An ultra-low load combustion device adapted to a tangentially fired boiler

Abstract

An ultra-low load combustion device adapted to tangentially fired boilers, which relates to the technical field of combustion boilers, specifically an ultra-low load combustion device adapted to tangentially fired boilers. The present invention protects the ultra-low load combustion device: adding a layer of low-capacity pulverized coal burners above the original top-layer primary air burners, and adding a layer of secondary air nozzles above the low-capacity pulverized coal burners; adding a small-capacity pulverized coal feeding device, and the small-capacity pulverized coal feeding device is connected to the low-capacity pulverized coal burners - and other 5 kinds of tangentially fired boiler retrofit structures. The ultra-low load combustion device of the present invention can achieve long-term stable operation of the boiler at 15% of the rated load and below without any auxiliary combustion aids such as oil, gas, plasma, and oxygen enrichment.

Description

Technical Field

[0001] The present invention relates to the technical field of combustion boilers, and particularly to an ultra-low load combustion device suitable for tangentially fired boilers. Background Art

[0002] At present, thermal power units, as the main peak shaving power sources in China, are actively undergoing in-depth peak shaving transformation to fully tap the peak shaving potential of thermal power units, which is of great significance for alleviating the current peak shaving pressure in China, accommodating more renewable energy power, and promoting the transformation of China's power structure.

[0003] In existing thermal power coal-fired units, tangentially fired boilers are equipped with 4 - 7 (or even more) primary air burners and several secondary air burners. Even if the tangentially fired boiler is transformed, the maximum stable operation can only be achieved at 40% of the rated load, and it is impossible to further reduce the load for operation. Summary of the Invention

[0004] The purpose of the present invention is to provide an ultra-low load combustion device suitable for tangentially fired boilers, which can achieve long-term stable operation at 15% of the rated load and below 15% of the rated load without any auxiliary combustion aids such as oil, gas, plasma, and oxygen enrichment.

[0005] The ultra-low load combustion device of the present invention suitable for tangentially fired boilers one:

[0006] Add a layer of low-capacity pulverized coal burners (F) above the original topmost primary air burners, and add a layer of secondary air nozzles above the low-capacity pulverized coal burners; a new small-capacity pulverized coal feeding device is added, and the small-capacity pulverized coal feeding device is connected to the low-capacity pulverized coal burners.

[0007] When the boiler is at ultra-low load (≤15% of the rated load), only the low-capacity pulverized coal burners (and the small-capacity pulverized coal feeding device) and the added secondary air nozzles operate; when the boiler load > 15% of the rated load, the low-capacity pulverized coal burners (and the small-capacity pulverized coal feeding device) and the added secondary air nozzles stop operating (maintaining ventilation and cooling), and other burners operate as normal.

[0008] The ultra-low load combustion device of the present invention suitable for tangentially fired boilers two:

[0009] Add a layer of low-capacity pulverized coal burners (F) above the original topmost primary air burners, and add a layer of secondary air nozzles above the low-capacity pulverized coal burners; the pulverized coal conveying pipeline at the outlet of the coal mill corresponding to the original topmost primary air burners (E) is transformed into a three-way two-outlet; one way supplies pulverized coal to the low-capacity pulverized coal burners (F) through a pulverized coal pipeline and a stop baffle valve, and the other way supplies pulverized coal to the original topmost primary air burners (E) through a pulverized coal pipeline and a stop baffle valve.

[0010] When the above ultra-low load combustion device is at the ultra-low load of the boiler (≤15% of the rated load), only the low-capacity pulverized coal burners (and the corresponding coal conveying pipelines) and the added secondary air nozzles operate; when the boiler load > 15% of the rated load, the low-capacity pulverized coal burners (and the corresponding coal conveying pipelines) and the added secondary air nozzles stop operating, and another path through the pulverized coal pipeline and the stop baffle door supplies pulverized coal to the original topmost primary air burner (E), and other burners operate as normal.

