Biodiesel and coal blending combustion system and method

Abstract

The invention discloses a biodiesel and coal blending combustion system and method, and belongs to the technical field of clean energy comprehensive utilization and combustion optimization. The system comprises a biodiesel tank, an oil pump, a biodiesel impurity filter, a valve I, a flow meter I, a heater I, an air feeder, a valve II, a flow meter II, a heater II, a coal mill, a pulverized coal bunker, a feeder, a primary air fan, a pulverized coal mixer, a heater III, a pulverized coal burner, a biodiesel cyclone burner, a furnace body and a flue gas treatment device. By means of the system, biodiesel and coal can be mixed and combusted in the coal-fired boiler, the combustion efficiency of the coal-fired boiler can be remarkably improved by adjusting the mixing position and proportion of the biodiesel, and pollutant emission of the coal-fired boiler is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive utilization and combustion optimization of clean energy, and in particular relates to a biodiesel and coal mixed combustion system and method. Background Art

[0002] With the intensification of global climate change and increasingly severe environmental problems, the world is actively promoting green and low-carbon development. Coal-fired power plants, the backbone of power generation, are a major source of CO2 and other pollutant emissions. Low-carbon transformation of coal-fired power plants is imperative.

[0003] Biomass, as a near-zero-carbon fuel, is considered a coal alternative. However, existing technologies suffer from issues such as high-temperature corrosion, fouling, and slagging during the co-firing process. Currently, biodiesel is primarily used as a diesel engine fuel, with little application as a primary fuel or blend in coal-fired boilers. Its high oxygen content and low sulfur properties are not effectively utilized by coal-fired pollution control systems. However, biodiesel struggles to stably combine with hydrophobic pulverized coal, leading to stratification or localized enrichment, resulting in fluctuating combustion. Furthermore, the ignition characteristics of biodiesel and pulverized coal differ significantly, making flame deignition and delayed burnout a common problem when co-firing.

[0004] The invention patent "Preheating Biodiesel Burner" with application number 201010275806.3 uses high-temperature combustion air to preheat biodiesel to improve atomization quality. The mixing of biodiesel and air is not sufficient, and when the biodiesel blending ratio is low, the combustion is unstable.

[0005] The invention patent with application number 201810460509.2, "A biodiesel and 0# diesel mixed combustion system and method", uses a four-channel swirl burner to mix biodiesel, 0# diesel and air for combustion. It is limited to the mixed combustion of liquid fuels and cannot be applied to coal-fired units.

[0006] In order to promote the application of biodiesel in pulverized coal boilers, given the high cost and complexity of overall boiler transformation, how to successfully achieve the goal of stable blending of biodiesel in the boiler while minimizing the transformation cost is an urgent problem that needs to be solved. Summary of the Invention

[0007] To address the problems and shortcomings of existing technologies, the present invention provides a biodiesel and coal blending combustion system and method. This biodiesel and coal blending combustion system enables the blending and combustion of biodiesel and coal in a coal-fired boiler. Furthermore, by varying the biodiesel blending position and ratio, it can significantly improve the boiler's combustion efficiency and reduce pollutant emissions. The technical solutions of the present invention are as follows:

[0008] A biodiesel and coal blended combustion system includes: a pulverized coal conveying line, a biodiesel conveying line, an air conveying line, a biodiesel tank 1, a pulverized coal bin 8, a biodiesel swirl burner 17, a pulverized coal burner 18, a burner 21, and a furnace body 19. The biodiesel in the biodiesel tank 1 is conveyed to the burner 21 via the biodiesel conveying line, the pulverized coal in the pulverized coal bin 8 is conveyed to the burner 21 via the pulverized coal conveying line, and air is conveyed to the burner 21 via the air conveying line. The burners 21 are arranged at the four corners of the furnace body 19 to form tangential combustion. The burner 21 includes the pulverized coal burner 18 and the biodiesel swirl burner 17. The biodiesel swirl burner 17 is mounted in the middle of the pulverized coal burner 18, and the two form an integral unit. The furnace outlet of the furnace body 19 is connected to a flue gas treatment device 20.

