An improved catalytic combustion device

Abstract

The present invention discloses an improved catalytic combustion device, belonging to the technical field of organic waste liquid and waste gas purification. The hydrogen-containing tail gas is sent into the gas holder through the intake mechanism and then enters the catalytic combustion device through the outlet mechanism; the liquid fuel methanol and the methanol-to-hydrogen residual liquid are quantitatively pressurized by the metering pump and then enter the vaporizer together with nitrogen from the upper opening, are heated and vaporized by exchanging heat with the flue gas, and flow into the catalytic combustion device by gravity; the air is quantitatively pressurized by the Roots blower, enters the catalytic combustion device after being heated and exchanged heat with the flue gas through the heat exchanger; the above three streams enter the catalytic combustion device, and the flue gas after sufficient reaction passes through the heat exchanger and the vaporizer in sequence and then is discharged; the reaction heat of the catalytic combustion device is taken out by heating the heat transfer oil flowing in the heat exchange tubes of the first-stage catalytic combustion reaction section, and the second-stage catalytic combustion reaction section is an adiabatic fixed-bed catalytic combustion reaction device, which can purify and treat the methanol-to-hydrogen residual liquid and waste gas.

Description

Technical Field

[0001] The present invention relates to the technical field of purification of organic waste liquid and waste gas, and particularly to an improved catalytic combustion device. Background Art

[0002] Methanol and water vapor pass through a catalyst under certain temperature and pressure conditions. Under the action of the catalyst, a methanol cracking reaction and a carbon monoxide shift reaction occur, generating hydrogen and carbon dioxide. This is a multi-component and multi-reaction gas-solid catalytic reaction system. The reaction equations are as follows:

[0003] CH3OH → CO + 2H2

[0004] H2O + CO → CO2 + H2

[0005] CH3OH + H2O → CO2 + 3H2

[0006] The H2 and CO2 generated by the reforming reaction are then separated by pressure swing adsorption (PSA) to obtain high-purity hydrogen. The remaining tail gas (mainly containing hydrogen, carbon dioxide, trace methanol, and a small amount of carbon monoxide) needs to be discharged. At the same time, the subsequent hydrogen-using process equipment will also discharge more or less excess hydrogen containing a large amount of VOCs substances.

[0007] With the country's emphasis on air pollution control, most regions in China can no longer accept the direct emission of the above gases into the atmosphere. The organic substances and carbon monoxide need to be purified before being discharged. The treatment process is cumbersome and complex, and it will also generate waste liquid and solid waste with secondary pollution.

[0008] In the existing methanol steam reforming technology for hydrogen production, since the raw material water is in excess, a large amount of water-containing residual liquid will be generated during the separation of the reformed gas. At the same time, certain side reactions will inevitably occur in the methanol steam reforming reaction, and there will also be impurities in the methanol raw material. These impurities are present in the above residual liquid. If all are returned as feed, they will accumulate in the system, thereby poisoning the methanol steam reforming catalyst and shortening its service life. Therefore, the impurity concentration in the reaction system cannot be very high, and the residual liquid must be quantitatively discharged outside the reactor. If directly discharged, it will cause environmental pollution.

[0009] In the existing methanol steam reforming hydrogen production technology, the concentration of hydrogen in the tail gas discharged after separating hydrogen by pressure swing adsorption (PSA) varies from 0% to 90% with the discharge flow rate, and it is discontinuous. It needs to be collected and buffered before continuous output. The molecular weight of hydrogen is 2, and the molecular weight of carbon dioxide is 44. When collecting the pressure swing adsorption tail gas in a container, there is an obvious stratification phenomenon. Hydrogen exists at the top of the container, while carbon dioxide is concentrated at the bottom of the container. When it is used as fuel to supply the catalytic combustion reaction, when the hydrogen content is low, less oxygen is consumed. When supplying air at the normal flow rate, oxygen will be enriched in the reactor. When the hydrogen concentration increases, it is extremely easy to form an explosive gas mixture, posing a safety hazard. When the hydrogen content is high, a large amount of oxygen is consumed. When supplying air at the normal flow rate, the reaction in the reactor is incomplete due to the lack of oxygen. Excessive hydrogen reacts with carbon monoxide, methanol, and methane under the action of the catalyst to generate VOCs substances of several hundred or even thousands of ppm, seriously exceeding the environmental protection emission standards. In the existing technology that uses catalytic combustion as a heat source, a large amount of flue gas is usually used for dilution to reduce the oxygen and combustible gas content in the reactor, so that it can operate safely. In this way, the equipment is bulky, the operating efficiency is low, and it is difficult to achieve the purification effect that meets the requirements of environmental protection emission standards. Summary of the Invention

