Boiler low-load stable combustion system with double-layer plasma ignition device and control method

Abstract

The invention discloses a boiler low-load stable combustion system with a double-layer plasma ignition device and a control method. 10KV or 6KV high-voltage electricity provided by a medium-voltage bus is reduced to 400V through a transformer to supply power to a rectification power supply cabinet and a control cabinet; the rectification power supply cabinet provides direct current needed by arc discharge for the A-layer plasma ignition device and the B-layer plasma ignition device, and the control cabinet provides control signals for the A-layer plasma ignition device and the B-layer plasma ignition device. When the A-layer plasma ignition device control power switch and the A-layer plasma ignition device power switch are switched on, the direct current and the control signal are correspondingly input into the A-layer plasma ignition device; and when the B-layer plasma ignition device control power switch and the B-layer plasma ignition device power switch are switched on, the direct current and the control signal are correspondingly input into the B-layer plasma ignition device. The low load of the boiler is achieved with low transformation cost, the operation mode in the start-stop process is flexible and changeable, and the boiler is suitable for different conditions.

Description

Technical Field

[0001] This invention relates to a boiler low-load stable combustion system and control method with a double-layer plasma ignition device, belonging to the field of boiler ignition for coal-fired power generation units. Background Technology

[0002] Currently, most units using plasma ignition technology only have one layer of plasma burners. During startup and commissioning, failures in some plasma igniters often prevent normal plasma ignition startup. Even after successful startup, the second pulverizing system can only be put into operation after the primary air temperature reaches a certain level, restricting the load increase rate and wasting energy. With the increasing demands of the power grid for deep peak-shaving capabilities, thermal power units need to have stronger load regulation capabilities, placing higher demands on the unit's stable combustion capability under low load. If the single-layer plasma ignition device configured in conventional boilers malfunctions, or if the single-layer burner or single coal mill corresponding to the single-layer plasma ignition device malfunctions, the stable combustion capability under low load is lost. Summary of the Invention

[0003] This invention provides a boiler low-load stable combustion system and control method with a double-layer plasma ignition device, which solves the problems disclosed in the background art.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A boiler low-load stable combustion system with a dual-layer plasma ignition device includes: a medium-voltage busbar, a transformer, a rectifier power supply cabinet, a control cabinet, an A-layer plasma ignition device, a B-layer plasma ignition device, a control power switch for the A-layer plasma ignition device, a control power switch for the B-layer plasma ignition device, a power switch for the A-layer plasma ignition device, and a power switch for the B-layer plasma ignition device. The medium-voltage busbar is connected to the rectifier power supply cabinet via the transformer, and the control cabinet is connected to the rectifier power supply cabinet. The A-layer plasma ignition device is connected to the control cabinet via the A-layer plasma ignition device control power switch and to the rectifier power supply cabinet via the A-layer plasma ignition device power switch. The B-layer plasma ignition device is connected to the control cabinet via the B-layer plasma ignition device control power switch and to the rectifier power supply cabinet via the B-layer plasma ignition device power switch.

[0005] Furthermore, an automatic switching device is provided between the A-layer plasma ignition device and the B-layer plasma ignition device. The automatic switching device is used to automatically switch to the other plasma ignition device when either the A-layer plasma ignition device or the B-layer plasma ignition device malfunctions.

[0006] Furthermore, an interlocking protection module is provided between the A-layer plasma ignition device and the B-layer plasma ignition device. The interlocking protection module is used to allow only one of the A-layer plasma ignition device and the B-layer plasma ignition device to be activated.

[0007] Furthermore, it also includes a DCS remote control module, which is used to remotely control the power switch and power supply switch of the A-layer plasma ignition device or the power switch and power supply switch of the B-layer plasma ignition device.

[0008] Accordingly, the control method of the boiler low-load stable combustion system with dual-layer plasma ignition device is as follows: the 10KV or 6KV high voltage power supplied by the medium voltage bus is stepped down to 400V by the transformer to power the rectifier power supply cabinet and the control cabinet. The rectifier power supply cabinet provides the DC power required for arcing of the A-layer plasma ignition device and the B-layer plasma ignition device, and the control cabinet provides control signals for the A-layer plasma ignition device and the B-layer plasma ignition device. When the control power switch and the power power switch of the A-layer plasma ignition device are closed, DC power and control signals are supplied to the A-layer plasma ignition device accordingly. When the control power switch and the power power switch of the B-layer plasma ignition device are closed, DC power and control signals are supplied to the B-layer plasma ignition device accordingly.

