Circulating fluidized bed boiler heat storage type fast start, variable load system and method

Abstract

The application relates to a circulating fluidized bed boiler heat storage type rapid starting and variable load system and method, which comprises two circulating fluidized bed boilers, the lower part of the furnace of each circulating fluidized bed boiler is connected with a material returning device through a material returning pipe; the material returning device of the first circulating fluidized bed boiler is connected with the material returning pipe of the second circulating fluidized bed boiler through a first material conveying pipeline, the material returning device of the second circulating fluidized bed boiler is connected with the material returning pipe of the first circulating fluidized bed boiler through a second material conveying pipeline; the middle part of the first material conveying pipeline and the second material conveying pipeline is communicated and connected with a heat storage tank; the first material conveying pipeline, the second material conveying pipeline and the heat storage tank are connected with a compressed air storage tank through a compressed air pipeline, and the compressed air storage tank is connected with an air compressor. The application utilizes the high-temperature bed material in the already operated circulating fluidized bed boiler to heat the circulating fluidized bed boiler which is about to be started, can rapidly increase the bed material temperature in the boiler to be started, makes the bed material reach the ignition condition, and further improves the starting speed of the boiler.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of boiler rapid start-up and variable load system, and particularly relates to a heat storage type rapid start-up and variable load system and method for a circulating fluidized bed boiler. BACKGROUND

[0002] The circulating fluidized bed boiler blows up the coal particles, biomass and other fuels and bed materials from the bottom of the furnace by fluidizing air, so that the particles are in a fluidized state and are combusted. The flue gas carrying part of the fine particles leaves the furnace and enters the gas-solid separator, the separator captures the particles in the fly ash, and returns to the furnace through the return feeder to form a cycle of solid particles. There is a large amount of inert solid particle bed material in the furnace, which is mainly composed of ash left over after coal combustion, and this part of the particles does not participate in the combustion reaction. Due to the strong heat storage capacity of high-temperature bed material, the residence time of fuel in the furnace is increased, and the combustion efficiency is high, so the circulating fluidized bed boiler has the characteristics of wide fuel application range; the circulating fluidized bed boiler can stably burn at a relatively low combustion temperature (800-900℃), and the generation of nitrogen oxides is lower than that of a pulverized coal boiler; by adding limestone in the furnace, sulfur dioxide can be removed during the combustion process, greatly reducing the desulfurization cost. Based on the above advantages, the circulating fluidized bed boiler is the best choice for large-scale clean use of high-sulfur and high-ash coal, gangue, washed medium coal, coal slime and biomass fuels. In recent years, the circulating fluidized bed boiler has been developing towards large-scale and high-parameter.

[0003] However, the circulating fluidized bed boiler has a large amount of bed material in the furnace, and the thermal inertia is large, which also has certain problems compared with other forms of boilers:

[0004] 1. Long start-up time and high energy consumption. Due to the existence of hundreds of tons of inert solid particle bed material in the boiler, during the start-up process of the boiler, the bed material in the furnace needs to be heated to a certain temperature first, so that the fuel in the furnace can burn stably, therefore the start-up time of the boiler is relatively long, and the energy consumption is high;

[0005] 2. Slow load regulation. During the operation of the boiler, due to the large amount of solid particles in the furnace, the furnace temperature is relatively stable, and during the load regulation process, the furnace temperature and the heat transfer coefficient change relatively slowly, resulting in relatively slow load change.

[0006] With the development of new energy technologies such as wind power and solar energy, higher requirements are put forward for the peak shaving flexibility of traditional coal-fired power plants, and it is urgent to improve the load regulation rate of the circulating fluidized bed unit. SUMMARY

[0007] The present application provides a heat storage type rapid start-up and variable load system and method for a circulating fluidized bed boiler to solve the technical problems of slow start-up and slow load regulation of the circulating fluidized bed boiler in the prior art.

[0008] The application comprises the following technical scheme: a circulating fluidized bed boiler heat storage type rapid starting and variable load system, comprising two circulating fluidized bed boilers, the lower part of the furnace of each circulating fluidized bed boiler is connected with a return feeder through a return pipe; the return feeder of the first circulating fluidized bed boiler is connected to the return pipe of the second circulating fluidized bed boiler through a first material conveying pipeline, and the return feeder of the second circulating fluidized bed boiler is connected to the return pipe of the first circulating fluidized bed boiler through a second material conveying pipeline; the middle part of the first material conveying pipeline and the second material conveying pipeline is communicated and connected with a heat storage tank; the first material conveying pipeline, the second material conveying pipeline and the heat storage tank are connected to a compressed air storage tank through a compressed air pipeline, and the compressed air storage tank is connected with an air compressor.

