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

Abstract

The invention discloses a system and method for recycling VOCs-containing tail gas in the sludge drying process of a disc dryer, the system comprises the disc dryer, a cyclone separator, a cooling device, a combustion device, a circulating fan and a concentration meter, a tail gas outlet of the disc dryer is connected with the cyclone separator, a gas phase outlet of the cyclone separator is communicated with the cooling device, and a gas phase outlet of the combustion device is communicated with the circulating fan. An outlet of the cooling device is divided into two branches, the first branch is communicated with an air inlet of the disc drying machine after passing through the circulating fan, the second branch is communicated with the combustion device, an outlet of the combustion device is communicated with a pipeline in front of the circulating fan, and the system further comprises a gas monitoring and control system. According to the system, the concentration of VOCs in tail gas is monitored in real time, system parameters are dynamically adjusted, and the operation efficiency and stability of the whole system are improved. The energy consumption in the sludge drying process is reduced, the environmental pollution is reduced, the economic benefit of sludge treatment is improved, and the method has remarkable environmental benefit and practical value.

Description

Technical Field

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

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

[0003] The main structure of the disc dryer consists of a cylindrical shell and a group of discs with a central penetration. The discs are hollow in structure, and the heat medium (such as steam or hot oil) flows through them, transferring the heat indirectly to the sludge through the disc wall. The sludge passes through the narrow channel between the disc and the shell, receiving heat energy from the disc, thereby evaporating the water. The water vapor formed by the evaporation of the sludge water gathers in the dome above the disc, and is then carried out of the dryer by the incoming air to achieve the drying of the sludge. However, during the drying process, the organic matter in the sludge will be released as the water evaporates, forming polluted gas containing VOCs.

[0004] Traditionally, these exhaust gases containing VOCs are usually directly introduced into boilers for combustion treatment to reduce their pollution to the environment. However, this method has certain defects: the exhaust gas itself is also a usable resource, and it is a waste of resources if it is directly burned and discharged; at the same time, the VOCs in the exhaust gas may not be completely burned during the combustion process, resulting in secondary pollution, such as smoke, particulate matter, etc., which further affects the environment.

[0005] In addition, with increasingly stringent environmental regulations and rising energy prices, traditional tail gas treatment methods can no longer 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 of the invention

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

[0007] The technical solution of the present invention is as follows: A system for recycling tail gas containing VOCs during the sludge drying process of a disc dryer comprises a disc dryer, a cyclone separator, a cooling device, a combustion device, a circulating fan and a concentration meter, wherein the tail gas outlet of the disc dryer is connected to the inlet of the cyclone separator, the solid phase outlet of the cyclone separator is connected to the dried sludge outlet of the disc dryer, the gas phase outlet of the cyclone separator is connected to the inlet of the cooling device, the outlet of the cooling device is divided into two branches, the first branch is connected to the air inlet of the disc dryer after passing through the circulating fan, and the second branch is connected to the inlet of the combustion device, the outlet of the combustion device is divided into two passages, the first passage is connected to the atmosphere, and the second passage is connected to the first branch in front of the circulating fan, a concentration meter is also arranged on the pipeline between the circulating fan and the disc dryer, and the tail gas recycling system also includes a gas monitoring and control system.

[0008] The system can form a closed-loop circulation path, cool the VOCs-containing exhaust gas and introduce it into the air inlet of the disc dryer for recycling, while controlling the VOCs concentration through the combustion device, and using a concentration meter to monitor the VOCs concentration when the treated exhaust gas is reintroduced into the disc dryer (1) to assist in adjusting system parameters.

[0009] Furthermore, a pneumatic ball valve is provided on the second branch between the cooling device and the combustion device.

[0010] Furthermore, the gas monitoring and control system is provided with pipelines connected to the combustion device and the pneumatic ball valve, respectively, for monitoring the VOCs concentration of the exhaust gas at the corresponding position.

[0011] Furthermore, the disc dryer is provided with a sludge inlet and a dry sludge outlet. A hollow disc group is provided inside the disc dryer, and a heat medium inlet is provided. The heat medium flows through the disc group and transfers heat to the sludge. The sludge passes between the disc group and the shell, evaporating water and forming high-temperature tail gas containing VOCs.

