Color-coated sheet VOC low-temperature catalytic combustion system and method

Abstract

The invention discloses a color-coated sheet VOC low-temperature catalytic combustion system and method, and the system comprises the following unit modules: a waste gas collection unit used for collecting VOC-containing waste gas volatilized in a color-coated sheet production process; the pretreatment module is connected with the waste gas collection unit and is used for pretreating the collected waste gas and removing impurities such as dust and liquid drops in the waste gas; the preheating device is connected with the pretreatment module and is used for heating the pretreated waste gas to a temperature interval suitable for catalytic reaction; the catalytic combustion reaction device is connected with the preheating device, is filled with a low-temperature catalyst and is used for promoting VOC (Volatile Organic Compounds) in the waste gas to generate a catalytic combustion reaction under a low-temperature condition; the heat recovery and cyclic utilization assembly is connected with the catalytic combustion reaction device and is used for recovering heat generated by reaction and feeding back part of the heat to the preheating device for preheating the waste gas; and the tail gas purification and emission unit is arranged behind the catalytic combustion reaction device and is used for deeply purifying the reacted tail gas to ensure that the tail gas is discharged after reaching the standard.

Description

Technical Field

[0001] The present invention relates to the technical field of waste gas treatment in color coated sheet production, and specifically relates to a low-temperature catalytic combustion system and method for VOC in color coated sheets. Background Art

[0002] In the current color coated sheet production industry, the tightening of environmental protection policies has made the treatment of volatile organic compound (VOC) waste gas a key link restricting industrial development. With the continuous increase in global attention to air quality, countries and regions have successively introduced increasingly strict environmental protection regulations, clearly restricting the emission concentration and total amount of VOCs in the color coated sheet production process.

[0003] Although the traditional activated carbon adsorption method can effectively adsorb VOCs in waste gas to a certain extent, it has many insurmountable drawbacks. The adsorption capacity of activated carbon is relatively limited. When treating high-concentration and large-flow waste gas, the adsorbent needs to be replaced frequently. This not only leads to a substantial increase in material costs, but also the regeneration process of activated carbon consumes a large amount of heat energy, further increasing the operating cost. More seriously, secondary pollution may occur during the regeneration process. For example, if the high-concentration VOC waste gas desorbed is not properly treated, it will cause greater harm to the environment.

[0004] As another common treatment method, the direct combustion method can completely decompose VOCs into carbon dioxide and water, but this method requires heating the waste gas to a high temperature of over 800°C. This not only consumes a large amount of fossil fuels such as natural gas and heavy oil, resulting in high operating costs, but also at high temperatures, nitrogen in the air is extremely easy to react with oxygen to generate harmful pollutants such as nitrogen oxides. These nitrogen oxides will not only exacerbate environmental problems such as acid rain and photochemical smog, but also pose a serious threat to human health.

[0005] In addition, some existing VOC treatment technologies show obvious insufficient adaptability in the face of complex and changeable production conditions and diverse waste gas components. There are differences in the production line processes and coating formulas of different color coated sheet production enterprises, resulting in large fluctuations in waste gas components and concentrations. Traditional treatment technologies are difficult to be flexibly adjusted according to the actual situation and cannot meet the personalized needs of each enterprise.

[0006] Based on this, the development of an efficient, energy-saving, highly adaptable and environmentally friendly VOC treatment technology has become an urgent need for the color coated sheet production industry to achieve green and sustainable development. Summary of the Invention

[0007] The object of the present invention is to provide a color-coated board VOC low-temperature catalytic combustion system and method. By burning and treating the VOC of the color-coated board, it reduces its environmental pollution. At the same time, through the catalytic reaction, the combustion efficiency is improved, and the harmless conversion effect and efficiency of the post-combustion gas are provided.

[0008] The object of the present invention is achieved by the following technical solutions:

[0009] A color-coated board VOC low-temperature catalytic combustion system includes the following main unit modules:

[0010] Exhaust gas collection unit: This unit is used to collect the VOC-containing exhaust gas volatilized during the production process of the color-coated board. It includes multiple suction hoods distributed at different workstations of the color-coated board production line. Each suction hood is connected to the exhaust gas aggregation pipeline through a pipeline, and the exhaust gas aggregation pipeline is connected to the pretreatment module. And this system can set suction hoods at different workstations, and can collect exhaust gas targeted according to the differences in exhaust gas generation amount and concentration at each workstation, improve the collection efficiency, and ensure that the exhaust gas collection efficiency is not less than 95%.

