Pulverized coal boiler tangential combustion system suitable for low-volatile coal

Abstract

The invention discloses a pulverized coal boiler tangential combustion system suitable for low-volatile coal types, which comprises a boiler body, an air pre-heater, a secondary fan, a primary fan and a plurality of coal mills, an outlet of each coal mill is connected with a plurality of pulverized coal pipelines, all the pulverized coal pipelines are respectively communicated with a pulverized coal burner on the boiler body, and the pulverized coal burners are communicated with the air pre-heater. The outlet of the primary fan is divided into two paths, one path is communicated with the hot primary air duct after passing through the air pre-heater, the other path is directly connected with the inlet of the hot primary air duct, the outlet of the hot primary air duct is divided into two paths, one path is directly connected with the inlet of each coal mill, and the other path is directly connected with the outlet of each coal mill; and the other path is communicated with the pulverized coal pipeline at the outlet of each coal mill through a bypass hot primary air duct. According to the invention, the initial temperature of pulverized coal entering the furnace can be obviously increased, and the ignition capacity and stable combustion capacity of low-volatile coal can be improved.

Description

Technical Field

[0001] The invention relates to a tangential combustion system for a pulverized coal boiler suitable for low-volatile coal, and belongs to the technical field of boilers. Background Art

[0002] A significant portion of my country's coal-fired power generation units utilize low-volatile lean coal or anthracite in their boiler units. Its dry ash-free volatile matter (Vdaf) content is less than 20%, and those with less than 6.5% are considered ultra-low-volatile coal. Low-volatile coal, due to its high degree of coalification, low volatile content, and low calorific value ratio of volatiles to calorific value, makes ignition difficult. This increased degree of coalification also results in a dense and stable lithofacies structure, low porosity, reduced reactivity, and poor burnout performance. Consequently, low-volatile coal is difficult to ignite and burn out, requiring higher ignition and burnout temperatures and longer burnout times.

[0003] To improve the combustion conditions of low-volatile coal, various technical measures have been applied in engineering practice based on the theory of the ignition heat required for pulverized coal combustion. Common methods include increasing pulverized coal concentration, raising the initial pulverized coal temperature, and improving the heat source conditions for pulverized coal ignition. These methods, such as using guard belt technology, hot air pulverized coal delivery, concentrated-lean separation technology, blunt body combustion stabilization technology, and pre-combustion chamber technology, have shown significant effectiveness in improving the ignition and stable combustion capabilities of low-volatile coal. However, for large-capacity boiler units, the conventional method of raising the initial pulverized coal temperature through hot air delivery is not feasible due to the limitations of direct-blowing pulverized coal systems. With the increasing frequency of deep peak shaving of coal-fired power generation units and the trend towards larger coal-fired units, further development of highly operational, effective, and cost-effective technical measures is needed to improve the ignition and stable combustion capabilities of low-volatile coal. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: how to improve the ignition and stable combustion capabilities of low-volatile coal in large-capacity boiler units.

[0005] In order to solve the above technical problems, the technical solution of the present invention is to provide a tangential combustion system of a pulverized coal boiler suitable for low-volatile coal, which is characterized in that it includes a boiler body, an air preheater, a secondary fan, a primary fan and multiple coal mills, and each coal mill outlet is connected to multiple coal powder pipes, all of which are respectively connected to the coal powder burner on the boiler body, and the coal powder burner is provided with a burner bellows. The secondary fan outlet is connected to the burner bellows through the air preheater, and the primary fan outlet is divided into two routes, one of which is connected to the hot primary air duct after passing through the air preheater, and the other is directly connected to the hot primary air duct inlet. The hot primary air duct outlet is divided into two routes, one of which is directly connected to each coal mill inlet, and the other is connected to the coal powder pipe of each coal mill outlet through the bypass hot primary air duct.

[0006] Preferably, the number of pulverized coal pipes at the outlet of each coal mill is the same as the number of pulverized coal burners at the same height layer of the boiler body; and one pulverized coal pipe on each coal mill is connected to one pulverized coal burner on the boiler body.

