A device and method for quickly assessing the pollution risk of coal combustion

Abstract

The present invention discloses an apparatus and method for rapidly assessing the contamination risk of coal combustion, wherein the apparatus comprises a combustion ash-making system, a coal ash burning system, and a weighing balance, wherein the combustion ash-making system comprises a gas distribution device, a coal powder feeder, a reaction tube, a coal ash collector, and an exhaust pump connected in sequence; the gas distribution device is provided with a gas flow meter for regulating gas flow and component ratio; the reaction tube is placed in a heating furnace, and its temperature is adjusted and controlled by a temperature controller of the heating furnace; a filter element for intercepting coal ash particles in the flue gas is provided in the coal ash collector; the invention utilizes high-temperature oxygen-rich intense combustion of coal powder under carrying flow conditions to simulate a real combustion environment to produce coal ash with low alkali / alkaline earth metal escape, and then organizes the coal ash to be heated and burned again in a crucible, and determines the contamination property of the coal by the mass loss of the ash sample and the sintering characteristics, thereby achieving a highly efficient assessment of the contamination risk of coal combustion, which is beneficial to better prevent and control boiler slagging contamination and promote the safe and high-proportion burning of high-alkali coal with better economy.

Description

Technical Field

[0001] The present invention belongs to the technical field of pulverized coal boiler combustion, and mainly relates to the detection and evaluation of the safety of coal types burned in boilers, and specifically relates to a device and method for quickly evaluating the contamination risk of coal. Background Art

[0002] High-alkali coal, with its abundant reserves, is widely used as a fuel for power plant boilers. However, the high relative concentration of alkali and alkaline earth metals in high-alkali coal ash makes them easily vaporized during high-temperature combustion. These metals then condense and adhere to heated surfaces and ash particles, forming a fouling layer. High levels of sodium and its compounds are particularly important in the formation of this fouling layer, which significantly compromises boiler safety and power generation economics. Effectively preventing and controlling boiler fouling is a prerequisite for the safe use of high-alkali coal.

[0003] A prerequisite for preventing and controlling contamination is understanding and predicting the contamination properties of incoming coal to power plants and furnaces, enabling the implementation of precise and reliable countermeasures. However, the alkali and alkaline earth metals in high-alkali coal ash fluctuate significantly with geographic coordinates and coal seam thickness, leading to sudden changes in the contamination properties of the coal entering power plant boilers. This can easily lead to severe contamination in a short period of time, drastically increasing safety risks and potentially causing accidents. The rapidly changing coal market, coupled with the blending of high-alkali coal with other coal types in varying proportions and rapid changes in coal composition, leads to increasing variability in the contamination properties of incoming coal. This necessitates efficient and frequent testing of the contamination properties of incoming coal. However, current methods for assessing coal contamination, such as ash composition testing and ash sintering characteristics, are either extremely inefficient due to slow sample preparation and testing processes, or the volatilization and escape of alkali and alkaline earth metals during the high-temperature, rapid ash preparation process, resulting in unreliable contamination assessment results. In short, current methods struggle to efficiently and reliably measure the contamination properties of incoming coal, failing to meet the practical needs of production and research. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention provides an apparatus and method for quickly assessing the contamination risk of coal combustion. Reliable coal ash is produced by simulating a real combustion process. The properties of alkali / alkaline earth metals, which are volatile at high temperatures, easily condense and adhere when cooled, and easily volatilize again when heated, are utilized to detect the volatile alkali / alkaline earth metal content and the sintering properties of the coal ash, thereby achieving a highly efficient assessment of the contamination risk of coal combustion.

[0005] In order to solve the above problems, the present invention provides a device for quickly assessing the risk of coal pollution. The device comprises a combustion ash-making system, a coal ash burning system and a weighing balance. The combustion ash-making system comprises a gas distribution device, a coal powder feeder, a reaction tube, a coal ash collector and an air pump connected in sequence. The gas distribution device is provided with a gas flow meter for regulating gas flow and component ratio. The reaction tube is placed in a heating furnace, and a temperature controller is provided in the heating furnace to control the temperature of the reaction tube. The coal ash collector is provided with a filter element for intercepting coal ash particles in the flue gas. The coal ash burning system comprises a high-temperature heating device and a crucible. The high-temperature heating device is used to heat the crucible. A crucible temperature regulator and a thermocouple are provided in the high-temperature heating device. The working temperature of the crucible when burning coal ash is 900-1100°C.

[0006] The resolution of the weighing balance is 0.1 mg or 1 mg; the gas flow meter is a gas mass flow controller; the filter element is made of metal wire or sintered metal powder; the pore diameter of the filter element is 3 to 10 μm; the crucible is made of quartz glass or nickel-chromium alloy.

