JPH06257719A - Fluidized bed boiler - Google Patents

Abstract

PURPOSE:To provide a fluidized bed type boiler having a cooling device for fuel ashes in which the ash cooling facility is simplified in its construction and the facility cost is reduced. CONSTITUTION:Supplied water for use in making coal water paste is heated through coolers 18A, 18B and 18C for cooling ashes within discharged gas got from a furnace 1, thereafter mixed with coal by a kneading machine 5 and the like and supplied to the furnace 1, so that heat generated by cooling the ashes is effectively utilized. Even if supplied water is leaked toward the ashes due to friction within the ash cooling devices 18A, 18B and 18C, a water supplying system is being operated normally at a lower pressure than that of the ashes, so that the supplied water for use in making coal and water paste is not lacked under an excessive leakage. In addition, even if the ashes are leaked at the water supplying side, a certain small amount of ashes are mixed with coal, supplied to the furnace 1 and finally collected at a cycline 11 and a filter 12 and so it is not necessary to stop the operation of the plant immediately and repairing of the ash coolers 18A, 18B and 18C can be carried out without any trouble.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus, and more particularly to a boiler apparatus capable of efficiently recovering waste heat of a plant and suitable for improving plant efficiency.

[0002]

2. Description of the Related Art A conventional fluidized bed boiler is shown in FIG. 2 by taking a pressurized fluidized bed boiler as an example. The furnace 1 housed in the pressure vessel 2 is provided with an air dispersion plate 10 at the bottom thereof, and fluid medium particles (not shown) are filled on the air dispersion plate 10. Then, the compressed air compressed by the air compressor 9 is supplied to the pressure vessel 2 and then supplied as combustion air through the air dispersion plate 10 into the furnace 1 to fluidize the fluidized medium to form a fluidized bed ( (Not shown). On the other hand, coal bunker 3
Coal as a fuel from limestone and limestone as a desulfurizing agent from the limestone bunker 4 are kneaded in a kneading machine 5 together with water sent from a water storage tank 21 by a water supply pump 22, and then sent to a fuel supply tank 6 for storage. The fuel mixture in the fuel supply tank 6 is pressurized by the fuel supply pump 7 and then blown into the fluidized bed in the furnace 1 by the fuel supply nozzle 8. Further, the combustion exhaust gas discharged from the furnace 1 is dust-removed by the cyclone 11 and then introduced into the gas turbine 13 through the filter 12. The paste water valve 24 is a control valve for not supplying an excessive amount of water.

The combustion exhaust gas from the furnace 1 is dust-removed by the cyclone 11 and the filter 12 and is sent to the gas turbine 13. After the exhaust gas is recovered by the exhaust heat recovery device 14A, it is exhausted from the chimney 14B. Further, the fluid in the furnace 1, the collected ash of the cyclone 11 and the collected ash of the filter 12 are extracted from the ash extraction pipes 17A to 17C, respectively, and cooled by the respective ash coolers 18A to 18C, and then the ash is collected. The pressure is reduced to the atmospheric pressure by the lock hoppers 19A to 19C and sent to the ash cyclone 20.

In the above pressurized fluidized bed boiler plant,
Since the gas turbine 13 is driven by the combustion exhaust gas, the exhaust gas is sent to the gas turbine 13 as it is at a high temperature of about 850 ° C. without being cooled. However, since the exhaust gas contains dust of about tens of thousands of mg / Nm ³ , if it is sent to the gas turbine 13 as it is, the blades of the gas turbine 13 will be worn, so it is necessary to remove dust at the inlet of the gas turbine 13. The ash collected here is also collected at a high temperature of about 850 ° C, so 100% is required to treat this ash.
It must be cooled to about 200 ° C.

Therefore, the conventional fluidized bed boiler plant has ash coolers 18A to 18C for cooling high temperature ash as shown in FIG. Each ash cooler 18
Cooling water pump 25 to cooling water pump 26 for A to 18C
The cooling water is supplied by the ash cooler 18A.
Since the temperature rises in the process of passing through ~ 18C, it is returned to the cooling water cooling tower 25 once, cooled, and then cooled again by the ash cooler 18A,
Cooling water circulation equipment sent to B and C is required.

