Composite bed catalytic oxidation device and treatment method of waste gas containing VOCs (Volatile Organic Compounds)

Abstract

The invention relates to a composite bed catalytic oxidation device and a treatment method of waste gas containing VOCs, the composite bed catalytic oxidation device sequentially comprises an induced draft fan, a heater, a first fluidization heat storage reactor, a connecting channel, a sifter and a second fluidization heat storage reactor according to the flow direction of the waste gas, the two fluidization heat storage reactors are designed to respectively comprise an upper part and a lower part, the lower part is a heat storage body fixed bed, and the lower part is a heat storage body fixed bed; the upper part is a fluidized bed filled with catalyst particles and heat accumulator particles, and the heat accumulator particles flow back and forth between the two reactors through a connecting channel and a sifter, so that the deep oxidation of the waste gas is realized, and meanwhile, the generated heat is efficiently transferred. Effective transfer of catalytic oxidation reaction heat can be achieved, the reaction temperature is homogenized, the service life of a catalyst is prolonged, meanwhile, deep purification of waste gas is achieved, and the heat utilization rate is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste gas treatment, and particularly relates to a composite bed catalytic oxidation device and a method for treating waste gas containing VOCs. Background Art

[0002] VOCs (volatile organic compounds) are characteristic pollutants of refineries and petrochemical enterprises. During the production process, VOCs mainly come from process exhaust gas, leakage of equipment and pipeline components, storage and transportation of volatile organic liquids, and atmospheric pollutant emissions from wastewater collection, treatment, and storage facilities. They can be divided into organized emission sources and unorganized emission sources, and usually, the unorganized emissions account for a relatively large proportion.

[0003] The treatment technologies for waste gas containing VOCs are roughly divided into recovery methods, destruction methods, and direct utilization methods. Among them, the recovery method is to recover most of the organic components in the organic waste gas by methods such as oil agent absorption, adsorbent adsorption, or condensation, reducing the organic matter content in the waste gas. However, the total hydrocarbon content of the organic waste gas treated by such methods is still relatively high and cannot meet the direct discharge standards. Therefore, it is still necessary to use the destruction method for treatment. The so-called destruction method is to carry out catalytic oxidation on the organic waste gas by using catalytic oxidation, high-temperature oxidation, etc. Such methods usually require catalysts, high-temperature environments, etc. to oxidize the organic matter into carbon dioxide and water, and the treatment effect is better. However, in the existing fixed-bed catalytic oxidation, honeycomb catalysts are filled in the reactor, and the organic waste gas passes through the catalyst bed layer radially. As the organic matter reacts in the catalytic bed layer, a large amount of reaction heat is released, causing the reaction temperature to increase step by step. Often, the temperature at the end of the fixed-bed catalyst reaches the maximum temperature allowed by the catalyst. The catalyst reacts at this temperature for a long time, shortening the service life of the catalyst. Especially with the increasingly strict environmental protection requirements, it is necessary to increase the reaction temperature of the catalytic oxidation method, which will inevitably shorten the service life of the catalyst and there is also a risk of catalyst deactivation due to temperature runaway. Moreover, the conventional VOCs catalytic oxidation process flow is that the high-temperature waste gas discharged from the catalytic oxidation reactor exchanges heat with the incoming normal-temperature waste gas containing VOCs through a heat exchanger. However, due to the increase in the temperature of the waste gas at the reactor outlet, the requirements for the heat exchanger are further improved. Under the condition of the same ordinary stainless steel material, existing heat exchangers such as heat pipe type, shell and tube type, and plate heat exchangers have low temperature resistance and heat transfer efficiency. And due to the increase in the heat transfer amount, to achieve the expected heat transfer effect, it is necessary to further increase the heat transfer area, increasing the investment in the heat exchanger.

[0004] CN113952822A discloses a fixed-bed plus fluidized-bed recovery method for VOCs in the viscose industry. It includes the following steps: S1 Fixed-bed recovery treatment, collecting VOCs waste gas generated in production workshops such as coating machines in adhesive enterprises and introducing it into a fixed-bed recovery device for adsorption treatment; S2 The gas adsorbed by the fixed-bed recovery device is introduced into a fluidized bed for adsorption concentration. In this method, the steam demister condenses and removes fog from the desorbed high-temperature mixed gas discharged from the fixed-bed, and then introduces it into the fluidized bed together with the waste gas adsorbed by the fixed-bed. After adsorption concentration, stable and up-to-standard gas is discharged, and at the same time, the condensed and separated liquid solvent is recycled. Setting the steam demister outside the bed cannot avoid the risk of runaway temperature at the end of the fixed bed, and there is still a problem of shortening the service life of the catalyst. Moreover, the reaction heat generated in the fixed bed and the fluidized bed is not effectively utilized.