[0010] In view of this, the present invention provides an improved catalytic combustion device, which can be used for the improved purification treatment of methanol hydrogen production residual liquid and waste gas and the heat-conducting oil liquid-phase heating system. It provides a complete purification treatment of methanol hydrogen production residual liquid and waste gas, can meet the requirements of safety and environmental protection supervision, and at the same time provides a heat source for methanol hydrogen production, facilitating independent construction, and thus being more suitable for practical use.

[0011] In order to achieve the above object, the technical solution of the improved catalytic combustion device provided by the present invention is as follows:

[0012] The improved catalytic combustion device provided by the present invention is sequentially provided with a first-stage catalytic combustion reaction section II (6 - 20), a gas circulation driving section (6 - 15), a first-stage catalytic combustion reaction section I (6 - 10), and a second-stage catalytic combustion reaction section (6 - 5) from bottom to top;

[0013] A liquid fuel methanol inlet and a reflux gas inlet are arranged on the gas circulation driving section (6 - 15), and a hydrogen-containing tail gas inlet is arranged at the bottom of the improved catalytic combustion device; the smoke exhaust port of the first-stage catalytic combustion reaction section II (6 - 20) is communicated with the reflux gas inlet on the gas circulation driving section (6 - 15) through a pipeline;

[0014] The second-stage catalytic combustion reaction section (6 - 5) includes a first opening (6 - 1) for discharging flue gas, a second opening (6 - 2) for introducing air, a third opening (6 - 3) for discharging reflux flue gas, a filling mechanism (6 - 4), and a gas guiding mechanism (6 - 6);

[0015] The air guiding mechanism (6-6) is two concentric inner and outer diversion pipes between the second opening (6-2) for introducing air and the third opening (6-3) for discharging the reflux flue gas connected inside the square box of the secondary catalytic combustion reaction section (6-5). The outer diversion pipe has two openings. One of them is connected to the bottom plate opening so that the flue gas discharged from the primary catalytic combustion reaction section I (6-10) is mixed with most of the inlet air, and then it is divided into two streams. One stream is sent to the filling mechanism (6-4) through the other opening of the outer diversion pipe, and after completing the secondary catalytic combustion reaction, it is discharged from the catalytic combustion device (6). The other stream is mixed with a part of the fresh air directly introduced by the inner diversion pipe to increase the oxygen content of the gas at the inlet of the filling mechanism for the primary catalytic combustion reaction. The third opening (6-3) is connected to the reflux gas inlet on the gas circulation driving section (6-15) through a pipeline.

[0016] The improved catalytic combustion device provided by the present invention can also be further realized by adopting the following technical measures.