[0007] The reaction tube is made of quartz glass or nickel-chromium alloy, and the outer wall of the reaction tube is frosted or plated with a heat-absorbing coating with an emissivity higher than 0.90; the inner diameter of the reaction tube is 35-50 mm, and the length of the heated section is 350-950 mm.

[0008] The electric heating furnace uses a tungsten filament infrared radiation tube for heating; the temperature sensing end of the thermocouple is in close contact with the outer wall of the reaction tube; the heating furnace uses a metal mirror reflection on the inner wall for insulation, and a medium flow channel is configured on the outer side of the metal mirror to cool the metal mirror; the visible light reflectivity of the metal mirror is greater than 0.85; the operating temperature range of the reaction tube is 5 to 1000°C, and the temperature change rate of the heating furnace is -300 to 300°C / min.

[0009] The invention also includes independently usable auxiliary equipment, which includes a flue gas oxygen analyzer and a vibrating sieve separator for characterizing particle size distribution; the air inlet of the flue gas oxygen analyzer is connected to the exhaust port of the air pump; the vibrating sieve separator is equipped with at least a square hole sieve with a sieve aperture of 90 μm; the sieve residue mass fraction R used to detect the powder particle size is 100 μm. 90 .

[0010] To solve the above problem, the present invention provides a method for quickly assessing the contamination risk of coal combustion, based on the device of the present invention, including the following process:

[0011] Step 1: Burning the coal ash sample: Using oxygen-containing gas as the conveying medium, the pulverized coal sample is uniformly conveyed into the experimental device for airflow-carried combustion, generating ash particles and flue gas. The ash particles and flue gas are then drawn through a filter element at a temperature of 120-200°C by a downstream suction pump, where the ash particles are retained. When the estimated ash particle volume exceeds 3g, the ash sample is removed from the filter element. The ash sample is sieved and ground in a dry environment to prepare a ready-to-use ash sample with a particle size of less than 90μm.

[0012] Step 2: Ash sample burning preparation: weigh and record the empty weight of the crucible in a dry state m1, put 0.8-1.5g of ash sample into the crucible, spread the ash sample evenly, compact the ash layer, weigh and record the total mass of the crucible and ash sample m2; put the crucible into a high-temperature heating device and prepare the conditions for high-temperature burning;

[0013] Step 3: Ash sample burning: Use the coal ash burning system to raise the temperature of the crucible to 900-1100°C at a heating rate of 200-500°C / min. After stabilization, keep the temperature for 12-30 minutes. Then remove the crucible and quickly cool it to room temperature under dry conditions.

[0014] Step 4: Ash sample mass loss rate measurement: Weigh and record the total mass of the crucible and residual ash after burning (m3); calculate the loss rate (L) = (m2-m3) / (m2-m1).

[0015] Step 5: Assess the risk of contamination of the heating surface during the combustion of the pulverized coal sample based on the loss on ignition rate L. The larger the value of L, the higher the risk of contamination when the boiler burns the pulverized coal sample.

[0016] The particle size of the pulverized coal sample is in the range of 45 to 125 μm; the mass transport rate of the pulverized coal is 1.5 to 3.0 g / min; the volume content of oxygen in the transport medium is greater than 35%; the standard state volume flow rate of the transport medium is 3.0 to 12.0 L / min, and the oxygen content of the flue gas is 5.0 to 7.0%; the initial temperature of the pulverized coal combustion in the experimental device is set to 700 to 1000°C.

[0017] The crucible burning temperature is set at 1000°C. The coal contamination risk is divided into six levels from low to high: Level 1, Level 2, Level 3, Level 4, Level 5, and Level 6, and is determined as follows:

[0018] -When L<0.3%, the contamination risk is determined to be Level 1;

[0019] - When 0.3%≤L<0.8%, the contamination risk is determined to be Level 2;

[0020] - When 0.8%≤L<2.0%, the contamination risk is determined to be Level 3;

[0021] - When 2.0%≤L<3.5%, the contamination risk is determined to be Level 4;

[0022] -When 3.5%≤L<5.0%, the contamination risk is determined to be Level 5;

[0023] -When L ≥ 5.0%, the contamination risk is determined to be Level 6.

[0024] After the completion of step 5, proceed to step 6, which is to use the particle size screening method to detect the sieve residue fraction R in the crucible. 90 ; Repeat steps 2 to 6 to obtain multiple sets of valid L, R 90 The numerical results show that the larger the values ​​are, the higher the risk of contamination of the boiler when burning the coal powder sample.