[0007] Preferably, the bypass hot primary air duct is provided with an electric regulating door, and the pulverized coal pipeline is provided with a temperature sensor; the electric regulating door and the temperature sensor are respectively connected to a controller.

[0008] Preferably, the bypass hot primary air duct is further provided with a pneumatic shut-off door for opening and closing the bypass hot primary air duct; the pneumatic shut-off door is connected to a controller.

[0009] Preferably, all the pulverized coal pipelines are directly connected to the pulverized coal burners on the boiler body.

[0010] Preferably, all the pulverized coal pipelines are connected to the pulverized coal burners on the boiler body through a thick-lean separation device.

[0011] Preferably, the outlet of the thick and thin separation device is connected to the upper and lower pulverized coal burners respectively, the outlet connected to the boiler body furnace through the upper pulverized coal burner is the thin pulverized coal airflow outlet, and the outlet connected to the boiler body furnace through the lower pulverized coal burner is the thick pulverized coal airflow outlet.

[0012] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0013] In this invention, a portion of the hot primary air is delivered through a bypass hot primary air duct into the pulverized coal duct at the pulverized coal mill outlet, where it mixes with the primary air / pulverized coal flow, further raising the temperature of the primary air / pulverized coal mixture at the pulverized coal mill outlet. A shutoff valve and a regulating valve are designed on the bypass hot primary air duct to shut off or adjust the bypass hot primary air flow rate, thereby regulating the temperature rise of the primary air / pulverized coal mixture at the pulverized coal mill outlet, meeting the design requirements for different boiler loads and coal types.

[0014] The present invention achieves a significant increase in the initial temperature of the primary air / powder entering the furnace, reduces the heat required for ignition of the pulverized coal airflow, improves the ignition ability, stable combustion ability and burnout of the pulverized coal, enhances the adaptability of the pulverized coal burner to low-volatile coal, and also enhances the safety and economy of the boiler.

[0015] The present invention can significantly increase the initial temperature of coal powder entering the furnace, and improve the ignition ability and stable combustion ability of low-volatile coal. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of a tangential combustion system for a 600MW pulverized coal boiler suitable for low-volatile coal.

[0017] Figure 2This is a schematic diagram of a tangential combustion system for a pulverized coal boiler suitable for low-volatile coal, taking a 600MW pulverized coal boiler as an example. DETAILED DESCRIPTION

[0018] To make the present invention more clearly understood, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0019] Example 1

[0020] The present invention provides a tangential combustion system for pulverized coal boilers suitable for low-volatile coal. Figure 1 As shown, it consists of a boiler body 1, a burner wind box 2, a pulverized coal burner 3, a secondary air duct 4, an air preheater 5, a secondary fan 6, a primary fan 7, a hot primary air duct 8, a pulverizer 9, a temperature sensor 10, a pulverized coal pipeline 11, a bypass hot primary air duct 12, an electric regulating door 13 and a pneumatic shut-off door 14.

[0021] The number of pulverized coal pipes 11 at the outlet of each coal mill 9 is the same as the number of pulverized coal burners 3 at the same height layer of the boiler body 1 ; one pulverized coal pipe 11 on each coal mill 9 is connected to one pulverized coal burner 3 on the boiler body 1 .

[0022] In this embodiment, each coal mill 9 has four pulverized coal pipes 11 at its outlet, connected to the pulverized coal burners 3 ( Figure 1 Only the design of one pulverized coal pipeline 11 of the coal mill 9 numbered A is shown, and the designs of the other pulverized coal pipelines 11 are the same), that is, the four pulverized coal pipelines 11 of each coal mill 9 are respectively connected to the four pulverized coal burners 3 located at the four corners of the same height layer.