[0017] Preferably, the primary catalytic combustion reaction section I (6-10) includes a filling mechanism I (6-8) and a heat conduction mechanism I (6-9); the primary catalytic combustion reaction section II (6-20) includes a filling mechanism II (6-18) and a heat conduction mechanism II (6-19);

[0018] The filling mechanism I (6-8) and the filling mechanism II (6-18) are square boxes with open tops and bottoms, and a perforated plate for support and commercially available particulate catalysts with platinum-palladium as the active component for purifying organic waste gas are filled inside the square boxes; the catalytic combustion reaction gas passes through the filling mechanism I (6-8) from bottom to top and passes through the filling mechanism II (6-18) from top to bottom;

[0019] The heat conduction mechanism I (6-9) and the heat conduction mechanism II (6-19) are a group of finned heat exchange tubes connected to the access pipe row and the discharge pipe row. The finned heat exchange tubes are inside the square boxes of the filling mechanism I (6-8) and the filling mechanism II (6-18). Catalysts are filled between the finned heat exchange tubes. The heat conduction oil is distributed to the finned heat exchange tubes through the access pipe row, absorbs the reaction heat and rises in temperature, and then converges to the discharge pipe row to export the reaction heat.

[0020] Preferably, the filling mechanism (6-4) is a closed square box, and a perforated plate for support and commercially available particulate catalysts with platinum-palladium as the active component for purifying organic waste gas are filled in the upper middle part of the square box. The catalytic combustion reaction gas passes through the filling mechanism (6-4) from bottom to top.

[0021] Preferably, the gas circulation driving section (6-15) is a square box with open tops and bottoms. The side plates are provided with openings for installing circulation fans, and there are an upper reflux gas inlet, a lower reflux gas inlet, and a methanol inlet.

[0022] Preferably, the circulation fan (6-16) is a direct-connected fan, which consists of an impeller and a motor.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. By using a floating roof gas holder to collect the intermittently discharged hydrogen-containing waste gas, the gas outlet of the floating roof gas holder comes from the mixed gas at the top and bottom of the container, enabling the hydrogen-containing waste gas to continuously and evenly supply gas to the catalytic combustion device for easy safety control.

[0025] 2. Liquid fuel methanol and the residual liquid from methanol hydrogen production are driven by a nitrogen gas stream through a vaporizer, making it easier to exchange heat and vaporize, ensuring more complete liquid vaporization for the catalytic combustion reaction; the continuously introduced nitrogen gas stream makes the catalytic combustion device operate more safely.

[0026] 3. The catalytic combustion device adopts a series-connected two-stage catalytic combustion reaction structure, which can preferably select catalysts according to different reaction type requirements. While efficiently recovering and supplying heat energy through the catalytic combustion reaction of the residual liquid and waste gas, the flue gas emissions can meet the requirements of on-line VOCs detection.

[0027] 4. By introducing fresh air into the bypass of the connecting pipe, it is convenient to adjust the oxygen content at the inlet of each stage of the two-stage catalytic combustion reaction. With only one air inlet, the whole system is simplified and the operation is more convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0029] Attached Figure 1 is a schematic diagram of the overall structure of the system for purifying the residual liquid from methanol hydrogen production, waste gas, and providing heat by liquid-phase heat transfer oil according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] In view of this, the present invention provides an improved catalytic combustion device, which can be used in an improved system for purifying the residual liquid from methanol hydrogen production, waste gas, and providing heat by liquid-phase heat transfer oil. It provides complete purification of the residual liquid from methanol hydrogen production and waste gas, meets the requirements of safety and environmental protection supervision, and at the same time provides heat source for methanol hydrogen production, facilitating independent construction, and thus being more suitable for practical use.

[0031] To further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details an improved catalytic combustion device proposed according to the present invention, including its specific implementation manners, structures, features, and effects, as follows. In the following description, different "one embodiment" or "embodiments" do not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0032] The term "and / or" in this article is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B is specifically understood as: it can include both A and B at the same time, A can exist alone, or B can exist alone, and it can have any one of the above three situations.

