JP3219294B2 - Fluidized bed boiler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressurized fluidized-bed combustion furnace for coal, which drives a gas turbine and a steam turbine to perform combined power generation, and in particular, controls the gas flow rate in the furnace to cope with starting and stopping of a boiler. The present invention relates to a pressurized fluidized-bed boiler provided with a device for performing the above.

[0002]

2. Description of the Related Art A feature of a pressurized fluidized bed boiler lies in the downsizing of the boiler and the improvement of power generation efficiency by combined cycle power generation. If fuel such as coal is burned in a pressurized state, the combustion load (hearth load) while maintaining almost the same gas flow velocity in the furnace
Can be increased to nearly 20 times that of a normal pressure fluidized bed boiler. Coal is a mixture with water (coal water slurry: CW
P), and pressurized and supplied into the combustion furnace by a pump. In the combustion furnace, the CWP burns while flowing by the combustion air, and the exhaust gas is guided from the combustion furnace to a dust remover and a gas turbine.

FIG. 4 shows an example of the prior art. The pressurized fluidized-bed boiler includes a pressure vessel 7, a combustion furnace 1, a dust remover 11, a gas turbine 12, a steam turbine 18, and the like.

[0004] The combustion furnace 1 is housed in a pressure vessel 7, and an air dispersion plate 6 is provided at the bottom thereof, and the fluid medium particles 2 are filled thereon. Pressurized air 8 is in pressure vessel 7
After being supplied to the inside, the air is supplied into the combustion furnace 1 as combustion air via a wind box 24 below the air dispersion plate 6, and the medium particles 2 are fluidized to form a fluidized bed 10. In the wind box 24,
A damper 23 for adjusting the air flow rate is provided. Further, outside the pressure vessel 7, a starting burner 25 connected to the wind box 24 is provided.

The combustion furnace 1 is supplied with C through a slurry conduit 17.
The coal / water slurry 26 is pumped from the WP pump 9 and supplied from the slurry spray nozzle 16 into the fluidized bed 10 for combustion.

The flue gas containing coal ash discharged from the fluidized-bed combustion furnace 1 is discharged from the upper part of the fluidized-bed combustion furnace 1 through an exhaust gas line 13, and dust contained in the flue gas is removed by the cyclone 5. Further, the exhaust gas removes combustion ash and the like contained in the combustion exhaust gas by a dust remover 11 provided outside the pressure vessel 7, and only the clean exhaust gas is introduced into the gas turbine 12.

The gas turbine 12 collects the energy of the exhaust gas to generate electric power by a generator 14, and drives a compressor 15 as a combustion air source. The exhaust gas discharged from the gas turbine 12 is supplied to a subsequent heat exchanger 21.
And discharged from the chimney 22.

In FIG. 4, 3 is a heat transfer tube, 4 is B
M tank, 19 is a generator, 20 is a cooler (condenser).

As a method for starting the pressurized fluidized-bed boiler, a method is used in which a starter burner 25 is provided in a wind box 24 below the air distribution plate 6 to assist the fluidized medium particles 2 in combustion. Start-up burner 25
When the temperature of the fluid medium 2 in the fluidized bed 10 reaches a predetermined temperature due to the combustion air and the fuel, coal (or coal water slurry: CWP) as a fuel is supplied into the fluidized bed 10 from the slurry conduit 17. In the fluidized bed 10, ignition and combustion of coal are started almost simultaneously with the supply of coal (or coal water slurry: CWP). At this time, it is important that the fluid medium particles in the fluidized bed 10 maintain a stable fluidity.

[0010]

In the conventional system,
It is difficult to keep the gas flow rate in the fluidized bed constant. The gas flow velocity in the fluidized bed is determined by the gas flow rate, temperature, and pressure in the fluidized bed, but the pressure in the fluidized bed cannot be arbitrarily controlled because the resistance of the gas turbine is constant.
In particular, it is difficult to adjust the gas flow rate in the fluidized bed to a predetermined value because the temperature in the fluidized bed becomes unstable and the combustion gas cannot be arbitrarily adjusted at startup.

[0011] When the gas flow rate becomes smaller than a predetermined value, the medium particles in the combustion furnace become a fixed bed, which causes clinkers such as flowing medium particles.

