System and method for recycling VOCs-containing tail gas in sludge drying process of disc dryer

Abstract

The application discloses a sludge drying process VOCs-containing tail gas recycling system and method of a disc dryer, the system comprising a disc dryer, a cyclone separator, a cooling device, a combustion device, a circulating fan and a concentration instrument, the tail gas outlet of the disc dryer being connected with the cyclone separator, the gas phase outlet of the cyclone separator being communicated with the cooling device, the outlet of the cooling device being divided into two branches, the first branch being communicated with the air inlet of the disc dryer after passing through the circulating fan, the second branch being communicated with the combustion device, the outlet of the combustion device being communicated with the pipeline before the circulating fan, and the system further comprising a gas monitoring and control system.The system realizes real-time monitoring of VOCs concentration in tail gas and dynamic adjustment of system parameters, improves the operation efficiency and stability of the whole system, and is helpful to reduce energy consumption in the sludge drying process, reduce environmental pollution, improve the economic benefits of sludge treatment, and has remarkable environmental benefits and practical value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental protection and energy comprehensive utilization, and specifically relates to a system and method for efficient recycling of tail gas containing volatile organic compounds (VOCs) generated during the treatment of high-moisture-content sludge (moisture content of 60% to 80%) by a disc dryer. BACKGROUND

[0002] With the acceleration of urbanization and the continuous improvement of environmental protection requirements, sludge treatment has become a problem that needs to be solved. As a key equipment for sludge treatment, the disc dryer is widely used in various sludge treatment sites. Its unique working principle makes it have a significant advantage in treating high-moisture-content sludge.

[0003] The main structure of the disc dryer is composed of a cylindrical shell and a set of central penetrating discs. The set of discs are hollow structures, and a hot medium (such as steam or hot oil) flows through them, indirectly transferring heat to the sludge through the disc wall. The sludge passes through the narrow channel between the disc and the shell, receives heat energy from the disc, and thus evaporates water. The water vapor formed by the evaporation of sludge water gathers on the dome above the disc, and is then carried out of the dryer by the incoming air, achieving the drying treatment of the sludge. However, during the drying process, organic matter in the sludge is released as water evaporates, forming VOCs-containing contaminated gas.

[0004] Traditionally, these VOCs-containing tail gas is usually directly introduced into the boiler for combustion treatment to reduce its pollution to the environment. However, this method has certain defects: the tail gas itself is a kind of useful resource, and if it is directly burned and discharged, it is a waste of resources; at the same time, VOCs in the tail gas may not be completely burned in the combustion process, causing secondary pollution such as smoke and particulate matter, further affecting the environment.

[0005] In addition, with the increasing strictness of environmental regulations and the rise of energy prices, the traditional tail gas treatment method has been unable to meet the needs of modern sludge treatment. Therefore, it is particularly important to develop a technology that can efficiently recycle VOCs-containing tail gas while reducing resource waste and environmental pollution. SUMMARY

[0006] The present application proposes a system for efficient recycling of VOCs-containing tail gas during the sludge drying process of a disc dryer, which aims to achieve efficient recovery and utilization of tail gas, reduce VOCs emissions, improve resource utilization, reduce environmental pollution, and achieve double improvement of environmental friendliness and economic benefits through innovative technical means.

[0007] The technical solution of the present application is as follows:

[0008] The application discloses a system for recycling VOCs-containing tail gas in a sludge drying process of a disc dryer, which comprises a disc dryer, a cyclone separator, a cooling device, a combustion device, a circulating fan and a concentration instrument, wherein the tail gas outlet of the disc dryer is connected with the inlet of the cyclone separator, the solid phase outlet of the cyclone separator is communicated with the dried sludge outlet of the disc dryer, the gas phase outlet of the cyclone separator is communicated with the inlet of the cooling device, the outlet of the cooling device is divided into two branches, the first branch is communicated with the air inlet of the disc dryer after passing through the circulating fan, the second branch is communicated with the inlet of the combustion device, the outlet of the combustion device is divided into two passages, the first passage is communicated with the atmosphere, and the second passage is communicated with the first branch before the circulating fan, and the concentration instrument is arranged on the pipeline between the circulating fan and the disc dryer, and the system further comprises a gas monitoring and control system.

