JPH01111110A - Dispersion plate nozzle for fluidized-bed type combustion apparatus - Google Patents

Abstract

PURPOSE:To prevent a fluidized medium from counterflowing out of the nozzle hole of a dispersion plate nozzle by divergently forming the nozzle hole through which air for fluidization is fed. CONSTITUTION:A nozzle hole 10 through which air for fluidization is fed is formed divergently, and the inside (feeding side) of the nozzle hole 10 has an area smaller than that of the outside thereof. As a dispersion plate nozzle 4 shown in the drawing, it has the nozzle hole 10 formed into a divergent trumpet-shape. When a pressure difference between the fore and after portions of the dispersion plate nozzle 4 becomes small or even in the case that a pressure is provided one-sidedly from the outside of the dispersion plate nozzle 4 without the feed of the air for fluidization from the inside thereof, a fluidized medium 3 within a fluidized bed acts as a locked material with the wedge effect produced by the trumpet-shaped dispersion plate nozzle 4. More particularly, the fluidized medium 3 flown reversely into the nozzle hole 10 from the outside thereof produces a contracted flow even if the flow rate of the fluidized medium 3 increases toward the inside of the nozzle hole 10, which area is small. Consequently, the passing area of the fluidized medium is further reduced by the contracted flow, and the gradual increase of the flow rate from the outside toward the inside causes the pressure to be lowered and a turbulent flow and the like to be generated, so that the fluidized medium 3 clogs at the tapered part of the nozzle hole 10 and is prevented from falling down into an air box 9.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a fluidized bed combustion apparatus, and in particular to a fluidized bed combustion apparatus suitable for reducing the fall of a fluidized medium from a nozzle hole for supplying fluidizing air. This invention relates to a dispersion plate nozzle for a device.

[Conventional technology]

Fluidized bed combustion equipment has advantages such as a wide range of applications for fuel, in-furnace desulfurization, and high in-bed heat transfer performance, and is suitably used as coal-fired boilers and the like.

As shown in FIG. 2, the conventional apparatus is equipped with a fluidized bed that uses limestone as the fluidized medium 3 and contains desulfurizing agent particles. A mixture of lime and limestone supplied from a crushed coal bunker and a limestone bunker (not shown) is placed in a fluidized bed at a concentration of 800 to
It is burned at 820°C, and the combustion energy heats the boiler to generate steam of the required quality. However, in the fluidized bed combustion apparatus, no consideration was given to the fact that the fluidized medium 3 in the fluidized bed flows backward through the nozzle hole 11 of the conventional dispersion plate nozzle 8 and falls into the wind box 9. Note that the nozzle hole 11 of the conventional dispersion plate nozzle 8
The hole diameter of is 4nwn, and the average particle diameter of the fluidizing medium 3 is 1~
2III+, it easily passes through the nozzle hole 11. In particular, in the startup cell where the startup hot blast furnace 7 is installed, the amount of air during startup using the startup light oil burner and the amount of air during normal flow after extinguishing the burner are significantly different, so during normal flow, conventional dispersion is used. Inside the nozzle hole 11 of the plate nozzle 8 (supply side)
The differential pressure between the inside and the outside becomes small, and when the fluidized bed is started and stopped, the conveying air in the coal feed pipe 5 flows before the fluidizing air and then stops, so the conveying air flows through the conventional dispersion plate nozzle 8. A problem has arisen in which the pressurized fluid medium 3 flows backward from the nozzle hole 11 and falls into the wind box 9, and the wind box 9 becomes full, making it impossible to continue operation. This is an important problem that must be solved before the size of fluidized bed combustion equipment is increased, and it is one of the problems that is urgently needed to be solved.

U.S. Patent No. 3,552,033 and Japanese Patent Application No. 1217-1989
The publication discloses a nozzle hole with a non-circular cross section in multiple stages provided radially or circumferentially from the center of the nozzle, a nozzle hole with a circular cross section, or a nozzle hole into which a short pipe is inserted.
All nozzle holes have the same opening area on the inside and outside, and are expected to have the above-mentioned problems.

[Problem that the invention seeks to solve]

The conventional technology did not take into account the issue of preventing the backflow of the fluidic medium from the nozzle hole of the dispersion plate nozzle, and there was a problem that the fluidic medium would accumulate in the wind box, making it impossible to continue operation. .

An object of the present invention is to provide a distribution plate nozzle for a fluidized bed combustion apparatus that prevents backflow of a fluidized medium from a nozzle hole of the distribution plate nozzle.

[Means for solving problems]

In order to achieve the above object, the present invention includes a dispersion plate nozzle in which the nozzle hole for supplying flowing air is formed to widen toward the end.