[0012] Furthermore, an air supplement inlet is provided on the pipeline in front of the circulating fan.

[0013] Furthermore, the gas monitoring and control system is electrically connected to the combustion device, the cooling device, the pneumatic ball valve and the concentration meter respectively.

[0014] Furthermore, the gas monitoring and control system includes a VOCs concentration monitor and an automatic control system, which can monitor the concentration of VOCs in the exhaust gas in real time and dynamically adjust the working parameters of the combustion device, cooling device and pneumatic ball valve according to the monitoring results.

[0015] Furthermore, the condensate outlet of the cooling device is connected to a sewage treatment system.

[0016] The present invention also proposes a method for recycling tail gas containing VOCs in the process of sludge drying of a disc dryer, which is carried out by using the tail gas recycling system as described above, and the process is as follows: The water-containing sludge enters the disc dryer through the sludge inlet, and is dried under the action of the hot medium steam. During the treatment process, tail gas containing VOCs is generated. The tail gas enters the cyclone separator through the tail gas outlet to initially separate the dry sludge. The tail gas temperature is then reduced to about 30°C by a cooling device. The cooled tail gas is then reintroduced into the air inlet of the disc dryer through the first branch and monitored and treated by a concentration meter under the action of a circulating fan. At the same time, the VOCs concentration in the tail gas is detected in real time through the gas monitoring and control system and the concentration meter. When the VOCs concentration is detected to be too high, the pneumatic ball valve is opened according to the instruction of the gas monitoring and control system, and the tail gas passes through the second branch pipeline. The combustion intensity of the combustion device is adjusted in real time through 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 reintroduced into the air inlet of the disc dryer after being monitored and treated by a concentration meter under the action of a circulating fan, thereby realizing efficient management and recycling of the tail gas containing VOCs.

[0017] In summary, the present invention proposes an innovative recycling system and method for the problem of 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, first preliminarily separates the dry sludge through a cyclone separator, and then uses a cooling device to reduce the tail gas temperature to about 30°C, and then reintroduces the cooled tail gas into the air inlet of the dryer to replace part of the fresh air, thereby realizing the recycling of resources. At the same time, the system is equipped with a combustion device to automatically adjust the combustion intensity according to the VOCs concentration in the tail gas, ensuring that the VOCs concentration is always maintained within a safe and stable range, effectively avoiding environmental pollution and safety hazards caused by VOCs enrichment. In addition, the present invention also integrates a gas monitoring and control system and a concentration meter, realizing real-time monitoring of the VOCs concentration in the tail gas and dynamic adjustment of system parameters, thereby improving the operating efficiency and stability of the entire system.

[0018] The implementation of the present invention not only helps to reduce energy consumption in the sludge drying process and reduce environmental pollution, but also improves the economic benefits of sludge treatment, and has significant environmental benefits and practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the process system and implementation method of the present invention; In the figure: 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 DESCRIPTION

[0020] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0021] like Figure 1 As shown, the high-efficiency recycling system of VOCs-containing tail gas in 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 dry 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, and 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, and the second passage is connected to the first branch before the circulating fan 7. A concentration meter 8 is also arranged on the pipeline between the circulating fan 7 and the disc dryer 1, and the tail gas recycling system also includes a gas monitoring and control system 5. A pneumatic ball valve 4 is also provided on the second branch between the cooling device 3 and the combustion device 6. An air supplement inlet is also provided on the pipeline in front of the circulating fan 7.

[0022] The disc dryer 1 is provided with a sludge inlet and a dry sludge outlet. A hollow disc group is provided inside the disc dryer 1, and a heat medium inlet is provided, through which the heat medium flows to transfer heat to the sludge. The sludge passes between the disc and the outer shell, evaporates water, and forms a high-temperature tail gas (80-90°C) containing VOCs. The flue gas flow rate in the disc dryer 1 is controlled within the range of 2 to 10 m / s to ensure the drying efficiency of the sludge and the effective collection of the tail gas. The tail gas outlet of the disc dryer 1 is closely connected to the cyclone separator 2 to prevent tail gas leakage.

