12. Pilot drying plants
a) Spray dryer I
Brand and model:Büttner – Schilde – Hass AG.
Capacity:0–7 L/h.
Description:The solution to be evaporated is injected as small droplets from the top of the dryer through a centrifugal nozzle driven by pressurized air. The feed rate can be adjusted within a specific range. The drying air is heated by four electric resistances and introduced into the dryer along with the solution. In a very short time, the fine particles dispersed in the drying air move toward the conical bottom of the dryer and are then carried to a cyclone, where vapor and solid particles are separated.
b) Spray dryer II
Brand and model:Industriewerke Karlsruhe, Model: C 80A-00.00.
Capacity:0–50 L/h.
Description:The solution to be dried is injected through an atomizer at the top of the dryer, driven by a dosing pump. The feed rate can vary according to process requirements. The atomized solution is dried through direct contact with hot air, which is heated by electric resistances. Finally, a cyclone filter separates the dried material.
c) Vacuum belt dryer
Brand and model:ISESA
Capacity:Depends on the solution to be dried.
Description:The dryer consists of a continuous Teflon belt, 495 cm long and 43 cm wide, mounted horizontally inside a stainless steel cylinder maintained under vacuum. The belt moves over 5 flat heat exchangers, which can be fed with steam, thermal fluid, or cooling water. The solution to be dried (which must have a viscosity of approximately 1,000 centipoise) is fed at one end of the dryer, ensuring uniform distribution across the belt width. The belt moves continuously at a speed of 5–25 cm/min. The solution comes into successive contact with the surfaces of the 5 heat exchangers, maintained at set temperatures. Heat transferred through the Teflon belt causes gradual evaporation of the solvent. If the material has plastic properties, the last exchanger is typically used as a cooler. At the end of the dryer, a mechanical scraper removes the solid from the belt and transfers it to a container.
d) Tray dryer
Brand and model:In-house manufacturing.
Capacity:Evaporation rate of 5 kg/h of water.
Description:The dryer has 5 trays where the wet product is placed. It receives direct thermal input from hot air recirculated by an axial fan located inside the drying chamber. Heating is provided by a 2 kW electric resistance with a temperature control system. The chamber measures 2 m in length, 1.3 m in width, and 2 m in height.