JPH041245B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention supplies coal, which is a solid fuel, onto a fluidized bed formed of relatively large particles, and further circulates fine particles such as sand as a heat transfer object. The present invention relates to a method for supplying dense bed material to a circulating fluidized bed boiler that improves heat exchange efficiency.

[Prior art]

A boiler that can burn solid fuel efficiently while meeting exhaust gas emission standards.A circulation system in which a circulating layer of fine particles of ash and limestone is placed above a fluidized bed (dense bed) made of relatively large particles. A type fluidized bed boiler has been proposed.

This circulating fluidized bed boiler consists of a combustor 1, which is a combustor, as shown in FIG.
an external heat exchanger 2 provided adjacent to the combustor 1; a cyclone 4 having a fluid supply port connected to the top of the combustor 1 via a connecting duct 3 on the external heat exchanger 2; It is composed of a hot recycle pipe 5 and a cold recycle pipe 6 that communicate the external heat exchanger 2 with the lower part of the combustor 1.

Combustor 1 has a fluidized bed area A and a circulation area B.
A dense bed 8 containing a dense bed material 7 made of relatively large particles is formed in the fluidized bed region A. This dense bed 8 is supplied with coal 9 as a solid fuel for the purpose of capturing sulfur content, and is filled with crushed limestone and the like which will become part of the circulating bed material.

Coal 9 is supplied into the dense bed 8 from a fuel supply pipe 10 provided in the upper part of the fluidized bed area A, and limestone is supplied into the dense bed 8 from a supply pipe 11 (supply port) provided in the lower part of the fluidized bed area A.
supplied within. Further, a fluidizing air system constituted by a supply pipe 12 and the like is provided at the lowest part of the fluidized bed region A, and fluidizing air a for fluidizing the dense bed 8 is supplied into the combustor 1. This fluidizing air a is used as fuel, 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 the upper edge of the fluidized bed region A, and the combustion air b is supplied to the combustor 1 while the supply amount is automatically adjusted by the flow rate adjustment section 14. supplied within.

On the other hand, the circulation area B forms a circulation layer 15 in which, in addition to fine solid particles such as sand, a circulation bed material R made of carbon, ash, or finely divided limestone generated by combustion in the lower stage is suspended. Secondary air is supplied into the circulation layer 15 from the secondary air system 16 to achieve more complete combustion.

The gas G containing the circulating bed material R is supplied to the cyclone 4 via the connecting duct 3, where the gas G
The circulating bed material R is separated, and the gas G is supplied to a boiler (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 well 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 well 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, recovers heat, and generates steam S. In addition, in the heat exchange section 22, the excess ash contained in the circulating bed material R floats to the upper layer of the fluidized circulating bed material R, and the heat exchange section 22
It is discharged to the outside through a discharge pipe 23 provided at the upper part of the pipe.

The circulating bed material R in the hot well 18 is sent to the hot recycle pipe 5, and the circulating bed material R whose temperature has been lowered by heat exchange in the heat exchange section 22 is sent to the fluidized bed area A of the combustor 1 through the cold recycle pipe 6. Reflux. Note that one end of a gas vent pipe 24 is connected to the top of the external heat exchanger 2, and the other end is connected to a large diameter portion forming the circulation layer region B of the combustor 1.

By the way, in the circulating fluidized bed boiler having the above structure, the dense bed material 7 in the combustor 1 is fluidized in the fluidized bed region A by the gas ejected from the lower part, but at this time, they move violently and collide with each other, causing them to crack. or wear. In order to form a predetermined fluidized bed region A, dense bed material 7 of a predetermined particle size is required, but the desired particle size decreases due to cracking or abrasion, and as a result, the dense bed material 7 that is insufficient during operation must be replenished. There is a need to.

By the way, this dense bed material 7 is considered to be made of a spherical body such as an alumina ball, for example, in order to keep the concentration of the dense bed constant and to reduce the degree of cracking and wear. There is a problem in guiding the liquid to the supply pipe 11 at the bottom of the combustor 1.

That is, the circulation type fluidized bed boiler with the above structure is large-sized, and the overall structure is like a 10-story building, and the height H of the supply pipe 11 is from the ground as shown in Fig. 3. It can reach up to 5m.

Therefore, if the spherical dense bed material 7 is to be conveyed to such a height by the belt conveyor 26, the inclination angle θ must be set to 0°, so theoretically the length L is infinite. It becomes large,
It cannot be transported by conveyor belt.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to facilitate the introduction of dense bed material into the combustor of a circulating fluidized bed boiler, Another point is to reduce costs by downsizing the belt conveyor.

[Summary of the invention]

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 cyclone that communicates the external heat exchanger with the combustor. In the circulating fluidized bed boiler,
A belt conveyor is arranged between the supply port at the bottom of the combustor and the dense bed material pasting area, the dense bed material is mixed into powder and granules to form a mixture, and this mixture is conveyed to the supply port by the belt conveyor. It is.

