A method and system for treating VOCs in a high-temperature carbonization process of a tunnel kiln

Abstract

The application discloses a kind of tunnel kiln high-temperature carbonization process VOC treatment method and system, comprising the following steps: step 1, VOC collection device is set in tunnel kiln heating section, and volatile organic compounds volatilized by material are captured;Step 2, the VOC collected is divided into two ways by fan: the first way is introduced into tunnel kiln high-temperature section, and is oxidized in ≥800 ℃ environment;The second way is introduced into the initial region of tunnel kiln cooling section, and is oxidized again in ≥800 ℃ environment;Step 3, part of the tail gas after high-temperature section treatment is recycled to heating section to form internal circulation airflow, and the remaining tail gas is introduced into cooling section for secondary treatment;Step 4, the tail gas after cooling section treatment is discharged through chimney to meet the standard.Through VOC collection device, VOC volatilized in heating section is efficiently captured, and the treatment mode of collection-subsection oxidation-internal circulation is used, VOC decomposition is realized using high-temperature section and cooling section (≥800 ℃) double high-temperature environment, VOC emission is greatly reduced, and strict environmental protection requirements are met.

Description

Technical Field

[0001] This invention belongs to the field of VOC treatment technology in tunnel kilns, and relates to a method and system for VOC treatment during the high-temperature carbonization process in tunnel kilns. Background Technology

[0002] Tunnel kilns are key equipment for the high-temperature carbonization of industrial products such as ceramics, refractory materials, and activated carbon. Due to their advantages of continuous and automated production, they are widely used in manufacturing. During production, materials sequentially undergo heating, high-temperature, and cooling stages within the kiln, achieving carbonization through complex physicochemical reactions.

[0003] However, with the expansion of industrial scale and stricter environmental protection requirements, the emission of volatile organic compounds (VOCs) during the carbonization process in tunnel kilns has become increasingly serious. Especially during the heating stage at the feed end, a large amount of organic components in the material volatilize after heating, forming a large amount of VOCs containing harmful substances such as benzene compounds and aldehydes. Currently, existing processes generally lack effective treatment methods, resulting in these pollutants being directly released into the atmosphere. Summary of the Invention

[0004] The purpose of this invention is to provide a VOC treatment method and system for the high-temperature carbonization process in a tunnel kiln, which aims to efficiently treat VOCs emitted during the heating phase while balancing environmental protection and product quality.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for VOC control during high-temperature carbonization in a tunnel kiln includes the following steps:

[0007] Step 1: Install a VOC collection device in the heating section of the tunnel kiln to capture the volatile organic compounds volatilized from the material;

[0008] Step 2: The collected VOCs are split into two streams using a fan:

[0009] The first route is introduced into the high-temperature section of the tunnel kiln for oxidation treatment at an environment of ≥800℃.

[0010] The second route is introduced into the initial area of ​​the cooling section of the tunnel kiln, where a secondary oxidation treatment is carried out at an environment of ≥800℃.

[0011] Step 3: Part of the exhaust gas after treatment in the high-temperature section is circulated to the heating section to form an internal circulation airflow, and the remaining exhaust gas is introduced into the cooling section for secondary treatment.

[0012] Step 4: The exhaust gas treated in the cooling section is discharged through the chimney in compliance with standards.

[0013] As a further improvement of one embodiment of the present invention, in step 2, the amount of VOC introduced into the high-temperature section is dynamically controlled by a regulating valve to ensure that the gas composition in the high-temperature section is stable and does not affect product quality, and the introduction position is close to the inlet end of the high-temperature section.

[0014] As a further improvement of one embodiment of the present invention, the VOC collection device in step 2 includes multiple air inlets and corresponding regulating valves, and the opening degree of each regulating valve is dynamically adjusted according to the VOC volatilization amount in different temperature zones of the heating section.

[0015] As a further improvement of one embodiment of the present invention, the tail gas internal circulation in step 3 is specifically as follows: the tail gas after high temperature section treatment is returned to the heating section through kiln airflow circulation, forming a closed-loop degradation path.

[0016] As a further improvement of one embodiment of the present invention, the length of the cooling section is greater than 10 meters, providing sufficient space and time for the oxidation of VOCs.

[0017] As a further improvement of one embodiment of the present invention, in step 2, the VOC introduced into the cooling section needs to be supplemented with oxygen, and the oxygen concentration is adjusted to a sufficient oxidation level by a makeup air fan.

[0018] A VOC treatment system employing the above method, wherein the VOC collection device includes a plurality of air inlets and regulating valves, with one regulating valve corresponding to one air inlet;

[0019] The first induced draft fan transports some of the VOCs to the high-temperature section;

[0020] The second induced draft fan transports the remaining VOCs to the cooling section;

[0021] The high-temperature section outlet is equipped with several air outlets and regulating valves. One regulating valve corresponds to one air outlet to control the exhaust gas recirculation ratio.

