Air pre-heater ash removal device and ash removal method

Abstract

The invention relates to an air pre-heater ash removal device and an ash removal method. The ash removal method comprises the following steps: S1, pretreatment: closing an inlet and an outlet of an area to be subjected to ash removal, and confirming that the internal pressure of the area to be subjected to ash removal is stabilized at normal pressure; s2, high-temperature treatment: high-temperature gas is injected into the area to be dedusted, so that the temperature of the area to be dedusted reaches 1500-1600 DEG C; s3, low-temperature treatment is conducted, specifically, low-temperature gas is injected into the area to be subjected to ash removal, and the temperature of the area to be subjected to ash removal is reduced to 150 DEG C or below from 1500 DEG C to 1600 DEG C; s4, negative pressure dust collection: negative pressure is generated in the area to be dedusted to suck ash, and the sucked ash is filtered and collected; and S5, optionally, the method also comprises a safety protection step: when the temperature in the area to be dedusted exceeds 1600 DEG C and / or the pressure fluctuation is greater than 0.05 MPa, cutting off the supply of the high-temperature gas and / or releasing the pressure of the area to be dedusted. Efficient stripping and removing of stubborn ash are achieved, the overhaul quality of the air pre-heater is improved, and the service life of the air pre-heater is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of heat exchange equipment maintenance technology, and relates to a dust removal device and method that utilizes the synergistic effect of high-temperature melting and rapid cooling, particularly to a dust removal device and method for an air preheater. Background Technology

[0002] After long-term operation, air preheaters accumulate a large amount of calcium salts such as calcium sulfate, as well as ash such as silica, ammonium sulfate, and ammonium bisulfate on the surface of the heat storage elements. Stubborn ash (such as the hardened layer formed by high-temperature sintering) is difficult to remove completely using traditional cleaning methods. Existing technologies have significant drawbacks: mechanical cleaning easily damages the surface of the heat storage elements, leading to a shortened equipment lifespan; conventional airflow purging has an efficiency of less than 40% in removing hardened ash and requires frequent operation; chemical cleaning generates secondary pollution and corrodes metal components. These methods fail to fundamentally destroy the adhesion structure between the ash and the elements, resulting in poor cleaning performance and high equipment maintenance costs. Summary of the Invention

[0003] The purpose of this invention is to provide an air preheater cleaning device and cleaning method, which utilizes the synergistic effect of high-temperature melting and rapid cooling to achieve efficient stripping and removal of stubborn ash.

[0004] To achieve one aspect of the above-mentioned objectives, the present invention adopts the following technical solution: A dust removal device, comprising: The high-temperature gas generating unit includes a heating unit for heating an inert gas to generate high-temperature gas, a temperature control unit for controlling the heating temperature, and a high-temperature gas conveying unit for conveying the high-temperature gas to the ash-cleaning area. The cryogenic gas generating unit includes a cryogenic gas supply unit for providing a cryogenic inert gas as cryogenic gas, and a cryogenic gas conveying unit for conveying the cryogenic gas to the ash-cleaning area. A negative pressure suction unit includes a negative pressure forming unit for generating negative pressure within the area to be cleaned, and a filtering unit, wherein the negative pressure attracts ash to the filtering unit for filtration and collection; and An optional safety protection unit includes a detection unit for detecting the pressure and / or temperature of the area to be cleaned, and a protection unit for cutting off the supply of high-temperature gas and / or depressurizing the area to be cleaned when the pressure and / or temperature exceeds a preset value.

[0005] To achieve another aspect of the above-mentioned objective, the present invention also provides a dust removal method, the dust removal method comprising the following steps: S1. Pre-treatment: Close the inlet and outlet of the area to be cleaned, and confirm that the internal pressure of the area to be cleaned is stable at normal pressure; S2. High-temperature treatment: Inject high-temperature gas into the area to be cleaned, so that the temperature of the area to be cleaned reaches 1500℃~1600℃; S3. Low temperature treatment: Inject low temperature gas into the area to be cleaned to reduce the temperature of the area from 1500℃~1600℃ to below 150℃; S4. Negative pressure dust collection: A negative pressure is generated in the area to be cleaned to adsorb ash and filter and collect the attracted ash; S5. Optionally, it also includes a safety protection step: when the temperature in the area to be cleaned exceeds 1600°C and / or the pressure fluctuation is greater than 0.05 MPa, the supply of high-temperature gas is cut off and / or the pressure in the area to be cleaned is depressurized.