[0025] The pollution risk of coal combustion is divided into six levels from low to high: low, medium, high, very high I, very high II, and very high III. The pollution risk level is determined by using the corresponding criteria based on the crucible temperature value. The specific criteria are as follows:

[0026] 1) If the crucible temperature is 900℃, determine as follows:

[0027] -When R 90 <3%, the contamination risk is judged to be low;

[0028] -When 3%≤R 90 <8%, the contamination risk is judged as medium;

[0029] -When 8%≤R 90 <15%, the contamination risk is judged as high;

[0030] -When 15%≤R 90 <25%, the contamination risk is judged as very high I;

[0031] -When 25%≤R 90 <35%, the contamination risk is judged as very high II;

[0032] -When R 90 ≥35%, the contamination risk is judged as very high III;

[0033] 2) If the crucible temperature is 950°C, determine as follows:

[0034] -When R 90 <6%, the contamination risk is judged to be low;

[0035] -When 6%≤R 90 <12%, the contamination risk is judged as medium;

[0036] -When 12%≤R 90 <20%, the contamination risk is judged as high;

[0037] -When 20%≤R 90 <30%, the contamination risk is judged as very high I;

[0038] -When 30%≤R 90 <40%, the contamination risk is judged as very high II;

[0039] -When R 90 ≥40%, the contamination risk is judged as very high Ⅲ

[0040] 3) If the crucible temperature is 1000℃, determine as follows:

[0041] -When R 90 <10%, the contamination risk is judged to be low;

[0042] -When 10%≤R 90 <20%, the contamination risk is judged as medium;

[0043] -When 20%≤R 90 <30%, the contamination risk is judged as high;

[0044] -When 30%≤R 90 <40%, the contamination risk is judged as very high I;

[0045] -When 40%≤R 90 <50%, the contamination risk is judged as very high II;

[0046] -When R 90 ≥50%, the contamination risk is judged as very high III;

[0047] 4) If the crucible temperature is 1050°C, determine as follows:

[0048] -When R 90 <20%, the contamination risk is judged to be low;

[0049] -When 20%≤R 90 <30%, the contamination risk is judged as medium;

[0050] -When 30%≤R 90 <45%, the contamination risk is judged as high;

[0051] -When 45%≤R 90 <60%, the contamination risk is judged as very high I;

[0052] -When 60%≤R 90 <75%, the contamination risk is judged as very high II;

[0053] -When R 90 ≥75%, the contamination risk is judged as very high III;

[0054] 5) If the temperature of the crucible (13) is 1100°C, determine as follows:

[0055] -When R 90 <30%, the contamination risk is judged to be low;

[0056] -When 30%≤R 90 <40%, the contamination risk is judged as medium;

[0057] -When 40%≤R 90 <55%, the contamination risk is judged as high;

[0058] -When 55%≤R 90 <70%, the contamination risk is judged as very high I;

[0059] -When 70%≤R 90 <85%, the contamination risk is judged as very high II;

[0060] -When R 90 ≥85%, the contamination risk is judged as very high III.

[0061] Compared with the prior art, the present invention has at least the following beneficial effects:

[0062] The equipment described in the present invention can provide a method for simulating a real combustion environment by using high-temperature combustion of coal powder under carrying flow conditions. After the ash particles and flue gas reach the low-temperature section of the experimental device, the alkali / alkaline earth metal-containing substances that volatilize in the high temperature will re-adhere to the coal ash, which can effectively avoid the escape loss of alkali / alkaline earth metals in the ash making process, making the ash sample close to the real boiler fly ash; on this basis, the coal ash is reheated in the crucible, so that the alkali / alkaline earth metal substances in the ash sample will be volatilized and lost again, thereby forming a weight loss, and the coal ash in the crucible will undergo sintering behavior, which is helpful to characterize the sintering characteristics.

[0063] The present invention proposes a new method for characterizing the contamination of coal. This method uses high-temperature combustion of pulverized coal under entrained flow conditions to simulate a real combustion environment. This allows the ash particles and flue gas to reach the low-temperature section of the experimental device, and the alkali / alkaline earth metal-containing substances that volatilize in the high temperature re-adhere to the coal ash. This effectively avoids the escape and loss of alkali / alkaline earth metals during the ash-making process, making the ash sample closer to real boiler fly ash. Furthermore, the coal ash is reheated in a crucible, causing the alkali / alkaline earth metal substances in the ash sample to volatilize and lose again, resulting in weight loss. Furthermore, the coal ash in the crucible undergoes sintering behavior, which helps characterize the sintering characteristics. The present invention detects the weight loss and sintering characteristics of coal ash, accurately characterizing the contamination of coal ash. This method is completely different from existing methods and processes.

[0064] The present invention is simple to operate, does not involve hazardous chemical reagents, and can provide test data and coal contamination risk assessment results within 2 hours. It is highly consistent with the actual needs of coal-fired power plants in the northwest and southwest that burn a large amount of high-alkali coal. The equipment and method are easy to master and promote.