In addition to this, without using the cooling water cooling tower 25, as shown in the pressurized fluidized bed boiler plant of FIG. 3, boiler feed water 15 supplied to the heat transfer tubes of the furnace 1 is supplied to the ash coolers 18A to 18A. It may be supplied to 18C to cool each ash.

[0007]

In the conventional pressurized fluidized bed boiler plant shown in FIG. 2, the high temperature fuel ash is cooled,
Furthermore, the cooling water cooling tower 25 for cooling the high temperature cooling water is required, and the equipment for that and the on-site power for operating the cooling tower 25 and the cooling water pump 26 were needed. Therefore, the increase in the motive power for cooling the ash has led to a decrease in the efficiency at the transmission end of the plant.

Further, in the pressurized fluidized bed boiler plant shown in FIG. 3 which emphasizes plant efficiency, the boiler feed water 1
By utilizing No. 5 and recovering the cooling recovery heat of the high temperature ash as the heat of the boiler steam system, the plant efficiency was improved. However, in this method, the ash cooler 18A should be used.
When ash leaks to the water supply 15 side due to wear within ~ 18C, and conversely, the water supply 15 leaks to the ash side (Which leakage occurs depends on the pressure balance between the cooling water side and the ash side) Since it affects the steam system of the boiler, it is necessary to stop the plant immediately, which is a problem in terms of plant reliability. In addition, especially the former ash is water supply 15
In the case of leakage to the side, if this leakage state continues for a long time, fine dust may reach the steam turbine 13, causing damage to the blades of the steam turbine 13, leading to a serious accident.

Further, compared with the case where the cooling water of the fuel ash cooling system of FIG. 2 is room temperature water of 20 ° C., the boiler feed water temperature of FIG. 3 is usually 100 to 200 ° C., which is a high temperature.
The contact area of the heat exchange fluid necessary for cooling the high temperature ash to 200 ° C. is inevitably increased, and the size of the ash cooler 18 is extremely large. Further, in some cases, the fuel ash cannot be cooled down to the target temperature unless the two fuel ash cooling methods shown in FIGS. 2 and 3 are installed in combination, which complicates the ash cooling facility, resulting in a facility cost. There was also an increasing problem. Therefore, an object of the present invention is to provide a fluidized bed boiler equipped with a fuel ash cooling device that simplifies ash cooling equipment and reduces equipment costs.

[0010]

The above objects of the present invention can be achieved by the following constitutions. That is, a wet fuel supply device that supplies a fuel in which coal is mixed with water to a furnace of a boiler,
In a fluidized bed boiler having an ash cooling device for cooling high temperature ash discharged from a boiler furnace with water, a flow provided with a route for supplying water used for ash cooling in the ash cooling device to a wet fuel supply device A bed boiler or a fluidized bed boiler in which water used for cooling high temperature ash discharged from a boiler furnace is mixed with coal and used as fuel for the boiler furnace.
A pressurized fluidized bed boiler is a typical example of the fluidized bed boiler of the present invention.

[0011]

In the pressurized fluidized bed boiler, the combustion speed of coal is extremely high because it burns coal under high pressure. Therefore, local combustion near the coal supply nozzle causes hot spots and causes clinker trouble.Therefore, by mixing water with coal and sending it to the boiler, it is possible to delay ignition of coal due to water evaporation and prevent local combustion. In many cases, a wet fuel supply system is adopted for the purpose.

Further, this system in which the fuel is made into a paste and pressure-fed is also excellent in that the fuel can be stably supplied into the boiler at a high pressure and with pressure fluctuation. Furthermore, in a normal boiler, the heat of the boiler is removed due to the evaporation of the fuel paste manufacturing water, which causes a reduction in boiler efficiency.However, in a pressurized fluidized bed boiler, a gas turbine is provided on the downstream side of the furnace. In addition, since the steam generated by evaporating the paste water is effectively recovered by the gas turbine as heat energy, the plant efficiency does not drop significantly as in the conventional ordinary boiler. For these reasons, the wet fluid supply system is often adopted in the pressurized fluidized bed boiler plant.

In a pressurized fluidized bed boiler plant employing this wet fuel supply system, paying attention to the fact that water is always required to produce a coal / water paste fuel, and the paste water at room temperature is heated to a high temperature. The above problem is solved by sending the ash cooler and supplying the temperature-increased feed water as it is to the paste manufacturing apparatus and mixing it with coal.

