JPS6071802A - Fluidized-bed boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a fluidized bed boiler 2 that facilitates adjustment of fluidized bed temperature.
Regarding.

In general, in a fluidized bed boiler, the heat transfer tubes embedded in the fluidized bed vary depending on the type of fuel, the particle size distribution of the fluidized medium forming the fluidized bed, the type of fluidized medium such as sand, limestone, and alumina particles, and operating conditions. While the thermal properties change and the temperature within the fluidized bed changes, it is necessary to maintain the temperature within the fluidized bed within a certain range consisting of the following points.

In other words, if the temperature in the fluidized bed is too high, the amount of unburned matter, carbon monoxide, and hydrocarbons generated will decrease, improving combustion efficiency and improving boiler efficiency, but on the other hand, nitrogen oxides will increase. Increase rapidly.

Conversely, if the temperature in the fluidized bed is too low, combustibility deteriorates, the desulfurization rate further decreases, and the amount of sulfur dioxide discharged increases.

In this way, the temperature within the fluidized bed must be kept within a certain range from both combustibility and pollution levels. It is determined by the relationship between the heat absorption amount of the fuel and the amount of fuel injected into the fluidized bed.

Setting the temperature of the fluidized bed is largely influenced by the amount of heat absorbed by the heating medium, but regarding the issue of the amount of heat absorbed by the heating medium, the particle size distribution and type of the fluidized medium, the flow state of the fluidized medium, and the fuel There are many uncertain factors in heat transfer engineering that are still unresolved, such as the type of This is the current situation.

Therefore, to adjust the heat absorption amount of the heat medium, first bury the heat transfer tubes in the fluidized bed so that they have a large heat transfer surface, and then cut the heat transfer tubes while operating the fluidized bed boiler to adjust the heat transfer amount of the heat transfer medium. The line to be adjusted is shown.

However, when the heat exchanger tube is cut, the following problems arise. For example, assuming that 7θ heat transfer tubes are buried in a fluidized bed and j of them are uncut, the flow rate of the heat medium will be doubled downstream of the cut heat transfer tubes, and the flow resistance (pressure loss) also doubles, and the film coefficient inside the pipe also increases in proportion to the flow velocity t75n.

Thus, changes in flow velocity, pressure drop, and film coefficient are
For example, an increase in pressure loss may cause insufficient pump capacity or affect the pressure and temperature of the generated steam, causing the entire fluidized bed boiler to become unbalanced.

In addition, if two or three of the 70 heat transfer tubes are cut, or if they are partially cut, the flow velocity, pressure loss, and film coefficient within each tube array buried in the fluidized bed may not be uniform. (In addition to this, uncertainties in heat transfer engineering are added, and the reality is that it is virtually impossible to adjust the temperature in the fluidized bed.) Also, based on this fact, it is difficult to adjust the temperature in the fluidized bed. However, there are technical problems in terms of combustion efficiency and pollution.

On the other hand, as shown in Figure 7i, there are the following problems in terms of the form of heat transfer within the fluidized bed. In the figure, a large number of heat exchanger tubes are horizontally installed in a staggered arrangement inside the fluidized bed. In the figure, 2i indicated by a broken line indicates the removed heat exchanger tube.

Air for fluidization and combustion is supplied into the fluidized bed through the air distribution plate 3. This air rises in the layer while forming bubbles, and in the process collides with the heat exchanger tubes and breaks them, becoming small bubbles that activate contact with the fuel and promote combustion. The air bubbles generated in the part where the heat transfer tube was removed do not collide with the heat transfer tube, so large bubbles 4ta
It grows and rises rapidly within the layer. As a result, the combustibility in this area deteriorates, the temperature inside the layer decreases in that area, and the temperature inside the layer cannot be made uniform, which not only makes it impossible to satisfy both flammability and pollution problems. Furthermore, there is a technical problem in that the heat transfer tubes are worn out by the fluidized medium that is accompanied by the rapid rise of bubbles.

As an improvement to this, a Dan tube was installed in the removed part of the heat transfer tube to prevent the growth of bubbles, but the flow rate, pressure loss, and film coefficient of the heat medium flowing inside the heat transfer tube were
The above-mentioned problems remain unsolved, and the overall fluidized bed boiler remains unbalanced, it is virtually impossible to control the temperature within the fluidized bed, and the combustion efficiency and pollution are unsatisfactory.

The present invention aims to solve the above-mentioned conventional technical problems, and to provide a fluidized bed boiler that enables a single temperature range in the fluidized bed and solves the problems of combustion efficiency and pollution at the same time.

