Japan firm completes 'world's first' CO2-based soil freezing project

Showcasing the potential for natural refrigerant technology in an increasing variety of applications, Japan's Chemical Grouting Co., Ltd. details the successful application of CO2-based soil freezing for an underground tunnel construction project last year.

By switching from traditional R22-based systems to Mayekawa's NH₃/CO₂ industrial refrigeration system, Chemical Grouting was able to achieve 40% savings in energy consumption.

Reducing environmental impact

Chemical Grouting performs construction projects across Japan, mainly in the areas of buildings, dams, slopes and soil cleansing and decontamination.

This particular project dealt with soil freezing during the construction of an underground tunnel in a metropolitan area in Japan.

"[For soil freezing,] HCFC refrigerants have been used so far," said Yuta Shioya, researcher for engineering systems development for Chemical Grouting, during the ATMOsphere Japan 2018 conference held in Tokyo, Japan on 13 February.

"However, by 2020 we will see the end of the manufacturing of these refrigerants. In addition, the alternative to HCFCs, which are HFCs, due to their high GWP, will also most likely be banned in the near future," he explained.

"This is why we have decided to use natural refrigerants, in order to reduce the environmental impact."

The project began in January 2017 and was completed in March 2017.

One of the biggest benefits the company saw by using the NH₃/CO₂ system, Shioya explained, was the reduction of their project working period by 40% (39 days).

The system’s compact size greatly simplified the disassembly and removal process.

Improved performance ranked among the other benefits.

"Due to the high efficiency of CO₂ and its low viscosity, the new method is able to freeze the soil more quickly and at lower temperatures," explained Shioya.

"In addition, the piping used is more compact and lightweight."

Mayekawa's NH₃/CO₂ system, which was used for this project, is one of the firm’s most popular systems. It is used in cold storage, logistics, and food processing facilities, and there are currently 1,495 installations worldwide.

Correction: A previous version of this article stated that it is the world’s first NatRef-based soil freezing project. That is not correct. It is the world’s first CO2-based soil freezing project.