A device and method for controlling fly ash deposition layer based on impinging stream technology

Abstract

The present invention discloses a device and method for regulating the fly ash deposition layer based on the impinging flow technology, which belongs to the technical field of ash accumulation prevention and control. The device for regulating the fly ash deposition layer based on the impinging flow technology of the present invention comprises a high-temperature furnace, a nanoparticle injection system and a fly ash injection system, wherein the nanoparticle injection system and the fly ash injection system are respectively used to spray nanoparticles and micron fly ash into the interior of the high-temperature furnace, and their injection directions are relatively arranged. The method for regulating the fly ash deposition layer of the present invention, by introducing nanoparticles into the interior of the high-temperature furnace, coats the surface of the coal-fired fly ash with nanoparticles, thereby effectively reducing its surface viscosity, and regulating the structure and composition of the fly ash deposition layer, ultimately achieving the purpose of significantly improving the ash deposition problem.

Description

Technical Field

[0001] The present invention belongs to the technical field of ash accumulation prevention and control, and more specifically, relates to a device and method for regulating fly ash deposition layers based on impinging flow technology, which is mainly used to solve the problems of ash and slagging on the heat exchange surface of power plant boilers, and is also applicable to other related fields. Background Art

[0002] High-alkali coal offers advantages such as low ignition temperature, high burnout rate, high combustion economy, and low pollutant emissions, making it an excellent power coal and in line with my country's energy conservation and emission reduction goals. However, due to its high ash content of Na2O and CaO, low SiO2 and Al2O3, and high ash melting point, high-alkali coal is prone to ash and slagging problems in coal-fired boiler heat exchangers. Currently, Xinjiang Zhundong coal, with its abundant reserves, has attracted widespread attention. Due to insufficient understanding of Zhundong coal's characteristics, some power plant boilers blended with Zhundong coal have experienced severe ash and slagging problems, resulting in frequent boiler shutdowns and severely restricting its development and utilization. Therefore, finding effective methods to control ash deposition in highly contaminating coals is a pressing issue.

[0003] Currently, research on controlling ash deposition in high-alkalinity contaminated coal focuses on the following main areas: 1) Sodium removal and quality improvement: This involves pre-treating the Jungdong coal to reduce its sodium content and improve its quality. Currently under development, sodium removal methods include water washing, hydrothermal treatment, microwave treatment, ion exchange, and CO2-H2O water treatment. These methods can achieve relatively high sodium removal rates under certain conditions, but the scale-up costs associated with these pre-treatment methods need further consideration. 2) Blending: Adding mineral additives to the combustion process of Jungdong coal chemically reacts with alkali metals, thereby immobilizing them. For example, kaolin, a common silica-alumina clay mineral, can effectively immobilize some alkali metals. 3) Co-firing: Blending Jungdong coal with other fuels, such as bituminous coal, oil shale and its semi-coke, sewage sludge, and biomass. This method can, to a certain extent, reduce the fly ash deposition tendency of Zhundong coal, but the selection and proportion of the blended fuel, as well as its impact on pollutants and combustion characteristics, require further evaluation. 4) Regarding combustion process improvements, some scholars have proposed the use of liquid slag removal, which captures alkali metal particles by forming a liquid film on the inner wall of the furnace, facilitating the timely discharge of coal ash in the form of liquid slag, thereby reducing the release of fly ash and mitigating the tendency to foul. 5) Coating technology: The use of special coatings on heat exchangers can reduce the adhesion rate of fly ash impacting the wall, thereby achieving the purpose of slag resistance and wear prevention. However, research has shown that in terms of control effectiveness, these methods each have their own advantages and disadvantages, and more or less face some key issues that need to be addressed, such as high investment costs, poor operability, and unstable results.

[0004] For example, Chinese patent application No. 2017112290742 discloses a method for preventing and controlling fouling and slagging in pulverized coal boilers based on particle condensation. This method involves conveying silicon- and aluminum-rich material particles into the boiler furnace via a conveying pipe and spraying the particles through a nozzle into the upper flue gas temperature range of 900-1200°C. The particle size is controlled between 5 and 200 μm and the temperature is below 600°C. This application effectively controls the fouling and slagging problems caused by burning high-alkali metal fuels by injecting low-temperature particles into the boiler furnace, causing the alkali metal vapor in the flue gas to condense on the low-temperature particles. The main feature of this application is that the injection of low-temperature particles is used to regulate the gasification and condensation mechanism of the alkali metal vapor to improve the deposition of fly ash, which is significantly different from the regulation method proposed in this patent.

