A treatment method and device for VOC-containing waste gas

Abstract

This invention relates to a method and apparatus for treating VOCs-containing waste gas. The method involves heating the VOCs-containing waste gas before it enters a catalytic oxidation reactor. The reactor is primarily a fluidized bed filled with granular catalytic oxidation catalyst, where the waste gas undergoes a fluidized oxidation reaction with the granular catalyst. A radially arranged columnar fixed bed, filled with a structured catalytic oxidation catalyst, is located within the fluidized bed. The lower end of the fixed bed penetrates the bottom of the reactor and collects in an exhaust pipe. A gas-solid separator is located above the fluidized bed. After fluidized oxidation, the waste gas passes through the gas-solid separator, where the catalyst particles are retained. The separated gas enters from the top of the fixed bed for further oxidation, and the high-temperature purified gas is discharged through the exhaust pipe. This invention effectively homogenizes the reaction temperature of the catalytic oxidation, avoids high-temperature hotspots in the catalyst bed and their impact on catalyst lifespan, and simultaneously achieves deep treatment of the waste gas and efficient utilization of heat.

Description

Technical Field

[0001] This invention belongs to the field of waste gas treatment technology, specifically relating to a method and device for treating VOCs-containing waste gas. Background Technology

[0002] Volatile organic compounds (VOCs) are characteristic pollutants of oil refining and petrochemical enterprises. During the production process, VOCs mainly come from process exhaust, equipment and pipeline component leaks, storage and transportation of volatile organic liquids, and air pollutant emissions from wastewater collection, treatment and storage facilities. They can be divided into organized emission sources and unorganized emission sources, with unorganized emissions usually accounting for a larger proportion.

[0003] Treatment technologies for VOCs-containing waste gas can be broadly categorized into recovery methods, destruction methods, and direct utilization methods. Recovery methods utilize absorbents, adsorbents, or condensation to recover most of the organic components from the waste gas. However, the total hydrocarbon content of the treated waste gas remains high, failing to meet emission standards. Therefore, destruction methods, such as catalytic oxidation and high-temperature oxidation, are necessary for further treatment.

[0004] Fixed-bed catalytic oxidation involves filling a fixed-bed reactor with a catalyst. Organic waste gas undergoes catalytic oxidation through the catalyst bed, releasing a large amount of heat that causes the reaction temperature to rise in stages. Often, the temperature at the end of the catalyst bed reaches the catalyst's maximum allowable temperature. Prolonged reaction at this temperature shortens the catalyst's lifespan. Furthermore, increasingly stringent environmental regulations require higher reaction temperatures to meet emission standards, increasing the risk of runaway emissions and catalyst deactivation, further shortening catalyst lifespan. In existing VOCs catalytic oxidation processes, high-temperature waste gas exiting the reactor exchanges heat with ambient-temperature VOCs waste gas entering through a heat exchanger. The increased temperature of the waste gas at the reactor outlet places higher demands on the heat exchanger. Under the same conditions using ordinary stainless steel materials, existing heat exchangers such as heat pipe, shell-and-tube, and plate heat exchangers have relatively low heat exchange efficiency. To achieve the desired heat exchange effect, the heat exchange area needs to be further increased due to the increased heat exchange capacity, increasing investment in the heat exchanger.

[0005] CN207025073U discloses an energy-saving and highly adaptable catalytic oxidation waste gas treatment device, including a heat exchanger, a heater, a catalytic oxidation reactor, an air cooler, a reflux induced gas system, and a heat exchanger bypass system. The reflux induced gas system includes reflux induced gas equipment and control components. The cold stream outlet of the heat exchanger is connected to the heater inlet, and the heater outlet is connected to the catalytic oxidation reactor inlet. The catalytic oxidation reactor outlet is divided into two paths: one connected to the hot stream inlet of the heat exchanger, and the other connected to the reflux induced gas equipment inlet. The hot stream outlet of the heat exchanger is connected to the air cooler inlet, and the air cooler outlet is divided into two paths: one connected to the exhaust stack, and the other connected to the reflux induced gas equipment inlet. The reflux induced gas equipment outlet is connected to the heater waste gas inlet. The heat exchanger bypass system connects the hot stream inlet and outlet of the heat exchanger. This patent can efficiently and energy-savingly treat waste gas with intermittent emissions and large fluctuations in organic matter concentration, achieving safe and stable operation of the waste gas treatment device. However, this method uses fixed-bed treatment. With increasingly stringent environmental protection requirements, the reaction temperature needs to be further increased to meet emission requirements, posing a risk of overheating and catalyst deactivation, which will shorten the catalyst's lifespan.

