Geothermal Mineral Recovery

Abstract

The first thought is: why? After reviewing the potential benefits, the question becomes: how soon?

The United States Strategic Mineral reserve is important to our homeland security. Some minerals found in geothermal silutions are critical to U.S. reserves.

A group of minerals that is important to the study of geothermal silutions is the silicates, which abound in many geothermal sites (see Figure 1.) The recovery of these minerals has multiple effects on the geothermal industry. First, if silica is not recovered, it starts precipitating out at about 240 degrees F. This necessitates reinjection above the precipitation temperature, unless there is a market for the material, and also prevents the recovery of heat energy, as heat can be recovered down to a little over 100 degrees F. Reinjecting the solids keeps the silica in solution, and it causes scaling as it passes through the geothermal plant and at the injection well. The recovery of silicates both dramatically reduces the scaling problem and allows more energy recovery, as the brines can be reinjected at a lower temperature.