[0011] The ultra-low load combustion device of the present invention applicable to tangential boilers III:

[0012] Add a layer of low-capacity pulverized coal burners (F) above the original topmost primary air burner, and add a layer of secondary air nozzles above the low-capacity pulverized coal burners; add a small-capacity pulverized coal feeding device, and the small-capacity pulverized coal feeding device is connected to the low-capacity pulverized coal burners; the original topmost primary air burner (E) is transformed into a staged low-capacity pulverized coal burner, and the staged low-capacity pulverized coal burner is composed of two upper and lower low-capacity pulverized coal burners; the coal conveying pipeline at the outlet of the coal mill corresponding to the original topmost primary air burner (E) is transformed into a three-way with two outlets; one path passes through the pulverized coal pipeline and the stop baffle door to supply pulverized coal to one of the low-capacity pulverized coal burners (E2 or E1) in the staged low-capacity pulverized coal burner, and the other path passes through the pulverized coal pipeline and the stop baffle door and then cooperates with the three-way of the front-of-furnace pulverized coal pipeline to supply pulverized coal to the upper and lower layers of low-capacity pulverized coal burners (E2 and E1) simultaneously.

[0013] When the above ultra-low load combustion device is at the ultra-low load of the boiler (≤15% of the rated load), only the low-capacity pulverized coal burners (and the corresponding coal conveying pipelines), one of the low-capacity pulverized coal burners (E2 or E1) in the staged low-capacity pulverized coal burner and the added secondary air nozzles operate; when the boiler load > 15% of the rated load, the low-capacity pulverized coal burners (and the corresponding coal conveying pipelines), the coal conveying pipeline of the independent one of the low-capacity pulverized coal burners in the staged low-capacity pulverized coal burner and the added secondary air nozzles stop operating, and another path through the pulverized coal pipeline and the stop baffle door and then cooperates with the three-way of the front-of-furnace pulverized coal pipeline to supply pulverized coal to the upper and lower layers of low-capacity pulverized coal burners E2 and E1 simultaneously, and other burners operate as normal.

[0014] The ultra-low load combustion device of the present invention applicable to tangential boilers IV:

[0015] One layer of the primary air burners in the original primary air burners is transformed into a staged low-capacity pulverized coal burner, and the staged low-capacity pulverized coal burner is composed of two upper and lower low-capacity pulverized coal burners; the pulverized coal conveying pipeline at the outlet of the coal mill corresponding to the transformed layer of primary air burners is transformed into a three-way two-outlet pipeline; the first path passes through the pulverized coal pipeline and the stop baffle valve to supply pulverized coal to one layer of low-capacity pulverized coal burners in the staged low-capacity pulverized coal burner, and this layer of low-capacity pulverized coal burner is an independent layer of low-capacity pulverized coal burner; the second path passes through the pulverized coal pipeline and the stop baffle valve and then cooperates with the three-way of the pulverized coal pipeline in front of the furnace to supply pulverized coal to the upper and lower two layers of low-capacity pulverized coal burners at the same time;

[0016] The pulverized coal conveying pipeline at the outlet of the coal mill corresponding to the primary air burner in the layer adjacent to the transformed layer is transformed into a three-way two-outlet pipeline. The first path passes through the pulverized coal pipeline and the stop baffle valve to supply pulverized coal to the non-independent layer of low-capacity pulverized coal burners in the staged low-capacity pulverized coal burner, and the second path passes through the pulverized coal pipeline and the stop baffle valve to supply pulverized coal to the primary air burner in this adjacent layer.

[0017] When the above ultra-low load combustion device is at the ultra-low load (≤15% of the rated load) of the boiler, only the first pulverized coal conveying pipeline and the first path of the pulverized coal conveying pipeline in the transformed layer are operated, that is, they supply pulverized coal to the upper and lower two layers of low-capacity pulverized coal burners respectively; when the boiler load > 15% of the rated load, the first pulverized coal conveying pipeline and the first path of the pulverized coal conveying pipeline in the transformed layer are stopped, the second pulverized coal conveying pipeline in the transformed layer and the second path of the pulverized coal conveying pipeline in the adjacent layer are opened, and other burners are operated as normal.

