Dust removal and denitration composite filter bag and filtering method thereof

Abstract

The dust removal and denitration composite filter bag integrally comprises a plurality of functional filter bag sections and a plurality of connecting parts, the functional filter bag sections are linearly arranged from top to bottom, each connecting part is arranged between each two adjacent functional filter bag sections, and each functional filter bag comprises a metal film catalysis filter bag and a metal film filter bag; the first section of the dust removal and denitration composite filter bag is the metal film catalysis filter bag, and the rest are the metal film filter bags; the connecting part is of a flange structure, and a coating type SCR honeycomb catalyst is embedded in the flange structure. According to the special structural design of the dust removal and denitration composite filter bag, the dust removal and denitration composite filter bag has good dust removal precision and denitration activity in a wide temperature range, the risk of catalyst deactivation and bag pasting can be reduced while the stable denitration efficiency is improved, and the production and manufacturing cost can be remarkably reduced.

Description

Technical Field

[0001] The present application relates to the technical field of functional filter materials, and mainly to a dust removal and denitrification composite filter bag and a filtering method thereof. Background Art

[0002] Industrial combustion processes generate large quantities of gases containing NOx and dust, causing serious environmental problems such as acid rain, photochemical smog, and haze. After years of effective air pollution control in my country's coal-fired power sector, the sector has transformed from a heavily polluting industry into a model for air pollution prevention and control. In addition to the power industry, my country also has a large number of non-power industries, such as small and medium-sized kilns. Unlike the relatively stable and single flue gas operating conditions of the power industry, the non-power industry, due to its wider scope, generally has complex flue gas composition and is difficult to treat. Large coal-fired power plants generally use traditional tandem flue gas purification processes with separate denitrification and dust removal units. This not only requires large space but also has high investment and operating costs. However, small and medium-sized kilns in my country are small in scale, numerous, and have complex flue gas compositions. Therefore, the multi-pollutant removal processes and catalysts previously used in large-scale industrial combustion flue gas from the power industry cannot be directly applied to non-power industries. Considering the current status and difficulties of industrial kiln flue gas treatment, the development of advanced materials and technologies for integrated dust and NO removal is a current research hotspot and important development direction for flue gas purification from small and medium-sized kilns.

[0003] The so-called integrated dust and nitrate removal technology refers to the simultaneous removal of NOx and dust from flue gas using the same set of technical devices or systems within the same flue gas temperature range. The core component of the integrated dust and nitrate removal technology is the "dust removal and denitrification composite filter bag / filter cartridge" that has both filtering and denitrification functions. In view of the characteristics of industrial kiln flue gas, there are currently high-precision, high-activity, and wide-temperature-range metal membrane catalytic filter bags that can meet the needs of industrial kiln flue gas dust removal and denitrification. They also have better air permeability, low resistance, water resistance, and sulfur resistance than existing materials, and have high recycling value. However, there are also some problems in actual applications. For example, when some industrial kilns (such as biomass boilers) are started and stopped at low temperatures, the flue gas will condense, causing the alkali and alkaline earth metals therein to dissolve in liquid water and penetrate into the catalytic filter bag layer, which can easily cause the catalyst to be deactivated by alkali poisoning. In addition, the production cost of metal membrane catalytic filter bags is relatively high.

[0004] Therefore, it is of great significance to develop an economical, stable and efficient dust removal and denitrification composite filter bag. Summary of the Invention

[0005] During the actual operation of cleaning or starting and stopping the furnace, condensation often occurs due to the low flue gas temperature, which causes the lower part of the filter bag to become sticky. If the filter bag is a catalytic filter bag, condensation can easily cause the alkali and alkaline earth metals in the flue gas to dissolve in liquid water and then penetrate into the catalyst, causing the catalyst to be deactivated by alkali poisoning, which increases the actual operating cost.

[0006] In response to the problems existing in the prior art, this application proposes a dust removal and denitrification composite filter bag and a manufacturing method thereof.

