Fuzzy Control of Calcium Carbonate and Silica Scales in Geothermal Systems

Abstract

Calcium carbonate and silica scaling occurrence are main problems, which affect production efficiency directly, during operational period for geothermal power plant or district heating application. Although their precipitation mechanism are different each other, both of them can be observed with different proportion in production and reinjection wells and surface equipments in geothermal systems. Thus, scale prevention and control systems are very important and controlling of scaling is easier than remove of them from wells and equipments after precipitation in a geothermal system. There are a few methods for controlling of silica and calcium carbonate precipitations in geothermal wells and surface equipments. Most production and reinjection wells require the implementation of a silica/calcium carbonate inhibition system to prevent silica/calcite precipitation inside the casing or pipes, separators in geothermal fields. Installing of inhibitor systems are the best and practical solution to prevent scaling problems and production loss if the optimum inhibitor dosages are determined and applied effectively in geothermal systems. Less than optimum ratios of inhibitors can result in product overfeed, increased costs, and in some cases, inhibitor induced fouling. This may be solved by fuzzy controller in geothermal systems. It is difficult to obtain the mathematical model, describes the relation of geothermal fluid characteristic and inhibitors. Because, the system is nonlinear and has a few dependent and independent variables. Fuzzy control may replace the role of the mathematical model in conservative controllers and substitutes it with another that is built from a number of smaller rules that on general only describe a small section of the whole system. In this study, two fuzzy logic controllers have been designed to control of the precipitation of silica and calcium carbonate by using scale inhibitors.