Material returning device of circulating fluidized bed boiler

Abstract

The utility model discloses a circulating fluidized bed boiler material returning device which comprises a material returning device vertical pipe, a material returning ascending section and a material returning pipe, the material returning ascending section is communicated with a hearth through the material returning pipe, and a material storage ascending section and a material storage branch bin are arranged beside the material returning ascending section in parallel. The storage sub-bins are communicated with the hearth through storage sub-bin return pipes provided with ash control valves; and the bottoms of the material return ascending section, the material storage ascending section and the material storage branch bins are respectively and correspondingly provided with air chambers which can be independently regulated and controlled. According to the device, the material storage function and the material return function are integrated in the material return device, an ash storage device does not need to be independently arranged, a mature material return device structure is adopted, materials can be flexibly stored and returned according to actual conditions in the operation process of the CFB boiler, and therefore the purposes of adjusting the ash concentration in the boiler, changing the heat capacity of a main circulation loop and improving the variable load rate of the boiler are achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a circulating fluidized bed boiler's back material device especially a back material device that can assist to complete circulating fluidized bed boiler fast peak shaving. BACKGROUND

[0002] The deep peak shaving technology of the commonly used thermal power generating unit at present mainly realizes the dynamic balance of the power grid through the deep variable load of the thermal power generating unit 20%~50% rated load, thermal decoupling or unit start-stop mode. However, the cost of the thermal power generating unit using the start-stop mode for peak shaving is relatively high, and frequent start-stop will also affect the service life of the unit, so the deep variable load technology becomes the main way for the thermal power generating unit to participate in flexible peak shaving. At present, the coal-fired CFB unit can usually only realize 30% peak shaving depth, and the advanced level or through certain modification technology can reach about 20%. The new generation of coal power construction action implementation scheme proposes higher requirements for the peak shaving depth and climbing rate of the coal power unit, but the CFB boiler has certain disadvantages in variable load due to its unique gas-solid flow and combustion mode, large thermal inertia and more heat storage.

[0003] The main factors affecting the heat transfer coefficient of the furnace heating surface of the CFB boiler include the circulating particle suspension density, ash particle size, fluidization speed, etc. The unique combustion mode of the CFB boiler determines that there are a large number of solid particles in the entire main circulating loop, and the heat capacity of the particles in the furnace is higher than that of the gas, so the particle convection heat transfer is the main heat transfer mechanism. The size of the particle convection heat transfer coefficient mainly depends on the aggregation concentration of the solid particles in the heating surface arrangement area and the particle renewal rate. The increase of the suspension density increases the particle concentration near the wall, providing more particles for heat exchange between the wall and the particles. A large number of circulating solid particles carry most of the heat of the boiler and circulate in the furnace, which also brings larger flow inertia to the entire system. The larger heat storage amount leads to the increase of the thermal inertia of the furnace heat transfer process, causing the slow load change rate of the CFB boiler, which is difficult to achieve fast response on the working medium side. The size of the flow inertia can be reflected as the speed of the change of the effective circulating ash amount in the furnace. Therefore, by changing the circulating ash amount in the furnace, the heat transfer coefficient of the CFB boiler can be effectively adjusted, the response speed on the working medium side can be accelerated, and the variable load rate of the CFB boiler can be improved.

[0004] CFB boiler return device is one of the key components of the boiler, the solid material separated by the cyclone separator establishes the material level height in the standpipe to ensure the loop seal, prevent the backflow of flue gas in the furnace, and continuously and stably return the material to the furnace, so as to realize the self-balancing of the returned material, maintain the necessary ash amount of the main circulating loop, and the power source of the returned material is derived from the material level difference between the ascending section and the descending section of the return device. The circulating ash captured by the conventional circulating fluidized bed boiler firstly passes through the return device standpipe, then enters the return device ascending section, and then is directly sent back to the furnace for the next material circulation without the ability and means to adjust the particle concentration in the furnace.

[0005] A circulating fluidized bed boiler wide load rapid peak regulation system is disclosed in CN219588933U, which controls the amount of solid particles entering the furnace through the ash storage mechanism to complete the rapid load regulation of the unit; the ash storage mechanism is used to heat the air entering the air preheater through the air supply mechanism, which on the one hand improves the temperature of the cold end of the air preheater, and on the other hand improves the stability and economy of the unit operation; by adding a first branch pipe and a second branch pipe to the secondary air fan, the output of the secondary air fan is increased to avoid the problem of stall of the secondary air fan running at low flow. However, the separate arrangement of the ash storage device is difficult to balance in terms of layout space, safety of the ash storage device, and control of the amount of ash, and the system configuration is complex.

