Recent Developments in Geothermal Scale Control

Abstract

Successful scale control treatment programs have been demonstrated and implemented for a variety of scale deposits encountered in the production of geothermal power, including calcite and metal silicates. More recently, inhibition of clay minerals has been demonstrated as well.

Control of amorphous silica scale has proved more challenging, and in many cases, is limited to pH modification. Chemical treatments developed to control metal silicates have limited effect against silica because formation of silica deposits involves different mechanisms and is controlled by different factors. A new class of inhibitors, different from the chemicals used to inhibit metal silicates, has been identified and is being qualified for field testing.

Computer modeling work suggests that returning carbon dioxide to flashed brine can control deposition of metal silicate scales in the heat exchanger of a combined cycle generating system while reducing or completely eliminating the need for silicate inhibitors.