JPH0419292Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention supplies coal, which is a solid fuel, onto a fluidized bed formed of relatively large particles such as gravel, and also supplies sand as a heat transfer object. A circulating fluidized bed boiler that improves thermal efficiency by circulating fine particles such as
In particular, it relates to the structure of a recycling pipe that allows circulating bed material to flow smoothly.

[Prior art]

As a boiler that can burn solid fuel efficiently while meeting exhaust gas emission standards, it uses a circulating system consisting of fine particles such as ash and limestone on a dense bed (fluidized bed) made of relatively large particles such as gravel. A circulating fluidized bed boiler equipped with bed material has been proposed.

As shown in FIG. 4, this circulating fluidized bed boiler includes a combustor 1 which is a combustor, an external heat exchanger 2 installed adjacent to the combustor 1, and a heat exchanger 2 on the external heat exchanger 2. a cyclone 4 having a fluid supply port connected to the top of the combustor 1 via a connecting duct 3; a recycle pipe 5 connecting the external heat exchanger 2 and the lower part of the combustor 1;
It consists of 6.

The combustor 1 has a lower dense bed area A.
And the freeboard area B of the large diameter part at the top of this
It is composed of In the dense bed area A, a dense bed 8 is formed in which a dense bed material 7 made of gravel or the like is accommodated. Further, this dense bed 8 is filled with coal 9 as a solid fuel and crushed limestone which is supplied for the purpose of capturing sulfur content and becomes part of the circulating bed material.

The coal 9 and limestone are supplied into the dense bed 8 from a fuel supply pipe 10 provided at the upper part of the dense bed area A. In addition, dense bed area A
A fluidizing air system constituted by a supply pipe 12 and the like is provided at the lowest part of the combustor 1, and fluidizing air a for fluidizing the dense bed 8 is supplied into the combustor 1. This fluidized air a is used for combustion, but its main role is to be sent over the entire area of the dense bed 8 by means of a dispersion plate, etc., and to fluidize the dense bed material 7 as a whole.

A combustion air system composed of a supply pipe 13 and the like is provided at a location corresponding to the upper edge portion of the dense bed area A, and the combustion air b is supplied to a flow rate adjusting section 14.
is supplied into the combustor 1 while the supply amount is automatically adjusted.

On the other hand, the freeboard area B forms a circulating bed material 15 in which carbon, ash, or finely divided limestone generated by combustion in the lower stage floats and circulates. Secondary air is supplied to this circulating bed material 15 from a secondary air system 16, thereby achieving more complete combustion. The gas G containing the circulating bed material R made of carbon, ash, finely divided limestone, etc. generated in the dense bed area A and the freeboard area B is supplied to the cyclone 4 via the connecting duct 3, where the gas G is The circulating bed material R is separated, and the gas G is supplied to a convection heat transfer section (not shown) and used as an energy source for steam generation.

On the other hand, the circulating bed material R collected by the cyclone 4 falls under its own weight into the hot recycle 18 of the external heat exchanger 2 from the dipleg 17 provided at the lower part. A fluidizing air supply pipe 19 is provided at the bottom of the external heat exchanger 2 to fluidize the circulating bed material R.

The circulating bed material R supplied into the hot recycling 18 overflows from the upper end of the partition wall 20 and moves into the heat exchange section 22 containing the heat transfer tubes 21 to recover heat and generate steam S. . The circulating bed material R supplied into the external heat exchanger 2 via the cyclone 4 is returned to the dense bed area A of the combustor 1 via the lower recycling pipes 5 and 6, and is The temperature inside A is controlled.

Note that a gas vent pipe 23 is provided at the top of the external heat exchanger 2.
One end is connected, and the other end is connected to a large diameter part forming a freeboard area B of the combustor 1, and configured to return gas in the external heat exchanger 2 to the freeboard area B of the combustor 1. has been done. Now, as described above, such a circulating fluidized bed boiler includes a combustor 1 having a dense bed region A in which the dense bed material 7 is fluidized and a freeboard region B in which the circulating bed material R is circulated, the circulating bed material R and the gas G. a cyclone 4 that separates the hot circulating bed material R, a heat exchange section 22 that accommodates the circulating bed material R discharged from the cyclone 4 and absorbing heat from the circulating bed material R, and a hot recycle 18 that accommodates the hot circulating bed material R. The external heat exchanger 2, which is constructed of
are supplied into the combustor 1 through the recycle pipe 6 so as to adjust the temperature.

