Efficient and economical SCR catalyst front carbon strip filtering and trapping device

Abstract

The invention relates to the field of flue gas purification treatment, in particular to an efficient and economical SCR (Selective Catalytic Reduction) catalyst preposed carbon strip filtering and trapping device which comprises a carbon strip filter screen and three layers of SCR catalysts which are arranged in a flue outlet, and the flue is a vertical flue; the carbon strip filter screen covers the section of the vertical flue, and a plurality of filter caps protruding upwards are distributed on the carbon strip filter screen; a plurality of layers of grid blades are arranged on the filter cap along the height direction; the three layers of SCR catalysts are located on the lower portion, soot blowers are arranged on the upper portion and the lower portion of each layer of SCR catalyst, and the soot blowers blow air towards the filter cap. On one hand, carbon strips in flue gas entering the SCR catalyst are filtered, and the catalyst is prevented from being blocked; on the other hand, carbon strip particles can be recycled, mechanical incomplete combustion heat loss is reduced, and boiler heat efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of flue gas purification and treatment, and in particular to a high-efficiency and economical SCR catalyst pre-filter and collection device. Background Technology

[0002] Biomass direct combustion power generation is an important way to utilize agricultural and forestry biomass resources on a large scale. "Zero-carbon" biomass direct combustion power generation is playing an increasingly prominent role in my country's energy system. In recent years, with increasingly stringent environmental protection requirements, SCR catalyst technology has been widely used to reduce NOx emissions during biomass combustion. Currently, biomass boilers use SCR denitrification technology before flue gas dust removal, employing alkali-resistant metal denitrification catalysts for direct denitrification in the tail flue. This denitrification method fully utilizes the temperature of the tail flue, reducing biomass denitrification costs and energy consumption. However, it also presents several problems, the most significant being catalyst poisoning, deactivation, and blockage. For agricultural and forestry biomass, a large number of char particles are carried into the tail flue by the flue gas during combustion. If left untreated, this can cause blockage of the SCR catalyst, increasing catalyst flow resistance, affecting catalyst efficiency, increasing induced draft fan power consumption, and ultimately reducing overall system efficiency.

[0003] In traditional biomass direct-fired boilers, the flue gas carries a large amount of fly ash and carbon bar particles during the primary and secondary air purging processes in the furnace. These large carbon bar particles can clog the SCR catalyst in the tail flue, affecting its activity and reducing denitrification efficiency. Furthermore, as carbon bar particles accumulate, significant flow resistance is generated before and after the SCR catalyst, reducing system economics. Therefore, it is necessary to filter and separate large-sized carbon bar particles from the flue gas to improve the operating efficiency of the SCR catalyst. In addition, carbon bar particles have a high calorific value; fully recovering and utilizing the carbon bars can effectively reduce heat loss from incomplete combustion in the boiler and improve combustion efficiency. Summary of the Invention

[0004] The purpose of this invention is to solve the problems existing in the prior art by proposing a highly efficient and economical SCR catalyst pre-filter and collection device.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A high-efficiency and economical SCR catalyst pre-filter collection device includes a three-layer SCR catalyst with a carbon strip filter screen installed in the flue outlet, and the flue is a vertical flue. The charcoal bar filter screen is located at the top, covering the cross-section of the vertical flue. Multiple upward-protruding filter caps are distributed on the charcoal bar filter screen, and the filter caps are also filter screen structures. The filter cap is provided with multiple layers of grid blades along the height direction. The grid blades are arranged at an angle, and the flue gas back-blowing channel is formed between the adjacent grid blades. The flue gas back-blowing channel faces downward at an angle. The three-layer SCR catalyst is located at the bottom, consisting of an upper catalyst layer, a middle catalyst layer, and a lower catalyst layer; each SCR catalyst layer is equipped with a soot blower at the top and bottom, with the soot blowers blowing air towards the filter cap.

[0006] As a further preferred option, the filter cap has an inverted cone structure.

[0007] As a further preferred option, the angle between the grid blades and the horizontal plane is 45°-70°.

[0008] As a further preferred option, the angle between the grid blades and the horizontal plane is 60°.

[0009] As a further preferred option, the gap between adjacent grid blades is 3mm.

[0010] As a further preferred option, the mesh of the carbon strip filter and the filter cap is rectangular, with a width of 1mm-2mm and a length of 2mm-3mm. As a further preferred embodiment, the mesh size of the carbon strip filter and the filter cap is 1mm*2mm.

[0011] As a further preferred option, the vertical flue on the side of the carbon bar filter screen is equipped with an ash removal device, which is an ash hopper or a dust collector, with the purpose of collecting the intercepted ash.

[0012] Beneficial effects: This invention provides a highly efficient and economical method and apparatus for filtering and collecting carbon strips before SCR catalyst. This filtering and collecting device filters the carbon strips in the flue gas entering the SCR catalyst to prevent catalyst blockage. On the other hand, it can recover carbon strip particles, reduce heat loss from incomplete mechanical combustion, and improve boiler thermal efficiency. In addition, the device is simple, reliable, low-cost, and easy to install, making it a highly efficient and economical method for solving the deactivation and blockage of SCR catalysts in biomass boilers.