[0009] The system can form a closed loop circulation path, the VOCs-containing tail gas is introduced into the air inlet of the disc dryer after being cooled for recycling, the VOCs concentration is controlled through the combustion device, and the VOCs concentration of the tail gas after being treated and being introduced into the disc dryer (1) again is monitored by the concentration instrument to assist in adjusting system parameters.

[0010] Further, a pneumatic ball valve is arranged on the second branch between the cooling device and the combustion device.

[0011] Further, the gas monitoring and control system is communicated with the pipeline of the combustion device and the pneumatic ball valve respectively, and is used for monitoring the VOCs concentration of the tail gas at the corresponding positions.

[0012] Further, the disc dryer is provided with a sludge inlet and a dried sludge outlet, a hollow disc group is arranged in the disc dryer, and a hot medium inlet is arranged, hot medium flows through the disc group, and heat is transferred to the sludge. The sludge passes through between the disc group and the shell, evaporates water, and forms high-temperature tail gas containing VOCs.

[0013] Further, an air supplement inlet is arranged on the pipeline before the circulating fan.

[0014] Further, the gas monitoring and control system is electrically communicated with the combustion device, the cooling device, the pneumatic ball valve and the concentration instrument respectively.

[0015] Further, the gas monitoring and control system comprises a VOCs concentration monitor and an automatic control system, can monitor the VOCs concentration in the tail gas in real time, and dynamically adjusts the working parameters of the combustion device, the cooling device and the pneumatic ball valve according to the monitoring result.

[0016] Further, the condensate outlet of the cooling device is communicated with a sewage treatment system.

[0017] The application also provides a method for recycling VOCs-containing tail gas in a sludge drying process of a disc dryer.

[0018] The water-containing sludge enters the disc dryer through a sludge inlet and is subjected to sludge drying treatment under the action of hot medium steam. In the treatment process, VOCs-containing tail gas is generated. The tail gas enters a cyclone separator through a tail gas outlet, and dry sludge is preliminarily separated. Then, the temperature of the tail gas is reduced to about 30 DEG C by using a cooling device. Subsequently, the cooled tail gas is introduced into an air inlet of the disc dryer again through the first branch under the action of a circulating fan after being monitored and treated by a concentration instrument. At the same time, the VOCs concentration in the tail gas is detected in real time by a gas monitoring and control system and the concentration instrument. When the VOCs concentration is too high, the gas monitoring and control system is instructed to open a pneumatic ball valve. The tail gas passes through the second branch pipeline and the combustion intensity of a combustion device is adjusted in real time by the gas monitoring and control system to ensure that the VOCs concentration is always maintained within a safe and stable range. Part of the tail gas at the outlet of the combustion device is directly discharged into the air, and the other part is introduced into the air inlet of the disc dryer again after being monitored and treated by the concentration instrument under the action of the circulating fan, so that the VOCs-containing tail gas is efficiently managed and recycled.

[0019] In summary, the application provides an innovative recycling system and method for the VOCs-containing tail gas generated by the disc dryer when treating high-water-content sludge. The method collects the high-temperature VOCs-containing tail gas discharged by the disc dryer, preliminarily separates the dry sludge by using a cyclone separator, reduces the temperature of the tail gas to about 30 DEG C by using a cooling device, and then introduces the cooled tail gas into the air inlet of the disc dryer to replace part of the fresh air, so as to realize the recycling of resources. At the same time, a combustion device is provided in the system to automatically adjust the combustion intensity according to the VOCs concentration in the tail gas, so as to ensure that the VOCs concentration is always maintained within a safe and stable range, thereby effectively avoiding environmental pollution and safety hazards caused by VOCs enrichment. In addition, the application also integrates a gas monitoring and control system and a concentration instrument to realize real-time monitoring of the VOCs concentration in the tail gas and dynamic adjustment of system parameters, thereby improving the operation efficiency and stability of the entire system.

[0020] The implementation of the application not only helps to reduce energy consumption and environmental pollution in the sludge drying process, but also improves the economic benefits of sludge treatment, and has significant environmental benefits and practical value. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The figure is a schematic diagram of the process system and implementation method of the application.

