BUCHI Inert Loop B-295 - Manual (Page 55)

6 Operation
55 B-290 Operation Manual, Version I
6 .8 Operation with the Spray Chilling Accessory
To operate the Spray Chilling Accessory, proceed as follows:
1. Fill a heating liquid, e.g. water or a thermal oil (polyethylene glycol PEG 400 with low viscosity)
into the heating bath and check whether the tubings are connected correctly. For sample melting
points below 50 °C, water can be used as heating liquid. For melting points up to 70 °C thermal
oil or polyethylene glycol is recommended. Consider the maximum heating liquid volume of 1.4
liters. Close product vessel with the PTFE cover and close the spray chilling accessory with the
cover comprising the heating coil.
2. Switch on the Mini Spray Dryer B-290. The instrument is preset to the spray chilling mode, due
to the connected long temperature probe.
3. Keep the feeding needle valve closed. Fill in the sample product into the product feed vessel.
4. Switch on the peristaltic pump with a pump rate of 60 % to circulate the heating liquid from the
bath to the nozzle and back to the bath. Keep the heating liquid circulating.
5. Set the temperature of the heating bath. A heating temperature of about 50 % above the melting
point of the product is recommended (e.g. melting point 60 °C: heating bath 1.5×60 °C = 90 °C).
Switch on the heater.
6. Turn on the compressed air flow to approximately 40 mm. The air is preheated through the hot
capillary in the heating bath before entering the nozzle. Thus, the air will not lead to a cooling
down of the melt in the nozzle.
7. Wait approximately 1 hour until the system is heated up and has reached steady state tempera-
ture conditions. The temperature is displayed as OUTLET temperature on the Mini Spray Dryer
B-290.
8. Check if the melt in the product feed vessel is completely liquefied. Use a stirring stick to improve
the melting process.
9. In case of an optional cooling of the inlet air, switch on the Dehumidifier B-296. The INLET
temperature shows the temperature of the cooling air. Switch on the Dehumidifier B-296.
10. Switch on the aspirator. The aspirator generates the gas flow in the system. A setting of 100 %
is recommended. Wait until the complete system has reached steady state conditions. Inlet air
temperatures of around +10 °C to +15 °C can be reached with the Dehumidifier B-296. Check
that the melt in the product feed vessel is completely liquid.
11. Open the needle valve carefully and watch the liquefied feed entering the feeding tube between
needle valve and nozzle inlet. The hot melt will pour into the two fluid nozzle. In case of a blocked
nozzle, push the nozzle cleaning. The spray chilling process starts.
12. Wait until the entire product is dispersed. A spray chilling run is typically quick and the particles
are collected in the spray chamber and product collection vessel of the cyclone.
13. Switch off the aspirator, the heater, and the peristaltic pump and turn off the spray flow.
14. Remove the product collection vessel with the powder.
15. Carefully empty the heating liquid from the bath by opening the hose clamp of the drain tubing.
16. Let the spray chilling accessory cool down after the experiment with its covers on. Fill the spray
chilling accessory with the cleaning agent and open the needle valve.
17. If the accessory is blocked remove it for cleaning. Use hot water, soap solutions and a brush. Put
the blocked metal parts in a heating oven to melt the stocked product.
18. Wash all parts with water and let them dry.
19. The silicone tubing between the spray chilling accessory and the nozzle has to be replaced if it is
blocked or broken.