Method and system for optimizing operation of coal-fired boiler for blending combustion of high-volatile coal

Abstract

The invention discloses an operation optimization method and system for a coal-fired boiler for blending combustion of high-volatile coal types. The operation optimization system comprises a coal quantity calculation system, a total air volume calculation system, a primary air volume calculation system, a secondary air volume calculation system, a coal quantity adjustment system, a primary air volume adjustment system, a cold primary air volume adjustment system, a hot primary air volume adjustment system and a secondary air volume adjustment system. And the cold primary air volume adjusting system and the hot primary air volume adjusting system of each commissioning combustor layer are controlled, so that the temperature of the air-powder mixture at the outlet of the pulverizing system of each commissioning combustor layer reaches the target temperature of the air-powder mixture at the outlet. By adjusting the coal quantity, the cold primary air quantity, the hot primary air quantity and the secondary air quantity of a commissioning burner layer, the air quantity needed by a coal pulverizing system and the temperature of an outlet air-powder mixture during blending combustion of high-volatile coal types are guaranteed, and boiler exhaust gas temperature rise and heat efficiency reduction are avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of power station boilers, and in particular relates to an operation optimization method and system for a coal-fired boiler blended with high-volatile coal. Background Art

[0002] In addition to equipment transformation of thermal power units, optimizing equipment efficiency, reducing unit coal consumption and plant power consumption, blending and burning coal is also one of the ways to reduce costs and increase profits. Due to the difficulty in purchasing the original design coal or the high price, many thermal power plants are burning non-design coal with relatively low prices or relatively easy to purchase. Exploring the potential of coal has become the main means for thermal power plants to reduce production costs.

[0003] High-volatile coal is easy to ignite, burns stably and has a large flame, but it may cause the exhaust gas temperature of coal-fired boilers to increase, increase the amount of cooling water, increase the air preheater differential pressure, reduce boiler efficiency, and reduce the economic efficiency of unit operation. In addition, the self-ignition temperature of high-volatile coal is relatively low. If the coal powder is not blown into the furnace in time or accumulates in dead corners, it is very easy to cause the coal powder to spontaneously ignite in the pulverizing system, affecting the safe operation of the unit. Summary of the invention

[0004] In view of this, the present invention provides a method and system for optimizing the operation of a coal-fired boiler that burns high-volatile coal. The method takes a tangentially fired boiler as the research object, and avoids an increase in the boiler exhaust temperature and a decrease in thermal efficiency while ensuring the air volume required by the pulverizing system and the outlet air-powder mixture temperature when burning high-volatile coal.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for optimizing the operation of a coal-fired boiler blended with high-volatile coal, comprising:

[0006] The coal of the tangentially fired boiler is sprayed into the furnace in layers for combustion;

[0007] Calculate the target coal volume and target total air volume for each burner layer in operation;

[0008] Control the coal quantity adjustment system to keep the coal quantity of each operating burner layer the same;

[0009] According to the coal quantity and air-coal ratio curve of each operating burner layer, calculate the target primary air volume of each operating burner layer;

[0010] According to the dry ash-free volatile matter of the coal and the amount of coal in each operating burner layer, the target outlet air-powder mixture temperature of each operating burner layer is obtained;

[0011] Control the primary air volume regulating system of each operating burner layer so that the primary air volume of each operating burner layer reaches the target primary air volume;

[0012] Control the cold primary air volume regulating system and the hot primary air volume regulating system of each operating burner layer so that the outlet air-powder mixture temperature of the pulverizing system of each operating burner layer reaches the target outlet air-powder mixture temperature;

[0013] Control the secondary air volume adjustment system of each operating burner to make the secondary air volume of each operating burner reach the target secondary air volume.

[0014] Furthermore, the sum of the cold primary air volume of the operating burner layer and the hot primary air volume of the operating burner layer is the primary air volume of the operating burner layer.

[0015] Furthermore, the target coal quantity C of the nth burner layer is n The calculation formula is: C n =C z / n; among them, C z is the total coal quantity of the boiler, t / h.