[0005] CN110296424A discloses an anti-scaling fluidized-bed regenerative oxidation device and a thermal oxidation method for VOCs gas. The anti-scaling fluidized-bed regenerative 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 outlet of the scrubbing tower 1 and the outlet of 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 regenerator layer 8 is arranged inside the fluidized regenerative bed 11. In this invention, a spherical regenerator layer is arranged inside the fluidized regenerative bed. When hot air passes through, friction is generated by the flow of the regenerator, and the scale is removed and carried into the cyclone separator by the wind, thus effectively solving the problem of scale blockage of the regenerator. However, the purpose of this invention is to solve the problem of scale formation in the fluidized-bed regenerator. The temperature of the oxidation combustion reaction is 600-1200°C, which is relatively high and the operating cost is relatively high; at the same time, the reaction heat generated by the fluidized bed is not effectively utilized. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a composite-bed catalytic oxidation device and a method for treating waste gas containing VOCs. The present invention can achieve effective transfer of catalytic oxidation reaction heat, equalize the reaction temperature, extend the service life of the catalyst, and at the same time achieve deep purification of the waste gas and improve the heat utilization rate.

[0007] A composite bed catalytic oxidation device provided by the present invention sequentially includes an induced draft fan, a heater, a first fluidized heat storage reactor, a connection channel, a sieve, and a second fluidized heat storage reactor according to the waste gas flow direction. The two fluidized heat storage reactors are respectively provided with upper and lower parts. The lower part is a fixed bed of heat storage bodies, and the upper part is a fluidized bed filled with a mixture of catalytic oxidation catalyst particles and heat storage body particles. After the device is started, the heat storage body particles flow reciprocally between the two reactors through the connection channel and the sieve, realizing the deep oxidation of waste gas and efficiently transferring the generated heat at the same time.

[0008] In the present invention, the heater is mainly used to heat the waste gas to 100 - 500 °C, preferably 250 - 400 °C. Specifically, it can be any one of an electric heater, a gas heater, an oil heater, etc., preferably an electric heater. The selected power should also meet the requirement that when starting with only air, the temperature in the fluidized heat storage reactor can be raised to the required temperature within 1 - 72 h.

[0009] In the present invention, the fluidized heat storage reactor can be in the form of a vertical cylinder, a cuboid, a cube, etc. The diameter should be selected so that the flow velocity in the fluidized bed is 0.2 - 2.0 m / s, preferably 0.8 - 1.4 m / s. The bottom of the reactor is provided with an air inlet and an exhaust port. After the waste gas containing VOCs is heated, it is transported into the reactor through the air inlet at the bottom of the reactor.

[0010] In the present invention, the first fluidized heat storage reactor and the second fluidized heat storage reactor are hermetically connected through a connection channel. A sieve is arranged in the connection channel so that the heat storage body particles in the two fluidized heat storage reactors can pass through while the catalyst particles are intercepted. The cross-section of the connection channel can be in the structure of a rectangle, a cylinder, etc. The size of the connection channel is determined according to the gas velocity of 2 - 10 m / s. The sieve is of a porous screen type, and the aperture of the screen should be smaller than the particle size of the catalyst particles and larger than the particle size of the heat storage body particles.

[0011] In the present invention, the particle size of the heat storage body particles is 0.1 - 5.0 mm, and the particle size of the heat storage body particles should be smaller than the aperture of the screen in the sieve. The material of the heat storage body particles is generally at least one of substances with heat storage capacity, specifically, at least one or a combination of several of porcelain balls, cordierite, mullite, silicon dioxide, zirconia, silicon carbide, etc. The dosage of the heat storage body particles is in a volume ratio of 1 - 6:1 to the catalyst particles.

[0012] In the present invention, the catalytic oxidation catalyst particles adopt the commonly used catalyst particles, and the particle size is 0.6 - 10 mm. The particle size of the catalyst particles is larger than the aperture of the screen in the sieve. The dosage of the particulate catalyst is such that the reaction volume space velocity is 500 - 50000 h -1The granular catalyst is preferably a catalyst supported on granular alumina or molecular sieve and loaded with noble metal Pt or / and Pd, and the noble metal loading is 0.01%-0.15%.

[0013] In the present invention, the heat storage body in the fixed bed is a heat storage body with a filtering function, and the material can be at least one of alumina, zirconia, silicon carbide, silicon nitride, boride, etc. The pore density is 5-50 PPI, the porosity ≥80%, and the filtration accuracy is 0.1-30 μm. Preferably, the heat storage body contains a foamed network structure inside, and more preferably, it is a foam ceramic.

