An Empirical Correlation for Zero-Net Liquid Flow in Gas-Liquid Compact Separator

Abstract

Compact separators have significant application for subsea separation and offshore application. However, their operating envelope is usually narrow due to physical phenomena such as liquid carryover and gas carry-under. Before the occurrence of liquid carryover, the separator operates in what is termed zero-net liquid flow (ZNLF). Though there is an efficient separation during ZNLF; there is also liquid holdup in the upper section of the separator, which is termed as ZNLF holdup. The ZNLF holdup in a cyclonic separator during an actual gas-liquid separation was studied experimentally. The ZNLF holdup was measured directly using electrical resistance tomography (ERT). The direct measurement approach is an improvement of the existing method, which depends on measuring the pressure drop across the stagnant liquid column. The results showed that increasing gas flow rate at a constant liquid flow rate increase zero-net liquid holdup in the upper part of the separator. An empirical correction was developed, and the correlation predicted the experimental results with a ±10% error margin. The correlation could be useful as part of the input into a pressure drop model for calculating pressure drop across the gas leg of the cylindrical cyclonic separator. This correlation will be useful to process engineers for optimum design and operation of a gas-liquid compact separator.