Working with fine powdered raw materials can literally mean getting a lot of dust up your nose. What a headache! Do you sometimes feel this problem is getting out of hand?

The implication of dust in the air on workers usually means they need to wear dust masks, which tend to generate a measure of unwanted discomfort and dissatisfaction, if your workers are anything like ours. The level of worker complaints start to rise and can even lead to a general strike if the dust problem gets too bad.

In another article on silicosis, I discussed in some detail about the more sinister threat of silicosis. This is a disease of the lungs that can result from lengthy exposure to breathing fine silica dust. Although a water-washed kaolin like Serina kaolin contains virtually no free silica, many other fillers do contain some free silica as an impurity which workers could be inhaling when conditions are very dusty. The worst-case scenario for managers like ourselves would be the nasty threat of lawsuits if we allow the situation to degenerate. But what can we do about dust, then?

Extraction systems

First to mind, is to remove the dust in the air by installing a dust extraction system – good idea. Some capital expenditure is involved in this option.

Enclosed vessels

Ha! – even better. Handle all dusty raw materials in fully enclosed systems. Although again capital expenditure is required, the results are usually worth it. At Serina, we replaced our open conveyor belts with closed tube conveyor belts with very satisfying results. These also removed the threat of contamination of the product by exposure to the open air. The kaolin pellets are moved through the conveyor by discs attached to a chain as shown in the picture:

Negative pressure

The trouble with fine dusty powders is that as soon as they fall any vertical distance, a fine cloud of powder is usually the result. So even if you have an enclosed vessel, the dust still escapes into the outside air. One way to get around this problem is to create a slight negative pressure in the vessel so that the outside air is slowly being drawn into the vessel, preventing any dust escaping out of it. The usual filters will have to be in place for the circulating air in such a system, but at least the dust does not get up your nose!

Fillers in PELLET form

All the options above require some capital expenditure to install. However another way to reduce the dust levels in your factory without capital expenditure, is to buy your filler in pellet form (if available), instead of in dry powder form.

Serina kaolin is available in both of these forms. The kaolin pellets are exactly the same as the powder in chemical and physical properties (e.g. particle size distribution), the only difference being that the kaolin is held together by 10% moisture to form pellets about 2 cm long and 1 cm in diameter. The pellets still look and feel dry, as shown in this picture:

Of course your process must be able to tolerate the 10% moisture content of the pellets. If you are making an aqueous slurry anyway, it is no problem to use the pellets instead of the powder. The pellets disperse easily in water with mechanical agitation. (If the dispersion needs to be speeded up, a dispersant can be added). So water-based paint, adhesive and ink applications, as well as soap, ceramic and paper applications could all use the pellet option with no problem – and therefore benefit from the lower dust levels during handling. The pellets are cheaper than the dry powder too, even with the moisture content taken into account, so there is another great benefit to using the pellets.

So I hope this has helped and I wish you less dust up your nose in future. 

Here is a quick reference to South Africa's Occupational Health and Safety Act


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Contact: Jenny Jay
ATSC. Ph.D (Chemistry)
Managing Director