[0018] The ultra-low load combustion device of the present invention is applicable to the ultra-low load combustion device of a tangentially fired boiler V:

[0019] Two adjacent layers of primary air burners in the original primary air burners are both transformed into staged low-capacity pulverized coal burners, and the staged low-capacity pulverized coal burner is composed of two upper and lower low-capacity pulverized coal burners; the pulverized coal conveying pipelines at the outlets of the coal mills corresponding to the primary air burners in the transformed layers are all transformed into three-way two-outlet pipelines; for each layer in the transformed layer, the first path passes through the pulverized coal pipeline and the stop baffle valve to supply pulverized coal to one layer of low-capacity pulverized coal burners in the staged low-capacity pulverized coal burner, and this layer of low-capacity pulverized coal burner is an independent layer of low-capacity pulverized coal burner; for each layer in the transformed layer, the second path passes through the pulverized coal pipeline and the stop baffle valve and then cooperates with the three-way of the pulverized coal pipeline in front of the furnace to supply pulverized coal to the upper and lower two layers of low-capacity pulverized coal burners in this layer at the same time.

[0020] When the above ultra-low load combustion device is at the ultra-low load (≤15% of the rated load) of the boiler, only the first pulverized coal conveying pipelines in the two transformed layers are operated, that is, they supply pulverized coal to the two independent layers of low-capacity pulverized coal burners in the two transformed layers; when the boiler load > 15% of the rated load, the first pulverized coal conveying pipelines in the two transformed layers are stopped, the second pulverized coal conveying pipelines in the two transformed layers are opened, and other burners are operated as normal.

[0021] In the present invention, a corresponding coal supply, cold and hot air system is provided for the small-capacity pulverized coal feeding device, and an air box air duct and a water-cooled wall are provided for the low-capacity pulverized coal burner. Low-capacity pulverized coal burner: It is a pulverized coal burner with a nozzle and a capacity smaller than that of the burner. Small-capacity pulverized coal feeding device: It includes a coal mill with a smaller output, a corresponding coal supply, cold and hot air systems, and a powder delivery pipeline. The powder delivery pipeline includes a pulverized coal pipeline and a stop baffle valve. The powder output capacity of the independent small-capacity pulverized coal feeding device is adjustable, which can meet the flexible operation requirements under ultra-low load. After the small-capacity pulverized coal feeding device stops operating, the low-capacity pulverized coal burner is forced to be cooled by air distribution to ensure its high-temperature burn resistance performance when operating above 15% of the rated load of the unit.

[0022] The small-capacity pulverized coal feeding device delivers fine and uniform pulverized coal. The heat capacity of small particle clusters in its pulverized coal cloud is small, which can be quickly heated to the ignition temperature, thus ensuring adjustable output and providing a pulverized coal cloud with good fineness and uniformity, providing the best conditions for the complete combustion of pulverized coal during the ultra-low load operation of the boiler.

[0023] During ultra-low load operation, the coal consumption of the unit (boiler) decreases sharply. The original conventional burner nozzles are relatively large, which cannot ensure the speed, ignition temperature, rigidity, and combustion stability of the pulverized coal in the burner. However, the low-capacity pulverized coal burner in the present invention has a low heat capacity and requires less heat for ignition, can ensure the speed of the pulverized coal in the burner and ignite quickly, and has a good burnout effect, enabling efficient and stable combustion of pulverized coal.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. The present invention realizes the stable operation of a tangentially fired boiler at an ultra-low load of 15% of the rated load and below without any auxiliary combustion aids.

[0026] 2. The low-capacity pulverized coal burner has a low heat capacity, can ignite quickly, and has strong low-load stability.

[0027] 3. The low-capacity pulverized coal burner has an independent powder delivery pipeline, which can be flexibly switched according to the load change.