[0022] The cooling section outlet is equipped with an induced draft fan and a chimney.

[0023] As a further improvement of one embodiment of the present invention, the air inlet of the VOC collection device is distributed along the kiln body in the heating section, and the opening degree of the regulating valve is positively correlated with the VOC volatilization amount in the corresponding temperature range.

[0024] As a further improvement of one embodiment of the present invention, the outlet of the high-temperature section is located close to the inlet of the heating section, and the single-point VOC introduction is limited by the regulating valve to not exceed 5% of the total gas flow of the high-temperature section.

[0025] As a further improvement of one embodiment of the present invention, the VOC treatment system includes an oxygen content monitoring module, which adjusts the amount of oxygen delivered by the make-up air fan to the cooling section in real time to maintain an oxygen concentration ≥8%.

[0026] The above technical solution has the following beneficial effects:

[0027] 1. The VOC collection device efficiently captures VOCs volatilized in the heating stage and adopts a treatment mode of collection-segmented oxidation-internal circulation. It utilizes the dual high-temperature environment of the high-temperature stage and the cooling stage (≥800℃) to decompose VOCs, significantly reducing VOC emissions and meeting stringent environmental protection requirements.

[0028] 2. Through precise debugging and location optimization, pollutants are efficiently treated while minimizing their impact on product quality, achieving a win-win situation for both environmental protection and production efficiency;

[0029] 3. The internal exhaust gas recirculation mechanism effectively recovers heat, improves energy utilization efficiency, and reduces enterprise production costs;

[0030] 4. The process and equipment have a simple structure, requiring no large-scale modification of existing tunnel kilns, making it easy for enterprises to implement and promote quickly, and resulting in significant economic and environmental benefits. Attached Figure Description

[0031] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0032] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0033] Figure 1 This is a schematic diagram of the structure provided by the present invention.

[0034] Figure 2 This is a schematic diagram of the process provided by the present invention. Detailed Implementation

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0037] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention. Example

[0038] See Figure 1 As shown, a VOC treatment system employing the above method comprises a tunnel kiln heating section 1 (hereinafter referred to as the heating section), a tunnel kiln high-temperature section 2 (hereinafter referred to as the high-temperature section), and a tunnel kiln cooling section 3 (hereinafter referred to as the cooling section). In the heating section, due to the heating of the material, the internal organic components continuously volatilize, forming a large amount of volatile organic compounds (VOCs) containing harmful substances such as benzene series compounds and aldehydes. This is the main VOC generation area. To prevent VOCs from escaping from the kiln head, an air curtain fan 4 is installed at the kiln head. A VOC collection device is also installed in the heating zone to capture the volatilized VOCs. A treatment mode of collection-segmented oxidation-internal circulation is adopted, utilizing the dual-stage high-temperature environment (≥800℃) of the high-temperature section and the cooling section to achieve VOC decomposition, significantly reducing VOC emissions.

[0039] like Figure 1 As shown, the VOC collection device includes a first induced draft fan 21 and a second induced draft fan 30. The first induced draft fan 21 is used to transport a portion of the VOCs to the high-temperature section, and the second induced draft fan 30 is used to transport the remaining VOCs to the cooling section. Specifically:

[0040] The air inlet of the first induced draft fan 21 is connected to the main air intake pipe A, which forms several air inlets in the heating section through the air intake branch pipes A. In this embodiment, there are eight air intake branch pipes A, forming air inlets 5-12 in the heating section; each air intake branch pipe A is equipped with a regulating valve, and the air inlets correspond one-to-one with the regulating valves, forming regulating valves 13-20.

[0041] The outlet of the first induced draft fan 21 is connected to the main exhaust pipe A, which forms several exhaust outlets in the high-temperature section through the exhaust branch pipes A. In this embodiment, there are four exhaust branch pipes A, forming exhaust outlets 26-29 in the high-temperature section; each exhaust branch pipe A is equipped with a regulating valve, and each exhaust outlet corresponds to a regulating valve, forming regulating valves 22-25.

[0042] The air inlet of the second induced draft fan 30 is connected to one end of the main air intake pipe B, and the other end of the main air intake pipe B is connected to the main air intake pipe A. The air outlet of the second induced draft fan 30 is connected to one end of the main exhaust pipe B, and the other end of the main exhaust pipe B is connected to the initial area of ​​the cooling section, forming an exhaust outlet 31 in the cooling section. In order to ensure sufficient oxygen supply for VOC oxidation in the cooling section, the main exhaust pipe B is connected to the make-up air fan 32.

