The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Fog Removal in the Declines of Underground Mines in Sub-Arctic Regions

Anu Martikainen

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Civil and Environmental Engineering for public examination and debate in Auditorium V1 at Helsinki University of Technology (Espoo, Finland) on the 1st of June, 2007, at 12 noon.

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Dissertation is also available in print (ISBN 978-951-22-8777-2)

Abstract

Fogging is a common safety hazard observed especially in the declines of underground mines located in sub-arctic regions. Fog forms when saturated air loses internal energy by mixing with a colder air stream, by simply ascending through the ventilation system of the mine, or when contact with cold wall-rock decreases air temperature.

Studies concerning fogging in underground mines are rare. Technological advances and more complete theoretical knowledge gained by research in many other fields offer possibilities for thorough fogging research in mines. This research aims to better understand underground fog formation, related parameters, characteristics, and fog behaviour.

Interviews, literature review, psychrometric and particle concentration measurements, on-site field tests of the existing fog removal methods, and developing and testing a new fog removal approach are used as research methods. The interviews show that there are methods not mentioned in the literature that are used for fog removal in mines. Case studies provide fascinating insight into fogging problems and how to solve them. From literature review the complicated behaviour of fog is uncovered, and the role of visibility, optical attenuation, and droplet size distribution studies are evaluated. Ideas concerning further research are presented according to the findings.

Basic study results demonstrate the situation in declines of three underground mines; Pyhäsalmi Mine, Orivesi Mine, and Louhi Mine in Finland. Studies concerning increasing air velocity show that the value suggested by literature to be high enough for fog dispersal, 0.25 m/s, is not nearly enough in the declines of these mines. Installing an additional fan, showed that the change in relative humidity and thus fog thickness was based on the quantity of heat the fan added to the air. Heating decreased fog thickness noticeably. Only local fog removal was observed for both methods.

Trials concerning new method development gave mainly positive results. The method is based on the water gathering effect of a net set perpendicular to the airflow. The frame and mesh installation are presented. Seven out of eight tested mesh materials resulted in a decrease of relative humidity and particle concentration. Twelve tests were completed, of which two were material combination tests. Unfortunately only two tests resulted in a noticeable decrease of fog thickness and even in these cases the efficiency was not enough for complete fog removal. The best results were received with aluminium net and a mist eliminator/fibrous filter fabric combination.

This thesis consists of an overview and of the following 6 publications:

  1. Martikainen, A. L., 2005, Comparative evaluation of fogging phenomenon in the ramp of three mines in Finland, Proceedings of the 8th International Mine Ventilation Congress, July 6-8 2005, AusIMM, Burwood, Australia, pp: 103-110. © 2005 Australasian Institute of Mining and Metallurgy (AusIMM). By permission.
  2. Martikainen, A. L., 2006, Alternative fog removal methods in mine ramps, Proceedings of the 11th US/North American Mine Ventilation Symposium, Mutmansky, J. and Ramani, R., eds., June 5-7 2006, Taylor & Francis Group plc, London, U.K., pp: 295-300. © 2006 Taylor & Francis. By permission.
  3. Martikainen, A. L., 2007, Fog mesh as an alternative fog removal method in mine ramps, 2006 Transactions of the Society for Mining, Metallurgy, and Exploration, Inc., January 2007, Volume 320, pp: 38-44. © 2007 Society for Mining, Metallurgy, and Exploration (SME). By permission.
  4. Martikainen, A. L., 2007, Fog mesh studies for fog removal, Proceedings of the 2007 SME Annual Meeting & Exhibit and 109th National Western Mining Conference, February 25-28 2007, Denver, Colorado, 4 pp. © 2007 Society for Mining, Metallurgy, and Exploration (SME). By permission.
  5. Martikainen, A. L. and Marks, J., 2007, Fogging in mines: The role of visibility, unfamiliar fog removal methods, and future research ideas, Journal of the Mine Ventilation Society of South Africa, Q2, 7 pp. © 2007 Mine Ventilation Society of South Africa (MVSSA). By permission.
  6. Martikainen, A. L., 2007, Fog removal with a fog mesh – mist eliminators and multiple mesh systems, International Journal of Mining, Reclamation and Environment, vol. 21, no. 3, 14 pp. © 2007 Taylor & Francis. By permission.

Keywords: mine ventilation, fog formation, fog removal, visibility, psychrometric, particle concentration

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© 2007 Helsinki University of Technology

Last update 2011-05-26