CN113499683B - VOC (volatile organic compound) based on catalytic oxidation s Composite processing system and method - Google Patents

Abstract

The invention discloses a _VOCs composite treatment system and method based on catalytic oxidation. The invention discloses a _VOCs composite treatment system based on catalytic oxidation, which includes an exhaust gas induced fan, a main exhaust fan, a desorption main fan, a cooling induced fan, a heater, and three composite treatment devices. The three composite treatment devices have the same structure, including an adsorption unit and an ozone catalytic oxidation unit. The output port of the adsorption unit is connected with the input port of the ozone catalytic oxidation unit. The adsorption unit adsorbs VOCs waste gas. The ozone catalytic oxidation unit is equipped with a catalyst, and in the case of inputting ozone, the VOCs exhaust gas is catalytically oxidized and decomposed. The catalyst in the present invention is formed by mixing α, β, and γ crystal catalysts respectively, exerts maximum thermal stability and high catalytic activity, and is not easy to sinter. In addition, the present invention realizes the decomposition of VOCs waste gas through catalytic oxidation, has lower energy consumption, and the system is more stable and reliable.

Description

A VOCs composite treatment system and method based on catalytic oxidation

technical field

The invention belongs to the technical field of ultra-low concentration and large air volume organic waste gas treatment. Specifically, it relates to a set of volatile organic compound compound treatment device and a treatment process thereof.

Background technique

VOCs exhaust gas is extremely volatile, and its generation methods are diversified, mainly from painting, motor vehicle exhaust, and heavy metal smelting. The air is seriously polluted, and it will also have a great impact on human health. Common treatment technologies for industrial VOCs include: adsorption, combustion, catalytic oxidation, absorption, etc.

The adsorption method to remove organic matter is to use activated carbon, carbon fiber, molecular sieve and other adsorbents with large specific surface area and porous structure to trap organic matter molecules. When the waste gas passes through the adsorption bed, the organic matter is adsorbed in the pores to purify the gas. The adsorption method is mainly suitable for the recovery and treatment of VOCs gas with large air volume, low humidity, low temperature and concentration less than 5000ppm. There are many factors affecting the adsorption effect of VOCs. The physical and chemical properties of the adsorbent itself, the molecular structure of VOCs, the temperature, humidity and coexisting pollutants of the external environment will all affect the process performance of the adsorption method. The molecular sieve runner is actually a kind of concentrator, using molecular sieve as an adsorption material, it can convert the original high-volume, low-concentration VOCs exhaust gas into low-volume, high-concentration exhaust gas, and the concentration ratio reaches 5-20 times. The runner has a honeycomb structure and can be divided into a treatment zone, a regeneration zone and a cooling zone, and the enrichment runner runs continuously in each zone. In the treatment area, VOCs are adsorbed and removed by the adsorbent, and the purified air is discharged from the treatment area of the concentration wheel. The organic waste gas VOCs adsorbed in the concentration wheel is desorbed by hot air treatment in the regeneration zone. The enrichment wheel is cooled in the cooling zone, and the air passing through the cooling zone is used as regeneration air after being heated, so as to achieve the effect of energy saving.

Ozone catalytic oxidation is an advanced oxidation technology carried out at low temperature. Its mechanism is that during the catalytic oxidation reaction, ozone and VOCs are adsorbed on the surface of the catalyst, and the ozone decomposes to generate active oxygen, which reacts with VOCs. Eventually carbon dioxide and water are formed. Studies have found that free radicals may be oxygen free radicals and hydroxyl free radicals. These two free radicals are extremely oxidizing, and their oxidizing ability is linearly related to the number of free radicals. Nowadays, supported catalysts are mostly used, and their carriers mainly include alumina, silica, titania, zeolite, and molecular sieve. The supported active components include noble metals and non-noble metals. The ozone catalytic oxidation process is simple, reliable and stable, and has a remarkable purification effect on VOCs.

The composition of organic waste gas is complex, and the concentration varies greatly, especially the organic waste gas emitted in industrial production. For the treatment of different VOCs, only a single process is used, the treatment efficiency is low, and there are disadvantages such as incomplete reaction and difficult to control by-products when used alone. Therefore, a combination of two processes is usually used to treat VOCs.

Contents of the invention

The object of the present invention is to provide a kind of _VOCs composite treatment system and method based on catalytic oxidation

The invention discloses a _VOCs composite treatment system based on catalytic oxidation, which includes an exhaust gas induced fan, a main exhaust fan, a desorption main fan, a cooling induced fan, a heater, and three composite treatment devices. The three composite treatment devices have the same structure, including an adsorption unit and an ozone catalytic oxidation unit. The output port of the adsorption unit is connected with the input port of the ozone catalytic oxidation unit. The adsorption unit adsorbs VOCs waste gas. The ozone catalytic oxidation unit is equipped with a catalyst, and in the case of inputting ozone, the VOCs exhaust gas is catalytically oxidized and decomposed.

