CN106731806B - Cross-flow ceramic membrane device for gas denitration and denitration method - Google Patents
Cross-flow ceramic membrane device for gas denitration and denitration method Download PDFInfo
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- CN106731806B CN106731806B CN201611241297.6A CN201611241297A CN106731806B CN 106731806 B CN106731806 B CN 106731806B CN 201611241297 A CN201611241297 A CN 201611241297A CN 106731806 B CN106731806 B CN 106731806B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
- B01D53/8631—Processes characterised by a specific device
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D—SEPARATION
- B01D2251/00—Reactants
- B01D2251/20—Reductants
- B01D2251/206—Ammonium compounds
- B01D2251/2062—Ammonia
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Abstract
The invention relates to a cross-flow ceramic membrane device for gas denitration and a denitration method, and belongs to the technical field of gas purification. Mainly adopts a ceramic membrane with a double-layer or multi-layer structure, a catalyst is loaded on the inner surface of the ceramic membrane, and nitrogen oxide and ammonia gas are fed in a cross flow manner to prepare the cross flow type ceramic membrane device for gas denitration. The nitrogen oxides are subjected to 'aeration type' air inlet by utilizing the porosity of the ceramic membrane and fully react with ammonia in the ceramic membrane channel under the action of the catalyst, and the denitration efficiency is higher than that of the traditional method.
Description
Technical Field
The invention relates to a cross-flow ceramic membrane device for gas denitration and a denitration method, and belongs to the technical field of gas purification.
Background
Nitrogen Oxides (NO) x ) Is one of the main pollutants in the atmosphere and seriously harms the ecological environment and human health. One of the commonly used technologies for denitration at present is an ammonia selective catalytic reduction method, and the conventional method is to coat a catalyst on the surface of a honeycomb or porous ceramic carrier, place the carrier in a closed container, and carry out two flue gases (high-temperature NO) x And NH 3 ) After being collected in a pipe, the mixture flows into a container, NO x And NH 3 Reaction to form N 2 And steam to achieve the aim of denitration.
However, this denitration method has problems that the reaction efficiency is low and the catalyst is easily contaminated by impurities in the raw material gas and poisoned.
Disclosure of Invention
The invention provides a denitration reactor of a tubular ceramic membrane with a catalyst loaded on the inner surface, which is used for removing NO x And N 2 The reactor realizes cross flow effect by using the internal channel of the tubular ceramic membrane and then supplies NO from the side of the support layer by separately feeding materials and utilizing the advantages of narrow and easily controllable pore size distribution of the ceramic membrane x Raw gas, NO x The impurities are removed by a porous supporting layer and NO is realized by the porous supporting layer x The stable feeding of the raw material gas realizes the interface reaction on the catalyst layer on the inner surface of the tubular ceramic membrane, and simultaneously removes the reaction product by utilizing the cross flow effect, thereby improving the catalytic reaction efficiency.
The technical scheme is as follows:
first aspect of the invention:
the tubular ceramic membrane is a tubular membrane, the outer wall of the ceramic membrane is a porous supporting layer, a channel is arranged in the porous supporting layer, and a denitration catalyst layer is loaded on the inner side surface of the porous supporting layer.
The denitration catalyst layer is made of CeO 2 、V 2 O 5 、MnO 2 、Fe 2 O 3 、TiO 2 、WO 3 And MgO or a mixture of two or more thereof.
The porous support layer consists of a ceramic membrane support layer and a ceramic membrane layer from outside to inside; the number of the internal channels of the tubular membrane is one or more.
The porosity of the ceramic membrane support layer is 15-60%, and the aperture is 10-100 μm; the porosity of the ceramic membrane layer is 15-60%, and the pore diameter is 0.5-20 μm.
Second aspect of the invention:
the utility model provides a cross-flow ceramic membrane device for gaseous denitration, including denitration reactor casing, inside is provided with the tubular ceramic membrane of load catalyst, form the cavity between the outside of the tubular ceramic membrane of load catalyst and the denitration reactor casing, still be provided with the sealing member inside the denitration reactor casing, the sealing member is isolated the cavity with the internal channel of the tubular ceramic membrane of load catalyst, be provided with the casing air inlet that is linked together with the cavity on the denitration reactor casing, it is linked together still to be provided with ceramic membrane air inlet and ceramic membrane gas outlet on the denitration reactor casing, connect respectively in the both ends of the tubular ceramic membrane passageway of load catalyst.
