JPH09152121A - Fuel supply apparatus of fluidized bed combustion furnace and its cooling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply a pasty fuel (CWP) into a fluidized bed combustion furnace without solidifying the fuel in a fuel supply nozzle pipe even upon emergent interruption of the fluidized bed combustion furnace. SOLUTION: Cooling water supply amounts of a predicted minimum amount and a predicted maximum amount are previously estimated which correspond to a cooling required heat amount required for preventing solidification of residual CWP in a CWP supply pipe 2 in response to an operation state of a fluidized bed combustion furnace. Upon emergency interruption of the operation of the fluidized bed combustion furnace, the cooling water amount of the predicted minimum amount is injected into the supply pipe 2 from a water supply pipe 9 through a nozzle 20. Further, inactive gas of an amount corresponding to a difference between the cooling water amounts of the predicted maximum amount and the predicted minimum amount is supplied into the supply pipe 2 from a pipe 7 through a nozzle 17. When fluidized bed temperature in the furnace in the early stage of the emergency interruption is temperature enough to vaporize excess water, the cooling water is injected through the nozzle 20, and then inactive as is supplied through the nozzle 17 after fluidized medium temperature in the fluidized bed is lowered. Thus, the excess water is prevented from flowing out into the furnace.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply apparatus for a fluidized bed combustion furnace and a cooling method thereof, and more particularly to a fuel supply apparatus for a fluidized bed boiler apparatus suitable for supplying pasty fuel and a cooling method thereof. Regarding

[0002]

2. Description of the Related Art Coal Water Paste (hereinafter referred to as "coal water paste"), which is a mixed slurry of coal and water,
CWP is, for example, a pressurized fluidized bed combustion device (hereinafter,
It is used for PFBC). The fuel is combusted in a fluidized bed combustion furnace of PFBC, and steam is generated in a heat transfer tube installed in the fluidized bed to drive a steam turbine. Further P
BACKGROUND ART There is known a pressurized fluidized bed boiler combined cycle power plant that drives a gas turbine with high-pressure and high-temperature combustion gas generated by an FBC to obtain electric power with high efficiency.

FIG. 6 shows a sectional structure of a nozzle for supplying a conventional CWP to a fluidized bed of a fluidized bed combustion furnace. CWP is CWP
The CWP supply pipe 32 of the supply nozzle 31 flows in through an inlet 33 of the CWP supply pipe 32, and from an outlet 34 thereof, a fluidized bed combustion furnace (not shown)
Sometimes called a furnace. ). Since the tip of the CWP supply nozzle 31 is inserted inside the furnace, it is exposed to the environment of 800 ° C to 900 ° C during fluidized bed combustion in the furnace.

Therefore, the CWP is the CWP supply nozzle 31.
CWP supply pipe 32 solidified by temperature rise in the pipe 32
In order to prevent the CWP from being blocked, cooling water is passed through a water cooling jacket 36 around the CWP supply pipe 32 to cool the CWP. The cooling water is supplied from the inlet nozzle 37, and the CWP
The supply nozzle 31 is cooled to the vicinity of its tip, and the cooling water is discharged from the outlet nozzle 38.

In addition, the dispersed air is introduced into a dispersed air jacket 40 provided around the water cooling jacket 36 by the inlet nozzle 4.
1 and is jetted to the CWP in the furnace from the dispersed air nozzle 42 at the tip of the CWP supply nozzle 31,
WP is finely dispersed to make it suitable for fluidization.

However, the conventional structure of the CWP supply nozzle 31 cannot cool the CWP at the tip of the nozzle 31 at the time of emergency stop, so that the CWP is held in the nozzle 31 without being solidified. No consideration was given to it.

[0007]

The prior art shown in FIG. 6 does not consider the operating condition of the fluidized bed combustion furnace, such as an emergency stop, in the structure of the CWP supply nozzle 31 for supplying the paste fuel. Since the dispersed air to be normally supplied cannot be supplied at the time of an emergency stop, the CWP in the furnace located at the tip of the nozzle 31 cannot be expected to be cooled by the dispersed air, and the tip of the nozzle 31 cannot be expected. However, there is a problem that the fuel is solidified and it becomes impossible to restart.