[0065] Furthermore, the present invention can adopt high oxygen concentration combustion to achieve rapid ignition and complete combustion of coal powder, so that sufficient coal ash that reliably simulates real combustion conditions can be quickly produced on micro and small experimental devices. This is the basis for efficient and reliable characterization of coal ash properties and is superior to existing methods.

[0066] Furthermore, the present invention adopts an infrared radiation heating method based on mirror insulation to ensure high efficiency of the experiment. The extreme heating and cooling rate in the range of 100 to 1000°C can reach -500 to 500°C / min, which greatly (90%) saves heating preparation and cooling waiting time and improves detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a schematic diagram of an implementable experimental device for pulverized coal combustion and ash production according to the present invention.

[0068] Figure 2 It is a schematic diagram of an implementable coal ash high-temperature combustion experimental device of the present invention.

[0069] 1-gas distribution device; 2-coal powder feeder; 3-reaction tube; 4-heating furnace; 5-coal ash collector; 6-vacuum pump; 7-filter element; 8-temperature controller; 9-high-temperature heating device; 10-heating chamber; 11-crucible temperature regulator; 12-thermocouple; 13-crucible. DETAILED DESCRIPTION

[0070] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0071] Implementation method one:

[0072] Combine Figure 1 and Figure 2To illustrate this embodiment, a device for quickly assessing the risk of coal contamination includes a combustion ash-making system, a coal ash burning system, and a weighing balance; wherein the combustion ash-making system includes a gas distribution device 1, a coal powder feeder 2, a reaction tube 3, a coal ash collector 5, and an air pump 6 connected in sequence; the gas distribution device 1 is provided with a gas flow meter for regulating gas flow and component ratio; the reaction tube 3 is placed in a heating furnace 4, and its temperature is adjusted and controlled by a temperature controller 8 of the heating furnace 4; the coal ash collector 5 has a filter element 7 for intercepting coal ash particles in the flue gas; the inner diameter of the reaction tube 3 is 35 to 50 mm, and the length of the heated section is 350 to 950 mm; the coal ash burning system includes a high-temperature heating device 9, a crucible 13, a thermocouple 12, and a crucible temperature regulator 11, and the working temperature of the crucible 13 when burning coal ash is 900 to 1100°C.

[0073] The resolution of the weighing balance is 0.1 mg or 1 mg; the gas flow meter is a gas mass flow controller; the reaction tube 3 is made of quartz glass or nickel-chromium alloy, and the outer wall is frosted or coated with a heat-absorbing coating with an emissivity higher than 0.90; the pore diameter of the filter element 7 is 3 to 10 μm; the crucible 13 is made of quartz glass or nickel-chromium alloy.

[0074] The electric heating furnace 5 is heated by a tungsten filament infrared radiation tube; the temperature sensing end of the thermocouple 12 is in close contact with the outer wall of the reaction tube 4.

[0075] The heating furnace 4 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 temperature change range of the reaction tube 3 is 5 to 1000°C, and the temperature change rate is -300 to 300°C / min.

[0076] The equipment also includes a vibration sieving device for characterizing particle size distribution and a flue gas oxygen analyzer. The vibration sieving device is equipped with at least a square-hole sieve with a sieve aperture of 90 μm. The air inlet of the flue gas oxygen analyzer is connected to the exhaust port of the vacuum pump 6.

[0077] By analyzing the characteristics and defects of various existing analytical methods and combining them with the actual conditions of coal-fired power plants, the present invention proposes for the first time a technical goal of efficiently and quickly characterizing the contamination properties of coal types, and proposes an equipment configuration that is completely different from existing methods. The above equipment configuration can achieve efficient and reliable ash production and precise burning, and can ensure the reliable and efficient implementation of experimental detection.

[0078] Implementation method 2:

[0079] Combine Figure 1 and Figure 2To illustrate this embodiment, the inner diameter of the reaction tube 3 is 45 mm, and the length of the heated section is 600 mm; the operating temperature of the crucible 13 when burning coal ash is 1000°C; the resolution of the weighing balance is 0.1 mg; the material of the reaction tube 3 is nickel-chromium alloy, and the outer wall is frosted and coated with a 0.1 mm thick nano-silicon carbide infrared absorption coating to enhance heat exchange; the pore diameter of the filter element 7 is selected to be 7 μm; the material of the crucible 13 is nickel-chromium alloy. Other embodiments are the same as the specific embodiment one. This embodiment coordinates and optimizes the size of each device, which is conducive to the miniaturization of the equipment; the 0.1 mm thick nano-silicon carbide infrared absorption coating can greatly enhance the temperature control response characteristics of the reaction tube and realize high-efficiency operation of the device; the extensive use of heat-resistant nickel-chromium alloy can enhance the thermal shock resistance of the equipment and ensure the working life of rapid temperature rise and fall operations. The 7 μm pores can ensure the smooth flow of the air channel and can intercept most of the coal ash particles.