[0013] Specifically, it includes the following advantages: 1. This invention provides a carbon strip particle filtration and analysis device that combines a metal louver grid and a metal filter screen of a certain size in front of the SCR catalyst. This device can effectively filter and separate large carbon strip particles, thereby avoiding blockage of the SCR catalyst by large carbon strip particles and thus improving the SCR catalytic efficiency.

[0014] 2. Because this invention filters carbon particles in flue gas, it can reduce flue resistance, reduce induced draft fan power, and improve system efficiency.

[0015] 3. This invention can recycle charcoal granules, reduce heat loss from incomplete mechanical combustion, and improve boiler thermal efficiency. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the filter cap structure; Figure 3 This is a schematic diagram illustrating the filtration effect of Embodiment 1 of the present invention; Figure 4 This is a schematic diagram illustrating the filtration effect of Embodiment 2 of the present invention; Figure 5 This is a schematic diagram illustrating the filtration effect of Embodiment 3 of the present invention; Figure 6 This is a schematic diagram illustrating the filtration effect of Embodiment 4 of the present invention; Figure 7 This is a schematic diagram illustrating the filtration effect of Embodiment 5 of the present invention; Figure 8 This is a schematic diagram illustrating the distribution characteristics of the flue gas flow field by the screen mesh of the present invention; Figure 9 This is a graph showing the relationship between the pressure drop across the filter and the flue gas velocity. Figure 10 This is a simulation diagram of the filtration effect of the combined grid and filter structure on the carbon strip. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0018] like Figure 1 The diagram shows a process flow and installation of a high-efficiency, economical SCR catalyst pre-filter carbon strip collection system. The flue gas temperature at the reactor inlet is approximately 360℃, which is within the ideal temperature range for the SCR catalyst. The flue gas carries particulate matter such as fly ash and carbon strips at a concentration of 5 g / Nm³. 3 The NOx concentration in the inlet flue gas is approximately 250 mg / Nm³. 3 .

[0019] The flue gas carrying particulate matter enters the inlet flue 1, then passes through the horizontal flue 2, and enters the vertical flue 3 where the SCR catalyst is located. Three layers of SCR catalyst are arranged in the vertical flue 3, including the upper catalyst layer 6, the middle catalyst layer 7, and the lower catalyst layer 8.

[0020] A carbon strip filter 4 is installed on the upper part of the catalyst layer. The carbon strip filter 4 has an inverted cone-shaped filter cap 41, which is also a filter structure. The pore size and installation angle of the carbon strip filter 4 and the filter cap 41 can be adjusted. Based on the carbon strip size, a pre-filter with a pore size of 1mm*2mm can effectively filter the carbon strips, achieving a filtration efficiency of over 99%. The length of the carbon strip passing through the filter does not exceed 5mm, effectively ensuring that the SCR catalyst is not clogged.

[0021] Furthermore, during the process of the filter screen intercepting carbon particles alone, filter screen clogging is prone to occur. To address this problem, another important structure of the present invention includes grid blades 42 combined with the filter screen. Specifically, multiple layers of grid blades 42 are arranged along the height direction on the filter cap 41. The grid blades 42 are arranged at an angle, and the flue gas backflow channel formed between adjacent grid blades 42 faces downwards at an angle. Figure 2 As shown, the grid blades 42 have an inclination angle of 60° and a gap of 3mm. The grid blades 42 can effectively intercept large-sized carbon particles in the initial stage. Since the particles are denser than the flue gas, they are blocked by the louvered grid due to gravity in the gap area. The carbon particles flow down the direction of the louver inclination angle to the lower part of the filter screen. Since a large number of carbon particles do not come into contact with the filter cap 41 in the middle and upper part, the clogging coverage area of ​​the overall filter screen by carbon particles can be reduced.

[0022] A soot blower 5 is installed at the bottom of the filter screen 4. Its main function is to periodically back-blow the carbon particles on the filter screen, and then discharge the carbon particles through the ash removal device into the vertical flue 3. The carbon particles have a high carbon content and a high calorific value. They are injected back into the boiler as fuel for combustion to reduce heat loss from incomplete mechanical combustion and improve boiler efficiency.

[0023] Numerical simulation results on the separation effect of the SCR pre-filter (1) Filtering effect of screen Example 1: The filtration effect of a 1mm*2mm screen arranged at a 45° angle on charcoal strips (3mm in length), as shown... Figure 3 As shown, for a 1mm*2mm filter screen, with an arrangement angle of 45°, it can filter most of the 3mm carbon strips, with a small portion of the carbon strips escaping from the filter screen.