[0014] In the present invention, a grid is provided between the fluidized bed and the fixed bed in each fluidized heat storage reactor.

[0015] The present invention also provides a method for treating waste gas containing VOCs, which uses the device provided by the present invention to treat the waste gas containing VOCs, and specifically includes the following steps:

[0016] (1) At the start of operation, start the heater to heat the heat storage body fixed bed in the first fluidized heat storage reactor to the temperature required for catalytic oxidation reaction.

[0017] (2) The waste gas containing VOCs enters the first fluidized heat storage reactor, first exchanges heat with the heat storage body of the fixed bed and is heated to the catalytic oxidation reaction temperature, and then enters the fluidized bed to carry out a fluidized reaction with the catalyst particles and the heat storage body particles. As the reaction proceeds, the heat released is absorbed and stored by the heat storage body particles, and then enters the second fluidized heat storage reactor through the sieve with the gas flow, and the catalyst particles are intercepted; the waste gas undergoes secondary oxidation in the second fluidized heat storage reactor, and transfers the heat to the catalyst particles, the heat storage body particles and the heat storage body of the fixed bed, and the purified gas is discharged from the device.

[0018] (3) In the next cycle, the waste gas is switched through the valve to first enter the second fluidized heat storage reactor to be heated by the heat storage body fixed bed, and then exchanges heat with the heat storage body particles that have completed heat storage in the fluidized bed in the previous cycle to heat the waste gas to the reaction required temperature. As the reaction proceeds, the reaction heat is released to make the heat storage body particles re-store heat. After heat storage, the heat storage body particles enter the first fluidized heat storage reactor through the sieve, waiting for the waste gas to enter in the next cycle, and the purified gas is discharged from the device.

[0019] (4) Steps (2) and (3) are repeated to achieve efficient heat transfer and deep purification of the waste gas containing VOCs.

[0020] In the present invention, when the device starts operation, it is necessary to start the heater to raise the temperature to the starting temperature of the catalytic oxidation reaction, generally 100-500 °C, preferably 250-400 °C. The heater is generally only used when the device starts. When the waste gas concentration meets the heat self-sustaining requirement of the device, the heater can stop working.

[0021] In the present invention, in the waste gas containing VOCs in step (2), the total hydrocarbon concentration is generally 2000 - 12000 mg / m 3 , preferably 2000 - 8000 mg / m 3 , and the content of low-carbon hydrocarbons is < 1000 mg / m 3 . When the total hydrocarbon concentration is relatively high, pretreatment is required or dilution gas is introduced to reduce the concentration to the specified value. The dilution gas can be any one of air, nitrogen, inert gas, etc.

[0022] In the present invention, in the first fluidized heat storage reactor in step (2), the temperature of the fluidized bed should be maintained at 300 - 650 °C, preferably 400 - 550 °C; after the heat storage body particles carry heat into the second fluidized heat storage reactor, the temperature of its fluidized bed is maintained at 250 - 500 °C, preferably 300 - 400 °C; after heat storage through the fixed bed heat storage body, the temperature of the exhaust gas is 50 - 250 °C, preferably 100 - 200 °C. In the next cycle, vice versa. When the two fluidized heat storage reactors reach heat balance, the heater can no longer be started.

[0023] In the present invention, the gas inlet and outlet switching period of the two fluidized heat storage reactors is 30 - 1000 s, preferably 60 - 300 s.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The inventors of the present application found during the operation of fixed-bed catalytic oxidation that in order to meet the purification depth requirements, generally the method of increasing the catalytic oxidation temperature is adopted, which easily causes over-temperature at the end of the fixed bed, and then leads to a shortened service life of the catalyst. To solve this problem, the inventors of the present application proposed to use a composite bed reaction device, that is, two fluidized heat storage reactors are provided, and a connection channel and a sieve are provided between the two reactors. The lower part of each reactor is a fixed bed of heat storage body, and the upper part is a fluidized bed where catalytic oxidation and heat storage are carried out in parallel. The heat storage body particles reciprocally flow between the two reactors through the sieve, alternately transferring the heat generated by catalytic oxidation to the organic waste gas, thereby realizing the deep treatment of the waste gas and the effective utilization of heat, especially equalizing the reaction temperature, avoiding the emergence of high-temperature hot spots of the catalyst, and prolonging the service life of the catalyst.

[0026] (2) The introduction of heat storage body particles in the fluidized bed and the reciprocating flow of the heat storage body particles between the two reactors can enable the heat generated by catalytic oxidation to be transferred online in a timely manner, ensuring the effective transfer of heat while reducing the amount of heat storage body used, preventing the reaction temperature from being too high, and improving the heat utilization rate.

