Tangent circle combustion system for combusting inferior coal and boiler

Abstract

The utility model discloses a tangential combustion system for burning inferior coal and a boiler, and belongs to the field of inferior coal blending combustion of tangential boilers of coal-fired thermal power generating units. Comprising combustors arranged on a hearth, a coal mill outlet powder pipe leading to the combustors, a rich-lean separation device arranged on the coal mill outlet powder pipe, a concentrated-phase coal powder pipe leading to the combustors on the same layer behind the rich-lean separation device, and exhaust air pipes capable of leading to D / E / F combustors respectively. When the combustion system combusts inferior coal under the working conditions of high load and medium load, rich-lean separation is not needed, and pulverized coal is combusted through a combustor on the same layer; when the combustion system combusts inferior coal under the low-load working condition, the rich-lean separation technology is adopted, exhaust gas is led to the D / E / F combustor of the upper combustion area to enter a hearth to be combusted, and dense-phase pulverized coal enters the combustor on the same layer to be stably combusted. By adjusting the running states of the rich-lean separation device and the exhaust gas pipeline, the safe and stable running of the boiler for burning the inferior coal under the full-load working condition is realized.

Description

Technical Field

[0001] The utility model belongs to the technical field of mixing and burning inferior coal in a tangentially fired boiler of a coal-fired thermal power unit, and relates to a tangentially fired combustion system and a boiler burning inferior coal. Background Art

[0002] Tangentially fired boilers are the main furnace type of coal-fired units. When tangentially fired boilers burning inferior coal are running at low load, as the amount of boiler fuel decreases, the number of operating pulverizing systems is reduced to less than 3. In order to meet the safe and stable operation of the coal mill, the primary air rate under low load conditions will increase significantly. In the current combustion system design, the pulverized coal pipe at the mill outlet corresponds one-to-one to the burner at a certain height. The concentration of the pulverized coal airflow at the mill outlet is exactly the same as the concentration of the pulverized coal airflow entering the furnace through the burner, and the concentration of the pulverized coal airflow entering the burner cannot be adjusted according to operating needs. In this way, under the condition of burning inferior coal at low load, the pulverized coal airflow will become difficult to ignite due to the increase in ignition heat due to the decrease in concentration, the boiler's stable combustion ability will decrease, and even unstable combustion will occur, affecting the safe and stable operation of the unit. Utility Model Content

[0003] The utility model aims to solve the problem in the prior art that it is difficult to stabilize the working condition of a tangentially fired boiler burning inferior coal at low load, and to provide a tangentially fired combustion system and a boiler burning inferior coal.

[0004] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0005] The utility model provides a tangential combustion system for burning inferior coal, comprising burners A, B, C, D, E and F installed on the furnace from bottom to top;

[0006] A powder return pipe is provided on each burner, a thick-lean separation device is provided on the powder return pipe of burner A or burner B, a dense-phase coal powder pipe connected with burner A or burner B is provided on the dense-lean separation device, and the other end of the dense-phase coal powder pipe is connected with an exhaust gas diversion structure leading to burner D, burner E and burner F.

[0007] Preferably, the exhaust gas diversion structure is an exhaust gas air main pipe.

[0008] Preferably, the exhaust air main pipe is respectively connected with burner exhaust air branch pipes leading to the D burner, the E burner and the F burner, and the other end of the burner exhaust air branch pipe is respectively connected with the D burner, the E burner and the F burner.

[0009] Preferably, a shut-off valve is provided on the burner exhaust gas branch pipe.

[0010] Preferably, the thick-lean separation device is a pipeline elbow separation device, a coal powder cyclone separation device, a swirl blade separation device or a shutter cone axial separation device.

[0011] Preferably, a first safety valve is provided on the powder return pipe.

[0012] Preferably, a second safety valve is provided at the outlet of the exhaust gas diversion structure.

[0013] Preferably, an exhaust gas air regulating valve is provided on the exhaust gas diversion structure.

