JP3761946B2 - Fuel supply apparatus for fluidized bed combustion furnace and cooling method thereof - Google Patents

Description

[0001]
[Technical field belonging to the invention]
The present invention relates to a fuel supply apparatus and a cooling method for a fluidized bed combustion furnace, and more particularly to a fuel supply apparatus and a cooling method for a fluidized bed boiler apparatus suitable for supplying a paste-like fuel.
[0002]
[Prior art]
A paste-like fuel (Coal Water Paste: hereinafter abbreviated as CWP) made of a mixed slurry of coal and water is used, for example, in a pressurized fluidized bed combustion apparatus (hereinafter referred to as PFBC). The fuel burns in a PFBC fluidized bed combustion furnace, and steam is generated in a heat transfer tube installed in the fluidized bed to drive the steam turbine. Further, there is known a pressurized fluidized bed boiler combined power plant that obtains electric power with high efficiency by driving a gas turbine with high-pressure and high-temperature combustion gas generated in PFBC.
[0003]
FIG. 6 shows a cross-sectional structure of a nozzle that supplies conventional CWP to a fluidized bed of a fluidized bed combustion furnace. CWP flows in from the inlet 33 of the CWP supply pipe 32 of the CWP supply nozzle 31 and is supplied from the outlet 34 to a fluidized bed combustion furnace (hereinafter sometimes referred to as a furnace) (not shown). Since the tip of the CWP supply nozzle 31 is inserted into the furnace, it is exposed to an environment of 800 ° C. to 900 ° C. during fluidized bed combustion in the furnace.
[0004]
For this reason, in order to prevent the CWP from solidifying due to temperature rise in the pipe 32 of the CWP supply nozzle 31 and blocking the CWP supply pipe 32, the CWP is supplied to the water cooling jacket 36 around the CWP supply pipe 32 through the cooling water. Cooling. Cooling water is supplied from the inlet nozzle 37, the CWP supply nozzle 31 is cooled to the vicinity of its tip, and the cooling water is discharged from the outlet nozzle 38.
[0005]
Further, the dispersed air is supplied from the inlet nozzle 41 to the dispersed air jacket 40 provided around the water cooling jacket 36, and is ejected from the dispersed air nozzle 42 at the tip of the CWP supply nozzle 31 to the CWP in the furnace to finely separate the CWP. It is dispersed to make it suitable for fluidization.
[0006]
However, since the structure of the conventional CWP supply nozzle 31 cannot cool the CWP at the tip of the nozzle 31 at the time of emergency stop, it is considered to keep the CWP in the nozzle 31 so as not to solidify as it is. Was not made.
[0007]
[Problems to be solved by the invention]
The conventional technique shown in FIG. 6 does not take into account the operation condition of emergency stop peculiar to a fluidized bed combustion furnace in the structure of the CWP supply nozzle 31 that supplies a paste-like fuel. Since it cannot be supplied at the time of stoppage, it cannot be expected that the dispersed air will cool the CWP in the furnace located at the tip of the nozzle 31, and the fuel at the tip of the nozzle 31 will be solidified. There is a problem that it is impossible to start.
[0008]
The object of the present invention is to eliminate the above-mentioned problems of the prior art, maintain the paste-like fuel in a stable temperature range without solidifying the paste-like fuel in the fuel supply nozzle pipe even at the time of emergency stop of the fluidized bed combustion furnace, and in the furnace It is an object of the present invention to provide a fuel supply apparatus for a fluidized bed combustion furnace that does not solidify the fluidized medium and a cooling method thereof.
[0009]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following configuration.
That is, in a fuel supply apparatus having a fuel supply nozzle for supplying a solid fuel with a paste-like 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. The expected minimum amount and the maximum amount of cooling water supply equivalent to the heat required for cooling required to prevent the solidification of the pasty fuel by adding liquid to the solid fuel in the past are obtained, and the fluidized bed combustion furnace is operated. The cooling method of the fuel supply apparatus injects the amount of the cooling water of the expected minimum amount at the time of an emergency stop and supplies an inert gas in an amount corresponding to the difference in the amount of cooling water between the predicted maximum amount and the expected minimum amount. .