Each of the three composite treatment devices has five vents, which are exhaust gas inlet, desorption inlet, cooling inlet, ozone inlet and purification gas outlet. The exhaust gas inlet, the desorption inlet and the cooling inlet are all connected to the input port of the adsorption unit; the ozone inlet is connected to the ozone supply port of the ozone catalytic oxidation unit; the output port of the ozone catalytic oxidation unit is connected to the purification gas outlet. The exhaust gas inlets of the three composite treatment devices are all connected to the VOCs exhaust gas delivery pipeline. The air outlet of the cooling induced draft fan is connected to the cooling inlets of the three composite processing units. The purification outlets of the three composite treatment devices are connected to the chimney through three valves, and connected to the air inlet of the desorption main blower through the other three valves. The air outlet of the desorption main blower is connected to the desorption air inlets of the three composite treatment devices through heaters and valves. The ozone outlet of the ozone generator is connected to the ozone inlet of the three composite treatment devices. The air outlet of the cooling induced draft fan is connected to the cooling inlets of the three composite processing units.

Preferably, the composite treatment device has three working states, which are adsorption state, desorption and decomposition state and cooling state. In the state of adsorption, VOCs exhaust gas is input from the exhaust gas inlet, and is output from the purification outlet after the organic pollutants are removed in the adsorption unit. In the state of desorption and decomposition, the hot gas flow is input from the desorption inlet, so that the organic pollutants in the adsorption unit are released, and the concentration of VOCs exhaust gas is realized; the concentrated VOCs exhaust gas enters the ozone catalytic oxidation unit; ozone is input from the ozone inlet to the ozone catalytic oxidation unit , The ozone catalytic oxidation unit performs catalytic oxidation and decomposition of VOCs exhaust gas under the action of ozone and catalyst. In the cooling state, the cold air flow is input from the cooling inlet, so that the temperature of the adsorption unit is lowered until the adsorption unit can adsorb the VOCs waste gas again.

Preferably, the catalyst used in the ozone catalytic oxidation unit is a MnOx-CeOx-LaOx catalyst prepared by a supersaturated impregnation method with metal oxide particles of three different crystal forms as the carrier.

Preferably, the crystal forms of the three metal oxide particles are α, β, and γ crystal forms respectively. The mass ratio of metal oxides in α, β, and γ crystal forms is 3:4:3.

Preferably, the metal oxide is alumina.

Preferably, a mass flow meter and a flame retardant are also arranged between the air outlet of the desorption main blower and the desorption inlets of the three composite treatment devices.

Preferably, a second three-way valve is also provided between the air outlet of the desorption main blower and the desorption air inlets of the three composite treatment devices. The third ventilation port of the second three-way valve is connected with the waste gas delivery pipeline.

Preferably, the adsorption material in the adsorption unit is activated carbon, molecular sieve, clay, zeolite or metal organic framework material.

Preferably, the adsorption unit adopts a molecular sieve wheel. The diameter of the molecular sieve runner is 2000-3000mm, and the thickness is 500-600mm.

Preferably, between the VOCs waste gas conveying pipeline and the three composite treatment devices, a waste gas induced draft fan and a dry filter box are arranged in series in series.

Preferably, the dry filter box is provided with a primary filter, a medium filter and a high filter arranged in sequence. The primary filter, intermediate filter and high efficiency filter all use quick-release aluminum frame filter bags. Among them, the filter bag of the primary filter is made of filter cotton, and the filter particle size is ≥5 μm. The filter bag of the medium-efficiency filter is made of non-woven material, and the filter particle size is 1-5 μm. The filter bag of the high-efficiency filter is made of glass fiber, and the filter particle size is 0.1-1 μm. The input port of the dry filter box, between any two filters and the output port all lead to differential pressure gauges.

Preferably, a first three-way valve is arranged between the exhaust gas induced fan and the dry filter box. The first air port of the first three-way valve is connected; the second air port of the first three-way valve is connected with the input port of the dry filter box. The third vent of the first three-way valve is connected with the chimney. When a failure occurs, the VOCs exhaust gas is evacuated by switching the first three-way valve.

Preferably, flap valves are provided at the waste gas inlet, desorption inlet, cooling inlet and ozone inlet of the three composite treatment devices.

The specific treatment process of the _VOCs composite treatment system based on catalytic oxidation is carried out in the following steps:

Step 1. Define three composite processing devices as a first composite processing device, a second composite processing device and a third composite processing device. The waste gas inlet and the purified gas outlet of the first composite treatment device are opened to enter the adsorption state, and the adsorption unit of the first composite treatment device absorbs and concentrates the organic pollutants in the input VOCs waste gas.