[0009] The material conveying pipeline, the heat storage system and the compressed air system are arranged between the return feeders of the two circulating fluidized bed boilers, so that the bed material particles in the furnace can be exchanged between the two boilers. The system can rapidly heat the solid particles in the other circulating fluidized bed boiler under the premise that one circulating fluidized bed boiler is in normal operation, so as to realize the functions of rapid starting and rapid load adjustment.

[0010] Further, the first material conveying pipeline and the second material conveying pipeline are communicated through a third material conveying pipeline, and the third material conveying pipeline is connected to the heat storage tank.

[0011] Further, two branches are arranged in the middle part of the third material conveying pipeline and connected to the heat storage tank, the connection point at the upper part of the heat storage tank is a particle inlet, and the connection point at the bottom of the heat storage tank is a particle outlet; a feeding plug-in door is arranged on the branch close to the particle inlet, and a discharging plug-in door is arranged on the branch close to the particle outlet.

[0012] Further, a first material plug-in door and a third material plug-in door are arranged at the end close to the return feeder and the end close to the return pipe of the first material conveying pipeline, respectively.

[0013] Further, a second material plug-in door and a fourth material plug-in door are arranged at the end close to the return pipe and the end close to the return feeder of the second material conveying pipeline, respectively.

[0014] Further, one end of the compressed air pipeline is provided with three compressed air branches; a first compressed air branch is connected to the first material conveying pipeline, a second compressed air branch is connected to the second material conveying pipeline, and a third compressed air branch is connected to the heat storage tank and the third material conveying pipeline.

[0015] Further, an air valve is arranged on each of the compressed air branches.

[0016] Further, the third compressed air branch pipe is provided with two branches after the air valve, one branch is connected to the bottom of the heat storage tank, and the other branch is connected to the end of the third material conveying pipe away from the heat storage tank; further branches can be provided according to the needs of material conveying and pipeline arrangement, and the different positions of the third material conveying pipe are connected.

[0017] Further, the connection point of the first compressed air branch pipe and the first material conveying pipe is close to the first circulating fluidized bed boiler; and the connection point of the second compressed air branch pipe and the second material conveying pipe is close to the second circulating fluidized bed boiler. In actual production and use, the first compressed air branch pipe can be further provided with multiple branches, and the connection point of the first compressed air branch pipe and the first material conveying pipe can be provided with multiple points according to the needs of material conveying and pipeline arrangement; the second compressed air branch pipe can also be further provided with multiple branches, and the connection point of the second compressed air branch pipe and the second material conveying pipe can be provided with multiple points according to the needs of material conveying and pipeline arrangement.

[0018] Further, the heat storage tank, the first material conveying pipe, the second material conveying pipe and the third material conveying pipe are all wrapped with heat preservation materials.

[0019] A heat storage type rapid starting and load changing method of a circulating fluidized bed boiler, which uses the rapid starting and load changing system, comprises the following steps: firstly, high-temperature solid particles in a return feeder of a normally operating first circulating fluidized bed boiler are transported under compressed air to enter a furnace of a second circulating fluidized bed boiler to be started, so that the furnace solid particle bed material is rapidly heated; at this time, the coal supply amount of the first circulating fluidized bed boiler is increased, the temperature in the furnace is kept unchanged, and the second circulating fluidized bed boiler is rapidly started; when the second circulating fluidized bed boiler needs to rapidly increase load, the operation process is the same as that of the rapid starting;

[0020] When any circulating fluidized bed boiler needs to rapidly decrease load, the circulating ash is made to enter the heat storage tank under compressed air, so that the boiler load decreasing speed is increased, and the heat carried by the solid particles is stored; after the high-temperature solid particles are stored in the heat storage tank, when the first circulating fluidized bed boiler needs to rapidly increase load, the high-temperature solid particles in the heat storage tank and the return feeder of the second circulating fluidized bed boiler are transported to the furnace of the first circulating fluidized bed boiler under compressed air, and vice versa.