[0006] A rapid load change circulating fluidized bed boiler is disclosed in CN208920042U, which realizes rapid change of the material concentration in the furnace during the peak regulation process through reasonable arrangement of the material leg, the return device, the return pipe and the rapid peak regulation bin, so as to adapt to the requirement of the power grid for the rapid response characteristics of the steam parameters. The rapid peak regulation bin is connected with the return pipe through a pipeline provided with an ash control valve, and a separate air distribution device is arranged at the bottom of the rapid peak regulation bin. In this structure, the rapid peak regulation bin is one or more than one which is separately arranged relative to the return device. To ensure that the ash is discharged from the return device to the ash storage bin, the ash storage bin must be lower than the return device, and the angle of the intermediate pipe must be ensured. Also, the ash storage bin must be higher than the return port of the furnace, which requires a greater height space in the layout, otherwise it is difficult to ensure the angle of the return pipe. Utility model content

[0007] The technical problem to be solved by the utility model is to provide a circulating fluidized bed boiler return device, which integrates the storage function and the return function of the return device, does not need to separately arrange an ash storage device, adopts a mature return device structure, can flexibly store and return material according to the actual situation during the operation of the CFB boiler, and thus achieves the purposes of adjusting the ash concentration in the furnace, changing the heat capacity of the main circulating loop and improving the variable load rate of the boiler.

[0008] The technical solution adopted by this utility model to solve its technical problem is: a circulating fluidized bed boiler feed return device, including a feed return riser, a feed return riser section, and a feed return pipe. The feed return riser section is connected to the furnace through the feed return pipe. A storage riser section and a storage compartment are arranged in parallel on the side of the feed return riser section. The storage compartment is connected to the furnace through a storage compartment return pipe equipped with an ash control valve. The bottom of the feed return riser section, the storage riser section, and the storage compartment are respectively provided with independently adjustable air chambers.

[0009] To reduce the impact of cooling during the ash storage process before it enters the furnace on combustion, the fluidizing air entering the ash storage compartment is preheated. Existing air preheating structures can be used to achieve this preheating.

[0010] To save space, the return feeder riser extends into the material storage rising section.

[0011] The beneficial effects of this utility model are: integrating the material storage device and the material return device, arranging the material storage rising section in parallel with the material return rising section, and setting up a material storage compartment next to the material storage rising section, eliminating the need for a separate ash storage device, and achieving the same purpose of adjusting the ash depth in the furnace, changing the heat capacity of the main circulation loop, and improving the boiler's variable load rate. The structure is simpler and easier to arrange. Attached Figure Description

[0012] Figure 1 This is a schematic diagram illustrating the application of this invention on a double-leg return feeder.

[0013] Figure 2 yes Figure 1 AA sectional view.

[0014] Figure 3 yes Figure 2 A schematic diagram of the BB cross-sectional view rotated 90 degrees counterclockwise.

[0015] Figure 4 This is a schematic diagram illustrating the application of this utility model on a single-leg feeder.

[0016] Figure 5 yes Figure 4 AA sectional view.

[0017] Figure 6 yes Figure 3 A schematic diagram of the BB cross-sectional view rotated 90 degrees counterclockwise.

[0018] The diagram is labeled as follows: 1-Return feeder riser, 2-Return feeder ascending section, 3-Storage feeder ascending section, 4-Storage feeder compartment, 5-Return feeder return pipe, 6-Storage feeder return pipe, 7-Ash control valve, 8-Partition wall, 9-Storage feeder compartment bottom plate, 10-Storage feeder ascending section bottom plate. The solid arrows in each diagram indicate the direction of material flow. Detailed Implementation

[0019] The utility model is further illustrated below in combination with the drawings and embodiments.

[0020] Embodiment 1

[0021] As shown in Figure 1 , Figure 2 , Figure 3 The circulating fluidized bed boiler return device of the utility model is applied to a double-leg return device, the bottom of the return device vertical pipe 1 is communicated with the bottom of the return device ascending section 2, the return device ascending section 2 is communicated with the furnace through two return device return pipes 5 arranged side by side, one storage ascending section 3 is arranged in parallel on the side of the return device ascending section 2, one storage compartment 4 is arranged on the two sides of the storage ascending section 3 respectively, the return device vertical pipe 1 is inserted into the storage ascending section 3, the lower parts of the two are cut off but the upper parts are communicated, each single storage compartment 4 is communicated with the furnace through a storage compartment return pipe 6 provided with an ash control valve 7; the bottoms of the return device ascending section 2, the storage ascending section 3 and the single storage compartment 4 are respectively provided with independently controllable air chambers. The structure of each air chamber can adopt a structure similar to the air chamber used in the existing return device return device ascending section 2, and therefore is omitted. Figure 2 In the figure, one side of the dotted line is the return device, and the other side of the dotted line is the furnace.