[0080] Implementation method three:

[0081] Based on the attached Figure 1 and Figure 2 A method for quickly assessing the contamination risk of coal combustion is implemented according to the following process:

[0082] Step 1: Burning a coal ash sample: Using oxygen-containing gas as the conveying medium, the pulverized coal sample is uniformly conveyed into the experimental apparatus for airflow-carried combustion, generating ash particles and flue gas. The ash particles and flue gas are then drawn through a filter element 7 at a temperature of 120-200°C by a downstream vacuum pump 6, where the ash particles are trapped. When the estimated amount of ash particles exceeds 3g, the ash sample is removed from the filter element 7. The ash sample is sieved and ground in a dry environment to prepare a ready-to-use ash sample with a particle size of less than 90μm.

[0083] Step 2: Ash sample calcination preparation: Weigh and record the empty weight m1 of the crucible 13 in a dry state, place 0.8-1.5g of ash sample into the crucible 13, spread the ash sample evenly, compact the ash layer with a flat round-headed tool, and weigh and record the total mass m2 of the crucible 13 and the ash sample; place the crucible 13 into the high-temperature heating device 9, and prepare the conditions for high-temperature calcination;

[0084] Step 3: Ash sample burning: Using the coal ash burning system, raise the temperature of the crucible 13 to 900-1100°C at a heating rate of 200-500°C / min, and keep it at this temperature for 15-30 minutes after stabilization; then remove the crucible 13 and quickly cool it to room temperature under dry conditions;

[0085] Step 4: Ash sample mass loss rate measurement: weigh and record the total mass m3 of the crucible 13 and the residual ash after burning; calculate the loss rate L = (m2-m3) / (m2-m1).

[0086] Step 5: Assess the risk of contamination of the heating surface during the combustion of the pulverized coal sample based on the loss on ignition rate L. The larger the value of L, the higher the risk of contamination when the boiler burns the pulverized coal sample.

[0087] The particle size of the pulverized coal sample is in the range of 45 to 125 μm; the mass transfer rate of the pulverized coal is 1.5 to 3.0 g / min; the volume content of oxygen in the conveying medium is greater than 35%; the standard volume flow rate of the conveying medium is adjusted in the range of 3.0 to 12.0 L / min, and the oxygen content of the flue gas is 5.0 to 7.0%; the initial combustion temperature of the pulverized coal in the experimental device is set to 700 to 1000°C. When the pulverized coal is lignite, the initial combustion temperature can be set to 750±30°C; when the pulverized coal is bituminous coal, the initial combustion temperature can be set to 850±30°C; when the pulverized coal is lean coal, the initial combustion temperature can be set to 900±30°C; when the pulverized coal is anthracite, the initial combustion temperature can be set to 950±30°C, and the volume content of oxygen in the conveying medium is greater than 60%.

[0088] In the first step, it should be ensured that the test is carried out in a dry environment and the prepared ash sample is in a sufficiently dry state.

[0089] The coal ash used in this method to characterize the contamination of coal is produced through intense combustion at high temperature and in an oxygen-rich environment, and the gasified alkali / alkaline earth metals eventually return to the ash particles, avoiding the volatilization loss of the alkali / alkaline earth metals. Therefore, the properties of the coal ash are very similar to those of an actual boiler, making it easy to characterize the amount of volatile alkali / alkaline earth metals by re-burning and weighing. Since volatile alkali / alkaline earth metals are the root cause of boiler contamination, this method is highly reliable in characterizing the contamination of coal ash. In addition, this method is easy to implement and operate, and is convenient for promotion and application in coal-fired power plants, meeting the high efficiency and reliability requirements of on-site applications, helping power plants to rationally mix coal and scientifically prevent and control contamination. In general, this method completely overcomes the inefficiency and unreliability of existing methods for characterizing coal / coal ash slagging contamination, and is a brand-new method.

[0090] Implementation method four:

[0091] When preparing the coal ash sample, the particle size of the coal powder sample is controlled below 125 μm, and the mass median particle size is controlled in the range of 60 to 75 μm; the coal powder mass delivery rate is set to about 2.0 g / min during sample preparation; the oxygen volume content in the conveying medium is controlled to about 40%; the standard state volume flow rate of the conveying medium is regulated according to the oxygen content of the flue gas in the exhaust gas, and the oxygen content of the flue gas is controlled to about 6.0%; the temperature of the filter element 7 is set to 150°C.

[0092] In the ash sample burning preparation stage, about 1.0g of coal ash sample is used. After flattening and compacting, the coal ash thickness is controlled at about 1.0mm. During the ash sample burning, a heating rate of 300℃ / min is used to increase the temperature to 1000℃; after stabilization, the temperature is kept for 20 minutes.

[0093] Other implementations are the same as the third specific implementation.

