Vacuum drying is the direction of the most priority in different industry branches. By the vacuum technique it is possible to dry a lot of dispersed materials to the desired humidity and, at the same time, to conserve a maximum quantity of useful substances in the dried material .
In 2007 the specialists of SPE RESST offered a vacuum ecologically-clean electricity-saving drying apparatus for dispersed material drying. The drying technique combines the processes of vacuumization and thermal heating. In the vacuum volume the drying process significantly accelerates, the water boiling temperature is decreasing and the evaporation intensity is increasing. The apparatus comprises a tubular resistive heat-insulated heating element, feed hopper, storage hopper for dried material, water-packed ring pump, vacuum pipeline and valves, systems of disperse material charging and discharging, meters of temperature, pressure, humidity, vacuum drying control systems (Fig.1.) The input end of the heater is connected to the feed hopper with a wet dispersed material. Another end of the heater is connected to the vacuum pipeline with the inlet branch of the vacuum pump via the storage hopper of dried material. The storage hopper of dried material is made as a separate vacuum-tight box whose one end is connected to the heater and second end to the inlet branch of the liquid-packet ring pump. This system provides a high-efficient continuous vacuum drying of dispersed materials.
Fig.1. Vacuum drying apparatus
The input end of the heater is provided with a suction air regulator permitting to control the dried material concentration in the turbulent flow. The drying regime is automatic. The yield is from 1 t/hour and more. The materiel being dried moving in the heater space in the turbulent flow collides with the pipe heated walls and is heated to the given temperature. The regime is controlled that provides a high quality of dried products with conserved physical-chemical properties. The heated dispersed material enters into the storage hopper where the moisture is separated from the dried material. The evaporated moisture goes into the vacuum pump and the dried material remains in the storage hopper. The maximum temperature of the heater is 400°C. The maximum power of the heater is 25 kW. The minimum pressure in the storage hopper is 100 mm Hg.
The process of dispersed material vacuum drying runs at temperatures from 40 to 60°C that provides the ecological purity of the drying technique. The developed drying apparatus is compact and movable, can be easy and quickly transported into the required region. The drying apparatus and applied technique permit to obtain finished products of a high quality, accelerate the drying process, as compared to other technologies, reduce the electricity consumption, decrease the weight and the cost value of the dried product and improve operating conditions for maintenance personnel. For example, to dry by this technology the grain with 20% initial humidity to the 10% humidity one needs the energy of 60W per 1 kg of the product to be dried, whereas the drying by standard methods requires 100 W per 1 kg and more. Maximum temperature of heating grain is 55°Ñ. The developed vacuum drying apparatus is cheap, ecologically clean, electricity saving, has small size, is ease in manufacturing and servicing, can be transported from one place to another.
The vacuum drying apparatus can be used in the agriculture, food industry, pharmaceutical, wood-working and power industries. It can be applied for drying: grains, coffee-beans, cacao, vegetables, fruits, sugar, chalk, turf, sawdust, silica gel, pressed grape skins and apple pomace and other dispersed materials.
Now, the developed and constructed vacuum drying apparatus is applied to test the technology for drying the dispersed material, having different form and content, depending on the heating temperature, pressure and time.
The vacuum drying apparatus is patented:
Patent number 81138, bulletin number 20 of 10.12.07. Ukraine,
Patent number 2005124594/06(027666) of 03.08.2005 Ukraine,
International patent number: PCT/UA2005/000051, Russia
International publication number: WO/2007/013866, date 01.02.2007.