[0014] A boiler comprises a plurality of coal mills, at least one outlet of which is connected to a tangential combustion system for burning low-quality coal.

[0015] Compared with the prior art, the utility model has the following beneficial effects:

[0016] The utility model proposes a tangential combustion system for burning inferior coal, wherein a burner and a corresponding return air pipe are provided on the furnace, a thick-thin separation device is provided on the return air pipe leading to the A burner or the B burner, for separating the concentration of the coal powder airflow, a dense phase coal powder pipe is provided on the thick-thin separation device, and one end of the dense phase coal powder pipe is connected to the A burner or the B burner, and the other end of the dense phase coal powder pipe is connected to the exhaust gas air main pipe, so as to lead the exhaust gas to the D burner, the E burner and the F burner respectively. When the combustion system burns inferior coal under high and medium load conditions, it is not necessary to perform thick-thin separation, and the coal powder is burned through the burners on the same layer; when the combustion system burns inferior coal under low load conditions, the thick-thin separation device is used to lead the exhaust gas to the D burner, the E burner and the F burner in the upper combustion zone to enter the furnace for combustion, and the dense phase coal powder enters the burners on the same layer for stable combustion. By adjusting the operating state of the thick-thin separation device and the exhaust gas air main pipe, the safe and stable operation of the boiler burning inferior coal under full load conditions is achieved. Therefore, the combustion system proposed in the utility model adopts a dense-lean separation device and reasonably arranges the exhaust gas position, ensuring that the boiler can adjust the concentration of the pulverized coal airflow entering the burner according to operating needs, thereby ensuring operating stability during low-load operation.

[0017] Furthermore, the exhaust air branch pipes of the burners connected to the D burner, the E burner and the F burner are respectively connected to the exhaust air main pipe in order to manage several branches.

[0018] Furthermore, a first safety valve is provided on the powder return pipe, and a second safety valve is provided on the outlet of the exhaust gas diversion structure, in order to make the tangential combustion system safer when working.

[0019] Furthermore, the exhaust gas air regulating valve is provided on the exhaust gas diversion structure in order to adjust the thick-thin separation ratio and the air / exhaust gas air ratio, and to change the burner flame shape and the flame center height. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the utility model and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 This is a structural diagram of a tangential-circle combustion system for burning inferior coal according to the utility model.

[0022] Among them: 1-burner, 2-powder return pipe, 3-thick and thin separation device, 4-dense phase coal powder pipe, 5-exhaust gas diversion structure, 6-shut-off valve, 7-burner exhaust gas wind branch pipe. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Generally, the components of the embodiments of the utility model described and shown in the drawings here can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the present invention to be protected, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0026] In the description of the embodiments of the present utility model, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the utility model product is usually placed when in use, it is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0027] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0028] In the description of the embodiments of the present utility model, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0029] The utility model is further described in detail below with reference to the accompanying drawings:

[0030] The utility model proposes a tangential combustion system for burning low-quality coal, such as Figure 1 As shown, it includes 1 installed on the furnace from bottom to top, and the burner 1 includes burners A burner, B burner, C burner, D burner, E burner and F burner; each burner is provided with a powder return pipe 2, and a thick-lean separation device 3 is provided on the powder return pipe 2 of burner A or burner B, and a dense-phase coal powder pipe 4 connected with burner A or burner B is provided on the dense-lean separation device 3, and the other end of the dense-phase coal powder pipe 4 is connected with an exhaust gas diversion structure 5 leading to burner D, burner E and burner F.

[0031] The exhaust gas flow distribution structure 5 is an exhaust gas main pipe. The exhaust gas main pipe is respectively connected with burner exhaust gas branch pipes 7 leading to the D burner, the E burner and the F burner. The other end of the burner exhaust gas branch pipe 7 is respectively connected to the D burner, the E burner and the F burner. The shut-off valve 6 is provided on the burner exhaust gas branch pipe 7 to manage the D burner, the E burner and the F burner.