[0027] (3) The catalyst particles and the heat storage particles are filled in the fluidized bed simultaneously, which increases the degree of waste gas disturbance in the reactor. This not only improves the fluidization reaction efficiency, but also removes the possible coking substances on the surface of the catalyst under the fluidization abrasion of the heat storage particles, restoring the catalyst activity to a certain extent and contributing to the improvement of the reaction efficiency.

[0028] (4) A heat storage fixed bed is arranged at the lower part of the fluidized bed, which cooperates with the heat storage body in the fluidized bed to ensure the heat storage efficiency. Moreover, it filters the catalyst particles and the heat storage particles in the fluidized bed to prevent them from being carried out of the reactor. At the same time, with the switching of the two reactors, the purpose of filtering dust and backwashing regeneration is achieved, avoiding fouling and blockage and not affecting the stable operation of the device. Description of the Drawings

[0029] Figure 1 is a process flow chart of the device and method of the present invention;

[0030] Wherein: 1 - heater, 201 - 1# intake valve, 202 - 2# intake valve, 301 - 1# exhaust valve, 302 - 2# exhaust valve, 401 - 1# fluidized heat storage reactor, 402 - 2# fluidized heat storage reactor, 501 - 1# fluidized bed, 502 - 2# fluidized bed, 601 - 1# grid, 602 - 2# grid, 701 - 1# heat storage fixed bed, 702 - 2# heat storage fixed bed; 8 - catalyst particles, 9 - heat storage particles, 10 - heat storage body, 11 - connection channel, 12 - sieve, 13 - induced draft fan; 101 - waste gas containing VOCs, 102 - dilution gas, 103 - purified gas. Detailed Embodiments

[0031] The technical solution and its usage effect of the present invention will be further clarified below in conjunction with the attached Figure 1 drawings and embodiments. The embodiments are implemented on the premise of the technical solution of the present invention, and the detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0032] In the following embodiments, the experimental methods are conventional methods in the art unless otherwise specified. The experimental materials used in the following embodiments can be obtained from biochemical reagent stores unless otherwise specified.

[0033] The composite bed catalytic oxidation device provided by the present invention is as shown in the attached Figure 1As shown in the figure, it sequentially includes an induced draft fan 13, a heater 1, a 1# fluidized heat storage reactor 401, a connection channel 11, a sieve 12, and a 2# fluidized heat storage reactor 402 in the waste gas flow direction. Each of the two fluidized heat storage reactors includes an upper part and a lower part. The lower part is a 1# heat storage body fixed bed 701 and a 2# heat storage body fixed bed 702 filled with heat storage bodies 10, and the upper part is a 1# fluidized bed 501 and a 2# fluidized bed 502 in which catalyst particles 8 and heat storage body particles 9 are mixed. The fluidized bed and the fixed bed are separated by a 1# grid 601 and a 2# grid 602. A connection channel 11 is provided between the two fluidized heat storage reactors 401 / 402, and a sieve 12 is provided in the connection channel to allow the heat storage body particles 9 to flow out while intercepting the catalyst particles 8. Thus, the heat storage body particles 8 can reciprocally flow between the two reactors through the connection channel and the sieve, and the heat generated by catalytic oxidation is alternately transferred to the waste gas containing VOCs.

[0034] Using the Figure 1 The device shown in the figure is used to treat the waste gas containing VOCs: At the start of operation, the heater 1 is started to heat the heat storage body fixed bed 701 in the 1# fluidized heat storage reactor 401. The waste gas containing VOCs 101 is sent into the 1# fluidized heat storage reactor 401 through the 1# inlet valve 201, and is first heated to the starting temperature of the catalytic oxidation reaction, generally 100 - 500 °C, preferably 250 - 400 °C, after exchanging heat with the heat storage body fixed bed 701. Then it enters the upper fluidized bed 501 and undergoes a catalytic oxidation reaction and a heat storage reaction with the catalyst particles 8 and the heat storage body particles 9. The reaction temperature of the fluidized bed 501 is maintained at 300 - 650 °C, preferably 400 - 550 °C; as the heat released during the reaction is absorbed and stored by the heat storage body particles 9, it enters the 2# fluidized heat storage reactor 402 through the sieve 12 along with the gas flow, and the catalyst particles are intercepted; the waste gas flow passes through the fluidized bed 502 and the heat storage body fixed bed 702 in the 2# fluidized heat storage reactor, and the temperature of the fluidized bed 502 is maintained at 250 - 500 °C, preferably 300 - 400 °C; after the heat of the gas is transferred to the heat storage body particles and the heat storage bodies in the fixed bed, the purified gas 103 after filtration and dust removal is discharged through the 1# exhaust valve 301, and the exhaust temperature is 50 - 250 °C, preferably 100 - 200 °C. In the next cycle, the waste gas containing VOCs 101 is sent into the heat storage body fixed bed 702 in the 2# fluidized heat storage reactor through the 2# inlet valve for heating, and then exchanges heat with the heat storage body particles that have completed heat storage in the fluidized bed 502 in the previous cycle, raising the waste gas temperature to the required reaction temperature and releasing heat, while enabling the heat storage body particles to store heat again. The heat storage body particles after heat storage also enter the 1# fluidized bed 501 through the connection channel 11 and the sieve 12, waiting for the entry of the waste gas containing VOCs in the next cycle. The waste gas further transfers the heat to the heat storage body fixed bed 701, and the purified gas 103 is discharged from the reaction device through the 2# exhaust valve; the above process is carried out cyclically to achieve efficient heat transfer during the treatment of the waste gas containing VOCs and deep purification of the waste gas.

