Heat storage catalytic combustion furnace for treating VOCs (Volatile Organic Compounds)

Abstract

The invention discloses a heat storage catalytic combustion furnace for VOCs treatment, which comprises an oxidation chamber and three heat storage catalytic chambers, the heat storage catalytic chambers are communicated with an air distribution box for gas inlet and outlet, and a plurality of first guide plates and second guide plates for uniformly dividing gas channels into a plurality of areas are respectively arranged on the gas channels of the air distribution box and the oxidation chamber; a chamfer is arranged at the corner of the oxidation chamber; and the chamfer is a linear chamfer. And the surface of the second guide plate is parallel to the inclined surface of the closest chamfer. The air distribution box is provided with a divergent section with a gas channel gradually widened, and the first flow guide plate is arranged on the divergent section. The gas flow field uniformity in the device operation process can be improved, and then pressure loss is reduced.

Description

Technical Field

[0001] The invention relates to VOCs treatment, and in particular to a heat storage catalytic combustion furnace used for VOCs treatment. Background Art

[0002] VOCs, or volatile organic compounds, refer to organic compounds that have a high saturated vapor pressure (greater than 13.33 Pa), a low boiling point, a small molecular weight, and are easily volatile at room temperature under standard conditions. This substance is one of the main pollutants in the atmosphere.

[0003] As one of the important methods for the treatment of organic waste gas, regenerative catalytic combustion is widely used in engineering due to its high purification rate and heat recovery efficiency. Regenerative catalytic combustion furnace (RCO) has been adopted in many VOCs treatment projects and plays an important role. In the existing RCO, the flow field distribution of medium and high air volume exhaust gas entering the air distribution box is uneven, resulting in low flow velocity when entering the regenerative bed, thereby increasing local resistance and system pressure loss; at the same time, in the rectangular oxidation chamber, due to the uneven flow field distribution, there will also be a problem of large pressure loss. These will lead to low exhaust gas treatment efficiency and large overall pressure loss. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a heat storage catalytic combustion furnace for VOCs treatment that can improve the uniformity of the gas flow field during the operation of the device and thereby reduce the pressure loss.

[0005] Technical solution: To achieve the above-mentioned purpose, a regenerative catalytic combustion furnace for VOCs treatment described in the present invention includes an oxidation chamber and three regenerative catalytic chambers. The regenerative catalytic chambers are connected to an air distribution box for the inlet and outlet of gas. The air distribution box and the oxidation chamber are respectively provided with a plurality of first guide plates and a second guide plate on their gas passages for dividing the gas passages into a plurality of areas; chamfers are provided at the corners of the oxidation chamber.

[0006] Based on the above scheme, by respectively arranging the first guide plate and the second guide plate in the air distribution box and the oxidation chamber, the gas channels in the air distribution box and the oxidation chamber are evenly divided into multiple areas, so that the gas flow field distribution can be more uniform and the turbulence degree can be reduced, which can reduce the pressure loss; and the chamfers at the corners of the oxidation chamber can also guide the airflow direction, making the gas flow field distribution more uniform and also reducing the pressure loss.

[0007] Preferably, the second guide plates are located above the heat storage catalytic chambers on both sides.

[0008] The top of the heat storage catalytic chamber on both sides is equivalent to the two ends of the oxidation chamber. The second guide plate is arranged here, that is, at the two ends of the oxidation chamber. As long as the gas needs to flow in the oxidation chamber, it will inevitably pass through here. Therefore, setting the second guide plate in this way can achieve a better guide effect.

[0009] Preferably, the chamfer angle is 30° to 60°.

[0010] In this angle range, better gas guidance can be achieved.

[0011] Preferably, the chamfer is a linear chamfer.

[0012] Preferably, the surface of the second guide plate is parallel to the inclined surface of the closest chamfer.

[0013] The surface of the second guide plate is parallel to the inclined surface of the closest chamfer so that the guide directions of the two are consistent, thus avoiding turbulence.