[0011] Pretreatment module: Connected to the exhaust gas collection unit, it pretreats the collected exhaust gas to remove impurities such as dust and liquid droplets. The pretreatment module is composed of a cyclone separator, a filtering device, and a condensation dehumidifier connected in sequence. The cyclone separator is used for preliminary separation of large particle impurities, and uses centrifugal force to separate heavier particles from the exhaust gas; the filtering device further removes fine dust to ensure that the dust content in the exhaust gas entering the subsequent equipment meets the requirements; the condensation dehumidifier reduces the humidity of the exhaust gas and reduces the impact of moisture on the subsequent catalytic reaction and equipment.

[0012] Preheating device: Connected to the pretreatment module, it heats the pretreated exhaust gas to a temperature range suitable for catalytic reaction. The present invention uses a plate heat exchanger as the preheating device, and uses the heat of the high-temperature tail gas after catalytic combustion reaction to preheat the low-temperature exhaust gas after pretreatment, and the heat exchange efficiency is not less than 85%. This design can effectively recover heat and reduce energy consumption.

[0013] Catalytic combustion reaction device: Connected to the preheating device, it is filled with a low-temperature catalyst inside. This low-temperature catalyst uses porous ceramics as a carrier and loads active components as transition metal oxides, such as copper oxide CuO, iron oxide Fe2O3, and cerium oxide CeO2. The catalytic combustion conversion rate of VOC is not less than 98% at 180-250°C. In the catalytic combustion reaction device, the VOC in the exhaust gas undergoes a catalytic combustion reaction with oxygen under the action of the low-temperature catalyst to generate carbon dioxide and water;

[0014] Among them, the transition metal oxides mentioned above are relatively low in cost and widely available, which can reduce the preparation cost of the catalyst to a certain extent. They can promote the reaction between VOC and oxygen through their own redox properties, thereby realizing the catalytic combustion of VOC; among them, cerium oxide has unique oxygen storage and release capabilities, which can regulate the supply of oxygen during the reaction and further improve the efficiency and stability of the catalytic reaction. The combination of cerium oxide and other transition metal oxides can produce a synergistic effect and significantly improve the overall performance of the catalyst.

[0015] Heat recovery and recycling components: connected to the catalytic combustion reaction device, recover the heat generated by the reaction, and feed part of the heat back to the preheating device for exhaust gas preheating. The components include a waste heat boiler and a thermal oil heat exchanger. The steam generated by the waste heat boiler can be used in other production links, such as heating, drying, etc. The thermal oil heat exchanger transfers heat to the thermal oil, which is used to preheat the exhaust gas or other process heating, realizing multi-level utilization of heat and improving energy utilization efficiency.

[0016] Exhaust gas purification and emission unit: It is installed after the catalytic combustion reaction device, and deeply purifies the exhaust gas after the reaction to ensure that it is discharged after meeting the standards. The unit includes an activated carbon adsorption device and an online monitor. The activated carbon adsorption device adsorbs the residual organic pollutants in the exhaust gas to further reduce the pollutant content in the exhaust gas; the online monitor monitors the exhaust emission indicators in real time, such as VOC concentration, carbon dioxide concentration, nitrogen oxide concentration, etc., to ensure that the exhaust emissions meet the relevant national and local standards.

[0017] Based on the above catalytic combustion system, the method for low-temperature catalytic combustion of VOC in color-coated plates of the present invention comprises the following steps:

[0018] Waste gas collection step: VOC-containing waste gas generated during the production of color-coated sheets is collected through the exhaust hood of the waste gas collection unit. According to the differences in the amount and concentration of waste gas generated at different workstations, the exhaust rate of each exhaust hood is adjusted to ensure that the waste gas collection efficiency is not less than 95%.

[0019] Pretreatment step: The collected exhaust gas is transported to the pretreatment module, and is sequentially processed by cyclone separation, filtration and condensation dehumidification to remove impurities such as dust and droplets in the exhaust gas and reduce the humidity of the exhaust gas.

