Inhibition of Antimony Sulfide (Stibnite) Scale in Geothermal Fields.

Fouling of different components of geothermal power production is one of the limiting factors in efficient use of the geothermal resources. Most common scales are silica, calcium carbonate, and calcium sulfate while, less common are iron, iron silicate, Ba/Sr sulfate and calcium fluoride. Sulfides of antimony and arsenic are local to some geographic areas. The latter scales are highly insoluble and depend on their oxidation state, pH and temperature. Antimony sulfide, commonly known as Stibnite is quite common in New Zealand and occurs mostly in low temperature area such as binary system heat exchangers. The paper discusses laboratory and field study on the mitigation of antimony sulfide scale by the addition of scale inhibitors.