JPH0419290Y2 - - 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. This invention relates to the structure of an L valve in a circulating fluidized bed boiler that improves thermal efficiency by circulating fine particles such as.

[Prior art]

As a boiler that can burn solid fuel efficiently while meeting exhaust gas emission standards, a circulating layer of fine particles of ash and limestone is placed on top of a fluidized bed (dense bed) made of relatively large particles such as gravel. A circulating fluidized bed boiler has been proposed.

As shown in FIG. 2, this circulating fluidized bed boiler includes a tower-shaped combustor 1 which is a combustor, an external heat exchanger 2 installed adjacent to this combustor 1,
On this external heat exchanger 2, the combustor 1
The cyclone 4 has a fluid supply port connected to the top of the combustor 1 via a connecting duct 3, and L valves 5 and 6 (supply pipes) connect the external heat exchanger 2 and the lower part of the combustor 1.

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 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 a part of the recirculation bed material. The coal 9 is supplied into the dense bed 8 from a fuel supply pipe 10 provided at the upper part of the dense bed area A, and the limestone is supplied into the dense bed 8 from a supply pipe 11 provided at the lower part of the dense bed area A.

Further, a fluidizing air system constituted by a supply pipe 12 and the like is provided at the lowest part of the dense bed area A, 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. Note that this fluidizing air a is supplied so that the dense bed 8 always maintains a constant fluidized state regardless of the increase in combustion load. A combustion air system composed of a supply pipe 13 and the like is provided at a location corresponding to the upper edge of the dense bed area A, and the amount of combustion air b supplied is automatically adjusted by a flow rate adjustment section 14. It is supplied into the combustor 1 while being controlled.

On the other hand, the freeboard area B forms a freeboard 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 freeboard 15 from a secondary air system 16 to achieve more complete combustion. The gas G containing particles R made of carbon, ash, finely divided limestone, etc. generated in the dense bed area A and the recirculation freeboard area B is passed through the connecting duct 3 to the cyclone 4.
Here, gas G and particles R are separated, and gas G is supplied to a circulation boiler (not shown) and used as an energy source for steam generation.

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

The particles R supplied into the hot recycle 18 overflow from the upper end of the partition wall 20 and move into the heat exchange section 22 containing the heat transfer tubes 21 to recover heat and generate steam S. Note that in the heat exchange section 22, the ash contained in the particles R floats to the upper layer of the fluidized particles R, and the ash contained in the particles R floats to the upper layer of the fluidized particles R,
It is discharged to the outside through a discharge pipe 23 provided at the upper part of 2. The particles R supplied into the external heat exchanger 2 via the cyclone 4 are returned to the dense bed area A of the combustor 1 via the lower L valves 5 and 6, and are It is now possible to control the temperature of

Note that one end of the gas vent pipe 24 is connected to the top of the external heat exchanger 2, and the other end is connected to the large diameter part forming the freeboard area B of the combustor 1.
It is configured to return the gas in the external heat exchanger 2 into the freeboard area B of the combustor 1.

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, a freeboard region B in which the particles R are circulated, and a cyclone that separates the particles R from the gas. 4. A heat exchange section 2 that accommodates the particles R discharged from the cyclone 4 and absorbs heat from the particles R.
2 and hot recycling 1 that accommodates hot particles R.
The heat of the hot particles R is recovered by the L valve 5 (which is a type of connecting pipe and serves to return the particles R to the combustor 1). The particles R are supplied into the combustor 1 by the L valves 6 so as to adjust the temperature thereof.

Therefore, even low-quality, hard-to-combustible fuels such as imported coal or fluid coke can be efficiently combusted, and low _NOx combustion is possible, which has recently put them into practical use.

[Problems to be solved with the idea]

By the way, in the circulating fluidized bed boiler having the above structure, particles R present in the external heat exchanger 2
Usually, as shown in FIG. 3, the L valve 5 is configured in an L shape with a vertical upstream pipe _l1 and a horizontal downstream pipe _l2 .
Conveying air c is supplied from supply ports 25 and 26 provided at the bent portions of the combustor 6, thereby causing the particles R to flow back into the combustor 1.

If the distance L between the external heat exchanger 2 and the combustor 1 is large in the L valve with such a configuration, the particles R will stay in the middle of this downstream pipe _l2 , and a predetermined amount of particles R will be refluxed into the combustor 1. I can't do it,
As a result, there is a possibility that the temperature inside the combustor 1 cannot be adjusted and operation becomes impossible.