[0033] See the attached Figure 1 , in the methanol-to-hydrogen residue, waste gas purification and treatment, and heat transfer oil liquid-phase heating system provided by the embodiment of the present invention, each reference numeral represents:

[0034] 1. Gas holder - Receives and stores gases, buffers changes in the inlet gas state, and balances the composition and flow rate of the outlet gas. The gas holder 1 has a vertical lifting structure and includes a water tank 1-1 and a floating drum 1-4. The water tank 1-1 is a bottomed and lidless cylinder, with a first opening at its lower part connected to the inlet mechanism 1-2, which is an inlet pipe that passes through the water layer from the outside of the lower part of the water tank to the inside of the water tank and reaches above the water surface and is covered by the floating drum; it has a second opening at its lower part connected to the outlet mechanism 1-3, including a gas guide pipe 1-6 suspended at the top of the floating drum 1-4 and moving together with the floating drum, and an outlet pipe that passes through the water layer from above the water surface of the water tank to the outside of the lower part of the water tank. At the same time, the gas guide pipe 1-6 is always inside the outlet pipe when the floating drum moves up and down, so that the outlet mechanism 1-3 can make the outlet gas a mixed gas from the top and bottom layers of the gas holder in a certain proportion. The floating drum 1-4 is a bottomless and lidless cylinder, with an exhaust mechanism 1-5 provided at its top, which is a gas conduit extending to a position slightly higher than the bottom opening of the floating drum at the bottom of the floating drum. It has an enlarged section with a gas-liquid separation function, and the enlarged section has gas velocity-reducing distribution openings. When the floating drum rises and exposes it above the water surface, the gas holder is filled with gas, and the excess gas is discharged through the exhaust mechanism 1-5.

[0035] 2. Roots blower - Compresses air meteredly, and it is a general mechanical equipment.

[0036] 3. Heat exchanger - Exchanges heat between air and the flue gas discharged from the catalytic combustion device 6 for waste heat recovery.

[0037] 4. Metering pump - Pressurizes liquid fuels such as methanol and methanol-to-hydrogen residue meteredly, and it is a general mechanical equipment.

[0038] 5. Vaporizer - It vaporizes liquid fuels such as methanol and the residue of hydrogen production from methanol by heat exchange with the flue gas that has been cooled by heat exchange with air, and recovers waste heat.

[0039] 6. Catalytic combustion device - The main reactor includes a first-stage catalytic combustion reaction section 6-10, 6-20, a second-stage catalytic combustion reaction section 6-5, and a gas circulation driving section 6-15.

[0040] The first-stage catalytic combustion reaction section I 6-10 and the first-stage catalytic combustion reaction section II 6-20 are isothermal fixed-bed catalytic combustion reactions, mainly for removing hydrogen. The first-stage catalytic combustion reaction section I 6-10 includes a filling mechanism I 6-8 and a heat conduction mechanism I 6-9; the first-stage catalytic combustion reaction section II 6-20 includes a filling mechanism II 6-18 and a heat conduction mechanism II 6-19; the filling mechanisms I 6-8 and II 6-18 are open-top square boxes, and there are perforated plates for support and commercially available granular catalysts with platinum-palladium as the active component for purifying organic waste gas filled inside the square boxes. The catalytic combustion reaction gas passes through the filling mechanism I 6-8 from bottom to top and through the filling mechanism II 6-18 from top to bottom. The heat conduction mechanisms I 6-9 and II 6-19 are a group of finned heat exchange tubes connected to the inlet pipe row and the outlet pipe row. The finned heat exchange tubes are inside the square boxes of the filling mechanisms I 6-8 and II 6-18, and catalysts are filled between the finned heat exchange tubes. The heat transfer oil is distributed to the finned heat exchange tubes through the inlet pipe row, absorbs the reaction heat and heats up, and then converges to the outlet pipe row to export the reaction heat.

