Research and Application of A Novel Descaling and Anti-Scaling Technology In Integrated Utilization of Geothermal Energy

Hot springs are very precious geothermal energy resources. Their three characteristics of "heat, mineral and water" make it great potential for integrated, comprehensive development with the primary, secondary and tertiary industries.  Hot springs have a high medical value because they contain many trace minerals that benefit human health. However, one of the main problems in their applications is the scaling of conveying pipelines and systems.  There are various ways of descaling processes in the market, but limited descaling techniques are available for consumer recreation sites such as hot springs, which require higher health concerns.  This paper describes a new descaling and prevention process developed independently not to damage hot springs’ water quality.  Starting from the well, the problem of carbonate scaling in hot spring water is solved through comprehensive control of pressure, temperature and pH value of hot spring water, and the quality and utilization of hot spring water are improved simultaneously.  This process is mainly aimed at utilizing and applying hot spring systems with carbonate scaling.  The formation mechanism of carbonate scaling is primarily related to the pH, temperature, pressure and salinity of hot spring water, which interact and influence each other. We first analyze the geochemical process of geothermal fluid through the stratigraphic structure, then examine the composition of scale and the cause of scaling in hot spring water through the scale components and water quality characteristics.  Finally, we calculate the carbonate saturation coefficient using the Oddo-Tomson saturation Index to evaluate the scaling trend of hot spring water.  On this basis, deep well pumps, heat exchangers, vacuum devices, filters and other equipment are used to control the pressure, temperature, and pH of the geothermal transport process under various working conditions to achieve the effect of scale removal and prevention.  The study found that increasing the wellhead pressure and lowering the temperature can effectively prevent carbonate scaling in the transport pipelines and improve the water quality of the hot springs.  As a result, the outlet temperature can be increased by more than 20℃, raise the bicarbonate ion by about 30%, and increase the export calcium and magnesium ion concentration. The study also found that calcium and magnesium ion precipitation can be enhanced under the optimized conditions of certain pH and vacuum degree to achieve the purpose of enhanced descaling.  Water quality analysis showed that the process only influenced the reduction of sodium, strontium and bicarbonate ions in hot spring water, but had little effect on other minerals and trace elements.  The new anti-scaling and descaling methods can improve the quality of hot spring water, maintain the activity, health and medical value of hot spring water, enhance the comprehensive utilization of geothermal resources, and harbor great commercial applications.