[0094] This embodiment provides optimal process operating parameters to achieve efficient and standardized operation of the system, which is convenient for implementation and comparison.

[0095] Implementation method five:

[0096] When evaluating the coal contamination risk, the crucible (13) burning temperature is set to 1000°C, and the coal contamination risk is divided into six levels from low to high: level 1, level 2, level 3, level 4, level 5, and level 6, and is determined in the following manner:

[0097] -When L<0.3%, the contamination risk is determined to be Level 1;

[0098] - When 0.3%≤L<0.8%, the contamination risk is determined to be Level 2;

[0099] - When 0.8%≤L<2.0%, the contamination risk is determined to be Level 3;

[0100] - When 2.0%≤L<3.5%, the contamination risk is determined to be Level 4;

[0101] -When 3.5%≤L<5.0%, the contamination risk is determined to be Level 5;

[0102] -When L ≥ 5.0%, the contamination risk is determined to be Level 6.

[0103] Other implementations are the same as the third or fourth specific implementation.

[0104] This implementation method provides clear contamination risk criteria, which can achieve standardized operation and facilitate implementation and comparison.

[0105] Implementation method six:

[0106] After the fifth step of the third embodiment is completed, the sixth step is carried out, that is, the sieve residue fraction R of the residual ash in the crucible 13 is detected by particle size screening method. 90 Repeat steps 1 to 6 to obtain multiple effective L and R values ​​for various types of coal. 90 The numerical results show that the larger the values ​​are, the higher the risk of contamination will occur when the boiler burns the coal powder sample. Combined with the reference coal types, the anti-contamination measures for the relevant coal types are decided.

[0107] Other implementations are the same as the third, fourth or fifth specific implementations.

[0108] By doing so, the sintering characteristics of coal ash can be obtained more conveniently and more comprehensively, and the contamination properties of coal types can be evaluated more reliably.

[0109] Implementation method seven:

[0110] Based on the sixth embodiment, when evaluating the coal-burning pollution risk, the coal-burning pollution risk is divided into six levels from low to high: low, medium, high, very high I, very high II, and very high III. The pollution risk level is determined by using the corresponding criteria according to the temperature value of the crucible (13). The specific criteria are as follows:

[0111] 1) If the temperature of the crucible (13) is 900°C, determine as follows:

[0112] -When R 90 <3%, the contamination risk is judged to be low;

[0113] -When 3%≤R 90 <8%, the contamination risk is judged as medium;

[0114] -When 8%≤R 90 <15%, the contamination risk is judged as high;

[0115] -When 15%≤R 90 <25%, the contamination risk is judged as very high I;

[0116] -When 25%≤R 90 <35%, the contamination risk is judged as very high II;

[0117] -When R 90 ≥35%, the contamination risk is judged as very high III;

[0118] 2) If the temperature of the crucible (13) is 950°C, determine as follows:

[0119] -When R 90 <6%, the contamination risk is judged to be low;

[0120] -When 6%≤R 90 <12%, the contamination risk is judged as medium;

[0121] -When 12%≤R 90 <20%, the contamination risk is judged as high;

[0122] -When 20%≤R 90 <30%, the contamination risk is judged as very high I;

[0123] -When 30%≤R 90 <40%, the contamination risk is judged as very high II;

[0124] -When R 90 ≥40%, the contamination risk is judged as very high Ⅲ

[0125] 3) If the temperature of the crucible (13) is 1000°C, determine as follows:

[0126] -When R 90 <10%, the contamination risk is judged to be low;

[0127] -When 10%≤R 90 <20%, the contamination risk is judged as medium;

[0128] -When 20%≤R 90 <30%, the contamination risk is judged as high;

[0129] -When 30%≤R 90 <40%, the contamination risk is judged as very high I;

[0130] -When 40%≤R 90 <50%, the contamination risk is judged as very high II;

[0131] -When R 90 ≥50%, the contamination risk is judged as very high III;

[0132] 4) If the temperature of the crucible (13) is 1050°C, determine as follows:

[0133] -When R 90 <20%, the contamination risk is judged to be low;

[0134] -When 20%≤R 90 <30%, the contamination risk is judged as medium;

[0135] -When 30%≤R 90 <45%, the contamination risk is judged as high;

[0136] -When 45%≤R 90 <60%, the contamination risk is judged as very high I;

[0137] -When 60%≤R 90 <75%, the contamination risk is judged as very high II;

[0138] -When R 90 ≥75%, the contamination risk is judged as very high III;

[0139] 5) If the temperature of the crucible (13) is 1100°C, determine as follows:

[0140] -When R 90 <30%, the contamination risk is judged to be low;

[0141] -When 30%≤R 90 <40%, the contamination risk is judged as medium;

[0142] -When 40%≤R 90 <55%, the contamination risk is judged as high;

[0143] -When 55%≤R 90 <70%, the contamination risk is judged as very high I;

[0144] -When 70%≤R 90 <85%, the contamination risk is judged as very high II;

[0145] -When R 90 ≥85%, the contamination risk is judged as very high III.

