A method and device for quickly characterizing the fouling characteristics of coal ash

Abstract

The present invention discloses a method and device for rapidly characterizing the fouling characteristics of coal ash. The method of the present invention mainly involves feeding pulverized coal into an experimental device for combustion to generate ash particles and flue gas, which then flow through a porous filter plate, and the ash particles are intercepted by the filter plate; after removing the filter plate, the loose ash particles are removed, leaving the remaining ash particles as sticky ash; the value of the physical quantity index R = (G3 - G1) / (G2 - G1) is calculated through the initial mass G1 of the filter plate, the mass G2 after intercepting the ash particles, and the mass G3 after removing the loose ash particles, and the fouling characteristics are discriminated. The device of the present invention includes a gas distribution device, a powder feeder, a reaction tube, an electric heating furnace, a filter plate, an air extraction pump, etc. The filter plate is made of sintered metal powder and is located in the downstream section of the reaction tube. The present invention realizes the high-efficiency and reliable characterization of the fouling characteristics of coal fly ash, which is beneficial to timely warning the fouling characteristics of the fuel entering the boiler of a power station boiler and ensuring the safety of boiler operation.

Description

Technical Field

[0001] The present invention belongs to the technical field of pulverized coal boiler combustion, and specifically relates to a method and device for detecting slagging and contamination of coal, and more particularly to a method and device for rapidly characterizing coal ash contamination characteristics. Background Art

[0002] Many coal resources have strong slagging and fouling characteristics, which are detrimental to the safe and stable operation of coal-fired power plant boilers. Boiler slagging mainly refers to the slag layer formed when molten or melted ash contacts the heating surface, which generally occurs at the bottom of the furnace water-cooled walls and platen superheaters. Boiler fouling mainly refers to the fouling layer formed when solid ash particles deposit and adhere to the heating surface, which can occur on the heating surfaces of the furnace water-cooled walls, platen superheaters, high-temperature superheaters, high-temperature reheaters, and even low-temperature superheaters and reheaters. The fouling properties of a coal type can also, to a certain extent, explain its slagging properties, especially highly fouling coal types, which generally have strong slagging properties. At the same time, considering that the scope of pollution hazards is larger, more rapid, and more difficult to prevent and control, characterizing the fouling characteristics of coal types is a very important foundational work for preventing and controlling boiler slagging and fouling.

[0003] The contamination risk of coal depends primarily on the characteristics of the ash, particularly its composition. Generally speaking, the higher the relative content of alkali / alkaline earth metals in the ash, the higher the contamination risk. To ensure boiler safety, highly contaminating coals are often mixed with less contaminating coals (or materials). The mixing ratio directly impacts the power plant's power generation costs and equipment life. Therefore, appropriately determining the mixing ratio, while balancing slagging and contamination prevention with power generation costs, is crucial for power plant operations. However, the ash composition of coal fluctuates significantly, influenced by its complex sources and causes. Even in large open-pit mines where the calorific value, industrial analysis, and elemental analysis indicators are quite stable, the ash composition of coal can fluctuate significantly, resulting in frequent and significant changes in slagging and contamination characteristics, posing a significant risk to boilers. Therefore, monitoring and controlling the contamination characteristics of coal ash are essential.

[0004] However, at present, the vast majority of coal-fired power plants do not have tools for detecting the fouling characteristics of coal ash. Traditional ash fusion characteristic detection is not applicable to the characterization of coal ash fouling characteristics and is inefficient. A few power plants use the method of regularly detecting the ash composition of coal to master the fouling characteristics of coal. However, the efficiency of detecting the ash composition in coal is low (coal sample preparation → combustion to obtain ash sample → digestion or grinding and pressing into test sample → detection to obtain elemental spectrum → spectrum data screening and conversion into relative content data of ash composition). It often takes several days to complete the chemical analysis, and the process is complex, costly, and unreliable (key components such as Na are easily lost in large quantities during the ash sample preparation process), seriously lagging behind production. Due to the needs of basic research, there are currently means for characterizing the fouling characteristics of coal types, mainly the characterization of the sintering characteristics of coal ash (for example: Huang Dongdong, et al. Research progress on the sintering characteristics of high-sodium coal ash [J]. Clean Coal Technology, 2021). The main drawback of applying this technology to actual production is low efficiency. Especially in the sintering method, in order to prevent the escape of key elements, a large amount of low-temperature ash needs to be prepared, which takes a long time. In basic research, medium and large-scale combustion furnace test methods are also often used (for example: Xiaojiang Wu, et al. Ash deposition and slagging behavior of Chinese Xinjiang high-alkali coal in 3MWth pilot-scale combustion test). This technology has good effects in basic research, but due to the need to operate complex and large test systems, it is inefficient and costly, and thus cannot be applied to the daily production process of coal-fired power plants. Summary of the Invention

