Method for reducing the amount of coal dust in the environment

Abstract

Coal dust laden air is treated with an aqueous foam of controlled durability and controlled penetrability so that a very high proportion of the particles in the air, including very small particles, are captured by the foam and drained into the liquid resulting from the collapse of the foam. The foam has a propensity to collapse during a brief period, thus forming drainage liquid. The volume of drainage liquid five minutes after foam generation provides a measure of the controlled durability of the foam. The usefulness of the foam is also affected by the rate at which the liquid resulting from foam collapse is absorbed into absorbtive materials, which rate should desirably be slower than the absorption rate of water. The precursor for the foam is a very dilute aqueous solution containing a surfactant plus a synthetic gum in a concentration from about 15 percent to about 45 percent of the weight of the surfactant. An appropriate mixture of sodium salts of alkylated benzene sulfonic acids is an effective surfactant which can be combined with about 35 percent of sodium carboxymethylcellulose having a substitution range from about 0.38 to about 0.48 and a sodium content near 5 percent plus or minus 0.5 percent which type of sodium carbomethoxycellulose is marketed as 7H-4 type of cellulose gum. Such gum has a viscosity of about 3,500 centipose plus or minus 1,000 centipoise when dispersed as a 1 percent solution in water.