Step 2: When the adsorption unit in the first composite treatment device is saturated, the first composite treatment device enters a state of desorption and decomposition. The heater heated by the heater enters the adsorption unit of the first composite treatment device from the desorption inlet of the first composite treatment device, so that the adsorbed organic matter in the first composite treatment device is desorbed and enters the ozone catalytic oxidation unit with the airflow. The ozone generated by the ozone generator enters the ozone catalytic oxidation unit of the first composite treatment device; the ozone catalytic oxidation unit performs catalytic oxidation on organic pollutants. At the same time, the second composite processing device enters the adsorption state.

Step 3: When the adsorption unit in the second composite treatment device is saturated, the second composite treatment device enters a state of desorption and decomposition. The third composite processing device enters the adsorption state. The first composite processing device enters the cooling state, and the cooling induced draft fan introduces cold air from the external environment into the adsorption unit of the first composite processing device, so that the temperature in the first composite processing device decreases and the original adsorption capacity is restored. The temperature-increased airflow output by the first composite processing device is merged into the second composite processing device in a state of desorption and decomposition, so as to reduce energy consumption.

Step 4: The first composite treatment device, the second composite treatment device and the third composite treatment device are switched cyclically among the adsorption state, the desorption decomposition state and the cooling state, so that one composite treatment device is in the adsorption state at any time.

The beneficial effects that the present invention has are:

1. The VOCs purification efficiency of the present invention is high. The present invention uses a set of "composite" VOCs treatment device, the adsorbent used is molecular sieve, the molecular sieve has high adsorption and desorption efficiency, can absorb and concentrate most of VOCs, and then process through ozone catalytic oxidation, the ozone catalytic oxidation unit will VOCs gas is degraded into carbon dioxide and water, which will be discharged if the standard is met, and will be recycled if the standard is not met. In general, the device of the present invention has a significant purification effect on VOCs. The energy-saving high-temperature shift catalyst in the ozone catalytic oxidation device is a mixture of α, β, and γ crystal catalysts, which exert maximum thermal stability and high catalytic activity, and are not easy to sinter.

2. The present invention is energy-saving and environment-friendly, and has no secondary pollutants. A small part of the exhaust gas after combustion in the present invention enters the atmosphere, and most of it is sent to the cooling area of the adsorption unit for reuse by the molecular sieve runner, which can not only meet the heat energy required for catalytic oxidation and adsorption, but also achieve the purpose of energy saving. In addition, the pressure drop generated by the adsorption of VOCs by the molecular sieve runner is extremely low, which can greatly reduce power consumption. Ozone catalytic oxidation degrades VOCs into carbon dioxide and water, and the tail gas is released to the atmosphere after passing the test. There are no other by-products and no secondary pollution.

3. The treatment process of the present invention is simple, stable and easy to control, safe and reliable. The process of the invention only includes filtration, adsorption unit and ozone catalytic oxidation unit, the treatment process is simple, the equipment operation is simple, controlled by PLC, stable, convenient and easy to manage. The exhaust gas is pretreated by a dry filter to remove the particles mixed in the exhaust gas and then proceed to the subsequent process, which is safe and reliable. The ozone generator and its electronic control equipment that generate ozone can be placed remotely without direct contact with the exhaust gas. In addition, the present invention adopts a modular design, has the minimum space requirement, and provides a continuous and unmanned control mode. Moreover, the present invention adopts PLC self-control technology, system automatic control, one-button start, simple operation, and can be matched with man-machine interface to monitor important operation data, to flexibly and accurately control the entire processing process, and improve the stability and controllability of the entire process sex.

4. Low investment and operating costs, wide application range. The present invention is aimed at the treatment of industrial waste gas with low concentration, large air volume and complex components. The molecular sieve runner is used to convert the original high air volume and low concentration VOCs waste gas into low air volume and high concentration waste gas, and the concentration ratio reaches 5-20 times. , the specifications of post-processing equipment are greatly reduced, and the operating cost is lower. It is suitable for most VOCs emission industries such as spraying, printing, and paint production. It is extremely suitable for medium and small industrial polluting enterprises. The process of the present invention will not produce secondary pollution. , It is especially suitable for enterprises without sewage treatment facilities and limited investment in environmental protection, with low equipment and operating costs, and simple and controllable post-maintenance.

5. The present invention adopts filtration technology, utilizes the dry filter box to efficiently purify the particulate matter in the exhaust gas, and ensures the stable and efficient operation of subsequent equipment.

Description of drawings

Fig. 1 is the waste gas treatment process flow chart of the present invention;

Fig. 2 is the comparative spectrogram of drying tail gas in the specific example and the result of VOCs exhaust gas treatment by the present invention.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings.

