Drying and gas or vapor contact with solids – Process – With contacting of material treated with solid or liquid agent
Patent
1994-10-26
1996-05-28
Lopez, F. Daniel
Drying and gas or vapor contact with solids
Process
With contacting of material treated with solid or liquid agent
34353, 34370, 34372, 34423, 34424, 34426, 34480, 34 69, 34 71, 34513, F26B 300
Patent
active
055199488
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a process for the production of pourable free-flowing granules of useful materials or mixtures thereof, which are suitable as and/or for use in wetting agents, detergents and/or cleaning products, from aqueous solutions and/or suspensions of such materials by fluidized-bed spray granulation in a hot fluidizing gas in the region of normal pressure.
Processes for the production of particles on an industrial scale from initially liquid products, i.e. from solutions or suspensions, include in particular spray drying, spray drying with integrated fluidized-bed agglomeration and fluidized-bed spray granulation. For decades now, spray drying has been typically used worldwide for the industrial-scale production of granules from aqueous preparations of useful materials of the type mentioned at the beginning. Hot air or mixtures of air and hot waste combustion gases are used as the drying gas stream. Washing powders and useful materials and mixtures thereof for the production of laundry detergents in pourable free-flowing powder form are industrially obtained in so-called spray-drying towers generally operated at ambient pressure either in countercurrent or, occasionally, in co-current.
DISCUSSION OF RELATED ART
The use of fluidized-bed spray granulation for the production of detergent granules is also known from the prior art (Uhlemann in Chem.-Ing.-Tech. 62 (1990), No. 10, pages 822-834 and EP-B-163 836). In this process, which is carried out far more rarely for the production of powder-form wetting agents, detergents and cleaning products, solid particles are kept suspended in an upwardly directed gas stream. In this state, the particles are separated from one another and are thus universally accessible to the droplets formed when liquid is sprayed into the fluidized bed. In addition, intensive heat exchange and mass transfer between the solid particles and the gas stream take place in this state.
Now, when a sprayed droplet meets a suspended particle, the liquid product of the sprayed droplet spreads over the solid substrate. The intensive heat exchange and mass transfer with the surrounding gas stream results in drying and solidification of the liquid film. As a result of repeated spraying, spreading and solidification, the particle grows like an onion. The particle with the required particle size is compact and also substantially round.
In the fluidized-bed spray granulation of aqueous preparations of the substances mentioned at the beginning, hot air is used as the fluidizing gas in the same way as in spray drying. In addition, the use of nitrogen gas is mentioned in EP-B-163 836.
In addition to the discretionary availability of the gas phase, advantages of drying using hot air as the drying gas include inter alia the possibility of working in so-called open systems which enable the moisture-laden hot gas phase to be disposed of without difficulty by discharge into the outside atmosphere. In addition, intensive physicochemical investigations into the course followed by the drying process have shown that drying with hot air takes place effectively and quickly, even where comparatively mild hot gas temperatures are used. The drying process on the moist particle actually begins at comparatively low temperatures, for example at particle temperatures of around 40.degree. C., largely irrespective of the temperature of the hot gas used and continues with a comparatively slow increase in the particle temperature to the boiling range of water under normal pressure. Overall, the drying process in hot air takes place quickly and very effectively, even in the final stages, so that the useful materials are exposed to comparatively mild temperatures during drying to form the free-flowing particles.
Among the disadvantages and limitations of this type of process for the specialist field targeted by the invention of the drying of useful materials or mixtures thereof in the production of laundry detergents and/or cleaning products, the following points are mentioned by
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Uhlmann, Chem. Ing.-Tech. 62 (1990), Nr. 10, Seiten 822-834.
Gehrmann, Chem.-Ing.-Tech. 62 (1990), Nr. 10, Seiten 512-520.
A. M. Trommelen et al., "Evaporation and Drying of Drops in Superheated Vapors" AICHE, Journal 16 (1970), Seiten 857-867.
Colin Beeby et al. "Stam Drying", Plenary Lecture, Proc. 4th, Int. Drying Sym. Kyoto (eds. R. Toei und Arun S. Mujamdar), 1984, Bd. 1, Seiten 51-68.
W. A. Stein, "Berechnung der Verdampfung von Flussigkeit aus feuchten Produkten im Spruhturm", Verfahrenstechnik 7 (1973), Seiten 262-267.
Beck Wilhelm
Fues Johann
Koch Otto
Raehse Wilfried
Grandmaison Real J.
Henkel Corporation
Jaeschke Wayne C.
Lopez F. Daniel
Szoke Ernest G.
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