[0006] Compared with the prior art, the present invention has the following advantages: 1. Significantly improved dust removal efficiency: For air preheaters that have been in operation for more than one year, the removal rate of stubborn ash is high, and can even reach more than 95%. Compared with the traditional airflow purging method, the ash removal rate is significantly improved.

[0007] 2. Good equipment protection: Non-contact dust removal avoids mechanical damage, and inert gas is used during high-temperature stages to prevent component oxidation.

[0008] 3. Environmentally friendly and economical: No chemical agents are used throughout the process, and the ash collection rate is about 100%, achieving zero pollution; the cost of a single ash removal is lower than that of chemical cleaning methods, and the ash removal cycle is extended from 3 months to 12 months. Attached Figure Description

[0009] Figure 1 This is a system diagram of a dust removal device according to an embodiment of the present invention. Detailed Implementation

[0010] Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments without departing from the scope of the present invention, and the description herein is for illustrative purposes only and not intended to limit the present invention.

[0011] After long-term operation, the surface of the heat storage elements in an air preheater will accumulate a large amount of calcium salt ash, such as calcium sulfate. During use, high-temperature sintering will form a stubborn, hardened ash layer that is difficult to remove. Considering the thermophysical properties of calcium salts such as calcium sulfate, which have a melting point of approximately 1450°C and are prone to shrinkage and embrittlement at low temperatures, the inventors unexpectedly discovered that by utilizing the difference in the "high-temperature melting-low-temperature embrittlement" characteristics of calcium salts such as calcium sulfate, it is possible to achieve efficient stripping and removal of stubborn ash. Thus, the technical solution of this invention was proposed.

[0012] In one aspect of the present invention, a dust removal device is provided, the dust removal device comprising: The high-temperature gas generating unit includes a heating unit for heating an inert gas to generate high-temperature gas, a temperature control unit for controlling the heating temperature, and a high-temperature gas conveying unit for conveying the high-temperature gas to the ash-cleaning area. The cryogenic gas generating unit includes a cryogenic gas supply unit for providing a cryogenic inert gas as cryogenic gas, and a cryogenic gas conveying unit for conveying the cryogenic gas to the ash-cleaning area. A negative pressure suction unit includes a negative pressure forming unit for generating negative pressure within the area to be cleaned, and a filtering unit, wherein the negative pressure attracts ash to the filtering unit for filtration and collection; and Optional safety protection unit includes a detection unit for detecting the pressure and / or temperature of the area to be cleaned, and a protection unit for cutting off the supply of high-temperature gas and / or depressurizing the area to be cleaned when the pressure and / or temperature exceeds a preset value.

[0013] In the safety protection unit, when the pressure exceeds a preset value, the protection unit can cut off the supply of high-temperature gas, or the protection unit can cut off the supply of high-temperature gas while simultaneously depressurizing the area to be cleaned; when the temperature exceeds a preset value, the protection unit can depressurize the area to be cleaned, or the protection unit can cut off the supply of high-temperature gas while simultaneously depressurizing the area to be cleaned.

[0014] In this invention, it should be understood that the high temperature refers to a temperature above 1450°C, preferably 1500°C to 1600°C; the low temperature refers to a temperature below 150°C, preferably below 30°C, more preferably below 0°C, and there is no particular limitation on the lower limit value, for example, -200°C or absolute zero.

[0015] In one embodiment, the inert gas of the cryogenic gas and the inert gas of the high-temperature gas may be of the same or different types. The inert gas of the cryogenic gas is selected from one or more of nitrogen, helium, and argon, preferably nitrogen. The inert gas of the high-temperature gas is selected from one or more of nitrogen, helium, and argon, preferably nitrogen.

[0016] It should also be understood that, in this invention, "inert gas" refers to a gas in which the volume percentage of inert gas is ≥95%, preferably ≥95%, ≥96%, ≥97%, ≥98%, or ≥99%.

