Boiler combustion system for low volatile coal

Abstract

The invention relates to a boiler combustion system for low volatile coal. The large air box and the primary air burner are arranged on the boiler body, the large air box is connected with the secondary air nozzle, and hot air is fed into a hearth of the boiler body through the secondary air nozzle; the primary fan is connected with the air preheater through an air pipe, a path of cold air is led out of the air pipe between the primary fan and the air preheater and is connected with the coal mill through the air pipe, and primary hot air at an outlet of the air preheater is connected with a cold air pipe between the primary fan and the coal mill through the air pipe; the boiler body is provided with at least two coal mills, pulverized coal pipelines are arranged at outlets of the coal mills, one end, far away from the coal mills, of each pulverized coal pipeline is connected with a primary air burner, and a primary air heating device is arranged on each pulverized coal pipeline; and after the temperature of the air-powder mixture is increased, ignition is easier, and the ignition and stable combustion characteristics of coal types are improved.

Description

Technical Field

[0001] The invention relates to the technical field of electric power industry, and in particular to a boiler combustion system for low-volatile coal. Background Art

[0002] Low volatile coal generally refers to coal with a dry ash-free volatile matter (Vdaf) of less than 15%, including some lean coal and anthracite, and is an important type of coal for power generation. This type of coal has a low volatile content, high ignition temperature, slow ignition, poor burnout, and is prone to unstable low-load combustion. The minimum stable combustion load of a boiler burning low-volatile coal is generally around 40% to 50% BMCR. The minimum stable combustion load of a boiler burning bituminous coal is generally around 20% to 30%. Today, when deep peak regulation of coal-fired units is becoming more and more frequent, it is imperative to reduce the minimum stable combustion load of boilers burning low-volatile coal.

[0003] There are many ways to improve the ignition characteristics of low-volatile coal.

[0004] One method is to increase the concentration of pulverized coal in the pulverized coal airflow. In the patent CN102563634B "Single Fireball Octagonal DC Burner Coal Powder Thick and Thin Separation Arrangement Structure", a thick and thin separator is set on the pulverized coal pipeline to divide the pulverized coal airflow into thick and thin streams, thereby increasing the pulverized coal concentration in the thick pulverized coal airflow and improving the ignition characteristics of the pulverized coal airflow.

[0005] One method is to increase the temperature of the pulverized coal airflow. Medium and small pulverized coal boilers below 300MW mostly use a central storage hot air pulverized coal delivery system. The hot air at the outlet of the air preheater is used to transport the prepared pulverized coal stored in the pulverized coal bin. The pulverized coal airflow temperature can be above 200℃, which can effectively improve the ignition characteristics of the pulverized coal airflow.

[0006] However, large boilers of 600MW and above cannot be equipped with a central storage hot air powder delivery system, and most of them use a direct blowing powder making system. The primary air of the boiler directly enters the coal mill to dry and transport the coal powder, and then enters the coal powder burner. Due to the limitations of the coal mill structure, the coal mill outlet air temperature generally needs to be less than 130℃ and cannot be further increased. Summary of the invention

[0007] In order to improve the ignition characteristics of low volatile coal, the existing large boilers of 600MW and above have the problem that the outlet air temperature of the pulverizer is generally less than 130℃ due to the limitation of the pulverizer structure and cannot be further improved. A boiler combustion system for low volatile coal is proposed.

[0008] The technical scheme of the present invention is: a boiler combustion system for low-volatile coal, comprising a boiler body, a primary air fan, a coal mill, a pulverized coal pipeline, a primary air heating device, a primary air burner, a large wind box, a secondary air nozzle, and an air preheater; the large wind box and the primary air burner are arranged on the boiler body, the large wind box is connected to the secondary air nozzle, and the hot air is sent into the furnace of the boiler body through the secondary air nozzle;

[0009] The primary fan is connected to the air preheater through an air duct, the air duct between the primary fan and the air preheater is led out and connected to the coal mill through the air duct, and the air preheater is connected to the air duct between the primary fan and the coal mill through the air duct;

[0010] The boiler body is equipped with at least two coal mills. A pulverized coal pipeline is set at the outlet of the coal mill. The end of the pulverized coal pipeline away from the coal mill is connected to a primary air burner. A primary air heating device is set on the pulverized coal pipeline.

[0011] Preferably, it also includes a secondary fan, which is connected to the air preheater through an air duct, and the air preheater is connected to the large air box through the air duct.

[0012] Preferably, it also includes a temperature control device, which outputs a power adjustment control signal to the primary air heating device.

[0013] Preferably, the primary air heating device is arranged continuously or in sections.

[0014] Preferably, the primary air heating device is provided with a heat preservation device to prevent heat from dissipating to the environment.