[0035] In the embodiments of the present invention, in the VOCs-containing waste gas to be treated, the total hydrocarbon concentration is generally 2000-12000 mg / m 3 , preferably 2000-8000 mg / m 3 , and the content of low-carbon hydrocarbons < 1000 mg / m 3 . When the total hydrocarbon concentration is high, pretreatment is required or diluting gas 102 such as air / inert gas, etc. is introduced to reduce the concentration to the specified value.

[0036] In the embodiments of the present invention, the catalytic oxidation catalyst particles filled in the fluidized bed are supported on granular alumina, loaded with noble metals Pt and Pd, and the loading amounts are 0.04% respectively. The particle size is 0.8-3.0 mm, and the particle size of the catalyst particles must be larger than the pore diameter of the sieve mesh in the sieve. The catalyst usage is such that the reaction volume space velocity is 500-50000 h -1 .

[0037] In the embodiments of the present invention, the particle size of the regenerator particles is 0.1-5.0 mm, and the particle size of the regenerator particles must be smaller than the pore diameter of the sieve mesh in the sieve. The material of the regenerator particles is at least one of substances with heat storage capacity, specifically at least one of porcelain balls, cordierite, mullite, silicon dioxide, zirconia, silicon carbide, etc. The usage amount of the regenerator particles is such that the volume ratio to the catalyst particles is 1-6:1.

[0038] In the embodiments of the present invention, the foam ceramics filled in the regenerator fixed bed contain a large number of foamed reticular structures inside, and the material is at least one of alumina, zirconia, silicon carbide, silicon nitride, boride, etc. The pore density is 5-50 PPI, the porosity ≥ 80%, and the filtration accuracy is 0.1-30 μm.

[0039] Example 1

[0040] In the VOCs waste gas discharged from multiple facilities such as sewage oil tanks, oil separation tanks, and flotation tanks in a chemical enterprise's sewage treatment plant, the non-methane total hydrocarbon concentration is 5000-7000 mg / m 3 , and the content of low-carbon hydrocarbons is 500-530 mg / m 3 .

[0041] Adopt attached Figure 1The processing device processes it. The heater is an electric heater that heats the waste gas to 400 °C. The cross-sectional diameters of the two vertical cylindrical fluidized heat storage reactors are determined according to the flow velocity of 1.0 m / s in the fluidized bed. The connecting channel is a horizontal cylindrical structure, and the diameter of the connecting channel is determined according to the gas velocity of 5 m / s. The sieve is a porous screen type, and the aperture of the screen is 0.7 mm. The catalyst particles use granular alumina as the carrier, loaded with noble metals Pt and Pd, and the loading amounts are 0.04% respectively. The particle size of the particles is about 1.0 mm. The catalyst usage is such that the reaction volume space velocity is 15000 h -1 The heat storage body particles use cordierite heat storage body particles with a particle size of 0.5 - 0.6 mm. The volume ratio of the particle usage to the catalyst particle usage is 4:1. The fixed bed heat storage body selects zirconia foam ceramics, with a pore density of 15 PPI, a porosity of 90%, a filtration accuracy of 15 μm, and a bed height of 1.5 m.

[0042] Before the VOCs-containing waste gas enters the device, air is mixed in for dilution, and the waste gas concentration is regulated to 2000 - 2500 mg / m 3 . The reaction temperature of the 1# fluidized bed is maintained at 500 °C. After the heat storage body particles carry heat into the 2# fluidized heat storage reactor, the temperature of the 2# fluidized bed is maintained at 350 °C. After being heat-stored by the heat storage body in the 2# fixed bed, the purified gas exhaust temperature is 100 °C. In the next cycle, vice versa. When the two fluidized heat storage reactors reach heat balance, the heater is no longer started. The switching cycle of the two reactors is 120 s.

