Micro-molecular alkane VOCs catalytic oxidation device and method capable of regenerating and desorbing

Abstract

The invention discloses a micromolecular alkane VOCs catalytic oxidation device and method capable of regenerating and desorbing, and belongs to the technical field of VOCs control. The device adopts a U-shaped flue, and is sequentially provided with a high-temperature flue gas heat exchange module, an integral catalyst and a noble metal catalysis plate module along a flue gas flow. The method comprises the following steps: preheating inlet VOCs through high-temperature flue gas heat exchange, carrying out primary catalytic oxidation by using an integral catalyst, carrying out heat exchange and temperature regulation, and then entering a noble metal catalytic plate module for deep catalytic oxidation; and in-situ regeneration and catalytic activity recovery of the noble metal catalytic plate are realized in a microwave-assisted air regeneration manner. According to the invention, high-efficiency, stable and energy-saving removal of micromolecular alkane VOCs can be realized, and the problem of deactivation of a noble metal catalyst caused by carbon deposition and sintering is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of VOCs pollution control technology, and relates to a regenerative desorption device and method for the catalytic oxidation of small molecule alkane VOCs. Background Technology

[0002] In the petrochemical industry, many refineries and ethylene cracking units emit large amounts of VOCs waste gas with a wide concentration range, which easily leads to high thermal conversion temperatures, uneven temperature distribution, local overheating, and high-temperature sintering within the catalyst. The proportion of small-molecule alkanes in their VOCs waste gas is high. Compared to other types of VOCs (such as aromatic hydrocarbons, oxygen-containing VOCs, and halogenated hydrocarbons), small-molecule alkanes (such as methane, ethane, propane, and n-hexane) are the most difficult to oxidize in terms of reactivity, and usually rely on noble metals (Pt, Pd) or transition metal oxides (MnOx, CoOx) to activate the CH bonds. This results in the following difficulties in the removal of small-molecule alkane VOCs: (1) the need for strong oxidizing active sites; (2) poor low-temperature activity; and (3) incomplete oxidation of alkanes easily leads to carbon deactivation on the catalyst surface. Therefore, efficient removal of small-molecule alkane VOCs requires accelerating the breaking of CH bonds.

[0003] Regenerative catalytic combustion (RCO) can oxidize VOCs into CO2 and H2O at relatively low temperatures (250-400℃), avoiding high-temperature thermal combustion (requiring temperatures above 800℃). In traditional RCOs, the monolithic catalysts for transition metal and precious metal VOCs suffer sintering damage, and frequent replacements lead to high maintenance and downtime costs. Therefore, reducing the frequency of replacements, decreasing the size of the monolithic catalysts used for replacement, and achieving catalyst regeneration not only reduce catalyst usage costs but also minimize losses due to downtime. Currently, improving the catalytic performance of small molecule alkane VOCs and enhancing catalysts mainly focuses on catalyst modification, preparation, and updating heating methods. Therefore, it is necessary to achieve uniform, efficient, and long-life catalytic oxidation across a wide range of VOC concentrations from the perspective of overall system design, while simultaneously saving costs. Summary of the Invention

[0004] The purpose of this invention is to provide a regenerable desorption device and method for the catalytic oxidation of small molecule alkane VOCs, in order to solve a series of problems in the prior art, such as uneven temperature distribution under a wide range of VOC concentrations, catalyst sintering caused by local runaway, and carbon buildup and blockage, thereby improving the stability and reliability of the VOCs catalytic oxidation device under operating conditions.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A regenerative desorption catalytic oxidation device for small molecule alkane VOCs includes: a U-shaped flue having an inlet side and a catalytic side that are interconnected;

[0007] The top of the inlet side is provided with a VOCs inlet flue, and the bottom of the inlet side is provided with a high-temperature flue gas inlet flue.

[0008] The catalytic side is provided with an integral catalyst module, a high-low temperature flue gas heat exchange module, a precious metal catalytic plate module and a VOCs outlet flue in sequence along the flue gas flow direction;

[0009] The high-low temperature flue gas heat exchange module includes a heat exchange flue and a first butterfly valve; the inlet and outlet ends of the heat exchange flue are both connected to the catalytic side, and the tube body is inserted inside the inlet side; the first butterfly valve is located on the catalytic side and between the inlet and outlet ends of the heat exchange flue (21), and is used to control the airflow through the heat exchange flue.