[0028] 4. The operating indicators of the boiler modified by the present invention are not lower than the pre-modification operating level, and it is ensured that the boiler can operate efficiently, safely, stably, and environmentally friendly for a long time. Brief Description of the Drawings

[0029] Figure 1 It is a schematic structural diagram of Embodiments 1 and 2 of the present invention;

[0030] Figure 2 It is a schematic structural diagram of Embodiments 3 and 4 of the present invention;

[0031] Figure 3Schematic diagram of the structure of Embodiment 5 of the present invention;

[0032] Figure 4 Schematic diagram of the structure of Embodiment 6 of the present invention; Detailed implementation manners

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] Embodiment 1:

[0035] This embodiment is applicable to the ultra-low load combustion device of a tangentially fired boiler:

[0036] Add a layer of low-capacity pulverized coal burners (F) above the original top-layer primary air burners, and add a layer of secondary air nozzles above the low-capacity pulverized coal burners; a new small-capacity pulverized coal feeding device is added, and the small-capacity pulverized coal feeding device is connected to the low-capacity pulverized coal burners. The comparison before and after the transformation of the tangentially fired boiler is as Figure 1 shown.

[0037] When the ultra-low load combustion device of this embodiment is at the ultra-low load (≤15% of the rated load) of the boiler, only the low-capacity pulverized coal burners (and the small-capacity pulverized coal feeding device) and the added secondary air nozzles operate; when the boiler load > 15% of the rated load, stop the operation of the low-capacity pulverized coal burners (and the small-capacity pulverized coal feeding device) and the added secondary air nozzles, and operate other burners as normal.

[0038] Embodiment 2:

[0039] This embodiment is applicable to the ultra-low load combustion device of a tangentially fired boiler:

[0040] Add a layer of low-capacity pulverized coal burners (F) above the original top-layer primary air burners, and add a layer of secondary air nozzles above the low-capacity pulverized coal burners; transform the pulverized coal conveying pipeline at the outlet of the coal mill corresponding to the original top-layer primary air burners (E) into a three-way two-way outlet; one way supplies pulverized coal to the low-capacity pulverized coal burners (F) through the pulverized coal pipeline and the stop baffle valve, and the other way supplies pulverized coal to the original top-layer primary air burners (E) through the pulverized coal pipeline and the stop baffle valve. The comparison before and after the transformation of the tangentially fired boiler is as Figure 1 shown.

[0041] In the ultra-low load combustion device of this embodiment, when the boiler is at ultra-low load (≤15% of the rated load), only the low-capacity pulverized coal burners (and the corresponding coal powder feeding pipelines) and the added secondary air nozzles operate; when the boiler load > 15% of the rated load, the low-capacity pulverized coal burners (and the corresponding coal powder feeding pipelines) and the added secondary air nozzles stop operating, and another path is opened to supply pulverized coal to the original topmost primary air burner (E) through the coal powder pipeline and the shut-off damper, and other burners operate as normal.

[0042] Embodiment 3:

[0043] The ultra-low load combustion device of this embodiment is applicable to a tangentially fired boiler:

[0044] One layer of low-capacity pulverized coal burners (F) is added above the original topmost primary air burner, and one layer of secondary air nozzles is added above the low-capacity pulverized coal burners; a small-capacity pulverized coal feeding device is added, and the small-capacity pulverized coal feeding device is connected to the low-capacity pulverized coal burners; the original topmost primary air burner (E) is transformed into a staged low-capacity pulverized coal burner, and the staged low-capacity pulverized coal burner is composed of two upper and lower low-capacity pulverized coal burners; the pulverized coal feeding pipeline at the outlet of the coal mill corresponding to the original topmost primary air burner (E) is transformed into a three-way with two outlets; one path passes through the coal powder pipeline and the shut-off damper to supply pulverized coal to one layer of the low-capacity pulverized coal burners (E2) in the staged low-capacity pulverized coal burner, and the other path passes through the coal powder pipeline and the shut-off damper and then cooperates with the three-way of the front-of-furnace coal powder pipeline to supply pulverized coal to the upper and lower layers of low-capacity pulverized coal burners (E2 and E1) simultaneously. The comparison before and after the transformation of the tangentially fired boiler is as Figure 2 shown.