[0016] Furthermore, the target total air volume F of the nth burner layer is zn The calculation formula is: Zn =C n ×α×β; where α is the theoretical air volume, t / t; β is the excess air coefficient.

[0017] Furthermore, the target secondary air volume F of the nth burner layer is en The calculation formula is: en =F zn -F yn ; Among them, F yn The target primary air volume for the nth operating burner layer, t / h.

[0018] The present invention also provides another technical solution: an operation optimization system for a coal-fired boiler blended with high-volatile coal, comprising a coal quantity calculation system, a total air volume calculation system, a primary air volume calculation system, a secondary air volume calculation system, a coal quantity adjustment system, a primary air volume adjustment system, a cold primary air volume adjustment system, a hot primary air volume adjustment system and a secondary air volume adjustment system;

[0019] The coal quantity calculation system is used to calculate the target coal quantity of each operating burner layer;

[0020] The total air volume calculation system is used to calculate the target total air volume of each operating burner layer according to the target coal volume, theoretical air volume and excess air coefficient of each operating burner layer;

[0021] The primary air volume calculation system is used to calculate the target primary air volume of each operating burner layer according to the coal volume of each operating burner layer and the air-coal ratio curve;

[0022] The secondary air volume calculation system is used to calculate the target secondary air volume of each operating burner layer according to the target total air volume and target primary air volume of each operating burner layer;

[0023] The coal quantity regulating system is used to keep the coal quantity of each operating burner layer the same;

[0024] The primary air volume regulating system is used to control the primary air volume regulating damper of each operating burner layer so that the primary air volume of each operating burner layer reaches the target primary air volume;

[0025] The cold primary air volume regulating system and the hot primary air volume regulating system are used to control the cold primary air volume regulating dampers and the hot primary air volume regulating dampers of each operating burner layer so that the outlet air-powder mixture temperature of the pulverizing system of each operating burner layer reaches the target outlet air-powder mixture temperature;

[0026] The secondary air volume regulating system is used to control the secondary air volume regulating damper of each operating burner layer so that the secondary air volume of each operating burner layer reaches the target secondary air volume.

[0027] Compared with the prior art, the present invention can ensure the air volume required by the pulverizing system and the outlet air-powder mixture temperature when blending high-volatile coal, and avoid the increase of boiler exhaust temperature and the decrease of thermal efficiency by adjusting the coal amount of the operating burner layer, cold primary air volume, hot primary air volume and secondary air volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of a method for optimizing the operation of a coal-fired boiler that burns high-volatile coal in the present invention;

[0029] Figure 2 The present invention is a schematic structural diagram of a coal-fired boiler operation optimization system for blending and burning high-volatile coal. DETAILED DESCRIPTION

[0030] The following will further describe the specific implementation of the present invention in combination with the accompanying drawings of the embodiments of the present invention, so that the technical solution of the present invention is easier to understand and grasp. It should be understood that the specific embodiments described here are only used to explain part of the embodiments of the invention, rather than all the embodiments. Other embodiments obtained by ordinary technicians in this field without making creative work are all within the scope of protection of the present invention.

[0031] Example 1

[0032] This embodiment provides an operation optimization method for a coal-fired boiler that burns high-volatile coal. The tangentially fired boiler that is more common in China is taken as the research object. It can ensure the air volume and outlet air-powder mixture temperature required by the pulverizing system when burning high-volatile coal, while avoiding an increase in the boiler exhaust temperature and a decrease in thermal efficiency.