[0010] Furthermore, it also includes a circulating fan and a hot air furnace. The circulating fan is located at the rear end of the VOCs outlet flue, the inlet of the hot air furnace is connected to the outlet of the circulating fan, and the outlet of the hot air furnace is connected to the high-temperature flue gas inlet flue.

[0011] Furthermore, the precious metal catalyst plate module includes at least two independent catalyst chambers, each catalyst chamber is equipped with a precious metal catalyst plate, and the precious metal catalyst plate is equipped with a rotating shaft.

[0012] Furthermore, the inlet end of the catalytic chamber is provided with a second butterfly valve, the side wall of the chamber is provided with an air inlet pipe, and a microwave radiation generator is located on the side of the precious metal catalytic plate.

[0013] Furthermore, the high-low temperature flue gas heat exchange module is configured with multi-stage heat exchange flue pipes and corresponding first butterfly valve structures. By adjusting the opening and closing state of the first butterfly valves at each stage, the number of heat exchange flue pipes through which the flue gas flows can be controlled.

[0014] Furthermore, the pore size and / or flow channel cross-sectional area of ​​the precious metal catalyst plate gradually decrease along the flue gas flow direction.

[0015] Furthermore, the catalyst of the noble metal catalyst plate contains at least one of platinum and palladium; the catalyst of the integral catalyst module is a transition oxide catalyst.

[0016] Furthermore, the power of the microwave radiation generator is 200W to 800W, and the power is adjustable.

[0017] A method for the regenerative desorption of small molecule alkane VOCs using the above-mentioned apparatus includes the following steps:

[0018] S1: VOCs flue gas containing small molecule alkanes enters the device through the VOCs inlet flue, while high-temperature flue gas generated by the hot blast stove enters the device through the high-temperature flue gas inlet flue. In the high-low temperature flue gas heat exchange module, VOCs flue gas and high-temperature flue gas exchange and preheat each other. Through flue gas mixing, the temperature of VOCs flue gas reaches the working temperature of the integrated catalyst module.

[0019] S2: The preheated flue gas flows through the integrated catalyst module for primary catalytic oxidation;

[0020] S3: By controlling the first butterfly valve, the high-temperature flue gas after primary oxidation selectively flows through the heat exchange flue to exchange heat with the low-temperature flue gas on the inlet side, and after cooling, it enters the precious metal catalytic plate module for secondary catalytic oxidation.

[0021] Furthermore, when the precious metal catalytic plate needs to be regenerated, for the target catalytic chamber in the precious metal catalytic plate module, the second butterfly valve at the inlet end is closed, air is introduced through the air inlet pipe, the microwave radiation generator is started and the precious metal catalytic plate is driven to rotate for in-situ regeneration; after the regeneration is completed, the catalytic chamber is restored to operation.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The device of the present invention can be used to improve the catalytic effect and service life of the catalyst. First, a two-stage catalytic system is adopted, which combines an integral catalyst (handling most of the load) with a precious metal catalytic plate (deep purification) to achieve efficient removal of small molecule alkanes and reduce catalyst costs. Second, through the U-shaped layout and adjustable heat exchange module, the heat of reaction is efficiently recovered for preheating the raw gas, and the purified flue gas is used for combustion assistance, which significantly reduces the energy consumption of the system operation.

[0024] (2) In the case of sintering and carbon blockage of the precious metal catalyst plate, the present invention can improve the microwave regeneration effect by rotating the precious metal catalyst plate. Moreover, the regeneration of a single precious metal catalyst chamber does not affect the online operation of the entire device for VOCs catalysis, thereby reducing operating costs and downtime expenses. The modular design and multi-stage controllable heat exchange and regeneration units enable the device to adapt to the VOCs treatment needs of different concentrations and air volumes, and provide high operational flexibility. Attached Figure Description

[0025] Figure 1 This is a front view of a regenerative desorption catalytic oxidation device for small molecule alkane VOCs in an embodiment of the present invention.

[0026] Figure 2 This is a side view of a regenerative desorption catalytic oxidation device for small molecule alkane VOCs in an embodiment of the present invention.

[0027] Figure 3This is an enlarged view of the noble metal catalyst plate and rotating shaft structure of a regenerative desorption catalytic oxidation device for small molecule alkane VOCs in an embodiment of the present invention.

