A combined waste gas treatment system and treatment method thereof

Abstract

The invention relates to a combined exhaust gas treatment system and method thereof, which comprises a vortex tube, an SCR component and a condensation recovery component. The vortex tube has a vortex chamber inside and is formed with an air inlet connected to the vortex chamber, so that the exhaust gas introduced from the air inlet forms a vortex in the vortex chamber. The vortex tube also comprises a hot end tube and a cold end tube which are coaxial and connected to the vortex chamber. The inner diameter of the cold end tube is smaller than the inner diameter of the hot end tube, and the inner diameter of the hot end tube is smaller than the inner diameter of the vortex chamber. Under the action of temperature difference and density difference, nitrogen oxides are guided out from the cold end tube, and volatile organic compounds are guided out from the hot end tube. When the exhaust gas is introduced into the vortex tube, under the dual action of temperature and density, the nitrogen oxide gas will gather in the inner circle and be discharged from the cold end tube, and the volatile organic compounds will gather in the outer circle and be discharged from the hot end tube, thereby achieving a separation effect, effectively reducing the energy consumption required for separating the combined exhaust gas. At the same time, the condensation recovery component can collect volatile organic compounds, thereby improving the utilization rate of resources.

Description

Technical Field

[0001] The present invention relates to the technical field of waste gas treatment, and in particular to a combined waste gas treatment system and method thereof. Background Art

[0002] In the industrial production process, volatile organic compounds (hereinafter referred to as VOCs), nitrogen oxides (hereinafter referred to as NOx) and other waste gases will be generated.

[0003] The existing treatment technologies for VOCs and NOx mixed exhaust gas mainly use thermal distillation separation technology, activated carbon adsorption RTO / RCO technology and SCR spray technology to jointly treat the mixed exhaust gas.

[0004] The above separation technologies have the problems of high energy consumption and low waste recycling rate. Summary of the invention

[0005] In view of this, it is necessary to provide a combined exhaust gas treatment system and method thereof to solve the problems of high energy consumption and low waste recycling rate in the existing process for separating volatile organic compounds and nitrogen oxides.

[0006] The present invention provides a combined exhaust gas treatment system, comprising a vortex tube, an SCR component and a condensation recovery component. The vortex tube has a vortex chamber inside and is formed with an air inlet connected to the vortex chamber, so that the exhaust gas introduced from the air inlet forms a vortex in the vortex chamber. The system also comprises a hot end tube and a cold end tube which are coaxial and connected to the vortex chamber. The inner diameter of the cold end tube is smaller than the inner diameter of the hot end tube, and the inner diameter of the hot end tube is smaller than the inner diameter of the vortex chamber. Under the action of temperature difference and density difference, nitrogen oxides are extracted from the cold end tube and volatile organic compounds are extracted from the hot end tube. The SCR component is connected to the cold end tube to treat nitrogen oxides, and the condensation recovery component is connected to the hot end tube to recover volatile organic compounds.

[0007] Furthermore, the SCR component includes a reaction box and a water replenishing component, an ammonia replenishing component and a catalyst component which are sequentially arranged along the gas flow direction inside the reaction box, the water replenishing component has a water replenishing end for adjusting the ratio between nitrogen monoxide and nitrogen dioxide in nitrogen oxides, the ammonia replenishing component has an ammonia replenishing end for conveying ammonia to the reaction box, and the catalyst component catalyzes the decomposition of the nitrogen oxides into nitrogen and water.

[0008] Furthermore, the water replenishing member includes a water tank and a first spray pipe built into the reaction box, and one end of the first spray pipe is connected to the water tank via a water pump;

[0009] The ammonia replenishing component includes an ammonia storage box and a solenoid valve, and the ammonia storage box is connected to the reaction box via the solenoid valve.

[0010] Furthermore, the condensation recovery component includes a plurality of condensers connected in sequence, and the temperatures in the plurality of condensers are set in steps, respectively used to recover volatile organic compounds with different boiling points.

[0011] Furthermore, it also includes the flow detection module installed on the cold end pipe, which is used to detect the gas flow in the cold end pipe.

