JPH02178501A - Fluidized-bed boiler - Google Patents

Abstract

PURPOSE:To reduce a pressure loss of a divided steam tube group and easily perform round-off of boiler minimum load by blocking steam allowed to flow through the divided steam tube group with the lowering of a load. CONSTITUTION:After fuel and air flows are throttled to some extent because combustibility is lowered when the temperature of a fluidized bed 3 lowers too much at the time of cell slapping, an air amount adjustment damper 11a is wholly closed to stop the flow of a right-half of the fluidized bed 3 and combustibility is not lowered at fluidized bed side temperature by supplying the same quantity as a fuel layer supplied to both combined fluidized bed 3 to a right-side fluidized bed 3 alone. The pressure loss of steam between an inlet and an outlet of a divided steam tube group 4b is at least necessary minimum pressure loss because the same quantity as a steam quantity allowed to flow in both the divided steam tube groups 4a, 4b is allowed to flow through the divided steam tube group 4b alone by closing a steam shut-off valve 38 at the side of the divided steam tube group 4a positioned at the side which stops the right-half of the fluidized bed 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fluidized bed combustion apparatus, and particularly to a fluidized bed boiler suitable for reducing the minimum load of the fluidized bed boiler.

[Conventional technology]

The temperature in the bed of a fluidized bed boiler that uses heavy oil, coal, etc. as fuel is usually 800 to 900'C, and heat transfer tubes,
In a fluidized bed boiler with buried steam pipes, the amount of heat transfer (heat transfer coefficient) in the layer of the heat transfer tubes and steam pipes is about 5 to 10 times larger than the amount of heat transferred from only the gas flow in a conventional boiler.
It has the characteristic of providing a large amount of heat transfer.

Furthermore, since fluidized bed boilers have excellent heat transfer characteristics in the bed, even low-grade coal such as sludge coal, which was conventionally dumped into piles, can be effectively used as fuel for fluidized bed boilers. In recent years, fluidized bed boilers have been attracting attention because they can reduce the volume of low-grade coal by incinerating it.

The outline of the fluidized bed boiler will be explained below using FIG. 10 and FIG. 11.

FIG. 10 is a longitudinal cross-sectional view of a conventional fluidized bed boiler, and FIG. 11 is a cross-sectional view taken along the horizontal line ``--■'' in FIG.

A perforated plate 2 is arranged at the bottom of the fluidized bed boiler 1, and a fluid N3 is formed on the perforated plate 2 by a fluid medium introduced from a medium input pipe (not shown). This flow 1! I
3 includes divided steam pipe groups 4a and 4b.

A heat transfer tube 5 is arranged, and a convection heat transfer section 6 on this flow WJa
A steam pipe 7 and an economizer pipe 8 are respectively arranged for the purpose of waste heat recovery.

9 is a partition wall, the air chambers 10a and 10b are divided by the partition wall 9, and an air HJ is provided at the entrance of the air chambers 10a and 10b.
I-regular dampers lla, 1)b are arranged.

Fluidization and combustion air flows from the air duct 12, air amount adjustment dampers lla and llb, and air chambers 10a and 10b.
3.

On the other hand, the fuel burned in the flow rIJS and the powdered fluid medium are transferred to the flow vJ layer 3 through the divided steam pipe groups 4a, 4b and the heat transfer tubes 5.
The heat is recovered by the steam pipe 7 of the convection heat transfer section 6 and the economizer pipe 8, and reaches the flue 13 as exhaust gas.

In such a structure, the flow of feed water during rated load operation of the fluidized bed boiler 1 will be explained with reference to FIGS. 10 and 11.

Water supplied from a boiler circulation pump (not shown) is supplied from the main water supply pipe 14 to the economizer inlet header 15 to the economizer pipe 8, where it is preheated and then supplied from the economizer outlet header 16 and the connecting pipe 17 to the drum 18. Ru.

Water separated into steam and water in one day is supplied to the heat exchanger tube 5 from the connecting pipe I9 to the heat exchanger tube inlet via the ladder 20, heated in the fluidized bed 3, and sent to the drum 18 via the heat exchanger tube outlet header 21 and the connecting pipe 22. Supplied.

