An Evaluation of Single Flash Power Plants with ORC Bottoming Units at High NCG Content

Abstract

The use of ORC bottoming units in series with steam turbines bring forth some advantages compared to single flash units with conventional cooling circuits. One of the most evident advantages is that an ORC unit does not require power for the extraction of non-condensable gases since the condensing process takes place at a pressure higher than atmospheric pressure. However, the ORC unit has lower thermal efficiency compared to conventional single flash units, and therefore the power produced with this integration is lower in terms of overall produced net power compared to single flash only. Although this is the case, the use of an ORC as a bottoming unit might help produce more overall net power in cases where the NCG content is high enough to make the gas extraction process demanding in terms of power consumption. In this study, we will try to identify roughly at which percentage of NCG content in steam, the use of an ORC as a bottoming unit will be advantageous against the conventional single flash cycle in terms of net power production.