[0032] A first safety valve is provided on the powder return pipe 2, and a second safety valve is provided on the outlet of the exhaust gas diversion structure 5, in order to make the tangential combustion system safer during operation. An exhaust gas air regulating valve is provided on the exhaust gas diversion structure 5, in order to adjust the thick-thin separation ratio and the air / exhaust gas air ratio, and to change the shape of the burner flame and the height of the flame center.

[0033] The thick-thin separation device 3 is a pipeline elbow separation device, a coal powder cyclone separation device, a swirl blade separation device or a shutter cone axial separation device, but is not limited to the above.

[0034] The utility model proposes a tangential combustion system for burning inferior coal, and the working process is as follows:

[0035] When the unit is running at high load or medium load, the pulverized coal concentration meets the requirements for stable combustion, the furnace heat load level is high, and the combustion condition is stable. At this time, the shut-off valve 6 of the exhaust gas from burner A to burners D / E / F is closed, and the inferior pulverized coal does not pass through the thick-thin separation device 3, and burns normally through burner A, that is, all pulverized coal airflow at the outlet of burner A does not undergo thick-thin separation and normally passes through burner A to enter the furnace for combustion. Among them, D / E / F burners represent burners D, E, and F.

[0036] When the unit is under low load, open the shut-off valve 6 from the exhaust gas of burner A to burners D / E / F. After the inferior pulverized coal is separated by the thick-thin separation device 3, the exhaust gas enters the furnace through burners D / E / F, and the dense-phase pulverized coal enters burner A for stable combustion. 1) When burners A and B are running at low load, the thick-thin separation method is adopted. You can choose to open one or two of the shut-off valves from burner A to burner D, burner A to burner E, and burner A to burner F, and the exhaust gas, air and pulverized coal enter the furnace through one or two layers of burners D / E / F. 2) When the A burner, B burner and C burner are running at low load, a thick-thin separation method is adopted. You can choose to open one or two of the shut-off valves from the exhaust gas of A burner to the D burner, the shut-off valve from the exhaust gas of A burner to the E burner, and the shut-off valve from the exhaust gas of A burner to the F burner, and the exhaust gas air and powder enter the furnace through one or two layers of the D / E / F burners. 3) When the A burner, B burner and D burner are running at low load, a thick-thin separation method is adopted. You can choose to open one or two of the shut-off valves from the exhaust gas of A burner to the D burner, the shut-off valve from the exhaust gas of A burner to the E burner, and the shut-off valve from the exhaust gas of A burner to the F burner, and the exhaust gas air and powder enter the furnace through one or two layers of the E / F burners.

[0037] When the unit is operating under low load conditions, taking the case where the A / B / C burners are in operation and the D / E / F burners are shut down as an example, according to the wind speed of the powder hose, the shut-off valve from the exhaust gas of the A burner to the D burner, the shut-off valve from the exhaust gas of the A burner to the E burner, and the shut-off valve from the exhaust gas of the A burner to the F burner, which are connected to the exhaust gas branch pipe corresponding to the A burner and leading to the D / E / F burners, can be selectively opened. The low-quality coal is passed through the A burner pulverizing system to generate an air-powder airflow, which is separated by the A burner concentration separation device to produce two airflows: the dilute phase part (i.e., exhaust gas) contains about 10% of the total coal powder and about 50% of the total air volume. The coal powder concentration is low and it is not easy to ignite. It enters the furnace through one or two layers of the upper combustion zone D / E / F burners above the center of the flame, and does not interfere with the stability of the overall combustion conditions in the furnace; the dense phase part contains about 90% of the total coal powder and about 50% of the total air volume. The coal powder concentration is high and the ignition heat is low, which is easy to ignite. It enters the furnace through the lower combustion zone A burner. Compared with the working condition without concentration separation, the ignition stability of the bottom burner is significantly improved, avoiding the negative impact of the high primary air rate on the combustion stability under low-load operation conditions. Among them, A / B / C burners represent A burners, B burners, and C burners.

