Dust removal device and system suitable for ultralow emission of flue gas of alkali recovery furnace in papermaking industry

Abstract

The utility model discloses a dust removal device and system suitable for ultra-low smoke emission of an alkali recovery furnace in the papermaking industry. The dust removal device comprises a shell, a pulse valve assembly arranged at the upper end in the shell, a filter assembly arranged in the middle of the shell, an ash bucket arranged at the bottom of the shell, an ash bucket electric heater arranged on the outer side of the ash bucket, a main discharging pipe arranged at the bottom end of the ash bucket, and a star-shaped discharger arranged on the main discharging pipe. The tail end of the discharging main pipe is connected with an ash dissolving device. Tiny particles in flue gas are intercepted through the filter assembly, compressed air is connected through the pulse valve assembly, and the compressed air is sprayed to the surface of the filter bag, so that the fine particles are effectively removed, and a downstream catalyst can be prevented from being blocked and poisoned. The ash bucket electric heating device is arranged on the outer side of the ash bucket, so that alkali ash in the ash bucket is kept at the dew point temperature or above, the phenomenon that low-temperature and high-moisture-content alkali fly ash absorbs moisture and is hardened on the inner surface of the ash bucket is effectively avoided, and accumulated ash in the ash bucket is conveyed to the ash dissolving device through flushing water pressurized by the hydraulic ash conveying pump to be dissolved again and recycled. And resources can be continuously used.

Description

Technical Field

[0001] The utility model relates to the technical field of gaseous particulate matter purification, and particularly relates to a dust removal device and system suitable for ultra-low emission of flue gas from an alkali recovery furnace in the paper-making industry. Background Art

[0002] An alkali recovery furnace is a chemical reaction device that reacts carbon, sodium, and sulfur in pulping black liquor to generate Na2CO3 and Na2S. After causticization, Na2CO3 generates NaOH, which is reused for pulping together with Na2S. It is one of the core devices in an alkaline chemical pulp production line. While recovering the alkali used in pulping production, it also provides energy for production and treats the malodorous gases generated by the pulping production line and the alkali recovery system.

[0003] The flue gas of an alkali recovery furnace has the following characteristics:

[0004] The temperature of the flue gas at the outlet is low (about 180 - 200 °C), the moisture content is high (up to 25 - 30%), the oxygen content is low, the concentrations of SO2 and SO3 are very low, and the main pollutants are NOx and dust. The main components of the dust in the alkali recovery furnace include Na2CO3 (Na2SO4), Na2S, etc. The dust is alkaline, has strong corrosiveness, is prone to caking, has a small particle size, is fluffy in accumulation, is easy to bridge, and has poor fluidity. The alkali metals in the dust have a great influence on the denitrification efficiency of the SCR denitrification catalyst and are prone to cause alkali metal poisoning of the catalyst.

[0005] Currently, the general process flow for the flue gas of an alkali recovery furnace is to remove dust first and then perform low-temperature denitrification. Due to the relatively low environmental protection emission requirements for the flue gas of early alkali recovery furnaces and the poor dust removal effect of bag filters due to the characteristics of alkali ash, dust removal generally uses a separate electrostatic precipitator. Due to certain failure rates of the electrostatic precipitator, there are problems with unstable particulate matter compliance emissions, unable to meet the requirements of stable ultra-low emissions of particulate matter in the flue gas, and it is easy to damage the downstream low-temperature SCR denitrification catalyst and shorten the service life of the catalyst.

[0006] In view of the unstable emission concentration of particulate matter in the flue gas after electrostatic precipitation and in order to protect the downstream catalyst, some solutions have also been proposed in the prior art.

[0007] For example, the patent with the patent number CN216418936U and the name of "A Simple Dust Removal Device for SCR Denitrification Flue Gas in the Paper-Making Industry" provides a simple filtering device that uses an electro-foam metal filter screen to perform secondary filtration on the particulate matter in the flue gas. However, the above simple device has certain drawbacks: such as low dust removal efficiency, inability to operate automatically, requiring manual cleaning, high labor intensity, affecting the operation of the denitrification system during cleaning, and being unable to ensure ultra-low emissions of pollutants in the flue gas.

[0008] In addition, there is also a patent with the patent number CN221015068 and the name of "a large particle ash interception device for alkali recovery boilers that can automatically remove ash". This device is only suitable for intercepting large particle dust and has limited ability to handle fine dust in alkali recovery flue gas. Content of the Utility Model

[0009] To solve the technical problems mentioned in the background art, the present utility model provides a dust removal device and system suitable for ultra-low emission of flue gas from alkali recovery furnaces in the paper-making industry.

