Optimization Of Freeze-Drying Energy Consumption
One of the annoying facts about freeze-drying is the high energy consumption and the consequent high cost. Are there any practical ways to handle this problem? Here Hawach forwards 4 ways to optimize freeze-drying energy consumption.
1. Optimization of freeze-drying energy consumption — using the right compressor
At present, the freeze dryer generally uses a piston refrigeration compressor as the main engine of the refrigeration system. Compared with the reversed Carnot cycle, its efficiency is generally less than 50%. If a scroll or screw compressor is used as the main engine, its efficiency will increase by 10 %, which can achieve energy-saving effects. It is possible to consider using scroll compressors instead of piston compressors on laboratory lyophilizer, and use screw compressors on medium and large lyophilization machine.
2. Optimization of freeze-drying energy consumption — adopting a new high-efficiency heat exchanger
There are generally three types of heat exchangers for refrigeration systems in freeze dryers: air-cooled finned heat exchanger, water-cooled shell and tube exchanger, and plate heat exchanger.
Here are the ways to optimize freeze-drying energy consumption regarding heat exchanger：
For air-cooled finned heat exchangers, we can use smaller pipes of 6-7mm to accommodate more heat exchange area under the same volume, thereby reducing the heat transfer temperature difference and improving the efficiency.
For shell and tube water condensers, high-efficiency heat transfer tubes are commonly used to replace the original light tubes, and the heat transfer efficiency has been increased several times. Further work is to reduce the inlet and outlet water pressure drop thus reducing energy consumption in the freeze-drying process.
For the plate heat exchanger, we should use one with low resistance and low oil accumulation, one that can ensure the heat exchange medium in a turbulent heat exchange state.
3. Optimization of freeze-drying energy consumption — using new pumps and fans
Freeze-drying equipment generally uses two refrigeration methods, one is a double compression refrigeration system, the other is a cascade compression refrigeration system. The former is mainly used for medium and large-scale production freeze-drying equipment, generally called a water-cooled system; the latter is mainly used for small experimental freeze-drying equipment, generally called the air-cooled system.
A water cooling tower is required in a water-cooled system, and there is generally a fan and a water pump on the cooling tower. A fan is required in an air-cooled system.
To reduce the freeze-drying energy consumption, here we can make an improvement to the above-mentioned pumps and fans. We can replace fixed-frequency water pumps and fixed-frequency fans with variable-frequency water pumps and variable-frequency fans.
The advantage of a variable-frequency fan is:
A. Adjust the speed according to the thermal load, thereby adjusting the air volume.
B. In lower ambient temperature, it changes to a low speed to reduce fan energy consumption.
C. In higher ambient temperature, it changed to high speed to increase heat exchange capacity.
The advantage of a variable frequency water pump is:
Adjust the speed according to the heat load thus adjusting the water volume, which can also achieve the purpose of improving heat exchange.
4. Optimization of freeze-drying energy consumption — adopting better refrigeration throttle valve
At present, freeze dryers generally use thermal expansion valves as refrigeration throttling components. It is envisaged that electronic expansion valves can be used instead of thermal expansion valves in the future.
Electronic expansion valve has the following advantages:
A. It can provide very precise temperature control;
B. Applicable to all refrigerants;
C. It has a shut-off function, which can eliminate the solenoid valve and avoid the liquid hammer failure.
Hope this article about reducing energy consumption in freeze-drying consumption can assist you.