The object of the present invention is to eliminate the above-mentioned problems of the prior art and to solidify the pasty fuel in the fuel supply nozzle pipe at a low cost even in the emergency stop of the fluidized bed combustion furnace.
It is an object of the present invention to provide a fuel supply device for a fluidized bed combustion furnace which is maintained in a stable temperature range and which does not solidify the fluid medium in the furnace, and a cooling method thereof.

[0009]

The above object of the present invention is achieved by the following constitution. That is, in a fuel supply device having a fuel supply nozzle for supplying a paste-like fuel by adding a liquid to solid fuel into a fluidized bed combustion furnace, an emergency stop is performed in advance according to the operating state of the fluidized bed combustion furnace. Operation of the fluidized bed combustion furnace by obtaining the expected minimum amount and the maximum amount of cooling water supply corresponding to the required cooling heat amount required to prevent the solidification of the pasty fuel by adding liquid to the solid fuel In the case of an emergency stop, the cooling method of the fuel supply device is configured to inject the expected minimum amount of cooling water and to supply an amount of inert gas corresponding to the difference between the estimated maximum amount and the expected minimum amount of cooling water. .

As another method, at the time of an emergency stop of the operation of the fluidized bed combustion furnace, first, while the temperature of the fluidized bed in the furnace at the beginning of the emergency stop is a temperature sufficient to evaporate the excess water,
It is also possible to use a cooling method of the fuel supply device in which water for cooling is injected to the tip of the fuel supply nozzle and then the temperature of the fluidized medium in the fluidized bed is lowered before supplying nitrogen gas for cooling.

The above object of the present invention can be achieved by the following constitution. That is, in a fuel supply device having a fuel supply nozzle for supplying a paste-like fuel by adding a liquid to a solid fuel into a fluidized bed combustion furnace, the fuel supply nozzle has a fuel supply pipe and an outer periphery of the fuel supply pipe. The fuel supply device is provided with a water cooling jacket provided in the fuel supply pipe, and a fuel solidification preventing water supply nozzle and a nitrogen supply nozzle are opened at the tip of the fuel supply pipe.

In the above fuel supply device, the fuel solidification preventing water supply nozzle and the nitrogen supply nozzle are connected to the fuel solidification preventing water supply pipe and the nitrogen supply pipe, respectively, which are juxtaposed to the water cooling jacket provided on the outer periphery of the fuel supply pipe. May be.

As a countermeasure against the fact that the tip of the fuel supply nozzle is heated by the heat in the fluidized bed combustion furnace during an emergency stop of the fluidized bed combustion furnace, an inert gas that does not cause residual coal combustion at the tip of the nozzle ( There is a method of cooling with a single substance such as nitrogen gas or liquid (such as water). However, it is difficult to estimate the temperature of the fluidized medium in the furnace facing the tip of the fuel supply nozzle, and it is expected that the fluctuation range in actual operation will be large. Therefore, it is necessary to estimate the required cooling heat quantity to be very high.

In this case, when supplying only nitrogen gas to the tip of the fuel supply nozzle for cooling, a very large flow rate is required, which is disadvantageous in terms of cost. Also, when only water is supplied for cooling the tip of the fuel supply nozzle, the flow rate actually used for cooling is smaller than the flow rate of the injected water, and excess water flows out into the fluidized medium in the furnace. in this case,
Excess water evaporates if the temperature of the entire fluidized bed is high, but if water remains without evaporation, the fluidized medium, which is limestone, may solidify due to the remaining water after the fluidized bed temperature has dropped. There is a need to remove these solids.

In the present invention which has improved the above-mentioned problems of the prior art, water and inert gas (nitrogen gas) supplied to the tip of the fuel supply nozzle at the time of an emergency stop of the fluidized bed combustion furnace act as follows.