[0033] Attached Figure 1 This is a flow chart of a method for optimizing the operation of a coal-fired boiler that burns high-volatile coal. The specific steps of the method are:

[0034] Step 1, injecting coal from a tangentially fired boiler into a furnace in layers for combustion;

[0035] Step 2, calculating the target coal volume and target total air volume of each burner layer in operation;

[0036] Step 3, control the coal quantity adjustment system to keep the coal quantity of each operating burner layer the same;

[0037] Step 4, calculating the target primary air volume of each operating burner layer according to the coal volume of each operating burner layer and the air-coal ratio curve;

[0038] Step 5, according to the dry ash-free volatile matter of the coal and the amount of coal in each operating burner layer, the target outlet air-powder mixture temperature of each operating burner layer is obtained;

[0039] Step 6, controlling the primary air volume regulating system of each operating burner layer so that the primary air volume of each operating burner layer reaches the target primary air volume;

[0040] Step 7, controlling the cold primary air volume regulating system and the hot primary air volume regulating system of each operating burner layer so that the outlet air-powder mixture temperature of the pulverizing system of each operating burner layer reaches the target outlet air-powder mixture temperature;

[0041] Step 8, controlling the secondary air volume regulating system of each operating burner so that the secondary air volume of each operating burner reaches the target secondary air volume.

[0042] After taking the above steps, if there are signs of coal blockage in the operating burner layer, adjust it by increasing the primary air volume.

[0043] If the outlet air-powder mixture temperature is too high at the operating burner layer, it means that the cold primary air volume is insufficient and can be adjusted by increasing the cold primary air volume.

[0044] If the thermal efficiency of the boiler decreases, the thermal efficiency of the boiler can be maintained by adjusting the secondary air volume of the operating burner.

[0045] The calculation formulas involved in the above steps are as follows:

[0046] The target coal quantity C of the nth layer of burners in operation n The calculation formula is: C n =C z / n; among them, C z is the total coal quantity of the boiler, t / h.

[0047] The target total air volume F of the burner layer in operation on the nth layer znThe calculation formula is: Zn =C n ×α×β; where α is the theoretical air volume, t / t; β is the excess air coefficient.

[0048] The target secondary air volume F of the burner layer in operation on the nth layer en The calculation formula is: en =F zn -F yn ; Among them, F yn The target primary air volume for the nth operating burner layer, t / h.

[0049] Application Examples

[0050] The present invention takes the operation of a subcritical 600MW four-corner tangential combustion boiler as an example. The boiler has 6×6 layers of burners. Usually, the boiler is put into operation with 5 layers of burners at full load, that is, 5×6 layers of burners are operated, and the burners in operation are in a combustion mode of equal coal distribution and equal air distribution. Table 1 shows the target outlet air-powder mixture temperature control value of the operating burner layer.

[0051] Table 1 Control value of air-powder mixture temperature at target outlet of burner layer in operation

[0052] Volatile matter on dry ash-free basis / % Outlet air-powder mixture temperature control value / ℃ ≤30 75-80 30-35 70-75 35-35 65-70 ≥40 60-65

[0053] Take a coal with a dry ash-free volatile content of 15% to 30% as an example. The auto-ignition temperature of this coal is 270 to 300°C, while the hot primary air temperature at the inlet of the pulverizer is usually controlled at 280 to 310°C. If the pulverized coal is not blown into the furnace in time or the pulverized coal is accumulated in the dead corner, it is very easy to cause the pulverized coal to spontaneously ignite in the pulverizing system, affecting the safe operation of the unit. Therefore, the primary air volume of the operating burner layer and the outlet air-powder mixture temperature should be kept within a reasonable range. Usually, the burner layer coal volume and wind-coal ratio curve should be operated to make the actual primary air volume consistent with the calculated theoretical primary air volume, so as to avoid the problem of coal blockage caused by too low primary air volume and the problem of reduced boiler thermal efficiency caused by too high primary air volume. At the same time, the outlet air-powder mixture temperature of the operating burner layer should be kept below 80°C. As the dry ash-free volatile content of the blended coal increases, the outlet air-powder mixture temperature should be controlled below 60°C.