[0009] The bottom of the burner 21 is connected to the up and down swing driving mechanism 22, which is arranged in the furnace body 19. The up and down swing driving mechanism 22 drives the burner 21 to swing up and down, and the up and down swing angle is ±20°;

[0010] The pulverized coal conveying line includes a coal mill 7, a pulverized coal bin 8, a feeder 9, a primary fan 10, a pulverized coal mixer 11, and a heater III 12. The coal mill 7, the pulverized coal bin 8, the feeder 9, the pulverized coal mixer 11, and the heater III 12 are connected in sequence. One side of the feeder 9 is connected to the primary fan 10. The burner 18 is provided with a pulverized coal outlet 24, and the heater III 12 is connected to the pulverized coal burner 18.

[0011] The biodiesel transmission line includes a biodiesel tank 1, an oil pump 2, a biodiesel impurity filter 3, a valve I4, a flowmeter I5, and a heater I6. The biodiesel tank 1, oil pump 2, biodiesel impurity filter 3, valve I4, flowmeter I5, and heater I6 are connected in sequence, and heater I6 is connected to burner 21. The biodiesel swirl burner 17 includes a biodiesel outlet 23, a biodiesel channel 27, and a primary air duct 26. The primary air duct 26 is connected to heater II16, and the biodiesel channel 27 is a double-helix swirl column. The biodiesel swirl burner 17 is manufactured using a double-helix swirl column with a length of 12 mm and a diameter of 9.5 mm. The burner design uses swirl studs to induce fuel to flow from the inlet to the cone chamber, thereby enhancing liquid flow turbulence, minimizing liquid retention in the burner, and significantly improving atomization efficiency. Even at lower pressures, the pressure swirl burner exhibits high atomization and combustion efficiency, thereby reducing energy consumption.

[0012] The air delivery circuit includes a blower 13, a valve II14, a flow meter II15, and a heater II16. The blower 13, the valve II14, the flow meter II15, and the heater II16 are connected in sequence. The heater II16 is connected to the burner 21. The air delivery circuit is connected to the air channel 25.

[0013] A method for burning a mixture of biodiesel and coal, characterized by comprising the following specific steps:

[0014] Step 1: After the biodiesel stored in the biodiesel tank 1 is pumped out by the oil pump 2, harmful impurities are filtered out by the biodiesel impurity filter 3, and then transported to the biodiesel swirl burner 17 through the valve I4, flow meter I5, and heater I6;

[0015] Step 2: The raw coal stored in the stockpile is fed into the pulverizer 7, where it is evaporated by hot air and crushed to the required mesh size. After passing through the pulverized coal bin 8, feeder 9 and primary fan 10, it is fully mixed with air in the pulverized coal mixer 11, heated by the heater III 12, and then fed to the pulverized coal burner 18.

[0016] Step 3: The air passes through the blower 13, valve II14, flow meter II15, and heater II16 in sequence and enters the air passages of the biodiesel swirl burner 17 and the pulverized coal burner 18 respectively;

[0017] Step 4: The plasma igniter first ignites the biodiesel coming out of the biodiesel swirl burner 17 to complete the ignition process, and then the pulverized coal is ignited at the outlet of the pulverized coal burner 18. At this time, the biodiesel and the pulverized coal are stably burned in the furnace at a set ratio, so that the biodiesel and coal are mixed and burned in the pulverized coal boiler. When the coal-fired unit is in a high-load operation state, the biodiesel mixing ratio is adjusted to be 0-20% of the total calorific value of the fuel, excluding 0% and 20%; when the coal-fired unit is in medium-load operation, the biodiesel mixing ratio is 20-25% of the total calorific value of the fuel, including 20%, excluding 25%; when the coal-fired unit is in low-load stable operation, the biodiesel mixing ratio is 25-30% of the total calorific value of the fuel, including 25% and 30%;

