A W-shaped flame boiler capable of stable combustion under low load conditions

Abstract

This utility model discloses a W-type flame boiler capable of stable combustion under low-load conditions. It includes a furnace body with a front radiant arch area and a rear radiant arch area. Multiple pulverized coal burners are evenly spaced along the transverse direction of the front and rear radiant arch areas. The feed inlets of the pulverized coal burners are connected to a pulverized coal supply system via pulverized coal conveying pipes. A low-load pulverized coal burner is located on the furnace body, and a combustion cavity is provided on the low-load pulverized coal burner. A solid fuel stabilizing ignition device is installed within the combustion cavity, and the combustion cavity is connected to the inner cavity of the furnace body. A low-load pulverized coal conveying pipe, connected to the combustion cavity, is also provided on the low-load pulverized coal burner. This device injects flame, rather than pulverized coal, into the inner cavity of the furnace body through the low-load pulverized coal burner, ensuring stable combustion of the W-type flame boiler under low-load conditions. This eliminates the need for large oil guns to inject diesel fuel into the furnace for combustion assistance under low-load conditions, saving operating costs.

Description

Technical Field

[0001] This utility model relates to coal-fired boilers, and in particular to a W-type flame boiler that can stably burn under low load conditions. Background Technology

[0002] W-type flame boilers, a special structural type of coal-fired boilers, employ an asymmetrical cavity design, vertically divided into upper and lower furnace modules with significantly different depths. Specifically, the lower furnace cavity is 80%-120% deeper than the upper furnace, naturally forming a radial arch structure at the cavity junction due to this depth difference. Regarding the combustion system configuration: the main combustion zone is located in the radial arch, including a pulverized coal nozzle array and a secondary air distribution device. The primary pulverized coal airflow and a portion of the secondary air are injected downwards through nozzles on the arch. The combustion dynamics are as follows: after initial ignition in the arch area, the primary pulverized coal airflow forms a downward flame front; this flame front forms a turbulent mixing zone with the secondary air system at the bottom of the lower furnace, achieving a 180° flow field reversal after momentum exchange, ultimately forming a characteristic W-shaped double flame front rising trajectory in the core area of ​​the furnace. This structure achieves efficient utilization of difficult-to-burn coal types through three major combustion enhancement mechanisms: 1) the expanded volume of the lower furnace provides a combustion field with a long residence time (>3.5s); 2) the downward-upward flame path forms a temperature field gradient (1600-1200℃ gradient distribution); 3) the dual-circulation motion mode of pulverized coal particles. It is particularly suitable for the combustion conditions of anthracite with volatile matter content <10% and low-quality coal with calorific value <18MJ / kg. The specific configuration of the combustion system is as follows: 24 swirl-type pulverized coal burners are evenly distributed in a matrix in the front and rear radial arch areas, and every 4 burner units constitute a pulverizing-injection subsystem, with a total of 6 MPS-type medium-speed coal mills (output coefficient 1:1.2). Under high load conditions (>75% BMC), the entire coal mill unit operates to form a symmetrical pulverized coal concentration field (deviation <8%), at which time the core area of ​​the lower furnace can maintain a stable combustion temperature of 1600±50℃. However, there are two technical defects under low load conditions (<40% BMC): First, the forced shutdown of four coal mills causes the burner working distance to increase to 2.1 times the design value, resulting in a coal powder distribution unevenness coefficient >35%, causing an imbalance in the thermal stress distribution of the furnace wall (temperature difference up to 480℃ / m), posing a risk of structural fatigue; Second, the temperature field of the lower furnace decays to the critical range of 800-900℃, coupled with the initial velocity of coal powder injection >28m / s (corresponding to a volumetric flow rate of 1.2×10^6 m³ / h), generating a strong turbulent flow field with a Reynolds number >2×10^5, which destroys the flame stability zone of the ignited coal powder, greatly reducing the boiler combustion stability. Low-load stable combustion can only be achieved through a diesel-assisted combustion system, but this leads to a surge in operating costs (fuel cost ratio increases by 12-18%). Utility Model Content

[0003] In view of this, the purpose of this utility model is to provide a W-type flame boiler that can stably burn under low load conditions, so as to at least solve the technical problem of the soaring cost of adding diesel fuel to W-type flame boilers when operating at low load.

[0004] The objective of this utility model is achieved through the following technical solution:

[0005] A W-type flame boiler capable of stable combustion under low-load conditions includes a furnace body with a front radiant arch zone and a rear radiant arch zone. Multiple pulverized coal burners are evenly spaced along the transverse direction in both the front and rear radiant arch zones. The feed inlets of the pulverized coal burners are connected to a pulverized coal supply system via pulverized coal conveying pipes. A low-load pulverized coal burner is located on the furnace body, and a combustion cavity is provided on the low-load pulverized coal burner. A solid fuel stabilizing ignition device is located within the combustion cavity. The combustion cavity communicates with the inner cavity of the furnace body. A low-load pulverized coal conveying pipe, connected to the combustion cavity, is also located on the low-load pulverized coal burner and connected to the pulverized coal supply system.