[0007] According to one aspect of the present application, a dust removal and denitrification composite filter bag is proposed, comprising a plurality of sections of functional filter bags linearly arranged from top to bottom and a plurality of connecting portions respectively arranged between two adjacent sections of the functional filter bags, wherein the functional filter bags include metal membrane catalytic filter bags and metal membrane filter bags; the first section of the dust removal and denitrification composite filter bag is the metal membrane catalytic filter bag, and the rest are the metal membrane filter bags; the connecting portion is a flange structure, and the flange structure has an embedded coated SCR honeycomb catalyst. Since condensation mostly occurs in the middle and lower part of the filter bag, this solution arranges the metal membrane catalytic filter bag, which serves as the main denitrification catalyst, in the first section of the dust removal and denitrification composite filter bag, thereby effectively solving the problem of catalyst poisoning and deactivation caused by condensation in the middle and lower part of the filter bag without changing the current actual operating conditions; in addition, since the flange structure carries a coated SCR honeycomb catalyst, it can also play a certain catalytic denitrification role, ensuring the overall denitrification efficiency of the composite filter bag, and the catalyst is easy to replace and dispose of.

[0008] Furthermore, the functional filter bag has at least three sections, each 0.6-1.1 meters long. Depending on actual operating conditions, the functional filter bag can have different sections and lengths. The design of a minimum of three sections and the length limit ensure that the filter bag as a whole has a certain dust removal efficiency, and the first section of the metal membrane catalytic filter bag is not affected by condensation, thereby improving the equipment's dust removal and denitrification efficiency and reducing production costs.

[0009] Furthermore, the overall length of the dust removal and denitrification composite filter bag should not exceed 8.0m. Excessively long filter bags will increase airflow resistance, thereby affecting dust removal efficiency and the convenience of dust removal of the equipment. Operators will need to spend more time and energy on dust removal, reducing production efficiency.

[0010] Furthermore, the metal membrane catalytic filter bag is a metal membrane filter bag with a catalytic layer. The metal membrane filter bag is formed by welding a metal membrane and a metal porous plate, and the metal membrane is formed by pressing and sintering metal fibers or metal powders. The metal membrane filter bag has good dust removal accuracy in a wide temperature range, and its water resistance and sulfur resistance are better than those of traditional filter materials. It is an ideal high-temperature flue gas dust removal material. By arranging a catalyst interlayer inside the metal membrane filter material, a metal membrane catalytic filter material is formed. The metal membrane catalytic filter bag thus produced can realize the integrated function of dust and saltpeter, has good dust removal accuracy and denitrification activity in a wide temperature range, and has low air permeability, high space utilization and recycling degree.

[0011] Preferably, the catalytic layer is a nickel foam-supported catalyst layer. Nickel foam has a high surface area and good mass transfer properties, which can effectively improve catalyst utilization and reduce costs. Furthermore, the porous structure of nickel foam not only facilitates contact between the catalyst and the reactants, improving catalytic activity and selectivity, but also reduces the pressure drop when the fluid passes through the carrier, reducing the energy consumption of the reaction system. Furthermore, nickel foam has good high temperature resistance and chemical stability, which can enhance the recyclability and long-term stability of the catalyst in high temperature environments, making it an excellent carrier for monolithic catalysts.

[0012] Furthermore, the flange structure includes an upper flange and a lower flange. The bottom of the upper flange is flush with the bottom of the coated SCR honeycomb catalyst. The upper flange is provided with a threaded outer ring, and the lower flange is provided with a threaded inner ring. The upper flange and the lower flange are detachably connected by threads. The upper flange is welded to the bottom of the functional filter bag, and the lower flange is welded to the top of the functional filter bag. The design of the flange structure being split up and down and connected by threads facilitates the maintenance and replacement of the functional filter bag and the coated SCR honeycomb catalyst, and is also conducive to adjusting the composite filter bag according to the working conditions. The design of the bottom of the upper flange being flush with the bottom of the coated SCR honeycomb catalyst maximizes the use of the internal space of the flange structure without affecting the dust removal of the filter bag.