In a third aspect of the invention:
a denitration method comprises the following steps:
i) Using a tubular ceramic membrane carrying a catalyst to contain NO x The raw material gas is pressed into the membrane tube from the outer side of the tube-type ceramic membrane and permeates into the denitration catalyst layer;
ii) will contain NH 3 Is fed from the channel of the catalyst-supporting tubular ceramic membrane and forms a catalyst-containing stream containing NH 3 The raw material gas flows from the surface of the channel in a cross flow way, so that NH is generated 3 And NO x And carrying out catalytic reaction on the surface of the denitration catalyst layer.
The reaction temperature is 320-380 ℃, and the reaction contains NH 3 The feed pressure of the raw material gas is 4-80 Kpa, and the feed pressure of the raw material gas containing NOx is 5-100 Kpa.
Advantageous effects
Mainly adopts a ceramic membrane with a double-layer or multi-layer structure, a catalyst is loaded on the inner surface of the ceramic membrane, and nitrogen oxide and ammonia gas are fed in a cross flow manner to prepare the cross flow type ceramic membrane device for gas denitration. The nitrogen oxides are subjected to 'aeration type' air inlet by utilizing the porosity of the ceramic membrane and fully react with ammonia in the ceramic membrane channel under the action of the catalyst, and the denitration efficiency is higher than that of the traditional method.
Drawings
FIG. 1 is a schematic front view of a cross-flow ceramic membrane apparatus for denitration according to the present invention;
FIG. 2 is a schematic top view of a cross-flow ceramic membrane apparatus for denitration according to the present invention;
fig. 3 is a schematic top view of a ceramic membrane supporting a catalyst.
Wherein, 1, a cavity; 2. a catalyst-supporting tubular ceramic membrane; 3. a housing air inlet; 4. a ceramic membrane air inlet; 5. a ceramic membrane air outlet; 6. a ceramic membrane support layer; 7. a ceramic membrane layer; 8. a denitration catalyst layer; 9. a ceramic membrane channel; 10. a denitrification reactor housing; 11. and a seal.
Detailed Description
The invention provides a ceramic membrane for loading a catalyst, which is a tubular membrane, and can be a single-tube type or a multi-channel type (namely, a plurality of channels are arranged inside), the structure of the single-tube type ceramic membrane is shown in figure 3, the outer wall of the tube is a ceramic membrane support layer 6, a ceramic membrane layer 7 is arranged on the inner wall side of the ceramic membrane support layer 6, and a catalyst layer 8 is arranged on the inner wall side of the ceramic membrane layer 7, wherein the ceramic membrane support layer 6 and the ceramic membrane layer 7 are taken as a porous support layer as a whole, in other embodiments, the support layer can be adopted independently, the ceramic membrane layer can be adopted independently, the support layer and the membrane layer which are arranged from outside to inside in sequence can be adopted, and the aim of the invention can be achieved as long as the catalyst layer is loaded inside the support layer outside.
As the material of the catalyst layer 8, which has been disclosed in the prior art, for example: ceO (CeO) 2 、V 2 O 5 、MnO 2 、Fe 2 O 3 、TiO 2 、WO 3 And MgO or a mixture of two or more thereof.
The support can increase the mechanical strength of the ceramic membrane, and the requirement of the support is that the support has larger pore diameter and porosity so as to increase the permeability of gas and reduce the gas conveying resistance. The porosity of the support is 15 to 60%, more preferably 20 to 40%.
The membrane layer is used for loading the catalyst, prevents the catalyst from being soaked into the pore canal of the support body in the coating and sintering processes, and can be directly coated with the catalyst layer when the pore diameter of the support body is within the range of pore diameter. The porosity of the membrane layer is 15 to 60%, more preferably 20 to 40%.
The pore diameter of the support is 10-5000 μm, and the preferable range is 500-800 μm.
The pore diameter of the membrane layer is 0.5-200 μm, and the preferable range is 50-100 μm.
The support body and the membrane layer are both porous structures, so that the mechanical strength of the ceramic membrane is increased, the effect of loading a catalytic catalyst is improved, and NO which is uniformly distributed and enters the membrane tube can be used x Gas, let NO x The gas enters a ceramic membrane channel in an aeration mode, NO x Gas and NH 3 The reaction is more complete under the action of the catalyst.
NO in the present invention x Refers to nitrogen oxides, such as: NO, NO 2 And the like.