[0009] Accordingly, the control method for the boiler low-load stable combustion system with dual-layer plasma ignition device is as follows: when the unit is running normally, if one of the 8-corner or 4-corner plasma devices in the A-layer plasma ignition device or the B-layer plasma ignition device fails, the system will automatically switch to the corresponding corner of the other plasma ignition device.

[0010] Accordingly, the control method for the boiler low-load stable combustion system with dual-layer plasma ignition device is as follows: only one of the A-layer plasma ignition device control power switch and the B-layer plasma ignition device control power switch can be closed, and only one of the A-layer plasma ignition device power switch and the B-layer plasma ignition device power switch can be closed.

[0011] Accordingly, the control method for the boiler low-load stable combustion system with dual-layer plasma ignition device is as follows: if the control power switch of the A-layer plasma ignition device under the control cabinet is closed, the power switch of the B-layer plasma ignition device under the rectifier power cabinet cannot be closed. If the control power switch of the plasma ignition device on layer B under the control cabinet is closed, the power switch of the plasma ignition device on layer A under the rectifier power cabinet cannot be closed. If the power switch of the plasma ignition device on layer B under the rectifier power supply cabinet is closed, the control power switch of the plasma ignition device on layer A under the control cabinet cannot be closed. If the power switch for the plasma ignition device on layer A under the rectifier power supply cabinet is closed, the control power switch for the plasma ignition device on layer B under the control cabinet will not be closed.

[0012] Accordingly, the control method for the boiler low-load stable combustion system with dual-layer plasma ignition device is as follows: when the DCS remote control module selects the A-layer plasma ignition mode, the B-layer plasma ignition device control power switch and the B-layer plasma ignition device power switch are automatically disconnected, and then the A-layer plasma ignition device control power switch and the A-layer plasma ignition device power switch are automatically closed.

[0013] Accordingly, the control method for the boiler low-load stable combustion system with dual-layer plasma ignition device is as follows: when the DCS remote control module selects the B-layer plasma ignition mode, the A-layer plasma ignition device control power switch and the A-layer plasma ignition device power switch are automatically disconnected, and then the B-layer plasma ignition device control power switch and the B-layer plasma ignition device power switch are automatically closed.

[0014] The beneficial effects achieved by this invention are as follows: This invention can be modified based on existing single-layer plasma ignition devices. In addition to the conventional A-layer plasma ignition device in a boiler, a B-layer plasma ignition device is added as a backup. Four new switches are added for switching: a control power switch for the A-layer plasma ignition device, a control power switch for the B-layer plasma ignition device, and a power power switch for the A-layer plasma ignition device and the B-layer plasma ignition device. This allows for flexible and adaptable boiler operation during low loads and start-up / shutdown processes at a relatively low modification cost. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention.

[0016] Figure label: 1-Medium voltage busbar, 2-Transformer, 3-Rectifier power supply cabinet, 4-Control cabinet, 5-A-layer plasma ignition device, 6-B-layer plasma ignition device, 7-A-layer plasma ignition device control power switch, 8-B-layer plasma ignition device control power switch, 9-A-layer plasma ignition device power switch, 10-B-layer plasma ignition device power switch. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention. Example 1