[0005] For example, the Chinese patent application number 202010269862X discloses a method for preventing and controlling slagging and contamination of high-alkali coal based on in-furnace zoning control. The application includes the following steps: 1) Dividing the boiler furnace into slagging zone, severe contamination zone, strong contamination zone and general contamination zone according to temperature; 2) By reducing the furnace cross-section heat load and the burner area wall heat load parameters, the slagging zone is controlled to the area from the burner to the height of the overburnt air, reducing the range of the slagging zone and narrowing the temperature window for alkali metal release; 3) By reducing the furnace volume heat load parameters, the severe contamination zone is controlled to the area from the overburnt air to the furnace outlet, and a large amount of alkali metal compounds are deposited in the severe contamination zone; 4) Through reasonable heating surface arrangement, the strong contamination zone is controlled to the horizontal flue area, reducing the probability of contamination of the horizontal flue heating surface; 5) Through reasonable heating surface arrangement, the general contamination zone is controlled to the tail flue area. This application utilizes temperature and time control in different zones of the boiler to maximize Na capture within the furnace. Small amounts of Na are actively removed to control slagging and fouling. This is completely different from the control method proposed in this patent. Summary of the Invention

[0006] 1. Problem to be solved

[0007] To address the shortcomings of existing technologies in effectively addressing the severe ash accumulation on boiler heating surfaces during the combustion and utilization of high-alkalinity contaminated coal, a device and method for controlling fly ash deposition using impinging stream technology are provided. This invention utilizes impinging stream technology to surface-modify fly ash from high-alkalinity coal combustion, resolving the fly ash deposition problem during the use of high-alkalinity coal. This approach is of great significance for the widespread application of high-alkalinity coal.

[0008] 2. Technical Solution

[0009] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0010] The present invention provides a device for regulating the fly ash deposition layer based on impinging flow technology, which includes a high-temperature furnace, a nanoparticle injection system and a fly ash injection system. The nanoparticle injection system and the fly ash injection system are respectively used to inject nanoparticles and micron fly ash into the high-temperature furnace, and their injection directions are relatively set.

[0011] Furthermore, the nanoparticle injection system includes a nanoparticle nozzle and a nanoparticle feeding unit, and the fly ash injection system includes a fly ash particle nozzle and a fly ash feeding unit. The discharge ends of the nanoparticle nozzle and the fly ash particle nozzle both extend into the high-temperature furnace and are arranged in a counter-positioned manner.

[0012] Furthermore, the nanoparticle feeding unit and the fly ash feeding unit both adopt fluidized bed feeding devices, and the corresponding fluidized bed feeding devices are connected to the feeding ends of the nanoparticle nozzle and the fly ash particle nozzle, respectively.

[0013] Furthermore, the nanoparticle feeding unit includes a first micro-fluidized bed, which is connected to a first mixing device through a first plunger pump, and the first mixing device is used to stir and mix the nanoparticles and water; the fly ash feeding unit includes a second micro-fluidized bed, which is connected to a second mixing device through a second plunger pump, and the second mixing device is used to stir and mix the fly ash particles and water.

[0014] Furthermore, the nanoparticle injection system and the fly ash injection system are both connected to a blowing gas supply unit.

[0015] Furthermore, the injection gas supply unit includes an air compressor, a flow control device and a preheating device. The gas output by the air compressor is respectively transported to the nanoparticle injection system, the fly ash injection system and the high-temperature furnace after passing through the flow control device and the preheating device.

[0016] Furthermore, it also includes an ash sampling unit, a smoke treatment unit and a monitoring unit. The ash sampling unit uses a temperature-controllable ash sampling probe to collect the deposited ash inside the furnace; the smoke treatment unit is used to condense, remove dust and discharge the flue gas generated by the high-temperature furnace; the monitoring unit includes a high-speed camera to capture the movement trajectory of nanoparticles and micron fly ash particles.

[0017] The invention provides a method for regulating a fly ash deposition layer, which introduces nanoparticles into a high-temperature furnace so that the surface of high-alkali coal-fired fly ash is coated with the nanoparticles.

[0018] Furthermore, the nanoparticles are SiO2, Al2O3, TiO2 or kaolin.

