Spray drying

Abstract

A method of preparing dry core-shell microcapsules from an aqueous dispersion of such capsules, comprising spraying the dispersion through a two-fluid air-liquid nozzle into a heated chamber having an upper part and a lower part, the spraying taking place in the upper part and the lower part being provided with a means of continuous capsule removal. The method allows the drying of capsules with considerably reduced losses.

Claims

1. A method of preparing dry core-shell microcapsules from an aqueous dispersion of such capsules, comprising spraying the dispersion through a two-fluid air-liquid nozzle into a heated chamber having an upper part and a lower part, the spraying taking place in the upper part and the lower part being provided with a means of continuous capsule removal.

2. The method according to claim 1, in which the means of continuous capsule removal is selected from rotary valves, double-flap valves and cycle valves.

3. The method according to claim 1, in which the capsules are removed in two stages.

4. The method according to claim 3, in which the means of continuous capsule removal from the heated chamber comprises a first stage of removal.

5. The method according to claim 3, in which a second removal stage comprises a cyclone separator equipped with a further means of continuous capsule removal.

6. A method of preparing dry core-shell microcapsules from an aqueous dispersion of such capsules, comprising spraying the dispersion through a two-fluid air-liquid nozzle into a heated chamber having an upper part and a lower part, the spraying taking place in the upper part and the lower part being provided with a continuous capsule remover.

7. The method according to claim 6, in which the continuous capsule remover is selected from rotary valves, double-flap valves and cycle valves.

8. The method according to claim 6, in which the capsules are removed in two stages.

9. The method according to claim 8, in which the continuous capsule remover from the heated chamber comprises a first stage of removal.

10. The method according to claim 8, in which a second removal stage comprises a cyclone separator equipped with a further continuous capsule remover.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 depicts a schematic view of a particular embodiment of the present subject matter.

(2) The disclosure is further described with reference to the accompanying drawing, which depicts a particular embodiment and which is not to be considered to be in any way limiting.

(3) A drying chamber generally indicated as 1 is supplied with capsules through a spray head 2 from a feed tank 3 by means of a pump 4. The chamber is supplied with heated drying air through a line 5, the air being drawn through a filter 6 by a fan 7 and then passed on to a heater 8 before entering the drying chamber 1 through a line 9. At the bottom of the drying chamber 1 is an inverted conical section 10 at the bottom of which is a rotary valve 11. This allows the removal of dried capsules continuously through line 12.

(4) Any capsules not recovered through valve 11 are recovered by passing the heated air out of the drying chamber via line 13 to a cyclone separator 14 also equipped with a rotary valve 15. This allows capsules to be removed via line 16.

(5) Potential pollutants are dealt with by means of a scrubber 17 which utilizes water from a tank 18 to clean the air from the cyclone separator. Waste water is collected in a holding tank 19 while cleaned air is exhausted to atmosphere by means of a fan 20.