from the core processing unit.

[0011] S5. In the exhaust and emission stage, a corrosion-resistant centrifugal fan is selected and placed at the end of the treatment system to keep the entire system under negative pressure and prevent exhaust gas leakage.

[0012] In one embodiment, step S1 above includes the following steps: effectively capturing and collecting the waste gas generated by each plating tank through a gas collection hood to the main pipeline.

[0013] In one embodiment, the wind speed on the surface of the air collection hood in step S1 above is ≥0.5m / s; the design wind speed of the main duct is 8~12m / s.

[0014] In one embodiment, the gas collection hood in step S1 above uses a top suction hood, a side suction hood, etc. to effectively seal and collect the plating tank, ensuring a capture efficiency of >90%; the main pipe is made of PP or FRP material to ensure corrosion resistance; the main pipe adopts a variable diameter design to ensure the air volume balance of each branch pipe.

[0015] In one embodiment, step S2 described above includes the following steps:

[0016] S21, primary spraying, removes most of the acidic gases through alkaline washing and neutralization;

[0017] S22, secondary spraying, uses oxidative washing to decompose cyanide and reduce chromic acid mist;

[0018] S23. Demisting to remove liquid droplets entrained in the exhaust gas and protect the fans and valves of the subsequent regenerative thermal incinerator.

[0019] In one embodiment, the primary spraying in step S21 above uses a circulating NaOH solution to effectively neutralize strong acids such as HCl and H2SO4. The dosage is automatically controlled by a pH meter to maintain optimal neutralization efficiency. In step S22, the secondary spraying targets chromic acid mist, HCN, etc., by adding a special oxidant, sodium hypochlorite, to oxidize them into less toxic substances, such as Cr. 6+ Reduced to Cr 3+HCN is oxidized into CO2 and N2; in step S23, a PP material demister is installed at the top of the spray tower to remove liquid droplets entrained in the exhaust gas, in preparation for the subsequent core treatment unit, and to prevent moisture from affecting the process, thereby completing the demisting process.

[0020] In one embodiment, the alkaline washing absorbent in step S21 above is a 5%–10% NaOH solution; the liquid-to-gas ratio is set to 2–3 L / m³. 3 pH control is achieved by automatically adding alkali solution through a pH meter to maintain the pH of the circulating liquid at 10-12.

[0021] In one embodiment, the oxidizing absorbent in step S22 above is a sodium hypochlorite solution (effective chlorine concentration 3-5%); ORP control is achieved by automatically adding oxidant through an ORP meter to maintain the ORP value at +400mV to +500mV.

[0022] In one embodiment, the demisting process in step S23 above uses either a cyclone demister or a wire mesh demister to ensure a demisting efficiency greater than 99%.

[0023] In one embodiment, step S3 above includes the following steps:

[0024] S31. Based on a regenerative thermal incinerator, it completely decomposes all VOCs and residual trace amounts of malodorous organic matter.

[0025] S32. The high-temperature flue gas (~150°C) from the outlet of the regenerative thermal incinerator in step S31 is rapidly cooled by a quench tower to avoid the resynthesis of dioxins.

[0026] S33, the post-absorption tower absorbs acidic secondary pollutants generated by the regenerative thermal incinerator.

[0027] In one embodiment, the combustion temperature in step S31 is set to 820°C to 850°C; the residence time is set to ≥1.0 second to ensure a heat recovery efficiency of ≥95%.

[0028] In one embodiment, the cooling method in step S32 above is spray water mist evaporation cooling; the outlet temperature is rapidly cooled to <70°C.

[0029] In one embodiment, the absorbent in step S33 above is a 5% NaOH solution.

[0030] In one embodiment, in step S3 above, a heat exchanger is added before the inlet of the regenerative thermal incinerator to preheat the inlet exhaust gas with the high-temperature flue gas purified by the regenerative thermal incinerator, which significantly reduces gas consumption and improves the energy-saving effect of the production process; an intelligent control system with automatic over-temperature alarm and bypass setting is adopted to monitor the combustion chamber temperature, and the bypass valve is automatically opened when the temperature is abnormally high to ensure safety.

[0031] In one embodiment, step S3 above adds a third stage of spraying to the two-stage spraying of the high-efficiency turbulent spray tower. The third-stage spray tower uses a special organic solvent or a low-volatility absorbent to circulate and absorb trace amounts of VOCs and odors that are difficult to be treated by alkaline solutions. The absorbent is replaced periodically.