[0024] Example 2: The filtration effect of a 1mm*2mm screen arranged at a 70° angle on charcoal strips (3mm in length), as shown... Figure 4 As shown, for a 1mm*2mm filter, increasing the arrangement angle to 70° can filter most of the 3mm carbon strips, with a small portion escaping from the filter. The filtration effect is improved due to the reduced projected area of ​​the filter mesh.

[0025] Example 3: The filtration effect of a 1mm*3mm screen arranged at a 70° angle on charcoal strips (3mm in length), as shown below. Figure 5 As shown, for a 1mm*3mm filter screen, with an arrangement angle of 70°, it can filter most of the 3mm carbon strips, with a small portion of the carbon strips escaping from the filter screen.

[0026] Example 4: The filtration effect of a 2mm*2mm screen arranged at a 70° angle on charcoal strips (3mm in length), as shown... Figure 6 As shown, for a 2mm*2mm filter screen arranged at a 70° angle, it can filter most of the 3mm carbon strips, with a small portion escaping through the filter screen. Due to the larger pore size, the filtration effect is slightly weakened.

[0027] Example 5: The filtration effect of a 2mm*2mm screen arranged at a 70° angle on charcoal strips (8mm in length), as shown... Figure 7 As shown, a 2mm*2mm filter screen arranged at a 70° angle can filter all 8mm carbon particles. Therefore, the screen can effectively intercept and filter large carbon particles, protecting the SCR catalyst from clogging.

[0028] (2) The effect of screen mesh on flue gas flow field distribution characteristics like Figure 8 As shown, for a 1mm*2mm filter screen, due to its low porosity, the filter screen generates a certain resistance to flue gas flow. CFD simulation results show that when the flue gas velocity is 5m / s, the flow resistance generated by the filter screen is 54Pa. When the flue gas passes through the filter screen openings, a certain acceleration and throttling process occurs, causing a pressure drop. The relationship between the pressure drop before and after the filter screen and the flue gas velocity is shown in the figure. Figure 9 As shown.

[0029] (3) Simulation of the effect of louvered grid and filter screen combination structure on carbon strip filtration effect Further simulations were conducted to examine the filtration effect of the carbon strip filter with its combination of louvered grids and a filter screen. The results are as follows: Figure 10 As shown.

[0030] It can be seen that the louvered grid significantly improves the flow field within the SCR flue. Under the guidance of the louvered grid, the flue gas flows obliquely upward. Since the particles are denser than the flue gas, they are subjected to centrifugal force in the gap area of ​​the louvered grid and are blocked and intercepted by the louvered grid. The carbon strips flow downstream along the louvered angle to the lower area of ​​the filter screen. Since a large number of carbon strip particles do not come into contact with the middle and upper part of the filter screen, the clogging of the filter screen by carbon strip particles is significantly reduced, which plays an important role in the long-term temperature operation of the SCR pre-filter.

[0031] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-efficiency and economical SCR catalyst pre-filter and collection device, characterized in that: Includes a carbon strip filter (4) installed in the flue outlet and a three-layer SCR catalyst, the flue being a vertical flue (3). The charcoal strip filter (4) is located at the top and covers the cross section of the vertical flue (3). Multiple filter caps (41) protruding upwards are distributed on the charcoal strip filter (4), and the filter caps (41) are also filter structures. The filter cap (41) is provided with multiple grid blades (42) along the height direction. The grid blades (42) are arranged at an angle. The flue gas back-blowing channel is formed between the adjacent grid blades (42) and faces downwards. The three-layer SCR catalyst is located at the bottom, namely the upper catalyst (6), the middle catalyst (7) and the lower catalyst (8); each layer of SCR catalyst is equipped with a soot blower (5) at the top and bottom, and the soot blower (5) blows air towards the filter cap (41).

2. The efficient and economical SCR catalyst pre-filter collection device according to claim 1, characterized in that: The filter cap (41) has an inverted conical structure.

3. The efficient and economical SCR catalyst pre-filter collection device according to claim 1, characterized in that: The angle between the grid blade (42) and the horizontal plane is 45°-70°.

4. The efficient and economical SCR catalyst pre-filter and collection device according to claim 3, characterized in that: The angle between the grid blade (42) and the horizontal plane is 60°.

5. The efficient and economical SCR catalyst pre-filter collection device according to claim 1, characterized in that: The gap between adjacent grid blades (42) is 3 mm.

6. The efficient and economical SCR catalyst pre-filter and collection device according to claim 1, characterized in that: The mesh of the carbon strip filter (4) and the filter cap (41) is rectangular, with a width of 1mm-2mm and a length of 2mm-3mm.

7. The efficient and economical SCR catalyst pre-filter and collection device according to claim 6, characterized in that: The mesh size of the carbon strip filter (4) and filter cap (41) is 1mm*2mm.

8. The efficient and economical SCR catalyst pre-filter and collection device according to claim 1, characterized in that: The vertical flue (3) on the side of the carbon strip filter (4) is equipped with an ash removal device.

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