[0146] Other implementations are the same as the sixth specific implementation.

[0147] This implementation method provides clear contamination risk criteria, which can achieve standardized operation and facilitate implementation and comparison.

[0148] It can be seen from the above embodiments that the implementation of the present invention is relatively flexible and diverse. 90 Whether it is one of the numerical results, or a comprehensive judgment of the coal contamination by combining two to three indicators, or changing the operating temperature of the test process or the aperture of the coal powder screen, it can be easily realized and implemented under the method provided by the present invention. Therefore, it is a change within the normal range of the present invention and belongs to the technical protection scope of the present invention.

[0149] The present invention is generally used in coal testing laboratories of scientific research institutions and coal-fired power plants, and is particularly used to strengthen coal quality and coal property testing and promote safe and high-proportion burning of economically efficient high-alkali coal.

Claims

1. A device for rapidly assessing the contamination risk of coal combustion, characterized by: Including combustion ash making system, coal ash burning system and weighing balance; The combustion ash-making system comprises an air distribution device (1), a coal powder feeder (2), a reaction tube (3), a coal ash collector (5) and an air pump (6) connected in sequence; the air distribution device (1) is provided with a gas flow meter for regulating gas flow and component distribution ratio; the reaction tube (3) is placed in a heating furnace (4), and a temperature controller (8) is provided in the heating furnace (4) to control the temperature of the reaction tube (3); the coal ash collector (5) is provided with a filter element (7) for intercepting coal ash particles in the flue gas; the coal ash burning system comprises a high-temperature heating device (9) and a crucible (13), and the high-temperature heating device (9) is used to heat the crucible (13). A crucible temperature regulator (11) and a thermocouple (12) are provided in the high-temperature heating device, and the working temperature of the crucible (13) when burning the coal ash is 900-1100°C; the device also includes independently usable auxiliary equipment, which includes a flue gas oxygen analyzer and a vibration screening instrument for characterizing the particle size distribution; the air inlet of the flue gas oxygen analyzer is connected to the exhaust port of the vacuum pump (6); the vibration screening instrument is equipped with at least a square hole sieve with a sieve aperture of 90 μm; the filter element (7) is made of metal wire or sintered from metal powder; the pore diameter of the filter element (7) is 3-10 μm.

2. The device for rapidly assessing coal contamination risk according to claim 1, characterized in that: The resolution of the weighing balance is 0.1 mg or 1 mg; the gas flow meter is a gas mass flow controller; and the crucible (13) is made of quartz glass or nickel-chromium alloy.

3. The device for rapidly assessing coal contamination risk according to claim 1, characterized in that: The material of the reaction tube (3) is quartz glass or nickel-chromium alloy, and the outer wall surface of the reaction tube (3) is frosted or plated with a heat-absorbing coating with an emissivity higher than 0.90; the inner diameter of the reaction tube (3) is 35-50 mm, and the length of the heated section is 350-950 mm.

4. The device for rapidly assessing coal contamination risk according to claim 3 is characterized in that: The heating furnace (4) is heated by a tungsten filament infrared radiation tube; the temperature sensing end of the thermocouple (12) is in close contact with the outer wall of the reaction tube (3); the heating furnace (4) uses a metal mirror as an inner wall, and the heating furnace (4) 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 operating temperature range of the reaction tube (3) is 5~1000℃, and the temperature change rate of the heating furnace (4) is -300~300℃ / min.

