Numerical evaluation of separation efficiency in converging T-junction with slug flow

Abstract

Purpose Excessive liquid carryover in T-junction presents a serious operational issue in offshore production platform. Slug flow and diameter ratio of T-junction are considered as two major factors causing liquid carryover. Regular and reduced T-junction are being used as partial phase separator but their efficiency is low. Converging T-junction with two distinct diameters (primary and secondary) in branch arm is used to improve the phase separation efficiency. The motivation is to combine specific feature of regular and reduced T-junction to increase separation efficiency of existing T-junction without involving too much operational workover. The purpose of this paper is to numerically evaluate the separation efficiency of a converging T-junction design. The present model and its methodology was validated with in-house experimental data for 3 inches diameter flow loop. Design/methodology/approach The slug flow regime was simulated using incompressible Eulerian mixture model coupled with volume of fluid method to capture the dynamic gas-liquid interface. Findings The analyses concluded that T-junction with primary-secondary branch arm diameters combination of 1.0-0.5 and 0.67-0.40 managed to achieve 95 per cent separation efficiency. The research also confirmed that over reduction of T-junction secondary diameter ratio below 0.2 will lead to decrease in separation efficiency. Research limitations/implications The present research is limit to air/water two-phase flow but the general results should be applicable for wider application. Practical implications The proposed design limited excessive workover and installation for current and existing T-junction. Hence, cutting down installation cost while improving the separation efficiency. Social implications The present research resulted in higher separation efficiency, cutting down production down time and lead to operational cost saving. Originality/value The present research proposes an original and new T-junction design that can increase phase separation efficiency to over 90 per cent. The finding also confirmed that there is a limitation whereby smaller diameter ratio T-junction does not always resulted in better separation.

Numerical evaluation of separation efficiency in the diverging T-junction for slug flow

“…For comparison purposes, similar velocity ratios were illustrated. Furthermore, two converging T-junctions mentioned in this figure have the highest separation efficiencies among other tested converging T-junctions tested by Pao and Memon (2019).…”

“…The converging design of the T-junction has the advantage of geometry. As explained by Pao and Memon (2019), sudden convergence in the sidearm acts as a barrier to the incoming liquid. Consequently, liquid loses its momentum in the process, hence there are high chances of liquid fall back.…”

“…Regular T-junction data belong to Saieed, obtained through experimentation. Separation efficiencies of converging T-junctions were given by Pao and Memon (2019). For comparison purposes, similar velocity ratios were illustrated.…”

“…The geometry designed in this research study is similar to the practical flow loop facility used by Saieed (Saieed, 2018). For comparative analysis, diameter ratios were selected as the exact opposite of the published data for converging T-junction (Pao and Memon, 2019). The first part of the geometry is a mixer and the rest of it is the T-junction.…”

“…Comparatively, the most efficient method is to calculate the separation efficiency using the area under the curve. More details on the justifications for selecting this method were mentioned by Pao and Memon (Pao and Memon, 2019) and will not be repeated here. …”