Since the periphery of the inner tube of the fuel supply nozzle is cooled by cooling water, it is possible to keep the temperature of the fluidized medium as a whole at a temperature at which it does not solidify if the supply of cooling water can be maintained even during an emergency stop. However, C at the tip of the fuel supply nozzle
The WP is solidified by the radiant heat of the furnace directly entering from the nozzle opening.

Therefore, according to the present invention, the minimum amount of cooling water and inert gas (nitrogen gas) necessary for cooling the heat of radiation generated by the radiation at the tip of the fuel supply nozzle is supplied to the tip of the fuel supply nozzle. It is intended to prevent the temperature of the CWP from rising.

The cooling water is supplied in such an amount that the excess water does not flow into the furnace. There are two types of combinations of water and the supply amount of the inert gas as shown in FIGS.

The method shown in FIG. 1 supplies the expected minimum amount of water required for the prevention of CWP solidification, and an amount corresponding to the difference between the estimated maximum amount and the expected minimum amount of the cooling water supplied. The supply of nitrogen gas prevents excessive water from flowing into the furnace.

In FIG. 2, while the temperature of the fluidized bed in the furnace is a temperature sufficient to evaporate the excess water, the water is supplied to the fuel supply nozzle to prevent the solidification of the CWP, and After the fluidized bed temperature has dropped, the idea is to prevent CWP solidification by inertness (nitrogen gas).

[0021]

Embodiments of the present invention will be described below. The fuel supply device of the present invention is used, for example, in a pressurized fluidized bed combustion furnace for a pressurized fluidized bed boiler combined cycle power plant. A wet supply method is mainly adopted as a method for supplying coal to the fuel supply nozzle of the pressurized fluidized bed combustion furnace. That is, water and a desulfurizing agent are added to crushed coal and mixed by a kneader to form a paste-like fluid (CWP).
After that, this is supplied as fuel to a fluidized bed boiler in a pressurized state using a pump.

FIG. 3 is a sectional view showing the structure of the fuel supply nozzle according to the embodiment of the present invention. The supply nozzle 1 for supplying a CWP in a paste form by adding a liquid to the solid fuel of the pressurized fluidized bed boiler has a multi-tube structure, and has a double tube around the CWP supply tube 2 which is the innermost tube. A water cooling jacket 3 is provided, and a distributed air jacket 5 is provided outside the water cooling jacket 3.
Is provided. A heat insulating material 6 is provided between the water cooling jacket 3 and the dispersed air jacket 5. The feature of this embodiment is that a nitrogen supply pipe 7 and a water supply pipe 9 for preventing solidification of CWP are provided inside the inner pipe portion of the double water cooling jacket 3.

On the inlet side of the CWP of the CWP supply pipe 2, a cooling water inlet nozzle 12 is provided in the inner pipe portion of the water cooling jacket 3 consisting of a double pipe, and the inner pipe portion of the water cooling jacket 3 is connected to the fuel supply nozzle 1. The CWP of the CWP supply pipe 2 is connected to the outer pipe portion of the water cooling jacket 3 bypassing from the tip.
An outlet nozzle 15 for cooling water is provided on the inlet side of.

A nitrogen supply pipe 7 is provided so as to penetrate a part of the inner pipe of the double water cooling jacket 3. An inlet nozzle 16 of the nitrogen supply pipe 7 is provided on the CWP introduction port side of the CWP supply pipe 2 and an outlet nozzle 17 thereof. Is provided at the tip of the inner tube portion of the water cooling jacket 3, and nitrogen is passed through the dispersion air jacket 5. Further, a solidification preventing water supply pipe 9 is provided so as to penetrate the other part of the inner pipe of the water cooling jacket 3, and an inlet nozzle 19 thereof is provided on the CWP introduction port side of the CWP supply pipe 2 and an outlet nozzle 20. Is open to the CWP supply pipe 2 on the tip side of the inner pipe portion of the water cooling jacket 3.