[0041] The second-stage catalytic combustion reaction section 6-7 is an adiabatic fixed-bed catalytic combustion reaction, mainly for removing VOCs. The second-stage catalytic combustion reaction section 6-5 includes a first opening 6-1 for discharging flue gas, a second opening 6-2 for introducing air, a third opening 6-3 for discharging the reflux flue gas, a filling mechanism 6-4, and a gas guiding mechanism 6-6; the filling mechanism 6-4 is a closed square box, and there are perforated plates for support in the upper middle part of the square box and commercially available granular catalysts with platinum-palladium as the active component for purifying organic waste gas filled inside. The catalytic combustion reaction gas passes through the filling mechanism 6-4 from bottom to top. The gas guiding mechanism 6-6 is two concentric inner and outer diversion pipes connected between the second opening 6-2 for introducing air and the third opening 6-3 for discharging the reflux flue gas inside the square box of the second-stage catalytic combustion reaction section 6-5. The outer diversion pipe has two openings. One of them is connected to the bottom plate opening so that the flue gas discharged from the first-stage catalytic combustion reaction section I 6-10 is mixed with most of the inlet air, and then it is divided into two streams. One stream is sent to the filling mechanism 6-4 through the other opening of the outer diversion pipe, and after completing the second-stage catalytic combustion reaction, it is discharged from the catalytic combustion device 6. The other stream is mixed with a part of the fresh air directly introduced by the inner diversion pipe to increase the oxygen content of the gas at the inlet of the filling mechanism for the first-stage catalytic combustion reaction.

[0042] The gas circulation drive section 6-15 is an open-top and open-bottom square box. The side plates are provided with openings for installing circulation fans, and there are an upper return gas inlet, a lower return gas inlet, and a methanol inlet. The circulation fan 6-16 is a direct-connected fan, which consists of an impeller and a motor.

[0043] Process description

[0044] The hydrogen-containing tail gas is sent into the gas holder 1 through the air intake mechanism 1-2, and then enters the catalytic combustion device 6 through the air outlet mechanism 1-3.

[0045] The liquid fuel methanol and the methanol hydrogen production residual liquid are quantitatively pressurized by the metering pump 4 and then enter the vaporizer 5 from the upper opening together with nitrogen. After being heated and vaporized by exchanging heat with the flue gas, they flow into the catalytic combustion device 6 by gravity.

[0046] The air is quantitatively pressurized by the Roots blower 2, enters the catalytic combustion device 6 after being heated and its temperature is raised by exchanging heat with the flue gas through the heat exchanger 3.

[0047] The above three streams of materials enter the catalytic combustion device 6. The flue gas after sufficient reaction passes through the heat exchanger 3 and the vaporizer 5 in sequence and then is discharged to the atmosphere.

[0048] The reaction heat of the catalytic combustion device 6 is taken out by heating the heat transfer oil flowing in the heat exchange tubes of the first-stage catalytic combustion reaction section I 6-10 and the first-stage catalytic combustion reaction section 6-20. The second-stage catalytic combustion reaction section 6-5 is an adiabatic fixed-bed catalytic combustion reaction device, which can purify and treat the methanol hydrogen production residual liquid and waste gas.

[0049] One of the technical problems to be solved by the solution is to make the hydrogen-containing tail gas - the pressure swing adsorption desorbed gas of methanol hydrogen production and the tail gas of catalytic hydrogenation reaction - be continuously and stably supplied, including the flow rate and the concentration of combustible gas, with small fluctuations.

[0050] In order to achieve the above purpose, a gas holder is used to realize gas collection and stable discharge.

[0051] One of the functions of the gas holder is to temporarily store the incoming gas. When the incoming gas flow rate is greater than the gas consumption flow rate, the floating roof of the gas holder rises to store the gas. When the incoming gas flow rate is less than the gas consumption flow rate, the floating roof of the gas holder descends to release the gas. The relationship between the intermittent incoming gas flow rate and the continuous outgoing gas flow rate is balanced through the up and down movement of the floating roof of the gas holder.

[0052] The second function of the gas holder is that the gas discharged from the gas holder is respectively from the top and bottom of the floating drum of the gas holder. A guide pipe that can move up and down with the floating drum is inserted into the outlet pipe. By presetting the gap between the guide pipe and the outlet pipe, the gas flow resistance in the guide pipe and between the guide pipe and the outlet pipe is changed, so that the light gas at the top of the floating drum and the heavy gas at the bottom of the floating drum are discharged in a certain proportion, so as to keep the concentration of the combustible gas discharged from the gas holder fluctuating near the average value.