[0018] Furthermore, heater I6 heats the biodiesel to a preset temperature, set at 60-80°C; heater II16 heats the air to a preset temperature, set at 135°C; heater III12 heats the pulverized coal particles to a preset temperature, set at 70-120°C;

[0019] The blower 13 provides the air required for combustion. On the one hand, it provides air for the biodiesel swirl burner 17 for atomization. On the other hand, it provides combustion-supporting substances for the combustion of biodiesel and coal powder, and controls the excess air coefficient at 1.15 to ensure complete combustion of the fuel in the furnace.

[0020] Furthermore, the control strategy for blended combustion is as follows: The control of blended combustion of biodiesel and coal is based on the core mechanism of "thermodynamic matching - oxygen transport synergy - pollutant suppression", aiming to achieve maximum thermal efficiency, minimum emissions and wide load adaptability, including:

[0021] Dynamic optimization of fuel ratio and calorific value balance model:

[0022]

[0023] Where Qtarget is the preset mixed fuel calorific value of 24.69MJ / kg, Qcoal = 19.68MJ / kg, QBD = 39.73MJ / kg;

[0024] Intelligent optimization model construction, multi-objective optimization function:

[0025]

[0026] Constraints:

[0027]

[0028] (Weight coefficients: α = 0.4, β = 0.35, γ = 0.25);

[0029] Where, η represents the combustion efficiency; NO x,std Indicates NO x The standard limit of emission, used for normalization; ΔT max Indicates the maximum temperature fluctuation in the furnace; T wall Indicates the upper limit of furnace wall temperature; τ comb Indicates the lower limit of the fuel's residence time in the furnace;

[0030] Digital Twin Prediction System: Using a particle swarm optimization algorithm, it analyzes and processes real-time data such as flame images, O2 concentration distribution, and NOx concentration and temperature at the furnace outlet. This intelligently controls the biodiesel blending position and ratio, ensuring high-efficiency and stable boiler combustion while significantly reducing pollutant emissions and achieving energy conservation and carbon reduction.

[0031] The beneficial effects of the present invention are:

[0032] 1. The system significantly reduces carbon emissions from coal-fired units by mixing biodiesel with coal for combustion.

[0033] 2. The system can adjust the biodiesel blending position and proportion, and dynamically adjust the biodiesel blending position from layer A to layer E and the biodiesel blending proportion from 0 to 30% according to the combustion status in the furnace, thereby optimizing the combustion effect in the furnace, improving the combustion efficiency of the coal-fired unit, and responding to the changes in combustion conditions caused by peak regulation, thereby achieving the effect of promoting low-load stable combustion of the coal-fired unit.

[0034] 3. The present invention adopts a low-cost modification scheme to carry out targeted optimization of the pulverized coal burner and integrate the biodiesel nozzle into the core area of the burner. This scheme realizes the efficient synergistic combustion of biodiesel and pulverized coal through the precise layout of the nozzle structure, and successfully achieves the goal of stable blending of biodiesel in the boiler while minimizing the modification cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic diagram of the system structure of Example 1 of the present invention;

[0036] Figure 2 1 is a schematic plan view of a fuel outlet of a burner according to embodiment 1 of the present invention;

[0037] Figure 3 1 is a perspective structural diagram of a burner according to embodiment 1 of the present invention;

[0038] Figure 4 Schematic diagram of the swing angle and structure of the burner in Example 1 of the present invention;

[0039] Figure 5 is a schematic cross-sectional view of a burner according to embodiment 1 of the present invention;

[0040] Figure 6 Schematic diagram of the structure of the biodiesel swirl burner according to Example 1 of the present invention; wherein part a is a three-dimensional schematic diagram; part b is a side view;