As shown in Figure 1, a _VOCs composite treatment system based on catalytic oxidation can perform adsorption and desorption-ozone catalytic oxidation composite treatment on volatile organic compounds, which includes exhaust gas induced draft fan 1-1, main exhaust fan 1-2, Desorption main fan 1-3, cooling induced draft fan 1-4, flame retardant 3, dry filter 4, first three-way valve 5-1, second three-way valve 5-1, valve group, mass flow meter 6. Heater 11 , first composite processing device 8 , second composite processing device 9 and third composite processing device 10 . The first combined treatment device 8 , the second combined treatment device 9 and the third combined treatment device 10 can perform combined treatment of adsorption and desorption and ozone catalytic oxidation on volatile organic compounds.

The first composite treatment device 8 , the second composite treatment device 9 and the third composite treatment device 10 have the same structure and are all adsorption-desorption-ozone catalytic oxidation composite devices. The composite device of adsorption-desorption-ozone catalytic oxidation includes an adsorption unit and an ozone catalytic oxidation unit. The output port of the adsorption unit is connected with the input port of the ozone catalytic oxidation unit. The adsorption material adopts activated carbon, molecular sieve, clay, zeolite or metal organic framework material. In this embodiment, the adsorption unit is preferably a molecular sieve wheel. Molecular sieve runner is divided into treatment zone, regeneration zone and cooling zone. The diameter of the molecular sieve runner is 2000-3000mm, and the thickness is 500-600mm.

The ozone concentration of the ozone catalytic oxidation unit in the working process should be 1500-2000mg/m ³ ; the ratio of VOCs waste gas to ozone is 1:15-1:10. Energy-saving high-temperature shift non-precious metal-supported catalyst in an ozone catalytic oxidation unit. Noble metals have many heteroatoms and are easy to sinter at higher temperatures. Sublimation leads to the loss of active components, which reduces the activity, and is expensive and cannot be used on a large scale. The activity of non-noble metal catalysts is sufficient for industrial application, and transition metal elements used to construct non-noble metal electrocatalysts include iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), molybdenum (Mo) and Tungsten (W). The carrier of the catalyst is aluminum oxide, silicon dioxide, titanium dioxide, zeolite or molecular sieve.

As a preferred technical solution, the catalyst described in this article uses MnOx prepared by supersaturated impregnation method with three different crystal forms of α-A1 ₂ 0 ₃ , β-A1 ₂ 0 ₃ , and γ-A1 ₂ 0 ₃ as carriers. - CeOx-LaOx catalysts. The carrier is mixed with oxides of three different crystal forms, and the three crystal forms are α, β, and γ crystal forms respectively. Make the catalyst exert the greatest thermal stability and high catalytic activity, and it is not easy to sinter. The initial crystal forms of different catalysts will have a great influence on the properties of the reduced catalysts. In order to achieve the best catalytic activity, the mixing ratios of the catalysts used in this invention are 30%, 40%, and 30%, respectively.

The adsorption-desorption-ozone catalytic oxidation compound device has five vents, which are waste gas inlet, desorption inlet, cooling inlet, ozone inlet and purification outlet. The exhaust gas inlet, the desorption inlet and the cooling inlet are all connected to the input port of the adsorption unit; the ozone inlet is connected to the ozone supply port of the ozone catalytic oxidation unit; the output port of the ozone catalytic oxidation unit is connected to the purification gas outlet.

The adsorption-desorption-ozone catalytic oxidation composite device has three working states, which are adsorption state, desorption decomposition state and cooling state. In the state of adsorption, VOCs exhaust gas is input from the exhaust gas inlet, and is output from the purification outlet after the organic pollutants are removed in the adsorption unit. In the state of desorption and decomposition, the hot gas flow is input from the desorption inlet, so that the organic pollutants in the adsorption unit are released, and the concentration of VOCs exhaust gas is realized; the concentrated VOCs exhaust gas enters the ozone catalytic oxidation unit; ozone is input from the ozone inlet to the ozone catalytic oxidation unit , The ozone catalytic oxidation unit performs catalytic oxidation and decomposition of VOCs exhaust gas under the action of ozone and catalyst. In the cooling state, the cold air flow is input from the cooling inlet, so that the temperature of the adsorption unit is lowered until the adsorption unit can adsorb the VOCs waste gas again.

The input port of the exhaust gas induced draft fan 1-1 is connected to the exhaust gas conveying pipeline, and the output port is connected to the first vent port of the first three-way valve 5-1; the second vent port of the first three-way valve 5-1 is connected to the dry filter Connect to the input port of box 4. The third air port of the first three-way valve 5-1 is connected with the chimney, and is used for emergency emptying of waste gas in case of failure. The third air port of the first three-way valve 5-1 is connected with the chimney, and is used for emergency emptying of waste gas in case of failure. The valve group includes the first flap valve 2-1, the second flap valve 2-2, the third flap valve 2-3, the fourth flap valve 2-4, the fifth flap valve 2-5, the sixth flap valve Flap valve 2-6, seventh flap valve 2-7, eighth flap valve 2-8, ninth flap valve 2-9, tenth flap valve 2-10, eleventh flap valve 2 -11, the twelfth flap valve 2-12, the thirteenth flap valve 2-13, the fourteenth flap valve 2-14, the fifteenth flap valve 2-15, the sixteenth flap valve 2 -16, the seventeenth flap valve 2-17, the eighteenth flap valve 2-18 and the nineteenth flap valve 2-19. The output port of the dry filter box 4 is connected with one end of the second flap valve 2-2, the fourth flap valve 2-4, and the sixth flap valve 2-6. The other end of the second flap valve 2-2, the fourth flap valve 2-4, the sixth flap valve 2-6 and the first composite processing device 8, the second composite processing device 9, and the third composite processing device 10 The exhaust gas inlets are connected separately.