[0045] In the ultra-low load combustion device of this embodiment, when the boiler is at ultra-low load (≤15% of the rated load), only the low-capacity pulverized coal burners (and the corresponding coal powder feeding pipelines), one layer of the low-capacity pulverized coal burners (E2) in the staged low-capacity pulverized coal burner, and the added secondary air nozzles operate; when the boiler load > 15% of the rated load, the low-capacity pulverized coal burners (and the corresponding coal powder feeding pipelines), the coal powder feeding pipelines of the independent one layer of the low-capacity pulverized coal burners in the staged low-capacity pulverized coal burner, and the added secondary air nozzles stop operating, and another path is opened to supply pulverized coal to the upper and lower layers of low-capacity pulverized coal burners E2 and E1 simultaneously through the coal powder pipeline and the shut-off damper and then cooperating with the three-way of the front-of-furnace coal powder pipeline, and other burners operate as normal.

[0046] The three-way of the coal powder pipeline is a pipeline three-way applicable to the coal powder pipeline.

[0047] Embodiment 4:

[0048] The ultra-low load combustion device of this embodiment is applicable to a tangentially fired boiler:

[0049] A low-capacity pulverized coal burner (F) is added above the original topmost primary air burner, and a secondary air nozzle is added above the low-capacity pulverized coal burner; a small-capacity pulverized coal feeding device is newly added, and the small-capacity pulverized coal feeding device is connected to the low-capacity pulverized coal burner; the original topmost primary air burner (E) is transformed into a staged low-capacity pulverized coal burner, and the staged low-capacity pulverized coal burner is composed of two upper and lower low-capacity pulverized coal burners; the pulverized coal conveying pipeline at the outlet of the coal mill corresponding to the original topmost primary air burner (E) is transformed into a three-way two-outlet pipeline; one way passes through the pulverized coal pipeline and the stop baffle valve to supply pulverized coal to one of the low-capacity pulverized coal burners (E1) in the staged low-capacity pulverized coal burner, and the other way passes through the pulverized coal pipeline and the stop baffle valve and then cooperates with the three-way of the pulverized coal pipeline in front of the furnace to supply pulverized coal to the upper and lower two low-capacity pulverized coal burners (E2 and E1) simultaneously. The comparison before and after the transformation of the tangential-firing boiler is as follows Figure 2 as shown

[0050] In the ultra-low load combustion device of this embodiment, when the boiler is at ultra-low load (≤15% of the rated load), only the low-capacity pulverized coal burner (and the corresponding pulverized coal conveying pipeline), one of the low-capacity pulverized coal burners (E1) in the staged low-capacity pulverized coal burner and the added secondary air nozzle operate; when the boiler load > 15% of the rated load, stop operating the low-capacity pulverized coal burner (and the corresponding pulverized coal conveying pipeline), the pulverized coal conveying pipeline of the independent low-capacity pulverized coal burner in the staged low-capacity pulverized coal burner, and the added secondary air nozzle, and open the other way that passes through the pulverized coal pipeline and the stop baffle valve and then cooperates with the three-way of the pulverized coal pipeline in front of the furnace to supply pulverized coal to the upper and lower two low-capacity pulverized coal burners E2 and E1 simultaneously, and operate other burners as normal

[0051] Example 5:

[0052] The ultra-low load combustion device adapted to the tangential-firing boiler in this embodiment:

[0053] One of the primary air burners (E layer) in the original primary air burner is transformed into a staged low-capacity pulverized coal burner (E1 layer and E2 layer), and the staged low-capacity pulverized coal burner is composed of two upper and lower low-capacity pulverized coal burners; the pulverized coal conveying pipeline at the outlet of the coal mill of the transformed primary air burner is transformed into a three-way two-outlet pipeline; the first way passes through the pulverized coal pipeline and the stop baffle valve to supply pulverized coal to one of the low-capacity pulverized coal burners (E1) in the staged low-capacity pulverized coal burner, and this low-capacity pulverized coal burner is an independent low-capacity pulverized coal burner; the second way passes through the pulverized coal pipeline and the stop baffle valve and then cooperates with the three-way of the pulverized coal pipeline in front of the furnace to supply pulverized coal to the upper and lower two low-capacity pulverized coal burners (E1 and E2) simultaneously