[0020] Preheating step: The pretreated exhaust gas enters the preheating device and exchanges heat with the high-temperature exhaust gas after the catalytic combustion reaction to raise the temperature required for catalytic combustion. Through the efficient heat exchange of the plate heat exchanger, the heat of the exhaust gas is fully utilized to reduce additional energy consumption, and the heat exchange efficiency is not less than 85%.

[0021] Catalytic combustion step: the preheated exhaust gas is passed into the catalytic combustion reaction device. Under the action of the low-temperature catalyst, VOC and oxygen undergo a catalytic combustion reaction to generate carbon dioxide and water. During this step, the exhaust gas flow rate and reaction temperature are controlled to keep the temperature in the catalytic combustion reaction device stable at 180-250°C to ensure efficient conversion of VOC, so that the conversion rate is not less than 98%.

[0022] Heat recovery and utilization steps: The heat generated by the catalytic combustion reaction is recovered by using the heat recovery and recycling components. Part of the heat is transferred to the thermal oil through the thermal oil heat exchanger to preheat the exhaust gas; the other part of the heat is used to generate steam through the waste heat boiler to supply energy for other production links, thus realizing the recycling of heat.

[0023] Exhaust gas treatment and emission steps: The exhaust gas after catalytic combustion enters the exhaust gas purification and emission unit, where it is first treated with activated carbon adsorption to further remove residual organic pollutants; it is then monitored by an online monitor and discharged into the atmosphere after meeting the standards.

[0024] In summary, due to the adoption of the above technical solution, the present invention has the following advantages compared with the prior art:

[0025] 1. Efficient treatment of VOC waste gas: The present invention adopts low-temperature catalytic combustion technology and uses efficient low-temperature catalysts to achieve efficient conversion of VOC at a relatively low temperature, with a conversion rate of not less than 98%, effectively reducing VOC pollution to the environment;

[0026] 2. Energy saving and consumption reduction: The heat of high-temperature tail gas after catalytic combustion reaction is recovered through plate heat exchanger for waste gas preheating, and the waste heat boiler and thermal oil heat exchanger are used to realize multi-stage recycling of heat, which greatly reduces the energy consumption in the treatment process and improves the energy utilization efficiency. The heat exchange efficiency is not less than 85%;

[0027] 3. Reduce secondary pollution: The pretreatment module effectively removes dust and droplets in the exhaust gas, avoiding damage to the catalyst and subsequent equipment; the activated carbon adsorption device and online monitoring instrument in the exhaust gas purification and emission unit ensure that the exhaust gas meets the emission standards, reducing the generation of secondary pollutants;

[0028] 4. High system stability: By controlling the exhaust gas flow and reaction temperature, the temperature in the catalytic combustion reaction device is kept stable within an appropriate range, ensuring the stable operation of the system and the continuous and efficient treatment of VOCs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of a unit module of the VOC low-temperature catalytic combustion system and method of the color-coated plate of the present invention. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0031] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and should not be construed as indicating or implying relative importance.

[0032] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] The specific implementation manner is as Figure 1 shown:

[0034] System operation:

[0035] 1. Exhaust gas collection: During the production process of color-coated plates, according to the exhaust gas generation situation at different workstations, adjust the extraction rate of each suction hood so that the exhaust gas can be collected into the exhaust gas aggregation pipeline in a timely and efficient manner;

[0036] 2. Pretreatment: The collected exhaust gas enters the pretreatment module. First, it is preliminarily separated by a cyclone separator to remove large particle impurities; then it passes through a filtering device to further filter fine dust; finally, it passes through a condensation dehumidifier to reduce the humidity of the exhaust gas and prepare for the subsequent catalytic combustion reaction;

[0037] 3. Preheating: The pretreated exhaust gas enters a plate heat exchanger and exchanges heat with the high-temperature tail gas after the catalytic combustion reaction, and the temperature rises to the temperature range suitable for the catalytic reaction;

[0038] During the heat exchange process, it is necessary to ensure that the heat exchange efficiency is not less than 85%;

[0039] 4. Catalytic combustion: The preheated waste gas is introduced into the catalytic combustion reaction device. Under the action of a low-temperature catalyst, the VOC reacts with oxygen in a catalytic combustion reaction. By adjusting the waste gas flow rate and reaction temperature, the temperature inside the reaction device is stably maintained at 180 - 250 °C to ensure a high conversion rate of VOC of not less than 98%;