[0014] Preferably, the length of the second guide plate is less than half the length of the heat storage catalyst chamber.

[0015] It is an appropriate range that the length of the second guide plate is less than half of the length of the heat storage catalyst chamber. If it is set too long, it is easy to cause turbulence.

[0016] Preferably, the chamfer is an arc-shaped chamfer.

[0017] Preferably, the air distribution box is provided with a gradually expanding section in which the gas passage gradually widens, and the first guide plate is arranged in the gradually expanding section.

[0018] The air distribution box is provided with a gradually expanding section so that the gas can be blown to the heat storage catalyst chamber more evenly. Since the flow direction of the airflow will change after entering the gradually expanding section, the first guide plate is provided here to play a better guiding role.

[0019] Preferably, the heat storage catalyst chamber is provided with a catalyst bed, a support grid and a heat storage bed in sequence from near to far from the oxidation chamber.

[0020] Preferably, the catalytic bed and the heat storage bed are both honeycomb-shaped.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant beneficial effects: by arranging a plurality of first guide plates and second guide plates in the air distribution box and the oxidation chamber to divide the gas channel into a plurality of areas, and by arranging chamfers at the corners of the oxidation chamber, a uniform distribution of the gas flow field is achieved by guiding the gas, thereby reducing gas turbulence, reducing the overall pressure loss of the device, and thereby improving the exhaust gas treatment efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the overall structure of the thermal storage catalytic combustion furnace;

[0023] Figure 2 This is a front cross-sectional view of the thermal storage catalytic combustion furnace;

[0024] Figure 3This is the left view of the thermal storage catalytic combustion furnace;

[0025] Figure 4 This is a schematic diagram of the three-dimensional structure of the heat storage catalytic combustion furnace;

[0026] Figure 5 This is the flow velocity simulation result diagram of the cross section below the regenerative bed in chamber A of the existing regenerative catalytic combustion furnace;

[0027] Figure 6 This is the simulation result diagram of the flow velocity in the section below the regenerative bed in chamber A of the regenerative catalytic combustion furnace;

[0028] Figure 7 This is a simulation result diagram of the flow velocity in the vertical section of the oxidation chamber of the existing thermal storage catalytic combustion furnace;

[0029] Figure 8 This is the simulation result of flow velocity in the vertical section of the oxidation chamber of this thermal storage catalytic combustion furnace. DETAILED DESCRIPTION

[0030] As shown in the figure, a regenerative catalytic combustion furnace for VOCs treatment described in the present invention includes an oxidation chamber 1 and three regenerative catalytic chambers 2. The regenerative catalytic chamber 2 is connected to an air distribution box 3 for the inlet and outlet of gas. The air distribution box 3 and the oxidation chamber 1 are respectively provided with a plurality of first guide plates 4 and second guide plates 5 on their gas passages for dividing the gas passages into a plurality of areas; a chamfer 6 is provided at the corner of the oxidation chamber 1.

[0031] The oxidation chamber 1 is a rectangular columnar structure, and is connected to three heat storage catalytic chambers 2 at the bottom of the oxidation chamber 1. The heat storage catalytic chambers 2 are also rectangular columnar structures. Of course, both can also be other structures; there are corners at the top of the left and right sides of the oxidation chamber 1, and chamfers 6 are set here. The connection between the oxidation chamber 1 and the three heat storage catalytic chambers 2 also has a corner except for the left and right outermost connection, and a chamfer 6 is also set here; in this embodiment, the chamfer 6 adopts a linear chamfer, and a circular chamfer can also be adopted. The angle of the chamfer can be any value between 30° and 60°, such as 30°, 45° and 60°. This embodiment adopts 45°.

[0032] The heat storage catalytic chamber 2 is provided with a catalytic bed 7, a supporting grid 8 and a heat storage bed 9 in sequence from near to far from the oxidation chamber 1. The catalytic bed 7 is filled with a regular precious metal honeycomb catalyst, and the heat storage bed 9 is filled with a regular honeycomb ceramic heat storage body; the inner walls of the heat storage catalytic chamber 2 and the oxidation chamber 1 are both provided with refractory aluminum silicate fibers for heat preservation.