[0043] After 1000 h of treatment, the concentration of non-methane total hydrocarbons in the purified gas is always ≤ 15 mg / m 3 , and the dust content is ≤ 20 mg / m 3 . It operates stably for a long time, and the service life of the catalyst is extended by more than 1.5 times. Moreover, due to the full utilization of heat, the energy consumption can be saved by more than 13%.

[0044] Example 2

[0045] The VOCs-containing waste gas discharged from the oil separation tank in the sewage treatment plant of a chemical enterprise has a non-methane total hydrocarbon concentration of 3000 - 4000 mg / m 3 , and the low-carbon hydrocarbons are 340 - 360 mg / m 3 .

[0046] Adopt attached Figure 1The processing device processes it. The heater is an electric heater that heats the waste gas to 300 °C. The diameters of the two vertical cylindrical fluidized heat storage reactors are determined according to the flow velocity of 1.4 m / s in the fluidized bed. The connecting channel is of a vertical cylindrical structure, and the diameter of the connecting channel is determined according to the gas velocity of 8 m / s. The sieve is a porous screen type with a screen aperture of 5.0 mm. The catalyst particles use granular alumina as a carrier and are loaded with noble metals Pt and Pd, with loadings of 0.04% respectively. The particle size is about 6.5 mm, and the particle sizes are all larger than the screen aperture in the sieve. The catalyst usage is such that the reaction volume space velocity is 10,000 h -1 . The heat storage body particles are cordierite heat storage body particles with a particle size of 3.0 - 4.0 mm, and the volume ratio of the particle usage to the catalyst particle usage is 6:1. The fixed bed heat storage body is made of zirconia foam ceramics with a pore density of 25 PPI, a porosity of 90%, a filtration accuracy of 25 μm, and a bed height of 1.5 m.

[0047] The waste gas containing VOCs directly enters the device for treatment. The reaction temperature of the 1# fluidized bed is maintained at 450 °C. After the heat storage body particles carry heat into the 2# fluidized heat storage reactor, the temperature of the 2# fluidized bed is maintained at 300 °C. After heat storage by the heat storage body in the 2# fixed bed, the exhaust temperature of the purified gas is 150 °C. In the next cycle, vice versa. When the two fluidized heat storage reactors reach heat balance, the electric heater can no longer be started. The switching cycle of the two reactors is 150 s.

[0048] After 1,000 h of treatment, the concentration of non-methane total hydrocarbons in the purified gas is always ≤ 16 mg / m 3 , and the dust content is ≤ 20 mg / m 3 . It operates stably in the long term, and the service life of the catalyst can be extended by more than 1.8 times. Moreover, due to the full utilization of heat, the energy consumption can be saved by more than 15%.

[0049] Example 3

[0050] The waste gas containing VOCs discharged from the sewage oil tank, flotation tank, etc. of a chemical enterprise has a non-methane total hydrocarbon concentration of 8,000 - 9,000 mg / m 3 , and the low-carbon hydrocarbons are 910 - 930 mg / m 3 .

[0051] Adopt attached Figure 1The processing device processes it. The heater is an electric heater that heats the waste gas to 400 °C. The diameters of the two vertical cylindrical fluidized heat storage reactors are determined based on a flow velocity of 1.0 m / s in the fluidized bed. The connection channel is of a vertical cylindrical structure, and its diameter is determined according to a gas velocity of 5.0 m / s. The sieve is a porous screen type with a screen aperture of 0.5 mm. The catalyst particles use granular alumina as the carrier and are loaded with noble metals Pt and Pd, with loadings of 0.04% respectively. The particle size is about 0.7 mm, and the particle sizes are all larger than the screen aperture in the sieve. The catalyst usage is such that the reaction volume space velocity is 20,000 h -1 The heat storage body particles are cordierite heat storage body particles with a particle size of 0.2 - 0.3 mm. The volume ratio of the particle usage of the heat storage body to that of the catalyst particles is 3:1. The fixed bed heat storage body is made of zirconia foam ceramics with a pore density of 30 PPI, a porosity of 90%, a filtration accuracy of 30 μm, and a bed height of 1.5 m.

[0052] Before the waste gas containing VOCs enters the device, air is mixed into the waste gas for dilution to regulate the waste gas concentration to 5000 - 5500 mg / m 3 . The reaction temperature of the 1# fluidized bed is maintained at 450 °C. After the heat storage body particles carry heat into the 2# fluidized heat storage reactor, the temperature of the 2# fluidized bed is maintained at 320 °C. After being heat-stored by the heat storage body in the 2# fixed bed, the purified gas exhaust temperature is 220 °C. In the next cycle, vice versa. When the two fluidized heat storage reactors reach heat balance, the electric heater can no longer be started. The switching cycle of the two reactors is 220 s.