[0017] In one embodiment, the cryogenic gas supply unit is a liquid nitrogen storage tank. The capacity of the liquid nitrogen storage tank is not particularly limited and can be, for example, 0.05 m³. 3 ~10 m 3 0.5 m 3 ~10 m 3 1 m 3~10 m 3 or 5 m 3 ~10 m 3 .

[0018] In one embodiment, the gas outlet of the cryogenic gas delivery unit has an atomizing nozzle.

[0019] In one embodiment, the gas outlet of the cryogenic gas conveying unit is located above the area to be cleaned to ensure that the cryogenic gas uniformly covers the area. For example, the gas outlet of the cryogenic gas conveying unit is preferably located 0.1 m to 1 m above the area to be cleaned, more preferably 0.5 m to 1 m above the area to be cleaned, such as 0.2 m, 0.3 m, 0.4 m, 0.5 m, 0.6 m, 0.7 m, 0.8 m, or 0.9 m above the area to be cleaned.

[0020] In one embodiment, the heating unit can be any suitable heating unit known to those skilled in the art, without particular limitation. For example, it can be a burner, more specifically a natural gas burner. In order to quickly reach the temperature required by the present invention, the thermal power of the natural gas burner can be 50-100 kW.

[0021] In this invention, the high-temperature gas conveying unit can be made of a high-temperature resistant material, such as a high-temperature resistant pipe. In one embodiment, the high-temperature resistant material can be any high-temperature resistant material known in the art, including but not limited to corundum ceramic.

[0022] In one embodiment, the filtration unit is a filtration device capable of collecting ash particles larger than 100 mesh and smaller than 100 mesh separately. For example, filtration can be performed through a 100-mesh filter, and ash particles larger than 100 mesh and smaller than 100 mesh can be collected separately.

[0023] In one embodiment, the safety protection unit can be an automatic control system that includes a detection unit and a protection unit. When the pressure and / or temperature signal is detected to exceed a preset value, the system automatically cuts off the supply of high-temperature gas and / or depressurizes the area to be cleaned.

[0024] In one embodiment, the area to be cleaned is the region of the air preheater equipped with heat storage elements.

[0025] In another aspect of the present invention, a dust removal method is provided, the dust removal method comprising the following steps: S1. Pre-treatment: Close the inlet and outlet of the area to be cleaned, and confirm that the internal pressure of the area to be cleaned is stable at normal pressure; S2. High-temperature treatment: Inject high-temperature gas into the area to be cleaned, so that the temperature of the area to be cleaned reaches 1500℃~1600℃; S3. Low temperature treatment: Inject low temperature gas into the area to be cleaned to reduce the temperature of the area from 1500℃~1600℃ to below 150℃; S4. Negative pressure dust collection: A negative pressure is generated in the area to be cleaned to attract ash, and the attracted ash is filtered and collected.

[0026] Optionally, in order to prevent damage to the components (or equipment) in the area to be cleaned, the method may further include S5, a safety protection step, which is: when the temperature in the area to be cleaned exceeds 1600°C and / or the pressure fluctuation is >0.05 MPa, the supply of high-temperature gas is cut off and / or the pressure in the area to be cleaned is depressurized.

[0027] In safety protection step S5, when the pressure exceeds the preset value, the supply of high-temperature gas can be cut off, or the supply of high-temperature gas can be cut off while depressurizing the area to be cleaned; when the temperature exceeds the preset value, the area to be cleaned can be depressurized, or the protection unit can cut off the supply of high-temperature gas while depressurizing the area to be cleaned.

[0028] It should also be understood that the "ash content" or "shed ash content" in this invention includes loose ash content already present in the area to be cleaned and ash content shed from the surface of the components in the area to be cleaned after being processed by the device or method of this invention.

[0029] In one embodiment, in the high-temperature treatment step S2, the holding time of the area to be cleaned at 1500℃~1600℃ can be adjusted according to the ash thickness so that the calcium salt ash such as calcium sulfate can be completely melted and form a peeling gap with the surface of the component in the area to be cleaned. For example, the holding time is more than 10 seconds and less than 5 minutes, preferably 30 seconds to 60 seconds.

[0030] In one embodiment, the temperature of the high-temperature gas is 1500°C to 1600°C.