[0012] Furthermore, it also includes a flow control module, which is connected to the flow detection module to receive and process the flow signal of the gas in the cold end tube, and the flow control module is connected to the ammonia supplement component to control the flow of ammonia delivered to the reaction box by the ammonia supplement component according to the flow signal of the gas in the cold end tube.

[0013] Furthermore, it also includes a filter element, which is installed at the air inlet of the vortex tube to filter large particles mixed in the exhaust gas.

[0014] The present invention also provides a combined exhaust gas treatment method, comprising the combined exhaust gas treatment system as described above, and further comprising the steps of:

[0015] The combined exhaust gas is introduced into the vortex tube. Under the effect of temperature difference and density difference, nitrogen oxides are discharged from the cold end tube and volatile organic compounds are discharged from the hot end tube.

[0016] The SCR component processes nitrogen oxides derived from the cold end pipe;

[0017] The condensation recovery component recovers the volatile organic matter derived from the medium heat end pipe.

[0018] Furthermore, the SCR component processes the nitrogen oxides derived from the cold end pipe, comprising the following steps:

[0019] Mixing distilled water into the nitrogen oxides entering the SCR component to adjust the ratio between nitrogen monoxide and nitrogen dioxide in the nitrogen oxides;

[0020] Ammonia gas is introduced and decomposed by a catalyst to produce nitrogen gas and water.

[0021] Furthermore, the condensation recovery component realizes temperature step recovery according to the boiling points of different substances in the volatile organic compounds.

[0022] Compared with the prior art: the combined high-pressure exhaust gas is passed into the vortex tube, and a vortex is generated in the vortex chamber. The gas speed of the inner circle of the vortex will gradually decrease, and the gas speed of the outer circle will gradually increase. The gas in the inner circle transfers the lost kinetic energy to the gas in the outer circle in the form of internal energy, so the gas temperature in the inner circle gradually decreases, and the gas temperature in the outer circle gradually increases. At this time, the volatile organic matter that is easy to liquefy in the inner circle gas will become liquid at a lower temperature. At the same time, because its density is greater than that of nitrogen oxides, it has a tendency to move to the periphery, while the nitrogen oxides in the periphery have a tendency to move inward. Under the dual effects of temperature and density, the nitrogen oxide gas will gather in the inner circle and be discharged from the cold end pipe, and the volatile organic matter will gather in the outer circle and be discharged from the hot end pipe, thereby achieving a separation effect, effectively reducing the energy consumption required for separating the combined exhaust gas. At the same time, the condensation recovery component can collect volatile organic matter, thereby improving the utilization rate of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the overall working process in the combined exhaust gas treatment system provided by an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of the operation of gas separation in a vortex tube in a combined exhaust gas treatment system provided by an embodiment of the present invention;

[0025] Figure 3 A schematic diagram of the structure of a test device in a combined exhaust gas treatment system provided in an embodiment of the present invention;

[0026] Figure 4 A working principle diagram of the SCR component in the combined exhaust gas treatment system provided by an embodiment of the present invention;

[0027] Figure 5 A schematic diagram of the relationship between exhaust gas pressure and cold and hot end temperatures in a combined exhaust gas treatment system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0029] like Figure 1-2As shown, a combined exhaust gas treatment system provided by the present invention includes a vortex tube 100, an SCR component 200 and a condensation recovery component. The vortex tube 100 has a vortex chamber 110 inside and is formed with an air inlet 120 connected to the vortex chamber 110, so that the exhaust gas introduced from the air inlet 120 forms a vortex in the vortex chamber 110. It also includes a hot end pipe 140 and a cold end pipe 130 that are coaxial and connected to the vortex chamber 110. The inner diameter of the cold end pipe 130 is smaller than the inner diameter of the hot end pipe 140, and the inner diameter of the hot end pipe 140 is smaller than the inner diameter of the vortex chamber 110. Under the action of temperature difference and density difference, nitrogen oxides are discharged from the cold end pipe 130 and volatile organic compounds are discharged from the hot end pipe 140. The SCR component 200 is connected to the cold end pipe 130 to treat nitrogen oxides, and the condensation recovery component is connected to the hot end pipe 140 to recover volatile organic compounds.