[0006] CN110296424A discloses an anti-scaling fluidized bed regenerative thermal oxidation device and a method for thermal oxidation of VOCs gas. The anti-scaling fluidized bed regenerative thermal oxidation device includes a scrubbing tower 1, a burner 2, a fluidized regenerative bed 11, a cyclone separator 6, and a tail gas treatment device 7. The outlets of the scrubbing tower 1 and the burner 2 are respectively connected to the inlet of the fluidized regenerative bed 11. The outlet of the fluidized regenerative bed 11 is connected to the inlet of the cyclone separator 6. The outlet of the cyclone separator 6 is connected to the inlet of the tail gas treatment device 7. A spherical heat storage layer 8 is provided inside the fluidized regenerative bed. This invention, by providing a spherical heat storage layer inside the fluidized regenerative bed, allows the heat storage body to flow and generate friction when hot air passes through, removing scale, which then enters the cyclone separator with the airflow. This effectively solves the problem of scale buildup and blockage in the heat storage body, significantly reducing operating and maintenance costs. However, the preferred temperature for the oxidation-combustion reaction is 600–1200°C, and more preferably 800°C. The higher the reaction temperature, the higher the operating cost. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method and apparatus for treating VOCs-containing waste gas. The method and apparatus of this invention effectively homogenize the reaction temperature of catalytic oxidation, avoiding high-temperature hotspots in the catalyst bed and their impact on catalyst lifespan, and achieving deep treatment of waste gas and effective utilization of heat.

[0008] The present invention provides a method for treating VOCs-containing waste gas, comprising the following:

[0009] After being heated, the VOC-containing waste gas enters the catalytic oxidation reactor. The reactor is mainly composed of a fluidized bed and is filled with granular catalytic oxidation catalyst. The waste gas and the catalyst particles undergo a fluidized oxidation reaction. Several tubular fixed beds are arranged radially inside the fluidized bed and filled with regular catalytic oxidation catalyst. The lower ends of the tubular fixed beds penetrate the bottom of the reactor and collect in an exhaust pipe. Several gas-solid separators are installed above the fluidized bed. After fluidized oxidation, the waste gas passes through the gas-solid separators, where the catalyst particles it carries are trapped. The separated gas enters from the top of the fixed bed and continues to oxidize. The high-temperature purified gas is discharged through the exhaust pipe.

[0010] In this invention, the initial temperature required for the catalytic oxidation reaction of VOCs-containing waste gas is generally 100-500℃, preferably 250-400℃. Heating is achieved using a heat exchanger and / or a heater, preferably using the high-temperature purified gas discharged from the fixed bed as the heat source. If the temperature after heat exchange cannot reach the initial temperature required for the catalytic oxidation reaction, further heating is applied using a heater. The heater is generally only used during device startup; once the entire reaction system reaches thermal equilibrium, the heater can be discontinued. The heat exchanger can be any type of heat pipe, shell-and-tube, or plate heat exchanger, with a plate heat exchanger being preferred. The heater can be any type of electric heater, gas heater, or fuel oil heater, with an electric heater being preferred.

[0011] In this invention, the catalytic oxidation reactor can be of various forms such as column type or tower type. The reactor diameter should be selected so that the flow velocity in the fluidized bed is 0.2-2 m / s, preferably 0.8-1.4 m / s. An air inlet is provided at the bottom of the reactor. After the VOCs-containing waste gas is heated to the initial temperature, it is transported into the fluidized bed through the air inlet. The particulate catalyst is fluidized by adjusting the pressure.

[0012] In this invention, the particulate catalytic oxidation catalyst packed in the fluidized bed is a conventionally used catalyst with a particle diameter of 0.6-10 mm, preferably 0.8-3.0 mm; the catalyst dosage is such that the reaction volume hourly space velocity is 500-50000 h⁻¹. -1 The particulate catalytic oxidation catalyst is preferably a catalyst supported on granular alumina or molecular sieves and loaded with noble metals Pt and / or Pd, with the noble metal loading being 0.01%-0.15%.

