GMH carries out investigations of air movement and dust in chutes and loading points using fluid dynamics software to enable us to deliver to our customers the benefits from this information in the design stages of the chutes and loading points.

Solving dust emission due to air movement
The first step we take is to identify what the air is actually doing both above the belt and in the chute. To identify the movement of air, Computational Fluid Dynamics [CFD] programmes are used to predict the air movement in the chute and of the air as it leaves the chute. After identifying the movement of air in the chute we look at the velocities involved and see if they were sufficient to entrain the material. Then we will identify a way of reducing or completely eliminating the air velocity.

There are a variety of scientific principles that govern the pick up of dust by re-circulating air: The first is the pick up velocity. For macroscopic particles like those on a belt, so quite simply, for a particle of fixed size and density you have to reduce the air velocity. The second is the Stokes Number: this governs the balance between inertial forces and fluid forces. Essentially if we can reduce the fluid forces and make the inertial forces dominant in this equation we can induce the particle to settle.

What have we achieved?
We have proven computationally and experimentally that it is possible to reduce the re-circulation velocity both in the chute and above the belt.

We now have the knowledge and means to design a bespoke chute that would reduce the velocity of the air and dramatically reduce the unwanted emission of dust.

A combination of Computational Fluid Dynamics (CFD) and onsite investigation has revealed that the control of dust has to be a combined strategy of controlling both the dust and the air velocity within the chute carrying entrained dust particles. The GMH chute design delivers the solution to reducing dust emission and giving control back to the operators in their push for cleaner transport from stockpile to bunker.