Cooling feeding blending device and cooling feeding blending treatment method for large coal-fired boiler blending

Abstract

The application relates to the technical field of fuel blending combustion treatment, in particular to a cooling feeding blending combustion equipment and a cooling feeding blending combustion treatment method for large-scale coal-fired boilers. In the application, the pulverized fuel is carried into a combustion furnace by cold flue gas, oxygen content is reduced, and fuel is prevented from being combusted in advance; during the feeding process, the primary air is blown into the feeding pipe by using the air inlet main pipe and the air inlet branch pipe, so that the feeding pipe is lower than 200 DEG C, and the fuel is prevented from being cracked in advance; the air cannon is used for blowing, so that the material blocking problem is solved; the microwave is used for heating and melting, so that the coking problem is solved; the online camera is arranged in the connecting section of the pulverizer and the feeding pipe, so that the feeding pipe internal feeding condition can be observed, and the blocking problem can be found in time.

Description

Technical Field

[0001] This application relates to the field of fuel blending technology, and in particular to a cooling feed blending equipment and a cooling feed blending method for large coal-fired boilers. Background Technology

[0002] Currently, there are various technical approaches for coal-fired power plants coupled with biomass in power generation projects. Biomass fuels entering the plant come in various shapes, including powder, bulk, pellets, and briquettes. Pulverization methods include using existing coal mills for separate pulverization, coal and biomass mixed pulverization, and independent biomass mills for separate pulverization. Coupling systems include installing new biomass burners in the boiler or utilizing existing coal burners. In existing projects, the biomass co-firing rate or proportion is relatively low, with the actual co-firing rate often significantly lower than the designed rate. Biomass powder has physical properties compared to coal powder, such as higher viscosity, lower density, softness, and easy hygroscopicity. Other biomass fuels have lower calorific value and poorer grindability, which can cause problems such as reduced grinding output in the pulverization system. Furthermore, issues such as easy blockage and inability to continuously and stably operate the biomass feeding and conveying system need to be addressed. Summary of the Invention

[0003] The technical problem to be solved by this invention is that the feeding system in the process of co-firing biomass in large coal-fired boilers is prone to clogging and premature combustion.

[0004] Therefore, the present invention provides a cooling feed co-firing device and a cooling feed co-firing treatment method for co-firing in large coal-fired boilers.

[0005] The technical solution adopted by this invention to solve its technical problem is: A cooling feed co-firing device for co-firing in large coal-fired boilers, comprising: Crusher, and A feed pipe is connected to the side wall of the combustion furnace. An air cannon and a microwave source are installed on the feed pipe. The air cannon is located on the side of the microwave source away from the combustion furnace. The main air inlet pipe is connected to the side wall of the combustion furnace and located above the feed pipe. Multiple branch air inlet pipes are connected between the main air inlet pipe and the feed pipe. A connecting pipe is used to connect the crusher and the feed pipe, and the connecting pipe is used to introduce cold flue gas into the feed pipe.

[0006] Furthermore, an observation hole is provided on the feed pipe, and an online camera is installed at the observation hole. The online camera is used to monitor the internal condition of the feed pipe.

[0007] Furthermore, the end of the feed pipe connected to the combustion furnace is horizontally arranged, the connecting pipe is located below the feed pipe and is arranged parallel to the feed pipe, and the end of the feed pipe away from the combustion furnace is bent downward.

[0008] Furthermore, the angle α at which the end of the feed pipe furthest from the combustion furnace bends downward is 10°~90°.

[0009] Furthermore, the angle α at which the end of the feed pipe furthest from the combustion furnace bends downward is 30°.

[0010] Furthermore, a one-way valve is connected to the connecting pipe, each air inlet branch pipe, and between the air cannon and the feed pipe, and a regulating valve is provided on each air inlet branch pipe and between the air cannon and the feed pipe.

[0011] Furthermore, it also includes a sensor assembly and a controller. The sensor assembly includes a thermometer installed in each air inlet pipe, a temperature sensor, a pressure sensor, a wind speed sensor installed in the feed pipe, and an online camera installed in the feed pipe. The controller is connected to the crusher, the air cannon, the microwave source, the online camera, and the sensor assembly.