[0013] Furthermore, the bottom of the last section of the dust removal and denitration composite filter bag is sealed with a flange cover. The detachable bottom design facilitates adjustment of the number of sections of the functional filter bag according to changes in working conditions, thereby selecting the most appropriate overall length of the dust removal and denitration composite filter bag.

[0014] According to the second aspect of the present application, a filtration method for a dust removal and denitrification composite filter bag is proposed, and the specific process is as follows:

[0015] S1. Air intake: Flue gas enters the dust and saltpeter integrated device through the flue. During the air intake process, the flue gas temperature can be controlled by adjusting the fan frequency or adding cold air through the cold air valve;

[0016] S2. Dust removal and denitrification: Flue gas enters the dust removal and denitrification composite filter bag, and dust in the flue gas is blocked on the surface of the dust removal and denitrification composite filter bag, completing dust removal; NOx is removed by the catalytic layer in the metal membrane catalytic filter bag and the coated SCR honeycomb catalyst in the flange structure, completing denitrification;

[0017] S3. Exhaust: The clean flue gas after dust removal and denitrification is discharged through the outlet flue.

[0018] Furthermore, in S2, the metal membrane catalytic filter bag is away from the condensation area. Condensation generally occurs in the middle and lower part of the filter bag. Therefore, the catalyst in the metal membrane catalytic filter bag located in the first section is almost not corroded by liquid water, and the risk of poisoning and deactivation of the coated SCR honeycomb catalyst located in the middle and upper part is relatively small.

[0019] Furthermore, the condensation area is located in the lower middle portion of the dust removal and denitrification composite filter bag. When the flue gas temperature reaches condensation conditions, liquid water forms in the condensation area. The unique structural design protects the metal membrane catalytic filter bag and the flange structure closer to the metal membrane catalytic filter bag from condensation. Therefore, the catalytic layer within the metal membrane catalytic filter bag and the coated SCR honeycomb catalyst within the flange structure will not be poisoned and deactivated, thereby ensuring the stability of the denitrification performance of the dust removal and denitrification composite filter bag.

[0020] Compared with the existing technology, this application has the following beneficial effects:

[0021] The dust removal and denitrification composite filter bag of the present application can ensure that it has good dust removal accuracy and denitrification activity within a wide temperature range, while also reducing the risk of filter bag deactivation and bag sticking, and improving the efficiency of stable denitrification; in addition, the special design of using metal membrane filter bags to replace part of the metal membrane catalytic filter bags effectively reduces the production cost of the dust removal and denitrification composite filter bag of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate the embodiments and, together with the description, serve to explain the principles of the present application. Other embodiments and many of the expected advantages of the embodiments will be readily apparent as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale with respect to each other. Like reference numerals designate corresponding similar parts.

[0023] Figure 1 A dust removal and denitrification composite filter bag filtration method according to an embodiment of the present application is shown;

[0024] Figure 2 The overall structure of the dust removal and denitrification composite filter bag according to a specific embodiment of the present application is shown;

[0025] Figure 3 A cross-sectional view of a dust removal and denitrification composite filter bag according to a specific embodiment of the present application is shown;

[0026] Figure 4 It shows the trend chart of various data before the start and stop of the pilot phase I;

[0027] Figure 5 Shows the trend chart of various data after the start and stop of the pilot phase I furnace;

[0028] Figure 6 It shows the trend chart of various data before the start and stop of the pilot phase II furnace;

[0029] Figure 7 The trend chart of various data after the start and stop of the pilot phase II furnace is shown.