[0015] Preferably, the primary air heating device is electric heating, and an electric heating element is provided on the periphery of the pulverized coal pipeline.

[0016] Preferably, the primary air heating device adopts steam heating.

[0017] Preferably, the primary air heating device comprises a heater outer cylinder and guide vanes, the heater outer cylinder is sleeved on the outside of the pulverized coal pipeline, and guide vanes are provided between the heater outer cylinder and the pulverized coal pipeline.

[0018] Preferably, the guide blades are evenly spirally sleeved on the outer surface of the pulverized coal pipeline.

[0019] Preferably, a steam inlet is provided at one end of the primary air heating device, and a steam outlet is provided at the other end.

[0020] The beneficial effects of the present invention are as follows: the coal mill of the present invention dries, heats and transports coal powder into the coal powder pipeline, and the coal mill outlet air temperature is controlled between 120°C and 130°C by adjusting the ratio of cold and hot air at the coal mill inlet; the electric heating primary air heater on the coal powder pipeline further increases the temperature of the air-powder mixture, and the temperature rise can be controlled between 10°C and 100°C; after the temperature of the air-powder mixture is increased, it is easier to ignite, thereby improving the ignition and stable combustion characteristics of the coal. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of a boiler combustion system for low volatile coal of the present invention;

[0022] Figure 2 This is a schematic diagram of the structure of a heater using steam heating according to the present invention.

[0023] In the figure, the component names corresponding to the reference numerals are as follows:

[0024] 1. Boiler body; 2. Primary fan; 3. Coal mill; 4. Pulverized coal pipeline; 5. Primary air heating device; 51. Heater outer cylinder; 52. Guide vanes; 53. Steam inlet; 54. Steam outlet; 6. Primary air burner; 7. Secondary fan; 8. Large wind box; 9. Secondary air nozzle; 10. Temperature control device; 11. Air preheater. DETAILED DESCRIPTION

[0025] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0026] refer to Figure 1 As shown, the present invention provides a boiler combustion system for low-volatile coal, including a boiler body 1, a primary air fan 2, a coal mill 3, a pulverized coal pipeline 4, a primary air heating device 5, a primary air burner 6, a secondary air fan 7, a large wind box 8, a secondary air nozzle 9, a temperature control device 10, and an air preheater 11;

[0027] The boiler body 1 adopts a four-corner tangential combustion method. The air outlet of the primary fan 2 is directly connected to the air preheater 11 through an air duct to preheat the air. The air duct between the primary fan 2 and the air preheater 11 leads out and is connected to the air inlet of the coal mill 3 through the air duct. After the air is preheated by the air preheater 11, the air outlet of the air preheater 11 is connected to the air duct between the primary fan 2 and the coal mill 3 through the air duct. In this way, a part of the primary air at the outlet of the primary fan 2 is heated by the air preheater 11 and mixed with another part of the unheated primary air before entering the coal mill 3;

[0028] The air outlet of the secondary air fan 7 is directly connected to the air preheater 11 through the air duct to preheat the air. After the air preheater 11 preheats the air, the air outlet of the air preheater 11 is connected to the large wind box 8 through the air duct. The large wind box 8 is arranged on the boiler body 1. The large wind box 8 is connected to the secondary air nozzle 9, and the hot air is sent into the furnace of the boiler body 1 through the secondary air nozzle 9.

[0029] In this embodiment, there are 6 coal mills 3, and 4 pulverized coal pipelines 4 are arranged at the outlet of each coal mill 3. The ends of the pulverized coal pipelines 4 away from the coal mill 3 are respectively connected to the primary air burners 6, and the primary air burners 6 are arranged on the boiler body 1. The pulverized coal pipelines 4 of two coal mills 3 are provided with primary air heating devices 5. The primary air heating devices 5 can be arranged continuously according to the arrangement of the pulverized coal pipelines. Because the pulverized coal pipelines have bends, branches, etc., the heating devices can be divided into several sections and arranged separately or in sections, that is, arranged in sections;

[0030] The boiler body 1 is equipped with at least two coal mills 3, and a primary air heating device 4 is provided on the outlet coal powder pipeline 4 of at least one coal mill 3, and the coal powder airflow at the outlet of the coal mill 3 is heated by the primary air heating device 4;

[0031] The coal mill 3 dries, heats and transports the coal powder into the coal powder pipeline 4. By adjusting the ratio of cold and hot air at the inlet of the coal mill 3, the outlet air temperature of the coal mill 3 is controlled between 120°C and 130°C. The electric heating primary air heater 5 on the coal powder pipeline 4 further increases the temperature of the air-powder mixture, and the temperature rise can be controlled between 10°C and 100°C. The heated air-powder mixture enters the boiler body 1 through the primary air burner 6, and is mixed with the secondary air entering the furnace through the secondary air nozzle 9 and burned.

