Device and method for predicting slagging characteristic of coal ash

Abstract

The invention discloses a device and a method for predicting coal ash slagging characteristics. The device comprises an electronic camera, a lens, a light source, a filter, quartz glass, a heating table upper cover, a sapphire sheet, an ash sample, a heating crucible, a heating table, a heating wire, a thermocouple, an air inlet pipe and an air outlet pipe. From the perspective of the coal ash particles, the device is adopted to explore the proportion of the molten particles at different temperatures, the coal ash slagging characteristic is predicted more accurately, and the anti-contamination design and operation of the boiler are accurately guided.

Description

Technical Field

[0001] The invention relates to the technical field of coal ash slagging analysis, and in particular to a device and method for predicting coal ash slagging characteristics. Background Art

[0002] In large-scale power station boilers, due to the high flue gas temperature in the furnace, the molten or partially molten fly ash particles collide with the heating surface, and continuously adhere to produce slagging, especially when burning high-alkali metal fuels. When designing the boiler, in order to alleviate the slagging condition of the heating surface and meet the boiler safety and economic indicators at the same time, the screen bottom flue gas temperature and the furnace outlet flue gas temperature should be reasonably selected. For power station pulverized coal boilers, if the screen bottom flue gas temperature and the furnace outlet flue gas temperature are too high, it will cause serious slagging of the screen superheater and serious ash accumulation on the horizontal flue heating surface, affecting the safe and stable operation of the boiler. If the screen bottom flue gas temperature and the furnace outlet flue gas temperature are designed too low, the area of ​​the heating surface will increase, resulting in an increase in boiler costs.

[0003] The selection principle of the flue gas temperature at the furnace outlet is clearly specified in the "DL / T 831-2015 Guidelines for the Selection of Furnaces of Large-Capacity Pulverized Coal-Fired Boilers". The design calculation flue gas temperature θ of the furnace outlet smoke window under BMCR conditions F "It is advisable to determine according to the deformation temperature of the fly ash, θ F "≤(DT-100)℃; but if the difference between the softening temperature and the deformation temperature of the coal ash (ST-DT) ≤50℃, then θ F "≤(ST-150)℃.

[0004] The coal ash deformation temperature is generally measured according to GB / T 219-2008 "Determination of coal ash fusibility". However, this method regards the coal ash as a whole with uniform distribution of components, but the actual distribution of coal ash components is not uniform, resulting in different melting states of coal ash particles with different components at the same temperature. Therefore, some boilers still have serious slagging and contamination problems on the screen superheater and horizontal flue heating surface during actual operation, which shows that selecting the furnace outlet flue gas temperature according to the coal ash deformation temperature cannot fundamentally alleviate the slagging of the boiler heating surface.

[0005] The slagging of boiler heating surface is closely related to the melting state of individual coal ash particles. When the molten coal ash particles hit the heating surface, they will adhere to form slagging, while the unmelted particles will not adhere to the heating surface. Therefore, starting from the melting state of coal ash particles, the slagging of boiler heating surface can be fundamentally alleviated. Summary of the invention

[0006] In order to solve the problem that the boiler heating surface still has serious slagging and contamination under the existing principle of selecting the flue gas temperature at the furnace outlet, the purpose of the present invention is to provide a device and method for predicting the slagging characteristics of coal ash.

[0007] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a device for predicting the slagging characteristics of coal ash, including an electronic camera 1, a lens 2, a light source 3, a filter 4, a quartz glass 5, a heating table cover 6, a sapphire sheet 7, an ash sample 8, a heating crucible 9, a heating table 10, a heating wire 11, a thermocouple 12, an air inlet pipe 13, and an air outlet pipe 14.

[0008] The filter 4 is connected to the lens 2 via threads.

[0009] The light source 3 is arranged around the lens 2 and illuminates the sapphire plate 7 through the quartz glass 5 .

[0010] The quartz glass 5 is embedded in the heating table cover 6 .

[0011] The upper cover 6 of the heating platform is connected to the heating platform 10 by bolts and can be disassembled for loading samples.

[0012] The heating crucible 9 is fixed at the center of the bottom of the heating platform 10 and cannot be moved.

[0013] The ash sample 8 is placed on the sapphire sheet 7 , and the sapphire sheet 7 with the ash sample 8 is placed at the center of the bottom of the heating crucible 9 .

[0014] The sapphire sheet 7 has a diameter of 5 mm and can be removed and replaced.

[0015] The heating wire 11 and the thermocouple 12 are wound under the heating crucible 9 .

[0016] A method for predicting coal ash slagging characteristics includes the following steps.

