Fluid sprinkling – spraying – and diffusing – Processes – Including mixing or combining with air – gas or steam
Patent
1994-03-17
1996-04-30
Merritt, Karen B.
Fluid sprinkling, spraying, and diffusing
Processes
Including mixing or combining with air, gas or steam
239424, 2394345, F23C 1102, F23K 500, B01J 400, F27B 1508
Patent
active
055117252
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to method and nozzle for supplying paste fuel to a fluidized bed.
More particularly, the invention relates to a method in comminuting paste fuel which is supplied from a nozzle to a fluidized bed, wherein the fuel in the nozzle is being pressed against an end surface tapering towards the nozzle outlet, and is distributed by means of a jet of splitting air ejected from the nozzle centrally of the fuel flow upstream of the nozzle outlet. EP-A-0182545 discloses a slurry atomizer operating in this way.
In order to secure a satisfactory combustion in furnaces with fluidized bed the paste fuel is dispersed in this way in the combustion chamber as coarse droplets. This dispersion is achieved by means of the jet of splitting air which is called the primary splitting air jet and is directed towards a ceramic cone which forms said tapering end surface. The primary splitting air jet is supplemented by a secondary splitting air jet which is supplied from an annular slot around the nozzle outlet. Experience has shown that there may arise problems by the annular slot being partly clogged, which causes a non-uniformly distributed flow of secondary splitting air and trickle of fuel caused thereby as well as erosion of that part of the nozzle which defines the annular slot, due to generation of vortexes in front of the nozzle. Furthermore, the cooling of the ceramic cone will be unsatisfactory or uneven, which contributes to formation of thermal tension in the ceramic cone and cracks, caused by such tension. If the ceramic cone is replaced by a cone of softer material such as metal the cone will, however, rapidly be destroyed by erosion.
Trickle of the fuel causes formation of agglomerates which fall to the bottom of the combustion chamber and will be sintered there. In prior art nozzles, the distribution of the droplet size is moreover rather wide and the formation of droplets is disturbed by said clogging of the annular slot for secondary splitting air. The nozzles used today are sensitive as far as the strength is concerned and cannot stand today's demand of low flow of splitting air.
SUMMARY OF THE INVENTION
The related problems will be avoided by the method of the invention, including the shape of the air forming a cone tangent to the nozzle outlet.
The advantage of the invention is, above all, that the nozzle can be of a relatively simple construction and that there is obtained a narrow droplet size distribution and low trickle. By the flow of splitting air being changed, the droplet size distribution can be affected in order to obtain a major or minor proportion of fine droplets in relation to a normal distribution. Moreover, wear and clogging inside the fuel nozzle will be avoided and the tendency of forming agglomerates will be eliminated not the least due to the fact that a slot for secondary flow of splitting air no longer will be required because such flow can be dispensed with, which means a reduction of the splitting air consumption.
The nozzle for supply of paste fuel to a fluidized bed, the paste fuel being comminuted, comprises, as does the nozzle in EP-A-0182,545, a conduit for supply of the paste fuel. The conduit of the invention tapers towards the outlet of the nozzle in the proximity thereof, and a spout for supply of splitting air which is located centrally of the conduit extends towards the outlet of the nozzle, the opening of said spout being located upstream of the outlet of the nozzle. Such a nozzle is of a simpler construction than the nozzles now used above all because no expensive cone of ceramic material is required, which is consumed and must be replaced now and then, and because it is not necessary for the nozzle to have a slot for a flow of secondary splitting air.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to explain the invention in more detail, reference is made to the accompanying drawings in which
FIG. 1 is an axial cross sectional view of a nozzle for supply of paste fuel to a fluidized bed,
FIG. 2 is an enlarged axial cross se
REFERENCES:
patent: 3050262 (1962-08-01), Curtis
patent: 3896996 (1975-07-01), Roest et al.
patent: 4284242 (1981-08-01), Randell
patent: 4292022 (1981-09-01), Hosek
patent: 4361285 (1982-11-01), Koppehele et al.
patent: 4544095 (1985-10-01), Litzen
patent: 4592506 (1986-01-01), Capes et al.
Barker Stephen N.
Wallin Thomas
ABB Carbon AB
Larson Herbert W.
Merritt Karen B.
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