[0023] The cyclone separator 2 adopts a sealed structure design, which is used to efficiently collect the VOCs-containing tail gas discharged from the disc dryer 1, and can use the centrifugal force principle to separate the larger particulate matter in the tail gas discharged from the disc dryer 1 to prevent it from entering the subsequent device to cause blockage or affect the treatment effect, and at the same time play 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. A guide plate is provided inside the cyclone separator 2 to optimize the flow path of the tail gas and improve the collection efficiency.

[0024] The cooling device 3 adopts efficient condensation technology to cool the collected tail gas. Through cooling, the high-temperature tail gas (80-90°C) is reduced to a suitable temperature (30°C), and the condensed water and VOCs-rich tail gas are separated at the same time, so as to achieve the preliminary removal of VOCs in the tail gas, and the generated condensate is discharged to the sewage treatment system. A cooling medium circulation pipeline and a sewage collection device are provided inside the cooling device 3 to ensure the cooling effect and the effective collection of sewage. The condensate outlet of the cooling device 3 is connected to the sewage treatment system, and the generated sewage is discharged to the sewage treatment system for further treatment to meet environmental protection standards.

[0025] The pneumatic ball valve 4 is located in the system pipeline, and can quickly and accurately open or close the gas channel according to the instructions of the gas monitoring and control system 5, adjust the gas flow, cooperate with the combustion device 6 and ensure the safety of the system.

[0026] 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 is always maintained within the preset safety threshold. The combustion device 6 adopts efficient combustion technology and precise combustion control system, which is used to perform deep combustion treatment on the tail gas treated by the cooling device 3 to further remove the VOCs in the tail gas and ensure that the tail gas meets environmental emission standards. Through combustion, the VOCs in the tail gas are deeply treated to ensure that the harmful substances in the tail gas are effectively removed. A part of the tail gas treated by the combustion device 6 is directly discharged into the air to meet the environmental emission standards; 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.

[0027] The gas monitoring and control system 5 is provided with pipelines connected to the combustion device 6 and the pneumatic ball valve 4, respectively, for monitoring the VOCs concentration of the tail gas at the corresponding position.

[0028] 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 exhaust 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 electrically connected to the combustion device 6, the cooling device 3, the pneumatic ball valve 4 and the concentration meter 8 respectively.

[0029] 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 to achieve the best effect of tail gas treatment. The gas monitoring and control system 5 also has an alarm function. When the tail gas treatment effect does not meet the standard, it will issue an alarm in time and take corresponding treatment measures. 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.

[0030] The circulating fan 7 is used to return the exhaust gas treated by the combustion device 6 to the disc dryer 1 for recycling. The circulating fan 7 has sufficient power and adjustment capacity to drive the exhaust gas to form a stable circulation flow in the system, ensuring the effective utilization of the exhaust 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 exhaust gas treatment effect and the needs of the disc dryer 1. By setting the circulating fan 7, the consumption of fresh air and the exhaust gas emission can be reduced, thereby realizing resource conservation and environmental protection.

[0031] The concentration meter 8 is used to monitor the VOCs concentration when the treated exhaust gas is reintroduced into the disc dryer 1 in real time, providing a basis for adjusting the system parameters to ensure stable and efficient operation of the system. For example, when the concentration meter 8 detects an abnormal change in the VOCs concentration during exhaust gas circulation, the gas monitoring and control system 5 can adjust the working parameters of the combustion device 6, the cooling device 3, etc. in time according to this data to ensure the treatment effect of the entire system on the exhaust gas containing VOCs and the stability of the treatment environment in the disc dryer 1.