[0053] After 1000 h of treatment, the concentration of non-methane total hydrocarbons in the purified gas is always ≤ 17 mg / m 3 , and the dust content is ≤ 20 mg / m 3 . It operates stably in the long term, and the service life of the catalyst can be extended by more than 1.6 times. Moreover, due to the full utilization of heat, the energy consumption can be saved by more than 12%.

[0054] Example 4

[0055] Same as Example 1, except that: the heat storage body particles are ceramic ball heat storage bodies, and the heat storage body in the fixed bed is made of alumina foam ceramics.

[0056] After 1000 h of treatment, the concentration of non-methane total hydrocarbons in the purified gas is always ≤ 15 mg / m 3 , and the dust content is ≤ 20 mg / m 3 . It operates stably in the long term, and the service life of the catalyst can be extended by more than 1.6 times. Moreover, due to the full utilization of heat, the energy consumption can be saved by more than 12%.

[0057] Example 5

[0058] Same as Example 1, except that: the heat storage body particles are made of silica heat storage body, and the heat storage body in the fixed bed is made of silicon carbide foam ceramics.

[0059] After 1000 h of treatment, the concentration of total non-methane hydrocarbons in the purified gas is always ≤ 15 mg / m 3 , and the dust content is ≤ 20 mg / m 3 . It operates stably in the long term, and the service life of the catalyst is extended by more than 1.4 times. Moreover, due to the full utilization of heat, the energy consumption can be saved by more than 9%.

[0060] Comparative Example 1

[0061] Same as Example 1, except that: a sieve is not provided in the connecting channel. Compared with Example 1, after 1000 h of treatment, the concentration of total non-methane hydrocarbons in the purified gas is ≥ 50 mg / m 3 , and the service life of the catalyst is shortened to 90% of the original designed life. Moreover, due to the insufficient utilization of heat, the electric heater operates at a high load, and the energy consumption of the device operation increases significantly.

[0062] Comparative Example 2

[0063] Same as Example 1, except that: the fixed bed of the heat storage body at the bottom is not provided in the fluidized heat storage reactor. Compared with Example 1, after 1000 h of treatment, the concentration of total non-methane hydrocarbons in the purified gas is ≥ 28 mg / m 3 , and due to the insufficient utilization of heat, the flue gas temperature rises, the electric heater operates at a high load, and the energy consumption of the device operation is relatively high.

[0064] Comparative Example 3

[0065] Same as Example 1, except that: the heat storage body particles are not introduced into the fluidized bed of the fluidized heat storage reactor. Compared with Example 1, after 1000 h of treatment, the concentration of total non-methane hydrocarbons in the purified gas is always higher than 40 mg / m 3 , and due to carbon deposition on the catalyst surface, the service life of the catalyst is shortened to 80% of the original designed life. Moreover, due to the insufficient utilization of heat, the load of the electric heater increases, and the operation energy consumption is high.

Claims

1. A composite bed catalytic oxidation device, characterized in that: According to the waste gas flow direction, it includes an induced draft fan, a heater, a first fluidized heat storage reactor, a connection channel, a sieve, and a second fluidized heat storage reactor. The two fluidized heat storage reactors are designed to include upper and lower parts respectively. The lower part is a fixed bed of heat storage bodies, and the upper part is a fluidized bed filled with a mixture of catalytic oxidation catalyst particles and heat storage body particles. The heat storage body particles flow reciprocally between the two reactors through the connection channel and the sieve, realizing the deep oxidation of waste gas and efficiently transferring the generated heat.

2. The device according to claim 1, characterized in that: The heater is used to heat the waste gas to 100 - 500 °C, preferably 250 - 400 °C, and specifically is any one of an electric heater, a gas heater, and an oil heater, preferably an electric heater.

3. The device according to claim 1, characterized in that: The fluidized heat storage reactor is one of the forms of a vertical cylinder, a cuboid, and a cube reactor. The diameter is selected so that the flow velocity in the fluidized bed is 0.2 - 2.0 m / s, preferably 0.8 - 1.4 m / s.

4. The device according to claim 1 or 3, characterized in that: An air inlet and an exhaust outlet are provided at the bottom of the reactor. The waste gas containing VOCs is heated and then transported into the reactor through the bottom air inlet and discharged from the reactor through the bottom exhaust outlet.

5. The device according to claim 1, characterized in that: The first fluidized heat storage reactor and the second fluidized heat storage reactor are connected through a connection channel. A sieve is provided in the connection channel. The cross-section of the connection channel is any one of a rectangular shape and a cylindrical structure. The size of the connection channel is determined according to the gas velocity of 2 - 10 m / s.