5. A method for rapidly assessing the risk of coal pollution, characterized in that: The device according to any one of claims 1 to 4 comprises the following process: Step 1: Burning coal ash sample: Using oxygen-containing gas as the conveying medium, the coal powder sample is uniformly conveyed into the experimental device for airflow-carried combustion, generating ash particles and flue gas; the ash particles and flue gas are sucked by the downstream suction pump (6) in the medium flow direction and flow through the filter element (7) with a temperature of 120~200℃, and the ash particles are intercepted; after the estimated amount of ash particles is greater than 3g, the ash sample in the filter element (7) is taken out; The ash sample is sieved and ground in a dry environment to prepare an ash sample with a particle size of less than 90 μm. Step 2: Ash sample burning preparation: weigh and record the empty weight of the crucible (13) in a dry state m 1. Place 0.8-1.5g of ash sample into the crucible (13), spread the ash sample evenly, compact the ash layer, weigh and record the total mass of the crucible (13) and the ash sample. m 2. Place the crucible (13) into the high-temperature heating device (9) and prepare the conditions for high-temperature burning; Step 3: Ash sample burning: using a coal ash burning system, the temperature of the crucible (13) is raised to 900-1100°C at a heating rate of 200-500°C / min, and then kept at this temperature for 12-30 minutes after stabilization; then, the crucible (13) is taken out and rapidly cooled to room temperature under dry conditions; Step 4: Ash sample mass loss rate measurement: weigh and record the total mass of the crucible (13) and the residual ash after burning m 3. Calculate the loss on ignition rate L = (m2-m3) / (m2-m1); Step 5: Based on the loss on ignition rate L Assess the risk of contamination of the heating surface during combustion of the pulverized coal sample; L The larger the value, the higher the risk of contamination when the boiler burns the pulverized coal sample; The burning temperature of the crucible (13) is set to 1000°C. The coal contamination risk is divided into six levels from low to high: level 1, level 2, level 3, level 4, level 5, and level 6, and is determined in the following manner: -when L <0.3%, the contamination risk is determined to be level 1; -When 0.3%≤ L <0.8%, the contamination risk is determined to be level 2; -When 0.8%≤ L <2.0%, the contamination risk is determined to be level 3; -When 2.0%≤ L <3.5%, the contamination risk is determined to be level 4; -When 3.5%≤ L <5.0%, the contamination risk is determined to be level 5; -when L ≥5.0%, the contamination risk is determined to be level 6; After the completion of step 5, the sixth step is to detect the sieve residue fraction of the residual ash in the crucible (13) by using the particle size screening method. R 90 ; Repeat steps 2 to 6 to get multiple groups of valid L, R 90 Numerical results show that the larger the values ​​are, the higher the risk of contamination of the boiler when burning the pulverized coal sample. The pollution risk of coal combustion is divided into six levels from low to high: low, medium, high, very high I, very high II, and very high III. The pollution risk level is determined by using the corresponding criteria based on the temperature value of the crucible (13). The specific criteria are as follows: 1) If the temperature of the crucible (13) is 900°C, determine as follows: -when R 90 <3%, the contamination risk is judged to be low; -When 3%≤ R 90 <8%, the contamination risk is judged as medium; -When 8%≤ R 90 <15%, the contamination risk is judged as high; -When 15%≤ R 90 <25%, the contamination risk is judged as very high I; -When 25%≤ R 90 <35%, the contamination risk is judged as very high II; -when R 90 ≥35%, the contamination risk is judged as very high III; 2) If the temperature of the crucible (13) is 950°C, determine as follows: -when R 90 <6%, the contamination risk is judged to be low; -When 6%≤ R 90 <12%, the contamination risk is judged as medium; -When 12%≤ R 90 <20%, the contamination risk is judged as high; -When 20%≤ R 90 <30%, the contamination risk is judged as very high I; -When 30%≤ R 90 <40%, the contamination risk is judged as very high II; -when R 90 ≥40%, the contamination risk is judged as very high Ⅲ 3) If the temperature of the crucible (13) is 1000°C, determine as follows: -when R 90 <10%, the contamination risk is judged to be low; -When 10%≤ R 90 <20%, the contamination risk is judged as medium; -When 20%≤ R 90 <30%, the contamination risk is judged as high; -When 30%≤ R 90 <40%, the contamination risk is judged as very high I; -When 40%≤ R 90 <50%, the contamination risk is judged as very high II; -when R 90 ≥50%, the contamination risk is judged as very high III; 4) If the temperature of the crucible (13) is 1050°C, determine as follows: -when R 90 <20%, the contamination risk is judged to be low; -When 20%≤ R 90 <30%, the contamination risk is judged as medium; -When 30%≤ R 90 <45%, the contamination risk is judged as high; -When 45%≤ R 90 <60%, the contamination risk is judged as very high I; -When 60%≤ R 90 <75%, the contamination risk is judged as very high II; -when R 90 ≥75%, the contamination risk is judged as very high III; 5) If the temperature of the crucible (13) is 1100°C, determine as follows: -when R 90 <30%, the contamination risk is judged to be low; -When 30%≤ R 90 <40%, the contamination risk is judged as medium; -When 40%≤ R 90 <55%, the contamination risk is judged as high; -When 55%≤ R 90 <70%, the contamination risk is judged as very high I; -When 70%≤ R 90 <85%, the contamination risk is judged as very high II; -when R 90 ≥85%, the contamination risk is judged as very high III.

6. The method for rapidly assessing coal contamination risk according to claim 5, characterized in that: The particle size of the pulverized coal sample is in the range of 45~125μm; the mass conveying rate of the pulverized coal is 1.5~3.0g / min; the volume content of oxygen in the conveying medium is greater than 35%; the standard state volume flow rate of the conveying medium is 3.0~12.0L / min, and the oxygen content of the flue gas is 5.0~7.0%; the initial temperature of the pulverized coal combustion in the experimental device is set to 700~1000℃.

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