[0033] The bottom of the heat storage catalytic chamber 2 is connected to an air distribution box 3, and the air distribution box 3 is provided with a rectangular column structure at the bottom and an inverted rectangular table-shaped top, that is, the top is gradually expanded, and a plurality of first guide plates 4 are provided in the inverted rectangular table to divide the inverted rectangular table into a plurality of areas. In this embodiment, five first guide plates 4 are used, which are arranged at a circumferential interval of 15°. It should be noted that the overall structure of the air distribution box 3 may be different from that of this embodiment, and the number of the first guide plates 4 may be selected according to actual needs. At least four guide plates may be provided to achieve a better guide effect. The first guide plates 4 may be arranged at a circumferential interval of 15°. The spacing angle is determined by the number and the shape of the area in the air distribution box 3. If the air distribution box 3 is not provided with a gradually expanding section and is a rectangular column structure, then the first guide plates 4 can be arranged in parallel and spaced apart; even the first guide plates 4 can be arranged into a special-shaped structure in conjunction with the air distribution box 3. For example, the first guide plates 4 cover the gradually expanding section and the ordinary rectangular section, then the first guide plates 4 are arranged in a bent shape. No matter how it is arranged, as long as the first guide plates 4 can evenly divide the gas channel in the air distribution box 3 into multiple areas, it will be fine.

[0034] A plurality of second guide plates 5 are provided in the oxidation chamber 1 above the left and right heat storage catalytic chambers 2 to divide the gas channel into a plurality of regions, and the surfaces of the second guide plates 5 on both sides are parallel to the inclined surfaces of the chamfers 6 at the left and right ends of the top of the oxidation chamber 1; in this embodiment, five second guide plates 5 are used, and their length is slightly less than half of the width of the heat storage catalytic chamber 2 in the left and right directions; there are at least four second guide plates 5, and the specific number is selected according to actual needs. Like the first guide plates 4, the shape, number and spacing of the second guide plates 5 can be adjusted according to actual conditions, as long as the gas channel here in the oxidation chamber 1 can be divided into a plurality of regions.

[0035] The air distribution box 3 is provided with an exhaust gas inlet and outlet pipe 3-1 and a back-blowing pipe 3-2. The exhaust gas inlet and outlet pipe 3-1 is connected with the air inlet valve 10 and the air outlet valve 11, and only one of them can be connected with the exhaust gas inlet and outlet pipe 3-1 at the same time; the back-blowing pipe 3-2 is connected with the back-blowing valve 12; the air inlet valve 10, the air outlet valve 11 and the back-blowing valve 12 are all lifting reversing valves including a cylinder and a solenoid valve; the air inlet valve 10 is connected with the air inlet fan 13 through the air inlet pipeline, the air outlet valve 11 is connected with the chimney 14 through the air outlet pipeline, the back-blowing valve 12 is connected with the back-blowing blower 15 through the back-blowing pipeline, and the back-blowing blower 15 is connected with the air outlet pipeline.

[0036] The regenerative catalytic chamber 2 and the air distribution box 3 operate as a whole chamber. For the convenience of description, the three chambers of the regenerative catalytic chamber 2 and the air distribution box 3 are respectively called chamber A, chamber B and chamber C from left to right; the specific working process of the regenerative catalytic combustion furnace is:

[0037] During the startup phase, a heater 16 is provided in the oxidation chamber 1, which may be an electric heater. The heater 16 heats the heat storage bed 9 and the catalyst bed 7 in the heat storage catalyst chamber to the temperature required for the catalytic combustion reaction. During the operation phase, the organic waste gas flows into the air distribution box 3 of chamber A through the air inlet valve 10 of chamber A, is first guided by the first guide plate 4, then undergoes heat exchange with the heated heat storage bed 9 to increase the temperature, and then flows through the support grid 8 to enter the catalyst bed 7 for oxidation reaction. The purified gas flows through the oxidation chamber 1, is guided by the second guide plate 5, and then passes through the catalyst bed 7, the support grid 8 and the heat storage bed 9 of chamber B downward in turn, and finally flows out from the outlet pipe of chamber B through the outlet valve 11 of chamber B. Chamber C is a back-blowing chamber, and the back-blowing air blower 15 extracts a small portion of the purified gas flowing out of Chamber B, and flows into Chamber C from the back-blowing pipe 3-2 through the back-blowing valve 12 of Chamber C, passes upward through the heat storage bed 9, support grid 8 and catalytic bed 7 of Chamber C, flows through the second guide plate 5 of the oxidation chamber 1, and then passes downward from Chamber B through the catalytic bed 7, support grid 8 and heat storage bed 9 of Chamber B in sequence, and also flows out from the outlet pipe of Chamber B. Since the exhaust gas flowing in from Chamber A may not be completely reacted and flow out from Chamber B, a small portion of the exhaust gas may remain in the oxidation chamber 1 or even flow into Chamber C, so the purpose of back-blowing is to blow this part of the organic exhaust gas back into the device, contact and react with the catalytic beds of Chamber C and Chamber B again, and reduce the residual organic gas in the device as much as possible to improve the purification efficiency. The above is the first process, that is, the air inlet valve 10 of Chamber A, the air outlet valve 11 of Chamber B and the back-blowing valve 12 of Chamber C are in the open state, and the other six valves are in the closed state. After this process runs for 90 seconds, it enters the second process and switches the valve opening and closing states. At this time, the air inlet valve 10 of chamber B, the air outlet valve 11 of chamber C and the back-blowing valve 12 of chamber A are in the open state, and the other six valves are in the closed state. The organic waste gas enters from chamber B, flows out from chamber C after reaction, and the back-blowing gas enters from chamber A. After this process runs for 90 seconds, it enters the third process and switches the valve opening and closing states. At this time, the air inlet valve 10 of chamber C, the air outlet valve 11 of chamber A and the back-blowing valve 12 of chamber B are in the open state, and the other six valves are in the closed state. The organic waste gas enters from chamber C, flows out from chamber A after reaction, and the back-blowing gas enters from chamber B. These three processes are one cycle, a total of 270 seconds, and the cycle works reciprocatingly.

[0038] In order to verify the effective effect of setting guide plates and chamfers on the thermal storage catalytic combustion furnace, the original equipment without guide plates and chamfers was compared and simulated and verified using Ansys Fluent software based on computational fluid dynamics (CFD); specifically:

[0039] Taking the first process in the cycle as an example, the exhaust gas enters from chamber A, flows out from chamber B after purification, and the backwash gas enters from chamber C. The main boundary conditions are set in Ansys Fluent software as follows: The organic exhaust gas flow rate is 5000m 3 / h, the back-blowing air flow rate is 10% of that, i.e. 500m3 / h, given the diameters of the two pipes, the inlet velocity of the air flow is calculated to be 7.1m / s, the purge port velocity is 12.3m / s, the outlet is a standard atmospheric pressure, the thermal storage bed is made of mullite, and the catalytic bed is made of cordierite. Both are porous media models and the air flow in them is laminar. The Realizable k-ε model is selected as the flow model for other places.

[0040] Verification 1:

[0041] Take a section 50mm below the bottom of the heat storage bed in room A, observe the cross-sectional wind speed, and take the surface integral average. The results are as follows: Figure 5 , Figure 6 As shown, it was found that the cross-sectional wind speed of the airflow in the original equipment before entering the heat storage bed was 2.98m / s, while that of the equipment with improved structure was 3.24m / s.