The steam separated in the drum 18 is supplied to the steam pipe 7 through the communication pipe 23 and the steam pipe inlet header 24, where it is superheated by the exhaust gas from the convection heat transfer section 6, passes through the steam pipe outlet header 25 and the communication pipe 26, and is then supplied to the inlet header 27. is supplied to the divided steam pipe group 4a, superheated by the combustion heat of the fluidized bed 3 in the divided steam pipe group 4a, and is supplied to the outlet header 28, the connecting pipe 29, and the superheater spray 3.
0, flows to the connecting pipe 31 and the population header 32, is superheated again in the divided steam pipe group 4b, and flows to the outlet from the ladder 33 to the main steam pipe 34.
supplied to

In addition, 35 is a spray adjustment valve.

As described above, in the conventional fluidized bed boiler 1, the entire amount of steam heated in the steam pipe 7 flows in series to the divided steam pipe groups 4a and 4b, which is not preferable in a case where cell slumbing control is performed.

That is, the air chamber 10a shown in FIGS. 10 and 11,
10b, the supply of combustion air and fuel to one air chamber 10a is stopped and the flow rate is reduced to half J! ! During low load operation in so-called cell slumping control, in which load control is performed in step 3, pressure loss increases and steam drift occurs.

FIG. 12 is a characteristic curve diagram in which the vertical axis shows the pressure loss of steam and the horizontal axis shows the evaporation amount, and the curve 4 mA shows the pressure loss in the conventional fluidized bed boiler 1.

In the conventional flow v3 Jii boiler 1, in order to prevent local overheating due to drift of steam in the divided steam pipe groups 4a and 4b during low load operation, a sufficient steam flow rate must be ensured during minimum load operation. Therefore, the song becomes as shown in song &iA in Fig. 12.

Therefore, when the required minimum load is low, the required minimum pressure loss (point B) is required with a small steam flow rate as shown by curve A in Figure 12, so the steam pressure loss is 0 at the maximum load. It grows larger when scratched as shown by the dots.

That is, as the minimum load operating condition becomes lower, the pressure loss during rated load operation increases as shown by curve klA, and therefore the design pressure of the boiler pressure-resistant parts including the drum 18 and the water supply piping must be increased.

[Problem to be solved by the invention]

As described above, the conventional fluidized bed boiler has the drawback that the steam pressure loss is large and the minimum load cannot be reduced.

The present invention aims to eliminate such conventional drawbacks,
The purpose is to provide a fluidized bed boiler that can reduce pressure loss in a group of divided steam pipes and easily reduce the minimum boiler load.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a divided steam pipe group inlet header and a divided steam pipe group outlet header downstream of the inlet header and upstream of the outlet header. The divided steam pipe group inlet header is connected to the inlet connecting pipe which serves as a steam cutoff valve.
The outlet header and the divided steam pipe group outlet header are connected by outlet connecting pipes.

[Effect]

By cutting off the steam flowing through the divided steam pipe groups as the load (evaporation amount) decreases, the flow rate of steam in the divided f-trachea group, that is, the pressure loss, is always kept above the required minimum pressure loss, so that the lowest load can be achieved. You can round up.

〔Example〕

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

FIG. 1 is a longitudinal sectional view of a fluidized bed boiler according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line II-II in FIG.
), (b) is a characteristic curve diagram in which the vertical axis shows steam pressure loss and fluidized bed temperature, and the horizontal axis shows boiler load.
The figure is a longitudinal sectional view explaining the operating method of the fluidized bed boiler shown in Fig. 1, and Figs. 5 and 6 are longitudinal sectional views showing other embodiments.
7(a) and 7(b) are characteristic curve diagrams of the fluidized bed boiler shown in FIGS. 5 and 6, and FIGS. 8 and 9 are longitudinal sections showing other embodiments. Top view and TX-TXv
It is a cross-sectional view of A.

In Figures 1, 2, and 4, numbers 1 to 28
．． 30, 34, and 35 are the same as the conventional one.

35a and 35b are divided steam pipe group inlet headers provided downstream of the inlet header 27, 37a and 37b are inlet connecting pipes that connect the inlet header 27 and the divided steam pipe group inlet headers 36a and 36b, and 38a and 38b are inlet connecting pipes. Steam cutoff valves 37a and 37b, 39a and 39b are divided steam pipe group outlet headers provided upstream of the outlet header 28, and 40a and 40b are outlet communication pipes that connect the divided 1 trachea group outlet headers 39a and 39b with the outlet header 28. It is.

The fluidized bed boiler shown in FIGS. 1, 2 and 4 differs from the conventional fluidized bed boiler shown in FIGS. 10 and 11 in the divided steam pipe group 4a.