[0032] The temperature control device 10 outputs a control signal to the primary air heating device 5, and the power of the primary air heating device 5 is adjusted by the temperature control device 10 to control the increase range of the primary air temperature;

[0033] The primary air heating device 5 can be electrically heated or steam heated; the heating element is located outside the pulverized coal pipeline 4, and heat is transferred to the pulverized coal airflow by heating the pulverized coal pipeline 4; a heat preservation device is arranged outside the heating element to prevent heat from dissipating to the environment;

[0034] When steam heating is adopted, the primary air heating device 5 comprises a heater outer cylinder 51 and guide blades 52. The heater outer cylinder 51 is sleeved on the outside of the pulverized coal pipeline 4. The guide blades 52 are arranged between the heater outer cylinder 51 and the pulverized coal pipeline 4. The guide blades 52 are uniformly spirally sleeved on the outer surface of the pulverized coal pipeline 4. The guide blades 52 form a channel for steam circulation. A steam inlet 53 is arranged at one end of the bottom of the primary air heating device 5, and a steam outlet 54 is arranged at the other end.

[0035] The beneficial effects are as follows: the coal mill 3 of the present invention dries, heats and transports coal powder into the coal powder pipeline 4, and the outlet air temperature of the coal mill 3 is controlled between 120°C and 130°C by adjusting the ratio of cold and hot air at the inlet of the coal mill 3; the electric heating primary air heater 5 on the coal powder pipeline 4 further increases the temperature of the air-powder mixture, and the temperature rise can be controlled between 10°C and 100°C; after the temperature of the air-powder mixture is increased, it is easier to ignite, thereby improving the ignition and stable combustion characteristics of the coal.

[0036] It should be noted that the orientations or positional relationships indicated by the above-mentioned terms "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. The terms "first", "second", etc. are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. "Multiple" means two or more. "Installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection.

[0037] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and equivalent changes made by using the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A boiler combustion system for low-volatile coal, characterized in that: The boiler comprises a boiler body (1), a primary air fan (2), a coal mill (3), a pulverized coal pipeline (4), a primary air heating device (5), a primary air burner (6), a large wind box (8), a secondary air nozzle (9), and an air preheater (11); the large wind box (8) and the primary air burner (6) are arranged on the boiler body (1), the large wind box (8) is connected to the secondary air nozzle (9), and hot air is sent into the furnace of the boiler body (1) through the secondary air nozzle (9); The primary fan (2) is connected to the air preheater (11) through an air duct, a path of the air duct between the primary fan (2) and the air preheater (11) is connected to the coal mill (3) through the air duct, and the air preheater (11) is connected to the air duct between the primary fan (2) and the coal mill (3) through the air duct; The boiler body (1) is equipped with at least two coal mills (3), a pulverized coal pipeline (4) is arranged at the outlet of the coal mill (3), one end of the pulverized coal pipeline (4) away from the coal mill (3) is connected to a primary air burner (6), and a primary air heating device (5) is arranged on the pulverized coal pipeline (4).

2. The boiler combustion system for low volatile coal according to claim 1, characterized in that: It also includes a secondary fan (7), which is connected to the air preheater (11) through an air duct, and the air preheater (11) is connected to the large wind box (8) through an air duct.

3. The boiler combustion system for low volatile coal according to claim 1, characterized in that: It also includes a temperature control device (10), which outputs a power adjustment control signal to the primary air heating device (5).

4. The boiler combustion system for low volatile coal according to claim 1, characterized in that: The primary air heating device (5) is arranged continuously or in sections.

5. The boiler combustion system for low volatile coal according to claim 1, characterized in that: The primary air heating device (5) is provided with a heat preservation device for preventing heat from being dissipated to the environment.

6. The boiler combustion system for low-volatile coal according to claim 1, characterized in that: The primary air heating device (5) is electrically heated, and an electric heating element is arranged on the periphery of the pulverized coal pipeline (4).

7. The boiler combustion system for low-volatile coal according to claim 1, characterized in that: The primary air heating device (5) adopts steam heating.

8. The boiler combustion system for low-volatile coal according to claim 7, characterized in that: The primary air heating device (5) comprises a heater outer cylinder (51) and guide blades (52); the heater outer cylinder (51) is sleeved on the outside of the pulverized coal pipeline (4); and the guide blades (52) are provided between the heater outer cylinder (51) and the pulverized coal pipeline (4).

9. The boiler combustion system for low-volatile coal according to claim 8, characterized in that: The guide blades (52) are evenly spirally sleeved on the outer surface of the pulverized coal pipeline (4).

10. The boiler combustion system for low-volatile coal according to claim 9, characterized in that: The primary air heating device (5) is provided with a steam inlet (53) at one end and a steam outlet (54) at the other end.

Images