Mobile Foam Dust-Suppression System

01 October, 2007

Best-Chem develop innovative dust-control solution for Hanson site

Earlier this year Hanson Aggregates decommissioned their crushing and processing plant at Ystrad Meurig Quarry, near Aberystwyth, Wales. This facility was replaced with a complete mobile crushing and screening plant, supplied by Metso Minerals, which has the capacity to process around 500,000 tonnes of stone (greywacke) per annum.

Water sprays are fitted at the head of the conveyors that feed the stone to the mobile crushers in order to wet the stone and suppress dust emissions. However, these sprays were having a very limited effect and there was, therefore, a serious dust issue that had to be addressed. The high level of fugitive dust was causing concerns relating to employees’ health, the local environment and vehicles operating in the quarry.

The addition of more water sprays was not the answer – as this not only failed to solve the dust problem but also led to screen blinding. Given the fully mobile nature of the installation, an imaginative and innovative solution was called for, and so in early June Best-Chem Ltd were approached to see what could be offered under these circumstances.

Having surveyed the site, it was clear to Best-Chem that the dust-suppression system also needed to be ‘mobile’ and capable of being moved with the crushing plant. In addition, given that the working area was very exposed, it became apparent that the options were somewhat limited.

A mobile foam dust-suppression system was recommended and a full-scale trial was offered using Best-Chem’s mobile foam-generating unit. The trial was carried out in mid-June and, based on the results (see before and after photos), Best-Chem were commissioned to design, build, supply and install the first ever integrated trailer-mounted mobile foam system.

Delivered in the first week of September, the system is housed in an enclosed Ifor Williams twin-axle trailer with roller shutters at one end and a personnel door at the other, and comprises:

a Best-Chem foam-generating unit
an air compressor
a chemical storage tank
a control panel
lights
a heater
reels for foam delivery hoses
easy camlock fittings for foam and water supply hoses
weather-proof, IP65-rated power and control connections on the exterior of the trailer.

The system is fully automated and its key features include:

The ability to apply foam at up to six different locations around the mobile crushing plant.
A low power requirement, taken from the auxiliary supply on the mobile crushers.
On/off signals taken from the belt scales on the conveyor leaving the primary crusher; this ensures that foam is only applied when there is material being processed and does not require any operator intervention once the system is switched on at the beginning of the day.
A chemical supply drawn from a 1,000-litre IBC housed in the rear of the trailer; the IBC is connected with easily operated camlock fittings to eliminate spillages.
Easily adjustable foam application rate to suit prevailing weather conditions; if the weather has been persistently wet, the flow rate can be either reduced or turned off at one or more application point.
Specially designed nozzles for consistent foam application are attached to the crushing plant using easily removable fittings so that they can be taken off during maintenance.
Flexible rubber hose used for delivery of the foam with camlock fittings for quick and easy removal and re-installation.
Efficient interior design of the trailer allows easy access to all components to simplify maintenance tasks.
Trailer fitted with standard tow bar, including lights, allowing the system to be easily moved around the quarry or to another quarry if required.

The mobile foam system delivers approximately 20 litres of solution per minute (150 parts water and one part Dustrol – Best-Chem’s proprietary foaming and binding agent). This is converted to foam as it travels down the rubber hoses to the five application points. The foam is applied directly into the jaws of the primary crusher; at the head end of the conveyors taking material to the secondary and tertiary crushers; and directly into the secondary and tertiary crushers.

Up to 95% of the fugitive dust is now captured during the crushing process, while the low level of moisture added ensures that the screens do not suffer from blinding, nor is there any contamination resulting from dust sticking to the larger stone sizes.

Simon Swinford, manager of Ystrad Meurig Quarry, is happy with the response and advice offered by Best-Chem, whose mobile foam system has solved the quarry’s dust problem. He said: ‘The initial trial was quite impressive; it didn’t take long for the foaming system to take effect when switched on. The mobile unit since supplied is very easy to move around the site and, at such an early stage, is proving very effective in combating the airborne dust produced by the crushing and screening process.’