Green Engineering
Hydraulic motion control could enable massive energy savings in supercritical CO2-driven rock
pulverization Rick Meyerhoefer
• Delta Computer Systems
Roughly 3% of the world’s generated electricity is consumed in the mining process of breaking down rocks. In Canada alone, mines consume more than 150 petajoules annually. For perspective, 1 petajoule can power the city of Calgary for three weeks, so any significant drop in mining energy requirements could have vastly beneficial consequences, both in cost and environmental impact. Natural Resources Canada figured the problem was worth exploring and announced the Impact Canada Crush It! Challenge, urging applicants to develop “a new clean technology solution that transforms how energy is used for crushing and grinding rocks in the mining industry.” Cliff Edwards of Envisioning Labs has what he thinks is a winning idea; using high-pressure and temperature control to pulverize rock with supercritical CO2. 10
June 2021
Green.Engineering 6-21.Vs2.LL.indd 10
The core idea is that breaking rocks through compression is hard; breaking them with tension is far easier. Think about the difference in effort between squeezing a sealed soda can until it bursts compared to simply putting it in the eezer. The U.S. Bureau of Mines had experimented with rock comminution (breaking something down into smaller particles) through steam flashing in the 1930s. Like so many other approaches, though, this may have been discarded because the energy required for the process was too great relative to the results. But Edwards wondered if another fluid might be amenable to a lower-energy approach. CO2 seemed like a strong contender. At a relatively easyto-achieve 74 bar and 31° C, the substance transitions om
www.designworldonline.com
DESIGN WORLD
6/4/21 11:40 AM