[0018] like Figure 1 As shown, this embodiment provides a boiler low-load stable combustion system with a dual-layer plasma ignition device, including: a medium-voltage busbar 1, a transformer 2, a rectifier power supply cabinet 3, a control cabinet 4, an A-layer plasma ignition device 5, a B-layer plasma ignition device 6, an A-layer plasma ignition device control power switch 7, a B-layer plasma ignition device control power switch 8, an A-layer plasma ignition device power switch 9, and a B-layer plasma ignition device power switch 10; the medium-voltage busbar 1 is connected to the rectifier power supply cabinet 3 via the transformer 2, and the control cabinet 4 is connected to the rectifier power supply cabinet 3; the A-layer plasma ignition device 5 is connected to the control cabinet 4 via the A-layer plasma ignition device control power switch 7, and is connected to the rectifier power supply cabinet 3 via the A-layer plasma ignition device power switch 9; the B-layer plasma ignition device 6 is connected to the control cabinet 4 via the B-layer plasma ignition device control power switch 8, and is connected to the rectifier power supply cabinet 3 via the B-layer plasma ignition device power switch 10. The control cables from control cabinet 4 to plasma ignition device 5 (layer A) and from control cabinet 4 to plasma ignition device 6 (layer B) are connected from control cabinet 4 at different locations. The power cables from rectifier power supply cabinet 3 to plasma ignition device 5 (layer A) and from rectifier power supply cabinet 3 to plasma ignition device 6 (layer B) are connected from rectifier power supply cabinet 3 at different locations.

[0019] The 10KV or 6KV high-voltage electricity provided by the medium-voltage busbar 1 is stepped down to 400V by the transformer 2 to power the rectifier power supply cabinet 3 and the control cabinet 4. The rectifier power supply cabinet 3 provides the DC power required for arcing of the A-layer plasma ignition device 5 and the B-layer plasma ignition device 6. The control cabinet 3 provides control signals to the A-layer plasma ignition device 5 and the B-layer plasma ignition device 6. A total of four switches are used for switching: A-layer plasma ignition device control power switch 7, B-layer plasma ignition device control power switch 8, A-layer plasma ignition device power power switch 9, and B-layer plasma ignition device power power switch 10.

[0020] The plasma ignition device mainly consists of the following parts: The plasma generator produces air plasma with an electrical power of 50kW to 150kW.

[0021] An ignition burner, used in conjunction with a plasma generator, to ignite and burn pulverized coal.

[0022] The auxiliary system consists of a cooling water supply system and an air supply system.

[0023] The plasma ignition device utilizes a direct current (greater than 200 A) to initiate an arc under a medium pressure greater than 0.1 MPa, and obtains a stable power direct current air plasma under a strong magnetic field. This plasma forms a localized high-temperature zone with a temperature greater than 5000 K in the primary combustion chamber of the burner. When pulverized coal particles pass through this plasma "fire core," they are subjected to high temperatures, releasing volatiles within 0.001 s, causing the pulverized coal particles to break down and accelerate combustion. Because this reaction occurs in the gas phase, it alters the particle size distribution of the mixture, increasing the ignition rate of the pulverized coal and further accelerating its combustion. Thus, the plasma ignition system significantly reduces the ignition energy E required for pulverized coal combustion.

[0024] Plasma contains a large number of chemically active particles, which can accelerate thermochemical conversion and promote complete combustion of fuel. In addition, under the action of plasma, pulverized coal can increase its volatile matter content by 20% to 80% compared with normal conditions. That is, plasma has the effect of regenerating volatile matter, which is of particular significance for igniting lean coal and enhancing combustion.

[0025] The plasma generator is a magnetically stabilized air-carrier plasma generator, consisting of a coil, cathode, and anode. The cathode is made of a high-conductivity metallic or non-metallic material, while the anode is made of a high-conductivity, high-thermal-conductivity, and oxidation-resistant metallic material. Both the cathode and anode are water-cooled to reduce the impact of high-temperature electric arcs. The plasma generator coil has the ability to withstand a 2000V DC voltage breakdown at 250℃, and the power supply uses full-wave rectification and has constant current performance.

[0026] The ignition process of a plasma generator is as follows: (1) Set the output current. (2) The cathode advances and contacts the anode, and the entire system has short-circuit resistance and maintains a constant current. (3) The cathode slowly leaves the anode, and the electric arc is pulled out of the nozzle under the action of the coil's magnetic force; (4) Air at a pressure of about 0.03 MPa is ionized into high-temperature plasma under the action of electric arc, with an energy density as high as 105 W / cm2 to 106 W / cm2, which creates favorable conditions for igniting different types of coal. Example 2

[0027] This embodiment provides a control method for a boiler low-load stable combustion system with a dual-layer plasma ignition device, including the following steps: During unit startup, the use of either the A-layer plasma ignition device or the B-layer plasma ignition device can be selected via four switches: A-layer plasma ignition device control power switch 7, B-layer plasma ignition device control power switch 8, A-layer plasma ignition device power switch 9, and B-layer plasma ignition device power switch 10. When A-layer plasma ignition device control power switch 7 and A-layer plasma ignition device power switch 9 are closed, A-layer plasma ignition device 5 is activated. When B-layer plasma ignition device control power switch 8 and B-layer plasma ignition device power switch 10 are closed, B-layer plasma ignition device 6 is activated.