In other words, the present invention suppresses the contact between the fluid medium and the heat transfer tubes without cutting out the heat transfer tubes, maintains the flow of the heat medium in the heat transfer tubes, and adjusts the amount of heat absorption. It is characterized in that a large number of heat exchanger tubes are arranged in a layer, a coating material is provided to cover the heat exchanger tubes, and the surface of the heat exchanger tubes is partially coated with this coating material.

Hereinafter, one embodiment of the present invention will be described in detail. The covering material 6 shown in the diagram is, for example, a cylindrical heat insulating tube or a heat transfer tube! The pipes are made from large-diameter steel pipes and cut into cylindrical shapes of fixed dimensions. Additionally, six slits are provided in this covering material B to facilitate attachment and detachment.

The covering material shown in FIG. 3 is made of a pair of steel plates t machined to a certain size, which are covered with bolts so as to sandwich the heat transfer tubes j therebetween.

The heat exchanger tube j is coated with this coating material as shown in Figure 1'g. The method of coating is to first cover the bend part /3 of the heat exchanger tube j where wear is most severe, and then coat the heat exchanger tube j located in the upper layer of the fluidized bed where there is a high possibility of bubble growth.

Also, the entire surface of the heat exchanger tube, for example, a fluidized bed/! In order to uniformly cover the entire surface of the heat exchanger tube j located in the upper layer of
Covering materials formed to a certain size are attached at certain intervals.

The operation of this embodiment configured as above will be explained next. In the example shown in Figure 7, one heat transfer tube j is bent three times to form a meandering tube, and these meandering tubes are arranged in three rows. In the three rows of meandering heat transfer tubes j, a heat medium of an amount fc corresponding to the evaporation area of the fluidized bed boiler is uniformly distributed and flowing.

The heat retained in the fluid medium is the heat transfer tube! Heat exchanger tubes due to contact with a fluid medium! Heat is transferred to the heat transfer tube! The heat transferred to is transferred to the heat medium flowing inside the heat transfer tube j.

In this heat transfer process, the heat transfer between the fluid medium and the heat transfer tube O is not constant depending on the type of fluid medium or the flow state, and there are many uncertain factors, so the actual situation is not clear.

On the other hand, heat transfer tubes! The heat transfer between the heat carrier and the heat carrier is determined by the flow rate of the heat carrier. Therefore, by keeping the flow rate of the heat medium constant and adjusting the amount of heat transfer between the heat transfer tube and the fluidized medium, the amount of heat absorbed by the heat medium is adjusted.

The above heat exchanger tube! Adjustment of the amount of heat transfer between the fluid medium and the heat transfer tube! Attach the coating material 6 to the surface of the heat exchanger tube! This is done by suppressing direct contact between the fluid and the fluid medium.

That is, a constant flow of heat medium is passed through the heat transfer tube j,
Covering material ≦ formed into a certain size is coated, and fluidized bed/! The area covered by the covering material B is increased or decreased so that the temperature within is within a certain range.

In this way, the fluidized bed/! The amount of heat absorbed by the heat medium is easily determined so that the temperature within the range is within the range.

As described in detail above, according to the fluidized bed boiler of the present invention, the flow rate of the heat medium flowing in the heat transfer tubes is kept constant, and only the amount of heat transfer between the heat transfer tubes and the fluidized medium is adjusted. Therefore, the amount of heat absorbed by the heat medium can be easily adjusted, and the temperature within the fluidized bed can be easily adjusted.

In addition, since the flow rate of the heat medium is constant, the pressure loss inside the heat transfer tubes does not change, there is no effect on incidental equipment such as pumps, there is no effect on steam pressure, and the overall balance of the fluidized bed boiler is maintained. It is maintained.

In this way, the temperature inside the fluidized bed can be reliably and easily controlled, which has excellent effects such as solving flammability and pollution problems at the same time, and maintaining the specified performance of the fluidized bed boiler. has.

[BRIEF DESCRIPTION OF THE DRAWINGS] Figure 17 is an explanatory diagram showing the form of heat transfer in the fluidized bed, the top diagram to 7y are an example of the present invention, and the top diagram is a perspective view of a cylindrical covering material. The figure is a perspective view of a covering material made of two plates, and the figure 7y is a perspective view showing a state in which a heat exchanger tube is covered with a covering material. /... Fluidized bed Jj... Heat exchanger tube 16... Covering material, ?
,,,steel plate as cladding material.

Claims (1)

[Claims] A large number of heat exchanger tubes are arranged in a fluidized bed, a coating material is provided to cover the heat exchanger tubes to suppress the amount of heat absorption, and the surface of the heat exchanger tubes is partially coated with this coating material. Fluidized bed boiler.