TRANSCRITICAL CO2 PULVERIZATION
At the core of the proposal is the fact that breaking rock by expansion within is a lower energy process than crushing or impact from outside, since rock tensile strength is significantly lower than rock compressive strength. Given reports that blasting is about 3x more energy efficient than crushing and grinding, we surmise that tensile rock breakage could offer significant energy reduction over compressive crushing and grinding. The challenge in this approach is to find an effective low energy and low cost way to create the expansive shattering force within the rock, without consuming a lot of material like is done in chemical explosives blasting. We propose addressing this by compressing a gas to supercritical conditions, and cycling it back and forth across the transcritical region using energy recovery in the compression and expansion cycle.
How Does It Work?
24% in energy savings (calculated 10.5 kWh/tonne assuming limestone and based on traditional rock crushing and grinding at 13.86 kWh/tonne)
Expected to result in vastly lower steel wear and use - potentially cutting the operational cost of steel replacement close to zero.
The CO2 used can be captured from another process, or even pulled from the atmosphere (direct air capture) thus helping with carbon sequestration.
No water use and no dust produced.
Lower emissions from lower energy use, and lower impact from embodied emissions in steel used. Renewable energy could power the capture process.
Proof of Concept
National Resources Canada “Crushing It” Challenge (semi-finalist) [link]