[0019] Furthermore, the surface of high-alkali coal-fired fly ash is coated with nanoparticles by means of impinging streams.

[0020] 3. Beneficial effects

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention provides a device for regulating the fly ash deposition layer based on the impinging stream technology, comprising a high-temperature furnace, a nanoparticle injection system and a fly ash injection system. By injecting nanoparticles into the high-temperature furnace, the surface of the fly ash particles is coated with nanoparticles, thereby regulating the structure and composition of the fly ash deposition layer and reducing its surface viscosity, thereby achieving the purpose of significantly improving the ash deposition problem.

[0023] (2) The present invention provides a device for regulating the fly ash deposition layer based on the impinging stream technology. Based on the impinging stream technology, nanoparticles are used to perform surface modification on the fly ash. This modification method is selective and can effectively reduce the viscosity of highly viscous fly ash, thereby enabling targeted regulation of the deposited ash. At the same time, the present invention combines the impinging stream technology with the fluidized bed technology to establish a complete set of measurement technology systems, and monitors and evaluates the fly ash modification effect through the setting of the ash accumulation sampling unit and the monitoring unit. Therefore, the system can be used to study the modification effect between nanoparticles and fly ash under different conditions (such as gas flow rate, temperature, etc.) to better solve the ash accumulation problem of different coals. At the same time, the system is easy to operate and can effectively improve efficiency.

[0024] (3) The present invention provides a device for regulating the fly ash deposition layer based on the impinging flow technology, wherein the blowing gas supply unit includes an air compressor, a flow control device and a preheating furnace. The flow control device can control the gas flow generated by the air compressor, thereby facilitating the regulation of the gas flow delivered to various locations. The setting of the preheating device can heat the blowing gas and regulate its temperature.

[0025] (4) The device of the present invention for controlling the fly ash deposition layer based on the impinging flow technology can not only solve the problem of development and utilization of high-alkali coal such as Zhundong coal, but also help solve the serious ash deposition problem in other fields. It is different from any previous control technology, shows significant innovation, has the potential for further development and application, and has advantages in operation, cost and efficiency.

[0026] (5) The present invention provides a method for regulating the fly ash deposition layer. By modifying the fly ash particles with nanoparticles, the structure and composition of the fly ash deposition layer can be regulated, effectively solving the ash accumulation problem existing in the application of high-alkali coal powder combustion. By adjusting the flow rate and temperature of the injection gas, the modification effect of the fly ash particles can be effectively guaranteed to meet the application requirements of different types of coal. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic structural diagram of a device for regulating fly ash deposition layer based on impinging stream technology according to the present invention;

[0028] Figure 2 Schematic diagram of the impact wall between fly ash and nanoparticles.

[0029] Description of the numbers in the figure:

[0030] 1. First mixing device; 2. First plunger pump; 3. First micro fluidized bed; 4. High-temperature furnace; 5. Nanoparticle nozzle; 6. Fly ash particle nozzle; 7. Second micro fluidized bed; 8. Second plunger pump; 9. Second mixing device; 10. Preheating device; 11. Flow control device; 12. Air compressor; 13. Temperature-controlled ash sampling probe; 14. Flue gas cooling device; 15. Dust removal device; 16. Induced draft fan; 17. High-speed camera. DETAILED DESCRIPTION

[0031] Example 1

[0032] To address the problem of fly ash deposition on boiler heating surfaces when using high-alkali coal, such as Zhundong coal, this embodiment proposes a method for regulating fly ash deposition. This method involves introducing nanoparticles into the high-temperature furnace chamber, coating the surface of the fly ash from the high-alkali coal with the nanoparticles, and thereby modifying the fly ash particles. Coating the fly ash with nanoparticles effectively reduces its surface viscosity while simultaneously regulating the structure and composition of the fly ash deposition layer, ultimately significantly improving the ash deposition problem.

[0033] Example 2

[0034] Specifically, the method for regulating the fly ash deposition layer of this embodiment uses impinging stream technology to coat the surface of the high-alkali coal-fired fly ash with nanoparticles. The nanoparticles can be preferably SiO2, Al2O3, TiO2 or kaolin according to the circumstances.