6. The device according to claim 1 or 5, characterized in that: The sieve is a porous screen type, and the aperture of the screen should be smaller than the particle size of the catalyst particles and larger than the particle size of the heat storage body particles.

7. The device according to claim 1, characterized in that: The particle size of the heat storage body particles is 0.1 - 5.0 mm, and the particle size of the heat storage body particles should be smaller than the aperture of the screen in the sieve; the heat storage body particles are made of at least one of porcelain balls, cordierite, mullite, silicon dioxide, zirconia, and silicon carbide; the usage amount of the heat storage body particles is in a volume ratio of 1 - 6:1 to the catalyst particles.

8. The device according to claim 1, characterized in that: The particle size of the catalyst particles is 0.6 - 10 mm, and the particle size of the catalyst particles should be larger than the pore size of the sieve mesh in the sieve; the dosage of the particulate catalyst is such that the reaction volume space velocity is 500 - 50000 h -1 .

9. The device according to claim 1 or 8, characterized in that: The particulate catalyst is preferably a catalyst with granular alumina or molecular sieve as the carrier and loaded with noble metal Pt or / and Pd, and the noble metal loading is 0.01% - 0.15%.

10. The device according to claim 1, characterized in that: The heat storage body in the fixed bed is a heat storage body with a filtering function, and the material is at least one of alumina, zirconia, silicon carbide, silicon nitride, and boride. The pore density is 5 - 50 PPI, the porosity ≥ 80%, and the filtering accuracy is 0.1 - 30 μm; preferably, a heat storage body containing a foamed network structure inside, and more preferably a foam ceramic.

11. The device according to claim 1, characterized in that: A grid is provided between the fluidized bed and the fixed bed in each fluidized heat storage reactor.

12. A method for treating waste gas containing VOCs, characterized in that the waste gas containing VOCs is treated by using the device according to any one of claims 1-11. Specifically It includes the following steps: (1) At the start of operation, start the heater to heat the fixed bed of the heat storage body in the first fluidized heat storage reactor to the temperature required for catalytic oxidation reaction. (2) Feed the waste gas into the first fluidized heat storage reactor. First, exchange heat with the fixed bed heat storage body and then heat up to the catalytic oxidation reaction temperature. Then enter the fluidized bed and carry out a fluidized reaction with the catalyst particles and the heat storage body particles. As the reaction proceeds, the heat released is absorbed and stored by the heat storage body particles. Then, along with the gas flow, it enters the second fluidized heat storage reactor through the sieve, and the catalyst particles are intercepted. The waste gas undergoes secondary oxidation in the second fluidized heat storage reactor, and the heat is transferred to the catalyst particles, the heat storage body particles, and the fixed bed heat storage body, and the purified gas is discharged from the device. (3) In the next cycle, the waste gas is switched through the valve and first fed into the second fluidized heat storage reactor to be heated by the fixed bed of the heat storage body, and then exchange heat with the heat storage body particles that have completed heat storage in the fluidized bed in the previous cycle, heating the waste gas to the reaction required temperature. As the reaction proceeds, the reaction heat is released to make the heat storage body particles re-store heat. After heat storage, the heat storage body particles enter the first fluidized heat storage reactor through the sieve, waiting for the waste gas to enter in the next cycle, and the purified gas is discharged from the device. (4) Steps (2) and (3) are repeated cyclically to achieve deep purification of the waste gas containing VOCs.

13. According to the method described in claim 12, It is characterized in that: When the device starts operation, start the heater to raise the temperature to the starting temperature of the catalytic oxidation reaction, which is 100-500 °C, preferably 250-400 °C.

14. According to the method described in claim 12, It is characterized in that: In the waste gas containing VOCs described in step (2), the total hydrocarbon concentration is 2000 - 12000 mg / m 3 , preferably 2000 - 8000 mg / m 3 , and the content of low-carbon hydrocarbons < 1000 mg / m 3 .

15. According to the method described in claim 12, It is characterized in that: In step (2), in the first fluidized heat storage reactor, the temperature of the fluidized bed should be maintained at 300-650 °C, preferably 400-550 °C.

16. According to the method described in claim 12, It is characterized in that: After the heat storage body particles carry heat into the second fluidized heat storage reactor in step (2), maintain the temperature of its fluidized bed at 250-500 °C, preferably 300-400 °C.

17. According to the method described in claim 12, It is characterized in that: After heat storage through the fixed bed heat storage body in step (2), the temperature of the exhaust gas is 50-250 °C, preferably 100-200 °C.

18. According to the method described in claim 12, It is characterized in that: The gas inlet and outlet switching cycle of the two fluidized heat storage reactors is 30-1000 s, preferably 60-300 s.

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