[0005] To solve the problems existing in the prior art, the present invention provides a method and device for rapidly characterizing the fouling characteristics of coal ash, realizing high-efficiency and reliable characterization of the fouling characteristics of coal types, and solving the problems of convenient inspection and timely regulation of the fouling characteristics of the fuel entering the furnace of a utility boiler.

[0006] The present invention provides a device for rapidly characterizing the fouling characteristics of coal ash to solve the above problems, which includes a gas distribution device, a coal feeder, a feed pipe, a reaction tube, a filter plate, a bracket, an exhaust pipe, and an exhaust pump connected in sequence; wherein the reaction tube is placed in an electric heating furnace, and a temperature controller, a power output cable, and a thermocouple are arranged on the electric heating furnace; the temperature controller is connected to the power output cable and the thermocouple, and the electric heating furnace realizes heating and temperature regulation of the reaction tube through the configured temperature controller, power output cable, and thermocouple; the filter plate, the bracket, the exhaust pipe, and the exhaust pump are connected in sequence, and the topmost filter plate is placed in the lower section of the reaction tube.

[0007] The gas distribution device includes a gas cylinder, a gas pressure reducing valve, and a gas flow controller arranged along the gas flow direction; the gas cylinder, the gas pressure reducing valve, and the gas flow controller are connected through gas pipelines; the feeding method of the coal feeder adopts piston propulsion, screw feeding, or disk cutting; the lower port diameter of the feeding pipe is 12 - 18 mm.

[0008] The inner diameter of the reaction tube is 30 - 60 mm and the length is 0.6 - 1.2 m; the electric heating furnace uses tungsten wire infrared radiation tubes or electric heating wires for heating, and the heated section length of the reaction tube is 0.4 - 1.0 m; the temperature sensing end of the thermocouple is closely attached to the outer wall of the reaction tube.

[0009] The electric heating furnace uses metal mirror reflection for heat preservation and is equipped with a medium flow channel for cooling the metal mirror; the visible light reflectivity of the metal mirror is greater than 0.85; the reaction tube is made of quartz or nickel-chromium alloy material, and the outer wall surface is subjected to frosted treatment or provided with an endothermic coating with an emissivity higher than 0.85; the working temperature of the reaction tube is 20 - 900 °C, and the temperature change rate is -300 - 300 °C / min.

[0010] The filter plate is made of sintered powder of nickel, chromium, or nickel-chromium alloy, with a thickness of 0.5 - 5.0 mm, a pore diameter less than 15 μm, and a porosity greater than 25%.

[0011] Based on the device of the present invention, the present invention provides a method for quickly characterizing the fouling characteristics of coal ash to solve the above problems. The method includes the following steps:

[0012] Using gas as the conveying medium, the pulverized coal is uniformly conveyed into the experimental device for combustion to generate ash particles and flue gas;

[0013] The ash particles and flue gas flow through the porous filter plate under the suction of the downstream air extraction pump, and the ash particles are intercepted;

[0014] Take out the filter plate, remove the loose ash particles on the ash particle interception surface of the filter plate, so that the remaining ash particles are adhesive ash;

[0015] Weigh the initial mass G1, the mass G2 after intercepting ash particles, and the mass G3 after removing loose ash particles of the filter plate in sequence;

[0016] Calculate the value of the physical quantity index R = (G3 - G1) / (G2 - G1) based on G1, G2, and G3;

[0017] Repeat the experimental process 2 - 5 times, take the arithmetic mean of the R values, and accordingly determine the fouling characteristics of the coal ash of the coal sample.

[0018] The particle size of the pulverized coal is in the range of 45 - 125 μm; the mass transport rate of the pulverized coal is 0.5 - 2.0 g / min; the volume content of oxygen in the transport medium is greater than 28%; the standard state volume flow rate of the transport medium is 2.0 - 10.0 L / min; the initial temperature of the combustion environment of the experimental device is set at 500 - 700 °C; the cumulative amount of pulverized coal transported in a single experiment of the experimental device is controlled within 2 - 10 g; after the pulverized coal transportation is completed, continue to purge for 2 - 3 min.