[0035] Example 3

[0036] like Figure 1As shown, the device for controlling the fly ash deposition layer based on the impinging stream technology of this embodiment includes a high-temperature furnace 4, a nanoparticle injection system, and a fly ash injection system. The nanoparticle injection system and the fly ash injection system are respectively used to inject nanoparticles and micron fly ash into the interior of the high-temperature furnace 4, and their injection directions are arranged relative to each other. Specifically, the nanoparticle injection system includes a nanoparticle nozzle 5 and a nanoparticle feeding unit, and the fly ash injection system includes a fly ash particle nozzle 6 and a fly ash feeding unit. The discharge ends of the nanoparticle nozzle 5 and the fly ash particle nozzle 6 both extend into the interior of the high-temperature furnace 4 and are arranged relative to each other. Nanoparticles and fly ash are fed respectively through the nanoparticle feeding unit and the fly ash feeding unit. Nanoparticles and fly ash are respectively injected into the interior of the high-temperature furnace 4 through the nanoparticle nozzle 5 and the fly ash particle nozzle 6 in a counter-injected manner, thereby achieving surface modification of the fly ash particles based on the impinging stream technology.

[0037] Example 4

[0038] The structure of the device for controlling the fly ash deposition layer based on the impinging stream technology of this embodiment is basically the same as that of Example 3, with the main difference being that, in order to accurately control the concentration of particles and ensure stable operation over a long period of time, the nanoparticle feeding unit and the fly ash feeding unit of this embodiment both use fluidized bed feeding devices, and the corresponding fluidized bed feeding devices are respectively connected to the feed ends of the nanoparticle nozzle 5 and the fly ash particle nozzle 6. Specifically, the nanoparticle feeding unit includes a first microfluidized bed 3, which is connected to a first mixing device 1 via a first plunger pump 2, and the first mixing device 1 is used to stir and mix the nanoparticles and water; the fly ash feeding unit includes a second microfluidized bed 7, which is connected to a second mixing device 9 via a second plunger pump 8, and the second mixing device 9 is used to stir and mix the fly ash particles and water. The nanoparticle injection system and the fly ash injection system are both connected to a blowing gas supply unit, which provides primary fluidizing air to the bottom of the fluidized bed and secondary blowing air flow to the interior of the nozzle.

[0039] The injection gas supply unit in this embodiment includes an air compressor 12, a flow control device 11, and a preheating furnace 10. The flow control device 11 allows for the control of the gas flow rate delivered to various locations, while the preheating device 10 allows for the preheating of the injection gas and the regulation of its temperature. Temperature is a key factor influencing particle adhesion, and this embodiment takes this influence into account. The furnace chamber utilizes silicon carbon rods for heating, with a maximum design temperature of approximately 1300°C. A secondary entrained air flow enters the furnace chamber after preheating.

[0040] The device for controlling the fly ash deposition layer in this embodiment further includes an ash sampling unit, a smoke treatment unit and a monitoring unit, wherein the ash sampling unit uses a temperature-controllable ash sampling probe 13 for collecting the deposited ash inside the furnace. Figure 2 As shown, after being modified by the impinging flow, fly ash particles fall into three categories: particles completely or minimally coated with nanoparticles (a), particles completely or largely coated with nanoparticles (b), and particles containing very few nanoparticles (c). These particles will collide with the wall, depositing onto it or rebounding. Due to differences in their surface properties, the deposition tendency of these particles upon collision with the wall varies significantly, and the structure and composition of the deposited ash also change accordingly. Therefore, a temperature-controlled ash sampling probe is placed horizontally at the bottom of the furnace to collect the deposited ash, allowing for evaluation of the fly ash deposition characteristics under different impinging flow conditions. The dust treatment unit (including a flue gas cooling device 14, a dust removal device 15, and an induced draft fan 16) is used to condense, remove dust, and discharge the flue gas generated by the high-temperature furnace 4. The monitoring unit includes a high-speed camera 17 to capture the trajectory of nanoparticles and micron fly ash particles. Specifically, an observation window is installed on the side of the nozzle to facilitate the measurement of particle flow, and then a backlight source and a high-speed camera 17 are used to form a measurement system to generate a narrow depth of field for 2D plane imaging, thereby capturing the movement trajectory of the particles.