[0028] Wherein: 1 is the VOCs inlet flue; 2 is the high-low temperature flue gas heat exchange module; 21 is the heat exchange flue pipe; 22 is the first butterfly valve; 3 is the high temperature flue gas inlet flue; 4 is the integrated catalyst module; 5 is the precious metal catalyst plate module; 51 is the second butterfly valve; 52 is the air inlet pipe; 53 is the microwave radiation generator; 54 is the precious metal catalyst plate; 55 is the rotating shaft; 6 is the VOCs outlet flue. Detailed Implementation

[0029] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly, provided that there is no mutual conflict.

[0030] Example 1

[0031] like Figure 1 , 2 Figure 3 shows a regenerative desorption catalytic oxidation device for small molecule alkane VOCs provided by the present invention. The structure and connection method of each component are described in detail below.

[0032] A regenerative desorption catalytic oxidation device for small-molecule alkane VOCs includes: a U-shaped flue having an inlet side and a catalytic side that are interconnected. A VOCs inlet flue 1 is located at the top of the inlet side, and a high-temperature flue gas inlet flue 3 is located at the bottom of the inlet side. Along the flue gas flow direction, the catalytic side is sequentially provided with an integral catalyst module 4, a high-low temperature flue gas heat exchange module 2, a precious metal catalytic plate module 5, and a VOCs outlet flue 6. Specifically, the integral catalyst module 4 is located below the catalytic side and downstream of the high-temperature flue gas inlet flue 3.

[0033] In one specific embodiment of the present invention, the high-low temperature flue gas heat exchange module 2 is disposed above the integral catalyst module 4, and includes a heat exchange flue pipe 21 and a first butterfly valve 22. The inlet and outlet ends of the heat exchange flue pipe 21 are both connected to the catalytic side, and the pipe body is partially inserted into the inlet side. The first butterfly valve 22 is disposed on the catalytic side, with the inlet end of the heat exchange flue pipe 21 located upstream of the first butterfly valve 22 and the outlet end located downstream of the first butterfly valve 22. The first butterfly valve is used to control the airflow through or bypass the heat exchange flue pipe 21. Further, the flue pipe on the catalytic side of the high-low temperature flue gas heat exchange module 2 has a square-to-circular-to-square structure, and the first butterfly valve 22 is disposed within this circular pipe section to cut off or open the flow path. When the first butterfly valve 22 is open, the flow resistance of the catalytic side flue gas pipe is much smaller than that of the heat exchange flue pipe 21, and the flue gas flows through the butterfly valve 22 instead of the heat exchange flue pipe 21.

[0034] Preferably, the high-low temperature flue gas heat exchange module 2 is configured with a multi-stage heat exchange flue pipe 21 and a corresponding first butterfly valve 22. By adjusting the opening and closing state of the first butterfly valve 22 at each stage, the number of heat exchange flue pipes through which the flue gas flows can be controlled, thereby controlling the temperature of the flue gas and adjusting the temperature of the flue gas entering the precious metal catalytic plate module 5 to its optimal catalytic activity temperature range. The heat exchange flue pipes 21 can be arranged in multiple columns and rows, and the heat exchange flue pipes can be bent and twisted on the inlet side to increase the heat exchange area.

[0035] In one specific embodiment of the present invention, the precious metal catalytic plate module 5 is disposed above the high-low temperature flue gas heat exchange module 2 for deep purification of the flue gas after primary catalysis. This module includes at least two independent catalytic chambers. Each catalytic chamber can operate independently or switch to a regeneration state, thereby enabling catalyst regeneration without shutdown and ensuring the continuity of device operation. The catalytic chambers are arranged in parallel along the flue gas flow direction, with their inlet ends connected to the outlet of the upstream heat exchange module, and their outlet ends converging to lead to the VOCs outlet flue duct 6.

[0036] Furthermore, each catalytic chamber mainly includes: a precious metal catalytic plate 54, a rotating shaft 55, a second butterfly valve 51, an air inlet pipe 52, and a microwave radiation generator 53. The precious metal catalytic plate 54 is a multi-layered flat or corrugated plate structure, fixed at intervals within the catalytic chamber, and is the core component for deep catalytic oxidation of VOCs. The rotating shaft 55 passes through the center of the precious metal catalytic plate 54 and is used to drive the entire catalytic plate to rotate under external force. Rotating the shaft increases the exposure area of ​​the catalytic plate under microwaves. The second butterfly valve 51 is located in the inlet flue of the catalytic chamber and is used to cut off or guide the flue gas flowing into the catalytic chamber. The air inlet pipe 52 is located on the side wall of the chamber between the second butterfly valve and the precious metal catalytic plate, and is equipped with a shut-off valve for introducing air into the chamber during the regeneration stage. The microwave radiation generators 53 are arranged in pairs on both sides of the precious metal catalytic plate 54 and are used to emit microwaves during the regeneration stage to heat the catalytic plate to burn off carbon deposits or sulfides to achieve regeneration. Furthermore, when the flue gas temperature is low after preheating, the precious metal catalytic plate 54 can be heated by means of microwave or other methods to achieve efficient catalysis.

