JPH0222281B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluidized bed boiler, and particularly to a fluidized bed boiler that can control steam temperature well.

BACKGROUND ART Fluidized bed furnaces, which burn fuel in a fluidized bed formed by fluidizing a fluidized medium such as sand, have high combustion efficiency and can burn even flame-retardant materials well, so they have recently been used in various fields. In addition, the amount of heat retained in the fluidized bed is extremely high, and the heat transfer efficiency is 4 to 5 in the empty column.
To achieve this, various fluidized bed boilers have been provided in which heat transfer tubes such as evaporator tubes and superheater tubes are arranged in the bed to effectively recover the heat within the bed. However, in order to achieve good combustion in a fluidized bed, it is necessary to maintain the bed temperature appropriately depending on the type of fuel supplied.
If the temperature drops below a certain level, combustion within the bed will fail and a large amount of unburned matter will scatter into the empty column.On the other hand, if the bed temperature is too high, some of the ash will melt and become fluidized. There are problems such as the product becoming defective. On the other hand, fluidized bed boilers, like other types of boilers, experience load fluctuations depending on the conditions of the equipment that uses steam and hot water, but for the reasons mentioned above, it is difficult to respond to these load fluctuations by changing the bed temperature. be. For this reason, a method has been proposed to adjust the steam temperature by adjusting the bed height and exposing part or all of the superheater tubes outside the bed, but the superheater tubes are arranged parallel to the bed height direction. Therefore, even a slight change in layer height causes a sudden change in the exposed area, making precise control impossible.

An object of the present invention is to eliminate the above-mentioned problems and provide a fluidized bed boiler in which steam temperature can be precisely controlled.

In short, in this invention, the evaporator tube is arranged relatively lower in the fluidized bed, at least a part of the superheater tube is arranged in the upper part of the fluidized bed so as to have a diagonal section, the parallel arrangement section is the main heat recovery section, and the The row section is configured to perform precise control as a temperature control section, and is characterized by being configured to rapidly drop the temperature in conjunction with the parallel section, which is located at a small height, in the event of an emergency stop of the boiler.

Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, a fluidized bed 3 is formed in a fluidized bed boiler main body 1 by fluidizing air (combustion air) A supplied through a blower 4, an air chamber 5, and a perforated plate 2. Reference numeral 6 denotes an evaporation tube disposed in the fluidized bed 3 as an intrabed heat transfer tube, and is bent so as to be substantially parallel to the bed height direction of the fluidized bed 3.

Reference numeral 7 denotes a superheater tube, which is disposed above the evaporator tube 6, and has a parallel portion 7a on the inflow side of the steam S, and a diagonal portion 7 on the outlet side that rises toward the outlet end.
b, and a portion of the oblique portion 7b is exposed from the fluidized bed 3.

If you want to increase the steam temperature during operation of a fluidized bed boiler, increase the bed height _H1 to increase the contact area between the fluidized bed and the superheater tube, and conversely, if you want to decrease the steam temperature, is performed by decreasing the layer height _H1 . In this case, steam temperature control is performed by making a part of the superheater tube 7 run obliquely.
Since H ₂ can be much larger than the height H ₃ of the parallel portion, precise temperature control can be achieved. By the way, if the efficiency in the empty column section is 1, then in the fluidized bed the heat transfer efficiency reaches 4 to 5, and since the heat transfer efficiency of the two is greatly different, precise control can be achieved by controlling the bed height in the diagonal section 7a. It becomes possible.

Next, a specific example of bed height control of the fluidized bed 3 is shown. When it is desired to reduce the bed height H ₁ , the fluidized medium is discharged through the medium discharge pipe 8 and stored in the storage tank 9.
If you want to increase the bed height _H1 , use the airflow transport pipe 10.
This is carried out by transporting the fluid medium in the storage tank 9 with air current.

In the case of emergency shutdown of the fluidized bed boiler due to failure of equipment that uses the steam generated in the boiler, the fluidized medium is discharged, but since the height H ₃ of the parallel section 7a, which is the main heat recovery section, is small. The entire superheater tube 7 can be exposed outside the layer in a short time.

In the above explanation, the heat exchanger tubes with the skewed section were explained as superheater tubes, but in the case of a fluidized bed boiler in which the superheater tube is not arranged as an intrabed heat exchanger tube, the evaporator tubes have the skewed section. It is of course possible to form.

By implementing this invention, the temperature of steam or hot water can be precisely controlled by adjusting the bed height.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a fluidized bed boiler according to the present invention. 1...Fluidized bed boiler main body, 3...Fluidized bed, 7...
...superheater tube, 7a...parallel section, 7b...oblique section.

Claims (1)

[Claims] 1 An evaporator tube and a superheater tube are arranged in a fluidized bed maintained within a predetermined temperature range, and the evaporator tube generates steam, and the superheater tube heats the generated steam to a desired temperature. 1. A fluidized bed boiler, characterized in that the evaporation tube is disposed relatively below the fluidized bed, and at least a part of the superheater is configured to have a diagonal section in the upper part of the fluidized bed.