The cross-sectional shape of the channel may be selected from square, hexagonal, triangular or circular, and the cross-sectional shape formed by the outer wall of the membrane tube may be similarly selected from these shapes, and the cross-section of the channel may be the same as or different from the cross-sectional shape formed by the outer wall of the membrane tube. In some preferred cases, it is preferable that both cross-sectional shapes are the same because of ease of manufacturing; in addition, the cross section is preferably circular, which can ensure large membrane area and is suitable for production and molding.
The material of the support and/or the film layer is selected from silicon carbide, diatomite, mullite, alumina, zirconia or titania, and is particularly suitable for the support and/or the film layer made of the alumina, the zirconia or the titania because the support and/or the film layer has better stability.
The reactor is structurally shown in fig. 1 and 2, and comprises a denitration reactor shell 10, a catalyst-loaded tubular ceramic membrane 2 is arranged inside the denitration reactor shell, a cavity 1 is formed between the outside of the catalyst-loaded tubular ceramic membrane 2 and the denitration reactor shell 10, a sealing element 11 is further arranged inside the denitration reactor shell 10, the cavity 1 is isolated from an internal channel of the catalyst-loaded tubular ceramic membrane 2 by the sealing element 11, a shell air inlet 3 communicated with the cavity 1 is formed in the denitration reactor shell 10, a ceramic membrane air inlet 4 and a ceramic membrane air outlet 5 are further formed in the denitration reactor shell 10 and are communicated with each other and respectively connected to two ends of the catalyst-loaded tubular ceramic membrane 2 channel.
During operation of the apparatus, NO x And NH 3 Separately fed, NO x Enters the reactor through the shell gas inlet 3, and NH 3 Fed from the ceramic membrane inlet 4 and the reaction product exits from the ceramic membrane outlet 5 at the other end. By utilizing the advantages of narrow and easily-controlled pore size distribution of the ceramic membrane, a layer of catalyst NO is loaded on a ceramic membrane support or a membrane layer x Enters a ceramic membrane channel and NH in an aeration way through the outer surface of the ceramic membrane through a support body and a membrane layer pore channel 3 Mixing, and reacting under the action of catalyst to obtain N 2 And water vapor.
Denitration operation test of ceramic membrane
The ceramic membrane denitration test device adopted by the invention has a structure as shown in figure 1, a plurality of ceramic membrane tubes are vertically assembled in the device, and a cavity formed in the device is NO x The (gas) shell side, the channel of the ceramic membrane tube is NH 3 Tube side (gas), NO x NH which enters the ceramic membrane tube through the membrane tube support layer, the membrane layer and the catalyst layer and flows slowly 3 Fully react under the action of a catalyst to generate N 2 And water vapor.
Example 1
The tests were carried out under different conditions:
a total of 9 ceramic membrane tubes were mounted in the module, and the membrane tubes were arranged in 3*3 in cross section and were 1m in length. The membrane tube is a single tube, and the size and the shape are as follows: circular, 12mm outside diameter, 8mm inside diameter.
Containing NO 2 Is introduced from the shell side of the reactor, NO x Concentration 1000mg/Nm 3 At 350 deg.C, 15KPa pressure and 0.3m flow rate 3 /min。
NH is introduced into the channel of the membrane tube 3 The flow of pure ammonia gas entering the membrane after the pyrolysis of the pure ammonia is 0.3m 3 At 310 ℃ and a pressure of 10 Kpa/min.
The porosity of the support and the membrane layer is 45%, the membrane tube is made of alumina, the average pore diameter of the support is 50 μm, the average pore diameter of the membrane layer is 10 μm, the thickness of the catalyst layer is 20 μm, and V is 2 O 5 Catalyst, after reaction, device outlet NO x The concentration is reduced to 95mg/Nm 3 And the denitration efficiency is 90.5%.
Example 2
The tests were carried out under different conditions:
a total of 16 ceramic membrane tubes were mounted in the module, and they were arranged 4*4 in cross-section, with a membrane tube length of 1.2m. The membrane tube is a single tube, and the size and the shape are as follows: circular, 20mm outside diameter, 14mm inside diameter.
Containing NO 2 Is introduced from the shell side of the reactor, NO x Concentration 1000mg/Nm 3 At 320 ℃, the pressure of 18KPa and the flow of 0.5m 3 /min。
NH is introduced into the channel of the membrane tube 3 The flow of pure ammonia gas entering the membrane after the pyrolysis of the pure ammonia is 0.2m 3 At 340 deg.C/min and 12Kpa.