[0021] The present application has the advantages and positive effects that:

[0022] 1、The present application uses the high temperature bed material in the running circulating fluidized bed boiler to heat the circulating fluidized bed boiler which is about to start, which can quickly increase the bed material temperature in the boiler to be started to reach the ignition condition, thereby improving the starting speed of the boiler. Assuming that the bed material flow is 500 kg / s, the bed material temperature can reach 600 DEG C in 10 minutes to meet the combustion condition, which can reduce the starting time of the original equipment by 80%.

[0023] 2、For the boiler providing high temperature bed material, the coal quantity is appropriately increased, and the cold bed material of the adjacent boiler is returned, so that the boiler output can be ensured without reduction; the bed material in the boiler to be started is equivalent to absorbing the heat of the coal of the adjacent boiler to be heated, compared with the traditional air duct burner burning oil or natural gas to increase the bed material temperature, and several ten thousand yuan of cost can be saved in one starting.

[0024] 3、The present application uses the heat storage tank to store high temperature bed material when the boiler is running, which can effectively reduce the radiation effect of the gas-solid two-phase flow convection in the boiler, so that the load of the boiler can be quickly reduced; the quick starting and quick load reduction of the boiler are beneficial to the regulation of the power grid, and in the background of the increasing wind power and solar power generation, the flexibility of the thermal power can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the overall structure schematic diagram of the present application.

[0026] In the figure, 1 is a first circulating fluidized bed boiler; 10 is a first material return device; 11 is a first material return pipe;

[0027] 2 is a second circulating fluidized bed boiler; 20 is a second material return device; 21 is a second material return pipe;

[0028] 3 is an air compressor; 4 is a compressed air storage tank; 41 is a first compressed air branch pipe; 411 is a first air valve; 42 is a second compressed air branch pipe; 421 is a second air valve; 43 is a third compressed air branch pipe; 431 is a third air valve;

[0029] 5 is a first material conveying pipeline; 51 is a first material conveying plug-in door; 52 is a third material conveying plug-in door;

[0030] 6 is a second material conveying pipeline; 61 is a second material conveying plug-in door; 62 is a fourth material conveying plug-in door;

[0031] 7 is a third material conveying pipeline; 71 is a feeding plug-in door; 72 is a discharging plug-in door; 8 is a heat storage tank. DETAILED DESCRIPTION

[0032] In order to further disclose the invention content, characteristics and effects of the present application, the following examples are specifically illustrated as follows in combination with the drawings.

[0033] Embodiment: refer to the attached Figure 1The application discloses a heat storage type fast starting and variable load system of a circulating fluidized bed boiler, which comprises two circulating fluidized bed boilers, a first circulating fluidized bed boiler 1, a first return pipe 11 connected to a first return feeder 10 at the lower part of the furnace of the first circulating fluidized bed boiler 1, a second circulating fluidized bed boiler 2, a second return pipe 21 connected to a second return feeder 20 at the lower part of the furnace of the second circulating fluidized bed boiler 2, the first return feeder 10 connected to the second return pipe 21 through a first feeding pipe 5, the second return feeder 20 connected to the first return pipe 11 through a second feeding pipe 6, the first feeding pipe 5 and the second feeding pipe 6 communicated at the middle part and connected to a heat storage tank 8, the first feeding pipe 5, the second feeding pipe 6 and the heat storage tank 8 all connected to a compressed air storage tank 4 through a compressed air pipe, and the compressed air storage tank 4 connected to an air compressor 3.

[0034] The first feeding pipe 5 and the second feeding pipe 6 are communicated through a third feeding pipe 7, the third feeding pipe 7 connected to the heat storage tank 8, two branches of the third feeding pipe 7 connected to the heat storage tank 8 at the middle part, a particle inlet at the upper part of the heat storage tank 8 and a particle outlet at the bottom of the heat storage tank 8, a feeding plug-in door 71 arranged on the branch close to the particle inlet and a discharging plug-in door 72 arranged on the branch close to the particle outlet, and the heat storage tank 8, the first feeding pipe 5, the second feeding pipe 6 and the third feeding pipe 7 all wrapped with heat insulation materials.

