Coal is often regarded as a necessary evil in that it provides the country with most of its power and valuable export earnings. However it has a reputation for being a ‘dirty’ energy source, especially in its handling. If the management if the dust generated during coal handling is looked at creatively, there are opportunities for the use of this plentiful resource, without posing a health risk to workers or inconveniencing people living in the surroundings.

Howden-owned company Engart has developed a cost-effective and efficient coal dust capture and containment system, which can improve workplace health and the lives of communities located near coal-related operations. The Engart surface dust scrubbers are a derivative of the company’s range of scrubbers that are mounted on continuous miners where they have been used to control dust in operations underground.

Waldo van der Merwe, dust scrubber systems manager at the company,  says the surface scrubbers enable coal industry-related operations such as mines, power stations, shipping terminals, and coal train and truck operators to more effectively control the dust generated at critical plant surface loading and unloading points. “Coal dust can, for instance, be a pervasive problem at power stations. However, it is often specific areas such as transfer points where much of this dust is released and where it is unnecessary to install sophisticated engineered systems because the area where the dust is generated is localised,” Van der Merwe adds.

How it works

The Type 46 and Type 36 surface units are capable of handling air volumes of up to 25 m³/s and have the capacity to overcome the resistance of external duct systems. These units are supplied on skids and are consequently easily transported, installed and commissioned. They can also be moved to alternative sites relatively quickly, making them extremely portable.

Dust-laden air is drawn into the dust extractor and mixed with water at the impeller and in the chamber. The mixture of dust, air and water is then drawn around the motor and caught in a steel woven mesh, which is continually washed by a multi-nozzle spray bank.

The dust-free air is exhausted, and the resultant sludge is pumped away for disposal. In the instances of power stations and shipping, this sludge can be returned to the original coal load where, once it is dry, it becomes part of the product transported or burned. Several mechanical safety devices are built into each unit to ensure that they can be used in explosive environments. These include a flame-proof electric motor located out of the air stream and an anti-spark impeller track system.

Application-specific units

Depending on the volume of dust involved, an affordable dust scrubber system can be designed for an individual application in order to effectively control ambient dust during working operations. An audit of the operation by an Engart representative from Howden, in conjunction with the plant engineers, will determine if surface scrubbers are the best option and, if they are, where they can be employed most effectively to control dust. Areas included in the analysis are procurement budgets, and running cost and maintenance priorities – all of which can impact on the selection of an appropriate dust capture and containment technology. In most instances a ducted system connected to a surface dust scrubber unit is highly effective in controlling the coal dust.

Market share

The scrubbers have established themselves as premier dust scrubbers in coal mines and other environments in South Africa where airborne dust is a risk to health and safety. The compact, robust design means it can be adapted relatively easy to surface unit applications where its use in a ducted system requires higher pressures, without impacting on reliability. According to Van der Merwe, the locally designed and manufactured units have been used successfully in the United States (US) before being introduced to the South African market. “In the US our representatives incorporated surface-mounted units into ducted systems to control the dust released at railcar tipping points,” he explains. “In these applications, the units proved to be highly effective in controlling large amounts of dust, in a package that that is energy efficient and requires very little maintenance.” The systems capture up to 99.7% of total dust and 95% of respirable dust, vastly improving the health conditions for those working in these operations.