[0031] In one embodiment, the temperature of the cryogenic gas is below 150°C, preferably below 30°C, and more preferably below 0°C. The temperature of the cryogenic gas can be, for example, 100°C, 50°C, 30°C, 0°C, -20°C, -50°C or lower, and its lower limit is not particularly limited, for example, -200°C or absolute zero.

[0032] In one embodiment, the low-temperature gas is injected from above the area to be cleaned to ensure that the low-temperature gas uniformly covers the area to be cleaned. Preferably, the gas is injected from 0.1 m to 1 m above the area to be cleaned, and more preferably from 0.5 m to 1 m above the area to be cleaned.

[0033] In one embodiment, the gas used for the low-temperature gas and the gas used for the high-temperature gas are the same or different kinds of inert gases, selected from one or more of nitrogen, helium, and argon; preferably nitrogen.

[0034] In one embodiment, in the cryogenic treatment step S3, the cryogenic gas is injected through an atomizing nozzle.

[0035] In one embodiment, the gas flow rate of the high-temperature gas and / or the low-temperature gas is not particularly limited and can be appropriately adjusted; for example, the gas flow rate of the high-temperature gas can be 5-200 m³ / h. 3 / h, 50-100 m 3 / h.

[0036] In one embodiment, the magnitude of the negative pressure used in the negative pressure suction step S4 is not particularly limited and can be a magnitude commonly used in the art, such as making the vacuum degree of the area to be cleaned from -0.08 MPa to -0.1 MPa.

[0037] There are no particular limitations on the filtration device used. In one embodiment, to better collect detached ash, the filtration device collects the ash, separately collecting ash particles larger than 100 mesh and smaller than 100 mesh. The calcium content in the ash affects its resource utilization, and traditional ash removal methods struggle to separate the Ca component. The inventors' method achieves ash removal where calcium salts are primarily found in ash particles smaller than 100 mesh, while the calcium content in ash particles larger than 100 mesh is lower, allowing for subsequent high-value utilization (such as in silica, water glass, and extraction of valuable elements). Therefore, this method enables the transfer of Ca to ash particles smaller than 100 mesh, facilitating the reuse of the collected ash.

[0038] It should be understood that negative pressure can be initiated at any stage of the method, such as before, during, or after any of the pretreatment, high-temperature treatment, and low-temperature treatment.

[0039] In one embodiment, during the safety protection step, the temperature in the area to be cleaned is monitored by a temperature sensor with a measurement accuracy of ±5°C.

[0040] In one embodiment, the area to be cleaned is the region of the air preheater equipped with heat storage elements.

[0041] In one embodiment, steps S1-S4 may be performed once or repeated multiple times during one cleaning cycle of the method. Preferably, the cleaning cycle is 1-2 hours.

[0042] In one embodiment, the method is performed using the aforementioned dust removal device.

[0043] This invention provides a dust removal technology. First, high-temperature gas is injected into the area to be cleaned, causing calcium salt ash such as calcium sulfate to completely melt and form a peeling gap with the component surface. Then, low-temperature gas is injected to rapidly cool the molten calcium salt. The stress generated by thermal expansion and contraction causes the calcium sulfate ash to become embrittled and detach from the component surface in the area to be cleaned, thus achieving the dust removal purpose. The device and technology of this invention can efficiently remove dust while avoiding mechanical damage to the equipment or components to be cleaned. Furthermore, the method of this invention can also be appropriately applied to the removal of ash such as silica, ammonium sulfate, and ammonium bisulfate.

[0044] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not imply that the scope of the invention is limited thereto.

