[ gas-liquid separation ]
Fig. 5. Parker Gemini Pura-Sep horizontal gas filter-coalescer
tension is reduced, resulting in a smaller average droplet diameter. The gas density is also increased, reducing the differential between the gas and liquid phases. The Stokes number is therefore reduced, and the separation efficiency decreases as the liquid droplet is more likely to follow the gas path. 14
The pressure drop of a clean fibrous filter media of thickness h can be estimated using the following expression:
Where f( β) was given by Davies( 1973) from experimental analysis of different filter media as: 15
f
1.5 � � � �
� �16� 1�56� for 0.006 ��
�0.6
Pressure drop for flow parallel to the fibres is half that of the flow perpendicular to the fibres. 15 Several filters of equal pore size can be arranged
in parallel and operated simultaneously to enable increased flow rate without increasing the pressure drop. The total flow rate and pressure drop are equally distributed across each filter. Conversely, multiple filters arranged in series can be used to improve removal efficiency and deal with a wide range of particulate sizes. 10 Minimising the pressure drop of the coalescing filter can contribute to improved plant efficiency by reducing the necessity for downstream hydrogen compression.
Conclusion
As in many industrial processes, gas-liquid separation is an integral part of the green hydrogen flowsheet. Simple design rules based on empirical correlations can be adopted for the preliminary sizing of separators, and mature technology exists for the removal of entrained liquid droplets.
Parker engineers within the Hydraulic and Industrial Process Filtration Division EMEA( HIFE) have redeployed the market-leading PEACH
36 Hydrogen Tech World | Issue 22 | June 2025