[0042] The turbulent kinetic energy of the cross section was observed in the same way, and the surface integral average was taken. It was found that the turbulent kinetic energy of the airflow in the original equipment before entering the heat storage bed was 2.15m 2 / s 2 , and the turbulent kinetic energy of the equipment after structural improvement is 1.36m 2 / s 2 , the value decreases, indicating that the turbulence level is weakened and the flow field distribution is more uniform.

[0043] By observing the pressure difference between the section and the gas inlet and taking the surface integral average, it was found that the inlet pressure in the original equipment was 718.10Pa, the section pressure was 700.89Pa, and the pressure difference was 17.21Pa. The pressure difference in the equipment with structural improvement was 5.29Pa. Therefore, the pressure loss was reduced after the structural improvement.

[0044] Verification 2:

[0045] Take a vertical section of oxidation chamber 1 and observe the velocity of the section. Figure 7 , Figure 8 As shown in the figure, it is found that the maximum velocity of the section in the original device is 2.34m / s, and the maximum velocity of the section after the structure improvement is 2.80m / s, while the turbulent kinetic energy is increased from 0.086m / s in the original device. 2 / s 2 Reduced to the improved 0.022m 2 / s 2 , indicating that the turbulence level in oxidation chamber 1 is weakened and the flow field distribution is more uniform.

[0046] The top sections of the catalyst bed 7 in chamber A and chamber B were taken respectively, that is, the pressure difference between the inlet section and the outlet section of the oxidation chamber was observed. It was found that the pressure difference in the original equipment was 1.61Pa, and the pressure difference after the structure was improved was 1.15Pa. It can be seen that the pressure loss was reduced after the structure was improved.

[0047] In summary, the improved equipment has a better flow field distribution, which improves the exhaust gas treatment efficiency. At the same time, the reduction in pressure loss can also reduce overall energy consumption.

Claims

1. A regenerative catalytic combustion furnace for VOCs treatment, comprising an oxidation chamber (1) and three regenerative catalytic chambers (2), characterized in that: The heat storage catalytic chamber (2) is connected to an air distribution box (3) for the inlet and outlet of gas. The air distribution box (3) and the oxidation chamber (1) are respectively provided with a plurality of first guide plates (4) and a second guide plate (5) on their gas passages for evenly dividing the gas passages into a plurality of regions. The oxidation chamber (1) is provided with a chamfer (6) at a corner.

2. A regenerative catalytic combustion furnace for VOCs treatment according to claim 1, characterized in that: The second guide plates (5) are located above the heat storage catalytic chambers (2) on both sides.

3. The regenerative catalytic combustion furnace for VOCs treatment according to claim 1, characterized in that: The angle of the chamfer (6) is 30° to 60°.

4. A regenerative catalytic combustion furnace for VOCs treatment according to claim 3, characterized in that: The chamfer (6) is a linear chamfer.

5. A regenerative catalytic combustion furnace for VOCs treatment according to claim 4, characterized in that: The surface of the second guide plate (5) is parallel to the inclined surface of the closest chamfer (6).

6. A regenerative catalytic combustion furnace for VOCs treatment according to claim 5, characterized in that: The length of the second guide plate (5) is less than half the length of the heat storage catalytic chamber (2).

7. The regenerative catalytic combustion furnace for VOCs treatment according to claim 3 is characterized in that: The chamfer (6) is an arc-shaped chamfer.

8. The regenerative catalytic combustion furnace for VOCs treatment according to claim 1, characterized in that: The air distribution box (3) is provided with a gradually expanding section in which the gas passage gradually widens, and the first guide plate (4) is arranged in the gradually expanding section.

9. The regenerative catalytic combustion furnace for VOCs treatment according to claim 1, characterized in that: There are no less than four of each of the first guide plates (4) and the second guide plates (5).

10. The regenerative catalytic combustion furnace for VOCs treatment according to claim 1, characterized in that: The heat storage catalytic chamber (2) is provided with a catalytic bed (7), a supporting grid (8) and a heat storage bed (9) in order from near to far from the oxidation chamber (1).

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