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This Week in Research – What the heck is the HAC? Innovative Research Project that is changing the Sudbury landscape

Innovative Research Project that is changing the Sudbury landscape


On Wednesday, June 21st, at Dynamic Earth, Laurentian University, MIRARCO and the Ultra-Deep Mining Network (UDMN), will be celebrating the official completion and operationalization of the Hydraulic Air Compressor (HAC) Demonstrator, a new technology that will dramatically alter, both literally and figuratively, Sudbury’s research landscape. The official opening event will run from 4:00 p.m. -6:00 p.m. during which time guests will have the opportunity to meet the HAQ team, partners and sponsors for the grand opening, have a guided tour of the HAC, eat BBQ food and listen to a special briefing in the Atlas Copco theatre from Dr. Miller, entitled: What the heck is the HAC? 


The Office of Research Services had the privilege of speaking with the project’s team leader, Dr. Dean Millar, Professor of Engineering at Laurentian University, about his innovative technology ahead of Wednesday’s event. 


Q: 1. Provide a brief description of the technology, project team, funders.
A: Whether it  for pneumatic power, refrigeration, distribution and transmission or liquefaction, gas compression is an energy intensive and expensive process. There is no publically promoted market gap or need. As a basic necessity in industrial processes and a part of the fundamental quality of life for Canadians, the gases just simply need to be compressed, and are compressed with conventional compressor technologies. Currently, organizations running compressors simply pay whatever it costs.


Hydraulic Air Compressors (HACs) produce compressed air through the action of water falling through a large difference in elevation so that the water pressure is transmitted to the millions of bubbles of air entrained by the water flow that, in turn, become compressed. The key point about the process is that the compressing water simultaneously cools the gas as it is being compressed, to deliver a practical ‘nearly’ isothermal gas compression. An isothermal compression process is the most energy efficient gas compression process conceivable; incumbent compressor technologies are measured against an inferior ideal: an isentropic process, which despite being an ideal will nevertheless will involve the consumption of more energy for the same amount of compressed gas produced. Some ideals are less ideal than others.


Other advantages of the compressed air produced by a HAC are that it is oil-free, typically drier and definitely cooler than compressed air produced by most incumbent industrial stationary compressor technologies. However, for the 18 or so historical HAC installations, there was one important Achilles Heel of the systems: because the air and the water are in intimate contact, and because the solubility of a gas increases with the increase of pressure, in a HAC, some of the gas being compressed can be dissolved in the water and lost. The modern twist on HACs that will be explored at the HAC Demonstrator at Dynamic Earth is that it is known that the solubility of gases in water reduces when there is already a solute –mostly an electrolyte- dissolved in it. Gas solubility also decreases with increasing temperature too. Both of the latter phenomena will be exploited in this project to overcome the depressed gas yields experienced by the historical HACs. The overall effect will be to substantially expand the applicability of HACs in modern gas compression tasks, and completely revive their commercial relevance in a modern context.


Q: 2. Describe the involvement of Science North and Dynamic Earth in the development of this project.
The technology and work program of investigations at Dynamic Earth embrace many areas of engineering science: physics and chemistry generally, drawing upon the areas of thermodynamics, two phase fluid flow, aqueous chemistry and bubble physics specifically. The facility also features some state-of-the-art mensuration technology. The principles of mensuration governing flow and depth metering at Dynamic Earth HAC range from: Coriolis forces, magnetic forces, sonic propagation and Doppler effects, wave guided radar wave propagation, to name a few. Chemical analysis of the compressed gases is by means of a 40 channel real-time mass spectrometer gas analyzer. 


So the site is rich in practical science. For Dynamic Earth and Science North, the attraction of collaborating is that this science is happening ‘live’ on their site and so it affords a tremendous opportunity to contribute to the public understanding of science and engineering. As part of their duties, the “HAC Pack”, the team of engineers and scientists charged with operating the facility and executing the program of investigations, will hold some responsibility for relaying their understanding of the scientific principles that underpin the HAC’s processes to the general public visiting Dynamic Earth’s exhibits. The team will be able to relay first hand how the scientific principles have been manipulated and optimized by the engineers to bring about specific system behaviours, to meet the particular objective of energy efficient gas compression. In essence, the HAC Demonstrator will act as a non-virtual classroom of engineering science, for visitors to Dynamic Earth.


Q: 3. Describe the importance and potential impacts of this technology.
A: Ultimately the objective for the facility is to show how any organization that absolutely needs to compress gas, can do so for less energy, lower cost and fewer CO2 emissions. The predictions of how much electricity might be saved start at 13%. This may not sound like much. However, compressed air systems use 10% of the total industrial energy use in exemplar jurisdictions across 4 continents: the European Union, the US, South Africa and both Malaysia and China. Consequently, the HAC Demonstrator project at Dynamic Earth addresses a market corresponding to 10% of all the industrial energy consumed around the world, and aims to reduce this to 9% at most.


Q: 4. How will this technology change the research landscape at Laurentian and in Sudbury?
A: To date, the HAC Demonstrator has involved a deep applied research collaboration between the academic and industrial partners that have contributed to its creation. The technology has, and always had, a natural synergy with the mining industry because of the high vertical extent of the systems. For the demonstrator, the plan is, through applied research, to bring this CleanTech to the Ontario mining industry to help lower their energy costs, maintain the Ontario mining industry’s competitiveness on the world stage, and to protect mining jobs in Ontario.


Q: 5. How will the technology be commercialized?
A: The Dynamic Earth HAC is a 21st Century twist on a 19th/20th Century technology. The historical spiritual home of this CleanTech will always be Northern Ontario and the 100 year old Ragged Chutes HAC near Cobalt. The team aspires to not only meet the needs of the Ontario mining industry; we aspire to exporting modern HAC technology all the way around the World and to deploying it in multiple industrial sectors. In showing what they can do in conceiving, designing, developing and constructing the Dynamic Earth HAC Demonstrator, the Sudbury-based consortium of innovators, engineers and suppliers, have made sure the technology's modern spiritual home will remain in Northern Ontario.


Q: 6. Describe how researchers from other disciplines might use this technology
A: Beyond establishing effectiveness during the initial investigation process, and the enhancements expected using co-solute and temperature interventions, the next phase of investigations will concentrate on use of HACs as energy efficient, continuous pressure-swing-absorption systems for carbon capture from flue gases arising from the combustion of fossil fuels. This program of work has already attracted approaches from researchers from around the world who have expressed an interest in running their own experiments on the HAC Demonstrator, concurrent with our own. This is just one example of how researchers from other disciplines might use the technology, but the potential for extensions of the research program are numerous. The flow conditions expected in HACs are expected to be mildly acidic, with elevated dissolved oxygen, fluid flow velocities ‘off the chart’ in comparison to what is conventionally deemed acceptable, of elevated temperature and, the water will be salty! The situation described is a ‘perfect storm’ for corrosion, that the engineers have dealt with using judicious selection of materials, special corrosion resistance linings and equipment specially designed for ‘salt-service’. Expressed another way, the HAC Demonstrator represents state-of-the-art research infrastructure for corrosion science, and we expect approaches from academics with this specialization when they learn of the facility. Other areas of engineering science where the HAC Demonstrator may be able to support research efforts include: pisciculture, environmental remediation of acid mine drainage, pressure acid leach processes, advanced industrial refrigeration systems and snowmaking, to name just a few.