[0022] In the diagram: 1. Disc dryer; 2. Cyclone separator; 3. Cooling device; 4. Pneumatic ball valve; 5. Gas monitoring and control system; 6. Combustion device; 7. Circulating fan; 8. Concentration meter. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] like Figure 1 As shown, the efficient recycling system for VOCs-containing tail gas during the sludge drying process of the disc dryer of the present invention mainly includes a disc dryer 1, a cyclone separator 2, a cooling device 3, a pneumatic ball valve 4, a gas monitoring and control system 5, a combustion device 6, a circulating fan 7, and a concentration meter 8. The tail gas outlet of the disc dryer 1 is connected to the inlet of the cyclone separator 2. The solid phase outlet of the cyclone separator 2 is connected to the dried sludge outlet of the disc dryer 1. The gas phase outlet of the cyclone separator 2 is connected to the inlet of the cooling device 3. The outlet of the cooling device 3 is divided into two branches. The first branch is connected to the air inlet of the disc dryer 1 after passing through the circulating fan 7. The second branch is connected to the inlet of the combustion device 6. The outlet of the combustion device 6 is divided into two passages. The first passage is connected to the atmosphere. The second passage is connected to the first branch before the circulating fan 7. A concentration meter 8 is also installed on the pipeline between the circulating fan 7 and the disc dryer 1. The tail gas recycling system also includes the gas monitoring and control system 5. A pneumatic ball valve 4 is also installed on the second branch between the cooling device 3 and the combustion device 6. An air supply inlet is also installed on the pipeline before the circulating fan 7.

[0025] The disc dryer 1 is equipped with a sludge inlet and a dried sludge outlet. Inside the disc dryer 1 is a hollow disc assembly with a heat medium inlet through which heat is transferred to the sludge. The sludge passes between the discs and the outer shell, evaporating moisture and forming high-temperature exhaust gas (80-90℃) containing VOCs. The flue gas velocity inside the disc dryer 1 is controlled within the range of 2-10 m / s to ensure efficient sludge drying and effective exhaust gas collection. The exhaust gas outlet of the disc dryer 1 is tightly connected to a cyclone separator 2 to prevent exhaust gas leakage.

[0026] The cyclone separator 2 adopts a sealed structure design for efficient collection of VOCs-containing tail gas discharged from the disc dryer 1, and can separate larger particulate matter in the tail gas discharged from the disc dryer 1 by using the principle of centrifugal force, preventing it from entering the subsequent device to cause blockage or affect the treatment effect, while also playing a role in preliminary purification of the tail gas. The cyclone separator 2 separates larger particulate matter by centrifugal force and transports the preliminarily treated tail gas to the cooling device 3 for pretreatment. The cyclone separator 2 is provided with a guide plate inside to optimize the flow path of the tail gas and improve the collection efficiency.

[0027] The cooling device 3 adopts efficient condensation technology to cool and treat the collected tail gas. By cooling, the high-temperature tail gas (80-90°C) is reduced to a suitable temperature (30°C), while condensate water and VOCs-rich tail gas are separated, achieving preliminary removal of VOCs in the tail gas, and the generated condensate is discharged to the sewage treatment system. The cooling device 3 is provided with a cooling medium circulation pipeline and a sewage collection device inside to ensure the cooling effect and effective collection of sewage. The condensate outlet of the cooling device 3 is in communication with the sewage treatment system, and the generated sewage is discharged to the sewage treatment system for further treatment to meet environmental protection standards.

[0028] The pneumatic ball valve 4 is located in the system pipeline and can quickly and accurately open or close the gas passage according to the instructions of the gas monitoring and control system 5, adjust the gas flow, cooperate with the combustion device 6, and ensure system safety.

[0029] The combustion device 6 is located in the circulation path and can automatically adjust the combustion intensity according to the feedback signal of the gas monitoring and control system 5 to ensure that the VOCs concentration always remains within the preset safety threshold. The combustion device 6 adopts efficient combustion technology and precise combustion control system for deep combustion treatment of the tail gas treated by the cooling device 3 to further remove VOCs in the tail gas and ensure that the tail gas meets environmental emission standards. By burning, the VOCs in the tail gas are deeply treated to ensure that harmful substances in the tail gas are effectively removed. The tail gas treated by the combustion device 6 is directly discharged into the air to meet environmental emission standards, and the other part is connected to the disc dryer 1 through the circulating fan 7 for recycling to reduce the consumption of fresh air and reduce tail gas emissions.