[0035] The first feeding pipe 5 is provided with a first feeding plug-in door 51 at one end close to the first return feeder 10, and the first feeding pipe 5 is provided with a third feeding plug-in door 52 at one end close to the second return pipe 21; the second feeding pipe 6 is provided with a second feeding plug-in door 61 at one end close to the first return pipe 11, and the second feeding pipe 6 is provided with a fourth feeding plug-in door 62 at one end close to the second return feeder 20.

[0036] One end of the compressed air pipe is provided with three compressed air branch pipes; a first compressed air branch pipe 41 connected to the first feeding pipe 5, the connection point of the first compressed air branch pipe 41 and the first feeding pipe 5 close to the first circulating fluidized bed boiler 1; a second compressed air branch pipe 42 connected to the second feeding pipe 6, the connection point of the second compressed air branch pipe 42 and the second feeding pipe 6 close to the second circulating fluidized bed boiler 2; and a third compressed air branch pipe 43 connected to the heat storage tank 8 and the third feeding pipe 7; the first compressed air branch pipe 41 is provided with a first air valve 411, the second compressed air branch pipe 42 is provided with a second air valve 421, and the third compressed air branch pipe 43 is provided with a third air valve 431.

[0037] The pipeline of the third compressed air branch pipe 43 behind the third air valve 431 is provided with two branches, one branch connected to the bottom of the heat storage tank 8 and the other branch connected to one end of the third feeding pipe 7 away from the heat storage tank 8.

[0038] The feeding pipe, heat storage system and compressed air system are arranged between the two circulating fluidized bed boiler return feeders, so that the bed material particles in the furnace can be exchanged. The system can make the solid particles in another circulating fluidized bed boiler rapidly heat up, realize the function of rapid start and rapid load adjustment under the premise that one circulating fluidized bed boiler is in normal operation.

[0039] Working principle:

[0040] When the system is not working, all the plug-in doors and valves are in the closed state, and the heat storage tank 8 does not store solid particles, so as to ensure that the air pressure in the compressed air storage tank 4 is greater than 0.6 Mpa.

[0041] When the first circulating fluidized bed boiler 1 is in normal operation, if the second circulating fluidized bed boiler 2 is started. First, open the first feeding plug-in door 51 and the third feeding plug-in door 52 on the first feeding pipe 5. Open the first air valve 411 on the first compressed air branch pipe 41. At this time, the solid particles in the first return feeder 10 of the first circulating fluidized bed boiler 1 enter the second return pipe 21 of the second circulating fluidized bed boiler 2, and then enter the furnace of the second circulating fluidized bed boiler 2 through the second return pipe 21. The solid particle bed in the furnace is rapidly heated up. At this time, the coal supply of the first circulating fluidized bed boiler 1 is appropriately increased to keep the temperature in the furnace unchanged.

[0042] When the first circulating fluidized bed boiler 1 is in normal operation, and the second circulating fluidized bed boiler 2 needs to rapidly increase the load, the operation process is the same as that of the auxiliary boiler rapid start.

[0043] When the first circulating fluidized bed boiler 1 needs to rapidly reduce the load, all the plug-in doors and valves are in the closed state, the first feeding plug-in door 51 on the first feeding pipe 5 and the feeding plug-in door 71 on the third feeding pipe 7 are opened. The circulating ash enters the heat storage tank 8 through compressed air to improve the speed of reducing the load of the boiler, and at the same time, the heat carried by the solid particles is stored.

[0044] After the heat storage tank 8 stores high-temperature solid particles, if the first circulating fluidized bed boiler 1 needs to rapidly increase the load, the discharge plug-in door 72 on the third feeding pipe 7 and the fourth feeding plug-in door 62 on the second feeding pipe 6 are opened. The high-temperature particles are transported to the first return pipe 11 of the first circulating fluidized bed boiler 1 through compressed air, and then enter the furnace of the first circulating fluidized bed boiler 1.

[0045] Although the preferred embodiments of the present application have been described, the present application is not limited to the above-mentioned specific embodiments, and the above-mentioned specific embodiments are merely illustrative, not restrictive, and many forms can be made by those skilled in the art under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims. These all belong to the protection scope of the present application.