[0030] During implementation, the combined high-pressure exhaust gas is introduced into the vortex tube 100, and a vortex is generated in the vortex chamber 110. The gas speed of the inner circle of the vortex will gradually decrease, and the gas speed of the outer circle will gradually increase. The gas in the inner circle transfers the lost kinetic energy to the gas in the outer circle in the form of internal energy, so the gas temperature in the inner circle gradually decreases, and the gas temperature in the outer circle gradually increases. At this time, the volatile organic matter that is easy to liquefy in the inner circle gas will become liquid at a lower temperature. At the same time, because its density is greater than that of nitrogen oxides, it has a tendency to move toward the periphery, while the nitrogen oxides in the periphery have a tendency to move inward. Under the dual effects of temperature and density, the nitrogen oxide gas will gather in the inner circle and be discharged from the cold end tube 130, and the volatile organic matter will gather in the outer circle and be discharged from the hot end tube 140, thereby achieving a separation effect, effectively reducing the energy consumption required for separating the combined exhaust gas. At the same time, the condensation recovery component can collect volatile organic matter, thereby improving the utilization rate of resources.

[0031] The vortex tube 100 in this embodiment has a vortex chamber 110 inside and an air inlet 120 connected to the vortex chamber 110, so that the exhaust gas introduced from the air inlet 120 forms a vortex in the vortex chamber 110. It also includes a hot end pipe 140 and a cold end pipe 130 that are coaxial with and connected to the vortex chamber 110. The diameters of the cold end pipe 130, the hot end pipe 140 and the vortex chamber 110 increase gradually. Under the action of temperature difference and density difference, nitrogen oxides are discharged from the cold end pipe 130 and volatile organic compounds are discharged from the hot end pipe 140.

[0032] The combined high-pressure exhaust gas mainly composed of nitrogen oxides and volatile organic compounds is introduced into the vortex chamber 110 from the air inlet 120 and hits the spiral entity therein, thereby generating a vortex. Under the dual effects of temperature and density, the nitrogen oxide gas will gather in the inner circle and be discharged from the cold end pipe 130, and the volatile organic compounds will gather in the outer circle and be discharged from the hot end pipe 140.

[0033] To prove the correctness of the working principle of the vortex tube 100, a detailed description and explanation is given below:

[0034] Since the gas flow rate inside the vortex tube 100 is fast and the motion is complex, it can be considered that the fluid inside the vortex tube 100 is in turbulent motion and the gas is in a compressible state. The turbulent motion is simulated according to the Standard k-ε model [3], and its Reynolds stress term, turbulent kinetic energy equation and dissipation rate equation are as follows:

[0035]

[0036]

[0037]

[0038] Where Gk is the turbulent kinetic energy term generated by the gradient change of the mean velocity; Gb is the turbulent kinetic energy term generated by the influence of buoyancy; YM is the fluctuation caused by excessive dissipation in compressible turbulence; σk and σε represent the Prandtl number corresponding to the turbulent kinetic energy k and the dissipation rate ε, respectively; Sk and Sε are the source terms of k and ε, respectively; C1ε, C2ε, and C3ε are empirical constants; and μt is the turbulent viscosity coefficient.

[0039] According to the above turbulence model, the analysis is performed in solidworks fluid simulation software, and the gas pressure is set to 7 bar. The whole process is that after the gas is fully accelerated in the vortex chamber 110 to generate vortex, a vortex is generated in the vortex tube 100. The external temperature of the vortex is higher than the internal gas temperature. When the vortex encounters the hot end baffle, it generates a reflux and flows to the cold end, and the temperature continues to drop during the flow process. The simulation results are shown in the figure below:

[0040] The highest temperature at the hot end reached 115.48°C, and the lowest temperature at the cold end reached -36.71°C, which was preliminarily consistent with the model estimation.

[0041] It should be noted that before the combined exhaust gas is introduced into the vortex tube 100, in order to prevent large particles in the combined exhaust gas from causing damage to subsequent equipment, in one embodiment, the system further includes a filter element, which is installed at the air inlet 120 of the vortex tube 100 to filter large particles mixed in the exhaust gas. The filter element can be composed of an activated carbon adsorption box with a multi-grid mesh filter, which can adsorb large particles in the introduced combined exhaust gas.