In order to eliminate the above-mentioned drawbacks, it is possible to make the L valve an inclined pipe as shown by the dotted line in FIG. It is not possible to control the amount of reflux, which poses a practical problem.

[Purpose of invention]

The present invention was devised to solve the conventional problems as described above, and its purpose is to improve the reflux of particles from the external heat exchanger into the combustor in a circulating fluidized bed boiler. This makes it possible to operate the boiler efficiently and continuously.

[Summary of the idea]

In order to achieve the above-mentioned object, the present invention includes a combustor having a dense bed, a cyclone connected to the combustor and whose lower part communicates with an external heat exchanger, and an L-type cyclone that connects the external heat exchanger and the combustor.
In a circulating fluidized bed boiler connected by valves,
The horizontal pipe constituting the L-valve is configured to have an inclined part in the center thereof which is inclined downward from the external heat exchanger side toward the combustor side.

〔Example〕

An embodiment of the structure of the L valve in the circulating fluidized bed boiler according to the present invention will be described below with reference to FIG.

FIG. 1 is an enlarged view of the main parts of a circulating fluidized bed boiler, and in this figure, the same reference numerals as in FIGS. 2 and 3 indicate the same names.

The L valves 5 and 6 that communicate the external heat exchanger 2 and the combustor ₁ are connected to a vertical upstream pipe L1 and a horizontal downstream pipe that has an inclined part halfway from the external heat exchanger 2 side to the combustor 1 side and slopes downward. It is composed of _two tubes. Specifically, this horizontal downstream pipe l ₂ has horizontal parts l _2-1 and l _2-2 at both ends, and an inclined part in the center.
l _2-3 is formed.

The length of this horizontal part l _2-1 is from 1D (diameter) to 2D, preferably from 2D to 5D, and l _2-2 is less than or equal to 10D, preferably
The angle of inclination θ of the inclined portion _l2-3 is preferably selected from a range of 2 degrees or more, preferably from 10 to 20 degrees.

According to the L valves 5 and 6 configured as described above, the particles R present at the lower part of the upstream pipe _l1 are transferred to the supply port 2.
The conveying air c from 5 and 26 passes through the horizontal part l _2-1 of the downstream pipe l ₂ and reaches the inclined part l _2-3 , where its own weight and the conveying air c reach the horizontal part l _2-2 , and from there It is refluxed into the combustor 1.

[Effect of idea]

As is clear from the above explanation, the L valve structure in the circulating fluidized bed boiler according to the present invention is
A feature of this valve is that an inclined part is provided in the center of the horizontal downstream pipe constituting the valve, which slopes downward from the external heat exchanger side toward the combustor side.

Since we have formed an inclined part in a part of the horizontal downstream pipe, the flow of the particles R in this part is good, and only the minimum necessary amount of conveying air is required, and there is no possibility that the particles R will stay. This has the effect of enabling efficient and continuous operation of the boiler.

[Brief explanation of the drawing]

Fig. 1 is an enlarged view of the main part showing an example of the structure of the L valve in the circulating fluidized bed boiler according to the present invention, Fig. 2 is an explanatory diagram of the circulation boiler, and Fig. 3 is an enlarged view of the main part. . 1... Combustor, 2... External heat exchanger, 3...
...Connection duct, 4...Cyclone, 5, 6...L
Valve, 7... Dense bed material, 8... Dense bed, 9... Coal, 10... Fuel supply pipe, 11,
12, 13... Supply pipe, 14... Flow rate adjustment section, 1
5...Free board, 16...Secondary air system, 17
...Dipreg, 18...Hot Recycle, 1
9... Fluid air supply pipe, 20... Partition wall, 21...
Heat exchanger tube, 22... Heat exchange section, 23... Discharge pipe, 2
4... Gas vent pipe, 25, 26... Supply port, l ₁ ...
Upstream pipe, _l2 ...Downstream pipe, _l2-1 , _l2-2 ...Horizontal part,
l _2-3 ...Slope section.

Claims (1)

[Claims for Utility Model Registration] A combustor having a dense bed, a cyclone communicating with the combustor and having a lower portion communicating with an external heat exchanger, and a circulation system in which the external heat exchanger and the combustor are communicated with each other through an L valve. A circulating type fluidized bed boiler, characterized in that the downstream pipe constituting the L valve is configured to have an inclined part in its intermediate part that slopes downward from the external heat exchanger side toward the combustor side. Structure of L valve in fluidized bed boiler.