Claims

1. A heat storage type fast start-up and load change system for a circulating fluidized bed boiler, comprising two circulating fluidized bed boilers, and a return feeder connected to a return pipe at the lower part of the furnace of each of the circulating fluidized bed boilers, characterized in that: The first circulating fluidized bed boiler's return feeder is connected to the second circulating fluidized bed boiler's return pipe through a first feeding pipe, and the second circulating fluidized bed boiler's return feeder is connected to the first circulating fluidized bed boiler's return pipe through a second feeding pipe; the first feeding pipe and the second feeding pipe are connected to a heat storage tank at the middle part; the first feeding pipe, the second feeding pipe and the heat storage tank are connected to a compressed air storage tank through a compressed air pipe, and the compressed air storage tank is connected to an air compressor; one end of the compressed air pipe is provided with three compressed air branch pipes; the first compressed air branch pipe is connected to the first feeding pipe, the second compressed air branch pipe is connected to the second feeding pipe, and the third compressed air branch pipe is connected to the heat storage tank and a third feeding pipe; the third compressed air branch pipe is provided with two branches at the pipeline behind the air valve, one branch is connected to the bottom of the heat storage tank, and the other branch is connected to one end of the third feeding pipe away from the heat storage tank; after high-temperature solid particles are stored in the heat storage tank, if the first circulating fluidized bed boiler needs to be quickly upgraded, the discharge plug-in door on the third feeding pipe and the fourth feeding plug-in door on the second feeding pipe are opened, and the high-temperature particles are transported to the first return pipe of the first circulating fluidized bed boiler by compressed air and sent into the hearth of the first circulating fluidized bed boiler; when any circulating fluidized bed boiler needs to be quickly downgraded, the circulating ash is made to enter the heat storage tank by compressed air. ​ 2. The circulating fluidized bed boiler heat storage type rapid startup and load change system according to claim 1, characterized by: The first feeding pipe and the second feeding pipe are connected through a third feeding pipe, and the third feeding pipe is connected to the heat storage tank.

3. The circulating fluidized bed boiler heat storage type rapid startup and load change system according to claim 2, characterized by: The third feeding pipe is provided with two branches at the middle part and connected to the heat storage tank; the connection point at the upper part of the heat storage tank is a particle inlet, and the connection point at the bottom of the heat storage tank is a particle outlet; a feeding plug-in door is arranged on the branch close to the particle inlet, and a discharge plug-in door is arranged on the branch close to the particle outlet.

4. The circulating fluidized bed boiler heat storage type rapid startup and load change system according to claim 1, characterized by: The first feeding pipe is provided with a first feeding plug-in door at one end close to the return feeder and a third feeding plug-in door at one end close to the return pipe.

5. The circulating fluidized bed boiler heat storage type rapid startup and load change system according to claim 1, characterized by: The second feeding pipe is provided with a second feeding plug-in door at one end close to the return pipe and a fourth feeding plug-in door at one end close to the return feeder.

6. The circulating fluidized bed boiler heat storage type rapid startup and load change system according to claim 1, characterized by: An air valve is arranged on each of the compressed air branch pipes.

7. The circulating fluidized bed boiler heat storage type rapid startup and load change system according to claim 1, characterized by: The connection point of the first compressed air branch pipe and the first feeding pipe is close to the first circulating fluidized bed boiler, and the connection point of the second compressed air branch pipe and the second feeding pipe is close to the second circulating fluidized bed boiler.

8. A method for heat storage type fast start-up and load change of a circulating fluidized bed boiler, using the fast start-up and load change system according to any one of claims 1 to 7, characterized by The method comprises the following steps: Firstly, high-temperature solid particles in the return feeder of the normally operating first circulating fluidized bed boiler are transported under compressed air to the hearth of the second circulating fluidized bed boiler to be started through the return pipe, so that the solid particle bed material in the hearth is quickly heated; at this time, the coal supply of the first circulating fluidized bed boiler is increased, the temperature in the hearth is kept unchanged, and the second circulating fluidized bed boiler is quickly started; when the second circulating fluidized bed boiler needs to be quickly upgraded, the operation process is the same as that of the auxiliary quick start; When any circulating fluidized bed boiler needs to reduce load rapidly, circulating ash is made to enter the heat storage tank by compressed air to improve the boiler load reduction speed and store the heat carried by solid particles; after high-temperature solid particles are stored in the heat storage tank, when the first circulating fluidized bed boiler needs to increase load rapidly, high-temperature solid particles in the heat storage tank and in the return feeder of the second circulating fluidized bed boiler are transported to the furnace of the first circulating fluidized bed boiler through the return pipe of the first circulating fluidized bed boiler by compressed air, and vice versa.

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