On the other hand, when the gas flow velocity in the furnace becomes high, the fluidized medium in the fluidized bed scatters outside the combustion furnace system, media particles in the fluidized bed disappear, and the fluidized bed height cannot be maintained. Therefore, there arises a problem that the medium particles must be supplied again into the combustion furnace. Such a phenomenon causes a similar problem when the fluidized-bed boiler is stopped.

The present invention solves the above-mentioned drawbacks of the conventional method, and causes clinker trouble of media particles in a fluidized bed, loss of fluid medium particles, or blockage trouble of a dust remover when starting and stopping a pressurized fluidized bed boiler. It is an object of the present invention to propose a pressurized fluidized bed combustion furnace provided with a control device for smoothly starting and stopping a boiler without performing.

[0014]

The object of the present invention is to provide a bypass pipe and a bypass valve for bypassing a gas turbine between an inlet of the gas turbine and an outlet of the gas turbine, and further provide a furnace pressure, a furnace temperature, and a combustion air amount. Can be solved by calculating the gas flow rate in the furnace by simultaneously measuring the flow rate of the furnace and adjusting the opening of the bypass valve so that the furnace pressure always becomes a predetermined value.

[0015]

According to the present invention, the flow rate of the furnace is adjusted by adjusting the opening of the bypass valve. That is, when the gas flow rate in the fluidized bed becomes higher than a predetermined value, the bypass valve is closed to pressurize the inside of the fluidized bed. Conversely, when the gas flow rate becomes lower than the predetermined value, the bypass valve is opened to flow the gas. By reducing the pressure in the layer, the gas flow rate is adjusted to a predetermined range.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a pressurized fluidized bed boiler according to an embodiment of the present invention, and FIG. 2 is a schematic control system diagram of a pressurized fluidized bed boiler showing another embodiment.

In FIG. 1, the pressurized fluidized-bed boiler includes a pressure vessel 7, a combustion furnace 1, a dust remover 11, a gas turbine 12, a steam turbine 18, and the like.

The combustion furnace 1 is housed in a pressure vessel 7, and an air distribution plate 6 is provided at the bottom thereof, and the fluid medium 2 is filled thereon. After the pressurized air 8 is supplied into the pressure vessel 7, it is supplied into the combustion furnace 1 as combustion air via a wind box 24 below the air distribution plate 6, and fluidizes the medium particles 2 to form a fluidized bed 10. To form The wind box 24 is provided with a damper 23 for adjusting an air flow rate. Further, a start-up burner 25 connected to the wind box 24 is provided outside the pressure vessel 7.

The combustion furnace 1 has a slurry conduit 17 through which C
The coal / water slurry 26 is pumped from the WP pump 9 and supplied from the slurry spray nozzle 16 into the fluidized bed 10 for combustion. The combustion furnace 1 is provided with a thermometer 30 for measuring the temperature and pressure in the fluidized bed 10 and pressure gauges 31a to 31c.

Coal / water slurry 2 burned in combustion furnace 1
The exhaust gas 6 is discharged from the upper part of the combustion furnace 1 through an exhaust gas line 13 as a combustion gas containing dust. Dust contained in the exhaust gas is removed by the cyclone 5, and furthermore, the pressure vessel 7
The gas turbine 1 is removed by a dust remover 11 provided outside the gas turbine 1.
2 is introduced.

The gas turbine 12 recovers the energy of the exhaust gas to generate power, and drives the compressor 15 which is a combustion air source. The exhaust gas discharged from the gas turbine 12 is introduced into the subsequent heat exchanger 21 and
Exhausted from 2.

As shown in FIG. 1, the exhaust gas line 13 is provided with a bypass pipe 35 and a bypass valve 32 for bypassing the gas turbine 12 from the inlet to the outlet of the gas turbine 12. The bypass valve 32 of the bypass pipe 35
This is provided to keep the gas flow rate in the fluidized bed 10 constant.

Hereinafter, the gas flow velocity in the fluidized bed 10 will be described.

Since the cross-sectional area A (m ² ) of the furnace is constant, the gas flow velocity V ₀ (m / s) in the fluidized bed is equal to the furnace pressure P
(Kg / cm ² .g.), The furnace temperature T (° C.) and the combustion air amount Q (m ³ / s) can be easily calculated by the mathematical formula shown in FIG.

