Process description

The liquid to be dried is pumped to the top of the drying chamber by a variable-speed progressing cavity pump, which provides a very smooth flow and constant flow rate. It is atomised by a two-fluid nozzle and enters the drying chamber as a fine droplet dispersion.

Hot air is blown into the chamber, on to the droplets causing flash evaporation of the surface moisture.

Theboundmoistureintheparticlesisevaporatedinthetimethatthey falltothedischargepointatthebaseofthecone(theresidencetime). Inthisconfigurationtheparticletemperaturewillneverexceedthewet bulbtemperatureoftheexhaustair.

A variable-speed centrifugal fan provides control over the inlet air flowandasteadyinlettemperatureisachievedbyusingathree-term controller in conjunction with an electric heater. A second variable- speed fan draws air from the chamber through a cyclone separator. This‘push-pull’fansystemprovidesflexibilitytooperatethechamber atvariablepressureswithvariableresidencetimes.

Two powder collection points are provided, one at the bottom of the mainchamber,andoneonthecycloneseparator.Thisenablesparticles ofdifferentsizestobecollectedsimultaneouslyand/orseparately.

Exhaust-airrelativehumiditycanbemeasuredandcontrolledso astoenablethesystemtorunattherequiredRHlevel.

Thenozzleisanexternal-mixtwo-fluidatomisingnozzle.Compressed airisdirectedontotheliquidstreamasitleavesthenozzlebodyand immediately atomises it. With this type of nozzle the orifice is larger than a single fluid type, and so it is possible to atomise more viscous productsandevenproductscontainingsuspendedsolids.

Features / benefits

No clogging, no need for de-blocking devices

Co-current flow for drying heat sensitive products

Counter-current flow maximises chamber residence time for non-heat sensitive products

Residence times in the drying cylinder variable up to 9 seconds u Data recording to computer for rapid evaluation and comparison u Accessory sets are available to quickly change fromdrying to spray chilling

Drying air temperature up to 250°C

Maximum flow rate up to 7 l/hr

Maximum evaporation rate of 3 l/hr

Tall form chamber straight side to diameter ratio of 3:1 conical discharge section

Advanced two-fluid nozzle atomisation system

Individual inlet and exhaust fans with variable-speed control

Bag filter and trace heating options

Flexible controls and full instrumentation provided in the IP65 control console

Easily dismantled for inspection and cleaning purposes

Compact, mobile design

Data logging facility for all key operating parameters

Powder discharges from two points, chamber and cyclone

Low noise levels

Control and measurement of relative humidity

Spark arrester on input and enhanced safety extraction fan