[0043] A chimney 36 and an induced draft fan 35 are installed at the tail outlet of the cooling section. The air inlet of the induced draft fan 35 is connected to the main air inlet pipe C. The main air inlet pipe C forms an air inlet 33 on the cooling section, and a regulating valve 34 is installed on the main air inlet pipe C. The air outlet of the induced draft fan 35 is connected to one end of the main air outlet pipe C, and the other end of the main air outlet pipe C is connected to the chimney 36.

[0044] In this embodiment, the air inlets 5-12 of the VOC collection device are distributed along the kiln body in the heating section, and the opening degree of the regulating valves 13-20 is positively correlated with the VOC volatilization amount in the corresponding temperature range. Therefore, a VOC monitor is installed inside the kiln body in the heating section. The VOC monitor transmits the detected VOC content data to the tunnel kiln controller, which can adjust the opening degree of the regulating valves 13-20 in real time based on the VOC content data to balance VOC treatment and product quality.

[0045] The product is mainly formed in the high-temperature section, which has strict temperature requirements. The temperature of the flue gas containing VOCs in the heating section is not high. Introducing too much VOCs will certainly reduce the pressure on VOC treatment, but the quality of the finished product will be affected. Introducing too little VOCs is not conducive to VOC treatment, but the quality of the finished product can be guaranteed. Here, it is necessary to adjust the air volume to evaluate the quality of the product.

[0046] Therefore, the outlet of the high-temperature section, 26-29, is located close to the inlet of the heating section, and the VOC introduction at a single point is limited by the regulating valve 22-25 to not exceed 5% of the total gas flow of the high-temperature section, so as to ensure that the introduction of balanced VOCs into the high-temperature section does not affect the product quality.

[0047] Since the exhaust gas after high-temperature treatment is partially circulated to the heating section to form an internal circulation airflow, the exhaust gas circulation ratio can also be controlled by regulating valves 22-25.

[0048] In this embodiment, to ensure sufficient VOC oxidation, the VOC treatment system includes an oxygen content monitoring module to adjust the amount of oxygen delivered by the make-up air fan 32 to the cooling section in real time, maintaining an oxygen concentration ≥8%.

[0049] like Figure 2 As shown, a VOC treatment method during high-temperature carbonization in a tunnel kiln, employing the aforementioned VOC treatment system, includes the following steps:

[0050] Step 1: Install a VOC collection device in the heating section of the tunnel kiln to capture the volatile organic compounds volatilized from the material, thus solving the problem of not treating VOCs in the heating section in traditional processes.

[0051] Step 2: The collected VOCs are split into two streams by the first exhaust fan 21 and the second exhaust fan 30:

[0052] The first route is introduced into the high-temperature section of the tunnel kiln for oxidation treatment at an environment of ≥800℃.

[0053] The second route is introduced into the initial area of ​​the cooling section of the tunnel kiln, where a secondary oxidation treatment is carried out at an environment of ≥800℃.

[0054] Step 3: Part of the exhaust gas after treatment in the high-temperature section is circulated to the heating section to form an internal circulation airflow, and the remaining exhaust gas is introduced into the cooling section for secondary treatment.

[0055] Step 4: The exhaust gas treated in the cooling section is discharged through the chimney in compliance with standards.

[0056] In step 2, the amount of VOC introduced into the high-temperature section is dynamically controlled by regulating valves 22-25. These regulating valves can be electric or pneumatic, and possess precise flow control capabilities. By monitoring the gas composition and process parameters in the high-temperature section in real time, the valve opening is automatically adjusted to ensure stable gas composition and prevent product quality from being affected by improper VOC introduction. Furthermore, the introduction location is close to the inlet of the high-temperature section, facilitating the rapid participation of VOCs in the oxidation reaction.

[0057] The VOC collection device is equipped with multiple air inlets 5-12 and corresponding regulating valves 13-18. The air inlets can be evenly or non-uniformly distributed in the heating section according to the VOC volatilization pattern, and their shape can be circular or square. Each regulating valve 13-18 dynamically adjusts its opening according to the VOC volatilization amount in different temperature zones of the heating section. When the VOC volatilization amount in a certain zone increases, the corresponding regulating valve opens wider, and vice versa.

[0058] Step 3, the internal circulation of exhaust gas, specifically involves the exhaust gas treated in the high-temperature section being returned to the heating section through the airflow circulation within the kiln, forming a "treatment-circulation" closed loop. This allows residual VOCs in the exhaust gas to participate in the reaction again, improving the treatment efficiency of VOCs. At the same time, it reduces external emissions while recovering heat, thereby improving energy utilization.

[0059] In this embodiment, the length of the cooling section is greater than 10 meters. Such a long cooling section provides sufficient space and time for VOCs to undergo oxidation, ensuring that VOCs can fully undergo secondary oxidation reactions in this area, further reducing their concentration and improving the treatment effect.