[0040] 5. Heat recovery and utilization: The heat generated by the catalytic combustion reaction is recovered through the heat recovery and recycling components. The waste heat boiler uses the heat to generate steam, which can be used in other production processes; the heat transfer oil heat exchanger transfers the heat to the heat transfer oil, and the heat transfer oil is used to preheat the waste gas or for other process heating;

[0041] 6. Tail gas treatment and emission: The tail gas after catalytic combustion enters the tail gas purification and emission unit. First, it passes through an activated carbon adsorption device to adsorb residual organic pollutants, and then the tail gas emission indicators are monitored in real time through an on-line monitor. And only when the tail gas emission indicators meet the relevant national and local standards, the tail gas is discharged into the atmosphere.

[0042] System maintenance:

[0043] Regularly check and maintain the system, including checking the operating status of each device, the connection of pipelines, the activity of the catalyst, etc. Replace the consumables such as ineffective filter materials and activated carbon in a timely manner to ensure the normal operation and treatment effect of the system.

[0045] Example 1:

[0046] In a medium-sized color-coated board production enterprise, the production line of this enterprise generates more than 5000 cubic meters of waste gas containing VOC every day, and the main components are toluene and xylene. The low-temperature catalytic combustion system of the present invention is adopted. After running for a period of time and detecting, the waste gas collection efficiency is stably at 96%. After pretreatment and preheating, it enters the catalytic combustion reaction device. At 180 - 250 °C, the VOC conversion rate reaches 98.5%. Under the effective operation of the heat recovery system, the heat exchange efficiency reaches 86%. The steam generated by the waste heat meets the needs of some drying processes of the enterprise, and all indicators of the tail gas after treatment are far lower than the national emission standards.

[0047] Example 2:

[0048] Before a large color-coated board factory introduced this system, especially with its complex production line, large amount of waste gas generated and complex composition. In addition to common aromatic hydrocarbons, there was also a small amount of halogenated hydrocarbons generated, resulting in relatively serious pollution. At the same time, its purification process was complex and the cost was high. After the system was introduced and put into operation, the waste gas collection efficiency was maintained between 95.5 - 95.8%. The pretreatment effectively removed impurities. In the catalytic combustion stage, under the control of temperature and flow rate, the average VOC conversion rate could reach 98.2%, and the heat exchange efficiency was 85.5%. The recovered heat was used to preheat the waste gas and other production links. The tail gas was adsorbed by activated carbon and monitored, and the emissions fully met the standards.

[0049] Comparison of test data:

[0050] Select the traditional direct combustion method and the system of the present invention to further compare under the same waste gas treatment volume and composition conditions: The traditional direct combustion method has a large fuel consumption. It consumes 0.5 cubic meters of natural gas to treat each cubic meter of waste gas. The nitrogen oxide content in the treated tail gas reaches 80 mg / m 3 ; while the system of the present invention only needs to consume a small amount of electric energy for the operation of equipment such as fans, and the nitrogen oxide in the tail gas is almost zero emission.

[0051] In terms of the VOC removal rate, although the traditional direct combustion method can reach 95%, the system of the present invention can achieve a conversion rate of more than 98% at low temperatures, fully demonstrating the significant advantages of the system of the present invention in energy conservation, environmental protection and efficient treatment.

[0052] The embodiments described above are only used to illustrate the technical ideas and characteristics of the present invention. The purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The scope of the patent adoption of the present invention cannot be limited only by these embodiments. That is, any equivalent changes or modifications made according to the spirit disclosed by the present invention still fall within the scope of the patent of the present invention.

Claims

1. A color-coated board VOC low-temperature catalytic combustion system, characterized in that, Includes the following unit modules: Waste gas collection unit, used to collect VOC-containing waste gas emitted during the production process of color-coated sheets; A pre-treatment module, connected to the exhaust gas collection unit, pre-treats the collected exhaust gas to remove impurities such as dust and liquid droplets therein; The preheating device is connected to the pretreatment module to heat the pretreated exhaust gas to a temperature range suitable for the catalytic reaction; The catalytic combustion reaction device is connected to the preheating device and is filled with a low-temperature catalyst to promote the catalytic combustion reaction of VOC in the exhaust gas under low-temperature conditions; The heat recovery and recycling component is connected to the catalytic combustion reaction device to recover the heat generated by the reaction and feed part of the heat back to the preheating device for exhaust gas preheating; The exhaust gas purification and emission unit is installed after the catalytic combustion reaction device to deeply purify the exhaust gas after the reaction to ensure that it is discharged after meeting the standards.