The porosity of the support and the membrane layer is 35%, the material is the membrane tube of zirconia, the average pore diameter of the support is 1000 μm, the average pore diameter of the membrane layer is respectively 20, 50, 100 and 200 μm, the thickness of the catalyst layer is 20 μm, and is V 2 O 5 Catalyst, after reaction, to export NO under different pore size conditions x The concentration and denitration efficiency were as follows
Example 3
The tests were carried out under different conditions:
a total of 9 ceramic membrane tubes were mounted in the module, and the length of the membrane tubes was 1.0m, with 3*3 alignment when viewed in cross-section. The membrane tube is a single tube, and the size and the shape are as follows: circular, external diameter 10mm, internal diameter 5mm.
Containing NO 2 Is introduced from the shell side of the reactor, NO x The concentration is 1500mg/Nm 3 The temperature is 360 ℃, the pressure is 12KPa, and the flow is 0.4m 3 /min。
NH is introduced into the channel of the membrane tube 3 The flow of pure ammonia gas entering the membrane after the pyrolysis of the pure ammonia is 0.5m 3 At 320 ℃ and 11 Kpa/min.
The porosity of the support body and the film layer is 40%, the material is the film tube of zirconia, the average hole of the support bodyThe diameters are respectively 200, 500, 800, 1000 and 2000 μm, the average pore diameter of the film layer is respectively 50 μm, the thickness of the catalyst layer is 15 μm, and is V 2 O 5 A catalyst.
Outlet of NO at different pore sizes of support x The concentration and denitration efficiency were as follows:
comparative example 1
The differences from example 1 are: adding NO x And NH 3 All enter the reactor from the feed inlet 4, and NO is 2 Gas and NH 3 The gas flow is the same, the reaction conditions are the same, and NO is discharged from the device x The concentration is reduced to 540 mg/Nm 3 The denitration efficiency was 46%.
Claims (3)
1. A denitration method is characterized by comprising the following steps:
i) Using a catalyst-loaded tubular ceramic membrane (2) to contain NO x The raw material gas is pressed into the membrane tube from the outer side of the tube-type ceramic membrane (2) and permeates into the denitration catalyst layer;
ii) will contain NH 3 Is fed from the channel of the catalyst-supporting tubular ceramic membrane (2) and forms a catalyst-containing stream containing NH 3 The raw material gas flows from the surface of the channel in a cross flow way, so that NH is generated 3 And NO x Carrying out catalytic reaction on the surface of the denitration catalyst layer;
the reaction temperature is 320-380 ℃, and the reaction contains NH 3 The feed gas has a feed pressure of 4-80 KPa and contains NO x The feeding pressure of the raw material gas is 5-100 Kpa;
the tubular ceramic membrane loaded with the catalyst is a tubular membrane, the outer wall of the ceramic membrane is a porous supporting layer, a ceramic membrane channel (9) is arranged in the porous supporting layer, and a denitration catalyst layer (8) is loaded on the inner side surface of the porous supporting layer;
the porosity of the ceramic membrane support layer (6) is 15-60%, and the aperture is 500-800 μm; the porosity of the ceramic membrane layer (7) is 15-60%, and the aperture is 0.5-20 μm.
2. The denitration method according to claim 1, wherein the denitration catalyst layer (8) is made of a material selected from CeO 2 、V 2 O 5 、MnO 2 、Fe 2 O 3 、TiO 2 、WO 3 And MgO or a mixture of two or more thereof.
3. The denitration method according to claim 1, wherein the porous support layer is composed of a ceramic membrane support layer (6) and a ceramic membrane layer (7) from the outside to the inside; the number of the ceramic membrane channels (9) in the tubular membrane is one or more.
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| CN114563310B (en) * | 2021-05-08 | 2023-03-17 | 南京工业大学 | CO (carbon monoxide) 2 /N 2 Method for predicting diffusion process of binary mixture through multilayer ceramic membrane |
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Address after: No.195, buyue Road, Pukou Economic Development Zone, Nanjing City, Jiangsu Province, 211806 Applicant after: JIANGSU JIUWU HITECH Co.,Ltd. Address before: No. 9, Garden Idea, Pukou Economic Development Zone, Nanjing, Jiangsu 211808 Applicant before: JIANGSU JIUWU HITECH Co.,Ltd. |
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