[0054] The pulverized coal delivery pipeline corresponding to the primary air burner (D layer) on the layer adjacent to the modified layer is modified into a three-way with two outlets. The first path passes through the pulverized coal pipeline and the stop baffle valve to supply pulverized coal to the low-capacity pulverized coal burner (E2) in the non-independent layer of the classified low-capacity pulverized coal burner. The second path passes through the pulverized coal pipeline and the stop baffle valve to supply pulverized coal to the primary air burner (D layer) on this adjacent layer. The comparison before and after the modification of the tangential boiler is as follows Figure 3 as shown.

[0055] In the ultra-low load combustion device of this embodiment, when the boiler is at ultra-low load (≤15% of the rated load), only the first pulverized coal delivery pipeline and the first path of the pulverized coal delivery pipeline in the modified layer are operated, that is, supplying pulverized coal to the upper and lower low-capacity pulverized coal burners respectively; when the boiler load > 15% of the rated load, stop operating the first pulverized coal delivery pipeline and the first path of the pulverized coal delivery pipeline in the modified layer, open the second pulverized coal delivery pipeline in the modified layer and the second path of the pulverized coal delivery pipeline on the adjacent layer, and operate other burners as normal.

[0056] The modified layer in this embodiment can be any layer (A, B, C, D or E layer).

[0057] Embodiment 6:

[0058] The ultra-low load combustion device of this embodiment is applicable to the tangential boiler:

[0059] The primary air burners in two adjacent layers (D layer and E layer) in the original primary air burners are both modified into classified low-capacity pulverized coal burners. The classified low-capacity pulverized coal burners are both composed of 2 upper and lower low-capacity pulverized coal burners (D1, D2, E1, E2 layers respectively); the pulverized coal delivery pipelines corresponding to the primary air burners in the modified layer are all modified into three-ways with two outlets; the first path of each layer in the modified layer passes through the pulverized coal pipeline and the stop baffle valve to supply pulverized coal to one layer of the low-capacity pulverized coal burner (D2 and E1 respectively) in the classified low-capacity pulverized coal burner, and this layer of low-capacity pulverized coal burner is an independent low-capacity pulverized coal burner; the second path of each layer in the modified layer passes through the pulverized coal pipeline and the stop baffle valve and then cooperates with the three-way of the pulverized coal pipeline in front of the furnace to supply pulverized coal to the upper and lower low-capacity pulverized coal burners (E1 and E2; D1 and D2) on this layer at the same time. The comparison before and after the modification of the tangential boiler is as follows Figure 4 as shown.

[0060] In the ultra-low load combustion device of this embodiment, when the boiler is at ultra-low load (≤15% of the rated load), only the first pulverized coal delivery pipelines in the two modified layers are operated, that is, supplying pulverized coal to the 2 independent low-capacity pulverized coal burners (D2 and E1) in the two modified layers; when the boiler load > 15% of the rated load, stop operating the first pulverized coal delivery pipelines in the two modified layers, open the second pulverized coal delivery pipelines in the two modified layers, and operate other burners as normal.

[0061] In this embodiment, the modified layer can be any adjacent layers (A and B, B and C, C and D, D and E).

[0062] In Embodiments 1 to 6, a corresponding coal supply, hot and cold air system is provided for the small-capacity pulverized coal feeding device, and a wind box air duct and water-cooled wall are provided for the low-capacity pulverized coal burner. Low-capacity pulverized coal burner: It is a pulverized coal burner with a nozzle and a capacity smaller than that of the burner. Small-capacity pulverized coal feeding device: It includes a coal mill with a smaller output, a corresponding coal supply, hot and cold air systems, and a powder delivery pipeline. The powder delivery pipeline includes a pulverized coal pipeline and a stop baffle valve. The powder output capacity of the independent small-capacity pulverized coal feeding device is adjustable, which can meet the flexible operation requirements under ultra-low load. After the small-capacity pulverized coal feeding device stops operating, air distribution is carried out to forcibly cool the set low-capacity pulverized coal burner to ensure its high-temperature burn resistance performance when operating above 15% of the rated load of the unit.