The air inlet of the cooling induced draft fan 1-4 is connected with the external environment; the air outlet of the cooling induced draft fan 1-4 is connected with the fifteenth flap valve 2-15, the sixteenth flap valve 2-16 and the seventeenth flap valve 2-17 is connected at one end. The other ends of the fifteenth flap valve 2-15, the sixteenth flap valve 2-16, and the seventeenth flap valve 2-17 are combined with the first composite processing device 8, the second composite processing device 9, and the third composite processing device. The cooling inlets of the processing device 10 are respectively connected. The purification outlets of the first composite processing device 8, the second composite processing device 9, and the third composite processing device 10 are connected to the eighth flap valve 2-8, the tenth flap valve 2-10, and the twelfth flap valve 2 One end of -12 is connected separately. The other ends of the eighth flap valve 2-8, the tenth flap valve 2-10, and the twelfth flap valve 2-12 are all connected to the air inlet of the main exhaust fan 1-2. The air outlet of the main exhaust fan 1-2 communicates with the chimney for outward discharge. One end of the fourteenth flap valve 2-14, the eighteenth flap valve 2-18, and the nineteenth flap valve 2-19 is connected to the first composite processing device 8, the second composite processing device 9, and the third composite processing device. The purified air outlets of the device 10 are connected respectively. The other ends of the fourteenth flap valve 2-14, the eighteenth flap valve 2-18, and the nineteenth flap valve 2-19 are all connected to the air inlet of the desorption main fan 1-3. The air outlet of the desorption main fan 1-3 is connected with the input port of the flame retardant 3 through the thirteenth flap valve 2-13. The output port of the flame arrester 3 is connected to the input port of the heater 11; the output port of the heater 11 is connected to the first air port of the second three-way valve 5-2 through the mass flow meter 6. The heater 11 can heat the gas passing through itself to form a hot air flow. The second air port of the second three-way valve 5-2, one end of the first flap valve 2-1, the third flap valve 2-3, the fifth flap valve 2-5 and the output of the dry filter box 4 port connection. The third ventilation port of the second three-way valve 5-2 is connected with the air inlet of the exhaust gas induced draft fan 1-1. The other end of the first flap valve 2-1, the third flap valve 2-3, and the fifth flap valve 2-5 are connected to the first composite processing device 8, the second composite processing device 9, and the third composite processing device 10. The desorption inlets are connected separately. The ozone outlet of the ozone generator 7 is connected with one end of the seventh flap valve 2-7, the ninth flap valve 2-9, and the eleventh flap valve 2-11. The other end of the seventh flap valve 2-7, the ninth flap valve 2-9, the eleventh flap valve 2-11 and the first composite processing device 8, the second composite processing device 9, and the third composite processing device 10 ozone inlets are connected separately.

The mass flow meter 6 monitors the degraded tail gas. If the discharge standard is met, it will be discharged to the chimney through the second three-way valve 5-2 and the fourteenth flap valve 2-14, or through the second three-way valve 5-2, the first flap valve 2-1, the third The flap valve 2-3 and the fifth flap valve 2-5 enter the molecular sieve runners of the first composite processing device 8, the second composite processing device 9 and the third composite processing device 10 for reuse. The chimney is connected with the external environment for outputting the purified gas. If the tail gas does not meet the discharge standard, the tail gas will enter the first composite processing device and the second composite processing device through the second flap valve 2-2, the fourth flap valve 2-4, and the sixth flap valve 2-6 respectively. , The third composite treatment device performs adsorption concentration again, and circulates the treatment until the tail gas reaches the discharge standard.

The present invention adopts three gas pipelines. When the molecular sieve regeneration zone is working, the hot air flows from the first flap valve, the third flap valve, and the fifth flap valve into the first composite processing device, the second composite processing device, The third composite processing device. When the molecular sieve cooling zone is working, the cold air flows from the first flap valve, the third flap valve, and the fifth flap valve into the first composite processing device, the second composite processing device, and the third composite processing device.

