Separation Vs Filtration

1. Removal by Inertial Impaction Uses the energy from the fluid Removal of larger particle size, 10 micron and above Used for bulk removal Removal by Direct Impaction Uses Filter Media with close mesh size (and inertial device) Removal of fine particle size, typically 1 micron and above Used for both bulk & aerosol removal Separation Vs Filtration

2. Removal Efficiency, location of the filter system Properties of Gas, flow rate Type and quantity of Particle to be removed and its properties Operating pressure & temperature Type of controls required Pressure drop allowed & Turn-down Ratio Material specification Factors Influencing Gas Filtration Selection

3. Location & Removal Efficiency Type & Property of Contaminant – Oil in particular Gas Property or MW or Sp. Gravity Flow Rate – Min / Max Operating Pressure – Min / Max Operating Temperature – Min / Max Allowed pressure drop Liquid Holding time or capacity Controls required Configuration – Horizontal, Vertical, In-line Special material, if any, required Information Required

4. Flow rates converted to ACFM or ACFS. At low pressure ACFM will be higher than at High Pressure. At high temperature ACFM is higher than at low temperature . SCFM and LB/Hr are independent of pressure and temperature while ACFM is sensitive to these. Flow Rate

5. Low pressure increases the ACFM. High pressure increases cost of separator. High pressure increases density resulting in decrease in density difference between gas & liquid and separation becomes more difficult. Drop in allowable shear force and therefore reduced velocity. (rV2) Mass flow rate is independent of pressure for a given SCFM. Operating Pressure

6. High Temperature increases ACFM. Influences filter element selection. Influences material selection. Influences control instrument selection. Mass flow rate is independent of temperature for a given SCFM. Operating Temperature

7. Composition influences MW. MW decides specific gravity. Specific gravity influences density based on operating pressure and temperature. Density influences velocity through the device and the size of the Separator. ACFM is independent of MWfor a given SCFM. Gas Property

8. Solids, solids and liquids, liquids. Nature of liquid and volume flow rate, Liquid/Gas ratio, Density of liquid. Viscosity of the liquid, if high drainage would be a problem, may require a mesh pad foe vane packs. Surface tension, if shear stress drops, re-entrainment would occur. Above factors dictate size, type of device and controls required. Type of Contaminant

9. Inertial Separators typically can remove only 10 micron and above. Vane will not guarantee removal of solids. If heavy oil is present may require mesh pad addition. Re-entrainment occurs at high gas velocity, dictates size of filter vessel. Influences filter element selection . Influences configuration. Removal Efficiency

10. Location of the system. Is slug involved. Type of Draining: Automatic or Manual. Volume flow rate of liquid. Above factors decide sump capacity & type of control. Sump capacity dictates separator size. Liquid Holding

11. CompressibilityFactor, Z, corrects the gas density for deviations from the ideal gas law. Use client specified value or use TEMA or Chemical Engineers Handbook. Use 1 if details not known. Compressibility Factor

12. Inlet velocity not to exceed rV2 = 4500, based on TEMA guidelines. Inlet to have a baffle to break the momentum and to protect against slugs. If oil or other liquid contaminants expected, vane pack with/without mesh pad or multi-cyclone type device required. If vane is selected for first stage and if inlet is directly in front, to use agglomerator . Holding capacity required. Size of inlet/outlet to vessel size. Design Considerations