FR2470636A1 - Granulating or coating prod. in bed kept in circulation by gas stream - incorporating means of adjusting position of gas jet vertically allowing particle size modification - Google Patents

Abstract

An appts. for granulating or coating a prod. consists of a vessel of vertical axis comprising a lower part in the form of a truncated cone surmounted by a cylindrical part and connected to a gas feed pipe at its base of smaller dia. A bed of particles is obtd. in the vessel maintained in suspension and circulated in closed cycles by a stream of gas ascending in the neighbourhood of the axis in the form of a jet. The particles are displaced radially towards the walls of the vessel, then descend slowly to be taken up again by the ascending gas stream. The gas jet can be displaced in a vertical axis on either side of the horizontal plane contg. the smaller dia. of the conical part. The amt. of the displacement allowed is equal to +- 9/5 cube root 100 d, where d is the smaller dia. In comparison with prior art this appts. allows the particle size of the prod. to be adjusted by modifying the position of the jet.

Description

he

  Improvement to the spraying device

  granulating material in granulating devices and / cu

the coating in a gushing bed.

The present invention relates to an improvement to the

positive spraying of the product to be granulated in the equipment

reils for granulation and / or coating in a gushing bed.

The spouting beds (often also called

  geyser type) are beds of particles obtained in a

  girdle of vertical axis having at its lower part a frustoconical part at the tip of which one introduces a

  gas updraft. This gas stream maintains the par-

suspended particles and causes them to circulate in closed cycles. Indeed, the particles are entrained by the ascending gas current in the vicinity of the axis of the enclosure

  in the form of a kind of jet or geyser, move radia-

slowly towards the walls of the enclosure then slowly descend

  ment to return to the tip of the frustoconical part. There they are taken up by the ascending gas stream. The gushing bed is described in French patent 1125461 of Il

March 1955 filed by National Research Council.

  It is known to use the gushing bed to granulate fluid products which harden by evaporation of water or

solvent or by cooling and / or to coat parts

cules or nuclei made beforehand using pro-

hardenable fluids. According to this granulation process, the granules in the course of formation or the particles in the course of coating are kept in the form of a spouting bed.

  using a cold or hot ascending gas stream and

gas in ascending gas stream below the bed

  gushing the curable product. The latter is partial-

  hardened in the gas stream then settles on the parts

ticulates of the gushing bed present at the lower part of the frustoconical part. The layer of sprayed product finishes hardening while the particles are entrained by the

upward gas flow in the central jet and that they re-

descend along the walls of the enclosure.

  ticules arrive near the tip of the truncated part

conical of the enclosure, they receive a new layer of sprayed product. Granulation or coating is therefore done

2470636-

by depositing successive layers. This granulation process

  is described in French patents 1 275 463 and 1 354 758

placed on September 28, 1960 and November 20, respectively

  1961 by Potasse et Engrais Chimiques.

The devices used until now for granulation

  in a gushing bed are constituted by an enclosure of axis ver-

tical, comprising a cylindrical part. When we want

work continuously this enclosure is equipped with the

  of the overflow bed for the extraction of granules

  the finishes. The ascending gas stream is introduced at the base of smaller diameter of the frustoconical lower part of the enclosure.

In the devices used until now, spraying

  tion was carried out- using a sprayer mounted in a

  fixed lesson near the plane of the small base of the game

  frustoconical of the enclosure. In these devices one could diff-

  carefully adjust the particle size of the finished granules when

  we changed the product to be granulated or even during the

granulation.--

  The present invention relates to a perfecti'ment to the dis-

  positive spraying of the product to be granulated in the equipment

  reils for granulation and / or coating in a spouting bed

  constituted by a vertical axis enclosure comprising a

frustoconical lower tie surmounted by a cylindrical part and connected at its base 'of' smaller diameter to a pipe

gas supply characterized by the fact that the

spray nozzle is fixed so that it can move

  on a vertical axis on either side of the horizontal plane

  holding the smallest diameter of the frustoconical part of the

9 \ 3 / ----

  30. girdle; from a distance equal to + 9 1 00d o d is the most

  small diameter of the frustoconical part.

  It is in fact possible by modifying the position of the sprayer to continuously adjust the particle size of the product. Indeed if we are looking for a higher particle size we go back up the sprayer and if we are looking for a smaller particle size

  the sprayer is lowered.

  However when the sprayer is lowered below the plane O containing the base of smaller diameter of the part 73-

  frustoconical with a height greater than 100 d there is-

  mation of fines which are entrained by the ascending gas stream. If the sprayer is raised above the plane O by a height greater than 5 10 there are risks of agglomeration formation and consequently risks of blocking.

bed cage.

The device ensuring the mobility of the sprayer can

  be mechanical, electrical or pneumatic. A me-

suitable canicism is illustrated in figure 1. It consists of

fitting of a tube (1), with a double heating jacket, placed

  vertically and located in the axis of the frustoconical spraying part. The lower part of the tube is provided with articulations (2) ensuring a degree of freedom in the

vertical direction, while flexible conduits (3) allow

  attempt to circulate the heating fluid. The arrival (4) is fixed with a positive inclination towards the altitude of

  spraying, to the body of the device. Two limit stops (5)

  attempt the vertical displacement of the tube (1), which is action-

born by a positioning system (6) (lever, nut, screw

crank, index).

  In another device shown in Figure 2 the displacement of the vertical tube 1 is provided by a system (2) (pinion, rack) placed outside the device. By

an appropriate geometry of the base (3) of the apparatus, this

  it can be crossed vertically. A packing gland

sheaity (4) is kept protected from all dust by the

bell device (3).

The comparative example given below will better

understand the invention.

In a granulator having a diia-

  400 mm meter sulfur has been granulated. All conditions

  remained equal except that the position of the pul

verifier. Position of the sprayer. 13 + 7 _ 5 \ l100d + 5 \ 3 Lr 53 10 Grain size 5 0t5 d 5 OOd mm%

> 4.75 0 0 0.5

4.75 - 3.35 1 21 44.0

3.35 - 2.00 43 63 50.0

2.00 - 1.00 42 15 5.0

_1.00 -14 1 0.5

Claims (1)

R E V E N D I C A T I O N S   Improvement to the product spraying device to be granulated in apparatuses for granulation and / or filling   gagage in a gushing bed constituted by a vertical enclosure   cal comprising a frustoconical lower part surmounted by a cylindrical part and connected at its base of smaller diameter to a gas supply pipe characterized in that the spraying device is fixed so as to be able to move on a vertical axis on either side of the horizontal plane containing the smallest diameter of the frustoconical part of the enclosure, from a distance equal to + 9 3 dod is the smallest diameter of the frustoconical part.