[0041] In the figure: 1-biodiesel tank, 2-oil pump, 3-biodiesel impurity filter, 4-valve I, 5-flow meter I, 6-heater I, 7-pulverized coal silo, 8-pulverized coal bin, 9-feeder, 10-primary fan, 11-pulverized coal mixer, 12-heater III, 13-air blower, 14-valve II, 15-flow meter II, 16-heater II, 17-biodiesel swirl burner, 18-pulverized coal burner, 19-furnace body, 20-flue gas treatment device, 21-burner, 22-up and down swing drive mechanism, 23-biodiesel outlet, 24-pulverized coal outlet, 25-air channel, 26-primary air duct, 27-biodiesel channel. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0043] Example 1

[0044] A biodiesel and coal mixed combustion system, such as Figure 1 、 2, 3, 4, 5, 6a and 6b, comprising: a pulverized coal conveying line, a biodiesel conveying line, an air conveying line, a biodiesel tank 1, a pulverized coal bin 8, a biodiesel swirl burner 17, a pulverized coal burner 18, a burner 21, and a furnace body 19; the biodiesel in the biodiesel tank 1 is conveyed to the burner 21 through the biodiesel conveying line, the pulverized coal in the pulverized coal bin 8 is conveyed to the burner 21 through the pulverized coal conveying line, and the air is conveyed to the burner 21 through the air conveying line; the burner 21 is arranged at the four corners of the furnace body 19 to form tangential combustion; the burner 21 comprises a pulverized coal burner 18 and a biodiesel swirl burner 17, the biodiesel swirl burner 17 is installed in the middle of the pulverized coal burner 18, and the two form a whole, and the furnace outlet of the furnace body 19 is connected to the flue gas treatment device 20;

[0045] The bottom of the burner 21 is connected to the up-and-down swing drive mechanism 22, which is arranged in the furnace body 19. The up-and-down swing drive mechanism 22 drives the burner 21 to swing up and down, and the up-and-down swing angle is ±20°; in the present invention, the up-and-down swing drive mechanism 22 is a conventional telescopic mechanism, including: an electric push rod, a hydraulic push rod, etc.

[0046] The pulverized coal conveying line includes a coal mill 7, a pulverized coal bin 8, a feeder 9, a primary fan 10, a pulverized coal mixer 11, and a heater III 12. The coal mill 7, the pulverized coal bin 8, the feeder 9, the pulverized coal mixer 11, and the heater III 12 are connected in sequence. One side of the feeder 9 is connected to the primary fan 10. The burner 18 is provided with a pulverized coal outlet 24, and the heater III 12 is connected to the pulverized coal burner 18.

[0047] The biodiesel transmission line includes a biodiesel tank 1, an oil pump 2, a biodiesel impurity filter 3, a valve I4, a flowmeter I5, and a heater I6. The biodiesel tank 1, oil pump 2, biodiesel impurity filter 3, valve I4, flowmeter I5, and heater I6 are connected in sequence, and heater I6 is connected to burner 21. The biodiesel swirl burner 17 includes a biodiesel outlet 23, a biodiesel channel 27, and a primary air duct 26. The primary air duct 26 is connected to heater II16, and the biodiesel channel 27 is a double-helix swirl column. The biodiesel swirl burner 17 is manufactured using a double-helix swirl column with a length of 12 mm and a diameter of 9.5 mm. The burner design uses swirl studs to induce fuel to flow from the inlet to the cone chamber, thereby enhancing liquid flow turbulence, minimizing liquid retention in the burner, and significantly improving atomization efficiency. Even at lower pressures, the pressure swirl burner exhibits high atomization and combustion efficiency, thereby reducing energy consumption.

[0048] The air delivery circuit includes a blower 13, a valve II14, a flow meter II15, and a heater II16. The blower 13, the valve II14, the flow meter II15, and the heater II16 are connected in sequence. The heater II16 is connected to the burner 21. The air delivery circuit is connected to the air channel 25.