[Problems to be solved with the idea]

By the way, in the circulating fluidized bed boiler having the above configuration, the circulating bed material R present in the external heat exchanger 2 is normally connected to the vertical upstream pipe l ₁ as shown in FIG.
and supply ports 25, 26 provided at the bends of the recycling pipes 5, 6, which are composed of horizontal downstream pipes _l2 .
The conveying air c is supplied from the combustor 1, thereby circulating the circulating bed material R into the combustor 1.

If the distance L between the external heat exchanger 2 and the combustor 1 is large in the recycling pipe with this configuration, the circulating bed material R will stay in the middle of this downstream pipe _l2 , and a predetermined amount of the circulating bed material R will be returned to the combustor 1. As a result, the temperature inside the combustor 1 cannot be adjusted and there is a possibility that the combustor 1 will not be able to operate.

Due to the above-mentioned circumstances, a method of arranging a pipe for supplying fluidized air inside this downstream pipe _l2 can be considered, but this method prevents the circulating bed material R from flowing back into the pipe and clogging it. There were problems such as the risk of causing damage.

[Purpose of invention]

The present invention was devised to solve the above-mentioned conventional problems, and its purpose is to:
In a circulating fluidized bed boiler, it is possible to improve the circulation of the circulating bed material from the external heat exchanger into the combustor, thereby enabling efficient and continuous operation of the boiler.

[Summary of the idea]

In order to achieve the above-mentioned object, the present invention includes a combustor having a fluidized bed, a cyclone connected to the combustor and whose lower part communicates with an external heat exchanger, and a recycling pipe connecting the external heat exchanger and the combustor. In a circulating fluidized bed boiler that communicates with the recycling pipe, a first pipe having a plurality of air jet ports at a lower part is disposed in a downstream pipe constituting the recycling pipe, and a second pipe is spaced apart within the first pipe. The circulating fluidized bed boiler is characterized in that an air supply pipe is connected to the base of the second pipe.

The recycle pipe according to the present invention is provided with a fluidizing device for circulating bed material R made of a double pipe inside, and the air introduced into the first pipe from the second pipe is transferred to the air jet of the first pipe. By ejecting from the outlet, the circulating bed material R that has entered the first pipe can be discharged to the outside.

Since the first pipe is in direct contact with the circulating bed material R, it is in a state where it is easy for this to enter from the jet port, but air is jetted from the first pipe into the second pipe,
Since it is ejected from the first pipe into the recycling pipe, the circulating bed material R is actively discharged from the first pipe. Furthermore, if a large amount of circulating bed material R enters the first pipe, it can be discharged by opening the end of the first pipe.

〔Example〕

An embodiment of the structure of a recycle pipe in a circulating fluidized bed boiler according to the present invention will be described below with reference to FIGS. 1 to 3.

Figure 1 is an explanatory diagram of the main parts of a circulating fluidized bed boiler, in which an external heat exchanger 2 and a combustor 1 are connected to an upstream tube.
They are communicated by recycle pipes 5 and 6, which are composed of _l1 and downstream pipe _l2 . A first pipe 25 and a second pipe 26 are arranged in a double structure in the downstream pipe _l2 constituting the recycling pipes 5 and 6.

More specifically, as shown in FIGS. 2 and 3, the first tube 25 has both ends closed by closing plates 27 to form a chamber, and has one or more rows of air jets at the bottom. An outlet 28 is provided and is disposed by a support 29 so as to have a distance d from the downstream pipe l ₂ , and its base is closed by a valve (not shown).

As an example of the air outlet 28 is shown in FIG. 3, the second pipe 26 has an opening 31 at its tip and is closed at its base by a closing plate 32. An air supply pipe 34 connected to an air supply source (not shown) is attached to the base thereof.

