An upstream reboiler design for removal of noncondensable gases from geothermal steam for Kizildere geothermal power plant, Turkey

Kizildere geothermal power plant, Turkey, has an installed capacity of 20.4 MWe. The field contains a high level of noncondensable gases (NCGs), changing from well to well, in amounts as high as 10-20% (with an average of 13% at the inlet of the turbine) by weight of steam. This amount of NCGs is being extracted from the condenser by gas compressors that consume about 17% of the total power production of the plant. An upstream reboiler process could be adopted to remove the NCGs from geothermal steam before they enter the turbine. Upstream reboilers therefore provide a cleaner and less corrosive steam supply to the turbine and condenser, increasing power generation performance for very high NCG contents. In this paper, upstream reboiler systems are investigated as an alternative to conventional gas extraction systems for Kizildere geothermal power plant. A vertical tube type reboiler has been designed and it is found that, as NCG content increases, the condensation hear transfer coefficient reduces steeply. It is concluded that vertical tube type reboilers are not efficient for fields that contain high levels of NCG (>15% by weight of steam). It is recommended that the use of direct contact reboilers be further investigated for this application. (C) 1999 CNR. Published by Elsevier Science Ltd. All rights reserved.