[0030] In the figure, 1-metal membrane catalytic filter bag; 11-metal membrane catalytic filter bag metal membrane layer; 12-metal membrane catalytic filter bag catalytic layer; 13-metal membrane catalytic filter bag metal porous plate; 2-flange structure; 21-coated SCR honeycomb catalyst; 22-lower flange threaded outer ring; 23-upper flange threaded inner ring; 3-metal membrane filter bag; 31-metal membrane layer of metal membrane filter bag; 32-metal membrane filter bag metal porous plate; 4-flange cover. DETAILED DESCRIPTION

[0031] The present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the relevant invention and are not intended to limit the invention. It should also be noted that, for ease of description, only portions relevant to the relevant invention are shown in the accompanying drawings.

[0032] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0033] The specific production steps of the dust removal and denitrification composite filter bag of this application are as follows:

[0034] Prepare metal membrane catalytic filter bags and metal membrane filter bags; weld the upper flange and the lower flange to each functional filter bag, and weld the catalyst fixing parts in the lower flange; install the coated SCR honeycomb catalyst in the flange structure; connect and fix the metal membrane catalytic filter bag and the metal membrane filter bag in sequence through the flange structure, and seal the bottom of the filter bag with the flange cover to obtain the dust removal and denitrification composite filter bag.

[0035] The dust removal and denitrification composite filter bag of the present application has a filtering method as follows Figure 1 The specific process is as follows:

[0036] S1. Air intake: Flue gas enters the dust and saltpeter integrated device through the flue. During the air intake process, the flue gas temperature can be controlled by adjusting the fan frequency or adding cold air through the cold air valve;

[0037] S2. Dust removal and denitrification: Flue gas enters the dust removal and denitrification composite filter bag, and dust in the flue gas is blocked on the surface of the dust removal and denitrification composite filter bag, completing dust removal; NOx is removed by the catalytic layer in the metal membrane catalytic filter bag and the coated SCR honeycomb catalyst in the flange structure, completing denitrification;

[0038] S3. Exhaust: The clean flue gas after dust removal and denitrification is discharged through the outlet flue.

[0039] Example

[0040] A dust removal and denitrification composite filter bag comprises a plurality of sections of functional filter bags linearly arranged from top to bottom and a plurality of connecting parts respectively arranged between two adjacent sections of the functional filter bags, wherein the functional filter bags comprise a metal membrane catalytic filter bag and a metal membrane filter bag; the first section of the dust removal and denitrification composite filter bag is a metal membrane catalytic filter bag, and the rest are the metal membrane filter bags; the connecting part is a flange structure, and the flange structure has an embedded coated SCR honeycomb catalyst.

[0041] Furthermore, the functional filter bag has a total of 3 sections, each section is 0.6m long, and after adding the upper and lower flanges welded to each section, the dust removal and denitrification composite filter bag is 3m in length as a whole.

[0042] Furthermore, the metal membrane catalytic filter bag is a metal membrane filter bag with a catalytic layer.

[0043] Preferably, the catalytic layer is a nickel foam-supported catalyst layer.

[0044] Furthermore, the flange structure includes an upper flange and a lower flange. The bottom of the upper flange is flush with the bottom of the coated SCR honeycomb catalyst. The upper flange is provided with a threaded outer ring and the lower flange is provided with a threaded inner ring. The upper flange and the lower flange are detachably connected by threads. The upper flange is welded to the bottom of the functional filter bag and the lower flange is welded to the top of the functional filter bag.

[0045] Furthermore, the bottom of the last section of the dust removal and denitrification composite filter bag is sealed with a flange cover.

[0046] The overall structure of the dust removal and denitrification composite filter bag is as follows Figure 2 As shown, Figure 3 for Figure 2 Cross-sectional views at AA, BB and CC.

[0047] Comparative Example

[0048] A metal film catalytic filter bag

[0049] The metal membrane catalytic filter bag of this comparative example is consistent with the metal membrane catalytic filter bag in the functional filter bag of the embodiment, except that the overall length of the metal membrane catalytic filter bag of this comparative example is 3m.