[0054] When high-volatile and high-slagging coal is mixed and burned, if the flame center is not well controlled, it may cause coking of the boiler water-cooled wall. When high-volatile coal is mixed and burned, the cold primary air volume is larger than that of non-mixed high-volatile coal, and the heat exchange of the air preheater is reduced, resulting in an increase in the boiler exhaust temperature, an increase in the amount of cooling water, and an impact on the boiler thermal efficiency. In actual operation, attention should be paid to the relationship between the boiler thermal efficiency and the total air volume, and the total air volume of the boiler should be controlled at a reasonable level. At the same time, special attention should be paid to controlling the boiler air leakage, reducing the leakage of additional cold air into the boiler, and increasing the secondary air volume as much as possible to increase the heat exchange of the air preheater, avoid a significant increase in the boiler exhaust temperature, and maintain the boiler thermal efficiency at a high level.

[0055] Example 2

[0056] Please refer to the attached Figure 2 , which is a schematic diagram of an operation optimization system for a coal-fired boiler blended with high-volatile coal of the present invention. The present invention takes a tangentially fired boiler in a power station as a research object, and the system includes a coal quantity calculation system, a total air volume calculation system, a primary air volume calculation system, a secondary air volume calculation system, a coal quantity adjustment system, a primary air volume adjustment system, a cold primary air volume adjustment system, a hot primary air volume adjustment system and a secondary air volume adjustment system.

[0057] The coal quantity calculation system is used to calculate the target coal quantity of each operating burner layer.

[0058] The total air volume calculation system is used to calculate the target total air volume of each operating burner layer according to the target coal volume, theoretical air volume and excess air coefficient of each operating burner layer.

[0059] The primary air volume calculation system is used to calculate the target primary air volume of each operating burner layer according to the coal volume of each operating burner layer and the air-to-coal ratio curve.

[0060] The secondary air volume calculation system is used to calculate the target secondary air volume of each operating burner layer according to the target total air volume and the target primary air volume of each operating burner layer.

[0061] The coal quantity regulating system is used to keep the coal quantity of each operating burner layer the same.

[0062] The primary air volume regulating system is used to control the primary air volume regulating damper of each operating burner layer so that the primary air volume of each operating burner layer reaches the target primary air volume.

[0063] The cold primary air volume regulating system and the hot primary air volume regulating system are used to control the cold primary air volume regulating dampers and the hot primary air volume regulating dampers of each operating burner layer, so that the outlet air-powder mixture temperature of the powder making system of each operating burner layer reaches the target outlet air-powder mixture temperature.

[0064] The secondary air volume regulating system is used to control the secondary air volume regulating damper of each operating burner layer so that the secondary air volume of each operating burner layer reaches the target secondary air volume.

[0065] It should be noted that each system in the above-mentioned coal-fired boiler operation optimization system for burning high-volatile coal can be fully or partially implemented by software, hardware and their combination. The above-mentioned systems can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the corresponding operations of each of the above systems. For the specific definition of a coal-fired boiler operation optimization system for burning high-volatile coal, please refer to the definition of a coal-fired boiler operation optimization method for burning high-volatile coal in the above text. The two have the same functions and effects, which will not be repeated here.

[0066] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein.

Claims

1. A method for optimizing the operation of a coal-fired boiler that burns high-volatile coal, characterized in that: include: The coal of the tangentially fired boiler is sprayed into the furnace in layers for combustion; Calculate the target coal volume and target total air volume for each burner layer in operation; Control the coal quantity adjustment system to keep the coal quantity of each operating burner layer the same; According to the coal quantity and air-coal ratio curve of each operating burner layer, calculate the target primary air volume of each operating burner layer; According to the dry ash-free volatile matter of the coal and the amount of coal in each operating burner layer, the target outlet air-powder mixture temperature of each operating burner layer is obtained; Control the primary air volume regulating system of each operating burner layer so that the primary air volume of each operating burner layer reaches the target primary air volume; Control the cold primary air volume regulating system and the hot primary air volume regulating system of each operating burner layer so that the outlet air-powder mixture temperature of the pulverizing system of each operating burner layer reaches the target outlet air-powder mixture temperature; Control the secondary air volume adjustment system of each operating burner to make the secondary air volume of each operating burner reach the target secondary air volume.

2. The method for optimizing the operation of a coal-fired boiler blended with high-volatile coal according to claim 1, characterized in that: The target coal quantity C of the nth layer of burners in operation n The calculation formula is: C n =C z / n; among them, C z is the total coal quantity of the boiler, t / h.