[0012] A method for co-firing cooling feed for large coal-fired boilers includes, Step 1: Introduce primary air into the main air inlet pipe. The temperature of the primary air should be below 40℃. Control the opening of the regulating valve to ensure that the air velocity in each air inlet branch pipe reaches the set requirement. Step 2: Start the crusher and crush the fuel into particles smaller than 50 micrometers. Then, introduce dried cold flue gas (temperature below 80℃, pressure 10-15kPa, flow rate 50-70m / s) into the connecting pipe. The cold flue gas carries the crushed fuel through a one-way valve, through the feed pipe, and mixes with the incoming air from the air inlet pipe before entering the furnace for combustion. When the surface temperature of the feed pipe is higher than 200℃, the primary air flow is increased by the regulating valve on the air inlet branch pipe to keep the feed pipe temperature below 200℃.

[0013] Furthermore, during the feeding process, the temperature and pressure of the feed pipe are monitored. When the pressure of the feed pipe reaches 0.3 MPa, the air cannon is activated to purge the feed pipe with high-pressure air and the primary air volume is increased to clear the feed pipe and reduce the pressure to below 0.1 MPa.

[0014] Furthermore, if the feed pipe pressure cannot be reduced, when the temperature on the side of the feed pipe near the combustion furnace reaches 600°C and the feed pipe pressure reaches 0.5 MPa, and the online camera image shows coking inside the feed pipe, the microwave source is activated, and microwaves are radially transmitted to the feed pipe through a single-mode microwave waveguide to heat the molten coking in the center of the feed pipe; when the temperature on the side of the feed pipe near the combustion furnace is higher than 800°C, it indicates that the coking has reached the coking melting temperature, the air cannon is activated to purge the feed pipe, and then the primary air volume is increased to remove the coking.

[0015] The beneficial effects of this invention are as follows: It proposes a feeding cooling structure, combined with cold flue gas to carry the pulverized fuel, reducing oxygen content and preventing premature combustion; it utilizes a single-pass method to keep the feed pipe below 200°C, preventing premature fuel decomposition; it uses air cannons to blow away grease, solving the problem of material blockage; it uses microwave heating to melt the material, solving the problem of coking; and it installs an online camera at the connection between the pulverizer and the feed pipe to observe the feeding process inside the feed pipe and promptly detect blockages. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Figure 1 This is a schematic diagram of the cooling feed and co-firing equipment used in large coal-fired boilers according to the present invention.

[0018] Figure 2 This is a CFD simulation diagram of the speed, pressure, and temperature distribution during feeding through a 30° bent feed pipe in this invention.

[0019] Figure 3 This is a CFD simulation diagram of the speed, pressure, and temperature distribution during feeding through a 60° bent feed pipe in this invention.

[0020] Figure 4 This is a CFD simulation diagram of the speed, pressure, and temperature distribution during feeding through a 90° bent feed pipe in this invention.

[0021] Figure 5 This is a schematic diagram of the thermogravimetric curve of straw pyrolysis in this invention.

[0022] Figure 6 This is a schematic diagram of the thermogravimetric curve of straw combustion in this invention.

[0023] In the diagram: 1. Crusher; 2. Connecting pipe; 3. Feed pipe; 4. Check valve; 5. Main air inlet pipe; 6. Branch air inlet pipe; 7. Air cannon; 8. Microwave source; 9. Controller; 10. Combustion furnace; 11. Online camera; 12. Regulating valve. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0025] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] A cooling feed co-firing device for co-firing in large coal-fired boilers includes a crusher 1, a connecting pipe 2, a feed pipe 3, an air inlet main pipe 5, an air cannon 7, a microwave source 8, a combustion furnace 10, a sensor assembly, and a controller 9.

[0028] The feed pipe 3 is connected to the side wall of the combustion furnace 10 and is located in the middle of the combustion furnace 10. The main air inlet pipe 5 is connected to the side wall of the combustion furnace 10 and is located at the top. Multiple air inlet branch pipes 6 are connected between the feed pipe 3 and the main air inlet pipe 5. The multiple air inlet branch pipes 6 are arranged along the length of the main air inlet pipe 5. Each air inlet branch pipe 6 is equipped with a one-way valve 4 and a regulating valve 12. The one-way valve 4 ensures that primary air flows only from the main air inlet pipe 5 to the feed pipe 3. A thermometer is installed on each air inlet branch pipe 6.

