SNF were asked to help a major player in the coal industry to stop dust from wind eroding the surface of stock piles of coal and coke leaving the site causing problems in nearby residential areas. Dust erosion is not only a problem with loss of valuable resource but an environmental pollution concern.
An approach was made to SNF to see if it could solve the problems on site. Experienced SNF technical staff visited site to assess the problem. The following simple but effective approach was put in practice:
Initially the different types of stock were identified. These were coal, pet coke and low sulphur pet coke. The low sulphur pet coke and pet coke were seen to be particularly bad causing the most problems in terms of airborne dust.
Small test stock piles of the three substrates (as discussed above) were laid out in a trial area, 4 piles of each type of stock were arranged.
The dust suppressant was prepared at various concentrations (0.5%, 0.75%, 1% and 1.5%) so that its binding effect may be assessed.
An area of approximately 1m2 of each type of stock was sprayed with the 4 different concentrations of the dust suppressant with a small area around each treated section being left unsprayed to allow for easy comparison between treated and not treated sections.
A diagram of the testing regime was made of the trial area so that each trial section can be readily identified and assessed.
The coal and pet coke sample piles visually required approximately 0.5 litre / m2 of the dust suppressant solution (at all the concentrations evaluated) for even coverage (10,000litres/20,000m2). The only exception to this was the low sulphur pet coke, which with its high fines content and spherical nature is extremely Hydrophobic. This required approximately 1.0 litre to cover 1m2 (10,000litres/10,000m2).
The sample piles were then fenced off to prevent accidental surface damage other than environmental impact (weathering).
The treated sections will now be left for several days before assessment of the various stock piles. Positive “capping” or “permanent” crust formation of approximately 5-10mm penetration down into the stock pile will slow down both wind and rain eroding the layer too quickly so preventing erosion of the stock causing airborne dust.
Once the trial has been completed, and an effective dose determined, SNF will recommend a procedure and concentration which will effectively treat each type of stock at the site.
Coal sprayed with the dust suppressant at a concentration of 0.5% – slight crust and bonding has formed on the surface of the coal pile, however, this crust breaks up fairly easily when disturbed.
The results above are deduced by visual and manual analysis of the stock piles. As the customer wants the problem to stop immediately, it was decided to recommend a slightly stronger concentration for each stock type to achieve this. Together, Customer and SNF will undertake further full scale trials to deduce whether the doses recommended from this trial can be reduced to a more efficient and economical level.
Pet Coke and Low Sulphur Coke require a dose of 1.5% which equates to 450 litres in a 30,000 litre tanker. Coal requires a dose of 1% which is 300 litres in a 30,000 litre tanker. SNF and the customer will continue to carefully monitor and assess the dust suppressant use to ensure that the treatment is effective.