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Gas Plant Separator Design
- 1. Separator Design Abita Antony Cyril Iyasele Natural Gas Engineering March 25, 2010
- 2. Outline Introduction Separatorconfigurations Demisters Sizing separators Summary
- 3. Introduction to PhaseSeparation Physical separation of natural gas to its component phases The temperature and pressure of the gas dictates phases present Occurs in a pressure vessel provided for that purpose Mist extractors-wire mesh, vanes, or baffles- reduce liquid entrainment
- 4. Separator Configurations Aseparator is a vessel used to separate a mixed-phase stream into gas and liquid phases that are ‘’relatively’’ free of each other Principles used to achieve physical separation of gas and liquid include: • momentum • gravity settling • coalescing Large volume of total fluid Large amount of dissolved gas High gas-liquid ratio Low total gas volume
- 5. Demisters Also knownas mist extractors Removes suspended mist or liquid entrainment Liquid removed is coalesced into larger droplets
- 6. Sizing Separators Specifying separatorsrequires: Pressure, temperature Flow rates physical properties of the streams Degree of separation required Specifications include: Diameter L/D ratio Vapor Space height Liquid residence time
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- 8. Sizing Separators Parameter Feed Vapor Outlet Liquid Outlet Flow rate 44 MMscfd 42.42 MMscfd 1.575 MMscfd Pressure 613 psia 613 psia 613 psia Temperature 68 F 68 F 68 F Separator Worksheet Vapor Liquid Components Feed (mol%) Outlet(mol%) Outlet(mol%) Nitrogen 0.20 0.21 0.00 CO2 4.50 4.65 0.49 H2 S 1.80 1.85 0.48 C1 78.31 81.08 3.51 C2 4.10 4.22 0.78 C3 3.10 3.15 1.70 iC4 2.00 1.99 2.30 nC4 1.50 1.47 2.29 iC5 0.70 0.65 2.14 nC5 0.50 0.45 1.90 C6 0.30 0.22 2.44 H2 O 3.00 0.07 81.97 Total 100.00 100.00 100.00
- 9. Sizing Separators Computer SimulationMethod EOS: Peng-Robinson
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- 13. Sizing Separators GPSA -Hand Calculation Method (Various Separator Configurations) Without Demister Case I: Horizontal separator Case II: Vertical separator With demister Case III: Horizontal separator (<10 ft ; >10ft) Case IV: Vertical separator
- 14. Sizing Separators Cases I& II: Horizontal & vertical separators without demister Horizontal Without Demister Vertical Without Demister Diameter (ft) Length (ft) L/D ratio Diameter (ft) Length (ft) L/D ratio 2.50 11.80 4.72 5.43 19.02 3.50 2.80 10.50 3.77 3.14 9.42 3.00
- 15. Sizing Separators Cases III& IV: Horizontal & vertical separators with demister Only for :Horizontal >10 ft Vertical With Demister Horizontal With Demister Diameter (ft) Length (ft) L/D ratio Diameter (ft) Length (ft) L/D ratio 1.40 7.00 5.00 2.87 10.05 3.50 1.50 6.50 4.36 1.80 5.40 3.03
- 16. Horizontal Separator withDemister- Case II ( L >10 ft ) L changes with Vt L/D ratio: b/w 3 ~ 5 Vt changes with L assumed Length (ft) Terminal Velocity (ft/s) Diameter (ft) L/D ratio L Vt Dv r 11 1.45 0.85 13.00 12 1.52 0.74 16.25 13 1.59 0.65 19.94 14 1.66 0.58 24.11 15 1.72 0.52 28.77
- 17. Summary GPSA GPSA HYSYS HYSYS GPSA (Vertical GPSA (Vertical (Horizontal (Horizontal (Horizontal) (Vertical) w. Demister) w/o Demister) w. Demister) w/o Demister) L/D ratio 3.00 3.00 3.50 3.50 3.00 3.50 Length (ft) 13.50 5.40 15.75 10.05 9.42 19.02 Diameter 4.50 1.80 4.50 2.87 3.14 5.43 (ft)
- 18. Next Design Stage Separatoroutlet vapor stream Parameter Vapor Outlet H2 S Flow rate 42.42 MMscfd Sweetening Pressure 613 psia CO2 Temperature 68 F Components Vapor Outlet(mol%) Nitrogen 0.21 CO2 4.65 H2S 1.85 C1 81.08 C2 4.22 C3 3.15 iC4 1.99 nC4 1.47 iC5 0.65 nC5 0.45 C6 0.22 H2O 0.07 Total 100.00
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