JPH025961B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluidized bed boiler, and more particularly to a fluidized bed boiler that allows good circulation of feed water.

Sand or small-diameter burnt lumps are used as a fluid medium, and this fluid medium is mixed with fuel (which may also be incinerated materials such as industrial waste.Hereinafter, the term fuel is used to include this incinerated material). Fluidized bed furnaces have recently attracted a lot of attention because they can use a variety of fuels and can burn even flame-retardant substances such as ash collected in exhaust gas called EP ash. Fluidized bed boilers, in which intrabed heat exchanger tubes such as evaporator tubes and superheater tubes are disposed within the fluidized bed to recover heat within the bed, are also becoming widely used.

However, in conventional fluidized beds, the main focus is on the combustion of the incinerated material, and the heat recovery within the bed is mostly considered as a secondary consideration, so little attention has been paid to heat recovery efficiency. Ta.

An object of the present invention is to provide a fluidized bed furnace that eliminates the above-mentioned problems and can more efficiently recover heat from the fluidized bed.

In short, this invention places the boiler drum at a height that allows for natural circulation of feed water, and if necessary, provides a certain inclination to the heat exchanger tubes in the layer to allow good circulation and flow of feed water. It is.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a fluidized bed furnace, in which an evaporator tube 3 and a superheater tube 4 are arranged as intrabed heat transfer tubes in a fluidized bed 2 formed in the furnace. 5 is a boiler drum, and the height H of the water surface of this boiler drum 5 with respect to the inlet header 3a of the evaporator tube 3 is set to be a height sufficient for natural circulation of water supply. A downcomer pipe 6 is disposed between the boiler drum 5 and the inlet header 3a, and a circulation pump 7 is disposed in the downcomer pipe 6 to assist in circulating feed water. Reference numeral 8 denotes a bypass line that bypasses the circulation pump 7, and this bypass line is provided with a control valve 9 that is set to be fully open when the circulation pump 7 fails.
Next, the evaporator tube outlet header 3b and the boiler drum 5 are connected to the riser tube 10, and the feed water is configured to circulate and flow through the evaporator tube 3 and the boiler drum 5.

On the other hand, the superheater tube 4 is connected to the drum 5 through a steam pipe 11, and is configured to discharge superheated steam to the outside of the system via a superheated steam pipe 12.

In the above boiler apparatus, the heat of the fluidized bed 2 is effectively recovered as a steam/water mixture and superheated steam. In this case, if the circulation pump 7 fails, the control valve 9 is immediately fully opened and the supplied water passes through the bypass pipe 8, so the circulation of the supplied water does not stop.
Further, since the drum 5 is located at a height that allows natural circulation of the water supply, even if the circulation pump 7 breaks down, there is almost no problem with the circulation of the water supply.

FIG. 2 shows a second embodiment of the present invention, which is constructed to allow better fluid flow within the heat transfer tube.

The intrabed heat transfer tube (the one shown is an evaporation tube) 30 arranged in the fluidized bed 2 is at a constant angle α with respect to the horizontal line 13.
It is constructed so that it is tilted with . In other words, it is configured to rise at an angle α toward the flow direction of the fluid within the heat exchanger tube 30. This heat exchanger tube 30
The heat exchanger tubes 31 connected in series with the heat exchanger tubes 31 are also inclined at substantially the same angle. If this inclination angle α is too small, the fluid flow will be slow, and if it is too large for the reaction, the heat transfer tube will come out of the layer. Therefore, the value of α is about 2 degrees to 15 degrees, preferably about 5 degrees to 10 degrees. Between degrees is good. By arranging the heat exchanger tubes 30 and 31 in this manner, the fluid inside always flows in the upward direction, resulting in good fluid flow. In this case, if the heights of the inlet headers 32, 34 and outlet headers 33, 35 of each heat exchanger tube 30 and 31 are h, and the distance between the outlet header 33 of the heat exchanger tube 30 and the inlet header 34 of the heat exchanger tube 31 is e, then The fluid will rise by about 2h+e from the time it flows in from the inlet header 32 of the heat exchanger tube 30 until it flows out from the outlet header 35 of the heat exchanger tube 31.

3 to 5 show a third embodiment.

In this embodiment, by arranging the heat exchanger tubes in parallel, the height of the heat exchanger tubes as a whole is reduced, making it possible to use the tubes even in a fluidized bed with a low bed height. In the case of the illustrated arrangement, the height from the lowest inlet header 32 to the highest outlet header 35 is 1 1/2 as shown in the figure.
h+e′. Here, e' indicates the height from the horizontal line 13', which is the axis of symmetry of the heat exchanger tube 30a, to the inlet header 34 of the heat exchanger tube 31a.

FIG. 4 is a schematic diagram showing the arrangement of heat exchanger tubes 31a and 30a, and FIG. 5 is a plan view of FIG. 3. As is clear from FIG. 5, the heat exchanger tubes 30a and 31a are arranged alternately. Therefore, the heat exchanger tube 31a located at the top is lowered,
If headers 34 and 32 are placed at the same height, e' will be -
1/2h, and the height of the heat exchanger tube 30a and 31a
It is also possible to have a height of about h.

By carrying out this invention, it is possible to circulate and flow the feed water effectively, and it is possible to effectively recover the heat of the fluidized bed.

[Brief explanation of drawings]

Figure 1 is a system diagram of a fluidized bed boiler according to the present invention, Figures 2 and 3 are cross-sectional views of the fluidized bed showing the arrangement of heat exchanger tubes, Figure 4 is a schematic diagram showing the arrangement of heat exchanger tubes, and Figure 4 is a schematic diagram showing the arrangement of heat exchanger tubes. FIG. 5 is a plan view of FIG. 3. 3... Evaporation pipe, 5... Boiler drum, 6... Downcomer pipe, 7... Circulation pump, 8... Bypass pipe line,
9... Control valve, 13, 13'... Horizontal line, 30,
31, 30a, 31a...intralayer heat exchanger tubes.

Claims (1)

[Scope of Claims] 1. The boiler drum is located at a height that allows natural circulation of water supply to the evaporator pipe inlet header, and a down pipe is provided with a pipe line that bypasses the circulation pump, and the bypass pipe line is provided with a pipe line that bypasses the circulation pump. A fluidized bed boiler characterized by being equipped with a control valve that is sometimes fully open. 2. A patent claim characterized in that the intrabed heat exchanger tube located in the fluidized bed is bent so as to have a certain inclination angle with respect to the horizontal line so that it rises in the direction of passage of the fluid passing through the inside. A fluidized bed boiler according to scope 1. 3. The fluidized bed boiler according to claim 1 or 2, wherein the angle of the heat exchanger tubes with respect to the horizontal line is between about 2 degrees and 15 degrees. 4. The fluidized bed boiler according to claim 2 or 3, wherein the heat exchanger tubes are arranged in series with respect to the feed water flow. 5. Claim 2 or 3, characterized in that the heat transfer tubes are arranged in parallel for the water supply flow.
Fluidized bed boiler as described in section.