[0032] In one embodiment, the fine filter in step S4 above uses an activated carbon adsorption bed to ensure that odors and trace pollutants are completely removed. The activated carbon box is designed with two sets in parallel, one for use and one for backup, which can be switched online for replacement and regeneration. In this step, the activated carbon is a backup measure rather than the main treatment unit, so it has a long lifespan, low replacement frequency, and controllable operating costs.

[0033] In one embodiment, the corrosion-resistant centrifugal fan exhaust stack in step S5 above is equipped with an online monitoring system to monitor process parameters such as pH, flow rate, and VOCs concentration. The data is connected to the environmental protection department and the central control room to achieve real-time monitoring.

[0034] The aforementioned electroplating waste gas treatment method utilizes a high-efficiency turbulent spray tower to treat acidic waste gas and chromic acid mist. The turbulent design increases the gas-liquid contact area and mass transfer efficiency, significantly improving the removal rate of acidic substances compared to traditional spray towers, typically reaching over 95%. Furthermore, the high-efficiency turbulent spray tower removes acidic components that could corrode subsequent core treatment equipment, especially the regenerative thermal incinerator, and removes most particulate matter, protecting downstream equipment. Step S3 involves dual-path selective treatment for different VOC concentrations. For high-VOC waste gas, the regenerative thermal incinerator, operating at ≥800℃, can remove almost all types of VOCs. The VOCs and odor substances are completely oxidized and decomposed into CO2 and H2O, with a removal rate generally as high as 98%-99% or more. For low-VOC exhaust gas, a special organic solvent absorbent is used in the third-stage spray tower to treat certain types of VOCs, thereby improving the adaptability and flexibility of the electroplating exhaust gas treatment process and reducing the operating load of the regenerative thermal incinerator. In addition, the fine filter in the post-treatment stage can effectively capture trace particles, aerosols, oil fumes, etc. that may escape from the front-end treatment, and can further adsorb residual trace VOCs and odors to ensure that the final emission gas is odorless and consistently meets the standards. Detailed Implementation

[0035] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0037] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0038] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0039] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0040] This invention discloses a method for treating electroplating waste gas, which includes the following steps:

[0041] S1. Waste gas collection and transportation;

[0042] S2, Pretreatment stage: A high-efficiency turbulent spray tower is used to pretreat acidic waste gas and particulate matter;

[0043] S3, Core Treatment Stage: For medium to high concentrations of VOCs, >1.5g / m³ 3 In operation: Based on the regenerative thermal incinerator, the exhaust gas is completely decomposed into CO2 and H2O at high temperature (≥800℃); In low concentration VOCs operation: Based on the high efficiency turbulent spray tower in step S2, a third-stage spray tower is added to absorb trace amounts of VOCs.

[0044] S4. In the post-processing stage, a fine filter is used to capture trace particles or aerosols that may escape from the core processing unit.

[0045] S5. In the exhaust and emission stage, a corrosion-resistant centrifugal fan is selected and placed at the end of the treatment system to keep the entire system under negative pressure and prevent exhaust gas leakage.

[0046] Furthermore, step S1 above includes the following steps: effectively capturing and collecting the waste gas generated by each plating tank through a gas collection hood to the main pipeline.

[0047] Specifically, the wind speed on the surface of the air collection hood in step S1 is ≥0.5m / s; the design wind speed of the main duct is 8~12m / s.

[0048] Specifically, in one embodiment, the above step S1 uses a top suction hood, a side suction hood, etc. to effectively seal and collect the plating tank, ensuring a capture efficiency of >90%; the main pipe is made of PP or FRP material to ensure corrosion resistance; the main pipe adopts a variable diameter design to ensure the air volume balance of each branch pipe.

[0049] Furthermore, step S2 above includes the following steps:

[0050] S21, primary spraying, removes most of the acidic gases through alkaline washing and neutralization;

[0051] S22, secondary spraying, uses oxidative washing to decompose cyanide and reduce chromic acid mist;

[0052] S23. Demisting to remove liquid droplets entrained in the exhaust gas and protect the fans and valves of the subsequent regenerative thermal incinerator.