FIG. 4 shows the principle of the present invention.
As shown in the figure, when a spherical body such as an alumina ball 29 is simply placed on the belt conveyor 26 and conveyed in the direction of the arrow, it is theoretically difficult to convey it because it rolls and falls by itself.

However, as shown in Figure B, the powder 28 and the spherical body 29
In the mixed state, this powder 28 becomes a bed material for the spherical body 29 and stabilizes the spherical body 29. As long as the powder 28 does not fall off,
The spherical bodies 29 can be transported by a belt conveyor 26. The present invention utilizes this principle.

In the present invention, the granular material is finer than the particle size of the dense bed material, is a stabilizing material that holds the dense bed material, and is preferably fine particles such as sand, and these fine particles are used as the circulating bed material. In some cases, it can be fed into the combustor along with dense bed material.

However, if the fine particles are not a circulating bed material, only the dense bed material may be separated from the mixture near the supply port and supplied. Further, even if the fine particles are circulating bed material, if the amount thereof is greater than the amount supplied to the combustor, the excess amount can be separated and then supplied.

Normally, the replenishment amount of dense bed material is a fraction of the replenishment amount of circulating bed material, and the amount of circulating bed material will not become excessive.

〔Example〕

An embodiment of the method for supplying dense bed material to a circulating fluidized bed boiler according to the present invention will be described below.

In FIG. 1, reference numeral 27 denotes a mixture stored in a storage area of dense bed material, and this mixture 27 is composed of powder 28 and, for example, alumina balls 29.

Specifically, the granular material 28 is sand of 1 mm or less,
Preferably, it is used as the circulating bed material R supplied into the combustor 1.

The alumina balls 29 serving as the dense bed material 7 are, for example, about 5 to 25 mm.

In addition, this powder and granular material 28 and alumina balls 29
are mixed in a 1:1 ratio. Such a mixture 27 has an angle of repose θ' of about 25°, and therefore the inclination angle θ of the belt conveyor 26 may be slightly smaller than this angle of repose θ'.

Then, this mixture 27 is transferred to a belt conveyor 26.
Supply pipe 1 provided at the bottom of combustor 1 by
1, but here, if necessary, sieve 30
The alumina balls 29 are separated, and only the alumina balls 29 are supplied as the dense bed material 7 from the supply pipe 11 into the combustor 1.

Of course, limestone, sand, etc. are supplied from the supply pipe 11 as needed, so these limestone, sand, etc. may be supplied simultaneously with the alumina balls 29 depending on the operating state of the fluidized bed boiler.

〔Effect of the invention〕

As is clear from the above explanation, according to the method for supplying dense bed material to a circulating fluidized bed boiler according to the present invention, spherical dense bed material such as alumina balls is mixed into powder and granules to form a mixture 27. is conveyed to the supply pipe 11 by the belt conveyor 26, and is supplied from this supply pipe 11 into the combustor 1.

Therefore, even if the dense bed material is spherical, the powder particles can serve as a holding material for the dense bed material and support it on the surface of the belt conveyor 26, and the angle of inclination of the belt conveyor 26 can be set relatively large. be able to.

As a result, it is possible to reduce the size of the belt conveyor, which not only reduces manufacturing costs and operating costs, but also reduces the installation space.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a method for supplying dense bed material to a circulating fluidized bed boiler according to the present invention, FIG. 2 is an explanatory diagram of a circulating fluidized bed boiler, and FIG. 3 is an explanatory diagram of a method for supplying dense bed material to a circulating fluidized bed boiler. FIG. 4 is an explanatory diagram of the case where spherical bodies are transported by a belt conveyor.
The figure shows the case of simply transporting spherical bodies, and the figure B shows the case of transporting a mixture of powder and spherical bodies according to the present invention. 1... Combustor, 2... External heat exchanger, 3...
...Connection duct, 4...Cyclone, 5...Hotwell, 6...Cold recycling, 7...Dense bed material, 8...Dense bed, 9...Coal,
10... Fuel supply pipe, 11, 12, 13... Supply pipe, 14... Flow rate adjustment section, 15... Recirculation bed, 1
6... Secondary air system, 17... Day preg, 18...
...hot recycling, 19...fluidizing air supply pipe,
20... Partition wall, 21... Heat exchanger tube, 22... Heat exchange section, 23... Discharge pipe, 24... Gas vent pipe, 26...
... Belt conveyor, 27 ... Mixture, 28 ... Powder, 29 ... Alumina ball, 30 ... Sieve.

Claims (1)

[Scope of Claims] 1. A combustor having a fluidized bed, a cyclone communicating with the combustor and having a lower portion communicating with an external heat exchanger, and a circulating fluid system that communicates the external heat exchanger with the combustor. In the bed boiler, the dense bed material forming the fluidized bed and the powder particles of the dense bed material are mixed and mixed to form a mixture, and the mixture is conveyed to the supply port at the bottom of the combustor by a belt conveyor. A dense bed material supply method characterized by the following.