[0010]
As another method, at the time of an emergency stop of the operation of the fluidized bed combustion furnace, first, while the fluidized bed temperature in the furnace at the initial stage of the emergency stop is a temperature sufficient to evaporate excess water, the tip of the fuel supply nozzle It is also possible to use a cooling method of a fuel supply device that performs water injection for cooling and then supplies nitrogen gas for cooling after the temperature of the fluidized medium in the fluidized bed is lowered.
[0011]
Further, the above-described problem of the present invention is achieved by the following configuration.
That is, in a fuel supply apparatus having a fuel supply nozzle for supplying a solid fuel with a paste-like fuel into a fluidized bed combustion furnace, the fuel supply nozzle includes 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 supply prevention water supply nozzle and a nitrogen supply nozzle are opened at the tip of the fuel supply pipe.
[0012]
In the fuel supply apparatus, the fuel solidification prevention water supply nozzle and the nitrogen supply nozzle may be connected to a fuel solidification prevention water supply pipe and a nitrogen supply pipe, respectively, arranged in parallel with a water cooling jacket provided on the outer periphery of the fuel supply pipe. .
[0013]
In order to prevent the tip of the fuel supply nozzle from being 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 char combustion at the tip of the nozzle (such as nitrogen gas) ) Or liquid (water, etc.) alone. However, the temperature of the fluid medium in the furnace facing the tip of the fuel supply nozzle is difficult to estimate, and the fluctuation range in actual operation is expected to be large, and the required cooling heat amount needs to be estimated very high.
[0014]
In this case, when only nitrogen gas is supplied to the tip of the fuel supply nozzle for cooling, a very large flow rate is required, which is disadvantageous in terms of cost. Further, 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 supplied water, and excess water flows out into the fluid medium in the furnace. In this case, if the temperature of the whole fluidized bed is high, excess water evaporates, but if water remains without evaporating, the fluidized medium, which is limestone, is solidified by the remaining water after the fluidized bed temperature is lowered. It is necessary to remove these solids.
[0015]
In the present invention in which the above problems of the prior art are improved, water and inert gas (nitrogen gas) supplied to the tip of the fuel supply nozzle at the time of emergency stop of the fluidized bed combustion furnace act as follows.
[0016]
Since the fuel supply nozzle inner pipe is cooled with cooling water, the fluid medium can be maintained at a temperature at which it does not solidify as a whole if the supply of cooling water can be maintained even during an emergency stop. However, the CWP at the tip of the fuel supply nozzle is solidified by the radiant heat of the furnace entering directly from the nozzle opening.
[0017]
Therefore, the present invention supplies the minimum amount of cooling water and inert gas (nitrogen gas) necessary for cooling the heat generated by the radiation at the tip of the fuel supply nozzle, so that the CWP at the tip of the fuel supply nozzle has a temperature. It prevents the rise.
[0018]
The cooling water is supplied in such an amount that the excess water does not flow out into the furnace, but there are two types of combinations of water and inert gas supply as shown in FIGS.
[0019]
The method shown in FIG. 1 supplies the expected minimum amount of water necessary for preventing CWP solidification, and an amount of nitrogen gas corresponding to the difference between the expected maximum amount and the expected minimum amount of the cooling water supply amount. To prevent excess water from flowing into the furnace.
[0020]
FIG. 2 shows that while the fluidized bed temperature in the furnace is sufficient to evaporate excess water, CWP solidification is prevented by supplying water to the fuel supply nozzle, and the fluidized bed temperature in the furnace is reduced. After the decrease, CWP solidification is prevented by inertness (nitrogen gas).
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
The fuel supply apparatus of the present invention is used, for example, in a pressurized fluidized bed combustion furnace for a pressurized fluidized bed boiler combined power plant. As a method of supplying coal to the fuel supply nozzle of the pressurized fluidized bed combustion furnace, a wet supply method is mainly adopted. That is, after adding water and a desulfurizing agent to crushed coal and mixing with a kneader to make a paste-like fluid (CWP), this is supplied to a fluidized bed boiler under pressure using a pump as fuel. To do.