[0038] The unit adopts a dense-lean separation layout and operation mode under low-load conditions of burning inferior coal, in which the A burner outlet powder pipe is equipped with an exhaust air main pipe leading to the D / E / F burners that are stopped at a high position, and an exhaust air branch pipe connected to the exhaust air main pipe and can lead to the D / E / F burners respectively, and the exhaust air branch pipe is equipped with a shut-off valve from the exhaust gas of the A burner to the D burner, a shut-off valve from the exhaust gas of the A burner to the E burner, and a shut-off valve from the exhaust gas of the A burner to the F burner, which can ensure that the exhaust air powder after dense-lean separation can selectively enter the furnace through the stopped upper burner, in which the concentration of the dense phase coal powder airflow and the position where the exhaust gas enters the furnace can be adjusted according to the operation needs. In high and medium load conditions where dense-lean separation is not required, the exhaust gas pipeline and the original coal mill outlet pipeline can be effectively isolated to ensure the safe operation of the system.

[0039] Therefore, the utility model discloses a tangential combustion system for burning inferior coal. When the combustion system burns inferior coal under high and medium load conditions, it does not need to perform dense-lean separation, and the coal powder is burned through the same-layer burner; when the combustion system burns inferior coal under low load conditions, the dense-lean separation technology is adopted to guide the exhaust gas to the D / E / F burner in the upper combustion zone to enter the furnace for combustion, and the dense phase coal powder enters the same-layer burner for stable combustion. By adjusting the operation state of the dense-lean separation device and the exhaust gas pipeline, the safe and stable operation of the boiler burning inferior coal under full load conditions is achieved, so as to achieve the stable combustion effect of inferior coal under low load.

[0040] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may be subject to various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A tangential combustion system for burning low-quality coal, characterized in that: It includes burners A, B, C, D, E and F installed on the furnace from bottom to top; A powder return pipe (2) is provided on each burner, a thick-thin separation device (3) is provided on the powder return pipe (2) of the A burner or the B burner, a dense-thin separation device (3) is provided with a dense-phase pulverized coal pipe (4) connected to the A burner or the B burner, and the other end of the dense-phase pulverized coal pipe (4) is connected to an exhaust gas diversion structure (5) leading to the D burner, the E burner and the F burner.

2. The tangential combustion system for burning low-quality coal according to claim 1, characterized in that: The exhaust gas diversion structure (5) is an exhaust gas main pipe.

3. The tangential circle combustion system for burning low-quality coal according to claim 2, characterized in that: The exhaust air main pipe is respectively connected with burner exhaust air branch pipes (7) leading to the D burner, the E burner and the F burner.

4. The tangential circle combustion system for burning low-quality coal according to claim 3 is characterized in that: A shut-off valve (6) is provided on the burner exhaust gas branch pipe (7).

5. The tangential circle combustion system for burning low-quality coal according to claim 1, characterized in that: The thick-thin separation device (3) is a pipeline elbow separation device, a coal powder cyclone separation device, a swirl blade separation device or a shutter cone axial separation device.

6. The tangential circle combustion system for burning low-quality coal according to claim 1, characterized in that: The powder return pipe (2) is provided with a first safety valve.

7. The tangential circle combustion system for burning low-quality coal according to claim 1, characterized in that: A second safety valve is provided at the outlet of the exhaust gas diversion structure (5).

8. The tangential circle combustion system for burning low-quality coal according to claim 1, characterized in that: An exhaust gas air regulating valve is arranged on the exhaust gas diversion structure (5).

9. A boiler, characterized in that: The invention comprises a plurality of coal mills, and the outlet of at least one coal mill is connected to the tangential circle combustion system for burning low-quality coal as claimed in any one of claims 1 to 8.

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