In particular, at the time of start-up, the medium temperature in the furnace significantly changes even if the combustion air amount Q is constant. Therefore, as is clear from the equation in FIG. 3, the gas flow velocity V ₀ changes significantly.
That is, since the temperature of the medium particles 2 gradually increases from the normal temperature, the gas flow velocity V ₀ increases. Gas flow velocity V ₀
It is also conceivable to change the combustion air amount Q in order to adjust the fuel consumption. However, it is important that the combustion air amount Q is proportional to the fuel at the time of starting, and that the combustion exhaust gas be maintained at a normal value. Not possible. From the above, the method of changing the furnace pressure is most effective in maintaining the gas flow rate V ₀ in the furnace at a predetermined value at the time of startup.

As described above, in the embodiment shown in FIG.
A bypass pipe 35 and a bypass valve 32 are provided in order to maintain the gas flow velocity V ₀ at a predetermined value. When the gas flow velocity V ₀ becomes higher than the predetermined value, the bypass valve 32 is closed to pressurize the fluidized bed 10, When the flow velocity V ₀ becomes lower than the predetermined value, the bypass valve 32 is opened to lower the pressure of the fluidized bed 10,
Adjusting the gas flow velocity V ₀ to a predetermined value.

In this embodiment, a pressure gauge 31a is arranged in the wind box 24, a pressure gauge 31b is arranged in the fluidized bed 10, and a pressure gauge 31c is arranged in the empty tower of the furnace 1, and these pressure detection values are measured. calculates the gas flow velocity V ₀ based on the (differential pressure) and the boiler load, and compares the preset reference value in response to the gas flow velocity V ₀ and the boiler load.

The basis for setting the gas flow velocity will be described below.

In the fluidized bed apparatus, conditions for stably flowing the medium particles must be ensured, and for that purpose, a gas flow rate that is higher than the fluidization start speed of the medium particles is required. Further, in order to prevent scattering of the medium particles from the inside of the fluidized bed and obtain a high heat absorption amount by the heat transfer tube, it is important to operate the gas at a gas flow rate of 5 times or less of the fluidization start speed.

Of course, the fluidization start speed differs depending on the properties of the particles (density, particle diameter, etc.) and the properties of the gas. For example, when the average particle diameter of the medium particles is 0.50 mm, the fluidized bed formation speed is 0.15 m / s, and when the average particle diameter is 1.0 mm, the fluidized bed formation speed is 0.4 m / s. 0m
In the case of m, the fluidized bed start speed is 1.1 m / s. As described above, the fluidization start speed increases with an increase in the average particle size of the medium particles, but in any case, as described above, in order to obtain a stable flow of the medium particles in the fluidized bed, the gas flow velocity is increased. Is preferably 1.5 to 5 times the fluidization start speed.

Generally, in a pressurized fluidized bed, the gas flow rate is 0.6
It is operated in a range of up to 2.0 m / s. This has a problem that when the gas flow rate is set to 2 m / s or more, wear of the heat transfer tube provided in the fluidized bed increases. On the other hand, when the gas flow rate is set to 0.5 m / s or less, there is a disadvantage that the cross-sectional area of the fluidized bed furnace increases and the entire apparatus becomes large. As described above, in the pressurized fluidized bed boiler, generally, the range of the operating gas flow velocity is optimally 0.6 to 2.0 m / s as described above. Therefore, the gas flow rate is determined in consideration of the fluidization start speed obtained from the particle properties, and a method of setting the range to 1.5 to 5 times the fluidization start speed is adopted.

FIG. 2 shows another embodiment. FIG.
1 is that the gas flow rate V ₀ of the fluidized bed 10 is adjusted by providing a bypass pipe 35 and a bypass valve 32 in the apparatus of FIG. A pressure gauge 31, an air flow meter 34, and a calculator 33 are provided, and a temperature detection signal 36 from the thermometer 30, a pressure detection signal 37 from the pressure gauge 31, and an air flow detection signal 38 from the air flow meter 34 are calculated by the calculator 33. And the calculator 33 calculates the gas flow velocity V ₀ in the fluidized bed 10 in the equation of FIG. Then, the gas flow rate detection signal and the gas flow rate setting signal 39 are compared by the computing unit 33, and when the gas flow rate detection signal is larger than the gas flow rate setting signal 39, the bypass valve 32 is closed. On the other hand, when the gas flow rate detection signal is smaller than the gas flow rate setting signal 39, the control is performed so that the bypass valve 32 is opened.

