IAN FRASER Inhaled coal dust is a serious health hazard and, in addition, an atmosphere loaded with coal dust can catch fire or even explode
When used in coal mining and materials handling processes, inertial spin filter technology for industrial dust separation can help eliminate the risk of coal-dust explosions and fires and create a safer working environment for mining company personnel, says Pretoria-based specialised engineering solutions company Rand Technical Services (RTS) chairperson Ian Fraser.
A high-efficiency application of cyclone technology, the spin filter units manufactured and installed by RTS use specialised cyclone technology to induce air flow to spin through fixed vanes at the entry to the vortexes. Centrifugal force then drives the dirt particles to the outside of the vortex, from where the dirt-laden air is purged through an annular port at the end of the vortex tube. A purge fan keeps the dirt-laden waste air in flight, from where it is either dispersed or collected as required, with clean air exiting the process.
Fraser says that RTS spin filters can remove 98% of particles 15 μm and larger through this simple process.
“This high-efficiency, maintenance-free cyclone technology replaces conventional dust and exhaust filters,” he says.
Fraser explains that coal dust is not only intrusive but also electrically conductive. “If this dust gets into electrical switchgear and control systems, it can cause serious failures, resulting in expensive stoppages and plant downtime,” he says.
Fraser notes that health and safety always need to be considered with any industrial operation. “Inhaled coal dust is a serious health hazard and, in addition, an atmosphere loaded with coal dust can catch fire or even explode,” he says.
Current industrial filtration methods often require costly maintenance and filter membrane replacement on an ongoing basis, notes Fraser.
“We have supplied several small spin-filter installations to coal mines for cleaning the air above and below ground. We are currently engaged in a larger project to collect and sequestrate coal dust from a large steam plant in Sasolburg,” he says.
Consistent Performance
Fraser says that unlike conventional filter membranes that clog because of pressure build-up after a period of use, there is no drop in pressure with spin filter modules.
“The units are self-cleaning, and do not clog when correctly installed, thereby offering consistent performance. They are highly energy efficient too, as the pressure through the spin filter is constant and does not increase as dust is removed,” he says, adding that no special maintenance is required. However, regular inspection is necessary to ensure that the main and purge fans are running correctly.
“Not only is pressure constant for the life of the unit but it also has an exceptionally long working life,” says Fraser, adding that RTS has units, installed more than 23 years ago, which are still operating. “The sturdy, high-density polypropylene construction of the blocks is highly resistant to erosion,” he notes.
RTS has installed several spin filters in mining and industrial applications, including at control rooms, transformer rooms, machinery spaces and workshops, among others. “This technology has also proven to be effective in the cooling of variable-speed drive installations,” notes Fraser.
Unlimited Capacity
Fraser says the spin filters are constructed in modules that can be built up into large panels, sized to match required air flow and offering an unlimited capacity on engineered systems. The smallest available unit, containing one inertial spin filter module, easily handles 1 200 Nm3/h to 2 500 Nm3/h, with upper-range capacity determined only by the application and available space.
“In applications requiring secondary filters to remove finer particles, such as in air-compressor intakes, the spin filters substantially extend the life of the secondary filters,” he notes, adding that conventional filter membranes are left with very low dust loadings and, therefore, last longer.
He says there is a beneficial ripple effect on cost savings throughout the plant when downtime from planned and unplanned shutdowns is greatly reduced, as less damaging friction from dust particles results in less wear and tear and, therefore, fewer equipment failures.