[0006] Furthermore, there are several low-load pulverized coal burners, each divided into two groups. The two groups of low-load pulverized coal burners are respectively located on the front and rear radiant arch areas or the front and rear F-wind areas.

[0007] Furthermore, a group of multiple low-load pulverized coal burners are evenly spaced along the transverse direction in the front radiating arch area, and a group of multiple low-load pulverized coal burners are evenly spaced along the transverse direction in the rear radiating arch area.

[0008] Furthermore, the pulverized coal supply system is a coal mill, and the four pulverized coal burners are each connected to a coal mill through a pulverized coal conveying pipe.

[0009] Furthermore, each of the coal powder conveying pipes on one-third of the coal mills is connected to a main pipeline. One end of the main pipeline is connected to the coal powder conveying pipe, and the other end is connected to two low-load coal powder conveying pipes. The ends of the two low-load coal powder conveying pipes are respectively connected to two low-load coal powder burners. Valves are installed on the coal powder conveying pipes between the main pipeline and the coal powder burners, and valves are installed on the main pipeline.

[0010] The beneficial effects of this utility model are:

[0011] The W-type flame boiler proposed in this utility model, which can stably burn under low-load conditions, is an improvement on the original W-type flame boiler. Specifically, it features a low-load pulverized coal burner on the boiler body, a combustion cavity on the low-load pulverized coal burner, and a solid fuel stable ignition device inside the combustion cavity. The combustion cavity is connected to the inner cavity of the boiler body. A low-load pulverized coal conveying pipe, connected to the combustion cavity, is also located on the low-load pulverized coal burner and connected to the pulverized coal supply system. Under low-load conditions, the solid fuel stable ignition device ignites the pulverized coal with pure oxygen inside the low-load pulverized coal burner. Therefore, the low-load pulverized coal burner injects a coal flame after ignition into the inner cavity of the boiler body, rather than pulverized coal itself. The ignited coal flame continues to burn after entering the furnace, changing the traditional method of pulverized coal entering the furnace and undergoing heat exchange ignition. This ensures stable combustion of the W-type flame boiler under low-load conditions, eliminating the need for large oil guns to inject diesel fuel into the furnace for combustion assistance, thus saving operating costs.

[0012] The low-load pulverized coal burners on the front and rear radiant arch areas or the front and rear F-wind areas are all arranged at uniform intervals along their transverse direction. Under low-load conditions, each low-load pulverized coal burner ignites the pulverized coal and enters the furnace, achieving uniform heat distribution within the furnace and reducing structural cracking caused by uneven heat distribution.

[0013] One-third of the coal mills have pulverized coal conveying pipes connected to a main pipeline. One end of the main pipeline is connected to the pulverized coal conveying pipe, and the other end is connected to two low-load pulverized coal conveying pipes. The ends of the two low-load pulverized coal conveying pipes are connected to two low-load pulverized coal burners. Valves are installed on the pulverized coal conveying pipes between the main pipeline and the pulverized coal burners, and valves are installed on the main pipeline. This allows for the supply of pulverized coal to several low-load pulverized coal burners by operating only two coal mills under low-load conditions, thereby achieving a minimum boiler operating load of 30% and improving boiler operating efficiency.

[0014] Other advantages, objectives, and features of this invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination and study, or may be learned from practice of this invention. The objectives and other advantages of this invention can be realized and obtained through the following description. Attached Figure Description

[0015] To make the objectives, technical solutions, and advantages of this utility model clearer, the following will describe this utility model in further detail with reference to the accompanying drawings, wherein:

[0016] Figure 1 This is a side view of the present invention.

[0017] Figure 2This is a top view showing the arrangement of 24 pulverized coal burners and 16 low-load pulverized coal burners on the furnace body according to this utility model.