[0010] The present utility model adopts the following technical solutions: A dust removal device suitable for ultra-low emission of flue gas from alkali recovery furnaces in the paper-making industry, the dust removal device includes a housing; a flue gas inlet and a flue gas outlet are arranged on the left and right sides of the housing; a pulse valve assembly is arranged at the upper end inside the housing; a filter assembly is arranged in the middle; a ash hopper is arranged at the bottom; the pulse valve assembly is connected to a compressed air storage tank through a pipeline, and a pipeline electric heater is connected to the pipeline between the two; the inner ash sliding angle of the ash hopper is greater than 65°, and an arc plate is installed on the inner side of the adjacent wall intersection angle inside the ash hopper; an ash hopper electric heater is arranged outside the ash hopper; a discharge main pipe is arranged at the bottom end of the ash hopper; a star-shaped discharger for controlling ash discharge is arranged on the discharge main pipe; the end of the discharge main pipe is connected to a ash dissolving device; the ash dissolving device and a hydraulic ash transportation water tank are connected through a hydraulic ash transportation pump pipeline, and the flushing water in the hydraulic ash transportation water tank is pressurized by the hydraulic ash transportation pump to send the accumulated ash in the ash hopper to the ash dissolving device for dissolution and recycling.

[0011] Furthermore, the filter assembly includes filter bags and cage; the filter bags include PTFE needle felt and PTFE film; the cage is made of 304 or 316L stainless steel.

[0012] Furthermore, the cover plate of the pulse valve assembly adopts a double-layer cover plate, with a detachable high-temperature resistant aluminum silicate heat preservation cloth bag arranged on the inner layer cover plate and a thickened rock wool layer arranged on the outside.

[0013] Furthermore, the present invention also provides a system suitable for ultra-low emission of flue gas from alkali recovery furnaces in the paper-making industry, including an alkali recovery furnace, and an electrostatic precipitator, a low-temperature SCR denitration reactor, a booster fan, a flue gas cooler, an induced draft fan and an emission chimney that are connected to the alkali recovery furnace through pipelines; the above-mentioned dust removal device suitable for ultra-low emission of flue gas from alkali recovery furnaces in the paper-making industry is connected between the electrostatic precipitator and the low-temperature SCR denitration reactor.

[0014] Compared with the prior art, the advantages of the present utility model are as follows: The dust removal device designed for the ultra-low emission of flue gas from the alkali recovery furnace in the paper-making industry intercepts tiny particulate matters in the flue gas through a filtering component, connects compressed air through a pulse valve component, and sprays it onto the surface of the filter bag to effectively remove fine particulate matters, and at the same time can prevent the downstream catalyst from being blocked and poisoned. An electric heater is arranged outside the ash hopper to keep the alkali ash inside the ash hopper above the dew point temperature, effectively preventing and avoiding the hygroscopicity of the low-temperature and high-moisture alkaline fly ash from caking on the inner surface of the ash hopper. The accumulated ash in the ash hopper is sent to the ash dissolving device through the flushing water pressurized by the hydraulic ash conveying pump to be dissolved and recycled again, enabling the resources to be sustainably used.

[0015] The dust removal system designed for the ultra-low emission of flue gas from the alkali recovery furnace in the paper-making industry is connected with the above-mentioned dust removal device after an electrostatic precipitator, which can stably and effectively remove particulate matters in the flue gas, has high reliability, low failure rate, high automation degree, and no secondary pollution. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of the overall structure of the dust removal device suitable for the ultra-low emission of flue gas from the alkali recovery furnace in the paper-making industry of the present utility model;

[0017] Figure 2 It is a schematic diagram of the overall structure of the dust removal system suitable for the ultra-low emission of flue gas from the alkali recovery furnace in the paper-making industry of the present utility model.

[0018] Wherein:

[0019] 1 - Alkali recovery furnace, 2 - Electrostatic precipitator, 3 - Bag filter, 4 - Low-temperature SCR denitration reactor, 5 - Booster fan, 6 - Gas cooler, 7 - Induced draft fan, 8 - Chimney

[0020] 3 - 1 - Shell, 3 - 2 - Filtering component, 3 - 3 - Compressed air storage tank, 3 - 4 - Pipeline electric heater, 3 - 5 - Pulse valve component, 3 - 6 - Ash hopper, 3 - 7 - Electric tracing heat for ash hopper, 3 - 8 - Rotary valve, 3 - 9 - Hydraulic ash conveying water tank, 3 - 10 - Hydraulic ash conveying pump, 3 - 11 - Ash dissolving device. Detailed Embodiment

[0021] Hereinafter, for the convenience of those skilled in the art to understand the technical solution of the present utility model, further description will be made with reference to the accompanying drawings. It should be understood that these descriptions are exemplary and not intended to limit the scope of the present utility model.

[0022] In the following detailed description, for the sake of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present utility model. However, it is evident that one or more embodiments can be implemented without these specific details. Additionally, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concepts of the present utility model.