[0030] The gas monitoring and control system 5 is provided with a pipeline in communication with the combustion device 6 and the pneumatic ball valve 4, respectively, for monitoring the VOCs concentration of the tail gas at the corresponding position.

[0031] The gas monitoring and control system 5 includes a VOCs concentration monitor and an automatic control system, which can monitor the concentration of VOCs in the tail gas in real time and dynamically adjust the working parameters of the combustion device 6, the cooling device 3 and the pneumatic ball valve 4 according to the monitoring results. The gas monitoring and control system 5 is in electrical communication with the combustion device 6, the cooling device 3, the pneumatic ball valve 4 and the concentration monitor 8, respectively.

[0032] The gas monitoring and control system 5 monitors the VOCs concentration, temperature and other parameters in the tail gas in real time, and automatically adjusts the operating parameters of the combustion device 6, the cooling device 3 and the pneumatic ball valve 4 according to the monitoring results, so as to achieve the best effect of tail gas treatment. The gas monitoring and control system 5 also has an alarm function, which sends out an alarm and takes corresponding measures in time when the tail gas treatment effect is not up to standard. Through the precise control of the gas monitoring and control system 5, the stability and reliability of the tail gas treatment effect can be ensured.

[0033] The circulating fan 7 is used to send part of the tail gas treated by the combustion device 6 back to the disc dryer 1 for recycling. The circulating fan 7 has sufficient power and adjusting capacity, which can drive the tail gas to form a stable circulating flow in the system, ensuring the effective utilization of the tail gas and the effective control of VOCs. The operation of the circulating fan 7 is automatically adjusted by the gas monitoring and control system 5 according to the tail gas treatment effect and the demand of the disc dryer 1. Through the setting of the circulating fan 7, the consumption of fresh air can be reduced and the tail gas emission can be reduced, so as to realize the saving of resources and the protection of the environment.

[0034] The concentration monitor 8 is used to monitor the VOCs concentration of the treated tail gas when it is introduced into the disc dryer 1 again, which provides a basis for adjusting the system parameters and ensures the stable and efficient operation of the system. For example, when the concentration monitor 8 detects abnormal changes in the VOCs concentration during the recycling of the tail gas, the gas monitoring and control system 5 can adjust the working parameters of the combustion device 6, the cooling device 3 and other devices in time according to the data, so as to ensure the treatment effect of the system on the tail gas containing VOCs and the stability of the treatment environment in the disc dryer 1.

[0035] Based on the above-mentioned tail gas recycling method of the sludge drying process of the disc dryer containing VOCs tail gas recycling system, the process is as follows:

[0036] The aqueous sludge enters the disc dryer 1 through the sludge inlet, and is subjected to sludge drying treatment under the action of the hot medium steam. In the treatment process, tail gas containing VOCs is generated, which enters the cyclone separator 2 through the tail gas outlet, and the dry sludge is preliminarily separated. Then, the cooling device 3 is used to reduce the temperature of the tail gas to about 30℃, and then the cooled tail gas is introduced into the air inlet of the disc dryer 1 through the first branch under the action of the circulating fan 7 after being monitored and treated by the concentration instrument 8. At the same time, the VOCs concentration in the tail gas is detected in real time by the gas monitoring and control system 5 and the concentration instrument 8. When the VOCs concentration is too high, according to the instruction of the gas monitoring and control system 5, the pneumatic ball valve 4 is opened, the tail gas passes through the second branch pipeline, and the combustion intensity of the combustion device 6 is adjusted in real time by the gas monitoring and control system 5, so that the VOCs concentration is always maintained in a safe and stable range. A part of the tail gas at the outlet of the combustion device 6 is directly discharged into the air, and the other part is introduced into the air inlet of the disc dryer 1 after being monitored and treated by the concentration instrument 8 under the action of the circulating fan 7, so as to realize efficient management and recycling of the tail gas containing VOCs.

[0037] The process method includes the steps of starting the disc dryer, preliminary treatment of the tail gas, cooling the tail gas, tail gas control, deep combustion treatment, recycling of the tail gas, and VOCs concentration monitoring. By accurately controlling the tail gas recycling ratio and the operation of the combustion device, and combining with the VOCs concentration monitoring data, efficient management and utilization of the tail gas are realized.