[0023] A plurality of pulverized coal pipes 11 are provided at the outlet of each coal mill 9. All the pulverized coal pipes 11 are respectively connected and communicated with the pulverized coal burners 3 on the boiler body 1. The pulverized coal burners 3 are provided with a burner wind box 2. The outlet of the secondary air fan 6 is connected to the burner wind box 2 through the air preheater 5. The outlet of the primary air fan 7 is divided into two routes, one of which is connected to the hot primary air duct 8 after passing through the air preheater 5, and the other is directly connected to the inlet of the hot primary air duct 8. The outlet of the hot primary air duct 8 is divided into two routes, one of which is directly connected to the inlet of each coal mill 9, and the other is connected to the pulverized coal pipe 11 at the outlet of each coal mill 9 through the bypass hot primary air duct 12.

[0024] During operation, the ambient temperature secondary air at the outlet of the secondary fan 6 is heated by the air preheater 5 before being fed into the burner windbox 2 and then into the boiler body 1. A portion of the ambient temperature primary air at the outlet of the primary fan 7 is heated by the air preheater 5 and mixed with the ambient temperature primary air at the outlet of the primary fan 7 that has not been heated by the air preheater 5 before entering the hot primary air duct 8. A portion of the hot primary air in the hot primary air duct 8 directly enters the coal mill 9 to participate in pulverizing. The remaining portion passes through the bypass hot primary air duct 12 and is mixed with the primary air / pulverized coal airflow in the pulverized coal duct 11 at the outlet of the coal mill 9 before being fed into the pulverized coal burner 3. The pulverized coal duct 11 is not equipped with a heating device.

[0025] An electric regulating door 13 is designed on the bypass hot primary air duct 12, and a temperature sensor 10 is provided on the pulverized coal pipeline 11. The electric regulating door 13 and the temperature sensor 10 are connected to the controller via wires or wireless signals. According to the temperature feedback from the temperature sensor 10 installed on the pulverized coal pipeline 11 (i.e., the temperature of the primary air in the pulverized coal pipeline 11), the signal can be transmitted to the controller, and the controller issues an opening instruction to the electric regulating door 13, thereby adjusting the flow in the bypass hot primary air duct 12 accordingly to meet the primary air / powder design temperature and explosion-proof requirements required in the pulverized coal pipeline 11. A pneumatic shut-off door 14 is provided on the bypass hot primary air duct 12, and the bypass hot primary air duct 12 can be closed by the pneumatic shut-off door 14 to meet the pulverizing requirements of the coal mill 9. The pneumatic shut-off door 14 is connected to the controller via wires or wireless signals.

[0026] In the present invention, after a portion of the hot primary air is mixed into the pulverized coal pipeline 11 through the bypass hot primary air duct 12, the temperature of the primary air / pulverized air flow entering the pulverized coal burner 3 is further increased, and the temperature rise can generally reach 10 to 50°C. After the initial temperature of the pulverized coal is increased, the heat required for ignition will decrease, which is beneficial to the ignition, stable combustion and burnout of the pulverized coal. For low-volatile coal with a dry ash-free volatile matter (Vdaf) of no more than 15%, the improvement effect will be very significant, especially for large-capacity pulverized coal boilers that use a double-inlet and double-outlet steel ball mill direct-blowing pulverized coal feeding system for burning anthracite. The technical solution of the present invention breaks through the temperature limit of the pulverizer equipment itself, does not change the design of the original pulverizing system, and heats the primary air / pulverized air flow more efficiently and directly, without affecting the drying output of the pulverizer. It has the characteristics of a simple system, high energy efficiency and good effect.

[0027] Among them, the boiler adopts four-corner tangential combustion technology, and the pulverizing system is equipped with six direct-blowing coal mills, numbered A to F.

[0028] Example 2

[0029] like Figure 2As shown, the difference between this embodiment 2 and embodiment 1 is that a dense-lean separation device 15 is designed on the pipeline before the pulverized coal pipeline 11 enters the pulverized coal burner 3. The other aspects are the same as those of embodiment 1. That is, all pulverized coal pipelines 11 are connected to the pulverized coal burners 3 on the boiler body 1 through the dense-lean separation device 15. The outlets of the dense-lean separation device 15 are respectively connected to the upper and lower pulverized coal burners 3. The outlet that connects to the furnace of the boiler body 1 through the upper pulverized coal burner 3 is the outlet for the lean pulverized coal airflow, and the outlet that connects to the furnace of the boiler body 1 through the lower pulverized coal burner 3 is the outlet for the dense pulverized coal airflow.

