A boiler system

Abstract

The present invention relates to a boiler system. The boiler system includes a boiler and a coal pulverizing unit. The boiler has at least one burner. The coal pulverizing unit includes at least one coal mill. At least one powder delivery pipeline leading to the burner is connected to the outlet of each separator of each coal mill. An auxiliary powder pipeline is also connected to the outlet of each separator of the coal mill. The auxiliary powder pipeline is connected to a powder storage bin. A control valve for controlling the on / off of the auxiliary powder pipeline is provided on the pipeline of the auxiliary powder pipeline. The powder storage bin is communicated with each powder delivery pipeline, and a control device for controlling the on / off of the connection between the powder storage bin and the powder delivery pipeline is provided on the pipeline connecting the powder storage bin and each powder delivery pipeline. When the coal mill is operating normally, a certain amount of pulverized coal is stored in the powder storage bin; when the coal mill trips or coal supply is interrupted, the control device controls the connection between the powder storage bin and the powder delivery pipeline to enable the powder storage bin to start supplying powder. At the same time, the control valve on the powder delivery pipeline remains open, and the powder delivery pipeline acts as a wind duct to blow the pulverized coal to the burner to maintain the fuel supply of the burner, thereby preventing the boiler from extinguishing.

Description

Technical Field

[0001] The present invention relates to a boiler system. Background Art

[0002] Thermal power generation is the main force in the development of electric power in modern society, and the main fuel used is coal. Large thermal power plants usually burn pulverized coal to improve the coal combustion efficiency. Therefore, the coal in the coal bunker needs to be first sent into a coal mill to be ground into powder, and then sent to the furnace of the boiler for combustion. As Figure 1 shown, the boiler system includes a boiler 7 and a coal pulverizing unit. The coal pulverizing unit includes at least one coal mill 2. The boiler 7 has a plurality of burners 14, and each coal mill supplies pulverized coal to a plurality of burners. Most of the coal mills currently used in thermal power plants are double-inlet and double-outlet coal mills or vertical coal mills. The vertical coal mill has a separator. As Figure 2 shown, the outlet of the separator 6 is connected with a plurality of pulverized coal conveying pipelines 4, and each pulverized coal conveying pipeline leads to a different burner. A control valve 5 is provided on each pulverized coal conveying pipeline 4. The double-inlet and double-outlet coal mill has two separators. As Figure 3 shown, the outlet of each separator 6 is connected with a plurality of pulverized coal conveying pipelines 4. Each pulverized coal conveying pipeline from the outlet of the same separator leads to a different burner. A control valve 5 is provided on each pulverized coal conveying pipeline 4. Each coal mill supplies pulverized coal to a plurality of burners through a plurality of pulverized coal conveying pipelines. Once the coal mill trips or stops coal supply, the burners corresponding to this coal mill may have problems of insufficient fuel supply, and even may cause the furnace to extinguish, resulting in huge losses. Summary of the Invention

[0003] The purpose of the present invention is to provide a boiler system to solve the problem that when the coal mill trips or stops coal supply, it causes insufficient fuel supply to the burner and then leads to boiler extinguishing.

[0004] To achieve the above object, the boiler system of the present invention includes a boiler and a coal pulverizing unit. The boiler has at least one burner, and the coal pulverizing unit includes at least one coal mill. Each separator outlet of each coal mill is connected to at least one coal powder delivery pipeline leading to the burner. Each separator outlet of the coal mill is also connected to an auxiliary powder pipeline, and the auxiliary powder pipeline is connected to a coal powder storage bin. A control valve is provided on the pipeline of the auxiliary powder pipeline to control the connection of the auxiliary powder pipeline when the amount of coal powder in the coal powder storage bin is lower than the rated storage amount and to control the disconnection of the auxiliary powder pipeline when the amount of coal powder in the coal powder storage bin reaches the rated storage amount. The coal powder storage bin is connected to each coal powder delivery pipeline, and a control device is provided on the pipeline connecting the coal powder storage bin and each coal powder delivery pipeline to control the disconnection of the coal powder storage bin and the coal powder delivery pipeline during normal coal powder delivery in the coal powder delivery pipeline and to control the connection of the coal powder storage bin and the coal powder delivery pipeline when the coal powder delivery pipeline cannot deliver coal powder normally. When the coal mill is operating normally, the coal powder delivery pipeline supplies coal powder to each burner normally, and at the same time, a certain amount of coal powder is stored in the coal powder storage bin; when the coal mill trips or runs out of coal, the control device controls the connection of the coal powder storage bin and the coal powder delivery pipeline to start the coal powder supply from the coal powder storage bin. At the same time, the control valve on the coal powder delivery pipeline remains open, and the coal powder delivery pipeline acts as a wind duct to blow the coal powder to the burner to maintain the fuel supply of the burner, thereby avoiding boiler flameout.