[0028] If the plasma device needs to be put into operation for stable combustion during normal operation of the unit, the A-layer plasma ignition device 5 or the B-layer plasma ignition device 6 can be selected as needed.

[0029] If the plasma ignition device 5 (layer A) or plasma ignition device 6 (layer B) is already in operation during normal operation of the unit, and one of the 8-corner or 4-corner plasma devices malfunctions, it can automatically switch to the corresponding corner of the other plasma ignition device. First, disconnect the control power switch and the power switch of the current plasma ignition device, and then close the control power switch and the power switch of the other plasma ignition device.

[0030] Interlocking protection function: The A-layer plasma ignition device control power switch 7 and the B-layer plasma ignition device control power switch 8 are interlocked, allowing only one of them to be selected. The A-layer plasma ignition device power switch 9 and the B-layer plasma ignition device power switch 10 are also interlocked, allowing only one of them to be selected. Furthermore, the A-layer plasma ignition device control power switches 7 and 8 under control cabinet 4 are also interlocked with the A-layer plasma ignition device power switches 9 and 10 under rectifier power cabinet 3. If the A-layer plasma ignition device control power switch 7 under control cabinet 4 is closed, the B-layer plasma ignition device power switch 10 under rectifier power cabinet 3 cannot be closed. If the B-layer plasma ignition device control power switch 8 under control cabinet 4 is closed, the A-layer plasma ignition device power switch 9 under rectifier power cabinet 3 cannot be closed. If the power switch 10 of the plasma ignition device in layer B under rectifier power cabinet 3 is closed, the control power switch 7 of the plasma ignition device in layer A under control cabinet 4 cannot be closed. If the power switch 9 of the plasma ignition device in layer A under rectifier power cabinet 3 is closed, the control power switch 8 of the plasma ignition device in layer B under control cabinet 4 cannot be closed.

[0031] The A-layer plasma ignition device control power switch 7, B-layer plasma ignition device control power switch 8, A-layer plasma ignition device power switch 9, and B-layer plasma ignition device power switch 10 are controlled by a remote DCS control module. When the remote DCS selects the A-layer plasma ignition mode, the B-layer plasma ignition device control power switch 8 and the B-layer plasma ignition device power switch 10 automatically open, and then the A-layer plasma ignition device control power switch 7 and the A-layer plasma ignition device power switch 9 automatically close. When the remote DCS selects the B-layer plasma ignition mode, the A-layer plasma ignition device control power switch 7 and the A-layer plasma ignition device power switch 9 automatically open, and then the B-layer plasma ignition device control power switch 8 and the B-layer plasma ignition device power switch 10 automatically close.

[0032] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A boiler low-load stable combustion system with a double-layer plasma ignition device, characterized in that, include: Medium-voltage busbar (1), transformer (2), rectifier power supply cabinet (3), control cabinet (4), A-layer plasma ignition device (5), B-layer plasma ignition device (6), A-layer plasma ignition device control power switch (7), B-layer plasma ignition device control power switch (8), A-layer plasma ignition device power switch (9) and B-layer plasma ignition device power switch (10); the medium-voltage busbar (1) is connected to the rectifier power supply cabinet (3) through the transformer (2), and the control cabinet (4) is connected to the rectifier power supply cabinet (3); the A-layer plasma ignition device (5) is connected to the control cabinet (4) through the A-layer plasma ignition device control power switch (7), and is connected to the rectifier power supply cabinet (3) through the A-layer plasma ignition device power switch (9); the B-layer plasma ignition device (6) is connected to the control cabinet (4) through the B-layer plasma ignition device control power switch (8), and is connected to the rectifier power supply cabinet (3) through the B-layer plasma ignition device power switch (10).

