A tangential combustion system for pulverized coal boilers suitable for low volatile coal types

Abstract

This utility model discloses a tangential combustion system for pulverized coal boilers suitable for low-volatile coal types. It includes a boiler body, an air preheater, a secondary air fan, a primary air fan, and multiple coal mills. Each coal mill outlet is connected to multiple pulverized coal pipes. All pulverized coal pipes are connected to pulverized coal burners on the boiler body. Each pulverized coal burner is equipped with a burner air box. The secondary air fan outlet is connected to the burner air box via the air preheater. The primary air fan outlet is divided into two paths: one path connects to the hot primary air duct after passing through the air preheater, and the other path directly connects to the inlet of the hot primary air duct. The hot primary air duct outlet is divided into two paths: one path directly connects to the inlet of each coal mill, and the other path connects to the pulverized coal pipe at the outlet of each coal mill via a bypass hot primary air duct. This utility model can significantly increase the initial temperature of pulverized coal entering the furnace, improving the ignition and stable combustion capabilities of low-volatile coal.

Description

Technical Field

[0001] This utility model relates to a tangential combustion system for pulverized coal boilers suitable for low volatile coal types, belonging to the field of boiler technology. Background Technology

[0002] In my country's coal-fired power generating units, a significant portion of the boiler units burn low-volatile coal or anthracite, with a dry ash-free volatile matter (Vdaf) content of less than 20%, and those less than 6.5% are classified as ultra-low volatile matter coal. Low-volatile matter coals are difficult to ignite due to their high degree of coalification, low volatile matter content, and low calorific value of volatile matter in the overall calorific value. The increased degree of coalification also results in a denser and more stable petrographic structure, lower porosity, reduced reactivity, and poorer burnout performance. Therefore, ignition and burnout of low-volatile matter coals are both challenging, requiring higher ignition and burnout temperatures and longer burnout times.

[0003] To improve the combustion conditions of low-volatile coals, various technologies have been applied in engineering practice based on the theory of ignition heat required for pulverized coal combustion. Common methods include increasing pulverized coal concentration, increasing the initial temperature of pulverized coal, and improving the ignition heat source conditions, such as using combustion belt technology, hot air pulverization technology, rich-lean separation technology, blister combustion stabilization technology, and pre-combustion chamber technology. These technologies have a good effect on improving the ignition and stable combustion capabilities of low-volatile coals. However, for large-capacity boiler units, the conventional method of using hot air pulverization to increase the initial temperature of pulverized coal is not feasible due to the limitations of the direct-fired pulverizing system. With the increasing frequency of deep peak shaving by coal-fired power units and the trend towards larger capacity coal-fired units, it is necessary to further develop technical measures that are highly operable, effective, and economical to improve the ignition and stable combustion capabilities of low-volatile coals. Summary of the Invention

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

[0005] To solve the above-mentioned technical problems, the technical solution of this utility model is to provide a tangential combustion system for pulverized coal boilers suitable for low volatile coal types. The system is characterized by comprising a boiler body, an air preheater, a secondary air fan, a primary air fan, and multiple coal mills. Each coal mill outlet is connected to multiple pulverized coal pipes. All pulverized coal pipes are connected to pulverized coal burners on the boiler body. Each pulverized coal burner is equipped with a burner air box. The secondary air fan outlet is connected to the burner air box via the air preheater. The primary air fan outlet is divided into two paths: one path connects to the hot primary air duct after passing through the air preheater, and the other path directly connects to the inlet of the hot primary air duct. The hot primary air duct outlet is divided into two paths: one path directly connects to the inlet of each coal mill, and the other path connects to the pulverized coal pipe at the outlet of each coal mill via a 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 level of the boiler body; 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 equipped with an electric regulating door, and the pulverized coal pipeline is equipped with a temperature sensor; the electric regulating door and the temperature sensor are respectively connected to the controller.

