The precipitation of “aluminum silicate” under geothermal stresses: Identifying its idiosyncrasies

Abstract

The interest in the usage of geothermal energy has increased exponentially during the past few decades and researchers internationally are currently focusing on improving the harvesting methods and promoting it due to its many benefits, compared to traditional energy sources. Corrosion and scaling are two of the most severe problems occurring when harvesting geothermal energy. Scaling takes place due to the variety of anions and cations that the majority of the geothermal reservoir waters contain, and are prone to both precipitation and deposition when subjected to dramatic changes in temperature and pressure, causing failures to several parts of the plant. One of the most commonly occurring scales in such systems is aluminum silicate, a persistent deposit whose structure, as it is formed in geothermal waters, differs completely from its geological counterparts. In this work we focus on revealing the true nature of the so-called “aluminum silicate”, performing a series of synthesis experiments under various conditions that take into account aluminum and silicate concentrations, solution pH and temperature. Complete physicochemical characterization of the aluminum and silicate precipitates reveals that it is a precipitate that shares several characteristics with amorphous silica.