[0030] After separation by the dense-lean separation device 15, the primary air / powdered coal flow in the pulverized coal pipeline 11 is divided into a dense pulverized coal flow and a lean pulverized coal flow. The dense pulverized coal flow is delivered to the furnace through the lower pulverized coal burner 3, while the lean pulverized coal flow is delivered to the furnace through the upper pulverized coal burner 3. The addition of the dense-lean separation device 15 significantly increases the pulverized coal concentration in the dense pulverized coal flow, further facilitating ignition and stable combustion of the pulverized coal, and further expanding the range of applicability to burning low-volatile coals.

Claims

1. A tangential combustion system for pulverized coal boilers suitable for low-volatile coal, characterized in that: The invention comprises a boiler body (1), an air preheater (5), a secondary air fan (6), a primary air fan (7) and a plurality of coal mills (9). The outlet of each coal mill (9) is connected to a plurality of pulverized coal pipes (11). All the pulverized coal pipes (11) are respectively connected to the pulverized coal burner (3) on the boiler body (1). The pulverized coal burner (3) is provided with a burner wind box (2). The outlet of the secondary air fan (6) is connected to the burner wind box (2) through the air preheater (5). The outlet of the primary air fan (7) is divided into two routes. One route is connected to the hot primary air duct (8) after passing through the air preheater (5), and the other route is directly connected to the inlet of the hot primary air duct (8). The outlet of the hot primary air duct (8) is divided into two routes. One route is directly connected to the inlet of each coal mill (9), and the other route is connected to the pulverized coal pipe (11) at the outlet of each coal mill (9) through a bypass hot primary air duct (12).

2. The tangential combustion system for a pulverized coal boiler suitable for low-volatile coal according to claim 1, characterized in that: The number of pulverized coal pipes (11) at the outlet of each coal mill (9) is the same as the number of pulverized coal burners (3) at the same height layer of the boiler body (1); and one pulverized coal pipe (11) on each coal mill (9) is connected to one pulverized coal burner (3) on the boiler body (1).

3. The tangential combustion system for a pulverized coal boiler suitable for low-volatile coal according to claim 1, characterized in that: The bypass hot primary air duct (12) is provided with an electric regulating door (13), and the pulverized coal pipeline (11) is provided with a temperature sensor (10); the electric regulating door (13) and the temperature sensor (10) are respectively connected to a controller.

4. The tangential combustion system for a pulverized coal boiler suitable for low-volatile coal according to claim 1, characterized in that: The bypass hot primary air duct (12) is also provided with a pneumatic shutoff door (14) for opening and closing the bypass hot primary air duct (12); the pneumatic shutoff door (14) is connected to a controller.

5. A tangential combustion system for a pulverized coal boiler suitable for low-volatile coal according to any one of claims 1 to 4, characterized in that: All the pulverized coal pipelines (11) are directly connected to the pulverized coal burners (3) on the boiler body (1).

6. A tangential combustion system for a pulverized coal boiler suitable for low-volatile coal according to any one of claims 1 to 4, characterized in that: All the pulverized coal pipelines (11) are connected to the pulverized coal burners (3) on the boiler body (1) through the thick-thin separation device (15).

7. The tangential combustion system for a pulverized coal boiler suitable for low-volatile coal according to claim 6, characterized in that: The outlets of the thick and thin separation device (15) are respectively connected to the upper and lower pulverized coal burners (3); the outlet connected to the furnace of the boiler body (1) through the upper pulverized coal burner (3) is the thin pulverized coal airflow outlet, and the outlet connected to the furnace of the boiler body (1) through the lower pulverized coal burner (3) is the thick pulverized coal airflow outlet.

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