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

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

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

[0011] Preferably, the outlets of the concentrated and dilute separation device are respectively connected to the upper and lower pulverized coal burners. The outlet that enters the boiler furnace through the upper pulverized coal burner is the dilute pulverized coal gas outlet, and the outlet that enters the boiler furnace through the lower pulverized coal burner is the concentrated pulverized coal gas 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 supplied to the pulverized coal pipeline at the coal mill outlet via a bypass hot primary air duct, where it mixes with the primary air / pulverized coal flow, further increasing the temperature of the primary air / pulverized coal mixture at the coal mill outlet. The bypass hot primary air duct is designed with shut-off and regulating valves, which can close or adjust the flow rate of the bypass hot primary air, thereby regulating the temperature rise of the primary air / pulverized coal mixture at the coal mill outlet to meet the design requirements of the boiler under different loads and when burning different types of coal.

[0014] This invention significantly improves the initial temperature of primary air / pulverized coal entering the furnace, reduces the heat required for ignition of the pulverized coal airflow, enhances the ignition capability, stable combustion capability, and burnout of pulverized coal, strengthens the adaptability of the pulverized coal burner to low-volatile coal types, and also enhances the safety and economy of the boiler.

[0015] This invention can significantly increase the initial temperature of pulverized coal entering the furnace, and improve the ignition and stable combustion capabilities of low-volatile coal. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a tangential combustion system for a 600MW pulverized coal boiler, applicable to low volatile coal types.

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

[0018] To make this utility model more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0019] Example 1

[0020] This utility model provides a tangential combustion system for pulverized coal boilers suitable for low-volatile coal types, such as... Figure 1 As shown, it consists of a boiler body 1, a burner air box 2, a pulverized coal burner 3, a secondary air duct 4, an air preheater 5, a secondary air fan 6, a primary air fan 7, a hot primary air duct 8, a coal mill 9, a temperature sensor 10, a pulverized coal pipeline 11, a bypass hot primary air duct 12, an electric regulating valve 13, and a pneumatic shut-off valve 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 level 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, which are connected to the pulverized coal burners 3 at the four corners of the boiler body 1. Figure 1 The design of one pulverized coal pipe 11 of the coal mill 9 numbered A is shown only. The design of the other pulverized coal pipes 11 is the same. That is, the four pulverized coal pipes 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] Each coal mill 9 outlet is equipped with multiple pulverized coal pipes 11. All pulverized coal pipes 11 are connected to the pulverized coal burners 3 on the boiler body 1. The pulverized coal burners 3 are equipped with burner air boxes 2. The outlet of the secondary air fan 6 is connected to the burner air box 2 through the air preheater 5. The outlet of the primary air fan 7 is divided into two paths. One path is connected to the hot primary air duct 8 after passing through the air preheater 5. The other path 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 paths. One path is directly connected to the inlet of each coal mill 9. The other path is connected to the pulverized coal pipes 11 at the outlet of each coal mill 9 through the bypass hot primary air duct 12.

[0024] In operation, the ambient temperature secondary air from the outlet of secondary air fan 6 is heated by air preheater 5 and then sent to burner air box 2, before entering boiler body 1. A portion of the ambient temperature primary air from the outlet of primary air fan 7 is heated by air preheater 5 and mixed with the unheated ambient temperature primary air from the outlet of primary air fan 7 before entering hot primary air duct 8. A portion of the hot primary air in hot primary air duct 8 directly enters coal mill 9 for pulverization, while the other portion is mixed with the primary air / pulverized coal flow in pulverized coal pipeline 11 at the outlet of coal mill 9 via bypass hot primary air duct 12 before being sent to pulverized coal burner 3. No heating device is installed on pulverized coal pipeline 11.