[0053] Specifically, in one embodiment, the primary spraying in step S21 uses a circulating NaOH solution to effectively neutralize strong acids such as HCl and H2SO4. The dosage is automatically controlled by a pH meter to maintain optimal neutralization efficiency. In step S22, the secondary spraying targets chromic acid mist, HCN, etc., by adding a special oxidant, sodium hypochlorite, to oxidize them into less toxic substances, such as Cr. 6+ Reduced to Cr 3+ HCN is oxidized into CO2 and N2; in step S23, a PP material demister is installed at the top of the spray tower to remove liquid droplets entrained in the exhaust gas, in preparation for the subsequent core treatment unit, and to prevent moisture from affecting the process, thereby completing the demisting process.

[0054] Specifically, the alkaline washing absorbent in step S21 uses a 5%–10% NaOH solution; the liquid-to-gas ratio is set to 2–3 L / m³. 3 pH control is achieved by automatically adding alkali solution through a pH meter to maintain the pH of the circulating liquid at 10-12.

[0055] Specifically, the oxidizing absorbent in step S22 is a sodium hypochlorite solution (effective chlorine concentration 3-5%); ORP control is achieved by automatically adding oxidant through an ORP meter to maintain the ORP value at +400mV to +500mV.

[0056] Specifically, the demisting process in step S23 uses either a cyclone demister or a wire mesh demister to ensure a demisting efficiency greater than 99%.

[0057] Furthermore, step S3 above includes the following steps:

[0058] S31. Based on a regenerative thermal incinerator, it completely decomposes all VOCs and residual trace amounts of malodorous organic matter.

[0059] S32. The high-temperature flue gas (~150°C) from the outlet of the regenerative thermal incinerator in step S31 is rapidly cooled by a quench tower to avoid the resynthesis of dioxins.

[0060] S33, the post-absorption tower absorbs acidic secondary pollutants generated by the regenerative thermal incinerator.

[0061] Specifically, the combustion temperature in step S31 is set to 820℃~850℃; the residence time is set to ≥1.0 second to ensure a heat recovery efficiency of ≥95%.

[0062] Specifically, the cooling method in step S32 is spray water mist evaporation cooling; the outlet temperature is rapidly cooled to <70℃.

[0063] Specifically, the absorption solution in step S33 is a 5% NaOH solution.

[0064] Specifically, in one embodiment, in step S3 above, a heat exchanger is added before the inlet of the regenerative thermal incinerator to preheat the inlet exhaust gas with the high-temperature flue gas purified by the regenerative thermal incinerator, which significantly reduces gas consumption and improves the energy-saving effect of the production process; an intelligent control system with automatic over-temperature alarm and bypass setting is adopted to monitor the combustion chamber temperature, and the bypass valve is automatically opened when the temperature is abnormally high to ensure safety.

[0065] Specifically, in one embodiment, step S3 above adds a third stage of spraying to the two-stage spraying of the high-efficiency turbulent spray tower. The third-stage spray tower uses a special organic solvent or a low-volatility absorbent to circulate and absorb trace amounts of VOCs and odors that are difficult to be treated by alkaline solutions, and the absorbent is replaced periodically.

[0066] Specifically, in one embodiment, the fine filter in step S4 uses an activated carbon adsorption bed to ensure that odors and trace pollutants are completely removed. The activated carbon box is designed with two sets in parallel, one for use and one for backup, which can be switched online for replacement and regeneration. In this step, the activated carbon is a backup measure rather than the main treatment unit, so it has a long lifespan, low replacement frequency, and controllable operating costs.

[0067] Specifically, in one embodiment, the corrosion-resistant centrifugal fan exhaust stack in step S5 above is equipped with an online monitoring system to monitor process parameters such as pH, flow rate, and VOCs concentration. The data is connected to the environmental protection department and the central control room to achieve real-time monitoring.

[0068] In summary, the electroplating waste gas treatment method disclosed in this invention treats acidic waste gas and chromic acid mist using a high-efficiency turbulent spray tower. The turbulent design increases the gas-liquid contact area and mass transfer efficiency, significantly improving the removal rate of acidic substances compared to traditional spray towers, typically reaching over 95%. Furthermore, the high-efficiency turbulent spray tower removes acidic components that could corrode subsequent core treatment equipment, especially the regenerative thermal incinerator, and removes most particulate matter, protecting downstream equipment. Step S3 involves dual-path selective treatment for different VOC concentrations; for high-VOC waste gas, the regenerative thermal incinerator, operating at ≥800℃, can almost completely remove VOCs. All types of VOCs and odor substances are completely oxidized and decomposed into CO2 and H2O, with removal rates generally reaching over 98%-99%. For low-VOC exhaust gases, a special organic solvent absorbent is used in the third-stage spray tower to specifically treat certain types of VOCs, thereby improving the adaptability and flexibility of the electroplating exhaust gas treatment process and reducing the operating load of the regenerative thermal incinerator. In addition, the fine filter in the post-treatment stage can effectively capture trace particles, aerosols, fumes, etc. that may escape during the front-end treatment, and can further adsorb residual trace VOCs and odors to ensure that the final exhaust gas is odorless and consistently meets the standards.