[0022]
A cross-sectional view of the fuel supply nozzle structure of one embodiment of the present invention is shown in FIG. A supply nozzle 1 for supplying a paste of CWP by adding a liquid to a solid fuel of a pressurized fluidized bed boiler has a multi-pipe structure, and a double pipe around the CWP supply pipe 2 which is the innermost pipe. A water cooling jacket 3 is provided, and a dispersed air jacket 5 is provided outside the water cooling jacket 3. A heat insulating material 6 is provided between the water cooling jacket 3 and the dispersed air jacket 5. A feature of the present embodiment is that a nitrogen supply pipe 7 and a water supply pipe 9 for preventing CWP solidification are provided inside the inner pipe portion of the double water cooling jacket 3.
[0023]
A cooling water inlet nozzle 12 is provided on the inner pipe portion of the water cooling jacket 3 formed of a double pipe on the CWP inlet side of the CWP supply pipe 2, and the inner pipe portion of the water cooling jacket 3 extends from the tip of the fuel supply nozzle 1. The cooling water outlet nozzle 15 is provided on the CWP inlet side of the CWP supply pipe 2 by bypassing and connected to the outer pipe portion of the water cooling jacket 3.
[0024]
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 thereof is provided on the CWP inlet side of the CWP supply pipe 2, and an outlet nozzle 17 is provided on the water cooling jacket. 3 is provided at the tip of the inner tube portion, and nitrogen is passed through the dispersed 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 its inlet nozzle 19 is provided on the CWP inlet side of the CWP supply pipe 2, and the 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.
[0025]
The dispersed air jacket 5 is provided around the outer pipe of the water-cooled jacket 3 formed of a double pipe, but the inlet nozzle 21 is provided on the CWP inlet side of the CWP supply pipe 2 and the outlet nozzle 22 is supplied with CWP. It is provided at the tip of the tube 2.
[0026]
FIG. 4 shows a cross-sectional view of the tip of the fuel supply nozzle 1. FIG. 5 is a sectional view taken along line AA in FIG. The CWP passes through the CWP supply pipe 2 which is the innermost pipe of the fuel supply nozzle 1 and is distributed and supplied in 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. .
[0027]
In order to prevent the temperature from rising in the CWP supply pipe 2 to solidify the CWP and block the inside of the pipe, the CWP is cooled by passing cooling water through a water cooling jacket 3 around the CWP supply pipe 2. Cooling water is supplied from the inlet nozzle 12, the fuel supply nozzle 1 is cooled to the vicinity of its tip, and the cooling water is discharged from the outlet nozzle 15. Further, 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, and the CWP is finely dispersed so as to be suitable for expected fluidization. Yes.
[0028]
In this way, the CWP passes through the CWP supply pipe 2 which is the innermost pipe of the fuel supply nozzle 1 having a multi-tube structure, and flows into 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. The CWP in the pipe is cooled by the water in the cooling water jacket 3 surrounding the CWP supply pipe 2.
[0029]
When the operation of the fluidized bed combustion furnace is stopped, such as an emergency stop, the residual CWP in the CWP supply pipe 2 is cooled and water is supplied from the anti-solidification water feed nozzle 20 through the anti-solidification feed pipe 9 in order to supply necessary moisture. Water is poured into the CWP in the CWP supply pipe 2, and the paste-like fuel is held in the CWP supply pipe 2 of the fuel supply nozzle 1 in a cooled state to prevent solidification.
[0030]
Then, as shown in FIG. 1, the expected minimum amount and the expected maximum amount of cooling water supply required for preventing CWP solidification prevention at the time of emergency stop are obtained in advance according to the operating state of the fluidized bed combustion furnace. An amount of water corresponding to the required amount of heat required for cooling is injected, and an amount of nitrogen gas corresponding to the required amount of cooling required for the difference between the predicted maximum amount and the expected minimum amount is supplied. Thus, excessive water is prevented from flowing into the furnace.