[0029] Connecting pipe 2 connects the crusher 1 and the feed pipe 3. A one-way valve 4 is also connected to connecting pipe 2. One end of connecting pipe 2 is used to receive cold flue gas, and connecting pipe 2 is used to discharge the crushed shaped fuel into the feed pipe 3. It should be noted that the side of the feed pipe 3 connected to the combustion furnace 10 is horizontally positioned, while the side of the feed pipe 3 near connecting pipe 2 is bent downwards at a bending angle α of 10°~90°, preferably α of 30°. Thus, connecting pipe 2 is located below the end of the feed pipe 3 connected to the combustion furnace 10, and the horizontal portions of connecting pipe 2 and feed pipe 3 are parallel to each other. An online camera 11 is installed inside the feed pipe 3. The online camera 11 is used to monitor the horizontal part of the feed pipe 3. The air cannon 7 and the microwave source 8 are both installed on the horizontal part of the feed pipe 3. A one-way valve 4 and a regulating valve 12 are also installed between the air cannon 7 and the feed pipe 3, so that the air flows unidirectionally from the air cannon 7 to the feed pipe 3. The air cannon 7 is installed on the side of the microwave source 8 away from the combustion furnace 10. Multiple passages can be provided between the microwave source 8 and the feed pipe 3.

[0030] The sensor assembly includes a thermometer installed in each air inlet pipe 6, a temperature sensor, a pressure sensor, and a wind speed sensor installed in the feed pipe 3. The controller 9 is connected to the crusher 1, the air cannon 7, the microwave source 8, the online camera 11, and the sensor assembly.

[0031] CFD simulations were performed on the velocity, pressure, and temperature distributions of feed pipe 3 at different bend angles α (30°, 60°, and 90°). The results are as follows: Figure 2 , Figure 3 , Figure 4 As shown: Figure 2 As shown, (a) the small figure shows the velocity distribution of the 30° elbow feed pipe 3, (b) the small figure shows the pressure distribution of the 30° elbow feed pipe 3, and (c) the small figure shows the temperature distribution of the 30° elbow feed pipe 3; Figure 3 As shown, (a) the small figure shows the velocity distribution of the 60° elbow feed pipe 3, (b) the small figure shows the pressure distribution of the 60° elbow feed pipe 3, and (c) the small figure shows the temperature distribution of the 60° elbow feed pipe 3; Figure 4 As shown, (a) the small figure shows the velocity distribution of the 90° elbow feed pipe 3, (b) the small figure shows the pressure distribution of the 90° elbow feed pipe 3, and (c) the small figure shows the temperature distribution of the 90° elbow feed pipe 3.

[0032] In the 90° bend design, the fluid generates significant centrifugal force during the abrupt turn, resulting in highly uneven velocity distribution within the pipe cross-section: a localized high-velocity zone appears near the inner wall, while the velocity decreases significantly near the outer wall, with the velocity gradient being the largest and the flow efficiency the lowest in the pipe bend area. In contrast, the 60° bend has a smoother streamline, reducing the velocity difference between the inner and outer sides of the flow field, and the velocity distribution tends to be more uniform; the 30° bend design completes the turn almost on a smooth curve, with the smallest velocity gradient in the mainstream area and a relatively uniform radial velocity distribution. Regarding the number of inlets, the three-inlet design further improves the uniformity of velocity distribution. The three-pipe design disperses material and gas into the main delivery pipe from three directions, forming multiple symmetrical superimposed flow streams, resulting in a more stable velocity field across the cross-section.

[0033] The calculated velocity, pressure, and temperature are shown in Table 1.

