Diesel designs cut health risk

Excerpts from a story first published in the CSIRO’s Earthmatters magazine:
http://www.csiro.au/resources/earthmatters.html

According to a report released by the Australian Coal Association Research Program (ACARP) “the significant introduction of diesel engines in underground mining plant since the 1960s has created a hazard in terms of suspended particulates”.
“The extent of this hazard is indicated by NIOSH [National Institute for Occupational Health & Safety in the United States] where exposure levels of diesel emissions were shown to be significantly higher for underground miners than for other occupations,” the report said.
This report covers the ACARP C15021 research project into using acoustic agglomeration techniques to reduce diesel particulates from coal mine vehicle exhaust by 92 per cent.
According to a Project Leader with CSIRO’s Exploration & Mining Division, Dr Patrick Glynn, “despite the expected improvements in emission performance by new diesel fuel, end-of pipe emission control may still be required to fully satisfy OHS&E expectations and future regulation”.
Dr Glynn said the goal of the ACARP project was to achieve “a high removal of 2.5 μm (PM 2.5) particulate material from the exhaust stream”.
“These particles have a propensity to be held in suspension and will only settle by inertial (gravity) means very slowly.
“The ultrasonic agglomeration method of removal increases the mass of the diesel particulate particles using ultrasonic agglomeration where a sonic probegenerated sound wave is tuned to increase the energy in a small particle such that it is attracted to other diesel particles.
This increases the overall mass of the agglomerated particle, allowing it to be removed by a ‘cyclone’ using exhaust stream velocity.”
This cyclonic filtration method is similar to the one used in modern vacuum cleaners: the dust-laden air in the outer walls of the cyclone swirls downwards and at the base of the vortex begins to swirl upwards, up the inside of the vortex. The vast majority of the debris separates from the air stream as air reaches the bottom of the swirl, and is deposited in the dirt container. Only a small fraction remains in the air and can be removed by a secondary, cartridge-type filter.

Testing positive
The tests were conducted at the Control Technologies International Ltd laboratory at Archerfield, Queensland, on a water brake dynamometer and were split into four stages including bench-testing a diesel engine to measure diesel particulate emissions over the RPM (revolutions per minute) spectrum, and building an electrostatic diesel exhaust filter and two prototype diesel exhaust scrubber ultrasonic filters which were fitted to a mine vehicle for a 3-month test period.
The tests also involved correlating the fundamental mass-over-time measurement used in this ACARP project with those from a NIOSH diesel particulate exposure-measuring instrument. This was done to measure diesel particulate loading in real time and the testing was to verify the effectiveness of this instrument against gravimetric (or fundamental) measurement.
The results have been of significant value to scientists working to improve occupational health and safety for mine workers.
“The reduction of 92 per cent in diesel exhaust particulate achieved by this project is remarkable because there is very little backpressure on the exhaust system that would, using normal micron filters, cause reduced engine output,” said Dr Glynn.
“The outcome of the project at 92 per cent particulate reduction came close to the 95 per cent particulate reduction aimed for at the beginning of the project.”
Since its report was submitted the research team has been awarded a second grant for a triple-chamber acoustic agglomerator that will remove up to 99 per cent of diesel particulates. This project is now underway.

For more information contact: Dr Patrick Glynn on tel: +61 7 3327 4636 or email: patrick.glynn@csiro.au

This article was first published in Earthmatters, the official magazine of CSIRO's Exploration & Mining Division - www.csiro.au/resources/earthmatters.html