How are 'scavenging steam' and 'non-condensable gases' managed in a binary power plant cycle?

In a binary power plant cycle, which uses a secondary working fluid (like isobutane or pentane) heated by geothermal fluids to drive a turbine, managing scavenging steam and non-condensable gases (NCGs) is crucial for maintaining efficiency and preventing operational issues. Scavenging steam, in this context, refers to small amounts of steam that may leak into the binary cycle from the geothermal heat source, or auxiliary steam introduced for operational reasons. While binary plants are closed-loop systems, small leaks can occur. NCGs, such as carbon dioxide (CO2), hydrogen sulfide (H2S), and nitrogen (N2), are often present in geothermal resources and can also enter the binary cycle. Scavenging steam is typically managed by carefully sealing the heat exchangers and other equipment to minimize leaks. Steam traps can be used to remove any accumulated condensate from the steam lines. Regular inspections and maintenance are essential to identify and repair any leaks. The management of NCGs is more complex. NCGs accumulate in the condenser, which reduces the partial pressure of the working fluid vapor and impairs the condensation process. This reduces the pressure drop across the turbine, lowering power output. To remove NCGs from the condenser, a gas extraction system is used. This system typically consists of a steam jet ejector or a vacuum pump. The steam jet ejector uses a high-velocity jet of steam to create a vacuum, which draws the NCGs out of the condenser. The vacuum pump directly removes the NCGs from the condenser. The extracted NCGs are then typically vented to the atmosphere or processed further to remove any valuable components or to comply with environmental regulations. Regular monitoring of the NCG concentration in the working fluid is essential to optimize the gas extraction system and maintain plant efficiency. Therefore, effective management of both scavenging steam and NCGs is vital for the reliable and efficient operation of a binary geothermal power plant.