[0050] Through a pilot test in a waste incineration plant, the performance of the dust removal and denitrification composite filter bag of the embodiment of the present application and the metal membrane catalytic filter bag of the comparative example were compared.

[0051] The specific pilot process is as follows: the flue gas (500-550℃) is drawn out from the flue at the superheater inlet, and then the bag zone flue gas temperature is controlled to 300-400℃ by adjusting the fan frequency or adding cold air from the cold air valve (if necessary). The working flue gas volume is 1075-2000m 3 / h enters the integrated dust and nitrate treatment unit. After dust removal and denitrification, the clean flue gas is introduced into the low-temperature superheater outlet flue via a matching induced draft fan, with the added resistance overcome by the matching fan. Dust intercepted by the filter bags is discharged into a steel drum at the bottom, where it is manually discharged regularly. The compressed air required for bag spraying is drawn from a nearby storage tank or compressed air pipeline. The reducing agent required for denitrification is led from a nearby ammonia water tank to the ammonia spray system. The power interface is drawn from a nearby power distribution cabinet.

[0052] The pilot test was conducted in two phases. In the first phase, the metal membrane catalytic filter bag of the comparative example was installed in the dust and nitrate integrated device. In the second phase, the dust removal and denitrification composite filter bag of the embodiment was installed in the dust and nitrate integrated device. The fan frequency, bag area pressure difference, total pressure difference of the dust and nitrate integrated device, inlet and outlet flue gas temperature and NO X The concentrations were measured and recorded, and the results are shown in Tables 1 and 2.

[0053] Table 1 Summary of data of the first phase of pilot test

[0054]

[0055]

[0056] The detailed trends of various data before the start and stop of the pilot phase I are as follows: Figure 4 As shown, the detailed trends of various data after the start and stop of the pilot phase I are as follows Figure 5 shown.

[0057] Table 2 Summary of data of the second phase of pilot test

[0058]

[0059] The detailed trends of various data before the start and stop of the pilot phase II furnace are as follows Figure 6 As shown, the detailed trends of various data after the start-up and shutdown of the pilot phase II furnace are as follows Figure 7 shown.

[0060] By comparison, we can find that:

[0061] At the beginning of the first phase of the pilot test, the average pressure difference in the bag area of ​​the metal membrane catalytic filter bag of the control group was 295Pa, and the average total pressure difference of the dust and saltpeter integrated device was 512Pa. After a shutdown and restart, the average pressure difference in the bag area increased significantly to 778Pa, and the average total pressure difference of the dust and saltpeter integrated device increased to 1009Pa. Through sampling, disassembly and laboratory analysis of the filter bags, it was found that the middle and lower parts of the filter bags had become sticky, and the lower part was covered with wet filter cakes, and the active substances of the internal catalysts were inactivated by alkali metal poisoning. It is speculated that when the waste incinerator is started and stopped, due to low temperature, condensation of flue gas causes the filter cake in the middle and lower sections to become sticky and unable to be cleaned, and the alkali and alkaline earth metals therein dissolve in liquid water and penetrate into the catalytic filter bag layer, causing the catalyst to be inactivated by alkali poisoning.

[0062] At the beginning of the second phase of the pilot test, the average pressure difference in the bag area of ​​the dust removal and denitrification composite filter bag of the embodiment was 241Pa, and the average total pressure difference of the dust and denitrification integrated device was 461Pa. After a shutdown and restart, the average pressure difference in the bag area was 613Pa, and the average total pressure difference of the dust and denitrification integrated device was 915Pa. Through sampling, disassembly and laboratory analysis of the filter bags, it was found that the middle and lower parts of the filter bags also had a sticky bag phenomenon, and the lower part was covered with a wet filter cake, but the humidity of the filter cake was lower than that of the control example. It is speculated that this is because water vapor in the embodiment is easier to pass through the surface of the metal membrane without being intercepted by the catalytic filter bag. The segmented design of the embodiment completely avoids the phenomenon of catalyst alkali metal poisoning in the middle and lower structures.