[0013] In this invention, at least one cylindrical fixed bed is radially arranged within the fluidized bed, preferably 1-20. The cross-sectional area ratio of the fluidized bed to the fixed beds is 3-10:1, and they are preferably symmetrically distributed across the cross-section of the fluidized bed. The fixed beds can have various cross-sectional shapes, such as circular, elliptical, rectangular, or triangular. Furthermore, the outer surface of the fixed beds preferably uses fins or threads, and the wall material can be stainless steel, ceramic, or any other material.

[0014] In this invention, the structured catalytic oxidation catalyst packed in the fixed bed is either monolithic or randomized, such as monolithic honeycomb ceramic or other randomized catalysts. The amount of catalyst used is such that the reaction volume hourly space velocity is between 500 and 50,000 h⁻¹. -1 The structured catalytic oxidation catalyst is preferably a honeycomb support catalyst supported on noble metals Pt and / or Pd, with the loading of noble metals Pt and / or Pd being 0.01%-0.15% by weight of the honeycomb support.

[0015] In this invention, the reaction temperature of fluidized oxidation is maintained at 300-550℃, preferably 400-500℃, by adjusting the heater and the concentration of waste gas entering the fluidized bed. The gas separated by the gas-solid separator directly enters the fixed bed, and the outlet temperature of the fixed bed is 1-100℃ higher than the inlet temperature, preferably not higher than 650℃.

[0016] In this invention, the lower end of each fixed bed penetrates the bottom of the reactor and collects in an exhaust pipe. The high-temperature purified gas after deep oxidation by the fixed bed is discharged through the exhaust pipe and transported to a heat exchanger to exchange heat with the VOCs waste gas to be treated. After heat exchange, the purified gas is discharged outside the device. The temperature of the discharged purified gas is generally 90-300℃, preferably 120-180℃.

[0017] In this invention, a gas-solid separator is located above the fluidized bed, with its outlet connected to the inlet of the fixed bed. It is used to trap catalyst particles carried in the exhaust gas discharged from the fluidized bed, and the separated gas enters the fixed bed. The gas-solid separator primarily consists of filter components, which can be of various forms, such as perforated, cylindrical, or bag-type structures. The material can be any of glass fiber, sintered metal mesh, or ceramic membrane, etc. The filter pore diameter is larger than the diameter of the particulate catalytic oxidation catalyst, generally 5-100 μm. The total cross-sectional area of ​​the gas-solid separators is 1-4 times the total cross-sectional area of ​​the fixed bed, and the number of separators is generally 8-20, preferably symmetrically distributed. A backflushing assembly is correspondingly installed above each gas-solid separator, and the purging medium can be at least one of air, N2, or other gases.

[0018] In this invention, the total hydrocarbon concentration in VOCs-containing waste gas is generally 2000-12000 mg / m³. 3 Preferred concentration: 4000-8000 mg / m³ 3 When the total hydrocarbon concentration is high, pretreatment or dilution gas is required to reduce the concentration to a specified value. The dilution gas can be any of air, nitrogen, inert gas, etc.

[0019] This invention also provides a treatment device for the above-mentioned VOCs-containing waste gas treatment method, comprising, in sequence according to the waste gas flow direction, a heat exchanger, a heater, and a catalytic oxidation reactor. The heat exchanger and / or heater are used to raise the temperature of the VOCs-containing waste gas to the starting temperature required for the catalytic oxidation reaction. The catalytic oxidation reactor is mainly composed of a fluidized bed, filled with granular catalytic oxidation catalyst, for the waste gas to undergo a fluidized oxidation reaction with the catalyst particles. Several columnar fixed beds are radially arranged inside the fluidized bed, filled with regular catalytic oxidation catalyst, and the reaction heat of fluidized oxidation is transferred to the catalyst inside the bed through the fixed bed wall. Several gas-solid separators are arranged above the fluidized bed. After fluidized oxidation, the waste gas passes through the gas-solid separators, where the catalyst particles it carries are trapped, and the gas enters the fixed bed for further oxidation. The high-temperature purified gas is discharged through the exhaust pipe at the bottom of the fixed bed.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The catalytic oxidation reactor of the present invention is mainly composed of a fluidized bed and several columnar fixed beds. After fluidized oxidation, the waste gas enters the fixed bed for oxidation, so that the two are connected in series in time and heat transfer is achieved in space. This effectively homogenizes the reaction temperature of the entire catalytic oxidation, avoids the occurrence of high temperature hot spots of catalyst and overheating at the end of fixed bed, ensures the reaction activity and service life of catalyst, and realizes deep oxidation of waste gas and effective utilization of heat.