As described above, according to the present invention, the feed water for making coal / water paste, which is the fuel used in the pressurized fluidized bed boiler plant of the wet fuel supply system, is heated through the ash cooler, and thereafter, The heat generated by cooling the ash is effectively used because it is mixed with coal and supplied to the furnace as fuel. That is, the heat consumption amount corresponding to the heat amount recovered from the fuel ash can be reduced, and the plant efficiency can be improved.

Further, in the event that the supply water leaks to the ash side due to wear in the ash cooler, the supply water is supplied to the ash cooler under conditions close to atmospheric pressure, and the supply water is always at a lower pressure than the ash side. Since the system is operating, this feed water will not leak to the ash side, and there will be no shortage of water for making coal / water paste. Also, even if the ash leaks to the water supply side for coal / water paste production, if it is in a small amount, the ash will be mixed with coal and supplied to the furnace, and eventually collected by the dust remover. Therefore, it is not necessary to stop the plant immediately, and the ash cooler can be repaired without any serious problems. In addition, even if the ash cooler cannot be repaired, the plant can be stopped in a safe manner without causing an emergency stop, and it is possible to minimize damage to the plant and improve its reliability and safety. .

[0016]

FIG. 1 shows an embodiment of the present invention. The furnace 1 of the pressurized fluidized bed boiler is housed in a pressure vessel 2. The fuel is supplied to the furnace 1 by a wet method in which it is mixed with water and sent. That is, the coal from the coal bunker 3, the limestone from the limestone bunker 4, and the water from the water storage tank 21 are supplied to the kneading machine 5 at appropriate ratios, and after sufficiently mixing to form a paste, from the fuel supply tank 6. Fuel supply pump 7
Are pressure-fed to the furnace 1. In the furnace 1, the pasty fuel is introduced into the furnace 1 through the fuel supply nozzle 8. On the other hand, the combustion air is sent to the pressure vessel 2 after being compressed by the air compressor 9, and the inside of the pressure vessel 2 is pressurized,
It is supplied into the furnace 1 through the air dispersion plate 10 and used as high-pressure combustion air.

The combustion exhaust gas from the furnace 1 is the cyclone 1 first.
The dust is removed by 1 and then further removed by the filter 12 and sent to the gas turbine 13 as clean gas. The power of the gas turbine 13 is used by the air compressor 9 directly connected to the gas turbine 13 as the power for compressing air. The exhaust gas from the gas turbine 13 is exhausted from the chimney 14B after being recovered by the exhaust heat recovery device 14A.

The recovered heat of the exhaust heat recovery device 14A is used to heat the boiler feed water 15, and the outlet heat recovery water of the exhaust heat recovery device 14A is sent to the furnace 1 where it is absorbed by the furnace heat transfer tube and becomes steam. The steam is sent from the steam pipe 16 to a steam turbine (not shown). Further, the fluid in the furnace 1, the collected ash of the cyclone 11 and the collected ash of the filter 12 are respectively ash extraction pipes 17A, 17B and 17C.
Ash coolers 18A, 18B,
After being cooled at 18C, ash lock hoppers 19A and 1A, respectively
The pressure is reduced to atmospheric pressure by 9B and 19C, and then sent to the ash silo 20.

Since the fuel to be sent to the furnace 1 is required to keep a proper mixing ratio of coal, limestone and water, the supply amount of coal and limestone is constantly monitored, and the kneading machine 5 adjusts the amount of water according to the amount. Need to be supplied to. Meanwhile, the ash cooler 18
Even in A, 18B, and 18C, the outlet temperature is always 150-
An appropriate amount of cooling water is required to maintain the temperature at 200 ° C. The amount of this cooling water is 18A, 18B, 18
The outlet temperature of C is monitored, and the required amount of cooling water is controlled by each ash cooling water valve 23A, 23B, 23C. This ash cooling water is ash cooler 18A,
After being collected at the outlets of 18B and 18C and then sent to the kneading machine 5, when the amount of water is less than the amount of water required for producing the pasty fuel, the paste water valve 24 is opened to secure the required amount of water. On the other hand, when the amount of ash cooling water exceeds the amount required for producing the pasty fuel, the paste water valve 24 is fully closed, the paste water return valve 28 is opened, and the kneading machine 5 is overheated.
Water is not sent to.