In the above configuration, when the circulating bed material R in the external heat exchanger 2 descends inside the upstream pipes _l1 of the recycle pipes 5 and 6 due to its own weight, the conveying air c supplied from the air supply port 35 moves the circulating bed material R into the combustor 1. At this time, the air is supplied from the air supply pipe into the second pipe 26, and the fluidized air e ejected from the jet port 28 provided in the first pipe 25 causes circulation in the downstream pipe _l2 . Since the bed material R is always fluidized,
It is possible to convey the circulating bed material R to the combustor ₁ side with a small amount of conveyed air c, and without accumulating the circulating bed material R in the downstream pipe l2.

While conveying the circulating bed material R in this way,
It is fluidized by the air flow and a part of it flows into the air outlet 2.
Even if air flows into the first pipe 25 from the air outlet 8, it does not enter the second pipe 26, so the air outlet 28 provided in the first pipe 25 is not closed.

In the unlikely event that a large amount of circulating bed material R is inside the first pipe 25,
If the air enters the pipe, the pipe connected to the first pipe 25 is opened and air e is supplied from the air supply pipe 34, and this air e flows through the opening 31 at the tip of the second pipe 26.
The circulating bed material R is supplied into the first pipe 25 from the above, fluidizes the circulating bed material R staying in the first pipe 25, and is discharged from the first pipe 25.

[Effect of idea]

As is clear from the above description, according to the circulating fluidized bed boiler having the recycle pipe structure according to the present invention, the first air outlet 28 is provided in the downstream pipe _l2 constituting the recycle pipes 5 and 6. A second tube 26 having an opening at its distal end is spaced apart from the first tube 25 and a second tube 26 is disposed at a distance from the first tube 25 to the first tube 25 . Air is supplied from the jet port 28 provided in the pipe 25 to fluidize the circulating bed material R present in the downstream pipe _l2 .

Therefore, the circulating bed material R in the downstream pipe _l2 constituting the recycling pipes 5 and 6 can be constantly fluidized, and there is no fear of closing the air outlet 28 of the first pipe 25. This has the effect that the amount of air can be kept to the minimum necessary, and as a result, the boiler can be operated efficiently and continuously for a long period of time.

[Brief explanation of drawings]

Figures 1 to 3 show an embodiment of the recycle pipe in a circulating fluidized bed boiler according to the present invention, in which Figure 1 is an explanatory diagram of the main parts of the fluidized bed boiler, and Figure 2 is an enlarged view of the main parts. , Figure 3 is A of Figure 2.
- It is a partially cutaway view of the A arrow. FIG. 4 is an explanatory diagram of the circulation boiler, and FIG. 5 is an explanatory diagram of the main parts of FIG. 4. 1... Combustor, 2... External heat exchanger, 4...
...Cyclone, 5, 6...Recycle pipe, 7
...Dense bed material, 8...Dense bed, 9...
... Coal, 10 ... Fuel supply pipe, 15 ... Free board, 16 ... Secondary air system, 18 ... Hot recycling, 19 ... Fluid air supply pipe, 20 ... Partition wall, 21 ... Heat exchanger tube, 22 ...Heat exchange section, 23...
... Gas vent pipe, 25 ... First pipe, 26 ... Second pipe, 27, 32 ... Closing plate, 28 ... Air outlet, 29, 33 ... Support, 34 ... Air supply pipe, 31 ...Opening, 35...Air supply port, l ₁ ...
Upstream pipe, l ₂ ...downstream pipe.

Claims (1)

[Claims for Utility Model Registration] A combustor having a fluidized bed, a cyclone connected to the combustor and whose lower part communicates with an external heat exchanger, and a circulation system in which the external heat exchanger and the combustor are connected through a recycling pipe. In the type fluidized bed boiler, a first pipe having a large number of air jet ports is arranged at the lower part of the downstream pipe constituting the recycling pipe, and a second pipe is arranged at intervals within the first pipe. . A circulating fluidized bed boiler, characterized in that an air supply pipe is connected to the second pipe.