2. The VOC low-temperature catalytic combustion system for color-coated plates according to claim 1, characterized in that: The exhaust gas collection unit comprises a plurality of exhaust hoods distributed at different workstations of the color-coated plate production line, each exhaust hood is connected to an exhaust gas collection pipe through a pipe, and the exhaust gas collection pipe is connected to a pretreatment module.

3. A VOC low-temperature catalytic combustion system for color-coated plates according to claim 1, characterized in that: The pretreatment module is composed of a cyclone separator, a filter device and a condensation dehumidifier connected in sequence. The cyclone separator is used to initially separate large particle impurities, the filter device further removes fine dust, and the condensation dehumidifier reduces the humidity of the exhaust gas.

4. A VOC low-temperature catalytic combustion system for color-coated plates according to claim 1, characterized in that: The preheating device adopts a plate heat exchanger, and utilizes the heat of the high-temperature tail gas after the catalytic combustion reaction to preheat the pretreated low-temperature exhaust gas, and the heat exchange efficiency is not less than 85%.

5. A VOC low-temperature catalytic combustion system for color-coated plates according to claim 1, characterized in that: The low-temperature catalyst in the catalytic combustion reaction device uses porous ceramics as a carrier, and the loaded active group is a metal oxide. The catalytic combustion conversion rate of the catalyst for VOC at 180-250°C is not less than 98%.

6. The VOC low-temperature catalytic combustion system for color-coated plates according to claim 1, characterized in that: The heat recovery and recycling component includes a waste heat boiler and a thermal oil heat exchanger. The steam generated by the waste heat boiler can be used in other production links. The thermal oil heat exchanger transfers heat to the thermal oil, which is used to preheat exhaust gas or other process heating.

7. A VOC low-temperature catalytic combustion system for color-coated plates according to claim 1, characterized in that: The exhaust gas purification and emission unit includes an activated carbon adsorption device and an online monitor. The activated carbon adsorption device adsorbs residual organic pollutants in the exhaust gas, and the online monitor monitors the exhaust gas emission indicators in real time to ensure compliance with emission standards.

8. A method for low-temperature catalytic combustion of VOCs in color-coated plates based on the system described in any one of claims 1-7, characterized in that, The following steps are involved: Waste gas collection step: VOC-containing waste gas generated during the production of color-coated sheets is collected through the exhaust hood of the waste gas collection unit; Pretreatment step: The collected exhaust gas is transported to the pretreatment module and sequentially subjected to cyclone separation, filtration and condensation dehumidification treatment; Preheating step: The pretreated exhaust gas enters the preheating device and undergoes heat exchange with the high-temperature exhaust gas after the catalytic combustion reaction to raise the temperature to the required temperature for catalytic combustion; Catalytic combustion step: the preheated exhaust gas is passed into the catalytic combustion reaction device. Under the action of the low-temperature catalyst, the VOC and oxygen undergo a catalytic combustion reaction to generate carbon dioxide and water; Heat recovery and utilization step: Use heat recovery and recycling components to recover the heat generated by the catalytic combustion reaction, part of which is used to preheat the exhaust gas, and the other part is used to supply energy for other production links; Tail gas treatment and emission steps: The tail gas after catalytic combustion enters the tail gas purification and emission unit, is first treated by activated carbon adsorption, and then discharged to the atmosphere after passing the on-line monitor and meeting the standards.

9. A method for low-temperature catalytic combustion of VOCs in a color-coated plate according to claim 8, characterized in that: In the waste gas collection step, according to the differences in the waste gas generation volume and concentration at different workstations, by adjusting the air extraction rate of each suction hood, ensure that the waste gas collection efficiency is not less than 95%.

10. A method for low-temperature catalytic combustion of VOCs in a color-coated board according to claim 8, characterized in that: In the catalytic combustion step, by controlling the waste gas flow rate and reaction temperature, keep the temperature in the catalytic combustion reaction device stable between 180 - 250 °C to ensure the efficient conversion of VOC.

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