[0042] To facilitate experimental verification, Figure 3The test device shown in the figure includes an air compressor 150, a plurality of flow meters 160, a plurality of thermometers 170 and a plurality of pressure gauges 180. The air compressor 150 can pressurize the combined exhaust gas and send it into the vortex tube 100. The flow meter 160, the thermometer 170 and the pressure gauge 180 can respectively measure the flow rate, temperature and pressure at the inlet and outlet of the vortex tube 100.

[0043] The SCR assembly 200 in this embodiment is connected to the cold end pipe 130 to treat nitrogen oxides. However, the conventional SCR has the problem of ammonia slip when treating NOx and the problem that NOx and NH3 cannot be fully contacted and mixed. Therefore, the present application makes further improvements.

[0044] like Figure 4 As shown, in one embodiment, the SCR component 200 includes a reaction box 210 and a water replenishing member 220, an ammonia replenishing member 230 and a catalyst member 240 which are sequentially arranged along the gas flow direction inside the reaction box 210. The water replenishing member 220 has a water replenishing end for adjusting the ratio between nitrogen monoxide and nitrogen dioxide in nitrogen oxides, the ammonia replenishing member 230 has an ammonia replenishing end for conveying ammonia to the reaction box 210, and the catalyst member 240 catalyzes the decomposition of nitrogen oxides into nitrogen and water.

[0045] The water replenishing member 220 includes a water tank and a first spray pipe built into the reaction box 210, and one end of the first spray pipe is connected to the water tank via a water pump. By adding a distilled water spray module at the outlet of the cold end of the vortex tube 100, nitrogen dioxide reacts with water to generate nitric acid liquid and nitrogen monoxide at the same time, that is, by controlling the spraying amount of distilled water, the ratio of nitrogen monoxide and nitrogen dioxide in nitrogen oxides can be controlled, thereby reducing the ammonia escape rate.

[0046] The ammonia replenishing device 230 includes an ammonia storage box 300 and a solenoid valve 310. The ammonia storage box 300 is connected to the reaction box 210 via the solenoid valve 310. The amount of ammonia input into the reaction box 210 can be controlled by the solenoid valve 310.

[0047] In one embodiment, the system further includes a flow detection module 400 installed on the cold end pipe 130 to detect the gas flow in the cold end pipe 130. At the same time, the system further includes a flow control module 500, which is connected to the flow detection module 400 to receive and process the flow signal of the gas in the cold end pipe, and the flow control module 500 is connected to the ammonia supplement component 230 to control the flow of ammonia gas delivered to the reaction box 210 by the ammonia supplement component 230 according to the flow signal of the gas in the cold end pipe. Among them, the flow detection module 400 can transmit the information such as the flow or temperature detected by it through the host computer 410.

[0048] A flow control module 500 is added to the pipeline for introducing ammonia gas. By detecting the change in the gas flow rate in the cold end pipe 130, the opening and closing degree of the solenoid valve 310 can be adjusted in real time to input a suitable amount of ammonia gas. Ultimately, the amounts of nitric oxide, nitrogen dioxide and ammonia gas in the reaction box 210 can be controlled.

[0049] In the flow control module 500, the control motherboard 510 (such as an STM32 microcontroller) and the flow sensor are used to monitor the gas flow rate in the cold end pipe 130 in real time through serial communication, and the ammonia supply is dynamically adjusted. When the flow rate increases, the system automatically introduces more ammonia to meet the SCR reaction; when the flow rate decreases, the supply is reduced to optimize efficiency.

[0050] In addition, this module design integrates the concept of intelligent industry and integrates the display module, key module and monitoring module. The LCD1602 display module is integrated using the GPIO interface of the STM32 microcontroller to display the flow data in real time; through the key interface, the operator can set the flow threshold by pressing the key and dynamically adjust the monitoring sensitivity. In addition, in the monitoring module, the operator can directly connect to the camera through WIFI and view the monitoring screen on the mobile phone software, providing a basis for precise control and intelligent monitoring.