[0049] In this embodiment, the boiler has a total of five layers of pulverized coal burners 18, including: A, B, C, D, and E. Under rated operating conditions, four layers of burners can meet the load. A biodiesel swirl burner 17 is installed in the middle of the pulverized coal burners 18. The pulverized coal burner 18 on the A layer is deactivated, and the middle biodiesel swirl burner 17 is used. The pulverized coal burners 18 on the C, D, and E layers continue to use the pulverized coal burners 18. Biodiesel and pulverized coal are fed into the furnace at a calorific value ratio of 1:4 through the feeder 7 and the flow meter 15.

[0050] A method for burning a mixture of biodiesel and coal, characterized by comprising the following specific steps:

[0051] Step 1: After the biodiesel stored in the biodiesel tank 1 is pumped out by the oil pump 2, harmful impurities are filtered out by the biodiesel impurity filter 3, and then transported to the biodiesel swirl burner 17 through the valve I4, flow meter I5, and heater I6;

[0052] Step 2: The raw coal stored in the stockpile is fed into the pulverizer 7, where it is evaporated by hot air and crushed to the required mesh size. After passing through the pulverized coal bin 8, feeder 9 and primary fan 10, it is fully mixed with air in the pulverized coal mixer 11, heated by the heater III 12, and then fed to the pulverized coal burner 18.

[0053] Step 3: The air passes through the blower 13, valve II14, flow meter II15, and heater II16 in sequence and enters the air passages of the biodiesel swirl burner 17 and the pulverized coal burner 18 respectively;

[0054] Step 4: The plasma igniter first ignites the biodiesel coming out of the biodiesel swirl burner 17 to complete the ignition process, and then the pulverized coal is ignited at the outlet of the pulverized coal burner 18. At this time, the biodiesel and the pulverized coal are stably burned in the furnace at a set ratio, so that the biodiesel and coal are mixed and burned in the pulverized coal boiler, wherein the proportion of biodiesel mixed combustion is adjusted to 0-20% of the total calorific value of the fuel when the coal-fired unit is in a high-load operation state, excluding 0% and 20%. In this embodiment, 5%, 15% and 19% are taken to suppress the risk of slagging; when the coal-fired unit is in medium load operation, the biodiesel blending ratio is 20-25% of the total calorific value of the fuel, including 20%, excluding 25%, which can optimize thermal efficiency; when the coal-fired unit is in low-load stable operation, the biodiesel blending ratio is 25-30% of the total calorific value of the fuel, including 25% and 30%, which can prevent deignition and instability;

[0055] Furthermore, heater I6 heats the biodiesel to a preset temperature of 60 to 80°C. In this embodiment, 60°C, 75°C, and 80°C are used. Heater II16 heats the air to a preset temperature of 135°C. Heater III12 heats the pulverized coal particles to a preset temperature of 70 to 120°C. In this embodiment, 70°C, 100°C, and 120°C are used.

[0056] Furthermore, the control strategy for blended combustion is as follows: The control of blended combustion of biodiesel and coal is based on the core mechanism of "thermodynamic matching - oxygen transport synergy - pollutant suppression", aiming to achieve maximum thermal efficiency, minimum emissions and wide load adaptability, including:

[0057] Dynamic optimization of fuel ratio and calorific value balance model:

[0058]

[0059] Where Qtarget is the preset mixed fuel calorific value of 24.69MJ / kg, Qcoal = 19.68MJ / kg, QBD = 39.73MJ / kg;

[0060] Intelligent optimization model construction, multi-objective optimization function:

[0061]

[0062] Constraints:

[0063]

[0064] (Weight coefficients: α = 0.4, β = 0.35, γ = 0.25);

[0065] Where, η represents the combustion efficiency; NO x,std Indicates NO x The standard limit of emission, used for normalization; ΔT max Indicates the maximum temperature fluctuation in the furnace; T wall Indicates the upper limit of furnace wall temperature; τ comb Indicates the lower limit of the fuel's residence time in the furnace;

[0066] Digital Twin Prediction System: Using a particle swarm optimization algorithm, it analyzes and processes real-time data such as flame images, O2 concentration distribution, and NOx concentration and temperature at the furnace outlet. This intelligently controls the biodiesel blending position and ratio, ensuring high-efficiency and stable boiler combustion while significantly reducing pollutant emissions and achieving energy conservation and carbon reduction.