[0037] Furthermore, the number of the precious metal catalyst plates 54 can be modularly expanded and flexibly increased or decreased according to the VOCs concentration, and the pore size of the precious metal catalyst plates 54 gradually decreases along the flow direction. The precious metal catalyst plates 54 use highly active catalysts such as platinum (Pt) and palladium (Pd) (ignition temperature 200–300℃), and the cross-sectional area of ​​the flow channels of different precious metal catalyst plates gradually decreases along the flow direction.

[0038] Furthermore, the monolithic catalyst 4 is a transition oxide catalyst such as copper manganese oxide (Cu-Mn-O, V2O5-WO3 / TiO2, etc.).

[0039] Furthermore, the rotating shaft 55 of the precious metal catalytic plate 54 in each catalytic chamber passes through the wall of the catalytic side and is connected by a chain gear to realize the synchronous rotation and closing of the precious metal catalytic plate 54 in each catalytic chamber.

[0040] Furthermore, the power of the microwave radiation generator 53 is 200W to 800W, and the power can be dynamically adjusted according to the amount of carbon deposited on the catalyst.

[0041] In one specific embodiment of the present invention, the catalytic oxidation device further includes a circulating fan and a hot air furnace. The circulating fan is located at the rear end of the VOCs outlet flue 6 to provide suction for the entire device. The inlet of the hot air furnace is connected to the outlet of the circulating fan, and the outlet of the hot air furnace is connected to the high-temperature flue gas inlet flue 3.

[0042] Example 2

[0043] A method for the catalytic oxidation of small molecule alkane VOCs with regenerative desorption using the apparatus described in Example 1 includes the following steps:

[0044] S1: Under the action of the circulating fan, VOCs flue gas containing small molecule alkanes enters the device through VOCs inlet flue 1. At the same time, high-temperature flue gas generated by the hot air furnace enters the device through high-temperature flue gas inlet flue. In the high-low temperature flue gas heat exchange module 2, it exchanges heat with the high-temperature flue gas from the high-temperature flue gas inlet flue 3 to preheat the VOCs flue gas temperature to reach the working temperature of the integrated catalyst module.

[0045] S2: The preheated flue gas flows through the integral catalyst module 4 for primary catalytic oxidation;

[0046] S3: By controlling the first butterfly valve 22, the high-temperature flue gas after primary oxidation selectively flows through the heat exchange flue pipe 21 to exchange heat with the low-temperature flue gas on the inlet side, and cools down to the working temperature of the precious metal catalytic plate module. Then, it enters the precious metal catalytic plate module 5 for secondary catalytic oxidation. The purified flue gas is partially sent to the hot air furnace as combustion gas by the circulating fan.

[0047] When the activity of the precious metal catalyst plate decreases due to carbon buildup or sintering, for the target catalyst chamber in the precious metal catalyst plate module 5, the second butterfly valve at the inlet end is closed, the air inlet pipe is opened to introduce air, the rotating shaft is driven to rotate the catalyst plate, and the microwave radiation generator is started to regenerate the catalyst plate; after the regeneration is completed, the air inlet pipe is closed and the second butterfly valve is opened to restore the operation of the catalyst chamber.

[0048] The principle of this invention is as follows:

[0049] For stationary monolithic VOCs catalysts, sintering and localized temperature runaway occur during catalytic use, leading to more uneven gas flow distribution. This further exacerbates the temperature runaway of the monolithic catalyst, inhibits its catalytic effect, and reduces its service life. This invention employs microwave regeneration of precious metal catalysts. By rotating the precious metal catalyst plates, the exposed area is increased, improving the desorption and combustion efficiency and extending the catalyst's service life. Through multiple precious metal catalyst plates with gradually decreasing pore sizes, turbulence is generated in the gaps between the catalyst plates as the exhaust gas flows through them, ensuring uniform gas flow to the next catalyst plate and a uniform temperature distribution across the plates.

[0050] The above-described embodiments are merely specific implementations of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make other different attempts based on the present invention. All changes or substitutions made without inventive effort resulting from the present invention are covered within the scope of protection of the present invention.