[0022] (2) A two-stage catalytic oxidation reaction module of fluidized bed-fixed bed is designed in a reactor. Through heat transfer and temperature control, the temperature difference between the inlet and outlet of the fixed bed is kept below 100℃, which reduces the exhaust temperature of the fixed bed and thus reduces the heat exchange area and investment cost of the heat exchanger.

[0023] (3) By setting up a gas-solid separator between the upper part of the fluidized bed and the inlet of the fixed bed, the quality and concentration of the waste gas flow can be controlled, so that the temperature and solid content of the waste gas flow are conducive to the control of the fixed bed and the deep oxidation of the waste gas can be achieved. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a process flow for the method and apparatus of the present invention;

[0025] Wherein: 1-heat exchanger, 2-heater, 3-catalytic oxidation reactor, 4-gas-solid separator, 5-fixed bed, 6-exhaust pipe, 7-backflush assembly, 8-particulate catalytic oxidation catalyst, 9-structured catalytic oxidation catalyst; 101-VOCs-containing waste gas, 102-backflush gas, 103-high-temperature purified gas, 104-exhaust purified gas.

[0026] Figure 2 This is a top view showing the distribution of the fixed bed and gas-solid separator in this invention. Detailed Implementation

[0027] The following embodiments further illustrate the technical solution and effects of the present invention. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples can be purchased from biochemical reagent stores.

[0029] The VOCs-containing waste gas treatment device of the present invention is as follows: Figure 1 As shown, the reactor comprises a heat exchanger 1, a heater 2, and a catalytic oxidation reactor 3, arranged sequentially according to the direction of waste gas flow. The heat exchanger 1 and / or heater 2 heat the VOC-containing waste gas 101 to be treated to the initial temperature required for the catalytic oxidation reaction before it enters the catalytic oxidation reactor 3. The catalytic oxidation reactor 3 is primarily a fluidized bed, filled with granular catalytic oxidation catalyst 8. The waste gas undergoes a fluidized oxidation reaction with the catalyst particles. Several cylindrical fixed beds 5 are radially arranged within the fluidized bed, filled with structured catalytic oxidation catalyst 9. The heat of reaction from the fluidized oxidation is transferred to the catalyst 9 within the bed through the fixed bed wall. The lower end of each fixed bed penetrates the bottom of the reactor and converges into an exhaust pipe 6. Several gas-solid separators 4 are installed above the fluidized bed, with their outlets connected to the fixed bed inlets. After fluidized oxidation, the waste gas passes through the gas-solid separators 4, where the catalyst particles are trapped. The separated gas then enters the fixed bed for further oxidation, and the high-temperature purified gas is discharged through the exhaust pipe 6. A backflushing assembly 7 is correspondingly installed above each gas-solid separator 4, and the purging medium can be air, N2, or other gases.

[0030] In this embodiment of the invention, the particulate catalytic oxidation catalyst uses granular alumina as a support, loaded with noble metals Pt and Pd at loading amounts of 0.04% each, with a particle diameter of 0.8-3.0 mm. The catalyst dosage is such that the reaction volume hourly space velocity is 500-50000 h⁻¹. -1 .

[0031] In this embodiment of the invention, a fixed bed is filled with an integrally loaded honeycomb ceramic catalyst containing noble metals Pt and Pd, using a cordierite honeycomb support. The loading amounts of Pt and Pd, based on the mass of the honeycomb support, are 0.04% each. The catalyst dosage is such that the volume hourly space velocity (HHSV) is maintained between 500 and 50000 h⁻¹. -1 A packing grid for fixing the catalyst is installed at the upper and lower ends of the fixed bed.