2. The boiler low-load stable combustion system with a double-layer plasma ignition device according to claim 1, characterized in that, An automatic switching device is provided between the A-layer plasma ignition device (5) and the B-layer plasma ignition device (6). The automatic switching device is used to automatically switch to the other plasma ignition device when either the A-layer plasma ignition device (5) or the B-layer plasma ignition device (6) malfunctions.

3. The boiler low-load stable combustion system with a double-layer plasma ignition device according to claim 1, characterized in that, An interlocking protection module is provided between the A-layer plasma ignition device (5) and the B-layer plasma ignition device (6). The interlocking protection module is used to allow only one of the A-layer plasma ignition device (5) and the B-layer plasma ignition device (6) to be activated.

4. The boiler low-load stable combustion system with a double-layer plasma ignition device according to claim 1, characterized in that, It also includes a DCS remote control module, which is used to remotely control the A-layer plasma ignition device control power switch (7) and the A-layer plasma ignition device power switch (9) or the B-layer plasma ignition device control power switch (8) and the B-layer plasma ignition device power switch (10).

5. The control method for a boiler low-load stable combustion system with a double-layer plasma ignition device according to claim 1, characterized in that: The 10KV or 6KV high voltage provided by the medium voltage bus (1) is stepped down to 400V by the transformer (2) to power the rectifier power supply cabinet (3) and the control cabinet (4). The rectifier power supply cabinet (3) provides the DC power required for arcing of the A-layer plasma ignition device (5) and the B-layer plasma ignition device (6). The control cabinet (3) provides control signals for the A-layer plasma ignition device (5) and the B-layer plasma ignition device (6). When the A-layer plasma ignition device control power switch (7) and the A-layer plasma ignition device power switch (9) are closed, DC power and control signals are respectively supplied to the A-layer plasma ignition device (5). When the B-layer plasma ignition device control power switch (8) and the B-layer plasma ignition device power switch (10) are closed, DC power and control signals are respectively input to the B-layer plasma ignition device (6).

6. The control method for a boiler low-load stable combustion system with a double-layer plasma ignition device according to claim 2, characterized in that: If, during normal operation of the unit, one of the 8-corner or 4-corner plasma devices in the A-layer plasma ignition device (5) or B-layer plasma ignition device (6) fails, the unit will automatically switch to the corresponding corner of the other plasma ignition device.

7. The control method for a boiler low-load stable combustion system with a double-layer plasma ignition device according to claim 3, characterized in that: Only one of the A-layer plasma ignition device control power switch (7) and the B-layer plasma ignition device control power switch (8) can be closed. Only one of the A-layer plasma ignition device power switch (9) and the B-layer plasma ignition device power switch (10) can be closed.

8. The control method for a boiler low-load stable combustion system with a double-layer plasma ignition device according to claim 3, characterized in that: If the A-layer plasma ignition device control power switch (7) under the control cabinet (4) is closed, the B-layer plasma ignition device power switch (10) under the rectifier power cabinet (3) cannot be closed. If the B-layer plasma ignition device control power switch (8) under the control cabinet (4) is closed, the A-layer plasma ignition device power switch (9) under the rectifier power cabinet (3) cannot be closed. If the power switch (10) of the plasma ignition device in layer B under the rectifier power cabinet (3) is closed, the control power switch (7) of the plasma ignition device in layer A under the control cabinet (4) cannot be closed. If the power switch (9) of the plasma ignition device in layer A under the rectifier power cabinet (3) is closed, the control power switch (8) of the plasma ignition device in layer B under the control cabinet (4) cannot be closed.

9. The control method for a boiler low-load stable combustion system with a double-layer plasma ignition device according to claim 4, characterized in that: When the DCS remote control module selects the A-layer plasma ignition mode, the B-layer plasma ignition device control power switch (8) and the B-layer plasma ignition device power switch (10) automatically open, and then the A-layer plasma ignition device control power switch (7) and the A-layer plasma ignition device power switch (9) automatically close.

10. The control method for a boiler low-load stable combustion system with a dual-layer plasma ignition device according to claim 4, characterized in that: When the DCS remote control module selects the B-layer plasma ignition mode, the A-layer plasma ignition device control power switch (7) and the A-layer plasma ignition device power switch (9) automatically open, and then the B-layer plasma ignition device control power switch (8) and the B-layer plasma ignition device power switch (10) automatically close.

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