[0060] During the VOC treatment process in the cooling stage, oxygen must be supplemented to ensure sufficient oxidation. Therefore, a makeup air fan 32 is installed. Different types of makeup air fans, such as centrifugal and axial flow fans, can be used, as long as they can meet the functional requirements for adjusting oxygen concentration. Through the makeup air fan 32, the amount of oxygen entering the cooling stage can be precisely adjusted according to the oxidation requirements of VOCs at different stages, regulating the oxygen concentration to a sufficient oxidation level. Simultaneously, an oxygen concentration sensor can be installed in the cooling stage to monitor the oxygen concentration in real time and feed the data back to the control system. The control system then automatically adjusts the operating parameters of the makeup air fan 32 to achieve precise control of the oxygen concentration, ensuring the high efficiency and stability of VOC treatment.

[0061] This invention employs a unique VOC treatment mode, efficiently capturing VOCs volatilized during the heating phase using a VOC collection device. The inlet layout of this collection device can be flexibly designed according to the space of the heating phase, such as in a matrix or ring distribution, to achieve comprehensive capture. The collected VOCs are treated using a collection-segmented oxidation-internal circulation mode, utilizing the dual-stage high-temperature environment of the high-temperature section and the cooling section (≥800℃) to fully decompose the VOCs and significantly reduce VOC emissions.

[0062] During implementation, by precisely adjusting the opening of each regulating valve and optimizing the VOC introduction location, pollutants are efficiently treated while minimizing their impact on product quality, achieving a win-win situation for both environmental protection and production efficiency. The exhaust gas internal recirculation mechanism effectively recovers heat, improves energy utilization efficiency, and reduces enterprise production costs.

[0063] Furthermore, the process and equipment structure of this invention are simple. Existing tunnel kilns only need to be equipped with VOC collection devices, regulating valves, circulation pipelines and other components, without large-scale modifications. Enterprises can implement and promote it quickly, which reduces the initial investment and can quickly meet the stringent environmental protection requirements, resulting in significant economic and environmental benefits.

[0064] Obviously, the embodiments described above are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0065] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0066] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for VOC treatment during high-temperature carbonization in a tunnel kiln, characterized in that, Includes the following steps: Step 1: Install a VOC collection device in the heating section of the tunnel kiln to capture the volatile organic compounds volatilized from the material; the VOC collection device includes multiple air inlets and corresponding regulating valves, and the opening degree of each regulating valve is dynamically adjusted according to the amount of VOC volatilization in different temperature zones of the heating section. Step 2: The collected VOCs are split into two streams using a fan: The first route is introduced into the high-temperature section of the tunnel kiln for oxidation treatment at an environment of ≥800℃. The amount of VOC introduced into the high-temperature section is dynamically controlled by a regulating valve to ensure that the gas composition in the high-temperature section is stable and does not affect product quality, and the introduction position is close to the inlet end of the high-temperature section. The second route introduces the initial area of ​​the cooling section of the tunnel kiln, where it undergoes secondary oxidation treatment at an environment of ≥800℃. During this process, the VOCs introduced into the cooling section require oxygen supplementation, and the oxygen concentration is adjusted to a sufficient oxidation level by using a makeup air fan. Step 3: The exhaust gas after high-temperature treatment is partially circulated to the heating section to form an internal circulation airflow. The internal circulation of the exhaust gas is specifically as follows: the exhaust gas after high-temperature treatment is returned to the heating section through the airflow in the kiln, forming a closed-loop degradation path; the remaining exhaust gas is introduced into the cooling section for secondary treatment; the length of the cooling section is greater than 10 meters, providing sufficient space and time for the oxidation of VOCs. Step 4: The exhaust gas treated in the cooling section is discharged through the chimney in compliance with standards.

2. A VOC treatment system employing the method of claim 1, characterized in that, The VOC collection device includes multiple air inlets and corresponding regulating valves; The first induced draft fan (21) transports some of the VOCs to the high-temperature section; The second induced draft fan (30) delivers the remaining VOCs to the cooling section; The high-temperature section outlet is equipped with several air outlets and corresponding regulating valves to control the exhaust gas recirculation ratio. The cooling section outlet is equipped with an induced draft fan (35) and a chimney (36).

3. The VOC treatment system according to claim 2, characterized in that, The air inlets of the VOC collection device are distributed along the kiln body in the heating section, and the opening degree of the regulating valve is positively correlated with the VOC volatilization amount in the corresponding temperature range.

4. The VOC treatment system according to claim 2, characterized in that, The outlet of the high-temperature section is located close to the inlet of the heating section, and the VOC introduction at a single point is limited to no more than 5% of the total gas flow of the high-temperature section by the regulating valve corresponding to the outlet.

5. The VOC treatment system according to claim 2, characterized in that, The VOC treatment system includes an oxygen content monitoring module, which adjusts the amount of oxygen delivered by the make-up air fan (32) to the cooling section in real time to maintain an oxygen concentration of ≥8%.

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