[0067] Example 2

[0068] This embodiment is similar to embodiment 1, except that a biodiesel and coal mixed combustion system is used. The structural components are different from those of embodiment 1 in that: the pulverized coal burner 18 on the B layer is deactivated and the biodiesel swirl burner 17 is used, while the pulverized coal burner 18 is still used on the C, D, and E layers. The other steps are the same as those of embodiment 1.

[0069] Example 3

[0070] This embodiment is similar to embodiment 1, except that a biodiesel and coal mixed combustion system is used. The structural components are different from those of embodiment 1 in that: the pulverized coal burner 18 of the C layer is deactivated and the biodiesel swirl burner 17 is used, and the pulverized coal burner 18 is still used on the B, D, and E layers. The other steps are the same as those of embodiment 1.

[0071] Example 4

[0072] This embodiment is similar to embodiment 1, except that a biodiesel and coal mixed combustion system is used. The structural components are different from those of embodiment 1 in that: the pulverized coal burner 18 on the D layer is deactivated and the biodiesel swirl burner 17 is used, while the pulverized coal burner 18 is still used on the B, C, and E layers. The other steps are the same as those of embodiment 1.

[0073] Example 5

[0074] This embodiment is similar to embodiment 1, except that a biodiesel and coal mixed combustion system is used. The structural components are different from those of embodiment 1 in that: the E layer pulverized coal burner 18 is deactivated and the biodiesel swirl burner 17 is used, and the B, C, and D layers still use the pulverized coal burner 18. The other steps are the same as those of embodiment 1.

[0075] Example 6

[0076] This embodiment is similar to Example 1, except that it is a biodiesel and coal mixed combustion system. The structural components and operating operations are different from those of Example 5 in that: the E-layer pulverized coal burner 18 is deactivated and a biodiesel swirl burner 17 is used; the A, B, C, and D layers use pulverized coal burners 18; biodiesel is fed into the furnace with pulverized coal at 5% of the total calorific value of the fuel through the feeder 7 and the flow meter 15; the other steps are the same as those of Example 1.

[0077] The above describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

[0078] The above is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the scope of protection of the present invention.

Claims

1. A biodiesel and coal mixed combustion system, characterized by: The invention comprises a pulverized coal conveying line, a biodiesel conveying line, an air conveying line, a biodiesel tank (1), a pulverized coal bin (8), a biodiesel swirl burner (17), a pulverized coal burner (18), a burner (21), and a furnace body (19). The biodiesel in the biodiesel tank (1) is conveyed to the burner (21) through the biodiesel conveying line, the pulverized coal in the pulverized coal bin (8) is conveyed to the burner (21) through the pulverized coal conveying line, and air is conveyed to the burner (21) through the air conveying line. The burner (21) is arranged at the four corners of the furnace body (19) to form tangential combustion. The burner (21) comprises a pulverized coal burner (18) and a biodiesel swirl burner (17). The biodiesel swirl burner (17) is arranged in the middle of the pulverized coal burner (18). The two form an integral whole. The furnace outlet of the furnace body (19) is connected to a flue gas treatment device (20).

2. The biodiesel and coal mixed combustion system according to claim 1, characterized in that: The pulverized coal conveying line comprises a coal mill (7), a pulverized coal bin (8), a feeder (9), a primary fan (10), a pulverized coal mixer (11), and a heater III (12). The coal mill (7), the pulverized coal bin (8), the feeder (9), the pulverized coal mixer (11), and the heater III (12) are connected in sequence, and one side of the feeder (9) is connected to the primary fan (10).

