Measurement and verification experience of compressed Air production at an industrial scale Hydraulic Air Compressor (HAC) NRCan Energy Summit May 30 th , 2018 Dean Millar B.Eng.(Hons), ARSM, PhD, DIC, FIMMM, CEM Bharti School of Engineering, Laurentian University Phone: 705-918-1613 (direct) Email: dmillar@laurentian.ca
Outline • Introduction • Commissioning, Measurement & Verification • Performance tests • Troubleshooting & debugging • Transitioning to commercial scale
The HAC Pack Find out more: www.electrale.com 705-918-1613 dmillar@mirarco.org 9
What does it do? How does it work?
Q. What will be demonstrated? A. Isothermal compressors that are easy to maintain will be cheaper to run 12% 12% Equipment and installation Maintenance Electricity 76% Shaded area = (Minimum) compression work US DOE: OFFICE OF INDUSTRIAL TECHNOLOGIES* https://www.energystar.gov/ia/business/industry/compressed_air1.pdf *50 kW e motor on the compressor, 2 shifts per day, 5 days per week, $0.05/kWh, 10 years
Definition of project success: agreement between modelled and measured HAC performance … 250 cfm 5.0 m (16.4 ft) Target: 73% efficiency Water: 21.9 m 0.400 m 3 /s (71.9 ft) (6300 gpm) Air: 0.115 Sm 3 /s (244 scfm) 2.1 bar(g) (31 psi(g)) Source: Young, S., Hutchison, A., Sengupta, S., Clifford, T., Pavese, V., Noula, C., Myre, M., Vitone, D., Chiasson, J.P., and Millar, D.L., 2015. Conceptual design of a modern-day hydraulic air compressor. ECOS 2015, Pau, France, June 2015.
…but first the demonstrator had to be built November 2016 February 2017 March 2017 June 2017 7
Some technical risk was mitigated through adoption of Charles Taylor’s 1905 design for the air water mixer
Y-piece attached + Larry Mk I Starting up with: Taylor air-water mixing head; forebay tank lid open
Commissioning, Measurement & Verification Simplified P&ID
An efficient HAC needs efficient pumps Freeflow System: Riventa Canada Inc. www.riventa.com
Commissioning operations proved that the measured compression process was close to isothermal… 12 12 10 10 Temperature increase in downcomer (mK) Temperature increase in downcomer (mK) 8 8 6 6 dT - BM38A t 4 4 dT - Pavese at al. dT - BM36A 2 2 dT - Pavese at al. 0 0 0.1 0.1 0.15 0.15 0.2 0.2 0.25 0.25 0.3 0.3 0.35 0.35 0.4 0.4 0.45 0.45 0.5 0.5 Water discharge (m3/s) Water discharge (m3/s) For more info on “nearly isothermal gas compression” see: Pavese, V., Millar, D., Verda, V., 2016. Mechanical efficiency of hydraulic air compressors. ASME J. of Energy Res Tech, (138) / 062005, 11p
… but revealed significant differences between modelled and measured performance 300 80 70 250 60 200 50 Free Air Delivery (Scfm) Efficiency (%) 150 40 30 100 20 BMT34 FAD HAC Mk14 Model FAD 50 10 BMT 34 Eff HAC Mk14 Model Eff 0 0 0.2 0.25 0.3 0.35 0.4 0.45 0.5 Water discharge (m3/s) Source: Millar, D.L. & Muller, E., 2017. Hydraulic Air Compressor demonstrator project. Presentation made at the ACEEE Summer Study on Energy Efficiency in Industry, Denver, August 15-18, 2017
With the Taylor head, the HAC Demonstrator had an efficiency ‘ sweet spot ’ at around 4.0 m of head and 0.225 m 3 /s water flow