[0019] Control the cumulative amount of pulverized coal transported according to the ash amount in the transported coal reaching 0.2 - 0.5 g and the thickness of the deposited ash layer on the filter plate reaching 0.2 - 0.4 mm; control the volume flow rate of the transport medium according to 1.2 - 2.0 times the theoretical transport medium flow rate corresponding to the theoretical oxygen consumption for complete combustion of the pulverized coal; regulate the mass transport rate of the pulverized coal according to the average movement time of the pulverized coal particles with the air flow in the experimental device being 1.5 - 4.0 s.

[0020] The filter plate is made of sintered powder of nickel or nickel-chromium alloy, with a thickness of 0.5 - 5.0 mm, a pore diameter less than 15 μm, and a porosity greater than 25%; by vertically flipping the filter plate, the loose ash particles are detached from the filter plate by gravity sedimentation, or the loose ash particles are detached from the filter plate by air flow carrying through an air flow with a speed of 8 - 12 m / s and a duration of 2 - 5 s.

[0021] It is divided into six grades according to the degree of fouling: extremely strong III, extremely strong II, extremely strong I, high, medium, and low.

[0022] When R ≥ 50%, the fouling is determined to be extremely high III;

[0023] When 30% ≤ R < 50%, the fouling is determined to be extremely high II;

[0024] When 20% ≤ R < 30%, the fouling is determined to be extremely high I;

[0025] When 10% ≤ R < 20%, the fouling is determined to be high;

[0026] When 5% ≤ R < 10%, the fouling is determined to be medium;

[0027] - When R < 5%, the fouling is determined to be low.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] ① The operation steps of the present invention are simple and efficient. The small experimental device not only simulates the actual combustion environment and fouling conditions, but also enables this detection process to be implemented in a general coal inspection laboratory. Therefore, it has good feasibility for characterizing the fouling characteristics of coal types in the daily production of power plants.

[0030] ② The present invention adopts high-oxygen-concentration combustion, ensuring the rapid ignition, intense combustion, and efficient burnout of pulverized coal particles. Combined with the temperature boundary conditions, it can better simulate the actual fouling conditions of the heating surface and miniaturize the experimental device.

[0031] ③ The present invention uses a porous filter plate sintered with metal powder as the coal ash adhesion surface, which is conducive to the high-efficiency collection of coal ash and the acceleration of adhesion, greatly improving the test efficiency and facilitating the accurate weighing of the filter plate and coal ash in each stage.

[0032] ④ The data processing of the present invention is simple and fast, and can directly give the reliable fouling characteristic grade of coal ash.

[0033] ⑤ The present invention uses a small heating furnace and sets a boundary temperature not higher than 700°C, greatly improving the operation efficiency of the device; if metal mirror reflection insulation is adopted, the start-stop efficiency of the experimental device can be further greatly improved, and the detection time can be shortened.

[0034] ⑥ The gaseous alkali / alkali earth metals released by the coal powder combustion in the present invention will re-adhere to the surface of the ash particles in the lower section of the reaction tube, better reproducing the actual situation, avoiding the problem that the alkali metal escapes in a large proportion during the ash preparation process in the sintering method, and making the results more stable and reliable.

[0035] ⑦ By using the present invention, after receiving the original coal sample, through a simple process of sample preparation / preparation → combustion / adhesion → removal of loose ash / weighing → calculation of sintering data, reliable fouling characteristic data of the coal sample can be given within 0.7 - 2 hours, and the actual fouling phenomenon of the coal ash on the metal surface can be displayed, realizing the high-efficiency preview and prediction of the slagging and fouling risks of the coal entering the furnace. Brief Description of the Drawings

[0036] Figure 1 is a schematic diagram of a device for quickly characterizing the fouling characteristics of coal ash according to the present invention.

[0037] Figure 2 is a schematic diagram of the filter plate of the present invention and its installation position.