3. The biodiesel and coal mixed combustion system according to claim 1, characterized in that: The biodiesel transmission line comprises a biodiesel tank (1), an oil pump (2), a biodiesel impurity filter (3), a valve 1 (4), a flow meter 1 (5), and a heater 1 (6). The biodiesel tank (1), the oil pump (2), the biodiesel impurity filter (3), the valve 1 (4), the flow meter 1 (5), and the heater 1 (6) are connected in sequence, and the heater 1 (6) is communicated with a burner (21).

4. The biodiesel and coal mixed combustion system according to claim 1, characterized in that: The air delivery circuit comprises an air blower (13), a valve II (14), a flow meter II (15), and a heater II (16). The air blower (13), the valve II (14), the flow meter II (15), and the heater II (16) are connected in sequence, and the heater II (16) is communicated with the burner (21).

5. The biodiesel and coal mixed combustion system according to claim 1, characterized in that: The biodiesel swirl burner (17) comprises a biodiesel outlet (23), a biodiesel channel (27), and a primary air channel (26), wherein the primary air channel (26) is connected to the heater II (16), and the biodiesel channel (27) is a double helical vortex column; The pulverized coal burner (18) is provided with a pulverized coal outlet (24); The air delivery line is in communication with the air channel (25).

6. The biodiesel and coal mixed combustion system according to claim 1, characterized in that: The bottom of the burner (21) is connected to an up-and-down swing driving mechanism (22), which is arranged in the furnace body (19) and drives the burner (21) to swing up and down.

7. A method for burning a mixture of biodiesel and coal, characterized in that: The specific steps are as follows: Step 1: After the biodiesel stored in the biodiesel tank (1) is pumped out by the oil pump (2), harmful impurities therein are filtered out by the biodiesel impurity filter (3), and then the biodiesel is transported to the biodiesel swirl burner (17) through the valve I (4), the flow meter I (5), and the heater I (6); Step 2: The raw coal stored in the stockpile is fed into the coal mill (7), where it is evaporated by hot air and crushed to the required mesh size. After passing through the pulverized coal bin (8), feeder (9) and primary fan (10), it is fully mixed with air in the pulverized coal mixer (11), heated by the heater III (12), and then fed to the pulverized coal burner (18). Step 3: The air is passed through the air blower (13), valve II (14), flow meter II (15), and heater II (16) and then into the air passages of the biodiesel swirl burner (17) and the pulverized coal burner (18). Step 4: The plasma igniter first ignites the biodiesel coming out of the biodiesel swirl burner (17), completing the ignition process. Then, the pulverized coal is ignited at the outlet of the pulverized coal burner (18). At this time, the biodiesel and pulverized coal are stably burned in the furnace at a set ratio, realizing the mixed combustion of biodiesel and coal in the pulverized coal boiler.

8. The method for burning biodiesel and coal blends according to claim 7, characterized in that: The plasma igniter first ignites the biodiesel coming out of the biodiesel swirl burner (17) to complete the ignition process, and then the coal powder is ignited at the outlet of the coal powder burner (18). At this time, the biodiesel and the coal powder are stably burned in the furnace at a set ratio, realizing the mixed combustion of biodiesel and coal in the coal powder boiler. The ratio of biodiesel mixed combustion is when the coal-fired unit includes: high load operation state, medium load operation state and low load operation state.

9. The biodiesel and coal mixed combustion method according to claim 7, characterized in that: Heater I (6) heats the biodiesel to a preset temperature; heater II (16) heats the air to a preset temperature; and heater III (12) heats the pulverized coal particles to a preset temperature.

10. The method for burning biodiesel and coal blends according to claim 7, characterized in that: The excess air coefficient of the mixed combustion is 1.15.

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