[0041] The specific principle of this embodiment is as follows: nanoparticles and water are mixed by magnetic stirring in the first mixing device 1, and fly ash particles are mixed with water in the second mixing device 9. Then, the mixture of particles and water is quantitatively controlled by the first plunger pump 2 and the second plunger pump 8 to enter the first micro fluidized bed 3 and the second micro fluidized bed 7. A small amount of water will evaporate quickly, and the nanoparticles and fly ash particles will enter the nanoparticle nozzle 5 and the fly ash particle nozzle 6 respectively under the influence of the primary fluidizing air, and will be sprayed into the furnace under the action of the secondary blowing airflow. A collision surface will be formed somewhere in the middle of the two nozzles. In this range, the micron particles and nanoparticles will collide violently. Figure 2 As shown, particles with high viscosity will be coated by nanoparticles, while particles with low viscosity may only be partially coated or not coated with nanoparticles. This can effectively reduce the deposition rate of fly ash particles with high viscosity, and ultimately achieve the purpose of regulating the deposition layer. It should be noted that, for the sake of simplicity, Figure 1Only two nozzles are used for illustration, but in fact, more nozzles and more flexible arrangements can be considered as needed. There are many factors that affect the coating effect of nanoparticles, such as the type and particle size of the nanoparticles and operating conditions (such as temperature, speed and nozzle arrangement, etc.). Since the physical and chemical properties of fly ash particles produced by different coal combustion are quite different, the device of this embodiment can simulate the modification of different fly ashes under different conditions (different temperatures, gas flow rates) and monitor the modification effects, and select suitable nanoparticles and optimal operating conditions based on the actual effects, thereby providing a reliable basis for preventing and controlling ash accumulation in the actual application of different types of coal combustion.

Claims

1. A device for controlling fly ash deposition based on impinging stream technology, characterized by: It comprises a high-temperature furnace (4), a nanoparticle injection system and a fly ash injection system, wherein the nanoparticle injection system and the fly ash injection system are respectively used to inject nanoparticles and micron fly ash into the high-temperature furnace (4), and the injection directions thereof are arranged relative to each other; The nanoparticle injection system comprises a nanoparticle nozzle (5) and a nanoparticle feeding unit, and the fly ash injection system comprises a fly ash particle nozzle (6) and a fly ash feeding unit; The nanoparticle feeding unit and the fly ash feeding unit both adopt fluidized bed feeding devices, and the corresponding fluidized bed feeding devices are respectively connected to the feeding ends of the nanoparticle nozzle (5) and the fly ash particle nozzle (6); the nanoparticle feeding unit comprises a first micro fluidized bed (3), the first micro fluidized bed (3) is connected to a first mixing device (1) via a first plunger pump (2), and the first mixing device (1) is used to stir and mix the nanoparticles and water; the fly ash feeding unit comprises a second micro fluidized bed (7), the second micro fluidized bed (7) is connected to a second mixing device (9) via a second plunger pump (8), and the second mixing device (9) is used to stir and mix the fly ash particles and water; The nanoparticle injection system and the fly ash injection system are both connected to a blowing gas supply unit; the blowing gas supply unit comprises an air compressor (12), a flow control device (11) and a preheating device (10); the gas output by the air compressor (12) passes through the flow control device (11) and the preheating device (10) and is respectively transported to the nanoparticle injection system, the fly ash injection system and the high-temperature furnace (4).

2. The device for controlling fly ash deposition layer based on impinging stream technology according to claim 1, characterized in that: The discharge ends of the nanoparticle nozzle (5) and the fly ash particle nozzle (6) both extend into the interior of the high-temperature furnace (4) and are arranged in a counter-positioned manner.

3. A device for controlling fly ash deposition layer based on impinging stream technology according to any one of claims 1-2, characterized in that: The system also includes an ash sampling unit, a smoke treatment unit, and a monitoring unit, wherein the ash sampling unit uses a temperature-controllable ash sampling probe (13) for collecting deposited ash inside the furnace; the smoke treatment unit is used to condense, remove dust, and discharge the smoke generated by the high-temperature furnace (4); and the monitoring unit includes a high-speed camera (17) for capturing the movement trajectory of nanoparticles and micron fly ash particles.

4. A method for regulating a fly ash deposition layer, characterized in that: Nanoparticles are introduced into the high-temperature furnace (4) using the device described in claim 1, and the surface of the high-alkali coal-fired fly ash is coated with the nanoparticles by means of impact flow.

5. The method for controlling the fly ash deposition layer according to claim 4, characterized in that: The nanoparticles are SiO2, Al2O3, TiO2 or kaolin.

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