1st Floor ulate-generating material. This measure prevents (or suppresses) the fine particles contained in the material from leaving the surface and becoming airborne. The chemical agents used in wet suspension can be either surfactants or foaming agents. Figure 5.23.2 shows a suppression system at a crusher discharge point.

The use of foam injection to control dust from material handling and processing operations is a recently developed method to augment wet suppression techniques. The foam is generated by a proprietary surfactant compound added to a small quantity of water, which is then vigorously mixed to produce a small-bubble, high-energy foam in the 100 to 200 /m size range. The foam uses little liquid volume and when applied to the surface of a bulk material, wets the fines more effectively than untreated water does. Foam has been successfully used in controlling the emissions from belt transfer points, crushers, and storage-pile load-ins.

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