Refrigerant substitution has always been a hot topic in the industry.
Freon is gradually disappearing because of its unfriendliness to the environment. In the field of industrial refrigeration, ammonia refrigerant is popular because of its low price and mature technology. However, in recent years, due to the continuous occurrence of ammonia accidents in Jilin and Shanghai, the industry has been more and more frightened.
So, is there a refrigerant that meets the requirements of energy conservation and environmental protection, and is relatively safe? Although there is not yet an authoritative consensus in the industry, carbon dioxide is becoming more and more powerful in the industry.. To this end, the reporter specially invited to Danfoss industrial refrigeration China and Asia Pacific application manager Mr. Tony Wong, share of carbon dioxide refrigeration market at home and abroad in the field of industrial refrigeration, and the development trend of the future.
Carbon dioxide refrigerant: safe, environmentally friendly and pollution-free.
It is understood that as early as 1869, Americans used carbon dioxide as a refrigerant to make an ice machine, which opened the way for the use of carbon dioxide as a refrigerant. In synthetic such as Freon refrigerating agent before has not developed, though carbon dioxide is not the only option for early refrigerants, but its early in the food industry and civil building air conditioning, and other fields has a major position. However, after the advent of synthetic refrigerants, carbon dioxide was quickly snubbed and retreated into a corner.
The extensive study of CFCs and HCFCs substitutes has been ongoing since the Montreal protocol was signed. Though the new alternative working medium has started commercial production, but it was found that the new alternative working medium and can't meet the requirements of "long-term" substitutes, most of the new medium has higher or other dominant greenhouse effect index and potential defects. Therefore, the application of natural works is still the primary concern, especially for some applications of carbon dioxide.
It is understood that carbon dioxide as refrigerant has advantage of high density, low viscosity, small flow loss, heat transfer effect, and through the strengthening of the role of heat transfer, can make the loop is not high up. At the same time, the environmental performance of carbon dioxide is good, the cost is easy to obtain, the stability is good, and it is beneficial to reduce the volume of the refrigerating device. Of course, the use of carbon dioxide as refrigerant also has corresponding high requirements. The relatively high critical pressure of carbon dioxide and the low critical temperature also give it a lot of difficulties in making refrigerant. Both subcritical circulation and across the critical cycle, carbon dioxide refrigeration system operating pressure will be higher than that of traditional refrigeration and air conditioning system, it will inevitably bring many new challenges to the design of the system and components.
Foreign development is good: carbon dioxide refrigeration is more mature.
What are the performance of carbon dioxide refrigeration systems in developed countries? The industry believes that it is widely promoted by the developed countries and as a reserve for future development, whether in design or safe operation, it tends to mature.
Mr. Huang said that in 1990, some developed countries in Europe and the United States began to explore carbon dioxide refrigeration. At the beginning of 2000, a actual project started construction or have been put into operation, the time to complete each carbon dioxide refrigeration system, will cause widespread attention, including the system used in the compressor, piping system, valves, etc. By 2006, Europe had applications in industrial refrigeration, supermarket refrigeration and other fields, and industrial refrigeration was about 200 to 300 orders of magnitude. Since then, more and more systems have pushed the various components of the carbon dioxide system into standardized configurations. Mr Huang predicts that the overall development of carbon dioxide is still on the rise, with 500 to 600 systems operating in Europe's industrial refrigeration system.
In addition, countries are actively drafting relevant standards and norms to promote the rapid development and sustainable application of the environmental protection industry. The safety standards for carbon dioxide refrigeration systems, such as the UK, have been revised to address the pressure and safety requirements of the refrigeration system. All relevant institutions and personnel, including design, owner, operation and installation personnel should attach great importance to this safety standard.
Domestic development is fast: carbon dioxide is still in its infancy.
As an important global refrigeration market, China's refrigerant substitution situation is also very serious. Similarly, every step of China's efforts to reduce carbon emissions has been arduous.
According to huang zhihua, the domestic carbon dioxide refrigeration is still in the early stage and even the start-up stage. When is it mature? It also takes time to learn, try and gain experience. Although China has lagged behind in the alternative to carbon dioxide refrigerants, there has been considerable progress in the efforts of all parties.
Danfoss is to reduce the carbon footprint of active responder, and devote themselves to the application of co2 in Europe and the United States experience to introduce Chinese colleagues, in order to promote the development of the natural working substance in the Chinese market a hand.