[0005] Further, the control device is a control device capable of controlling the coal powder flow rate. The coal powder flow rate can be adjusted according to actual needs to maintain the normal coal powder supply of the corresponding burner, and at the same time, improve the utilization rate of coal powder.

[0006] Preferably, a powder feeder is used as the control device. The powder feeder is more convenient and reliable for controlling the coal powder flow rate.

[0007] Based on any of the above solutions, a pulverized coal-air mixer is provided at the position where the pipeline connecting the coal powder storage bin and the coal powder delivery pipeline is connected to the coal powder delivery pipeline. When the coal mill trips or runs out of coal, the pulverized coal-air mixer makes the primary air blown into by the coal powder delivery pipeline and the coal powder falling from the coal powder storage bin mix more evenly before entering the burner, so that the coal powder burns more fully in the burner and the utilization rate of coal powder is improved.

[0008] A new separator for separating air and coal powder is connected between the auxiliary powder pipeline and the coal powder storage bin. The new separator separates the coal powder and the primary air sent out by the auxiliary powder pipeline. A large amount of coal powder falls into the coal powder storage bin, and a small amount of fine coal powder is carried by the primary air and sent to other places.

[0009] Further, a lean-phase air pipeline leading to the burnout air layer of the boiler is connected to the air outlet of the new separator, and a valve for controlling the on-off of the lean-phase air pipeline is provided on the lean-phase air pipeline. The small amount of fine coal powder carried by the primary air is sent into the boiler for combustion through the lean-phase air pipeline, improving the utilization rate of coal powder.

[0010] The new separator is located above the coal powder storage bin, and due to the gravity of the coal powder, it automatically falls into the coal powder storage bin. Description of the Drawings

[0011] Figure 1 It is a working flow chart of multiple vertical coal mills used in an existing boiler system;

[0012] Figure 2 It is a working flow chart of a single vertical coal mill;

[0013] Figure 3 It is a working flow chart of a double-in and double-out coal mill;

[0014] Figure 4 It is a schematic diagram of an auxiliary powder pipe connected to a coal mill;

[0015] In the figure: 1 - raw coal hopper; 2 - coal mill; 3 - slag discharge box; 4 - powder delivery pipeline; 5 - control valve; 6 - separator; 7 - boiler; 8 - auxiliary powder pipe; 9 - powder storage bin; 10 - new separator; 11 - air-powder mixer; 12 - coal feeder; 13 - dilute-phase air pipeline; 14 - burner; 15 - valve. Specific embodiments

[0016] The following further describes the embodiments of the present invention in conjunction with the accompanying drawings.