[0023] As Figure 1 shown, the dust removal device 3 applicable to the ultra-low emission of flue gas from alkali recovery furnaces in the paper-making industry, which the present utility model relates to, includes a housing 3-1. A flue gas inlet and a flue gas outlet are arranged on the left and right sides of the housing 3-1. A pulse valve assembly 3-5 is arranged at the upper end inside the housing, a filter assembly 3-2 is arranged in the middle, and a hopper 3-6 is arranged at the bottom. During specific implementation, the filter assembly 3-2 includes filter bags and bag cages; the filter bags include PTFE needle felts and PTFE films. The aperture of the filter bags after film coating is in the micron level, which can effectively prevent water vapor, oil, and fine dust particles from entering the interior of the filter material, facilitating dust cleaning, prolonging the service life of the filter bags, and preventing bag clogging. The bag cages are made of 304 or 316L stainless steel to prevent corrosion. The flue gas after electrostatic dust removal flows through the filter bags, and the particulate matter in the flue gas is intercepted on the outer surface of the filter bags, further removing the fine dust in the flue gas.

[0024] The pulse valve assembly is communicated with a compressed air storage tank 3-3 through a pipeline, and a pipeline electric heater 3-4 is connected to the pipeline between the two. When the differential pressure at the inlet and outlet of the dust removal device 3 rises to the dust cleaning set value, the compressed air in the compressed air storage tank 3-3 is heated by the pipeline electric heater 3-4, and the temperature of the heated compressed air is automatically controlled by a PLC. The heated compressed air further enters the pulse valve assembly 3-5 and is sprayed onto the surface of the filter bags through the dust cleaning pipeline, causing the alkali ash on the surface of the filter bags to fall into the hopper 3-6.

[0025] In this embodiment, the inner ash sliding angle of the hopper 3-6 is greater than 65°. The inner lining of the hopper is made of stainless steel 304, and an arc plate is installed on the inner side of the adjacent wall intersection angle inside the hopper 3-6 to ensure that the inner surface of the hopper is smooth and not prone to ash hanging. An ash hopper electric heater 3-7 is arranged on the outer side of the hopper 3-6 to keep the alkali ash inside the hopper above the dew point temperature, preventing the alkali ash from absorbing moisture and caking on the inner surface plate of the hopper. During specific implementation, a vibrator, an air cannon, etc. can be configured on the inner side of the hopper 3-6.

[0026] A discharge main pipe is provided at the bottom of the ash hopper 3-6, and a star-shaped discharger 3-8 for controlling ash discharge is provided on the discharge main pipe. The end of the discharge main pipe is connected to a ash dissolving device 3-11. The ash dissolving device 3-11 and the hydraulic ash transportation water tank 3-9 are connected by a pipeline through a hydraulic ash transportation pump 3-10. The flushing water in the hydraulic ash transportation water tank 3-9 is pressurized by the hydraulic ash transportation pump 3-10 to send the accumulated ash in the ash hopper 3-6 to the ash dissolving device 3-11 for dissolution and then recycling. During specific implementation, a water seal is designed for the pipeline at the valve outlet of the ash dissolving device 3-11 and the discharger 3-8 to prevent wet cold air from flowing back into the ash hopper and causing alkali ash caking. In this embodiment, the above ash cleaning, ash discharging and transportation processes can all be remotely and automatically controlled through the DCS in the control room.

[0027] During specific implementation, the top of the filter bag adopts a double-layer top cover, and a segmented high-temperature resistant aluminosilicate cloth bag for heat preservation is arranged in the interlayer and fixed by sewing. The cover plate of the pulse valve assembly 3-5 adopts a double-layer cover plate. A detachable high-temperature resistant aluminosilicate heat preservation cloth bag is arranged on the inner cover plate, and a thickened rock wool layer is arranged on the outside.

[0028] The dust removal device designed by the utility model is applicable to the ultra-low emission of flue gas from alkali recovery furnaces in the paper industry. It intercepts tiny particulate matters in the flue gas through a filtering component, connects compressed air through a pulse valve assembly, and sprays it onto the surface of the filter bag to effectively remove fine particulate matters, and at the same time prevent the downstream catalyst from being blocked and poisoned. An electric heater is arranged on the outside of the ash hopper to keep the alkali ash inside the ash hopper above the dew point temperature, effectively preventing the low-temperature and high-moisture-containing alkaline fly ash from absorbing moisture and caking on the inner surface of the ash hopper. The accumulated ash in the ash hopper is sent to the ash dissolving device for re-dissolution and recycling through the flushing water pressurized by the hydraulic ash transportation pump, enabling sustainable use of resources.

