Vacuum freeze drying

General

Vacuum cryogenic drying technology is currently worldwide most advanced technology for food dehydration processing. Compared with the commonly used drying method, the freeze-dried food produced with this technology features long period of quality assurance, good re-hydration nature, good-looking color, good flavor, taste and high content of nutritious components. The dried food basically remains unchanged in its volume and shape. This drying technology can be widely used in process of vegetables, fruits, condiments, aquatic products, biological products, medicine, beverage, exemplar etc.  Vacuum cryogenic drying equipment mainly includes food pre-freezing system, drying bin system, heating system, vacuum system, refrigerating system, material conveying system, medium system, pneumatic system, cleaning and sterilizing system.

Working principle

The vacuum cryogenic drying is a drying method for dehydration and preservation of substances. It sublimes the moisture in the pre-processed substance from solid state into gaseous state by -30℃quick-freezing under the vacuum condition.

Main characteristics of PVG-FDG vacuum cryogenic drying equipment

1. The vacuum system is in combination structure of water-sealed pump + oil-sealed pump. The extraction of pre-vacuum is performed by oil-sealed pump group of large power and the vacuum for operation remains by water-sealed Roots pump group of small power so as to reduce energy consumption. Meanwhile, the water-sealed pump group can remove vacuity instability of the system due to poor water-removal performance of oil-sealed pump and emulsification deterioration of the pump oil.

2. Heating is conducted in closed water circulation system, where three-way adjusting valve is used for automatic adjustment of heat supply to the water circulation system to precisely control temperature of the heating plate. Besides, nitrogen is used for automatic pressure-keeping to ensure the working temperature of the hot water reaching 120℃.

3. The rear mounted and bottom mounted water catching cold traps are adopted. Compared with the split externally mounted cold trap, they are featured by short passageway, small resistance, and smooth design of water and steam passageway, equal water catching and improved water catching efficiency. The water catching cold traps adopted the unique way of ammonia single-phase cycle refrigeration, which has good stability of liquid supply for refrigeration and easy operation compared with universal liquid supply method s, the small and medium- sized equipment can adopt Freon for refrigeration and the flow can be adjusted by the expansion valve.

Main technical parameters of PVG-FDG series vacuum cryogenic drying equipment.