[0051] Since the gas flow rate at the cold end of the graduated separation module is relatively fast, when the ammonia gas is mixed with the nitrogen oxide gas at the cold end outlet, it cannot be mixed evenly, resulting in a decrease in the reaction efficiency during the subsequent SCR reaction. Therefore, a grid-type guide plate is installed in the pipeline after the two gases are mixed. The two gases are mixed evenly through the grid-type guide plate, ultimately achieving the goal of increasing the reaction rate and reducing the ammonia escape effect.

[0052] The condensation recovery assembly in this embodiment is connected to the hot end pipe 140 to recover volatile organic compounds.

[0053] The condensation recovery component includes a plurality of condensers connected in sequence, and the temperatures in the plurality of condensers are set in steps, which are respectively used to recover volatile organic compounds with different boiling points.

[0054] In one embodiment, the condensation recovery component is designed with a three-stage temperature gradient condensation system to effectively recover volatile organic compounds with different boiling points. The first stage recovers high boiling point and large molecular weight VOCs; the second stage recovers alcohols and esters with high utilization value; the third stage recovers low molecular weight VOCs, achieving efficient separation and collection.

[0055] Specifically, according to theoretical calculations and simulation diagrams, the temperature separation module can heat the hot end airflow to about 130°C. The boiling points of common VOCs components such as butanol, butyl esters, xylene, and propylene glycol methyl ether acetate are all near this temperature. Since the gas introduced into the temperature separation module is high-pressure gas, the boiling points of each substance will decrease by about 5°C when the pressure increases. Therefore, when implementing graded condensation separation at different temperatures, the energy consumption required to change the temperature is less, and good separation and collection effects can be achieved.

[0056] A three-level temperature gradient is set up to realize graded condensation and recovery of volatile organic compounds. The first-level temperature gradient is controlled at t≥130℃ (t is the condensing water temperature), and mainly recovers volatile organic compounds with high boiling points, i.e., larger molecular weights; the second-level temperature gradient is controlled at 90℃≤t<130℃, and mainly recovers volatile organic compounds with higher utilization, such as alcohols and esters; the third-level temperature gradient is controlled at 40℃≤t<90℃, and mainly recovers volatile organic compounds that have not been recovered by the above two temperature gradients, including volatile organic compounds with lower molecular weights.

[0057] Compared with the prior art, the combined high-pressure exhaust gas is introduced into the vortex tube 100, and a vortex is generated in the vortex chamber 110. The gas speed of the inner circle of the vortex will gradually decrease, and the gas speed of the outer circle will gradually increase. The gas in the inner circle transfers the lost kinetic energy to the gas in the outer circle in the form of internal energy, so the gas temperature in the inner circle gradually decreases, and the gas temperature in the outer circle gradually increases. At this time, the volatile organic matter that is easy to liquefy in the inner circle gas will become liquid at a lower temperature. At the same time, because its density is greater than that of nitrogen oxides, it has a tendency to move toward the periphery, while the nitrogen oxides in the periphery have a tendency to move inward. Under the dual effects of temperature and density, the nitrogen oxide gas will gather in the inner circle and be discharged from the cold end tube 130, and the volatile organic matter will gather in the outer circle and be discharged from the hot end tube 140, thereby achieving a separation effect, effectively reducing the energy consumption required for separating the combined exhaust gas. At the same time, the condensation recovery component can collect volatile organic matter, thereby improving the utilization rate of resources.

[0058] The present invention also provides a combined exhaust gas treatment method based on the vortex tube 100, comprising the combined exhaust gas treatment system based on the vortex tube 100 as described above, and further comprising the steps of:

[0059] S100, introducing the combined exhaust gas into the vortex tube 100, and under the effect of temperature difference and density difference, the nitrogen oxides are discharged from the cold end tube 130, and the volatile organic compounds are discharged from the hot end tube 140;

[0060] S200, the SCR assembly 200 processes the nitrogen oxides derived from the cold end pipe 130;

[0061] S300 , the condensation recovery component recovers the volatile organic matter derived from the intermediate heat end pipe 140 .