[0038] 1 - Gas distribution device; 2 - Coal feeder; 3 - Feed pipe; 4 - Reaction tube; 5 - Electric heating furnace; 6 - Filter plate; 7 - Exhaust pipe; 8 - Exhaust pump; 9 - Bracket; 10 - Temperature controller; 11 - Power output cable; 12 - Thermocouple. Detailed Embodiment

[0039] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0040] Reference Figure 1 and Figure 2 For the device for rapidly characterizing the fouling characteristics of coal ash according to the present invention, it includes a gas distribution device 1, a powder feeder 2, a feed pipe 3, a reaction tube 4, a filter plate 6, a bracket 9, an exhaust pipe 7, and an exhaust pump 8 that are connected in sequence; wherein the reaction tube 4 is placed in an electric heating furnace 5, and the electric heating furnace 5 realizes the temperature control of the reaction tube 4 through its configured temperature controller 10, power output cable 11, and thermocouple 12; the filter plate 6, the bracket 9, the exhaust pipe 7, and the exhaust pump 8 are connected in sequence, and the topmost filter plate 6 is placed in the lower section of the reaction tube 4. A bracket 9 is arranged below the filter plate 6, the filter plate 6 is embedded in the bracket, there is a gap between the bottom surface of the filter plate 6 and the bracket 9, a through hole is arranged at the center of the bracket 9, the exhaust pipe 7 communicates with the through hole, and the exhaust pump 8 is connected to the exhaust pipe 7.

[0041] The gas distribution device 1 includes a gas cylinder, a gas pressure reducing valve, a gas flow controller, and a gas pipeline; the feeding method of the powder feeder 2 adopts a piston propulsion type, a screw feeding type, or a disk cutting type; the lower port diameter of the feed pipe 3 is 12 - 18 mm.

[0042] The inner diameter of the reaction tube 4 is 30 - 60 mm and the length is 0.6 - 1.2 m; as a preferred embodiment, the inner diameter of the reaction tube 4 is 40 - 50 mm and the length is 0.8 - 1.0 m;

[0043] The electric heating furnace 5 is heated by tungsten wire infrared radiation tubes or electric heating wires, and the heated section length of the reaction tube 4 is 0.4 - 1.0 m; the temperature sensing end of the thermocouple 12 is closely attached to the outer wall of the reaction tube 4.

[0044] As a preferred embodiment, the electric heating furnace 5 adopts metal mirror reflection heat preservation and is configured with a medium flow channel for cooling the metal mirror; the visible light reflectivity of the metal mirror is greater than 0.85; the reaction tube 4 is made of quartz or nickel-chromium alloy material, and the outer wall surface is subjected to frosted treatment or coated with an endothermic coating with an emissivity higher than 0.85; the working temperature of the reaction tube 4 is 20 - 900 °C, and the temperature change rate is -300 - 300 °C / min.

[0045] As a preferred embodiment, the filter plate is made of sintered powder of nickel, chromium, or nickel-chromium alloy, with a thickness of 0.5 - 5.0 mm, a pore diameter less than 15 μm, and a porosity greater than 25%.

[0046] The method for quickly characterizing the fouling characteristics of coal ash according to the present invention is implemented according to the following steps:

[0047] 1) Sample preparation: Crush, reduce, quickly dry and grind the collected coal sample into a pulverized coal sample (with a mass of about 30 - 100 g). During the grinding process of the coal sample, a porous sieve is required to control the particle size of the final pulverized coal sample. As a reference, the particle size of the pulverized coal can be controlled in the range of 45 - 125 μm, and the mass-weighted average particle size is preferably controlled in the range of 75 - 90 μm;

[0048] 2) Preparation of experimental device: Place 3 - 20 g of the coal sample into the feeding system of the experimental device; Weigh the initial mass G1 of the dry and clean filter plate 6 and place it in the downstream section of the reaction tube; Heat the temperature of the reaction tube of the electric heating furnace to 500 - 700 °C (about 600 °C);

[0049] 3) Combustion: Use gas as the conveying medium to uniformly convey the pulverized coal into the experimental device for combustion to generate ash particles and flue gas;

[0050] 4) Ash deposition: The ash particles and flue gas flow through the porous filter plate 6 under the suction of the downstream air pump 8, and the ash particles are intercepted;

[0051] 5) Take out the filter plate and quickly cool it to 40 - 60 °C (slightly higher than the ambient temperature) on the surface of a normal-temperature metal plate, and weigh the mass G2 of the filter plate after intercepting the ash particles;

[0052] 6) Remove loose ash: Vertically flip the filter plate so that the loose ash particles fall off the filter plate by gravity sedimentation, or blow the loose ash particles off the filter plate by airflow with a speed of 8 - 12 m / s (about 10 m / s) and a duration of 2 - 5 s, or use a combination of the above two methods to remove the loose ash particles on the ash particle interception surface of the filter plate, so that the remaining ash particles are adhesive ash, and weigh the mass G3 after removing the loose ash particles; Calculate the value of R = (G3 - G1) / (G2 - G1);