A dispersion air jacket 5 is provided around the outer tube of the water cooling jacket 3 consisting of a double tube. The inlet nozzle 21 is provided on the CWP introduction port side of the CWP supply pipe 2 and the outlet nozzle 22. Is provided at the tip of the CWP supply pipe 2.

FIG. 4 shows a sectional view of the tip of the fuel supply nozzle 1. Further, FIG. 5 shows a cross-sectional view taken along the line AA of FIG. The CWP passes through the CWP supply pipe 2 which is the innermost pipe of the fuel supply nozzle 1, and is dispersed and supplied into a furnace fluidized bed (not shown) by the dispersed air blown from the dispersed air nozzle 22 at the outlet of the fuel supply nozzle 1. .

When the temperature rises in the CWP supply pipe 2, the CWP
CW is prevented from solidifying and blocking the inside of the pipe.
The CWP is cooled by passing cooling water through the water cooling jacket 3 around the P supply pipe 2. The cooling water is supplied from the inlet nozzle 12, cools the fuel supply nozzle 1 to the vicinity of its tip, and the cooling water is discharged from the outlet nozzle 15. In addition, the dispersed air supplied from the dispersed air inlet nozzle 21 is jetted into the CWP from the dispersed air outlet nozzle 22 at the tip of the fuel supply nozzle 1 to disperse the CWP finely and make it suitable for the expected fluidization. There is.

As described above, the CWP passes through the CWP supply pipe 2 which is the innermost pipe of the fuel supply nozzle 1 having the multi-pipe structure,
The CWP in the pipe is the water in the cooling water jacket 3 surrounding the CWP supply pipe 2 by being dispersed and supplied in the furnace fluidized bed by the dispersed air blown from the dispersed air outlet nozzle 22 at the outlet of the fuel supply nozzle 1. It is cooled.

When the operation of the fluidized bed combustion furnace is stopped, such as during an emergency stop, the residual CWP in the CWP supply pipe 2 is cooled and necessary water is supplied. Therefore, the solidification prevention water supply pipe 9 is used to prevent solidification prevention water supply nozzle 20. CWP supply pipe 2 of fuel supply nozzle 1 by pouring more water into CWP in CWP supply pipe 2
The paste-like fuel is kept cool inside to prevent it from solidifying.

Then, as shown in FIG. 1, the expected minimum amount and the expected maximum amount of cooling water supply required to prevent solidification of CWP at the time of an emergency stop are obtained in advance according to the operating state of the fluidized bed combustion furnace. The amount of water corresponding to the required minimum amount of heat required for cooling is injected, and the amount of nitrogen gas corresponding to the required amount of cooling heat for the difference between the expected maximum amount and the expected minimum amount is supplied. In this way, excess water is prevented from flowing into the furnace.

As another method that achieves the same effect, the method shown in FIG. 2 can be considered. The method is to inject water for cooling to the tip of the fuel supply nozzle at the beginning of an emergency stop,
Next, it is a cooling method of the fuel supply device which supplies the nitrogen gas for cooling after the temperature of the fluidized medium in the fluidized bed is lowered. At this time, it is difficult to predict the temperature of the fluidized medium in the fluidized bed combustion furnace, so a sufficient fluidized medium temperature period for evaporating excess water should be obtained in advance according to the operating state of the fluidized bed combustion furnace. During this period, cooling water is supplied to prevent CWP solidification at the nozzle tip. After that, supply of cooling water was stopped,
An inert gas (nitrogen gas) in an amount corresponding to the required cooling amount after this time is supplied. In this way, it is possible to set the range in which there is no problem even if excess water flows into the furnace. Further, it is also effective to avoid the excessive cooling by reducing the cooling water amount and the inert gas (nitrogen gas) amount at a constant flow rate as the temperature of the fluid medium decreases.

The nitrogen gas is supplied from the nozzle 17 to the tip of the fuel supply nozzle 1 through the nitrogen supply pipe 7 arranged in the cooling water jacket 3 to prevent it from being heated by the heat of the furnace.