[0045] Example To accomplish the following embodiments, a dust removal device was employed. Figure 1 To explain, it has the following characteristics: High-temperature gas generation section: includes a natural gas burner (thermal power 50-100kW) for heating nitrogen and a temperature control system for controlling the heating temperature, as well as a high-temperature resistant pipeline (made of corundum ceramic) for delivering the heated nitrogen to the area inside the air preheater equipped with heat storage elements; the flow rate of the high-temperature gas can be adjusted by a gas valve. Cryogenic gas generation unit: Equipped with a liquid nitrogen storage tank, connected by a pipeline and an atomizing nozzle. The nozzle is positioned approximately 0.5 to 1 m above the heat storage element to ensure uniform coverage of the cryogenic gas. Negative pressure dust collection unit: It consists of a vacuum pump and a filter collection device. The vacuum pump generates suction to attract ash to the filter device, and the filter device filters and collects the attracted ash. Safety Protection Unit: Equipped with a temperature sensor (measurement accuracy ±5℃) and a pressure sensor, it automatically cuts off the high-temperature gas supply and depressurizes the air preheater when the internal temperature exceeds 1600℃ or the pressure fluctuation is >0.05MPa to prevent the equipment from overheating and being damaged.

[0046] Test method description: Ash removal rate: The proportion of ash removed after ash removal treatment to the total ash in the heat storage elements of the air preheater. The total ash in the heat storage elements of the air preheater is calculated as the sum of the ash removed after ash removal treatment and the ash removed after the heat storage elements have been cleaned by ultrasonic treatment with 10wt% dilute sulfuric acid for 10 hours.

[0047] Calcium salt content in ash: The calcium salt content in ash (calculated as CaO) was analyzed using an XRF spectrometer.

[0048] Example 1 The heat storage elements of the air preheater are cleaned by following these steps: Pretreatment: After the air preheater is shut down, close the inlet and outlet valves and use the pressure sensor to confirm that the internal pressure of the air preheater is stable at atmospheric pressure.

[0049] High-temperature treatment: Continuously introduce 1500℃ high-temperature nitrogen into the air preheater and maintain the air preheater at a temperature above 1500℃ for about 300 seconds.

[0050] Cryogenic treatment: Inject nitrogen gas at 30°C to lower the temperature to below 150°C. The nozzle for injecting the cryogenic nitrogen gas is positioned 0.5 m above the heat storage element.

[0051] Negative pressure cleaning: After the temperature of the area of ​​the air preheater equipped with the heat storage element drops below 150°C, start the negative pressure dust collection to collect all the detached ash particles, and collect ash particles larger than 100 mesh and smaller than 100 mesh respectively.

[0052] When there is ash residue, repeat the "high temperature treatment - low temperature treatment" process and control the cleaning time of each air preheater to 1-2 hours per unit.

[0053] Example 2-11 Examples 2-11 were carried out in a similar manner to Example 1, with the same total dust removal time. The difference was that the relevant experimental parameters for Examples 2-11 were as shown in Table 1.

[0054] Comparative Example 1 The heat storage elements of the air preheater were cleaned by conventional airflow purging. The purging time was the same as the total purging time in Example 1. The temperature of the purging airflow was 200℃ and the purging speed was 80-90 m / s.

[0055] Comparative Example 2 Chemical cleaning was used to remove ash from the heat storage elements of the air preheater, which were soaked in 2wt% dilute sulfuric acid for 120 min.

[0056] Table 1. Experimental parameters and results for each embodiment and comparative example.

[0057] The ash removal method of this application has good ash removal efficiency, even reaching over 95%, and after ash removal, the heat exchange efficiency of the heat storage element recovers to over 95% of the design value. Furthermore, analysis of the "percentage of CaO in ash below 100 mesh" reveals a high calcium salt content in Examples 1-6 and 8, indicating that this method can transfer Ca elements to ash below 100 mesh, thus facilitating the recycling and reuse of ash larger than 100 mesh.

[0058] The method described in this application uses non-contact dust removal, which avoids mechanical damage and thus extends the service life of the equipment.

Claims

1. A dust removal device, characterized in that, The dust removal device includes: The high-temperature gas generating unit includes a heating unit for heating an inert gas to generate high-temperature gas, a temperature control unit for controlling the heating temperature, and a high-temperature gas conveying unit for conveying the high-temperature gas to the ash-cleaning area. The cryogenic gas generating unit includes a cryogenic gas supply unit for providing a cryogenic inert gas as cryogenic gas, and a cryogenic gas conveying unit for conveying the cryogenic gas to the ash-cleaning area. A negative pressure suction unit includes a negative pressure forming unit for generating negative pressure within the area to be cleaned, and a filtering unit, wherein the negative pressure attracts ash to the filtering unit for filtration and collection; and An optional safety protection unit includes a detection unit for detecting the pressure and / or temperature of the area to be cleaned, and a protection unit for cutting off the supply of high-temperature gas and / or depressurizing the area to be cleaned when the pressure and / or temperature exceeds a preset value.

