March/April 2013

Air supply on demand

New ventilation technology provides airflow when and where it is needed

By Krystyna Lagowski

The development team at Goldcorp’s Éléonore project install ventilation conducts along the exploration ramp. Airflow at the mine relies on an automated ventilation system furnished by SimSmart | Courtesy of Goldcorp

Many existing mine ventilation systems are often based on a “set and forget” mentality – a mine will set its systems for maximum airflow and keep them that way throughout the day. It is assumed that if air needs to be provided somewhere, it needs to be there all the time. But why provide air to areas that are not being actively used? Why not introduce a system that makes it possible to shut off airflow and move it somewhere else in a timely fashion?

Saving energy and even boosting productivity are the goals of automated ventilation. “Ventilation on demand (VOD) is the ability to have the right amount of air where you need it, when you need it,” says Cheryl Allen, principal engineer, ventilation, mines technical support at Vale. “You use automated systems to deliver VOD – we speak of the two simultaneously.”

“With the older systems, we’d have to get a crew, we’d have to maybe build a bulkhead, maybe move heavy boards to change airflow in and out of regulators,” explains Allen. “The older systems can’t react quickly enough.”

VOD, with fan and louver controls responding to data relayed from underground, directs the required volume of air to the places in the mine where it is needed. Automated ventilation’s inherently quicker reaction times and greater flexibility make a compelling business case to decrease energy costs where production is not possible, while increasing production where possible, says Andrew Dasys, president of the data analysis consultancy, Objectivity. During a 31-day case study done in concert with the Centre for Excellence in Mining Innovation (CEMI) to model the VOD business case, Dasys says, changing air only once per shift and redistributing unused air from two operating levels provided a potential production increase of a quarter to half a million dollars, by allowing an additional scoop tram to operate.

Sudbury-based CEMI has ongoing partnerships with operations to advance the understanding of VOD in Canada. The next phase of CEMI’s VOD project is to determine how mines can increase production potential using VOD.

Communication is critical

One of the keys to optimizing airflow is an effective mine-wide communications system, says George Hughes, research and development program director at CEMI. “That system has to control at least three components – the variable frequency drive fan system, auxiliary fan operation and some way of opening and closing regulators,” he says. The system Hughes describes is in place at Xstrata’s Nickel Rim mine. The network there enables individuals to access the Internet while underground. It also has a mobile and stationary array of air quality sensors, and radio frequency identification system (RFID), to track where people and vehicles are throughout the mine.

To exploit these tools, the mine uses a proprietary three-dimensional (3D)-modelling and simulation software from SimSmart technology to optimize airflow in the mine. “You can create a 3D model, connect it in real-time to sensors and fans, and control your network from that model,” says Sarah Perno, director of sales at SimSmart.

The software, known as SmartEXEC, gives mine operators the power to control ventilation using a range of options which can include physical measurement or mass-flow balance that calibrates the best airflow for a specific area based on depth, temperature, air quality and demand. Using mass-flow balance control, the actual VOD flow can be compared to an ideal model value and then adjusted to provide maximum energy savings. While in the development stage, a mine can design, test and validate the implemented ventilation system to ensure it meets all health, safety and operational requirements.

The VOD system at Nickel Rim also has instruments mounted on the mobile fleet, which measure air quality and air quantity, in addition to instruments at fixed locations in the mine. The ­SimSmart software is also employed at Goldcorp’s Éléonore development in Quebec.

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