[0063] The average denitrification efficiency of the metal membrane catalytic filter bag in the comparative example was above 98% in the early stage. After a shutdown and restart, the average denitrification efficiency dropped to below 85%. The average denitrification efficiency of the dust removal and denitrification composite filter bag in the embodiment was above 98%, indicating that the structural design of the present application greatly reduces the probability of the catalytic layer being deactivated by being immersed in liquid water containing alkali metals when starting and stopping the furnace, thereby achieving stability and high efficiency of denitrification.

[0064] The above describes the specific embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

[0065] In the description of this application, it should be understood that the terms "upper", "lower", "inner", "outer", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting this application. The wording 'comprising' does not exclude the presence of elements or steps not listed in the claims. The simple fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used for improvement. Any reference signs in the claims should not be interpreted as limiting the scope.

Claims

1. A composite filter bag for dust removal and denitrification, comprising a plurality of functional filter bags linearly arranged from top to bottom and a plurality of connecting parts respectively arranged between two adjacent functional filter bags, characterized in that: The functional filter bag includes a metal membrane catalytic filter bag and a metal membrane filter bag; the first section of the dust removal and denitrification composite filter bag is the metal membrane catalytic filter bag, and the rest are the metal membrane filter bags; the connecting part is a flange structure, and the flange structure is embedded with a coated SCR honeycomb catalyst.

2. The dust removal and denitrification composite filter bag according to claim 1, characterized in that: The functional filter bag has at least 3 sections, and the length of each section is 0.6-1.1m.

3. The dust removal and denitrification composite filter bag according to claim 1 is characterized in that: The overall length of the dust removal and denitrification composite filter bag does not exceed 8.0m.

4. The dust removal and denitrification composite filter bag according to claim 1, characterized in that: The metal membrane catalytic filter bag is a metal membrane filter bag with a catalytic layer.

5. The dust removal and denitrification composite filter bag according to claim 4 is characterized in that: The catalytic layer is a nickel foam loaded catalyst layer.

6. The dust removal and denitrification composite filter bag according to claim 1, characterized in that: The flange structure includes an upper flange and a lower flange, the bottom of the upper flange is flush with the bottom of the coated SCR honeycomb catalyst, the upper flange is provided with a threaded outer ring, the lower flange is provided with a threaded inner ring, the upper flange and the lower flange are detachably connected by threads, the upper flange is welded to the bottom of the functional filter bag, and the lower flange is welded to the top of the functional filter bag.

7. The dust removal and denitrification composite filter bag according to claim 1, characterized in that: The bottom of the last section of the dust removal and denitration composite filter bag is sealed by a flange cover.

8. A filtering method for a dust removal and denitration composite filter bag as claimed in any one of claims 1 to 7, characterized in that: The specific process is as follows: S1. Air intake: Flue gas enters the dust and saltpeter integrated device through the flue. During the air intake process, the flue gas temperature can be controlled by adjusting the fan frequency or adding cold air through the cold air valve; S2, dust removal and denitrification: the flue gas enters the dust removal and denitrification composite filter bag, and the dust in the flue gas is blocked on the surface of the dust removal and denitrification composite filter bag to complete the dust removal; NOx is removed by the catalytic layer in the metal membrane catalytic filter bag and the coated SCR honeycomb catalyst in the flange structure to complete the denitrification; S3. Exhaust: The clean flue gas after dust removal and denitrification is discharged through the outlet flue.

9. The filtering method of the dust removal and denitration composite filter bag according to claim 8, characterized in that: In S2, the metal membrane catalytic filter bag is far away from the condensation area.

10. The filtering method of the dust removal and denitration composite filter bag according to claim 9, characterized in that: The condensation area is located in the lower middle part of the dust removal and denitrification composite filter bag. When the flue gas temperature reaches the condensation condition, liquid water will form in the condensation area.

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