Reykjanes Geothermal Field: Development of Combined Vertical and Horizontal Separator

Abstract

In the Reykjanes geothermal power plant, the steam is separated from brine at high pressure and the hot brine disposed of. Bottoming unit is being developed in which the hot brine will be flashed in two stages and the medium- and low-pressure steam used in a dual flash turbine to generate 30 MW of electricity. Two horizontal separators are used in the power plant for separation of high-pressure steam and brine but, although very effective, horizontal separators are not suitable for the low-pressure separators because of high silica scaling rate. Effective steam purification is very important already in the first step of separation because of the high salinity and silica content of the brine. For obtaining the dual purpose of effective steam separation and minimal scaling a combined vertical and horizontal separator was developed. In it the brine tangentially enters the vertical part and is separated from the steam by centrifugal action. The steam then flows into the horizontal part and droplets are separated by gravitational settling and finally the steam is purified in a mist eliminator. The design was tested in an experimental separator for 25 kg/s of 207 °C brine, which was flashed in two stages producing 2.5 kg/s of MP-steam at 155 °C and 2.0 kg/s of LP-steam at 108 °C. The tests were successful and separator efficiency of 99.99% could be obtained. The design is now being scaled up for full size separation of 410 kg/s of brine and production of 38 kg/s of MP-steam and 34 kg/s of LP- steam.