3. The method for optimizing the operation of a coal-fired boiler blended with high-volatile coal according to claim 1, characterized in that: The target total air volume F of the burner layer in operation on the nth layer zn The calculation formula is: Zn =C n ×α×β; where α is the theoretical air volume, t / t; β is the excess air coefficient; C n The target coal quantity for the nth operating burner layer, t / h.

4. The method for optimizing the operation of a coal-fired boiler blended with high-volatile coal according to claim 1, characterized in that: The target secondary air volume F of the nth layer of burner in operation en The calculation formula is: en =F zn -F yn Among them, F yn The target primary air volume of the nth burner layer, t / h; F zn The target total air volume for the nth burner layer in operation, t / h.

5. The method for optimizing the operation of a coal-fired boiler blended with high-volatile coal according to claim 1, characterized in that: If there are signs of coal blockage in the operating burner layer, adjust it by increasing the primary air volume.

6. The method for optimizing the operation of a coal-fired boiler blended with high-volatile coal according to claim 1, characterized in that: If the outlet air-powder mixture temperature of the operating burner layer is too high, it can be adjusted by increasing the cold primary air volume.

7. The method for optimizing the operation of a coal-fired boiler blended with high-volatile coal according to claim 1, characterized in that: If the thermal efficiency of the boiler decreases, the thermal efficiency of the boiler can be maintained by adjusting the secondary air volume of the operating burner.

8. An operation optimization system for a coal-fired boiler burning high-volatile coal, characterized in that: It includes a coal quantity calculation system, a total air quantity calculation system, a primary air quantity calculation system, a secondary air quantity calculation system, a coal quantity adjustment system, a primary air quantity adjustment system, a cold primary air quantity adjustment system, a hot primary air quantity adjustment system and a secondary air quantity adjustment system; The coal quantity calculation system is used to calculate the target coal quantity of each operating burner layer; The total air volume calculation system is used to calculate the target total air volume of each operating burner layer according to the target coal volume, theoretical air volume and excess air coefficient of each operating burner layer; The primary air volume calculation system is used to calculate the target primary air volume of each operating burner layer according to the coal volume of each operating burner layer and the air-coal ratio curve; The secondary air volume calculation system is used to calculate the target secondary air volume of each operating burner layer according to the target total air volume and target primary air volume of each operating burner layer; The coal quantity regulating system is used to keep the coal quantity of each operating burner layer the same; The primary air volume regulating system is used to control the primary air volume regulating damper of each operating burner layer so that the primary air volume of each operating burner layer reaches the target primary air volume; The cold primary air volume regulating system and the hot primary air volume regulating system are used to control the cold primary air volume regulating dampers and the hot primary air volume regulating dampers of each operating burner layer, so that the outlet air-powder mixture temperature of the pulverizing system of each operating burner layer reaches the target outlet air-powder mixture temperature; The secondary air volume regulating system is used to control the secondary air volume regulating damper of each operating burner layer so that the secondary air volume of each operating burner layer reaches the target secondary air volume.

9. The operation optimization system for a coal-fired boiler burning high-volatile coal according to claim 8, characterized in that: In the coal quantity calculation system, the target coal quantity C of the nth layer of burners in operation is n The calculation formula is: C n =C z / n; among them, C z is the total coal quantity of the boiler, t / h; In the total air volume calculation system, the target total air volume F of the nth layer of burners in operation zn The calculation formula is: Zn =C n ×α×β; where α is the theoretical air volume, t / t; β is the excess air coefficient; C n The target coal quantity for the nth operating burner layer, t / h.

10. The operation optimization system for a coal-fired boiler blended with high-volatile coal according to claim 8, characterized in that: In the secondary air volume calculation system, the target secondary air volume F of the nth layer of burners in operation is en The calculation formula is: en =F zn -F yn Among them, F yn The target primary air volume of the nth burner layer, t / h; F zn The target total air volume for the nth burner layer in operation, t / h.

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