That is, it is interlocked with the calculator 33 for calculating the detection signals 36 and 37 from the thermometer 30 and the pressure gauge 31 provided in the combustion furnace 1. The calculator 33 includes a thermometer 30, a pressure gauge 31, and an air flow meter 3 provided in the fluidized-bed combustion furnace 1.
Based on the detection signals 36, 37, 38 from 4, the gas flow rate V ₀ in the fluidized bed 10 is calculated in real time, and a control signal 40 for adjusting the valve opening is sent to the bypass valve 32.

The gas flow rate detection signal in the combustion furnace 1 is
The gas flow rate, temperature, and pressure inside the fluidized bed can be calculated by the equations shown in FIG. 3. Particularly, at the time of startup, since the temperature inside the fluidized bed 10 gradually increases with a predetermined amount of air, the temperature inside the fluidized bed changes every moment. The gas flow velocity V ₀ in the inside cannot be arbitrarily adjusted. Accordingly, by controlling the pressure of the combustion furnace 1, the gas flow rate V in the fluidized bed is controlled.
₀ can be easily controlled.

Thus, when the pressurized fluidized bed boiler is started,
Even at the time of stop, the gas flow velocity V ₀ can be kept substantially constant, and clinker trouble of the medium particles 2 and scattering of the medium particles 2 can be prevented.

[0037]

According to the present invention, the start and stop of the boiler can be performed without causing a clinker trouble of the medium in the fluidized bed, a trouble of missing the fluid medium particles, or a trouble of closing the dust remover when the boiler is started and stopped. The pressurized fluidized-bed boiler can be performed smoothly and can be provided with high reliability.

Further, the present invention can be used as an emergency discharge valve for adjusting the pressure in the fluidized bed in an emergency. In addition, the released flue gas can remove pollutants such as nitrogen oxides in a subsequent flue gas treatment device (such as denitration), and it is safe, non-polluting and highly reliable in pressurized fluidized bed boilers even in an emergency. Can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a pressurized fluidized-bed boiler according to an embodiment of the present invention.

FIG. 2 is a schematic control system diagram of a pressurized fluidized-bed boiler showing another embodiment.

FIG. 3 is a diagram showing a mathematical expression.

FIG. 4 is a schematic configuration diagram of a pressurized fluidized bed boiler according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion furnace 2 Medium particle 3 Heat transfer tube 5 Cyclone 6 Air dispersion plate 7 Pressure vessel 8 Pressurized air 9 CWP pump 10 Fluidized bed 12 Gas turbine 14 Generator 17 Slurry conduit 21 Heat exchanger 22 Chimney 24 Wind box 26 Coal / water slurry

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuki Masaji 3-36 Takara-cho, Kure City, Hiroshima Prefecture Inside the Kure Research Institute, Inc. (72) Inventor Kenji Higashikawa 3-36 Takara-cho Kure City, Hiroshima Prefecture Babkotsuk Day (72) Inventor Taro Sakata, 3-36 Takara-cho, Kure-shi, Hiroshima Prefecture Babkotsuk Day Inside Kure Factory, Ltd. (72) Inventor Kodai Nonaka 3-36, Takara-cho, Kure-shi, Hiroshima Prefecture Babkotsuk Day Kure Factory Co., Ltd. (72) Inventor Akio Nishiyama 3-36 Takaracho, Kure City, Hiroshima Pref. Bab Kokitsu Co., Ltd. Kure Factory Co., Ltd. (56) References JP-A-5-26057 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) F02C 3/26 F02C 9/18 F23C 11/02

Claims (1)

(57) [Claims] 1. A furnace having a fluidized bed, a gas turbine that supplies and rotates a combustion gas from the furnace, an exhaust gas line connecting the furnace and the gas turbine, and a gas that detects a gas flow rate in the furnace. A gas flow detecting means, a gas branch pipe provided on the gas turbine upstream side of the exhaust gas line, and a flow regulating valve provided in the middle of the gas branch pipe, wherein a gas flow rate in the furnace is preset. The fluidized-bed boiler is configured to operate the flow control valve when the gas flow rate falls below the gas flow rate to branch the combustion gas in the furnace from the gas branch pipe.