In this way, the ash-cooled water is returned to the furnace 1 together with the fuel without being discarded to the outside of the system, so that heat is recovered in the furnace 1. That is, according to the present embodiment, the feed water for producing the pasty fuel, which is the fuel used in the pressurized fluidized bed boiler plant of the wet fuel supply system, is heated through the ash cooler and then mixed with coal to form a furnace. The heat generated by cooling the ash is effectively used because it is supplied as coal / water paste fuel, and the heat energy can be consumed by the amount of heat recovered from the fuel ash, improving plant efficiency.

In the unlikely event that the ash coolers 18A, 18B, 1
Even if the ash cooling water leaks to the ash side inside 8C, the inlet of the kneading machine 5 is at atmospheric pressure, and the ash coolers 18A, 18B,
Since the water pressure in 18C can be kept sufficiently lower than the pressure on the ash side, the ash cooling water does not leak to the ash side and the water for preparing the pasty fuel does not run short. Further, even if the ash leaks to the water supply side for producing the pasty fuel, if the amount is a certain amount, the ash is mixed with coal and supplied to the furnace 1, and finally the dust removing device (the cyclone 11 and the filter 12). ), It is not necessary to stop the plant immediately, and the ash cooler 18A will not be important.
Repair of ~ 18C is possible. Also, the ash cooler 18A-1
Even if the 8C cannot be repaired, the plant can be stopped in a safe manner without an emergency stop and the damage to the plant can be minimized, and the reliability and safety can be improved.

[0022]

According to the present invention, since the ash discharged from the furnace is cooled with water before being mixed with the fuel in the furnace, it is possible to reduce the fuel consumption amount corresponding to the recovered heat amount by cooling the ash. Therefore, the plant efficiency will be improved. Also,
Should ash leak into the ash cooling water due to wear in the ash cooler, the ash cooling water containing this ash will be mixed with the fuel and supplied to the boiler, and finally collected by the dust remover. Therefore, it is not necessary to stop the plant immediately, and it is possible to repair the ash cooler without serious consideration. In addition, even if the ash cooler cannot be repaired, the plant can be stopped in a safe manner without a very emergency stop, and it is possible to minimize damage to the plant, thus reducing the reliability and safety of the plant. To be enhanced.

[Brief description of drawings]

FIG. 1 is a system diagram of a pressurized fluidized bed boiler showing an embodiment of the present invention.

FIG. 2 is a system diagram of a pressurized fluidized bed boiler showing a conventional technique.

FIG. 3 is a system diagram of a pressurized fluidized bed boiler showing a conventional technique.

[Explanation of symbols]

1 ... Furnace, 2 ... Pressure vessel, 3 ... Coal bunker, 4 ... Limestone bunker, 5 ... Kneader, 6 ... Fuel supply tank, 7 ... Fuel supply pump, 8 ... Fuel supply nozzle, 9 ... Air compressor, 10
... Air dispersion plate, 11 ... Cyclone, 12 ... Filter, 1
3 ... Gas turbine, 14A ... Exhaust heat recovery unit, 14B ... Chimney, 15 ... Boiler feed water, 16 ... Steam piping, 17A, B,
C ... Ash extraction pipe, 18A, B, C ... Ash cooler, 19
A, B, C ... Ash lock hopper, 20 ... Ash silo, 21 ...
Water tank, 22 ... Water supply pump, 23A, B, C ... Ash cooling water valve, 24 ... Paste water valve, 25 ... Cooling water cooling tower, 2
6 ... Cooling water pump, 28 ... Paste water return valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akimitsu Matsumoto 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Kure Factory

Claims (2)

[Claims] 1. A fluidized bed boiler having a wet fuel supply device for supplying a fuel in which coal is mixed with water to a furnace of a boiler, and an ash cooling device for cooling high temperature ash discharged from the boiler furnace with water. A fluidized bed boiler, wherein a path for supplying water used for ash cooling in the ash cooling device to a wet fuel supply device is provided. 2. A fluidized bed boiler characterized in that water used for cooling high temperature ash discharged from a boiler furnace is mixed with coal and used as fuel for the boiler furnace.