[0032] Example 1

[0033] Adopting attachment Figure 1The VOCs-containing waste gas treatment device shown includes a cylindrical catalytic oxidation reactor with a diameter of 2.8 m. Five symmetrically distributed cylindrical fixed beds, made of stainless steel, are located within the fluidized bed, with a fluidized bed to fixed bed cross-sectional area ratio of 5:1. Twelve symmetrically distributed gas-solid separators, employing a perforated structure made of sintered metal mesh, have a filter pore diameter of 50 μm and a cross-sectional size identical to that of the fixed beds. These separators are used to trap particulate catalyst carried in the waste gas exiting the fluidized bed, and the separated gas then enters the fixed beds for further oxidation. A backflushing assembly is installed above each gas-solid separator, using nitrogen (N2) as the purging medium.

[0034] The concentration of non-methane total hydrocarbons in the VOCs-containing waste gas to be treated is 5000 mg / m³. 3 about.

[0035] The VOC-containing waste gas is heated to 300℃ after passing through a heat exchanger and / or heater. The heat exchanger uses high-temperature purified gas discharged from a fixed bed for heat exchange. If the temperature after heat exchange cannot reach the required initial reaction temperature, the heater is used for heating. Once the entire reaction system reaches thermal equilibrium, the heater is no longer activated. The heat exchanger is a plate heat exchanger, and the heater is an electric heater.

[0036] The waste gas is transported into the fluidized bed through the inlet at the bottom of the fluidized bed. The fluidized bed is filled with particulate catalytic oxidation catalyst with a particle diameter of about 0.8 mm. The amount of catalyst used is such that the reaction volume hourly space velocity is 10,000 h⁻¹. -1 Pressure was adjusted to fluidize the particulate catalyst. The reaction temperature of the fluidized catalytic oxidation was maintained at 400℃ by controlling the exhaust gas concentration. The inlet temperature of the fixed bed was kept consistent with the outlet temperature of the gas-solid separator, and the catalyst dosage in the fixed bed was adjusted to maintain a reaction volume hourly space velocity (VHSV) of 5000 h⁻¹. -1 The temperature of the high-temperature purified gas discharged from the fixed bed is 500℃. After exchanging heat with the ambient temperature VOCs waste gas entering the catalytic oxidation reactor in the heat exchanger, the gas is discharged at an exhaust temperature of 170℃.

[0037] After 1000 hours of operation, the concentration of non-methane total hydrocarbons in the emitted purified gas remained below 100 mg / m³. 3 No high-temperature hot spots or overheating of the fixed-bed reaction occurred during long-term operation, and the catalyst lifespan was 131% of the original design life. Moreover, due to the full utilization of heat, energy consumption can be saved by more than 24%.

[0038] Example 2

[0039] Adopting attachment Figure 1The VOCs-containing waste gas treatment device shown features a cylindrical catalytic oxidation reactor with a diameter of 2.8 m. Five symmetrically distributed cylindrical fixed beds, made of stainless steel, are located within the fluidized bed, with a fluidized bed to fixed bed cross-sectional area ratio of 5:1. Twelve symmetrically distributed gas-solid separators, employing a perforated structure made of sintered metal mesh, have a filter pore diameter of 50 μm and a cross-sectional size identical to that of the fixed beds. These gas-solid separators trap catalyst particles carried in the waste gas exiting the fluidized bed; the separated gas then enters the fixed beds for further oxidation. A backflushing assembly is installed above each gas-solid separator, using nitrogen (N2) as the purging medium.

[0040] The concentration of non-methane total hydrocarbons in the VOCs waste gas to be treated is 8000 mg / m³. 3 about.

[0041] The VOC-containing waste gas is heated to 350℃ after passing through a heat exchanger and / or heater. The heat exchanger uses high-temperature purified gas discharged from a fixed bed for heat exchange. When the temperature after heat exchange cannot reach the required initial temperature of the reactor, heating is applied by the heater. Once the entire reaction system reaches thermal equilibrium, the heater is no longer activated. The heat exchanger is a plate heat exchanger, and the heater is an electric heater.

[0042] The waste gas is introduced into the fluidized bed through the inlet at the bottom of the fluidized bed. The fluidized bed is filled with granular catalytic oxidation catalyst with a particle diameter of 2 mm. The amount of catalyst used is such that the reaction space velocity is 20,000 h⁻¹. -1 Pressure was adjusted to fluidize the granular catalyst. The reaction temperature of the fluidized catalytic oxidation was maintained at 500℃ by controlling the concentration of waste gas entering the fluidized bed. The inlet temperature of the fixed bed was kept consistent with the outlet temperature of the gas-solid separator, and the catalyst dosage in the fixed bed was sufficient to maintain a reaction volume hourly space velocity of 10,000 h⁻¹. -1 The temperature of the high-temperature purified gas discharged from the fixed bed is 650℃. After exchanging heat with the ambient temperature VOCs waste gas entering the catalytic oxidation reactor in the heat exchanger, the gas is discharged at an exhaust temperature of 220℃.

