Controlling coal dust in conveyor systems and transfer points is not just an issue of health and safety, but also has a significant impact on operational efficiency and cost of ownership. Transfer points are often the main source of coal dust generation, but process plant owners often overlook the potential to optimize the design and positioning of transfer chutes. While dust suppression and extraction systems are widely used, they can only manage so much, says Alwin Nienaber, Technical Director of South Africa's Weba Chute Systems.
A more effective approach is to first focus on the engineering of the chutes, which can alleviate 50 to 80% of the dust problem. Then, the suppression and extraction of the remaining dust can become a more efficient part of a comprehensive solution. As health and safety regulations become more stringent, it is expected that facilities will face increased pressure to address dust issues. Coal dust is not only a health risk but also a hazard for spontaneous combustion in the coal sector.
Excessive dust not only poses a risk to employees and contractors but also to the surrounding communities. It also affects operational efficiency and continuity as certain areas may be off-limits when conveyors are running. This makes it difficult to check and maintain critical conveyor equipment and machinery until the system is shut down and the dust settles. The presence of dust also means that equipment and machinery require regular cleaning and increases the cost of maintenance.
To control dust, an understanding of material flow and the impact of uncontrolled velocity is crucial, says Nienaber. By controlling the flow of material, it can be consolidated into a homogenous stream, reducing dust dispersal. This is not always easy, as natural segregation in coal on a conveyor can cause fine material to separate and quickly aerate, leading to dust generation.
Most chutes simply provide an open channel for material to fall through, which leads to an uncontrolled spread of material and more dust. A controlled flow design, based on the material's inherent qualities, speed, volume, and throughput requirements, can provide a more efficient flow of material and reduce dust.
The effective control of coal dust starts with the early stages of plant design, says Nienaber. The positioning of crushers, screens, feeders, conveyors, and other plant equipment in relation to each other is crucial to achieving control over the material flow. Transfer chute experts can play a valuable role in advising plant designers on the optimal positioning of equipment during the planning stage, leading to a more efficient flow of material and reduced dust.