2. The dust removal device according to claim 1, characterized in that, The inert gas types of the low-temperature gas and the high-temperature gas may be the same or different. The inert gas type of the low-temperature gas is selected from one or more of nitrogen, helium, and argon. The inert gas type of the high-temperature gas is selected from one or more of nitrogen, helium, and argon. And / or, the gas outlet of the cryogenic gas delivery unit is located 0.5 m to 1 m above the area to be cleaned; And / or, the cryogenic gas supply unit is a liquid nitrogen storage tank; And / or, the gas outlet of the cryogenic gas delivery unit has an atomizing nozzle; And / or, the heating unit is a burner; And / or, the filtration unit is a filtration device capable of collecting ash particles larger than 100 mesh and smaller than 100 mesh, respectively.

3. The dust removal device according to claim 1 or 2, characterized in that, The area to be cleaned is the region of the air preheater equipped with heat storage elements.

4. A method for cleaning dust, characterized in that, The dust removal method includes the following steps: S1. Pre-treatment: Close the inlet and outlet of the area to be cleaned, and confirm that the internal pressure of the area to be cleaned is stable at atmospheric pressure; S2. High-temperature treatment: Inject high-temperature gas into the area to be cleaned, so that the temperature of the area to be cleaned reaches 1500℃~1600℃; S3. Low temperature treatment: Inject low temperature gas into the area to be cleaned to reduce the temperature of the area from 1500℃~1600℃ to below 150℃; S4. Negative pressure dust collection: A negative pressure is generated in the area to be cleaned to attract ash, and the attracted ash is filtered and collected; S5. Optionally, it also includes a safety protection step: when the temperature in the area to be cleaned exceeds 1600°C and / or the pressure fluctuation is greater than 0.05 MPa, the supply of high-temperature gas is cut off and / or the pressure in the area to be cleaned is depressurized.

5. The dust removal method according to claim 4, characterized in that, In step S2, the area to be cleaned is kept at 1500℃~1600℃ for more than 10 seconds and less than 5 minutes, preferably 30 seconds~60 seconds; And / or, the temperature of the high-temperature gas is 1500℃~1600℃.

6. The dust removal method according to claim 4, characterized in that, In step S3, the temperature of the low-temperature gas is below 150°C; And / or, the low-temperature gas is injected from 0.5 m to 1 m above the area to be cleaned.

7. The dust removal method according to claim 4, characterized in that, In the high-temperature treatment step, the gas flow rate of the high-temperature gas is adjusted to be between 50-100 m³ / h. 3 Within the range of / h; And / or, adjust the gas flow rate of the cryogenic gas in the cryogenic treatment step.

8. The dust removal method according to claim 4, characterized in that, The gas used for the low-temperature gas and the gas used for the high-temperature gas are the same or different kinds of inert gases. The low-temperature gas is selected from one or more of nitrogen, helium, and argon. The inert gas used for the high-temperature gas is selected from one or more of nitrogen, helium, and argon. And / or, in the cryogenic treatment, the cryogenic gas is injected through an atomizing nozzle.

9. The dust removal method according to claim 4, characterized in that, In step S4, the vacuum level of the area to be cleaned is set to -0.08 MPa to -0.1 MPa; And / or, in step S4, a negative pressure is generated in the area to be cleaned before, during or after any of steps S1-S3 to attract ash. And / or, in step S4, after the filtration, the ash particles larger than 100 mesh and smaller than 100 mesh in the area to be cleaned are collected respectively; And / or, in the safety protection step, the temperature in the area to be cleaned is monitored by a temperature sensor with a measurement accuracy of ±5℃; And / or, the area to be cleaned is the area of ​​the air preheater equipped with heat storage elements.

10. The dust removal method according to any one of claims 4 to 9, characterized in that, In the method, steps S1-S4 are performed once or repeated multiple times. And / or, the dust removal method is carried out using the dust removal device according to any one of claims 1 to 3.

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