[0043] After 1000 hours of operation, the concentration of non-methane total hydrocarbons in the emitted purified gas remained below 100 mg / m³. 3 This avoids the occurrence of high-temperature hot spots on the catalyst and overheating in the fixed-bed reaction, extending the catalyst's lifespan to 118% of the original design life. Moreover, due to the full utilization of heat, energy consumption can be saved by more than 29%.

[0044] Example 3

[0045] Adopting attachment Figure 1The VOCs-containing waste gas treatment device shown features a cylindrical catalytic oxidation reactor with a diameter of 2.8 m. Five symmetrically distributed cylindrical fixed beds, made of stainless steel, are located within the fluidized bed, with a fluidized bed to fixed bed cross-sectional area ratio of 5:1. Twelve symmetrically distributed gas-solid separators, employing a perforated structure made of sintered metal mesh, have a filter pore diameter of 50 μm and a cross-sectional size identical to that of the fixed beds. These separators trap catalyst particles carried in the oxidation waste gas exiting the fluidized bed, allowing the separated gas to continue oxidation in the fixed beds. A backflushing assembly is installed above each gas-solid separator, using nitrogen (N2) as the purging medium.

[0046] The concentration of non-methane total hydrocarbons in the VOCs-containing waste gas to be treated is 3000 mg / m³. 3 about.

[0047] VOCs exhaust gas is heated to 280℃ after passing through a heat exchanger and heater. The heat exchanger uses high-temperature purified gas discharged from a fixed bed for heat exchange. When the temperature after heat exchange cannot reach the required initial reaction temperature, the heater is used for heating. Once the entire reaction system reaches thermal equilibrium, the heater is no longer activated. The heat exchanger is a plate heat exchanger, and the heater is an electric heater.

[0048] The waste gas is conveyed into the fluidized bed through the waste gas inlet at the bottom of the fluidized bed. The fluidized bed is filled with granular catalytic oxidation catalyst with a particle diameter of 1.0 mm. The amount of catalyst used in the fluidized bed is such that the reaction space velocity is 30,000 h⁻¹. -1 Pressure was adjusted to fluidize the granular catalyst. The reaction temperature of the fluidized catalytic oxidation was maintained at 400℃ by controlling the concentration of waste gas entering the fluidized bed. The inlet temperature of the fixed bed was kept consistent with the outlet temperature of the gas-solid separator, and the catalyst dosage in the fixed bed was adjusted to maintain a reaction space velocity of 30,000 h⁻¹. -1 The temperature of the high-temperature purified gas discharged is 480℃. After exchanging heat with the ambient temperature VOCs waste gas entering the catalytic oxidation reactor in the heat exchanger, the gas is discharged at an exhaust temperature of 110℃.

[0049] After 1000 hours of operation, the concentration of non-methane total hydrocarbons in the emitted purified gas remained below 100 mg / m³. 3 This avoids the occurrence of high-temperature hot spots on the catalyst and overheating in the fixed-bed reaction, extending the catalyst's lifespan to 139% of the original design life. Moreover, due to the full utilization of heat, energy consumption can be saved by more than 16%.

[0050] Example 4

[0051] The difference from Example 1 is that the gas-solid separator is replaced with a cylindrical filter, the height of which is 1 / 4 of the height of the fixed bed. The material is a sintered metal mesh with a filter hole diameter of 50μm. The total cross-sectional area of ​​the filter is twice the total cross-sectional area of ​​the fixed bed.

[0052] After 1000 hours of operation, the concentration of non-methane total hydrocarbons in the emitted purified gas remained below 100 mg / m³. 3 This avoids the occurrence of high-temperature hot spots on the catalyst and overheating in the fixed-bed reaction. Compared with Example 1, the increased filtration area prevents an increase in bed pressure drop, which helps to further homogenize the reaction temperature, and the catalyst lifespan is 142% of the original design life.