[0029] In addition, the utility model also provides an ultra-low emission system for flue gas from an alkali recovery furnace in the paper industry, including an alkali recovery furnace 1, an electrostatic precipitator 2, a low-temperature SCR denitration reactor 4, a booster fan 5, a gas cooler 6, an induced draft fan 7 and an emission chimney 8 which are connected to the alkali recovery furnace 1 through pipelines. The electrostatic precipitator 2 and the low-temperature SCR denitration reactor 4 are connected to the dust removal device 3 involved in this embodiment.

[0030] Under the action of the booster fan 5 and the induced draft fan 7, the flue gas at the outlet of the alkali recovery furnace 1 first enters the electrostatic precipitator 2, making the dust in the flue gas charged and adsorbed on the anode plate under the action of the electric field force, thereby collecting and removing the alkali ash in the flue gas. The outlet flue of the electrostatic precipitator 2 is connected to the dust removal device 3 of this embodiment. Through the physical interception of the filter bag, the alkali ash concentration in the flue gas is further reduced. The removal of NOx is achieved through the low-temperature denitration reactor 4. The resistance of the bag dust removal and SCR denitration system is overcome by the booster fan 5. The flue gas after dust removal and denitration enters the gas cooler 6 after being pressurized by the booster fan for heat recovery and reuse. The flue gas is discharged into the chimney 8 through the induced draft fan 7.

[0031] In the operation of this system, when the electrostatic precipitator 2 works normally, the bag filter 3 only bears a slight dust removal load, has low resistance, and has a low cleaning frequency. When the electrostatic precipitator fails, the bag filter can act as a "shield" for the catalyst, intercepting a large amount of alkali ash that suddenly rises, ensuring that particulate matter emissions meet standards while preventing alkali ash from poisoning the catalyst and avoiding clogging and poisoning of the catalyst.

[0032] In summary, the utility model is designed to be suitable for the ultra-low emission dust removal system of the flue gas of the alkali recovery furnace in the papermaking industry. The above-mentioned dust removal device is connected after the electrostatic precipitator, which can stably and effectively remove particulate matter in the flue gas, has high reliability, low failure rate, high degree of automation, and no secondary pollution.

[0033] The above embodiments are merely descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the protection scope determined by the claims of the present invention.

Claims

1. A dust removal device applicable to the ultra-low emission of flue gas from alkali recovery furnaces in the paper-making industry, characterized in that, The dust removal device (3) includes a housing (3-1); a flue gas inlet and a flue gas outlet are provided on the left and right sides of the housing (3-1); a pulse valve assembly (3-5) is provided at the upper end inside the housing; a filter assembly (3-2) is provided in the middle; a hopper (3-6) is provided at the bottom; the pulse valve assembly (3-5) is communicated with a compressed air storage tank (3-3) through a pipeline, and a pipeline electric heater (3-4) is connected to the pipeline between the two; the inner ash-sliding angle of the hopper (3-6) is greater than 65°, and an arc plate is installed on the inner side of the intersection angle of the adjacent walls inside the hopper (3-6); a hopper electric heater (3-7) is provided outside the hopper (3-6); a discharge main pipe is provided at the bottom end of the hopper (3-6); a star-shaped discharger (3-8) for controlling ash discharge is provided on the discharge main pipe; the end of the discharge main pipe is connected to a ash dissolving device (3-11); the ash dissolving device (3-11) and a hydraulic ash conveying water tank (3-9) are communicated through a pipeline by a hydraulic ash conveying pump (3-10), and the flushing water in the hydraulic ash conveying water tank (3-9) is pressurized by the hydraulic ash conveying pump (3-10) to send the accumulated ash in the hopper (3-6) to the ash dissolving device (3-11) for dissolution and recycling.

2. The dust removal device applicable to ultra-low emission of flue gas from alkali recovery boilers in the paper-making industry according to claim 1, wherein The filter assembly (3-2) includes filter bags and cage; the filter bags include PTFE needle felt and PTFE film; the cage is made of 304 or 316L stainless steel.

3. The dust removal device applicable to ultra-low emission of flue gas from alkali recovery boilers in the paper-making industry according to claim 1, characterized in that, The cover plate of the pulse valve assembly (3-5) adopts a double-layer cover plate, a detachable high-temperature resistant aluminosilicate heat preservation cloth bag is arranged on the inner cover plate, and a thickened rock wool layer is arranged on the outside.

4. An ultra-low emission system for the flue gas of an alkali recovery furnace applicable to the paper-making industry, characterized in that, It includes an alkali recovery furnace (1), and an electrostatic precipitator (2), a low-temperature SCR denitration reactor (4), a booster fan (5), a flue gas cooler (6), an induced draft fan (7) and an emission chimney (8) which are connected to the alkali recovery furnace (1) through pipelines; the dust removal device (3) applicable to the ultra-low emission of the flue gas of the alkali recovery furnace in the paper-making industry described in any one of claims 1-3 is connected between the electrostatic precipitator (2) and the low-temperature SCR denitration reactor (4).

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