[0031]
Further, as another method having the same effect, the method shown in FIG. 2 can be considered. The method is a cooling method for a fuel supply device that performs cooling water injection at the tip of the fuel supply nozzle in the early stage of an emergency stop, and then supplies cooling nitrogen gas after the temperature of the fluidized medium in the fluidized bed has decreased. . At this time, since it is difficult to predict the fluid medium temperature in the fluidized bed combustion furnace, a fluid medium temperature period sufficient to evaporate excess water according to the operating state of the fluidized bed combustion furnace is obtained in advance. During this period, cooling water is supplied to prevent CWP solidification at the nozzle tip. Thereafter, the supply of the cooling water is stopped, and an inert gas (nitrogen gas) in an amount corresponding to the necessary cooling amount after this point is supplied. In this way, even if excess water flows out into the furnace, it can be brought into a range where there is no problem. It is also effective to avoid excessive cooling by reducing the amount of cooling water and the amount of inert gas (nitrogen gas) as the flow rate of the fluidized medium is not constant.
[0032]
Nitrogen gas is supplied from the nozzle 17 to the tip of the fuel supply nozzle 1 through the nitrogen supply pipe 7 disposed in the cooling water jacket 3 to prevent being heated by the heat of the furnace.
[0033]
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 anti-caking water supply pipe 9 so that CWP is not clogged.
[0034]
Thus, according to the present invention, during the emergency stop of the fluidized bed combustion furnace, the supply of pasty fuel is stopped, and the cooling nitrogen gas and water are supplied to the CWP in the fuel supply nozzle. In addition, the water content of CWP remaining in the nozzle tube can be maintained and maintained in a stable temperature range that does not solidify, and the amount of nitrogen for cooling can be reduced and the solidification of the furnace fluidized medium due to excess cooling water can be achieved.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram of the supply amounts of water and nitrogen gas for preventing CWP solidification at a fuel supply nozzle according to the present invention.
FIG. 2 is an explanatory diagram of the supply amounts of water and nitrogen gas for preventing CWP solidification at a fuel supply nozzle according to the present invention.
FIG. 3 is a cross-sectional view of a fuel supply nozzle according to an embodiment of the present invention.
4 is a detailed view of the tip of a fuel supply nozzle in FIG. 3. FIG.
FIG. 5 is a cross-sectional view taken along line AA in FIG.
FIG. 6 is a cross-sectional view of a fuel supply nozzle in the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel supply nozzle 2 CWP supply pipe 3 Water cooling jacket 5 Dispersed air jacket 6 Heat insulating 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 Anti-solidification water supply inlet nozzle 20 Anti-solidification water supply outlet nozzle 21 Dispersed air inlet nozzle 22 Dispersed air outlet nozzle

Claims (4)

In 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,
Depending on the operating conditions of the fluidized bed combustion furnace, the expected minimum amount and the expected maximum amount corresponding to the heat required for cooling required to prevent solidification of the pasted fuel by adding liquid to the solid fuel at the time of emergency stop An amount corresponding to the difference between the predicted maximum amount and the predicted minimum amount of cooling water is injected at the time of emergency stop of the operation of the fluidized bed combustion furnace after the cooling water supply amount is obtained. A method for cooling a fuel supply apparatus, characterized by supplying an inert gas. In 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,
At the time of emergency stop of the operation of the fluidized bed combustion furnace, first, as long as the fluidized bed temperature in the furnace at the initial stage of emergency stop is sufficient to evaporate surplus water, water injection for cooling is applied to the tip of the fuel supply nozzle. And then supplying an inert gas for cooling after the temperature of the fluid medium in the fluidized bed is lowered. In 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,
The fuel supply nozzle is provided with a fuel supply pipe and a water cooling jacket provided on the outer periphery of the fuel supply pipe, and a water supply nozzle for preventing solidification of the fuel and an inert gas supply nozzle are opened at the tip of the fuel supply pipe. A fuel supply device. The fuel solidification prevention water supply nozzle and the inert gas supply nozzle are respectively connected to a fuel solidification prevention water supply pipe and a nitrogen supply pipe which are arranged in parallel with a water cooling jacket provided on the outer periphery of the fuel supply pipe. The fuel supply device according to claim 3.

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