[0053] 7) Repeat: Repeat steps 2 - 6 more than once to obtain 2 groups of R values. If the difference between the two groups of R values is less than 5%, take their average value as the final result; If the difference between the two groups of R values is ≥5%, then repeat steps 2 - 6 more than twice to obtain a total of 4 groups of R values. Exclude the maximum and minimum values, and take the average value of the middle two groups of R values as the final result. The repeated test can be flexibly decided according to the reliability of the process.

[0054] 8) End the experiment: Backflush and clean the filter plate; Turn off the power of the experimental device, take out the remaining coal sample, and tidy up the experimental device.

[0055] The operating parameters can be referred to the following methods: the mass conveying rate of pulverized coal is 0.5 - 2.0 g / min; the volume content of oxygen in the conveying medium is greater than 28% (e.g., 40%); the standard state volume flow rate of the conveying medium is 2.0 - 10.0 L / min (e.g., 5.0 L / min); the cumulative amount of pulverized coal conveyed in a single experiment of the experimental device is controlled within 2 - 10 g (e.g., 6 g); after the pulverized coal conveying is completed, continue to purge for 2 - 3 min. Among them, the cumulative amount of pulverized coal conveyed is controlled according to the ash amount in the conveyed coal reaching 0.2 - 0.5 g and the thickness of the ash layer deposited on the filter plate reaching 0.2 - 0.4 mm; the volume flow rate of the conveying medium is controlled according to 1.2 - 2.0 times of the theoretical conveying medium flow rate corresponding to the theoretical oxygen consumption for complete combustion of pulverized coal; the mass conveying rate of pulverized coal is regulated according to the average movement time of pulverized coal particles in the air flow in the experimental device being 1.5 - 4.0 s.

[0056] As a preferred embodiment, the filter plate is made of sintered powder of nickel or nickel-chromium alloy, with a thickness of 0.5 - 5.0 mm, a pore diameter less than 15 μm (e.g., 5 μm), and a porosity greater than 25% (e.g., 40%); by vertically flipping the filter plate, the loose ash particles are separated from the filter plate by gravitational settlement, or the loose ash particles are separated from the filter plate by being carried by an air flow with a speed of 8 - 12 m / s and a duration of 2 - 5 s.

[0057] Among them, it is divided into six grades according to the degree of soiling: extremely strong III, extremely strong II, extremely strong I, high, medium, and low:

[0058] - When R ≥ 50%, the soiling is judged as extremely high III;

[0059] - When 30% ≤ R < 50%, the soiling is judged as extremely high II;

[0060] - When 20% ≤ R < 30%, the soiling is judged as extremely high I;

[0061] - When 10% ≤ R < 20%, the soiling is judged as high;

[0062] - When 5% ≤ R < 10%, the soiling is judged as medium;

[0063] - When R < 5%, the soiling is judged as low.

[0064] The operating parameters in the above method steps are flexibly applied and implemented according to actual needs within the above ranges.

[0065] The present invention is generally applied in coal inspection laboratories, used for efficiently and reliably characterizing the coal soiling of coal-fired power plants burning high-alkali coal or slagging and soiling coal types, realizing timely early warning of the soiling characteristics of the fuel entering the furnace, and improving the safety of boiler operation.

Claims

1. An apparatus for rapidly characterizing the fouling characteristics of coal ash, characterized in that: It includes a gas distribution device (1), a coal feeder (2), a feed pipe (3), a reaction tube (4), a filter plate (6), a bracket (9), an extraction pipe (7) and an extraction pump (8) connected in sequence; wherein the reaction tube (4) is placed in an electric heating furnace (5), and a temperature controller (10), a power output cable (11) and a thermocouple (12) are arranged on the electric heating furnace (5); the temperature controller (10) is connected to the power output cable (11) and the thermocouple (12), and the electric heating furnace (5) realizes the heating and temperature control of the reaction tube (4) through the configured temperature controller (10), power output cable (11) and thermocouple (12); the filter plate (6), the bracket (9), the extraction pipe (7) and the extraction pump (8) are connected in sequence, and the topmost filter plate (6) is placed in the lower section of the reaction tube (4); the filter plate is made of sintered powder of nickel, chromium or nickel-chromium alloy, with a thickness of 0.5 - 5.0 mm, a pore diameter less than 15 μm, and a porosity greater than 25%; the electric heating furnace (5) adopts metal mirror reflection heat preservation and is configured with a medium flow channel for cooling the metal mirror; the visible light reflectivity of the metal mirror is greater than 0.85; the reaction tube (4) is made of quartz or nickel-chromium alloy material, and the outer wall surface is subjected to frosted treatment or provided with an endothermic coating with an emissivity higher than 0.85; the working temperature of the reaction tube (4) is 20 - 900 °C, and the temperature change rate is -300 - 300 °C / min.