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

[0026] In this invention, a portion of the hot primary air is mixed into the pulverized coal pipeline 11 via the bypass hot primary air duct 12, further increasing the temperature of the primary air / pulverized coal flow entering the pulverized coal burner 3. The temperature rise can generally reach 10–50°C. After the initial temperature of the pulverized coal increases, its required ignition heat decreases, which is beneficial for ignition, stable combustion, and complete combustion. For low-volatile coal with a dry ash-free volatile matter (Vdaf) content of no more than 15%, the improvement effect will be very significant. This is especially true for large-capacity pulverized coal boilers using a double-inlet, double-outlet steel ball mill direct-fired pulverized coal feeding system that burns anthracite. The technical solution of this invention overcomes the temperature limitations of the coal mill itself, does not change the design of the original pulverizing system, and provides more efficient and direct heating of the primary air / pulverized coal flow without affecting the drying output of the coal mill. It features a simple system, high energy efficiency, and good performance.

[0027] The boiler adopts tangential combustion technology, and the pulverizing system is equipped with six direct-fired 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 rich-lean separation device 15 is designed on the pipeline before the pulverized coal pipeline 11 enters the pulverized coal burner 3. Otherwise, it is the same as embodiment 1. That is, all pulverized coal pipelines 11 are connected to the pulverized coal burners 3 on the boiler body 1 through the rich-lean separation device 15. The outlet of the rich-lean separation device 15 is connected to the upper and lower pulverized coal burners 3 respectively. The outlet of the upper pulverized coal burner 3 entering the furnace of the boiler body 1 is the lean pulverized coal gas outlet, and the outlet of the lower pulverized coal burner 3 entering the furnace of the boiler body 1 is the rich pulverized coal gas outlet.

[0030] After separation by the thick-thickness separation device 15, the primary air / pulverized coal flow in the pulverized coal pipeline 11 is divided into two streams: a thick pulverized coal flow and a thin pulverized coal flow. The thick pulverized coal flow is sent into the furnace from the lower pulverized coal burner 3, while the thin pulverized coal flow is sent into the furnace from the upper pulverized coal burner 3. With the addition of the thick-thickness separation device 15, the pulverized coal concentration in the thick pulverized coal flow is significantly increased, which is more conducive to the ignition and stable combustion of pulverized coal and further expands the applicability range for low-volatile coal types.

Claims

1. A tangential combustion system for pulverized coal boilers suitable for low-volatile coal types, characterized in that, The system includes a boiler body (1), an air preheater (5), a secondary air fan (6), a primary air fan (7), and multiple coal mills (9). Each coal mill (9) has multiple pulverized coal pipes (11) connected to its outlet. All pulverized coal pipes (11) are connected to the pulverized coal burners (3) on the boiler body (1). The pulverized coal burners (3) are equipped with burner air boxes (2). The outlet of the secondary air fan (6) is connected to the burner air box (2) through the air preheater (5). The outlet of the primary air fan (7) is divided into two paths. One path is connected to the hot primary air duct (8) after passing through the air preheater (5), and the other path 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 paths. One path is directly connected to the inlet of each coal mill (9), and the other path is connected to the pulverized coal pipes (11) at the outlet of each coal mill (9) through the bypass hot primary air duct (12).

2. The tangential combustion system for pulverized coal boilers suitable for low-volatile coal types as described in 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 level 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).

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

4. A tangential combustion system for pulverized coal boilers suitable for low-volatile coal types as described in claim 1, characterized in that, The bypass hot primary air duct (12) is also provided with a pneumatic shut-off valve (14) for opening and closing the bypass hot primary air duct (12); the pneumatic shut-off valve (14) is connected to the controller.

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

6. A tangential combustion system for pulverized coal boilers suitable for low-volatile coal types, as described in any one of claims 1-4, characterized in that... All of the pulverized coal pipelines (11) are connected to the pulverized coal burners (3) on the boiler body (1) via a concentration separation device (15).

7. A tangential combustion system for pulverized coal boilers suitable for low-volatile coal types as described in claim 6, characterized in that, The outlet of the concentrated-dilute separation device (15) is connected to the upper and lower pulverized coal burners (3), respectively. The outlet of the upper pulverized coal burner (3) into the furnace of the boiler body (1) is the dilute pulverized coal gas outlet, and the outlet of the lower pulverized coal burner (3) into the furnace of the boiler body (1) is the concentrated pulverized coal gas outlet.

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