The dry filter box 4 is provided with a preliminary filter, a medium filter and a high efficiency filter arranged in sequence. The primary filter, intermediate filter and high efficiency filter all use quick-release aluminum frame filter bags, which are easy to replace by weight. Among them, the filter bag of the primary filter is made of filter cotton, and the filter particle size is ≥5 μm. The filter bag of the medium-efficiency filter is made of non-woven material, and the filter particle size is 1-5 μm. The filter bag of the high-efficiency filter is made of glass fiber, and the filter particle size is 0.1-1 μm. The input port of the dry-type filter box, between any two filters and the output port all lead to pressure difference gauges, so as to monitor the pressure difference between the two ends of the filter, and remind the operator to replace the filter. The filtration speed of each filter bag is 1-1.5m/s, and the empty flow velocity of the box is 2-3m/s.

The signal output lines of each differential pressure gauge and each flap valve in the valve group are connected to the controller; the motors in the exhaust gas induced draft fan 1-1, the main exhaust fan 1-2, and the desorption main fan 1-3 are all connected to the controller The controller is connected through the motor driver. The controller adopts PLC. Thus, the whole processing technology is controlled by the PLC automatic control system, and the PLC automatic control system is composed of a programming system, an electric control cabinet (including a touch screen), an electric flap valve and a pressure sensor. During the operation, by controlling the electric flap valve of the exhaust gas in and out of the pipeline, three identical composite treatment devices are carried out alternately, and the 24-hour cycle alternately works to efficiently purify VOCs in the exhaust gas, and finally the treated gas is discharged through the chimney up to the standard. Control parameters The adsorption time is 1~2h, and the desorption time is determined by the intake concentration and the desorption air volume, generally greater than 0.5h.

The specific treatment process of this volatile organic compound treatment device is carried out in the following steps:

Step 1. Automatically controlled by PLC, the induced draft fan is started, and the organic waste gas enters the treatment system, and enters the dry filter 4 through the induced draft fan to remove particulate matter.

Step 2, the second flap valve and the eighth flap valve are opened, the first composite processing device enters the adsorption state, and the organic waste gas output from the dry filter 4 enters the first composite processing device through the second flap valve, and the second composite processing device enters the adsorption state. An adsorption unit of a composite treatment device performs adsorption and concentration of organic pollutants in VOCs waste gas. After the organic pollutants are adsorbed, the tail gas composite discharge standard is discharged through the main exhaust fan 1-2 and the chimney. The entire adsorption and concentration process is controlled within 1-2 hours.

Step 3. When the adsorption unit in the first compound treatment device is saturated (that is, after 1 to 2 hours), the first flap valve, the seventh flap valve, and the fourteenth flap valve are opened through PLC automatic control. , the second flap valve is closed, the desorption fan 1-3 and the ozone generator 7 are opened, and the first composite treatment device enters the desorption and decomposition state. Under the suction generated by the desorption main blower 1-3, the thirteenth flap valve, the flame retardant 3, the heater 11, the mass flow meter 6, and the first flap valve 2-1 enter the first composite treatment process. The airflow in the regeneration area of the adsorption unit of the device; the airflow is heated by the heater 11 to desorb the organic matter from the adsorption unit and enter the ozone catalytic oxidation unit with the airflow, so that the VOCs exhaust gas is concentrated to 5-20 times. The ozone generated by the ozone generator 7 enters the ozone catalytic oxidation unit of the first composite treatment device; the ozone catalytic oxidation unit catalyzes the oxidation of organic pollutants, so that the organic pollutants are degraded into carbon dioxide and water vapor. The residence time of the adsorbed and concentrated tail gas in the ozone catalytic oxidation unit should be 10-15s. The air flow rate of the ozone catalytic oxidation unit was set at 4 L/min. The tail gas output by the ozone catalytic oxidation unit passes through the desorption main fan 1-3 and the mass flow meter 6; the mass flow meter 6 detects the catalytic oxidation tail gas, and if the tail gas meets the emission standard, it passes through the eighth flap valve 2- 8 is discharged to the chimney; otherwise, the exhaust gas is re-input to the first composite processing device through the first flap valve 2-1, or is transported to the input port of the exhaust gas induced draft fan 1-1 through the first three-way valve 5-1.

Simultaneously, the fourth flap valve, the tenth flap valve, and the eighteenth flap valve (the gas source that provides the hot air flow) are opened, and the second compound treatment device enters the adsorption state, and the VOCs waste gas output by the dry filter 4 is carried out. adsorption.

Step 4. When the adsorption unit in the second composite treatment device is saturated (i.e. after 1 to 2 hours), automatically controlled by PLC, the third flap valve and the ninth flap valve are opened, and the fourth flap valve is closed. The second composite treatment device enters the state of desorption and decomposition, and catalyzes and oxidizes the organic pollutants adsorbed in the second composite treatment device.