[0053] In addition to the gas inlet and outlet interfaces, the gas holder is also equipped with a safety discharge port after the gas holder is filled with gas to prevent accidents caused by the sliding out of the floating drum.

[0054] The second technical problem to be solved by the solution is to realize heat energy recovery and supply, treat the residual liquid of methanol to hydrogen production, the desorbed gas of pressure swing adsorption, and the tail gas of catalytic hydrogenation, and the finally discharged gas meets the requirements of on-line VOCs detection.

[0055] To achieve the above purpose, a catalytic combustion device is used. The catalytic combustion device is provided with liquid fuel methanol, an inlet for the residual liquid of methanol to hydrogen production, a hydrogen-containing tail gas (methanol to hydrogen production pressure swing adsorption desorbed gas), an inlet for the tail gas of catalytic hydrogenation reaction, an air inlet, and a flue gas outlet after reaction. There are a cold heat transfer oil inlet and a hot heat transfer oil outlet.

[0056] The secondary catalytic combustion process technology is adopted. In the first-stage catalytic combustion reaction section, a constant-temperature fixed-bed catalytic combustion reaction is used, and two groups are arranged in parallel up and down. Each group includes a filling mechanism and a heat conduction mechanism. The filling mechanism is a square box with openings at the top and bottom, and a perforated plate for support and commercially available granular catalysts with platinum-palladium as the active component for organic waste gas purification are filled in the square box. The heat conduction mechanism is a group of finned heat exchange tubes connected to the inlet pipe row and the outlet pipe row. The finned heat exchange tubes are in the square box of the filling mechanism, and the catalysts are filled between the finned heat exchange tubes. The heat transfer oil is distributed to the finned heat exchange tubes through the inlet pipe row to absorb the reaction heat and then flows together to the outlet pipe row to export the reaction heat. The oxygen content is controlled below 8%, and the catalytic combustion reaction is carried out under oxygen-deficient conditions, and the reaction temperature is 150 - 450 °C.

[0057] In the second-stage catalytic combustion reaction section, an adiabatic fixed-bed catalytic combustion reaction is used. After the exhaust gas of the first-stage catalytic combustion reaction section undergoes catalytic combustion reaction, the concentration of combustible gas contained is very low, usually lower than 25% of the lower explosion limit. It is safely mixed with fresh air through a pipeline. After sufficient mixing, a part of it is mixed with fuel, and when necessary, an appropriate amount of fresh air can be supplemented and then sent to the first-stage catalytic combustion reaction section by a circulation fan. The other part of the gas passes through the second-stage catalytic combustion reaction section from bottom to top, the adiabatic fixed catalytic combustion catalyst bed layer, mainly to remove VOCs, so that the gas discharged from the second-stage catalytic combustion reaction meets the requirements of on-line VOCs detection. The oxygen content is controlled above 3%, and the catalytic combustion reaction is carried out under oxygen-rich conditions, and the reaction temperature is 300 - 600 °C.

[0058] The third technical problem to be solved by the solution is efficient waste heat utilization. The exhaust gas of the second-stage catalytic combustion reaction is first used for air preheating, and then enters the chimney from below and is discharged upward. A shell-and-tube heat exchanger is used to strengthen the air preheating to make the temperature of the gas at the inlet of the second-stage catalytic combustion reaction section reach the requirements. Coils are arranged in the chimney for the liquid feed to vaporize from top to bottom in the nitrogen stream, so as to recover waste heat to the greatest extent.

[0059] Although the preferred embodiments of the present invention have been described, additional changes and modifications can be made by those skilled in the art once they learn of the basic creative concept. Therefore, the appended claims are intended to be interpreted to include the preferred embodiments as well as all changes and modifications that fall within the scope of the present invention.