2. The device for rapidly characterizing the fouling characteristics of coal ash according to claim 1, wherein: The gas distribution device (1) includes a gas cylinder, a gas pressure reducer and a gas flow controller arranged along the gas flow direction; the gas cylinder, the gas pressure reducer and the gas flow controller are connected through a gas pipeline; the feeding mode of the coal feeder (2) adopts piston propulsion, screw feeding or disk cutting; the lower port diameter of the feed pipe (3) is 12 - 18 mm.

3. The device for rapidly characterizing the fouling characteristics of coal ash according to claim 1, wherein: The inner diameter of the reaction tube (4) is 30 - 60 mm and the length is 0.6 - 1.2 m; the electric heating furnace (5) adopts tungsten wire infrared radiation tubes or electric heating wires for heating, and the heated section length of the reaction tube (4) is 0.4 - 1.0 m; the temperature sensing end of the thermocouple (12) is closely attached to the outer wall of the reaction tube (4).

4. A method for rapidly characterizing the fouling characteristics of coal ash based on the device according to any one of claims 1-3, characterized in that, The method includes the following steps: Using gas as the conveying medium, uniformly conveying pulverized coal into the experimental device for combustion to generate ash particles and flue gas; The ash particles and flue gas flow through the porous filter plate (6) under the suction of the downstream extraction pump (8), and the ash particles are intercepted; Taking out the filter plate, removing the loose ash particles on the ash particle interception surface of the filter plate, so that the remaining ash particles are agglomerated ash; Weighing the initial mass G1, the mass G2 after intercepting ash particles, and the mass G3 after removing loose ash particles of the filter plate in sequence; Calculating the value of the physical quantity index R = (G3 - G1) / (G2 - G1) based on G1, G2, and G3; Repeating the experimental process 2 - 5 times, taking the arithmetic mean of the R values, and accordingly determining the fouling characteristics of the coal ash of the coal sample; The particle size of the pulverized coal is in the range of 45 - 125 μm; the mass flow rate of the pulverized coal is 0.5 - 2.0 g / min; the volume content of oxygen in the conveying medium is greater than 28%; the standard state volume flow rate of the conveying medium is 2.0 - 10.0 L / min; the initial temperature of the combustion environment of the experimental device is set at 500 - 700 °C; the cumulative amount of pulverized coal conveyed in a single experiment of the experimental device is controlled within 2 - 10 g; after the pulverized coal conveying is completed, continue to purge for 2 - 3 min; it is divided into six levels according to the degree of fouling: extremely strong III, extremely strong II, extremely strong I, high, medium, and low: - When R ≥ 50%, the fouling is judged as extremely high III; - When 30% ≤ R < 50%, the fouling is judged as extremely high II; - When 20% ≤ R < 30%, the fouling is judged as extremely high I; - When 10% ≤ R < 20%, the fouling is judged as high; - When 5% ≤ R < 10%, the fouling is judged as medium; - When R < 5%, the fouling is judged as low; The cumulative amount of pulverized coal conveyed is controlled according to the ash amount in the conveyed coal reaching 0.2 - 0.5 g and the thickness of the ash layer deposited on the filter plate reaching 0.2 - 0.4 mm; the volume flow rate of the conveying medium is controlled according to 1.2 - 2.0 times the theoretical flow rate of the conveying medium corresponding to the theoretical oxygen consumption for complete combustion of the pulverized coal; the mass flow rate of the pulverized coal is regulated according to the average movement time of the pulverized coal particles in the air flow in the experimental device being 1.5 - 4.0 s; By vertically flipping the filter plate, the loose ash particles are separated from the filter plate by gravity settlement, or the loose ash particles are separated from the filter plate by being carried by an air flow with a speed of 8 - 12 m / s and a duration of 2 - 5 s.

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