[0018] In the diagram: 1. Furnace body; 2. Front radiant arch area; 3. Pulverized coal burner; 4. Rear radiant arch area; 5. Pulverized coal conveying pipe; 6. Pulverized coal supply system; 7. Low-load pulverized coal burner; 8. Main pipeline; 9. Low-load pulverized coal conveying pipe; 10. Valve; 11. Front F-air zone; 12. Rear F-air zone. Detailed Implementation

[0019] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the preferred embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0020] Example 1

[0021] like Figure 1-2 The W-type flame boiler shown is capable of stable combustion under low load conditions. Its main body is the furnace body 1, which has a front radiant arch zone 2 and a rear radiant arch zone 4. Twelve pulverized coal burners 3 (e.g., ...) are evenly spaced along the transverse direction of the front radiant arch zone 2 of the furnace body 1. Figure 2 In the furnace body 1, 12 pulverized coal burners 3 are evenly spaced along its transverse direction on the rear radiant arch area 4 (e.g., A1, B1, A2, B2, A3, B3, A4, B4, C1, D1, C2, D2). Figure 2 The feed inlets of each pulverized coal burner 3 (C3, D3, C4, D4, E1, F1, E2, F2, E3, F3, E4, F4) are connected to the pulverized coal supply system 6 via pulverized coal conveying pipes 5. The pulverized coal supply system 6 is a coal mill or a pulverized coal silo equipped with a fan. Specifically, pulverized coal burners A1, A2, A3, and A4 are connected to coal mill A via pulverized coal conveying pipes 5; pulverized coal burners B1, B2, B3, and B4 are connected to coal mill B via pulverized coal conveying pipes 5; pulverized coal burners C1, C2, and C3 are connected to coal mill B via pulverized coal conveying pipes 5. C3 and C4 are connected to the C pulverizer via pulverized coal conveying pipe 5; pulverized coal burners D1, D2, D3, and D4 are connected to the D pulverizer via pulverized coal conveying pipe 5; pulverized coal burners E1, E2, E3, and E4 are connected to the E pulverizer via pulverized coal conveying pipe 5; pulverized coal burners F1, F2, F3, and F4 are connected to the F pulverizer via pulverized coal conveying pipe 5; the improvement of this embodiment is that multiple low-load pulverized coal burners 7 (e.g., ...) are arranged at uniform intervals along the transverse direction of the front radial arch area 2 on the front radial arch area 2. Figure 2 In the A1-1, A1-2, A2-1, A2-2, A3-1, A3-2, A4-1, and A4-2 sections, multiple low-load pulverized coal burners 7 are evenly spaced laterally along the rear radial arch area 4. Figure 2The components B1-1, B1-2, A2-1, B2-2, B3-1, B3-2, B4-1, and B4-2 are provided in the low-load pulverized coal burner 7. A solid fuel stable ignition device is provided in the combustion cavity. The solid fuel stable ignition device adopts the structure disclosed in the patent for a device that can achieve stable ignition of solid fuel (publication number: 220397587U). It uses pure oxygen to ignite pulverized coal. The combustion cavity is connected to the burner nozzle 7. A low-load pulverized coal conveying pipe 9 is provided on the low-load pulverized coal burner 7 and is connected to the combustion cavity. Specifically, the four pulverized coal conveying pipes 5 on the A coal mill are each connected to a main pipe 8 via a tee connector. The end of each main pipe 8 is connected to two low-load pulverized coal conveying pipes 9 via tee connectors (the diameter of the main pipe 8 is the same as that of the pulverized coal conveying pipes 5, and the diameter of the low-load pulverized coal conveying pipes 9 is half the diameter of the main pipe 8). A valve 10 is installed on the pulverized coal conveying pipe 5 between the main pipe 8 and the pulverized coal burner 3. This means that the A coal mill can simultaneously power eight low-load pulverized coal burners 7 (e.g., ...). Figure 2 The B coal mill supplies pulverized coal to 8 low-load pulverized coal burners 7 (A1-1, A1-2, A2-1, A2-2, A3-1, A3-2, A4-1, A4-2). Four pulverized coal conveying pipes 5 on the B coal mill are each connected to a main pipe 8 via a tee connector. Each main pipe 8 has two low-load pulverized coal conveying pipes 9 connected to its end via a tee connector (the diameter of the main pipe 8 is the same as that of the pulverized coal conveying pipes 5, and the diameter of the low-load pulverized coal conveying pipes 9 is half the diameter of the main pipe 8). A valve 10 is installed on the pulverized coal conveying pipe 5 between the main pipe 8 and the pulverized coal burner 3. This means that the B coal mill can simultaneously supply pulverized coal to 8 low-load pulverized coal burners 7 (e.g., A1-1, A1-2, A2-1, A2-2, A3-1, A3-2, A4-1, A4-2). Figure 2 Coal powder is supplied from B1-1, B1-2, A2-1, B2-2, B3-1, B3-2, B4-1, and B4-2.