[0060] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. An improved catalytic combustion device, characterized in that, The first-stage catalytic combustion reaction section II (6 - 20), the gas circulation driving section (6 - 15), the first-stage catalytic combustion reaction section I (6 - 10), and the second-stage catalytic combustion reaction section (6 - 5) are sequentially arranged from bottom to top; A liquid fuel methanol inlet and a reflux gas inlet are provided on the gas circulation driving section (6 - 15), and a hydrogen-containing tail gas inlet is provided at the bottom of the improved catalytic combustion device; the smoke exhaust port of the first-stage catalytic combustion reaction section II (6 - 20) is communicated with the reflux gas inlet on the gas circulation driving section (6 - 15) through a pipeline; The second-stage catalytic combustion reaction section (6 - 5) includes a first opening (6 - 1) for discharging flue gas, a second opening (6 - 2) for introducing air, a third opening (6 - 3) for discharging reflux flue gas, a filling mechanism (6 - 4), and a gas guiding mechanism (6 - 6); The gas guiding mechanism (6 - 6) is two concentric inner and outer diversion pipes connected between the second opening (6 - 2) for introducing air and the third opening (6 - 3) for discharging reflux flue gas in the square box of the second-stage catalytic combustion reaction section (6 - 5). The outer diversion pipe has two openings. One of them is connected to the bottom plate opening so that the flue gas discharged from the first-stage catalytic combustion reaction section I (6 - 10) is mixed with most of the inlet air, and then is divided into two streams. One stream is sent to the filling mechanism (6 - 4) through the other opening of the outer diversion pipe and is discharged from the catalytic combustion device (6) after completing the second-stage catalytic combustion reaction. The other stream is mixed with a part of the fresh air directly introduced by the inner diversion pipe to increase the oxygen content of the gas at the inlet of the filling mechanism for the first-stage catalytic combustion reaction. The third opening (6 - 3) is communicated with the reflux gas inlet on the gas circulation driving section (6 - 15) through a pipeline.

2. The improved catalytic combustion device according to claim 1, characterized in that, The first-stage catalytic combustion reaction section I (6 - 10) includes a filling mechanism I (6 - 8) and a heat conduction mechanism I (6 - 9); the first-stage catalytic combustion reaction section II (6 - 20) includes a filling mechanism II (6 - 18) and a heat conduction mechanism II (6 - 19); The filling mechanism I (6 - 8) and the filling mechanism II (6 - 18) are square boxes with open tops and bottoms, and a perforated plate for support and commercially available particulate catalysts with platinum and palladium as active components for purifying organic waste gas are filled in the square boxes; the catalytic combustion reaction gas passes through the filling mechanism I (6 - 8) from bottom to top and passes through the filling mechanism II (6 - 18) from top to bottom; The heat conduction mechanism I (6 - 9) and the heat conduction mechanism II (6 - 19) are a group of finned heat exchange tubes connected to the access pipe row and the discharge pipe row. The finned heat exchange tubes are in the square boxes of the filling mechanism I (6 - 8) and the filling mechanism II (6 - 18). Catalysts are filled between the finned heat exchange tubes. The heat-conducting oil is distributed to the finned heat exchange tubes through the access pipe row, absorbs the reaction heat and rises, and then converges to the discharge pipe row to export the reaction heat.

3. The improved catalytic combustion device according to claim 1, characterized in that, The filling mechanism (6 - 4) is a closed square box, and a perforated plate for support and commercially available particulate catalysts with platinum and palladium as active components for purifying organic waste gas are provided in the upper middle part of the square box. The catalytic combustion reaction gas passes through the filling mechanism (6 - 4) from bottom to top.

4. The improved catalytic combustion device according to claim 1, wherein The gas circulation driving section (6-15) is an open-top and open-bottom square box, with openings on the side plates for installing circulation fans, and an upper return gas inlet, a lower return gas inlet, and a methanol inlet are provided.

5. The improved catalytic combustion device according to claim 4, characterized in that, The circulation fan (6-16) is a direct-connected fan, which consists of an impeller and a motor.

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