An advanced domestic industrial refrigeration CO₂ cascade system with Danfoss contribution

Since it is located in the downtown, the project is applied with a common solution in European countries as NH₃/CO₂ cascade system for considering the safety factor to strictly limit the ammonia charge. The NH₃/CO₂ system features one high-temperature system and one low temperature one. As a result, ammonia can be reduced to 10% of the total charged used in standing alone of the ammonia systems, which ensure a more safe environment for the cold storage and food production. ON the CO₂ side, Danfoss valves rated at an MWP (Maximum Working Pressure) of 52 bar made it ideal to fulfill the plant design conditions. Under the high-pressure conditions, the system was furnished with the modular valve stations, like Danfoss ICF control solution and ICV industrial control valve, to ensure good operation, and simplify the maintenance and service of the system.

As required by the customer as "fully automated engine room", the precise liquid level control solution that Danfoss provided can guarantee a good stability for the system. Liquid level control is considered key to offer a stable and reliable liquid feed and exert a big influence on the operation and efficiency of the system. Due to the low dielectric constant of the CO₂ refrigerant and the complex condition in the liquid separator, traditional capacitive level probes are not accurate and present erratic readings during operation. Danfoss newly introduced liquid level sensor AKS 4100(U) has been applied in this project, and achieved a precise and reliable liquid level reading by its new TDR (Time Domain Reflectometry) technology. As a result, the system can control opening of the Danfoss ICM motorized valve to enlarge the setting range of the capacity. Meanwhile, this arrangement is more flexible and compact, and easy for the remote control, which is the precondition of the unattended station.

For the efficiency saving consideration, the project is installed with CO₂ compressor (manufactured by Yantai Moon) to operate the hot gas defrosting. Successfully applied in the solution, Danfoss ICM series motorized valve is used to control the defrost process from hot gas supply and suction line pressure equalization once the sequence is terminated. FengRun's NH3/ CO₂ cascade system is in a smooth operation, and the system already reduced electricity usage for refrigeration by around 10% every year for the company.

Danfoss industrial refrigeration national sales manager Mr. Yan Lixin has expressed "I'm proud of the successful cooperation that Danfoss automatic control solution on the Yantai FengRun project. As a leading company in CO₂ refrigeration technology, Danfoss would like to share its rich experience and cases from Europe to Chinese partners. I can clear see that CO₂ solutions will have a good future in China refrigeration related industries, and we Danfoss will contribute more to this field with info sharing, project instruction, system guidance and product supply."

As a kind of greenhouse gas, the reduction of the CO₂ discharge can release the greenhouse effect. Meanwhile, CO₂ as a natural refrigerant applying in the refrigeration field bears a long history. Compared with the traditional refrigerant, CO₂ can represent the trend of the future refrigeration as its environmental and safe factors. 100 years ago, CO₂ has once applied in the ice machine. A century later, CO₂ has re-entered people's view based on its excellent advantages.

To promote CO₂ as a natural refrigerant and achieve the "Twelfth five-year" plan of energy saving and emission reduction, Danfoss industrial refrigeration offered two series of "CO₂ road show" to the Chinese peers in late 2011 and early 2012. Two phases of road show routed over 15 cities with over thousands attendees, Danfoss also successfully promote their solutions in energy saving, safety and environmental friendly of CO₂ refrigerant through this event.