[0017] Specific embodiments of the boiler system of the present invention include a boiler and a coal pulverizing unit. The boiler has at least one burner, and the coal pulverizing unit includes at least one coal mill. As Figure 4 shown, at least one powder delivery pipeline 4 leading to the burner is connected to the outlet of the separator 6 of each coal mill 2. An auxiliary powder pipe 8 is also connected to the outlet of the separator of the coal mill. The auxiliary powder pipe is connected to a powder storage bin 9. The powder storage bin 9 is provided with a rated storage capacity. A control valve 5 is provided on the pipeline of the auxiliary powder pipe 8 to control the connection of the auxiliary powder pipe 8 when the amount of pulverized coal in the powder storage bin 9 is lower than the rated storage capacity and to control the disconnection of the auxiliary powder pipe 8 when the amount of pulverized coal in the powder storage bin 9 reaches the rated storage capacity. The powder storage bin 9 is connected to each powder delivery pipeline 4, and a coal feeder 12 is provided on the pipeline connecting the powder storage bin and each powder delivery pipeline. When the powder delivery pipeline is delivering powder normally, the coal feeder controls the disconnection of the powder storage bin and the powder delivery pipeline. When the powder delivery pipeline cannot deliver powder normally, the coal feeder controls the connection of the powder storage bin and the powder delivery pipeline. The coal feeder can adjust the pulverized coal flow rate according to actual needs to maintain the normal pulverized coal supply to the corresponding burner. At the same time, the utilization rate of pulverized coal is improved. A air-powder mixer 11 is provided at the position where the pipeline connecting the powder storage bin and the powder delivery pipeline is connected to the powder delivery pipeline. When the coal mill trips or the coal supply is interrupted, the air-powder mixer makes the primary air blown in from the powder delivery pipeline and the pulverized coal falling from the powder storage bin mix more evenly before entering the burner, so that the pulverized coal burns more fully in the burner and the utilization rate of pulverized coal is improved.

[0018] An additional separator 10 is connected between the auxiliary pulverized coal pipe 8 and the pulverized coal storage bin 9. The additional separator separates the pulverized coal and primary air sent out by the auxiliary pulverized coal pipe. A lean-phase air pipeline 13 leading to the burnout air layer of the boiler is connected to the air outlet of the additional separator, and a valve 15 for controlling the on / off of the pipeline is provided on the lean-phase air pipeline. Most of the pulverized coal sent out by the auxiliary pulverized coal pipe 8 falls into the pulverized coal storage bin 9, and a small amount of fine pulverized coal is carried by the primary air and sent into the boiler 7 for combustion through the lean-phase air pipeline, thereby improving the utilization rate of pulverized coal. The additional separator 10 is located above the pulverized coal storage bin 9, and due to the gravity of the pulverized coal, it automatically falls into the pulverized coal storage bin.

[0019] The rated storage capacity of the pulverized coal storage bin is set according to actual needs, and it only needs to meet the output of one coal mill for a certain period of time. During this period, the coal mill failure is handled or other coal mills are started to avoid boiler flameout caused by the tripping or coal interruption of this coal mill.

[0020] The boiler system also includes a control unit, a monitoring unit for monitoring the working status of each coal mill, and a storage detector for detecting the pulverized coal storage capacity in the pulverized coal storage bin. The monitoring unit and the storage detector are both connected to the control unit for control. The control valves on each pulverized coal delivery pipeline, the control valves on the auxiliary pulverized coal pipeline, and the coal feeder are also connected to the control unit for control.

[0021] When the detection unit detects that a certain coal mill stops supplying pulverized coal, it sends a signal to the control unit. The control unit controls the opening of the coal feeder corresponding to the corresponding coal mill according to the received signal, so that the corresponding pulverized coal storage bin serves as a new pulverized coal source to continue supplying pulverized coal to the burner, thereby making the pulverized coal supply uninterrupted and maintaining the combustion of the burner. During the period when the pulverized coal storage bin supplies coal, the failure of this coal mill is handled. After the failure is eliminated, the coal mill continues to supply pulverized coal to the burner, and the detection unit sends a signal to the control unit, and the control unit controls the corresponding coal feeder to close according to the received signal. Of course, if this coal mill fails, other coal mills can also be started. Generally, large boilers in thermal power plants are equipped with multiple coal mills, and the number of operating coal mills is related to the load of the boiler. At low loads, generally 2 to 3 coal mills are operating, and there are standby coal mills. If the coal mills in operation experience coal interruption or tripping and other failures, the standby coal mills can be started to supply fuel to maintain the boiler load. Starting a standby coal mill is a relatively complex process and requires a certain startup time. During the period before the standby coal mill is started, the pulverized coal storage bin can serve as a new pulverized coal source to continue supplying pulverized coal to the burner, avoiding boiler flameout caused by the standby coal mill not being started in time.