Claims

1. A regenerative desorption catalytic oxidation device for small molecule alkane VOCs, characterized in that, include: The U-shaped flue has an inlet side and a catalytic side that are interconnected. The top of the inlet side is provided with a VOCs inlet flue (1), and the bottom of the inlet side is provided with a high-temperature flue gas inlet flue (3). The catalyst side is provided with an integral catalyst module (4), a high-low temperature flue gas heat exchange module (2), a precious metal catalyst plate module (5) and a VOCs outlet flue (6) in sequence along the flue gas flow direction. The high-low temperature flue gas heat exchange module (2) includes a heat exchange flue (21) and a first butterfly valve (22); the inlet and outlet ends of the heat exchange flue (21) are connected to the catalytic side, and the tube body is inserted into the inlet side; the first butterfly valve (22) is located on the catalytic side and is used to control the airflow to flow through the heat exchange flue (21) or bypass the heat exchange flue (21).

2. The regenerative desorption catalytic oxidation device for small molecule alkane VOCs according to claim 1, characterized in that, It also includes a circulating fan and a hot air furnace. The circulating fan is located at the rear end of the VOCs outlet flue (6). The inlet of the hot air furnace is connected to the outlet of the circulating fan, and the outlet of the hot air furnace is connected to the high-temperature flue gas inlet flue (3).

3. The regenerative desorption catalytic oxidation device for small molecule alkane VOCs according to claim 1, characterized in that, The precious metal catalyst plate module (5) includes at least two independent catalyst chambers, each of which is provided with a precious metal catalyst plate (54), and the precious metal catalyst plate (54) is provided with a rotating shaft (55).

4. The regenerative desorption catalytic oxidation device for small molecule alkane VOCs according to claim 3, characterized in that, The inlet end of the catalytic chamber is provided with a second butterfly valve (51), the side wall of the chamber is provided with an air inlet pipe (52), and the side of the precious metal catalytic plate (54) is provided with a microwave radiation generator (53).

5. The regenerative desorption catalytic oxidation device for small molecule alkane VOCs according to claim 1, characterized in that, The high-low temperature flue gas heat exchange module (2) is configured with a multi-stage heat exchange flue pipe (21) and a corresponding first butterfly valve (22). The number of heat exchange flue pipes through which the flue gas flows can be controlled by adjusting the opening and closing state of the first butterfly valve (22) at each stage.

6. The regenerative desorption catalytic oxidation device for small molecule alkane VOCs according to claim 3, characterized in that, The aperture and / or flow channel cross-sectional area of ​​the precious metal catalyst plate (54) gradually decrease along the flue gas flow direction.

7. The regenerative desorption catalytic oxidation device for small molecule alkane VOCs according to claim 3, characterized in that, The catalyst of the noble metal catalyst plate (54) contains at least one of platinum and palladium; the catalyst of the integral catalyst module (4) is a transition oxide catalyst.

8. The regenerative desorption catalytic oxidation device for small molecule alkane VOCs according to claim 4, characterized in that, The power of the microwave radiation generator (53) is 200W to 800W and is adjustable.

9. A method for the catalytic oxidation of small molecule alkane VOCs using the apparatus described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1: VOCs flue gas containing small molecule alkanes enters the device through the VOCs inlet flue (1), while high-temperature flue gas generated by the hot air furnace enters the device through the high-temperature flue gas inlet flue (3). In the high-low temperature flue gas heat exchange module (2), VOCs flue gas and high-temperature flue gas exchange and preheat each other, so that the temperature of VOCs flue gas reaches the working temperature of the integral catalyst module. S2: The preheated flue gas flows through the integral catalyst module (4) for a first catalytic oxidation; S3: By controlling the first butterfly valve (22), the high-temperature flue gas after primary oxidation selectively flows through the heat exchange flue (21) to exchange heat with the low-temperature flue gas on the inlet side, and after cooling, it enters the precious metal catalytic plate module (5) for secondary catalytic oxidation.

10. The method for catalytic oxidation of small molecule alkane VOCs with regenerative desorption according to claim 9, characterized in that, When the precious metal catalyst plate needs to be regenerated, for the target catalyst chamber in the precious metal catalyst plate module (5), close the second butterfly valve (51) at the inlet end, open the air inlet pipe (52) to introduce air, start the microwave radiation generator (53) and drive the precious metal catalyst plate (54) to rotate for in-situ regeneration; after the regeneration is completed, restore the operation of the catalyst chamber.

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