[0032] Based on the tail gas recycling method of the VOCs tail gas recycling system in the above-mentioned disc dryer sludge drying process, the process is as follows: The water-containing sludge enters the disc dryer 1 through the sludge inlet, and is dried under the action of the hot medium steam. During the treatment, tail gas containing VOCs is generated. The tail gas enters the cyclone separator 2 through the tail gas outlet, and the dry sludge is initially separated. The tail gas temperature is then reduced to about 30°C by the cooling device 3. Subsequently, the cooled tail gas is reintroduced into the air inlet of the disc dryer 1 through the first branch and monitored and treated by the concentration meter 8 under the action of the circulating fan 7. 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 meter 8. When it is detected that 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, and 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 VOCs The concentration is always maintained within a safe and stable range. Part of the exhaust gas at the outlet of the combustion device 6 is directly discharged into the air, and the other part is reintroduced into the air inlet of the disc dryer 1 after being monitored and processed by the concentration meter 8 under the action of the circulating fan 7, thereby realizing efficient management and recycling of VOCs-containing exhaust gas.

[0033] The process method includes the steps of starting a disc dryer, preliminary exhaust gas treatment, exhaust gas cooling, exhaust gas control, deep combustion treatment, exhaust gas recycling and VOCs concentration monitoring. By accurately controlling the exhaust gas circulation ratio and the operation of the combustion device, and combining the VOCs concentration monitoring data, efficient management and utilization of the exhaust gas can be achieved.

[0034] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A system for recycling tail gas containing VOCs in the process of sludge drying by a disc dryer, characterized in that: The 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 meter (8), wherein 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 dry 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), and 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, and the second passage is connected to the first branch in front of the circulating fan (7), and a concentration meter (8) is also 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).

2. The system for recycling tail gas containing VOCs in the sludge drying process of a disc dryer according to claim 1 is characterized in that: A pneumatic ball valve (4) is also provided on the second branch between the cooling device (3) and the combustion device (6).

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

4. The system for recycling tail gas containing VOCs in the sludge drying process of a disc dryer according to claim 1 is characterized in that: The disc dryer (1) is provided with a sludge inlet and a dried sludge outlet. A hollow disc group is provided inside the disc dryer (1), and a heat medium inlet is provided. The heat medium flows through the disc group and transfers heat to the sludge. The sludge passes between the disc group and the outer shell, evaporating water and forming high-temperature exhaust gas containing VOCs.

5. The system for recycling tail gas containing VOCs in the sludge drying process of a disc dryer according to claim 2 is characterized in that: An air replenishment inlet is also provided on the pipeline in front of the circulating fan (7).

6. The system for recycling tail gas containing VOCs in the sludge drying process of a disc dryer according to claim 2 is characterized in that: The gas monitoring and control system (5) is electrically connected to the combustion device (6), the cooling device (3), the pneumatic ball valve (4) and the concentration meter (8) respectively.

7. The system for recycling tail gas containing VOCs in the sludge drying process of a disc dryer according to claim 6 is characterized in that: The gas monitoring and control system (5) comprises a VOCs concentration monitor and an automatic control system, which can monitor the concentration of VOCs in the exhaust 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.

8. The system for recycling tail gas containing VOCs in the sludge drying process of a disc dryer according to claim 2, characterized in that: The condensate outlet of the cooling device (3) is connected to a sewage treatment system.

9. A method for recycling tail gas containing VOCs in the process of sludge drying in a disc dryer, using the tail gas recycling system as described in any one of claims 2 to 8, characterized in that: The process is as follows: The water-containing sludge enters the disc dryer (1) through the sludge inlet, and is dried under the action of the hot medium steam. During the treatment process, tail gas containing VOCs is generated. The tail gas enters the cyclone separator (2) through the tail gas outlet, and the dry sludge is initially separated. The tail gas temperature is then reduced to about 30°C by a cooling device (3). The cooled tail gas is then reintroduced into the air inlet of the disc dryer (1) through the first branch and monitored and treated by a concentration meter (8) under the action of a circulating fan (7). 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 meter (8). When the VOCs concentration is detected to be too high, the pneumatic ball valve (4) is opened according to the instruction of the gas monitoring and control system (5), and the tail gas passes through the second branch pipeline. 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 high. The concentration is always maintained within a safe and stable range. Part of the exhaust gas at the outlet of the combustion device (6) is directly discharged into the air, and the other part is reintroduced into the air inlet of the disc dryer (1) after being monitored and processed by the concentration meter (8) under the action of the circulating fan (7), thereby achieving efficient management and recycling of the exhaust gas containing VOCs.

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