[0053] Example 5

[0054] The difference from Example 1 is that the columnar fixed bed adopts a tubular structure, the outer surface of the fixed bed is finned, and the material is ceramic. After 1000 hours of operation, the concentration of non-methane total hydrocarbons in the emitted purified gas remained below 100 mg / m³. 3 This avoids the occurrence of high-temperature hot spots on the catalyst and overheating in the fixed-bed reaction. Compared with Example 1, the heat transfer in the fluidized bed and fixed bed is more efficient, the catalyst lifespan is 136% of the original design life, and energy consumption can be saved by more than 33%.

[0055] Comparative Example 1

[0056] Similar to Example 1, except that a fixed bed of the same size as the fluidized bed is used instead of the fluidized bed, both filled with structured catalyst. To meet the treatment requirements, the reactor inlet temperature needs to be increased to above 500℃, and the outlet temperature is consistently between 600-650℃. After 500 hours of operation, hot spots exceeding 650℃ are generated in some parts of the fixed bed catalyst, and the catalyst lifespan is 78% of the original design lifespan.

[0057] Comparative Example 2

[0058] Same as Example 1, except that only a fluidized bed was used, without a fixed bed. After 1000 hours of operation, the concentration of non-methane total hydrocarbons in the purified gas increased to 300 mg / m³. 3 In summary, the waste gas was not adequately treated; the fluidized reaction of the catalyst resulted in some loss, and the heat was not effectively utilized.

[0059] Comparative Example 3

[0060] Similar to Example 1, but with the difference that a fluidized bed and a fixed bed are connected in series, with the fixed bed consisting of a single bed layer. The waste gas from the fluidized oxidation process then enters the fixed bed. After 1000 hours of operation, the concentration of non-methane total hydrocarbons in the emitted purified gas increased to 200 mg / m³. 3 In the above cases, the waste gas was not treated effectively, the heat was not utilized effectively, and hot spots exceeding 650°C were generated in some parts of the fixed bed. The catalyst lifespan was reduced to 78.5% of the original design lifespan.

Claims

1. A method for treating VOC-containing exhaust gas, characterized by The application relates to a VOCs-containing waste gas heating and catalytic oxidation device.

2. The method of claim 1, wherein: The VOCs-containing waste gas is heated to a starting temperature of 100-500 DEG C required for catalytic oxidation.

3. The method of claim 2, wherein: The VOCs-containing waste gas is heated to a starting temperature of 250-400 DEG C required for catalytic oxidation.

4. The method according to claim 1 or 2 or 3, characterized in that: The heating is achieved by using a heat exchanger or a heater.

5. The method of claim 4, wherein: The high-temperature purified gas discharged from the fixed bed is used for heat exchange in the heat exchanger, and if the temperature after heat exchange cannot reach the starting temperature, the heater is used for heating.

6. The method of claim 4, wherein: The heat exchanger is any one of a heat pipe type, a tube type and a plate type heat exchanger, and the heater is any one of an electric heater, a gas heater and an oil heater.

7. The method of claim 6, wherein: The heat exchanger is a plate type heat exchanger, and the heater is an electric heater.

8. The method of claim 1, wherein: The catalytic oxidation reactor is columnar or tower-shaped, and the reactor diameter is selected to make the flow velocity in the fluidized bed 0.2-2 m / s.

9. The method of claim 8, wherein: The reactor diameter is selected to make the flow velocity in the fluidized bed 0.8-1.4 m / s.

10. The method of claim 1 or 8, wherein: The reactor bottom is provided with an air inlet, the VOCs-containing waste gas is transported into the fluidized bed through the air inlet after being heated, and the granular catalyst is made to realize fluidization by adjusting and controlling the pressure.

11. The method of claim 1, wherein: The diameter of the granular catalytic oxidation catalyst in the fluidized bed is 0.6-10 mm; the catalyst usage is to make the reaction volume space velocity at 500-50000 h -1 .

12. The method of claim 1, wherein: The diameter of the granular catalytic oxidation catalyst in the fluidized bed is 0.8-3.0 mm.

13. The method of claim 1 or 11 or 12, wherein: The granular catalytic oxidation catalyst takes granular alumina or molecular sieve as a carrier and is loaded with noble metal Pt or Pd, and the noble metal loading amount is 0.01%-0.15%.