[0063] In Embodiments 1 to 6, the ultra-low load combustion device can quickly ignite without any auxiliary combustion aids when the boiler is under ultra-low load, and achieve long-term efficient, safe and stable operation.

[0064] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

Claims

1. An ultra-low load combustion device adapted to a tangentially fired boiler, characterized in that: A layer of low-capacity pulverized coal burners (F) is added above the original topmost primary air burners, and a layer of secondary air nozzles is added above the low-capacity pulverized coal burners; a new small-capacity pulverized coal feeding device is added, and the small-capacity pulverized coal feeding device is connected to the low-capacity pulverized coal burners; the original topmost primary air burners (E) are transformed into staged low-capacity pulverized coal burners, and the staged low-capacity pulverized coal burners are composed of two upper and lower low-capacity pulverized coal burners; the pulverized coal conveying pipeline at the outlet of the coal mill corresponding to the original topmost primary air burners (E) is transformed into a three-way two-outlet pipeline; one way passes through the pulverized coal pipeline and the stop baffle valve to supply pulverized coal to one of the low-capacity pulverized coal burners in the staged low-capacity pulverized coal burners (E2 or E1), and the other way passes through the pulverized coal pipeline and the stop baffle valve and then cooperates with the three-way on the pulverized coal pipeline in front of the furnace to supply pulverized coal to the upper and lower layers of low-capacity pulverized coal burners (E2 and E1) simultaneously.

2. An ultra-low load combustion device adapted to a tangentially fired boiler, characterized in that: One of the primary air burners in the original primary air burners is transformed into a staged low-capacity pulverized coal burner, and the staged low-capacity pulverized coal burner is composed of two upper and lower low-capacity pulverized coal burners; the pulverized coal conveying pipeline at the outlet of the coal mill corresponding to the transformed primary air burner is transformed into a three-way two-outlet pipeline; the first way passes through the pulverized coal pipeline and the stop baffle valve to supply pulverized coal to one of the low-capacity pulverized coal burners in the staged low-capacity pulverized coal burner, and this low-capacity pulverized coal burner is an independent low-capacity pulverized coal burner; The second way passes through the pulverized coal pipeline and the stop baffle valve and then cooperates with the three-way on the pulverized coal pipeline in front of the furnace to supply pulverized coal to the upper and lower layers of low-capacity pulverized coal burners simultaneously; The pulverized coal conveying pipeline at the outlet of the coal mill corresponding to the primary air burner in the layer adjacent to the transformed layer is transformed into a three-way two-outlet pipeline. The first way passes through the pulverized coal pipeline and the stop baffle valve to supply pulverized coal to the non-independent low-capacity pulverized coal burner in the staged low-capacity pulverized coal burner, and the second way passes through the pulverized coal pipeline and the stop baffle valve to supply pulverized coal to the primary air burner in this adjacent layer.

3. An ultra-low load combustion device adapted to a tangentially fired boiler, characterized in that: Two adjacent layers of primary air burners in the original primary air burners are both transformed into staged low-capacity pulverized coal burners, and the staged low-capacity pulverized coal burners are composed of two upper and lower low-capacity pulverized coal burners; the pulverized coal conveying pipelines at the outlets of the coal mills corresponding to the primary air burners in the transformed layers are all transformed into three-way two-outlet pipelines; for each layer in the transformed layers, the first way passes through the pulverized coal pipeline and the stop baffle valve to supply pulverized coal to one of the low-capacity pulverized coal burners in the staged low-capacity pulverized coal burner, and this low-capacity pulverized coal burner is an independent low-capacity pulverized coal burner; for each layer in the transformed layers, the second way passes through the pulverized coal pipeline and the stop baffle valve and then cooperates with the three-way on the pulverized coal pipeline in front of the furnace to supply pulverized coal to the upper and lower layers of low-capacity pulverized coal burners in this layer simultaneously.

Images