SME Annual Meeting Feb. 23 - 26, 2014, Salt Lake City, UT 1 Copyright © 2014 by SME Preprint 14-143 FAN REQUIREMENTS IN THE SECOND 100 YEARS OF A MINE LIFE A. Haghighat, Missouri Univ. of Science and Tech., Rolla, MO A. D. S. Gillies, Missouri Univ. of Science and Tech., Rolla, MO ABSTRACT The Missouri University of Science and Technology’s (Missouri S&T) Experimental Mine is a teaching and research facility which has been excavated in limestone by mining engineering students over almost 100 years. The mine is currently being extended to a second level. Available fans for ventilation are two surface fans of 24 kW and two underground booster fans of 12 kW. The design of a ventilation network in conjunction with multi surface fans and booster fans entails a complex procedure. Ventsim Visual software modeling has been used for network analysis to determine the optimum surface and booster fans locations, blade settings, and speeds. Both natural and mechanical induced ventilation pressures have been taken into account. Three working faces on each level have been designated as target points that minimum air quantities are required. The model has been calibrated against a pressure and quantity survey. Design of ductwork, door/stopping positions and different fans characteristics have been examined. The optimum flow rate at identified working faces, efficiency and minimum energy losses and annual network power cost determine the best scenario. The optimum design has been determined for the ventilation network for the next 100 years. The optimum flow rate across working faces is the key criterion selected. INTRODUCTION Multiple operating points of mine fans are a problem that fan and mining engineers must constantly be aware of in mine/fan systems. In a single fan system, unstable conditions can be avoided by restricting fan operation to the “normal operating range.” Unstable oscillating behavior of an axial-flow fan assuming a properly manufactured and installed fan can normally be attributed to the multiple operating points that exist under the given ventilation system configuration. Eck (1973) provided the following explanation for the resulting condition: If these [multiple operating] points are close together [in terms of fan pressures and air quantities], which often happens, then even small pressure fluctuations might initiate oscillation [between operating points]. Once oscillation has been initiated for whatever reason, additional uncontrollable displacements of the characteristic will occur due to the continuous accelerations and delays [pulsing] of the individual air columns. To prevent this, care must be taken that the operating point is at same distance from the critical range (Y. J. Wang, Mutmansky, & Hartman, 1988). The system operating point in ventilation systems with a single main fan is defined by the intersection of the mine impedance curve, based on Atkinson’s equation, the fan characteristic curve. As mining progresses the total resistance is increased and the mine characteristic curve becomes steeper. The operating point then moves up the fan curve, reducing the total air quantity available and increasing the system pressure. A study has been carried on to improve the ventilation network model of the Missouri University of Science and Technology Experimental Mine that based on use of Ventsim Visual ventilation software. Numerous parameters such as efficiency, air quantity, total pressure, density and temperature have been considered to select the most appropriate surface and booster fans. Five simulation scenarios have been employed in order to maximize the network efficiency and air flow quantity in three working faces and minimize the annual network power cost. Different locations for surface fan(s), and booster fan(s) at different blades’ angle have been examined in (series/parallel) arrangements. Pressure quantity leap frog surveys have been used to acquire the performance specification of the mine. The main fan selection has been carried out according to the mine performance specification and fans characteristic. The present ventilation network has been made a basic for ventilation network optimization. MISSOURI S&T EXPERIMENTAL MINE The Experimental Mine is an underground limestone mine located in Rolla, Missouri. The mine is accessed by two adit portals, has three raises to the surface and two primary ventilation shaft. The two mine portals both have ventilation doors (Figure 1). Figure 1. The Missouri S&T Experimental Mine portals. Current ventilation network The 1.2-m diameter Joy axial vane fan with 30 KW kW motor has been installed to exhausting blowing approximately 23.6 m 3 /s of airflow at 1,000 Pa of static pressure to the underground workings. Two Spendrup booster fans have been installed in underground in series connection to the surface fan. Each booster fan is driven by a 12 KW three phase 460V motor that will load the circuit by approximately 20A. Booster fans have been mounted on skids to facilitate transportation. Locations of booster fans can be altered to optimize a particular ventilation network. A variable frequency drive (VFD) has been installed at each fan. The VFD’s have been set up in separate boxes next to the switch boxes (Figure 2). Booster fans are of vane axial deign andhave adjustable blade angles.