Danfoss has been promoting carbon dioxide cooling in China earlier, with the first round of carbon dioxide roadshows in nine cities across the country by the end of 2011.The response was enthusiastic, but it also aroused more interest from colleagues in the industry. We hope to continue our in-depth discussion.Therefore, in 2012, we organized a more in-depth and detailed road show to introduce the more specific application technologies in the carbon dioxide system and achieved better results.2013, danfoss, realizes the co2 system corresponding to the valve product production and commercial applications, to now, we are the mainstream of industrial refrigeration products have achieved 52 kg pressure level of the minimum requirements, that is to say, the standardization of danfoss provide industrial refrigeration valve product, can be compatible with carbon dioxide (co2) system.From an industrial refrigeration point of view, there is no "special" support for a particular project, but a whole series of gestures.
How to apply it to reality: only accumulation will has a mutation.
From several perspectives, manager Huang discusses the difficulties and obstacles in the promotion of carbon dioxide system. "The Chinese market is a global market," he said. "all the good things can be found at home, and many domestic manufacturers have developed carbon dioxide equipment. Carbon dioxide refrigeration without too much on technology threshold, but how to implement the specific projects, such as late system design, construction, maintenance, debugging and so on, is also very challenging, after all, everyone has to adapt to the system, the original ammonia, fluorine to turn to new areas, need more time to conquer.
In the process of installation, the carbon dioxide system puts forward new requirements on the bearing capacity of the system pipeline due to the high carbon dioxide pressure. At the same time, the carbon dioxide system has a higher requirement for water. The purity of carbon dioxide recommended by the international community is 99.9% dry, and the water content is less than 0.1%. This is a big Challeng this for actual operation, if the system is not completely hydrated during installation and operation, or lubricating oil has water in it. Carbon dioxide reacts with water to produce acid, which, on the basis of carbonation, is a more corrosive acid and a threat to the system. In the same way, also is faced with the problem of water with oil reaction and so on, these problems may have never met, only when really appeared gradually accumulate experience.
Carbon dioxide is a new technology, our country currently lacks experience related to system operators, this needs time to develop, and can stay behind after training to serve the industry for a long time, is also a need to consider the problem. Therefore, a new concept is introduced, so as to realize the efficient operation and safe operation of the system by improving the automation control level of the refrigeration system.
Put safety first: comprehensive prevention and response.
In recent years, several liquid ammonia accidents have caused the government and industry to tread on thin ice. In fact, any refrigerant should take full account of safety.
Like the ammonia refrigeration system, the carbon dioxide system also needs the comprehensive, systematic rules and regulations and the security system to realize effective control. At present, our country have not specifically made relevant specification for co2 refrigeration system. From the perspective of national standard, missing is still in the state, only reference to similar pressure level and safety level of specification, not systematic and standardized. In the concrete implementation process, there will be a variety of problems, some can only rely on enterprise experience accumulation.
"To fully consider the high pressure characteristics of the co2 cooling system, especially when the temperature is high, it can cause the fluctuation of the pressure," said Mr. Huang. If the pressure exceeds the safety range of the system, if there is not enough safety valve, there may be a large system damage and safety hazard. If the carbon dioxide system leaks, it can also cause serious harm. Mr. Huang added that this time will need to improve safety, in addition to the relief valve, condensing units, can be added at the time of temperature rise, by condensing units, cut down the temperature. Of course, you can also consider taking the initiative to discharge the safety valve before it starts to jump.
Look for the future: niche markets have more potential.
As the countries in the aspect of environmental protection and energy saving, and more associations, enterprises and the downstream customer's emphasis on environmental protection, security, has been more and more people begin to pay close attention to and support the carbon dioxide refrigeration system.
At present, the development of carbon dioxide is very fast, but the base is still small, and it is not clear whether it can become the mainstream of the market. From the experience of foreign development, the development of carbon dioxide refrigeration is not only the safety Angle, but also the energy consumption of the system. According to the Kyoto protocol and the Montreal protocol, Freon refrigerants will gradually be limited in China between 2013 and 2030.As a result, a large industrial refrigeration project (refrigerator, slaughterhouses, brewery, dairy, quick-frozen processing, fishery, etc.), the next few years the use of Freon will gradually is restricted, carbon dioxide system will have a place, after all, suitable is the best, in a more appropriate temperature range, smaller market segments, the application of carbon dioxide would have great potential.
R744 unit cooler