At the same time, the sixth flap valve and the twelfth flap valve are opened, and the third composite treatment device enters an adsorption state to adsorb the VOCs waste gas output by the dry filter 4 . The fifteenth flap valve and the fourteenth flap valve are opened, the first flap valve, the seventh flap valve and the eighth flap valve are closed, the first composite processing device enters the cooling state, and the cooling induced draft fans 1-4 are started , introduce cold air flow from the external environment to the adsorption unit of the first composite treatment device, so that the temperature in the first composite treatment device is reduced; the airflow with increased temperature output by the first composite treatment device is passed into the desorption fan 1- 3 air inlets to reduce energy consumption; after 0.5 hours of cooling, the first composite treatment device restores its original adsorption capacity.

Step 5. PLC controls the first composite processing device, the second composite processing device and the third composite processing device to switch between the adsorption state, the desorption decomposition state and the cooling state, so that one composite processing device is in the adsorption state at any time state, to achieve 24-hour continuous treatment of VOCs exhaust gas. The temperature of the whole composite device is controlled at 0°C-100°C, the system is automatically controlled, one-button start, easy to operate, and the temperature of each unit can be adjusted with the man-machine interface, and the VOCs treatment effect can reach more than 95%.

In addition, the entire process has operation protection measures: 1. When the follow-up device cannot operate normally, the exhaust gas can be evacuated by manually switching the first three-way valve 5-1, so as to ensure that the exhaust gas in the workshop can be discharged smoothly and avoid causing damage to the workshop. VOCs accumulate, and the concentration is too high to affect the health of workers. 2. Both the dry filter box and the adsorption device are equipped with differential pressure gauges to prevent the blockage of the filter bag or adsorption/catalyst from affecting the normal operation of the entire process.

The VOCs waste gas treatment effect of the present invention is illustrated by experiment below:

In a pharmaceutical production enterprise in Zhejiang, the exhaust gas was dried, and even after three-stage alkali spraying, the foul smell was still obvious. The present invention is used for on-site experiments; the experimental results prove that the present invention can significantly remove the peculiar smell of VOCs waste gas, basically no peculiar smell can be smelled at the discharge port of the experimental device, and the dimensionless value of the stench is less than 300 after three-party testing.

The samples submitted for inspection were determined by Shimadzu GCMS-TQ8050 mass spectrometer and manual solid-phase microextraction, and qualitative analysis was performed by library search using NIST14 standard mass spectral library. The analysis results are shown in Figure 2. In Fig. 2, curve A corresponds to the situation of only drying tail gas, and curve B corresponds to the situation after being processed by the technical scheme recorded in the present invention. It can be seen from Figure 2 that the main substances in the drying tail gas are toluene, m-bromotoluene and p-bromotoluene, 3-bromo-2,2-dimethyl-1-propanol, naphthalene and 2,4-dimethyl Benzaldehyde etc. The main substances of the tail gas treated by the adsorption-ozone catalytic oxidation composite device are toluene, m-bromotoluene and p-bromotoluene, etc. Explain that VOCs exhaust gas is processed by the present invention and after drying, the component chromatography of toluene, m-bromotoluene, p-bromotoluene, 3-bromo-2,2-dimethyl-1-propanol and 2,4-dimethylbenzaldehyde The peak is significantly reduced.

Claims (6)