[0017] Step 1: Prepare the coal ash sample according to GB / T 212-2008 "Industrial Analysis Methods of Coal": Spread the coal sample smaller than 0.2 mm evenly in an ash dish so that it does not exceed 0.15 g per square centimeter, place the ash dish into the constant temperature zone of a muffle furnace with a furnace temperature not exceeding 100°C, close the furnace door and leave a 15 mm gap in the furnace door, slowly raise the furnace temperature to 500°C in no less than 30 minutes, and keep it at this temperature for 30 minutes, continue to raise the temperature to 815±10°C, and burn at this temperature for 1 hour.

[0018] Step 2: Apply rosin on the central area of ​​the sapphire sheet, adhere a small amount of prepared ash sample to the rosin, blow it thoroughly with an ear bulb, place the sapphire sheet with the ash sample in the center of the bottom of the heating crucible, turn on the electronic camera and the imaging display system connected to it, adjust the magnification and focal length to make more coal ash particles clearly appear in the imaging display system.

[0019] Step 3: Connect the heating platform and the upper cover of the heating platform, introduce the required atmosphere and open the cooling water circuit. Turn on the heating system, the heating rate is 30°C / min below 900°C, and the heating rate is 5°C / min above 900°C. During the heating process, the morphological changes of each coal ash particle are recorded every 20°C.

[0020] Step 4: Use image processing software to analyze the change in particle area at different temperatures. When the particle area reaches the minimum, record the temperature as the melting temperature of the particle, and obtain the melting temperatures of all particles in turn.

[0021] Step 5. To reduce experimental and analytical errors, the experiment was repeated three times, and the number of molten particles at different temperatures was counted to obtain a curve of the ratio of molten particles to the total number of particles as a function of temperature, which guided the selection of the boiler screen bottom flue gas temperature and the furnace outlet flue gas temperature.

[0022] Compared with the existing prediction methods of coal ash slagging characteristics, the present invention has the following advantages.

[0023] 1. The present invention provides a device and method for predicting the slagging characteristics of coal ash. By adopting the above device, the coal ash melting temperature of different particles in the coal ash can be measured. The operation is simple and there is no need to make a standard ash cone.

[0024] 2. The present invention provides a device and method for predicting the slagging characteristics of coal ash. By obtaining the ratio of coal ash molten particles at different temperatures, accurate guidance can be provided for the anti-fouling design and operation of boilers. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is an overall structural diagram of a device and method for predicting coal ash slagging characteristics.

[0026] Figure 2 This is a partially enlarged view of a device and method for predicting coal ash slagging characteristics according to the present invention. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "top", "bottom", "one side", "the other side", "front", "back", "middle part", "inside", "top end", "bottom end", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The present invention is further described in detail below with reference to the accompanying drawings.

[0030] like Figure 1 , Figure 2 As shown, the present invention provides a device for predicting the slagging characteristics of coal ash, including an electronic camera 1, a lens 2, a light source 3, a filter 4, a quartz glass 5, a heating table cover 6, a sapphire sheet 7, an ash sample 8, a heating crucible 9, a heating table 10, a heating wire 11, a thermocouple 12, an air inlet pipe 13, and an air outlet pipe 14.

[0031] The filter 4 is connected to the lens 2 via threads, and the filter 4 only allows light with a corresponding central wavelength to pass through.

[0032] The light source 3 is arranged around the lens 2 and irradiates the sapphire plate 7 through the quartz glass 5 . The wavelength of the light source 3 is consistent with the central wavelength of the filter 4 .

[0033] The quartz glass 5 is embedded in the heating table cover 6 .

[0034] The upper cover 6 on the heating platform is connected to the heating platform 10 by bolts and can be disassembled for loading samples. Cooling water is passed through the upper cover 6 on the heating platform and the heating platform 10 .

[0035] The heating crucible 9 is fixed at the center of the bottom of the heating platform 10 and cannot be moved. The material of the heating crucible is mainly Al2O3.

[0036] The ash sample 8 is placed on the sapphire sheet 7 , and the sapphire sheet 7 with the ash sample 8 is placed at the center of the bottom of the heating crucible 9 .

[0037] The sapphire sheet 7 has a diameter of 5 mm and can be removed and replaced.

[0038] The heating wire 11 and the thermocouple 12 are wound under the heating crucible 9 .

[0039] A method for predicting coal ash slagging characteristics includes the following steps.

[0040] Step 1: Prepare the coal ash sample according to GB / T 212-2008 "Industrial Analysis Methods of Coal": Spread the coal sample smaller than 0.2 mm evenly in an ash dish so that it does not exceed 0.15 g per square centimeter, place the ash dish into the constant temperature zone of a muffle furnace with a furnace temperature not exceeding 100°C, close the furnace door and leave a 15 mm gap in the furnace door, slowly raise the furnace temperature to 500°C in no less than 30 minutes, and keep it at this temperature for 30 minutes, continue to raise the temperature to 815±10°C, and burn at this temperature for 1 hour.