[0034] Table 1. Speed, Pressure, and Temperature Conditions

[0035] As shown in Table 1, the 90° bend design resulted in enhanced localized heat retention due to the intensified vortex flow, leading to a more concentrated high-temperature region. In contrast, the 30° bend provided a smoother flow, more uniform temperature distribution, and smaller temperature differences. The smaller bend angle is beneficial for improving the gas-solid mixing efficiency and acceleration effect in the acceleration section, thereby increasing the material flow velocity in feed pipe 3, improving velocity uniformity, reducing pressure drop in feed pipe 3, and resulting in more uniform temperature distribution. In conclusion, using a 30° bend in conjunction with three feed inlets can improve the heat exchange efficiency of the gas-solid flow, ensure uniform heating of particles, and thus improve the thermal performance of the conveying system. Therefore, the 30° bend design was ultimately selected for implementation. A method for co-firing cooling feed for large coal-fired boilers, comprising: Step 1: Introduce primary air (below 40℃) into the main air inlet pipe 5, and control the opening of the regulating valve 12 to ensure that the air velocity in each air inlet branch pipe 6 reaches the set requirement (20m / s, adjustable) to prevent primary air backflow. According to thermogravimetric analysis, if... Figure 5 As shown, the cellulose in straw begins to decompose at 200℃. Therefore, when the surface temperature of the feed pipe 3 is higher than 200℃, the primary airflow needs to be increased through the regulating valve 12 on the air inlet pipe 6 to keep the temperature of the feed pipe 3 below 200℃, in order to prevent the fuel from decomposing due to heat.

[0036] Step 2: Start the crusher 1 to crush the fuel into a certain particle size (particle size below 50 micrometers to facilitate pneumatic conveying). Extract the flue gas (150℃) in front of the chimney for cooling and drying. Then, introduce the dried cold flue gas (temperature below 80℃, pressure 10-15kPa, flow rate 50-70m / s). The cold flue gas has a low oxygen content, forming an inert atmosphere to prevent premature oxidation of the fuel. Carrying the crushed fuel, it passes through the one-way valve 4, through the feed pipe 3, and mixes with the incoming air from the air inlet pipe 6 before entering the furnace for combustion. The third step is to monitor the feed. S3.1 Monitors the temperature and pressure of feed pipe 3 to prevent premature combustion and fuel blockage. Based on the thermogravimetric analysis of straw combustion, such as... Figure 6 As shown, lignin in straw decomposes at temperatures above 300℃ and begins to burn at temperatures above 500℃. Previously, the air intake pipes 6 were designated as pipe 1, pipe 2, and pipe 3, arranged in order of distance from the boiler inlet. Thermometers 1, 2, and 3 were installed on these pipes, respectively, with the thermometers positioned close to the feed pipe 3. When the temperature of feed pipe 3, as indicated by thermometer 1, rises to 300℃, there is a risk of lignin decomposition and combustion, potentially causing premature fuel combustion. The system determines whether premature fuel combustion has occurred based on sensor readings. If premature combustion is detected, the primary air volume in the corresponding primary air duct is increased to lower the temperature of feed pipe 3 and dilute the fuel.

[0037] When the pressure in feed pipe 3 reaches 0.3 MPa, the feed resistance in feed pipe 3 is reached when it is full of fuel, which may indicate fuel blockage in feed pipe 3. Based on the temperature and pressure sensor values ​​and the image recognition of online camera 11, it is determined whether feed pipe 3 is blocked. If feed pipe 3 is determined to be blocked (pressure greater than 0.3 MPa), air cannon 7 is activated to use high-pressure air to purge feed pipe 3 and increase the primary air volume to clear feed pipe 3 and reduce the pressure to below 0.1 MPa.

[0038] S3.2 Resolving Coking and Blockage Issues. In S3.1, if the pressure cannot be reduced, coking and blockage may occur in feed pipe 3. Controller 9 determines whether coking and blockage in feed pipe 3 is due based on sensor values. The determination method is as follows: If the temperature of feed pipe 3 reaches 600℃ and the pressure reaches 0.5 MPa, and the image from online camera 11 matches the characteristics of coking images, it is determined that feed pipe 3 is coking and blocked. Microwave source 8 is activated, selecting a more accurate single-mode microwave mode. Microwaves are radially delivered to feed pipe 3 via a single-mode microwave waveguide to heat the molten coke at the center of feed pipe 3. When the temperature of feed pipe 31 heated by microwave exceeds 800℃, it indicates that the coking has reached the coke melting temperature. Air cannon 7 is activated to purge feed pipe 3, and then the primary air volume is increased to remove the coke.

[0039] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined by the scope of the claims.

Claims

1. A cooling feed co-firing device for co-firing in large coal-fired boilers, characterized in that, include Crusher (1), and Feed pipe (3), the feed pipe (3) is connected to the side wall of the combustion furnace (10), and an air cannon (7) and a microwave source (8) are provided on the feed pipe (3). The air cannon (7) is located on the side of the microwave source (8) away from the combustion furnace (10). The main air intake pipe (5) is located on the outside of the side wall of the combustion furnace (10) and above the feed pipe (3). Multiple air intake branch pipes (6) are connected between the main air intake pipe (5) and the feed pipe (3). A connecting pipe (2) is connected between the crusher (1) and the feed pipe (3). The connecting pipe (2) is used to introduce cold flue gas into the feed pipe (3).