14. The method of claim 1, wherein: The cross section shape of the columnar fixed bed adopts at least one of a circular shape, an elliptical shape, a rectangular shape and a triangular shape, and the material is stainless steel or ceramic.

15. The method of claim 14, wherein: The outer surface of the columnar fixed bed adopts a fin or screw thread form.

16. The method of claim 1, wherein: The packed bed is filled with a structured catalytic oxidation catalyst which is monolithic or in bulk form; the catalyst is used in such an amount that the reaction volume space velocity is in the range from 500 to 50,000 h -1 .

17. The method of claim 16, wherein: The fixed bed is filled with the regular catalytic oxidation catalyst which is a monolithic honeycomb ceramic catalyst.

18. The method of claim 1, wherein: The catalytic oxidation catalyst filled in the fixed bed is a honeycomb carrier catalyst loaded with noble metal Pt and / or Pd, and the noble metal Pt and / or Pd loading amount is 0.01%-0.15% based on the mass of the honeycomb carrier.

19. The method of claim 1, wherein: The fluidized oxidation reaction temperature is maintained at 300-550 DEG C by adjusting and controlling the heater and the waste gas concentration.

20. The method of claim 19, wherein: The fluidized oxidation reaction temperature is maintained at 400-500 DEG C by adjusting and controlling the heater and the waste gas concentration.

21. The method of claim 1, wherein: The gas separated by the gas-solid separator directly enters the fixed bed, and the fixed bed outlet temperature is 1-100 DEG C higher than the fixed bed inlet temperature.

22. The method of claim 21, wherein: The fixed bed outlet temperature is not higher than 650℃.

23. The method of claim 1, wherein: The high-temperature purified gas after the fixed bed depth oxidation is discharged through the exhaust pipe, transported to the heat exchanger to exchange heat with the waste gas to be treated, and then discharged out of the device after heat exchange. The discharged purified gas temperature is 90-300℃.

24. The method of claim 23, wherein: The discharged purified gas temperature is 120-180℃.

25. The method of claim 1, wherein: The gas-solid separator is arranged at the upper part of the fluidized bed and is communicated with the fixed bed inlet, used for intercepting the catalyst particles carried from the waste gas discharged from the fluidized bed, and the separated gas enters the fixed bed; the gas-solid separator is any one of a hole type, a cylinder type, and a bag type filter assembly, and the material is any one of glass fiber, metal sintered mesh, and ceramic membrane, and the filter hole diameter is greater than the particle catalyst diameter.

26. The method of claim 25, wherein: The filter hole diameter is greater than the particle catalyst diameter, which is 5-100μm.

27. The method of claim 1 or 25, wherein: The back flushing assembly is arranged at the upper part of each gas-solid separator, and the flushing medium is at least one of air and N2.

28. The method of claim 1, wherein: The total hydrocarbon concentration in the VOCs-containing exhaust gas is 2000-12000 mg / m 3 When the total hydrocarbon concentration is high, pretreatment or dilution with air, nitrogen, or any of the inert gases is required to reduce the concentration to the specified value.

29. The method of claim 28, wherein: The total hydrocarbon concentration in the VOC-containing exhaust gas is 4000-8000 mg / m 3 .

30. A treatment device for the treatment of VOCs-containing exhaust gas according to any one of claims 1-29, characterized in that: The waste gas flows through the heat exchanger, the heater, and the catalytic oxidation reactor in sequence, the heat exchanger and / or the heater are used to heat the waste gas containing VOCs to the required initial temperature of the catalytic oxidation reaction; the catalytic oxidation reactor mainly uses the fluidized bed, filled with catalytic oxidation particle catalyst, and the waste gas and the catalyst particles are subjected to fluidized oxidation reaction; the cylindrical fixed bed is arranged radially in the fluidized bed, filled with regular catalytic oxidation catalyst, and the reaction heat of the fluidized oxidation is transferred to the catalyst in the bed through the fixed bed wall; the lower end of each fixed bed penetrates the reactor bottom and is collected in an exhaust pipe; the gas-solid separator is arranged at the upper part of the fluidized bed, and the outlet is communicated with the fixed bed inlet, the fluidized oxidation stream passes through the gas-solid separator, the carried catalyst particles are intercepted, the separated gas enters the fixed bed for further oxidation, and the high-temperature purified gas is discharged through the exhaust pipe.

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