Organic compounds -- part of the class 532-570 series – Organic compounds – Four or more ring nitrogens in the bicyclo ring system
Patent
1981-11-16
1984-08-14
Ford, John M.
Organic compounds -- part of the class 532-570 series
Organic compounds
Four or more ring nitrogens in the bicyclo ring system
C07D25160
Patent
active
044658320
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the spraying of a liquid by means of a gas into a fluidized bed of solid material, in which process said spraying is conducted by means of a two-phase spraying device, consisting of a liquid feed tube fitted concentrically in a gas feed tube, in which device the end face of the liquid feed tube and the inner wall of the part of the gas feed tube extending beyond this end face are chamfered at an angle of 70.degree.-90.degree. so that between this face and this wall there is a conical channel, and this inner wall connects, via a rounded area, to the inner wall of an outflow channel fitted coaxially in respect of the liquid feed tube, of which channel the smallest inside diameter is 1 to 1.6 times the inside diameter of the outflow opening of the liquid feed tube and 2.5 to 10 times the curvature radius of the rounded area, as known from the U.S. Pat. No. 4,109,090 (which is incorporated herein by reference).
With such a process large quantities of liquid can be sprayed at a relatively low gas velocity. This is particularly of importance in the spraying of a liquid into a fluidized bed of a solid substance, because in applying a low outflow rate there will be less pulverizing of the solid substance so that the residence time of the solid substance in the fluidized bed is increased. Furthermore, the application of low gas velocities is energetically favourable.
The known sprayers are used, inter alia, in the granulation of urea or fertilizers, such as ammonium nitrate, etc. in a fluidized bed and in the preparation of melamine by spraying urea into a fluidized bed of an inert or catalytically active material by means of ammonia or a mixture of ammonia and carbon dioxide.
A very important advantage of this sprayer compared with other known sprayers is that the outflow channel is less exposed to wear.
In certain applications of the said process, it has been found, however, that some wear of the sprayer occurs due to sensitivity of the sprayer to deviations from the optimum form.
Minor deviations from this form or changes in the operating conditions caused erosion of the outflow opening of the sprayer when used for spraying liquid into a fluidized bed of solid material.
It has surprisingly been found that the cause of this phenomenon lies in the fact that already with a small change in form or conditions, the flow picture in the outflow channel can be such that the jet issuing from the channel becomes detached from the wall of the channel. The static pressure along the wall is then lower than the pressure in the area surrounding the sprayer, in consequence of which solid substance from the fluidized bed is sucked into the outflow channel and erodes the wall in an eddy occurring at the place of the wall.
The invention provides a process for the spraying of a liquid which process is less sensitive to deviations from the optimum design or to changes in the operating conditions of the sprayers.
According to the invention the outflow channel is, seen into the flow direction, conically narrowed.
The narrowing of the channel creates a pressure increase along the wall, which increase is such that, under all circumstances, the pressure at least at the place where the medium leaves the nozzle is greater than outside the nozzle. There can then be no reflux of solid substance from the fluidized bed into the channel. However, care must be taken that the smallest diameter of the narrowed part is not smaller than the inside diameter of the outflow opening of the liquid feed tube in order to avoid wear caused by liquid flowing along the wall of the nozzle.
Generally it will suffice for only the end of the sprayer outflow channel to be provided with a narrowed part, in which case the conically narrowed part of the outflow nozzle is connected, via a cylindrical part, to the rounded transition on the inner wall of the gas feed tube. If, in this case, there should be a partial vacuum locally along the wall of the nozzle, reflux of medium from the surrounding area into the channel will yet be p
REFERENCES:
patent: 2566229 (1951-08-01), Mackay
patent: 3014666 (1961-12-01), Verbouwens
patent: 3377350 (1968-04-01), Watson et al.
patent: 3475132 (1969-10-01), Seifert
patent: 3727839 (1973-04-01), Marsh
patent: 3831843 (1974-08-01), Masai
patent: 4109090 (1978-08-01), van Hardeveld et al.
patent: 4156080 (1979-05-01), van Herdeveld
de Wit Willem
Vermijs Winfried J. W.
Ford John M.
Stamicarbon B.V.
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