A bubble detrainment, water free fall and bubble re-entrainment zone becomes evident from the downcomer pressure profiling measurements Venturi inductor geometry draws air in through manifold Bubbles expand due to lowering of pressure (convergent duct, Bernoulli) Larger bubbles coalesce more readily ~0.9 m Void formed from coalesced bubbles Water jet free falls through the void and accelerates Water jet impacts upon a bubble depleted zone ‘New’ bubbles are re-entrained below impact zone Water velocity now sufficient to transport (drag) bubbles downward HAC compression process starts Bubbles become smaller as water potential energy is lost and pressure increases Void fraction (gas holdup) reduces as bubbles are compressed Flow becomes more ‘water dominated’ Water velocity reduces due to its incompressibility Frequency of bubble interactions (break-up & coalescence) reduce 9
Head loss due to bubble detrainment, free fall and re- entrainment amounted to a ~0.9m head loss across all tests, but brought the measured & predicted performance together 300 300 80 80 75 75 275 275 70 70 250 250 65 65 225 225 60 60 55 55 200 200 Free Air Delivery (Scfm) Free Air Delivery (Scfm) 50 50 Efficiency (%) Efficiency (%) 175 175 45 45 150 150 40 40 35 35 125 125 30 30 100 100 25 25 BM36A & BM38A FAD 75 75 20 20 HAC Mk 14 FAD 15 15 50 50 10 10 BM36A & BM38A Eff (%) 25 25 5 5 HAC Mk 14 Eff (%) 0 0 0 0 0.1 0.1 0.15 0.15 0.2 0.2 0.25 0.25 0.3 0.3 0.35 0.35 0.4 0.4 0.45 0.45 0.5 0.5 Water discharge (m3/s) Water discharge (m3/s)
Detrainment loss depended on the air-water mixing head geometry Forebay water levels with given geometry Geometry tested Removing air manifold for hydrofoil grille test
Fitting the Y-piece in the forebay tank permitted testing of a ‘closed loop’ configuration with an ‘in-line’ air-water mixer From pump 1 Y-piece attached “Larry Mk I” From pump 2
Alex Hutchison’s PhD studies produced an air water mixing head that added ~10% to the Dynamic Earth HAC efficiency (71% against a target of 73%) No manifold (hydrofoil grille). Y Config Y Config + Grill No head 2 pumps. Larry Mk I No head 1 pump. In the best case, the HAC Demonstrator returned 10.9 kW/acfm after all losses are taken into account. This appears impressive, but the HAC Demonstrator delivery pressure is far less than normal service air pressure.
… but bubbles in water with previously dissolved co-solutes can have lower diameter Without co-solute With co-solute Credit: Valeria Pavese
Adding NaCl as a co-solute, increases the water surface tension. This makes bubbles smaller and ‘tougher’; smaller bubbles are dragged to underflow in the HAC separator Some co-solutes increase surface tension Some co-solutes reduce surface tension Graph source: Chaplin, M. 2017. Explanation for the physical anomalies of water. Online: http://www1.lsbu.ac.uk/water/physical_anomalies.html
We are now exploring HAC designs for commercial mine installation … • Energy efficient • Safe • Cooler and drier air • Reliable • Long operating life • Scalable • Same or lower CAPEX www.electrale.com “All the air at half the cost” +1-705-918-1613
Compressed Air and Gas Institute (CAGI) data can be used to compare the performance of conventional, incumbent, compressors, with that of a HAC (using the model checked against HAC Demonstrator data for the latter!) 0.290 CAGI 2 No.TS32SC-400HHAC/150psi 0.270 HAC 4000/150psi Efficiency (kW/acfm) 0.250 0.230 Curve for HAC rises at low flow rates, due to 14kW ventilation fans 0.210 running continuously to ‘dispose of’ compression heat 0.190 0.170 0.150 0 500 1000 1500 2000 2500 3000 3500 4000 4500 FAD (acfm) How much money is saved actually depends on the demand profile, and whether the machines have been sized properly to meet this demand, but the flatter turn down curve of the HAC, should offer advantage
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