[0022] When the W-type flame boiler is operating at high load, valves 10 on all pulverized coal conveying pipes 5 are opened while valves 10 on all main pipes 8 are closed, and the ABCDEF coal mills are started, supplying pulverized coal to each pulverized coal burner 3. When the W-type flame boiler is operating at low load, valves 10 on the main pipes 8 are opened while valves 10 on the pulverized coal conveying pipes 5 are closed, the AB mill is running, the CDEF mills are shut down, and the AB mill is running. Pulverized coal enters each low-load pulverized coal burner 7, where it is ignited by the solid fuel stabilizing ignition device. Therefore, the low-load pulverized coal burner 7 supplies pulverized coal to the furnace. The inner cavity of boiler body 1 is injected with fire instead of pulverized coal, which ensures stable combustion of the W-type flame boiler under low load conditions. This eliminates the need for large oil guns to inject diesel fuel into the furnace for combustion assistance under low load conditions, saving operating costs. In addition, the low-load pulverized coal burners 7 on the front radiant arch area 2 and the rear radiant arch area 4 of boiler body 1 are evenly spaced, which ensures uniform heating of boiler body 1 and reduces the risk of structural fatigue. Under low load conditions, only two coal mills need to be operated to supply pulverized coal to 16 low-load pulverized coal burners 7, thereby achieving a minimum operating load of 30% for the boiler and improving boiler operating efficiency.

[0023] Example 2

[0024] The difference from Embodiment 1 is that: a front F-air zone 11 and a rear F-air zone 12 are provided on the furnace body 1. Multiple low-load pulverized coal burners 7 are arranged at uniform intervals along the lateral side of the front F-air zone 11 on the front F-air zone 11, and multiple low-load pulverized coal burners 7 are arranged at uniform intervals along the lateral side of the rear F-air zone 12 on the rear F-air zone 12. That is, the only difference between Embodiment 2 and Embodiment 1 is the arrangement position of the low-load pulverized coal burners.

[0025] It should be noted that: the pulverized coal burners 3 and the low-load pulverized coal burners 7 do not necessarily have to be arranged in the above order, and can be arranged in any other order; the low-load pulverized coal burners 7 are not limited to being supplied with pulverized coal by coal mill A and coal mill B, and can be supplied with pulverized coal by any two coal mills; the low-load pulverized coal burners 7 are not limited to being supplied with pulverized coal by coal mill 6, which supplies pulverized coal to pulverized coal burners 3, and can be supplied with pulverized coal by an independent pulverized coal supply system 6.

[0026] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of this utility model without departing from the spirit and scope of this technical solution, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.

Claims

1. A W-type flame boiler capable of stable combustion under low load conditions, comprising a furnace body (1), a front radiant arch area (2) and a rear radiant arch area (4) provided on the furnace body (1), and a plurality of pulverized coal burners (3) uniformly spaced laterally on the front radiant arch area (2) and the rear radiant arch area (4), wherein the feed inlet of the pulverized coal burner (3) is connected to a pulverized coal supply system (6) through a pulverized coal conveying pipe (5), characterized in that: A low-load pulverized coal burner (7) is provided on the furnace body (1). A combustion cavity is provided on the low-load pulverized coal burner (7). A solid fuel stabilizing ignition device is provided in the combustion cavity. The combustion cavity is connected to the inner cavity of the furnace body (1). A low-load pulverized coal conveying pipe (9) is provided on the low-load pulverized coal burner (7) and is connected to the combustion cavity. The low-load pulverized coal conveying pipe (9) is connected to the pulverized coal supply system (6).

2. The W-type flame boiler capable of stable combustion under low load conditions according to claim 1, characterized in that: The low-load pulverized coal burners (7) are a number and are divided into two groups. The two groups of low-load pulverized coal burners (7) are respectively set on the front radiation arch area (2) and the rear radiation arch area (4) or on the front F wind area and the rear F wind area.

3. The W-type flame boiler capable of stable combustion under low load conditions according to claim 2, characterized in that: A group of multiple low-load pulverized coal burners (7) on the front radiating arch area (2) are evenly spaced laterally along the front radiating arch area (2), and a group of multiple low-load pulverized coal burners (7) on the rear radiating arch area (4) are evenly spaced laterally along the rear radiating arch area (4).

4. The W-type flame boiler capable of stable combustion under low load conditions according to claim 1, characterized in that: The pulverized coal supply system (6) is a coal mill, and four pulverized coal burners (3) are connected to a coal mill through a pulverized coal conveying pipe (5).

5. The W-type flame boiler capable of stable combustion under low load conditions according to claim 4, characterized in that: One-third of the coal mills have a main pipeline (8) connected to each coal powder conveying pipe (5). One end of the main pipeline (8) is connected to the coal powder conveying pipe (5), and the other end is connected to two low-load coal powder conveying pipes (9). The ends of the two low-load coal powder conveying pipes (9) are connected to two low-load coal powder burners (7). A valve (10) is provided on the coal powder conveying pipe (5) between the main pipeline (8) and the coal powder burner (3). A valve (10) is provided on the main pipeline (8).

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