On the population side of 4b, divided steam pipe group inlet headers 36 a, 36 b are provided downstream of the inlet header 27, and this inlet header 27 and the divided steam pipe group inlet headers 36 a, 36
b is an artificial connecting pipe 3 having steam cutoff valves 38a, 3 [1b
This is the point mentioned in 7a and 37b.

On the other hand, on the outlet side of the divided steam pipe groups 4a, 4b, there are also divided steam pipe group outlet headers 39a, 3 upstream of the outlet header 28.
9b, and these divided steam pipe group outlet headers 39a, 39
b and the outlet header 28 are connected by outlet communication pipes 4Qa and 40b.

As for the operating method of the fluidized bed boiler l, first of all, Fig. 1 and Fig. 2.
As shown in the figure, during boiler rated operation, air amount adjustment dampers lla, llb and steam cutoff valves 38a, 38b
The entire fluidized bed 3 is operated between both devices, and the temperature of the fluidized bed 3 during rated operation is at point D in Fig. 3(b),
The pressure loss at this time is at 8 points in FIG. 3(a).

Therefore, when the load control of the fluidized bed boiler 1 is performed by cell slumping control as described above, the amount of fuel supplied to the right half of the fluidized bed 3 is reduced and the air-fuel ratio is adjusted as shown in FIG. Air volume adjustment damper lla to keep it constant
The temperature of the flow rB3 is lowered from the point shown in FIG. 3(b) to the point F to reduce the amount of heat absorbed in the divided steam pipe group 4a. (
At this time, the steam pressure loss also decreases from point E to point G in FIG. 3(a). ) That is, the heat absorption amount of the divided steam pipe groups 4a and 4b -
Based on the formula: heat transfer area If too much, the combustibility will deteriorate, so after reducing the amount of fuel and air to a certain extent, the air 1iPl adjustment damper 11a is fully closed to stop the flow of the right half of the flow N3 shown by the diagonal line in FIG. By supplying the same amount of fuel that had been supplied to both fluidized beds 3 up to now only to the flow rrI3 on the left side of Fig. 4, the temperature of the bed on the flowing side will decrease as shown in Fig. 3(b). returns from point F to point H again, and there is no reduction in combustibility.In addition, the steam cutoff valve on the side of the divided steam pipe group 4a located on the side where the right half of the fluidized bed 3 in FIG. 4 is stopped. 38a
By closing both divided steam pipe groups 4a
, 4b flows through only one of the divided steam pipe groups 4b, so the pressure loss of the steam at the entrance and exit of the divided steam pipe group 4b is Diagram (a)
The pressure drop rises from point G to point I, and the pressure drop never drops below the required minimum pressure drop.Furthermore, the installation location of the divided steam pipe group 4a that shuts off the steam is as shown in Figure 4, where the fluidized bed 3 in the right half of the figure is Since the flow is stopped, no heat transfer takes place, so the divided steam pipe group 4a will not overheat.

5 and 6 show other embodiments, FIG. 5 is a longitudinal cross-sectional view of a fluidized bed boiler, and FIG. 6 is a Vl-V shown in FIG. 5.
There is a sectional view taken along the I line.

The difference from the embodiments shown in FIGS. 1, 2, and 4 is that the air chambers 10a, 10b, 1
The steam pipe groups 4a, 4b, 4c are divided into 6 parts, ie, 0c, 10d, 10e, and 10f, and the divided steam pipe groups 4a, 4b, and 4c are divided into 3 parts, and the inlet header 27 and the divided steam pipe group inlet headers 36a, 36b, and 36c are connected to the steam cutoff valve 38a.

Inlet communication pipes 37a, 37b, 3 with 38b, 38C
7c, the outlet header 28 and the divided steam pipe group outlet headers 39a, 39b, 39c are connected to the outlet connecting pipe 40a,
40B and 40C, and the other explanations are the same and will therefore be omitted here.

In the embodiment shown in FIGS. 5 and 6, the air chamber is divided into three parts, ie, air chambers 10a, 10b, and 10c. ,
less than those in Figures 2 and 4, and J! ! I Flammability and NOX associated with temperature fluctuations.

Fluctuations in environmental values such as Sox can be suppressed, and the number of divisions of the divided steam pipe group can be reduced to the divided steam pipe group 4a.