[0041] Step 2: Apply rosin on the central area of ​​the sapphire sheet, adhere a small amount of prepared ash sample to the rosin, blow it thoroughly with an ear bulb, place the sapphire sheet with the ash sample in the center of the bottom of the heating crucible, turn on the electronic camera and the imaging display system connected to it, adjust the magnification and focal length to make more coal ash particles clearly appear in the imaging display system.

[0042] Step 3: Connect the heating platform and the upper cover of the heating platform, introduce the required atmosphere and open the cooling water circuit. Turn on the heating system, the heating rate is 30°C / min below 900°C, and the heating rate is 5°C / min above 900°C. During the heating process, the morphological changes of each coal ash particle are recorded every 20°C.

[0043] Step 4: Use image processing software to analyze the change in particle area at different temperatures. When the particle area reaches the minimum, record the temperature as the melting temperature of the particle, and obtain the melting temperatures of all particles in turn.

[0044] Step 5. To reduce experimental and analytical errors, the experiment was repeated three times, and the number of molten particles at different temperatures was counted to obtain a curve of the ratio of molten particles to the total number of particles as a function of temperature. The experimental results were used to guide the selection of the boiler screen bottom flue gas temperature and the furnace outlet flue gas temperature.

[0045] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0046] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A device for predicting coal ash slagging characteristics, comprising an electronic camera (1), a lens (2), a light source (3), a filter (4), a quartz glass (5), a heating platform cover (6), a sapphire sheet (7), an ash sample (8), a heating crucible (9), a heating platform (10), a heating wire (11), a thermocouple (12), an air inlet pipe (13), and an air outlet pipe (14), wherein the filter (4) is connected to the lens (2) by means of threads, the light source (3) is arranged around the lens (2), the quartz glass (5) is embedded in the heating platform cover (6), the heating platform cover (6) is connected to the heating platform (10) by means of bolts, the heating crucible (9) is fixed at the central position of the bottom of the heating platform (10), the sapphire sheet (7) is placed at the central position of the bottom of the heating crucible 9, the ash sample (8) is placed on the sapphire sheet (7), and the heating wire (11) and the thermocouple (12) are wound around the bottom of the heating crucible (9).

2. The device for predicting coal ash slagging characteristics according to claim 1, characterized in that A filter (4) is arranged under the lens (2), and the filter (4) only allows light of a corresponding central wavelength to pass through. The light source (3) is arranged around the lens (2), and the wavelength of the light source (3) is consistent with the central wavelength of the filter (4).

3. A method for predicting coal ash slagging characteristics, characterized in that The following steps are involved: Step 1: Prepare coal ash samples according to GB / T 212-2008 "Industrial Analysis Methods of Coal": Spread coal samples smaller than 0.2 mm evenly in an ash dish so that they do not exceed 0.15 g per square centimeter, place the ash dish in a constant temperature zone of a muffle furnace with a furnace temperature not exceeding 100°C, close the furnace door and leave a 15 mm gap in the furnace door, slowly raise the furnace temperature to 500°C in no less than 30 minutes, and keep it at this temperature for 30 minutes, continue to raise the temperature to 815±10°C, and burn it at this temperature for 1 hour. Step 2: Apply rosin to the central area of ​​the sapphire sheet, adhere a small amount of prepared ash sample to the rosin, blow it thoroughly with an ear-cleaning bulb, place the sapphire sheet with the ash sample in the central position of the bottom of the heating crucible, turn on the electronic camera and the imaging display system connected to it, adjust the magnification and focal length, so that more coal ash particles are clearly displayed in the imaging display system. Step three, connect the heating table and the upper cover of the heating table, introduce the required atmosphere and open the cooling water circuit. Turn on the heating system, the heating rate is 30°C / min below 900°C, and the heating rate is 5°C / min above 900°C. Record the morphology changes of each coal ash particle every 20°C during the heating process. Step four, use image processing software to analyze the change of particle area at different temperatures. When the particle area reaches the minimum, record the temperature as the melting temperature of this particle, and obtain the melting temperature of all particles in turn. Step five, in order to reduce the experimental and analysis errors, repeat the experiment three times, count the number of molten particles at different temperatures, and obtain the curve of the proportion of molten particles to the total number of particles as the temperature changes, to guide the selection of the flue gas temperature at the bottom of the boiler screen and the flue gas temperature at the furnace outlet.

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