[0022] When the storage detector detects that the pulverized coal storage in the pulverized coal bin is lower than the rated storage, it controls the control valve on the auxiliary powder pipe to open, separates a part of the pulverized coal milled by the coal mill, and stores it in the pulverized coal bin through the auxiliary powder pipe; when the storage detector detects that the pulverized coal storage in the pulverized coal bin reaches the rated amount, it controls the control valve on the auxiliary powder pipe to close, and the pulverized coal bin stops feeding powder.

[0023] When the coal mill is operating normally, the control valves on each powder feeding pipeline are in the open state, and the powder feeding pipeline normally supplies powder to each burner. At the same time, the control valve on the auxiliary powder pipe is opened to store a certain amount of pulverized coal in the pulverized coal bin. After the pulverized coal storage reaches the rated storage, the control valve is closed; when the coal mill trips or runs out of coal, the feeder is started to supply powder. At the same time, the control valves on each powder feeding pipeline still remain in the open state, and the powder feeding pipeline acts as an air duct to blow the pulverized coal falling from the pulverized coal bin to the burner, maintaining the fuel supply of the burner, so as to avoid boiler flameout.

[0024] During deep peak shaving, the boiler system can also be used to increase the pulverized coal concentration of the corresponding operating burners, reduce the ignition heat, and improve the combustion stability.

[0025] In addition, it should be supplemented that whether the coal mill used in the boiler system is a vertical coal mill as Figure 2 shown or a double-in and double-out coal mill as Figure 3 shown, it can achieve the purpose of continuously supplying pulverized coal to the burner and avoiding boiler flameout when the coal mill trips or runs out of coal.

[0026] In the above embodiments, the coal powder flow is controlled by the feeder. In other embodiments, a regulating valve can also be used. Of course, a shut-off valve can also be used, but the shut-off valve can only control the connection or disconnection between the pulverized coal bin and the powder feeding pipeline and cannot control the coal powder flow.

[0027] In the above embodiments, the new separator is located above the pulverized coal bin, considering that it is more convenient to make the pulverized coal fall into the pulverized coal bin by using the self-gravity of the pulverized coal. Of course, it is not limited to this. The new separator can also be set at other positions, such as below the pulverized coal bin, and the pulverized coal is pumped into the pulverized coal bin by a pump.

Claims

1. A boiler system comprising a boiler and a pulverizing unit, wherein the boiler has at least one burner, and the pulverizing unit comprises at least one coal mill, wherein each separator outlet of each coal mill is connected to at least one pulverizing pipeline leading to the burner, wherein: Each separator outlet of the coal mill is also connected to an auxiliary powder pipe, and the auxiliary powder pipe is connected to a powder storage bin. The auxiliary powder pipe pipeline is provided with a control valve which controls the auxiliary powder pipe to be connected when the amount of coal powder in the powder storage bin is lower than the rated storage amount, and controls the auxiliary powder pipe to be disconnected when the amount of coal powder in the powder storage bin reaches the rated storage amount. The powder storage bin is connected to each powder delivery pipeline, and the pipeline connecting the powder storage bin and each powder delivery pipeline is provided with a control device which controls the powder storage bin to be disconnected from the powder delivery pipeline when the powder delivery pipeline is delivering powder normally, and controls the powder storage bin to be connected to the powder delivery pipeline when the powder delivery pipeline cannot deliver powder normally.

2. The boiler system according to claim 1, wherein: The control device is a control device capable of controlling the flow rate of pulverized coal.

3. The boiler system according to claim 2, characterized in that: The control device is a powder feeder.

4. The boiler system according to any one of claims 1 to 3, characterized in that: An air-powder mixer is provided at a position where the pipeline connecting the powder storage bin and the powder delivery pipeline is connected to the powder delivery pipeline.

5. The boiler system according to any one of claims 1 to 3, characterized in that: A newly added separator for separating air and coal powder is connected between the auxiliary powder pipe and the powder storage bin.

6. The boiler system according to claim 5, characterized in that: The air outlet of the newly added separator is connected to a dilute phase air pipeline leading to the boiler burnout air layer, and a valve for controlling the on-off of the dilute phase air pipeline is provided on the dilute phase air pipeline.

7. The boiler system according to claim 5, characterized in that: The newly added separator is located above the powder storage bin.

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