[0038] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A system for recycling VOCs-containing tail gas in a sludge drying process of a disc dryer, characterized in that, The tail gas recycling system comprises a disc dryer (1), a cyclone separator (2), a cooling device (3), a combustion device (6), a circulating fan (7) and a concentration instrument (8), the tail gas outlet of the disc dryer (1) is connected with the inlet of the cyclone separator (2), the solid phase outlet of the cyclone separator (2) is communicated with the dry sludge outlet of the disc dryer (1), the gas phase outlet of the cyclone separator (2) is communicated with the inlet of the cooling device (3), the outlet of the cooling device (3) is divided into two branches, the first branch is communicated with the air inlet of the disc dryer (1) after passing through the circulating fan (7), the second branch is communicated with the inlet of the combustion device (6), the outlet of the combustion device (6) is divided into two passages, the first passage is communicated with the atmosphere, and the second passage is communicated with the first branch before the circulating fan (7), the concentration instrument (8) is further arranged on the pipeline between the circulating fan (7) and the disc dryer (1), and the tail gas recycling system further comprises a gas monitoring and control system (5). The pneumatic ball valve (4) is further arranged on the second branch between the cooling device (3) and the combustion device (6). The gas monitoring and control system (5) is electrically communicated with the combustion device (6), the cooling device (3), the pneumatic ball valve (4) and the concentration instrument (8) respectively. The concentration instrument (8) monitors the VOCs concentration in the tail gas in real time.

2. The VOCs-containing tail gas recycling system during the sludge drying process of a disc dryer according to claim 1, characterized in that, The gas monitoring and control system (5) is provided with a pipeline communicated with the combustion device (6) and the pneumatic ball valve (4) respectively, and is used for monitoring the VOCs concentration of the tail gas at the corresponding position.

3. The system according to claim 1, wherein the system further comprises a VOCs removal unit. The disc dryer (1) is provided with a sludge inlet and a dry sludge outlet, the disc dryer (1) is provided with a hollow disc group and a heat medium inlet, heat medium flows through the disc group, heat is transferred to the sludge, the sludge passes through between the disc group and the shell, evaporates water, and high-temperature tail gas containing VOCs is formed.

4. The system according to claim 2, wherein the system further comprises a VOCs removal unit. An air supplement inlet is further arranged on the pipeline before the circulating fan (7).

5. The system according to claim 2, wherein the system further comprises a VOCs removal unit. The gas monitoring and control system (5) comprises a VOCs concentration monitor and an automatic control system, can monitor the VOCs concentration in the tail gas in real time, and dynamically adjusts the working parameters of the combustion device (6), the cooling device (3) and the pneumatic ball valve (4) according to the monitoring result.

6. The system according to claim 2, wherein the system further comprises a VOCs removal unit. The condensate outlet of the cooling device (3) is communicated with a sewage treatment system.

7. A method for recycling VOCs-containing tail gas in a sludge drying process of a disc dryer, using the tail gas recycling system according to any one of claims 2-6, characterized in that, The process is as follows: The aqueous sludge enters the disc dryer (1) through the sludge inlet, and is subjected to sludge drying treatment under the action of the heat medium steam. In the treatment process, tail gas containing VOCs is generated, which enters the cyclone separator (2) through the tail gas outlet, and the dried sludge is preliminarily separated. Then, the cooling device (3) is used to reduce the temperature of the tail gas to about 30℃, and then the cooled tail gas is introduced into the air inlet of the disc dryer (1) through the first branch under the action of the circulating fan (7) after monitoring and treatment by the concentration instrument (8). At the same time, the VOCs concentration in the tail gas is detected in real time by the gas monitoring and control system (5) and the concentration instrument (8). When the VOCs concentration is too high, the pneumatic ball valve (4) is opened according to the instruction of the gas monitoring and control system (5), the tail gas passes through the second branch pipeline, and the combustion intensity of the combustion device (6) is adjusted in real time by the gas monitoring and control system (5) to ensure that the VOCs concentration is always maintained within a safe and stable range. Part of the tail gas at the outlet of the combustion device (6) is directly discharged into the air, and the other part is introduced into the air inlet of the disc dryer (1) after monitoring and treatment by the concentration instrument (8) under the action of the circulating fan (7), realizing efficient management and recycling of the tail gas containing VOCs.

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