[0022] Specifically, the bottom of the storage ascending section 3 is communicated with the return device vertical pipe 1, but the storage ascending section 3 and the return device ascending section 2 are mutually separated, and a partition wall 8 is arranged between the storage ascending section 3 and the storage compartment 4 at the lower part, so that the material in the storage ascending section 3 can be temporarily accumulated in the storage compartment 4 after being pushed to the storage compartment 4. When being arranged, in order to facilitate adjustment, the top positions of the storage ascending section 3 and the storage compartment 4 are equivalent to the top position of the return device ascending section 2, but the bottom plate position of the storage compartment 4 can be lower than the bottom plate position of the storage ascending section 3, so as to increase the capacity of the storage compartment 4 and expand the adjustment range of the temporary storage material volume.

[0023] When the boiler is in steady state operation, the storage ascending section 3 is operated with a small fluidization air volume, at this time, the material in the storage ascending section 3 plays a sealing role, separates the storage compartment 4 from the return device vertical pipe 1, the circulating ash captured by the cyclone separator normally enters the furnace through the return device vertical pipe 1, the return device ascending section 2 and the return device return pipe 5, and the ash control valve 7 is in a closed state. The storage compartment 4 does not play a role of temporarily storing material at this time, and the circulating fluidized bed boiler return device of the utility model is equivalent to a conventional return device.

[0024] When the boiler has a need for rapid load reduction, the boiler operating load gradually decreases, the fluidization air volume of the storage rising section 3 is increased, and a part of the circulating material captured by the cyclone separator is sent into the storage compartment 4 for storage. The storage compartment 4 is operated with a smaller fluidization air volume to ensure the basic fluidization state. In order to avoid the temperature of the solid particles in the storage compartment 4 from decreasing too much to affect the ignition in the furnace, the fluidization air of the storage compartment 4 is preferably preheated before entering the storage compartment 4. The ash control valve 7 is in a closed state, and the other part of the circulating material normally passes through the return pipe 1, the return rising section 2 and the return compartment return pipe 5 into the furnace. In this way, the ash concentration and the heat transfer coefficient in the furnace can be effectively reduced, and the purpose of rapidly reducing the boiler load can be achieved.

[0025] When the boiler has a need for rapid load reduction, the boiler operating load gradually decreases, the fluidization air volume of the storage rising section 3 is increased, and a part of the circulating material captured by the cyclone separator is sent into the storage compartment 4 for storage. The storage compartment 4 is operated with a smaller fluidization air volume to ensure the basic fluidization state. In order to avoid the temperature of the solid particles in the storage compartment 4 from decreasing too much to affect the ignition in the furnace, the fluidization air of the storage compartment 4 is preferably preheated before entering the storage compartment 4. The ash control valve 7 is in a closed state, and the other part of the circulating material normally passes through the return pipe 1, the return rising section 2 and the return compartment return pipe 5 into the furnace. In this way, the ash concentration and the heat transfer coefficient in the furnace can be effectively reduced, and the purpose of rapidly reducing the boiler load can be achieved.

[0026] In summary, the circulating fluidized bed boiler return device of the present application can achieve the purpose of adjusting the boiler load, and the newly added storage rising section 3 and storage compartment 4 can be arranged around the conventional return pipe, which is convenient and does not require more height space.

[0027] Example 2:

[0028] As shown in Figure 4 , Figure 5 , Figure 6 The circulating fluidized bed boiler return device of the present application is applied to a single-leg return pipe, and the structure is similar to the aforementioned example 1. The way of adjusting and controlling the boiler load is also the same. The bottom of the return pipe 1 is connected with the bottom of the return rising section 2, the return rising section 2 is connected with the furnace through a return return pipe 5, a storage rising section 3 is arranged in parallel on the side of the return rising section 2, two storage compartments 4 are arranged on the two sides of the storage rising section 3 respectively, the return pipe 1 extends into the storage rising section 3, the lower parts of the two are separated but the upper parts are connected, each single storage compartment 4 is connected with the furnace through a storage compartment return pipe 6 provided with an ash control valve 7; the bottoms of the return rising section 2, the storage rising section 3 and the single storage compartment 4 are respectively provided with independently controllable air chambers. Figure 5 In the figure, one side of the dotted line is the return pipe, and the other side of the dotted line is the furnace.

Claims

1. A circulating fluidized bed boiler feed return device, comprising a feed return riser (1), a feed return ascending section (2), and a feed return pipe (5), wherein the feed return ascending section (2) is connected to the furnace via the feed return pipe (5), characterized in that: Parallelly arranged on the side of the return material ascending section (2) are a storage material ascending section (3) and a storage material sub-bin (4), the storage material sub-bin (4) is communicated with the furnace through a storage material sub-bin return material pipe (6) provided with an ash control valve (7); the bottoms of the return material ascending section (2), the storage material ascending section (3) and the storage material sub-bin (4) are respectively provided with independently controllable air chambers.

2. A circulating fluidized bed boiler backfeed device as claimed in claim 1, characterized in that The fluidized air entering the storage material sub-bin (4) is preheated.

3. A circulating fluidized bed boiler backfeed device according to claim 1 or 2, characterized in that: The return material riser (1) extends into the storage material ascending section (3).

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