Take the "life gate" in your own hands

“In China, the annual industrial energy consumption is about 2.91 billion tons of standard coal, but the residual heat (low grade thermal energy) below 150 degrees Celsius is often 'waste heat', and its total amount is equivalent to 14.2% of industrial energy. If 40% of waste heat can be effectively The use of one year will save 165 million tons of standard coal, which is of great significance," said Wang Ruzhu, director of the Institute of Refrigeration and Cryogenic Engineering at Shanghai Jiao Tong University.

Professor Wang Ruzhu has been "smashing" with green energy for more than 30 years. The Sino-Italian Green Energy Laboratory, which houses more than 20 top green energy technologies, is an integrated manifestation of his many years of technical breakthroughs. Here, based on the research and development of several decades of refrigeration and heat transfer technology, Wang Ruzhu led the team to carry out the project of “Low-grade residual energy recovery technology and heat pump equipment R&D and demonstration” to solve the “pain point” of energy saving and emission reduction.

As an energy-saving technology, heat pump can turn low-temperature waste heat into useful high-grade heat energy. For example, instead of conventional coal boiler heating, it can greatly alleviate the tension of central heating heat source in the north, and at the same time realize energy saving and consumption reduction of industrial production. More blue, greener.

The "engine" behind the super heat pump

Waste heat at different temperatures has different uses. For example, the medium and high temperature residual heat can be used to generate electricity through the heat engine. The medium and low temperature waste heat can be used for power generation, refrigeration and heat supply through recovery, and the low temperature waste heat can be supplied with domestic hot water through the heat pump. By consuming a small amount of fossil energy or electricity, the recovered waste heat can be converted into useful high-grade heat for industrial processes or heating projects.

"The low temperature, low energy density and dispersion are the main problems that are difficult to recycle at low temperature and waste heat," said Wang Ruzhu. Compressed heat pumps, absorption heat pumps and chemical heat pumps are the main ways to improve the quality of waste heat. Although the three heat pump technologies have been developed, it has been difficult to break through the bottlenecks of heat pump capacity, energy efficiency ratio, temperature rise and reliability. The project not only needs to overcome technical problems, but also consider economic benefits. If energy saving is not cost-effective, these technologies and equipment are also difficult to promote and apply.

In this regard, Wang Ruzhu led the project team to overcome difficulties, through the development of a single technology and innovation in processes, processes and other aspects, the development of high efficiency, large capacity, thermal load adaptability of the "super" heat pump, breaking through the low The technical barriers to the application of scale and capacity have been promoted, and the development of the emerging heat pump equipment industry has been promoted.

Performance improvement and system optimization matching are key to improving the energy efficiency of compression heat pumps. “General equipment uses a single system of one evaporator and one condenser,” said Wang Ruzhu. The project team divided the compression heat pump evaporation and condensation temperature into two sections, and adopted the independent countercurrent dual system for segmentation evaporation and staged condensation, which reduced the heat exchange temperature difference between evaporation and condensation, and reduced the compressor pressure ratio, thereby improving energy efficiency.

“The high-performance absorption heat pump demonstration unit has a particularly large capacity and can only be assembled in the field. Any rework or modification will cost a lot.” Dr. Pan Quanwen of the project team said that due to the large size of the unit, it is necessary to divide the design according to the limit size of transportation. And manufacturing, and rigorous testing and quality control of each component to ensure a successful assembly in the field.

In contrast, the technical maturity of chemical heat pumps is much lower than that of compression and absorption heat pumps. The 50-kilowatt chemical heat pump researched by the project team has no precedents for reference in the world. The unremitting efforts of the researchers ensure the success of the demonstration project.

"Eggs along the way", the industrialization spillover effect is significant

The industrial application of the research provides a vast world for the super heat pump developed by the project team.

The compression heat pump demonstration unit used in the Anshan Steel Lingshan heating renovation project has improved the heating energy efficiency comparison technology by 15%-20%, reaching 6.67, and the heat output capacity of 9 MW, which can save more than 3,500 tons of standard coal per year. "At present, the world's most advanced unit energy efficiency ratio is only about 5.5-5.8, our unit has surpassed the world's most advanced level." Wang Ruzhu is very proud. "After the demonstration of the heat pump system, the customer immediately added another five."

In the demonstration project of waste heat recovery heating in Xigu Thermal Power Plant of Datang Gansu Power Generation Co., Ltd., the efficiency of the high-efficiency absorption heat pump developed by the project is 1.77 times that of steam heating. At present, two heating seasons have been stably operated. “The first heating season recovered about 434,000 tons of standard coal waste heat, saving 529,000 tons of water and reducing 135,000 tons of carbon dioxide emissions.” Wang Ruzhu said that this is equivalent to the heating capacity of 15,900 conventional household air-conditioning heat pumps. .

Waste heat utilization, in addition to thermal energy conversion, heat storage technology is also critical. In this regard, the team developed a phase change heat storage material and system, and directly "go the egg along the way", in the Jiangsu Anbite Fort Energy Group achieved results transformation. “The heat storage device can fully meet the winter heating demand in northern China,” said Wang Ruzhu. The heat storage heating demonstration project has also landed in the Yanqing District Government Building in Beijing, and it can be recycled in less than three years.

In addition, in the industry's difficult point "high-temperature steam heat pump", the team developed a compression-type heat pump technology using twin-screw with intermediate spray cooling, and successfully converted and applied in Hanzhong Precision Machinery Co., Ltd.

At the same time, the enterprises and units that cooperate with the project leader Shanghai Jiaotong University are also growing and developing: Zhuhai Gree Electric Appliance Co., Ltd. has developed 13 international leading technologies related to compression refrigeration and heat pump; Shuangliang Energy Saving System Co., Ltd. was established. The largest lithium bromide central air-conditioning manufacturing base in the Asia-Pacific region; the Institute of Engineering Thermophysics of the Chinese Academy of Sciences built the first 50-kilowatt chemical heat pump prototype in China...

Based on the demonstration project, the network utilization and scale application of industrial waste heat are still under exploration. The “Guidelines for the Utilization of Low-grade Residual Energy Network” compiled by the project team will become the guidance book for the large-scale utilization of industrial waste heat. "In the future, we should comprehensively consider the waste heat source and residual heat conversion technology, and optimize the matching according to the energy requirements and matching criteria according to the needs of users, and form an overall network solution that solves the industrial waste energy, heat, cold and storage. A large amount of energy saving and emission reduction is of great significance.” Wang Ruzhu said, “I hope that our guidebook can provide experience for large-scale application of industrial energy conservation and emission reduction.”