1. A _VOCs composite treatment system based on catalytic oxidation, including exhaust air induced draft fan (1-1), main exhaust fan (1-2), desorption main fan (1-3), cooling induced draft fan (1-4 ), a heater (11) and three composite treatment devices; it is characterized in that: the three composite treatment devices have the same structure, and all include an adsorption unit and an ozone catalytic oxidation unit; the output port of the adsorption unit is connected to the input port of the ozone catalytic oxidation unit The adsorption unit adsorbs the VOCs exhaust gas; the ozone catalytic oxidation unit is equipped with a catalyst, and in the case of inputting ozone, the VOCs exhaust gas is catalytically oxidized and decomposed; The catalyst used in the ozone catalytic oxidation unit is a MnOx-CeOx-LaOx catalyst prepared by a supersaturated impregnation method with three different crystal forms of A1 ₂ O ₃ particles as the carrier. The three A1 ₂ O ₃ The crystal forms of the particles are α, β, and γ crystal forms respectively; the mass ratio of A1 ₂ O ₃ particles of α, β, and γ crystal forms is 3:4:3; Each of the three composite treatment devices has five vents, which are exhaust gas inlet, desorption inlet, cooling inlet, ozone inlet and purification outlet; exhaust gas inlet, desorption inlet and cooling inlet are all connected to the input port of the adsorption unit; ozone The inlet is connected to the ozone supply port of the ozone catalytic oxidation unit; the output port of the ozone catalytic oxidation unit is connected to the purification outlet; the exhaust gas inlets of the three composite treatment devices are all connected to the VOCs exhaust gas pipeline; the cooling induced draft fan (1-4) The air outlet is connected to the cooling inlet of the three composite treatment devices; the purified air outlet of the three composite treatment devices is connected to the chimney through three valves, and connected to the air inlet of the desorption main fan (1-3) through the other three valves ; The air outlet of the desorption main fan (1-3) is connected to the desorption air inlet of the three composite treatment devices through the heater (11) and the valve; the ozone outlet of the ozone generator (7) is connected to the three composite treatment devices The ozone inlet of the device; the air outlet of the cooling induced draft fan (1-4) is connected to the cooling inlet of the three composite treatment devices; The composite treatment device has three working states, which are adsorption state, desorption and decomposition state, and cooling state; in the adsorption state, VOCs waste gas is input from the waste gas inlet, and the organic pollutants are removed from the adsorption unit after being purified. Gas port output; in the state of desorption and decomposition, the hot air flow is input from the desorption inlet, so that the organic pollutants in the adsorption unit are released, and the concentration of VOCs exhaust gas is realized; the concentrated VOCs exhaust gas enters the ozone catalytic oxidation unit; ozone is input from the ozone inlet to the ozone Catalytic oxidation unit, the ozone catalytic oxidation unit catalyzes the oxidation and decomposition of VOCs exhaust gas under the action of ozone and catalyst; in the cooling state, the cold air flow is input from the cooling inlet, which reduces the temperature of the adsorption unit until the adsorption unit can adsorb VOCs exhaust gas again. 2. A VOCs composite treatment system based on catalytic oxidation according to claim 1, characterized in that: between the air outlet of the desorption main fan (1-3) and the desorption air inlets of the three composite treatment devices A mass flow meter (6), a flame retardant (3) and a second three-way valve (5-2) are also provided. 3. A VOCs composite treatment system based on catalytic oxidation according to claim 1, characterized in that: between the VOCs exhaust gas conveying pipeline and the three composite treatment devices, exhaust gas induced draft fans (1-1) and Dry filter box (4). 4. A VOCs composite treatment system based on catalytic oxidation according to claim 3, characterized in that: the dry filter box (4) is provided with primary filter, intermediate filter and High-efficiency filter; primary-effect filter, medium-efficiency filter and high-efficiency filter all use quick-release aluminum frame filter bags; among them, the filter bag of the primary-effect filter is made of filter cotton, and the filter particle size is ≥ 5 μm; the medium-efficiency filter The filter bag of the filter is made of non-woven fabric, with a filter particle size of 1-5 μm; the filter bag of the high-efficiency filter is made of glass fiber, with a filter particle size of 0.1-1 μm; the input port of the dry filter box, any two filters The differential pressure gauges are drawn from both the outlet and the outlet. 5. A VOCs composite treatment system based on catalytic oxidation according to claim 3, characterized in that: a first three-way valve ( 5-1); the first vent of the first three-way valve (5-1) is connected to the exhaust air induced draft fan (1-1); the second vent of the first three-way valve (5-1) is connected to the dry filter The input port of the box (4) is connected; the third vent of the first three-way valve (5-1) is connected with the chimney; when a failure occurs, the VOCs exhaust gas is emptied by switching the first three-way valve. 6. the processing method of a kind of _VOCs compound treatment system based on catalytic oxidation as claimed in claim 1, is characterized in that: step 1, three compound treatment devices are respectively defined as the first compound treatment device, the second compound treatment device and the third compound treatment device; the waste gas inlet and the purification outlet of the first compound treatment device are opened to enter the adsorption state, and the adsorption unit of the first compound treatment device absorbs and concentrates the organic pollutants in the input VOCs waste gas; Step 2. When the adsorption unit in the first composite treatment device is saturated, the first composite treatment device enters the state of desorption and decomposition; the airflow obtained by heating with the heater (11) enters from the desorption inlet of the first composite treatment device The adsorption unit of the first composite treatment device makes the organic matter adsorbed in the first composite treatment device desorb and enter the ozone catalytic oxidation unit with the airflow; the ozone generated by the ozone generator (7) enters the ozone catalytic oxidation of the first composite treatment device In the unit; the ozone catalytic oxidation unit catalyzes the oxidation of organic pollutants; at the same time, the second composite treatment device enters the adsorption state; Step 3: When the adsorption unit in the second composite processing device is saturated, the second composite processing device enters the desorption and decomposition state; the third composite processing device enters the adsorption state; the first composite processing device enters the cooling state, and the cooling induced draft fan ( 1-4) Introduce cold air from the external environment into the adsorption unit of the first composite treatment device, so that the temperature in the first composite treatment device decreases and restores the original adsorption capacity; the output temperature of the first composite treatment device increases The air flow is merged into the second compound treatment device in the state of desorption and decomposition, so as to reduce energy consumption; Step 4: The first composite treatment device, the second composite treatment device and the third composite treatment device are switched cyclically among the adsorption state, the desorption decomposition state and the cooling state, so that one composite treatment device is in the adsorption state at any time.

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