JPS5981408A - Fluidized-bed type boiler - Google Patents

Abstract

PURPOSE:To increase the combustion efficiency of a fluidized-bed furnace by a method wherein the density of heat transfer pipes on the furnace wall at a vacant column part, through which a gas containing unburnt matter flows, is reduced in order to completely burn an unburnt gas passing through the vacant column part. CONSTITUTION:A part of heat transfer pipes constituting a furnace wall at a vacant column part 7 are thinned out so that the density of heat transfer pipes is made less dense here than that at a fluidized-bed part and the uppermost part of the vacant column part. The length of the zone of the furnace wall, over which the heat transfer pipes are thinned out, is preferably made enough long for unburnt matters passing through the vacant column part to completely burn. A part of heat transfer pipes 8 may be arranged so as to bypassing the furnace wall instead of to thin-out the heat transfer pipes 8 constituting the furnace wall. The partial removal of the heat transfer pipes 8 constituting the furnace wall at a part just above a fluidized bed results the reduction of the heat quantity transferred at the vacant column part, resulting in raising the temperature at the vacant column part and consequently enabling to completely burn the unburnt matters (CO and the like) passing through the vacant column part.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluidized bed boiler, and more particularly to a coal-fired fluidized bed boiler in which unburned matter is reduced as much as possible.

As shown in FIG. 1, a conventional fluidized bed boiler includes a fluidized bed 2 formed on a dispersion plate 1 in the furnace, an intrabed heat exchanger tube 3 provided in the fluidized bed 2, and a a fuel supply pipe 4 for supplying fuel; a wind box 5 provided directly below the distribution plate 1;
An air supply pipe 6 for supplying fluidizing air to the wind box 5, an empty tower section forming a space above the fluidized bed 2, and a furnace wall heat transfer tube 8 provided on the furnace wall of the empty tower section. It mainly consists of

In a fluidized bed boiler with such a configuration, a desulfurizing agent (such as limestone) is present in the fluidized bed to perform in-furnace desulfurization, and in order to burn coal at a relatively low temperature to suppress NOx, Coal is not sufficiently combusted in the fluidized bed, and gas containing unburned components such as carbon oxide (CO) and soot is discharged from the empty column to the outside of the furnace, creating the need for secondary treatment, and There is a problem in that the combustion efficiency of the furnace is reduced.

Conventionally, in order to deal with such problems, a buckle plate was placed in the empty tower section, and unburned components (mainly unburned carbon) were collided with each other for complete combustion. Attempts have been made to completely combust the unburned matter by increasing the residence time in the empty column, but these methods have the drawbacks of increasing the pressure loss in the empty column and complicating the equipment. there were.

An object of the present invention is to provide a fluidized bed boiler that eliminates the drawbacks of the above-mentioned prior art, reduces unburned content in the empty column by simple means, and increases the combustion efficiency of the fluidized bed furnace.

The present invention burns coal and gas containing unburned matter in the fluidized bed section and the empty tower section above the fluidized bed section, reduces the number of heat transfer tubes in the fluidized bed and on the wall of the tower section, and burns the unburned gas that passes through the empty tower section. The feature is that the gas is completely combusted.

The present invention will be explained in detail below with reference to the drawings.

FIG. 2 is a sectional view of a furnace portion of a fluidized bed boiler showing an embodiment of the present invention. In the figure, this device is composed of parts that are referred to by the reference numerals shown in FIG.
A part of the heat exchanger tubes forming the furnace wall of the empty tower section 7 is thinned out,
The number of heat exchanger tubes is smaller than the number of heat exchanger tubes at the top of the fluidized bed section and the sky column section. It is desirable that the length of the furnace wall where the heat transfer tubes are thinned out is a sufficient length for the unburned matter passing through the empty column to be completely combusted. Instead of thinning out the heat exchanger tubes constituting the furnace wall, some of the heat exchanger tubes may be arranged so as to detour from the furnace wall.

According to the above embodiment, by partially removing the heat transfer tubes that constitute the furnace wall directly above the fluidized bed, it is possible to reduce the amount of heat transferred in the cavity and increase the temperature. Unburned components (such as CO) passing through the column can be completely combusted. Therefore, it becomes possible to improve the combustion efficiency of the entire fluidized bed furnace.

In the present invention, instead of thinning out the heat transfer tubes on the furnace wall of the empty tower section directly above the fluidized bed, a heat-blocking mask may be applied to a portion of the tubes. For this mask, for example, a fire-resistant block material may be used, and the front surface of any heat exchanger tube may be covered with the block material.

As described above, according to the present invention, by reducing the amount of heat transferred through the heat transfer tubes that constitute the furnace wall directly above the fluidized bed, the temperature of the empty tower portion is increased, and unburned components such as CO are completely combusted. Therefore, the combustion efficiency of the entire furnace can be increased.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of the furnace portion of a fluidized bed boiler showing a conventional fluidized bed boiler and an embodiment of the present invention. l... Dispersion plate, 2... Fluidized bed, 3...
・-・Intralayer heat transfer tube, 6...Air supply tube, tsu...
... Sky tower section, 8... Sky tower section heat exchanger tube. Agent Patent Attorney Takenaga Kawakita Figure 1 Figure 2

Claims (1)

[Claims] (1) Burn coal and gas containing unburned matter in the fluidized bed and the empty tower above it, reduce the number of heat transfer tubes in the fluidized bed and on the furnace wall, and burn the unburned gas that passes through the empty tower. A fluidized bed boiler characterized by complete combustion.