Process for the preparation of granules

A process for the preparation of solid granules from a liquid material which process comprises the steps of:

• (1) forming and maintaining, in a vessel and above a feeding device therein, a fluidized bed of solid particulate nuclei by upwardly flowing a first relatively low velocity fluidizing gas stream through said bed, said feeding device comprising:
• (a) a first central conduit for delivering an upward flow of starting liquid material into the vessel from the exit of said first conduit in the form of an initially virtually closed conical film, with a vertex angle of 50.degree.-110.degree., and with an internal turbulence such that the Weber number, expressed as:
• We.delta.=.rho..sub.1 (U.sub.1).sup.2 .delta./.sigma..sub.1,
• is greater than 2000, and
• where:
• .rho..sub.1 =the density of the liquid material, in kg/m.sup.3,
• U.sub.1 =the potential velocity of the liquid material, in m/sec.,
• .sigma..sub.1 =the surface tension of the liquid material, in N/m,
• .delta.=the film thickness upon exit from the central channel, in m,
• (b) said first central conduit also having means for imparting a horizontal velocity component to said starting liquid prior to its exit, and
• (c) a second concentric conduit annularly disposed about said first conduit for delivering an upward flow of a second gas stream into the vessel from the exit thereof,
• (2) introducing said starting liquid through said first central conduit to form said vertually closed conical film with said vertex angle and said Weber number, with a thrust exceeding the thrust of said second gas stream and having a horizontal velocity component,
• (3) introducing, through said concentric annular conduit said second gas stream in a predominantly vertical direction so that the second gas stream is made to hit the conical film at an angle of 30.degree.-80.degree. and at an initially higher velocity, relative to the velocity of said first gas stream, which second gas velocity is such that the ratio:
• .rho..sub.gas [U.sub.gas ].sup.2 /.sigma..sub.1
• where:
• .rho..sub.gas =the density of the gas, in kg/m.sup.3
• U.sub.gas =the potential velocity of the gas, in m/sec., and
• .sigma..sub. = the surface tension of the liquid material, in N/m, is from 5.times.10.sup.5 to 50.times.10.sup.5 m.sup.-1,
• thereby forming a dilute zone of solid nuclei above the exit of said feeding device, whereby
• (a) said second gas stream impacts said virtually closed conical film to nebulize the same into very fine liquid droplets, to form a droplet loaded gas stream,
• (b) said droplet loaded gas stream aspirates a portion of the nuclei from said fluidized bed into said dilute zone,
• (c) said aspirated solid particulate nuclei thus contact said very fine liquid droplets to moisten said nuclei, and
• (d) allowing the liquid material thereby taken up by the nuclei to soldify thereon causing the solid nuclei to grow in size, and
• (4) thereafter removing the thus-obtained granules from said vessel.