[0062] Furthermore, the SCR assembly 200 processes the nitrogen oxides derived from the cold end pipe 130, including the following steps:

[0063] S210, mixing distilled water into the nitrogen oxides entering the SCR component 200 to adjust the ratio between nitrogen monoxide and nitrogen dioxide in the nitrogen oxides;

[0064] S220, introducing ammonia gas and decomposing it under the catalysis of a catalyst to generate nitrogen gas and water.

[0065] Furthermore, the condensation recovery component realizes temperature step recovery according to the boiling points of different substances in the volatile organic compounds.

[0066] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A combined exhaust gas treatment system, characterized in that: include: A vortex tube, which has a vortex chamber inside and is formed with an air inlet connected to the vortex chamber, so that the exhaust gas introduced from the air inlet forms a vortex in the vortex chamber, and also includes a hot end tube and a cold end tube coaxial with and connected to the vortex chamber, the inner diameter of the cold end tube is smaller than the inner diameter of the hot end tube, and the inner diameter of the hot end tube is smaller than the inner diameter of the vortex chamber, under the action of temperature difference and density difference, nitrogen oxides are discharged from the cold end tube, and volatile organic compounds are discharged from the hot end tube; An SCR component, which is in communication with the cold end pipe and is used to treat nitrogen oxides; A condensation recovery component, which is in communication with the hot end pipe and is used to recover volatile organic compounds; The SCR component comprises a reaction box, and a water supply component, an ammonia supply component and a catalyst component sequentially arranged along the gas flow direction inside the reaction box, wherein the water supply component has a water supply end for adjusting the ratio between nitrogen monoxide and nitrogen dioxide in nitrogen oxides, the ammonia supply component has an ammonia supply end for conveying ammonia to the reaction box, and the catalyst component catalyzes the decomposition of nitrogen oxides into nitrogen and water; The system also includes a flow detection module installed on the cold end pipe, for detecting the gas flow in the cold end pipe; The system also includes a flow control module, which is connected to the flow detection module to receive and process the flow signal of the gas in the cold end tube. The flow control module is connected to the ammonia replenishing component to control the flow of ammonia delivered to the reaction box by the ammonia replenishing component according to the flow signal of the gas in the cold end tube.

2. The combined exhaust gas treatment system according to claim 1, characterized in that: The water replenishing member includes a water tank and a first spray pipe built into the reaction tank, and one end of the first spray pipe is connected to the water tank via a water pump; The ammonia replenishing component includes an ammonia storage box and a solenoid valve, and the ammonia storage box is connected to the reaction box via the solenoid valve.

3. The combined exhaust gas treatment system according to claim 1, characterized in that: The condensation recovery component comprises a plurality of condensers connected in sequence, and the temperatures in the plurality of condensers are set in steps, respectively used for recovering volatile organic compounds with different boiling points.

4. The combined exhaust gas treatment system according to claim 1, characterized in that: It also includes a filter element, which is installed at the air inlet of the vortex tube and is used to filter large particles mixed in the exhaust gas.

5. A combined waste gas treatment method, characterized in that: The combined exhaust gas treatment system according to any one of claims 1 to 4 further comprises the steps of: The combined exhaust gas is introduced into the vortex tube. Under the effect of temperature difference and density difference, nitrogen oxides are discharged from the cold end tube and volatile organic compounds are discharged from the hot end tube. The SCR component processes nitrogen oxides derived from the cold end pipe; The condensation recovery component recovers the volatile organic matter derived from the medium heat end pipe.

6. The combined exhaust gas treatment method according to claim 5, characterized in that: The SCR assembly processes the nitrogen oxides derived from the cold end pipe and comprises the following steps: Mixing distilled water into the nitrogen oxides entering the SCR component to adjust the ratio between nitrogen monoxide and nitrogen dioxide in the nitrogen oxides; Ammonia gas is introduced and decomposed by a catalyst to produce nitrogen gas and water.

7. The combined exhaust gas treatment method according to claim 5, characterized in that: The condensation recovery component realizes temperature step recovery according to the boiling points of different substances in the volatile organic matter.

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