[Effect]

According to the present invention, the dispersion plate nozzle hole for supplying fluidizing air to the fluidized bed is widened toward the end, and the inner side has a smaller area than the outside. When the fluidizing air flowing from the nozzle hole disappears and pressure is applied from the outside, the fluidized medium inside the fluidized bed flows backward from the outside of the nozzle hole, but the flow velocity increases in the small area inside the nozzle hole, resulting in a contracted flow. As the passing area becomes narrower, the flow velocity gradually increases inward, or the pressure decreases, creating turbulent flow, and the so-called wedge effect (material lock of the fluid medium) causes the fluid to flow back through the nozzle hole. It will not fall into the wind box.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1a to 2.

As shown in FIG. 2, a wind box 9 is surrounded by a furnace wall 2 and partitioned by a water pipe 6 with a membrane that forms the bottom of the furnace.
A hot blast stove 7 for startup is connected to this wind box 9. A coal feeding pipe 5 is provided for supplying one fuel into a fluidized bed in which a fluidized medium 3 flows and performs combustion through a plurality of water pipes 6 with membranes and a partition plate connecting them, and a coal feeding pipe 5 that supplies one fuel to the fluidized bed where the fluidized medium 3 flows and performs combustion, and the other fluidizing air. The dispersion plate nozzle 4 is configured such that the supply nozzle hole 10 is widened toward the end and the inner side (supply side) has a smaller area than the outer side.

The flow of fluidizing air is supplied under pressure by a forced draft fan (not shown), heated by an air preheater midway through, and is injected from the wind box 9 into the fluidized bed through the nozzle hole 10 of the distribution plate nozzle 4 to form a fluidized medium. It works to make 3 fluid.

The starting hot air stove 7 pumps the fluidized medium 3 at 500 to 600 ml at the time of starting up.
It is a furnace for heating to ℃.

In the above configuration, in the conventional dispersion plate nozzle 8 shown in FIG. 3, the nozzle hole diameter is 4 mm and the average particle diameter of the fluid medium 3 is 1 to 2 mm. During normal flow other than that, the differential pressure between the inside and outside of the distribution plate nozzle becomes small. In addition, when starting and stopping the fluidized bed, in order to prevent the fluidized medium 3 from flowing back into the coal feed pipe 5, the conveying air in the coal feed pipe 5 flows before the fluidizing air and then stops, so that the conveying air is dispersed. There was a problem that the fluidizing medium 3 would fall and accumulate in the wind box 9 due to conditions such as the plate nozzle 4 being pressurized, making it impossible to continue operation. , the shape of the nozzle hole 10 is changed to a trumpet shape with an inclination of 30 to 35'' and widens at the end. Even when pressure is applied from the outside, the fluidized medium 3 in the fluidized bed acts to materially lock in the trumpet-shaped dispersion plate nozzle 4 due to the wedge effect. The flow velocity of the medium 3 increases on the inside where the area is small, resulting in contracted flow, and as a result, the area through which the layer passes becomes narrower, and the flow velocity gradually increases from the outside to the inside, causing pressure to drop and turbulence to occur. This prevents the fluid medium 3 from getting stuck in the narrowed portion and falling into the wind box 9.

Further, as shown in FIG. 1b, the nozzle holes 10 of the dispersion plate nozzle 4 are arranged in two stages on the circumference, and a plurality of nozzle holes 10 are arranged alternately in each row.

As another embodiment of the present invention, as shown in FIG. 1c, the nozzle hole 10 has a shape that combines a small-diameter cylindrical shape on the inside and a trumpet shape on the outside, similar to the nozzle hole shape in FIG. 1a. This provides the effect of preventing backflow of the fluid medium.

〔Effect of the invention〕

According to the present invention, the nozzle hole of the dispersion plate nozzle for supplying fluidizing air has a shape that widens toward the end and has a smaller area on the inside than the outside, so that the fluidized medium in the fluidized bed can be easily flowed into the wind box under all operating conditions. Backflow fall can be prevented,
Since the accumulation of the fluidized medium in the wind box can also be prevented, there is no interruption in operation and long-term stable operation of the fluidized bed combustion apparatus is possible.

[Brief explanation of the drawing]

FIG. 1a is a sectional view of a dispersion plate nozzle showing one embodiment of the present invention, FIG. 1b is a perspective view of FIG. 1a, and FIG. 1C is a partial sectional view showing another embodiment of the present invention. The figure is a cross-sectional view of a fluidized bed combustion apparatus, and FIG. 3 is a cross-sectional view of a dividing plate nozzle showing the prior art. 3... Fluid medium, 4... Dispersion plate nozzle, 10...
nozzle hole.

Claims (1)

[Claims] A dispersion plate nozzle for a fluidized bed combustion apparatus, characterized in that a nozzle hole for supplying fluidizing air is formed to widen toward the end.