Gustav Lorentzen: NH3/CO2 system development in China

By Caixia Mao, Sep 26, 2014, 09:54 3 minute reading

Chinese company Yantai Moon presented its latest research into CO2 technology, including the benefits of NH3/CO2 cascade solutions for industrial refrigeration, at the 2014 Gustav Lorentzen conference held in Hangzhou, China.

Through its 2014 Gustav Lorentzen (GL 2014) papers, Yantai Moon discussed the different stages leading up to the to the development of an NH3/CO2 system, and demonstrated that such systems can achieve a higher COP than other types of refrigeration systems. Yantai Moon’s NH3/CO2 cascade research received support from the UNDP (United Nations Development Program) and the Chinese government. 
“Our goal in attending Gustav Lorentzen this year is to convey our message of building an environmental friendly refrigeration technology and to share knowledge on green, low-carbon solutions,” continues Mr. Wang Liqun, from the marketing department of Yantai Moon, “We will  keep promoting sustainable solutions.”
Development of low charge Chinese NH3/CO2 system 
In their first GL 2014 presentation, Yantai Moon reviewed the different steps towards the development of an NH3/CO2 system. The project began in May 2011, when the UNDP and the Ministry of Environmental Protection chose Yantai Moon’s NH3/CO2 cascade refrigeration system development plan as a global HCFC-22 phase-out project.  On the 23 July 2013, the Chinese Government acknowledged that Yantai Moon’s development results filled a technological gap in Chinese national refrigeration technology. Following this, from September to November 2013, Yantai Moon organised a road show to promote CO2 refrigeration technology as a solution ready for large-scale application across China. 
The presentation also highlighted some technical aspects of the NH3/CO2 cascade system. For safety, ammonia is confined to the refrigeration unit within an equipment room. This reduces ammonia charge to 10% compared to traditional ammonia systems. What is more, the cascade system, takes full advantage the different heat transfer, mass transfer and refrigeration properties of NH3 and CO2, in particular the fact that CO2 has a higher heat exchange efficiency at lower temperatures. The system cascade systems can supply temperatures between 0°C and -52°C. 
Yantai Moon recommends that the NH3/CO2 system applied to quick freezing applications (-45°C to -40°C) and large cold storage (-33°C to -28°C) to maximise energy saving potential of the system.  
NH3/CO2 system comparative studies reveal cascade systems more efficient than ammonia only systems
In a second Yantai Moon paper titled “Research on CO2 Refrigeration System” by Ge Changwei, Jiang Shaoming and Yu Zhiqing, data analysis shows that a CO2 refrigeration system has a very high running efficiency in a temperature range of -55 °C to 5 °C. 
In the comparative study of an NH3/CO2 cascade refrigeration system with a two-stage ammonia compression refrigeration system, the COP of the NH3/CO2 cascade refrigeration system was between 8.8 and 10% higher, at an evaporating temperature of -45 °C. 
With regards to COP, when compares to an NH3 single stage refrigeration system, and NH3 double stage refrigeration systems, and R22 single stage refrigeration system, and an R22 double refrigeration system, the NH3/CO2 system achieved a COP of 2.18 at -40°C/+25°C and 1.78 at -50°C/+25°C, higher than any of the other refrigeration systems. 
Installation examples of NH3/CO2 system 
Yantai Moon also introduced some installation examples of NH3/CO2 systems in China. 
  • Yantai Fengrun Food Co., Ltd, installed an NH3/CO2 cascade refrigeration system in 2009. The system uses a CO2 screw compressor under the design condition of -40°C/35°C and heat capacity of 240kW. The system is fully automated and its installation has resulted in 10% energy savings. 
  • Weihai Jiuye Warehouse Logistics introduced two sets of NH3/CO2 cascade refrigeration systems with evaporation temperatures at -45°C and -35°C respectively. 
  • The largest refrigeration system using natural refrigerant system in China is the frozen shellfish and sea cucumber processing centre of the Roe Island Group, which also features an NH3/CO2 cascade refrigeration system.. 


By Caixia Mao

Sep 26, 2014, 09:54

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