During normal operation of the fluidized bed combustion furnace, it is desirable to supply a small amount of air to the nitrogen supply pipe 7 and the solidification preventing water supply pipe 9 so that the CWP does not become clogged.

As described above, according to the present invention, at the time of an emergency stop of the fluidized bed combustion furnace, the supply of the pasty fuel is stopped and the cooling nitrogen gas and water are supplied to the CWP in the fuel supply nozzle. By doing so, it is possible to maintain the water content of the CWP remaining in the nozzle pipe and maintain it in a stable temperature range where it does not solidify, reduce the amount of cooling nitrogen, and prevent solidification of the furnace fluid medium due to excess cooling water. You can

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of supply amounts of water and nitrogen gas for preventing CWP solidification in a fuel supply nozzle according to the present invention.

FIG. 2 is an explanatory diagram of supply amounts of water and nitrogen gas for preventing CWP solidification in the fuel supply nozzle according to the present invention.

FIG. 3 is a sectional view of a fuel supply nozzle according to an embodiment of the present invention.

FIG. 4 is a detailed view of the tip of the fuel supply nozzle of FIG.

FIG. 5 is a sectional view taken along line AA of FIG. 4;

FIG. 6 is a cross-sectional view of a fuel supply nozzle according to the related art.

[Explanation of symbols]

1 Fuel Supply Nozzle 2 CWP Supply Pipe 3 Water Cooling Jacket 5 Dispersed Air Jacket 6 Insulation Material 7 Nitrogen Supply Pipe 9 Water Supply Pipe for CWP Solidification Prevention 12 Cooling Water Inlet Nozzle 15 Cooling Water Outlet Nozzle 16 Nitrogen Inlet Nozzle 17 Nitrogen Outlet Nozzle 19 Solidification Prevention Water Supply Inlet Nozzle 20 Solidification Prevention Water Supply Outlet Nozzle 21 Dispersed Air Inlet Nozzle 22 Dispersed Air Outlet Nozzle

Claims (4)

[Claims] 1. A fuel supply device having a fuel supply nozzle for supplying a paste-like fuel by adding a liquid to a solid fuel into a fluidized bed combustion furnace, in advance according to an operating state of the fluidized bed combustion furnace. Addition of liquid to solid fuel at the time of emergency stop to obtain the minimum and expected maximum amount of cooling water supply that corresponds to the required cooling heat amount required to prevent the solidification of the fuel in paste form At the time of emergency stop of the operation of the furnace, while injecting the expected minimum amount of cooling water, the amount of inert gas corresponding to the difference between the expected maximum amount and the expected minimum amount of cooling water is supplied. Fuel supply device cooling method. 2. A fuel supply apparatus having a fuel supply nozzle for supplying a paste-like fuel by adding a liquid to a solid fuel into a fluidized bed combustion furnace. While the temperature of the fluidized bed in the furnace at the beginning of an emergency shutdown is sufficient to evaporate excess water, cooling water is injected at the tip of the fuel supply nozzle, and then the temperature of the fluidized medium in the fluidized bed drops. A method for cooling a fuel supply device, comprising supplying an inert gas for cooling after that. 3. A fuel supply device having a fuel supply nozzle for supplying a paste-like fuel by adding a liquid to solid fuel into a fluidized bed combustion furnace, wherein the fuel supply nozzle has a fuel supply pipe and the fuel supply. A fuel supply device characterized in that a water cooling jacket provided on the outer circumference of the pipe is provided, and a fuel solidification preventing water supply nozzle and an inert gas supply nozzle are opened at the tip of the fuel supply pipe. 4. The fuel solidification preventing water supply nozzle and the inert gas supply nozzle are connected to a fuel solidification preventing water supply pipe and a nitrogen supply pipe, which are juxtaposed to a water cooling jacket provided on the outer periphery of the fuel supply pipe. The fuel supply device according to claim 3, wherein