4b and 4c, the maximum pressure loss of superheated steam can be reduced as shown by the curve in FIG. 7(a). Furthermore, in this case, since the air chamber is divided into six, the divided steam pipe group can also be divided into six at most, thereby making it possible to further reduce the bed temperature fluctuation range of the fluidized bed 3 and the pressure loss of steam.

FIGS. 8 and 9 show another embodiment, in which an existing fluidized bed boiler is modified.

Figure 8 is a vertical cross-sectional view of a fluidized bed boiler, and Figure 9 is the
- IX line transversal diagram sectional view.

In Figures 8 and 9, 41 is an existing steel frame;
Other symbols indicate the same symbols as in other embodiments.

When modifying an existing fluidized bed boiler 1 as shown in the embodiment of the present invention, on the inlet side of the divided steam pipe groups 4a and 4b, the existing inlet header is connected to the inlet of the divided steam pipe group by a ladder 36a.
, 36b, and as shown in FIG. 9, an inlet header 27 is newly installed between the connecting pipe 26 and the divided steam pipe group inlet headers 35a and 36b, and the population header 27 and the divided steam pipe group inlet header 36a, Newly installed steam cutoff valve 38 between 35b
They are connected by inlet communication pipes 37a and 37b having pipes a and 38b.

On the other hand, on the outlet side of the divided steam pipe groups 4a and 4b, the existing outlet headers are replaced with the divided steam pipe group outlet headers 39a and 39b.
By installing new outlet connecting pipes 40a, 40b and outlet header 28 between the divided steam pipe group outlet headers 39a, 39b as shown in Fig. 9, even an existing fluidized bed boiler can be easily installed. Through modification work, it is possible to transform the boiler into a fluidized bed boiler with less fluctuation in bed temperature of fluidized N3 and less steam pressure loss, and most of the existing steel frame 41 and fluidized bed boiler 1 can be used, so the period and cost of modification work are shortened. I'm done.

〔Effect of the invention〕

According to the present invention, it is possible to reduce the minimum load without increasing pressure loss, that is, without increasing the drum pressure during rated operation. Therefore, since the design pressure of the boiler pressure-resistant section is reduced, the thickness of each component material can be made thinner, and a fluidized bed boiler that is excellent in terms of economy can be obtained.

[Brief explanation of the drawing]

FIGS. 1 to 9 relate to embodiments of the present invention, and FIGS.
The figure is a vertical cross-sectional view of a fluidized bed boiler, and Figure 2 is the ff of Figure 1.
-U 4% cross-sectional view, Figures 3 (a) and (b) are characteristic curve diagrams with the vertical axis showing steam pressure loss and fluidized bed temperature, and the horizontal axis showing boiler load, Figure 4 is FIG. 1 is a longitudinal sectional view explaining the operating method of the fluidized bed boiler, FIGS. 5 and 6 are longitudinal sectional views and vr-VlyL sectional views showing other embodiments, and FIGS. 7(a) and (b ) are characteristic curve diagrams of the fluidized bed boiler shown in Figures 5 and 6, Figures 8 and 9 are longitudinal cross-sectional views and cross-sectional views taken along line IX-IX showing other embodiments, and Figure 10 is the conventional one. FIG. 11 is a cross-sectional view along x+-)1g of FIG. 10, and FIG. 12 is a characteristic curve diagram of a conventional fluidized bed boiler. 2...Perforated plate, 3...Fluidized bed, 4a, 4b. 4C・・・・・・Divided steam pipe group, 9・・・・・・
...Partition wall, 10a, 10b, 10c, 10d, lO
e, 10f...Air chamber, 27.32...
...Inlet header, 28°33...Outlet header, 36a, 36b, 36c...
Split steam pipe group inlet header, 37a, 37b. 37c...... Entrance connecting pipe, 38a, 38b
, 38C... Steam cutoff valve, 39a, 39
b, 39c...Divided steam outlet header, 40a,
40b, 40C...Exit connecting pipe. Figure 10 ('/,) Figure 10

Claims (1)

[Claims] A perforated plate is placed between the fluidized bed and the air chamber, and the air chamber is partitioned by a partition wall to divide the cells, and a group of divided steam pipes are connected to the inlet header and the outlet header along the cell dividing direction. A divided steam tube group inlet header and a divided steam tube group outlet header are provided downstream of the inlet header and upstream of the outlet header, and the inlet header and the divided steam tube group inlet header are steam-blocked. 1. A fluidized bed boiler characterized in that an outlet header and a divided steam tube group outlet header are connected to each other by an inlet connecting pipe having a valve, respectively.