2. The cooling feed co-firing equipment for large coal-fired boilers according to claim 1, characterized in that, An observation hole is provided on the feed pipe (3), and an online camera (11) is provided at the observation hole. The online camera (11) is used to monitor the internal condition of the feed pipe (3).

3. The cooling feed co-firing equipment for large-scale coal-fired boilers according to claim 1, characterized in that, The feed pipe (3) is horizontally connected to the combustion furnace (10) at one end. The connecting pipe (2) is located below the feed pipe (3) and is parallel to the feed pipe (3). The end of the feed pipe (3) away from the combustion furnace (10) is bent downward.

4. The cooling feed co-firing equipment for large coal-fired boilers according to claim 3, characterized in that, The angle α at which the end of the feed pipe (3) away from the combustion furnace (10) bends downward is 10°~90°.

5. The cooling feed co-firing equipment for large coal-fired boilers according to claim 4, characterized in that, The angle α at which the end of the feed pipe (3) away from the combustion furnace (10) bends downward is 30°.

6. The cooling feed co-firing equipment for large coal-fired boilers according to claim 1, characterized in that, One-way valves (4) are connected to the connecting pipe (2), each air inlet branch pipe (6), and between the air cannon (7) and the feed pipe (3). A regulating valve (12) is provided on each air inlet branch pipe (6) and between the air cannon (7) and the feed pipe (3).

7. The cooling feed co-firing equipment for large coal-fired boilers according to claim 3, characterized in that, It also includes a sensor assembly and a controller (9). The sensor assembly includes a thermometer installed in each air inlet pipe (6), a temperature sensor, a pressure sensor, a wind speed sensor installed in the feed pipe (3), and an online camera (11) installed in the feed pipe (3). The controller (9) is connected to the crusher (1), the air cannon (7), the microwave source (8), the online camera (11), and the sensor assembly.

8. A method for co-firing cooling feedstock in large coal-fired boilers, characterized in that, include, Step 1: Introduce primary air into the main air inlet pipe (5). The temperature of the primary air should be below 40℃. Control the opening of the regulating valve (12) so that the air velocity of each air inlet branch pipe (6) reaches the set requirement. Step 2: Start the crusher (1) to crush the fuel into particles smaller than 50 micrometers. Then, introduce dried cold flue gas (temperature below 80℃, pressure 10-15kPa, flow rate 50-70m / s) into the connecting pipe (2). The cold flue gas carries the crushed fuel through the one-way valve (4), through the feed pipe (3), and mixes with the incoming air from the air inlet pipe (6) before entering the furnace for combustion. When the surface temperature of the feed pipe (3) is higher than 200°C, the primary air flow is increased by the regulating valve (12) on the air inlet branch pipe (6) so that the temperature of the feed pipe (3) remains below 200°C.

9. The cooling feed co-firing treatment method for large coal-fired boilers according to claim 8, characterized in that, During the feeding process, the temperature and pressure of the feed pipe (3) are monitored. When the pressure of the feed pipe (3) reaches 0.3 MPa, the air cannon (7) is started to blow the feed pipe (3) with high-pressure air and the primary air volume is increased to clear the feed pipe (3) and reduce the pressure to below 0.1 MPa.

10. The cooling feed co-firing treatment method for large coal-fired boilers according to claim 9, characterized in that, If the pressure of the feed pipe (3) cannot be reduced, when the temperature of the side of the feed pipe (3) near the combustion furnace (10) reaches 600°C and the pressure of the feed pipe (3) reaches 0.5 MPa, the image of the online camera (11) shows that there is coking inside the feed pipe (3). Start the microwave source (8) and transmit microwaves radially to the feed pipe (3) through the single-mode microwave waveguide to heat the melting coking in the center of the feed pipe (3). When the temperature of the side of the feed pipe (3) near the combustion furnace (10) is higher than 800°C, it indicates that the coking has reached the coking melting temperature. Start the air cannon (7) to purge the feed pipe (3) and then increase the primary air volume to remove the coking.

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