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Simulating Air Absorption in a Hydraulic Air Compressor (HAC)

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Simulating Air Absorption in a Hydraulic Air Compressor (HAC) Simulating air absorption in a hydraulic air compressor (HAC) by Stephen M. Young A thesis submitted in partial fulfillment of the requirements for the degree of Master of Applied Science (MASc) in Natural Resources Engineering The Faculty of Graduate Studies Laurentian University Sudbury, Ontario, Canada ©Stephen Young, 2017 THESIS DEFENCE COMMITTEE/COMITÉ DE SOUTENANCE DE THÈSE Laurentian Université/Université Laurentienne Faculty of Graduate Studies/Faculté des études supérieures Title of Thesis Titre de la thèse Simulating air absorption in a hydraulic air compressor (HAC) Name of Candidate Nom du candidat Young, Stephen Degree Diplôme Master of Applied Science Department/Program Date of Defence Département/Programme MASc. Natural Resources Engineering Date de la soutenance March 3, 2017 APPROVED/APPROUVÉ Thesis Examiners/Examinateurs de thèse: Dr. Dean Millar (Supervisor/Directeur(trice) de thèse) Dr. Kim Trapani (Committee member/Membre du comité) Dr. Ramesh Subramanian (Committee member/Membre du comité) Approved for the Faculty of Graduate Studies Approuvé pour la Faculté des études supérieures Dr. David Lesbarrères Monsieur David Lesbarrères Dr. Graeme Norval Dean, Faculty of Graduate Studies (External Examiner/Examinateur externe) Doyen, Faculté des études supérieures Dr. Wilson Pascheto (External Examiner/Examinateur externe) ACCESSIBILITY CLAUSE AND PERMISSION TO USE I, Stephen Young, hereby grant to Laurentian University and/or its agents the non-exclusive license to archive and make accessible my thesis, dissertation, or project report in whole or in part in all forms of media, now or for the duration of my copyright ownership. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also reserve the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. I further agree that permission for copying of this thesis in any manner, in whole or in part, for scholarly purposes may be granted by the professor or professors who supervised my thesis work or, in their absence, by the Head of the Department in which my thesis work was done. It is understood that any copying or publication or use of this thesis or parts thereof for financial gain shall not be allowed without my written permission. It is also understood that this copy is being made available in this form by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. ii Abstract A hydraulic air compressor (HAC) is a no moving parts compressor that uses hydropower to compress air that is inducted through a Venturi effect. The solubility of gases in water increases with pressure and provides a means for the dissolved gas to bypass the air-water separator and reduce the compressed air yield of a HAC. The model developed and fully described herein extends the approach of Chen and Rice (1983) to allow for a multiplicity of gas mixtures, predicts the compressed air yield reduction from gas solubility, and predicts the compressed air yield improvement by increasing the liquid temperature and the presence of pre-dissolved salts. The model simulated multiple scenarios that adjust the parameters that are known to affect air absorption in the downcomer and returns results consistent with the expected behaviour in each scenario. One of such scenarios was the simulation of the downcomer of the Ragged Chutes HAC installation. The results were compared with the single data point of oxygen concentration in compressed air delivered by a HAC and results from an equilibrium solubility model available in the literature. Under the same conditions, the model described herein predicts a concentration of oxygen of 0.181 mol/mol, a value that is 2.3% higher than the equilibrium condition. In order to match the results of the equilibrium model, the mass diffusivities of nitrogen, oxygen, argon and carbon dioxide needed to be artificially increased from their reported values in the literature by a factor of 2000. This suggests that the solubility kinetics are important to consider in the design of a HAC when predicting the compressed air yield but if the equilibrium assumption is adopted the estimate of compressed air yield will be conservative. Keywords: hydraulic air compressors, isothermal compression, air absorption, interphase mass transfer, solubility kinetics iii Acknowledgments I would like to thank Dean Millar for his guidance through my research, the committee members Kim Trapani, Ramesh Subramanian, Graeme Norval and Wilson Pascheto, the Ultra Deep Mine Network for funding my research, my colleagues in the HAC Demonstration Project, my colleagues at MIRARCO and the Bharti School of Engineering at Laurentian University for your assistance with my research. iv Table of Contents Thesis Defense Committee ............................................................................................................. ii Abstract .......................................................................................................................................... iii Acknowledgments.......................................................................................................................... iv Table of Contents ............................................................................................................................ v List of Figures ............................................................................................................................... vii List of Tables ................................................................................................................................. ix List of Appendices ......................................................................................................................... xi Nomenclature ................................................................................................................................ xii Greek Letters ............................................................................................................................ xiv Subscripts .................................................................................................................................. xv Chapter 1 ......................................................................................................................................... 1 1. Introduction ............................................................................................................................. 1 1.1 Hydraulic air compressors (HACs) .................................................................................. 1 1.2 The minimum work compression process ........................................................................ 8 1.3 The effect of solubility on the performance of a HAC .................................................. 11 1.4 Research objectives ........................................................................................................ 13 1.5 Thesis overview.............................................................................................................. 14 Chapter 2 ....................................................................................................................................... 15 2. Literature Review .................................................................................................................. 15 2.1 HACs .............................................................................................................................. 17 2.1.1 Modeling the performance of a hydraulic air compressor ...................................... 18 2.2 Two-phase flow hydrodynamics .................................................................................... 20 2.2.1 Flow regime ............................................................................................................ 20 2.2.2 Bubble size distribution .......................................................................................... 26 2.2.3 Drag......................................................................................................................... 34 2.2.4 Volume fraction ...................................................................................................... 36 2.3 Gas absorption rate ......................................................................................................... 37 2.3.1 Diffusivity of gases in liquids ................................................................................. 40 2.3.2 Gas solubility .......................................................................................................... 45 2.3.3 Psychrometry .......................................................................................................... 52 2.4 Gas-liquid separators ...................................................................................................... 54 2.5 Summary ........................................................................................................................ 59 Chapter 3 ....................................................................................................................................... 61 3. HAC modeling methodology................................................................................................. 61 3.1 Mixing ...........................................................................................................................
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