[0069] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for treating electroplating waste gas, characterized in that, Includes the following steps: S1. Waste gas collection and transportation; S2. Pretreatment stage: A high-efficiency turbulent spray tower is used to pretreat acidic waste gas and particulate matter; S3, Core Treatment Stage: For medium to high concentrations of VOCs, >1.5g / m³ 3 In operation: Based on the regenerative thermal incinerator, the exhaust gas is completely decomposed into CO2 and H2O at high temperature (≥800℃); In low concentration VOCs operation: Based on the high efficiency turbulent spray tower in step S2, a third-stage spray tower is added to absorb trace amounts of VOCs. S4. In the post-processing stage, a fine filter is used to capture trace particles or aerosols that may escape from the core processing unit. S5. In the exhaust and emission stage, a corrosion-resistant centrifugal fan is selected and placed at the end of the treatment system to keep the entire system under negative pressure and prevent exhaust gas leakage.

2. The electroplating waste gas treatment method according to claim 1, characterized in that, Step S1 includes the following steps: effectively capturing and collecting the waste gas generated by each plating tank through a gas collection hood to the main pipeline.

3. The electroplating waste gas treatment method according to claim 2, characterized in that, Step S2 includes the following steps: S21, primary spraying, removes most of the acidic gases through alkaline washing and neutralization; S22, secondary spraying, uses oxidative washing to decompose cyanide and reduce chromic acid mist; S23. Demisting to remove liquid droplets entrained in the exhaust gas and protect the fans and valves of the subsequent regenerative thermal incinerator.

4. The electroplating waste gas treatment method according to claim 3, characterized in that, In step S21, the primary spraying uses a circulating NaOH solution to effectively neutralize strong acids such as HCl and H2SO4. The dosage is automatically controlled by a pH meter to maintain optimal neutralization efficiency. In step S22, the secondary spraying targets chromic acid mist and HCN, adding a special oxidant, sodium hypochlorite, to oxidize them into less toxic substances, such as Cr. 6+ Reduced to Cr 3+ HCN is oxidized into CO2 and N2; in step S23, a PP material demister is installed at the top of the spray tower to remove liquid droplets entrained in the exhaust gas, in preparation for the subsequent core treatment unit, and to prevent moisture from affecting the process, thereby completing the demisting process.

5. The electroplating waste gas treatment method according to claim 4, characterized in that, Step S3 includes the following steps: S31. Based on a regenerative thermal incinerator, it completely decomposes all VOCs and residual trace amounts of malodorous organic matter. S32. The high-temperature flue gas (~150°C) from the outlet of the regenerative thermal incinerator in step S31 is rapidly cooled by a quench tower to avoid the resynthesis of dioxins. S33, the post-absorption tower absorbs acidic secondary pollutants generated by the regenerative thermal incinerator.

6. The electroplating waste gas treatment method according to claim 5, characterized in that, The combustion temperature in step S31 is set to 820℃~850℃; the residence time is set to ≥1.0 second to ensure a heat recovery efficiency of ≥95%.

7. The electroplating waste gas treatment method according to claim 6, characterized in that, The cooling method in step S32 is spray water mist evaporation cooling; the outlet temperature is rapidly cooled to <70℃.

8. The electroplating waste gas treatment method according to claim 7, characterized in that, The absorbent in step S33 is a 5% NaOH solution.

9. The electroplating waste gas treatment method according to claim 8, characterized in that, The fine filter in step S4 uses an activated carbon adsorption bed to ensure that odors and trace pollutants are completely removed. The activated carbon box is designed with two sets in parallel, one for use and one for backup, which can be switched online for replacement and regeneration. In this step, the activated carbon is a backup measure rather than the main treatment unit, so it has a long lifespan, low replacement frequency, and controllable operating costs.

10. The method for treating electroplating waste gas according to claim 9, characterized in that, In step S5, an online monitoring system is installed on the exhaust stack of the corrosion-resistant centrifugal fan to monitor process parameters such as pH, flow rate, and VOC concentration. The data is connected to the environmental protection department and the central control room to achieve real-time monitoring.