Binary plant retrofitting of a single-flash steam plant

Abstract

The edge of the Pacific Ocean is an area of strong tectonic activity marked by volcanoes and seismic activity. In all countries around the Ring of Fire, such as New Zealand, Japan, Indonesia, the Philippines and the western coastal Americas, harnessing the geothermal power potential capacity is of strategic importance for these countries growth. Developing a new steam field faces many challenges, takes time, costs a significant amount of equity, has mineral risk, and confronts environmental and regulatory issues. Existing steam fields frequently use single flash, steam turbine power generation plants. Although efficient and reliable, a significant part of the total thermal capacity is lost in the liquid-phase (hereinafter called brine). This paper describes in detail how it is possible to recover safely and efficiently the energy contained into the brine, otherwise wasted. In fact, just utilizing the energy contained in the existing brine, it is possible to add approximately 30% of the steam field rated electrical power output thanks to the Exergy GEX binary plant, based on its patented Radial Outflow Turbine (ROT). This type of design is in operation in different markets around the world, such as in Italy, Turkey and Portugal (the Azores Islands). The paper will focus on a case study where further issues are addressed, such as silica scaling, by applying state of the art geochemistry.