ENGINEERING

1. ENGINEERING UAEU United Arab Emirates University College of Engineering Industrial Training and Graduation Project Unit Design and optimization of a fractionation unit Mariam Ali Albraiki Hanaa Saeed Al-Shamsi Lamya Lari Fatima Al-shehhi Advisor: Dr. Rachid Chebbi

2. Outline • Introduction. • Summary of GP1 • Objective of GP2 • Project units • Refrigeration unit • Fractionation unit • Sweetening unit

3. Refrigeration Separator Chiller Compressor Sweetening Heat exchanger Absorber Fractionation unit Distillation column • Sizing of the equipments • Cost of the plant • Conclusion

4. Introduction The project is about designing and optimizing fractionating plant in Al-Ruwais Fractionation Unit. Our target from the fractionation unit is to design and optimize a unit in order to separate the liquid components from natural gas into DEO, C3, butanes and C5+.

5. Summary of GP1 • Complete literature survey. • Two simulator packages were used simulate chemical processes such as : • HYSYS simulator used for the fractionation and refrigeration sections • ASPEN-PLUS used for sweetening section

6. Objectivres of GP2 • Design Fractionation Unit. • Design equipments of the Refrigeration and Sweetening Unit. • Determine efficiency of compressor and pump. • Estimate Fractionation, Refrigeration and Sweetening Units Cost. • Study Environmental Aspect.

7. Project units Refrigeration Fractionation Sweetening

8. Refrigeration unit

9. Fractionation unit

10. Sweetening unit

11. Refrigeration unit

12. Seperator Separation Process Separation process operates basically on the principle of pressure reduction to achieve the separation of gas from a liquid inlet stream.

13. Types of Separators Horizontal Separators Vertical Separators

14. Separator Sizing • Fluid physical properties required for sizing, were obtained form HYSYS simulator: • Density for liquid and vapor phases • Operating pressure • Volumetric flow rate of vapor and liquid phases • The settling velocity of liquid droplets • Relation between operating pressure and Lv/Dv

15. The liquid height : • The cross sectional area for vapor flow : • The vapor velocity : • Vapor residence time required for the droplets to settle to liquid surface : • Actual residence time: • The actual residence time is set equal to vapor residence time, and from this step , Dv, and Lv are determined.

16. Results

17. Chiller • Logarithmic mean temperature • The rate of heat transfer: • Heat transfer area was determined assuming U • Shell side heat transfer coefficient

18. Tube side heat transfer coefficient • Calculate Uo and compare it with the assumed U :

19. Compressor efficiency Definition of Compressor Compressors are described as mechanical device that takes in a gas and increases its pressure by squeezing volume of it into a smaller volume Types of Compressor • Reciprocating compressors • Centrifugal compressors • Axial flow compressors

20. Condition of the two compressors

21. 3.22 29023

22. 74 8.06

23. Efficiency of the two compressors

24. Fractionation unit

25. C2 C3 C4 De-ethanizer De-propanizer De-butanizer C5+

26. Type of trays The vapor area of the holes varies between 5 to 15% of the tray area Sieve tray In the sieve plate, vapor bubbles up through simple holes in the tray through the flowing liquid Hole sizes range from 3 to 12 mm in diameter, with 5 mm a common size

27. Bubble cap tray vapor or gas rises through the opening in the tray into bubble caps This type has been used over 100 years The gas flows through slots in the periphery of each cap and bubbles upward through the flowing liquid.

28. Valve tray modification of the sieve tray, they are essentially sieve plate with large diameter holes.

29. Tray efficiency stage efficiency is the performance of a practical contacting stage to the theoretical equilibrium stage. Murphree plate efficiency is the ratio of the actual separation achieved to that which would be achieved in an equilibrium stage

30. Design column • Calculate the maximum and minimum vapor and liquid rates which can be obtained from simulation results. • Collect the system physical properties from simulation results. • Select a trial plate spacing. • Estimate the column diameter based on flooding considerations.

31. Decide the liquid flow arrangement. Check the weeping rate. Check the pressure drop. Check downcomer back up. Recalculate the percentage flooding Check entrainment.

32. The liquid- vapor flow factor was determined for the top and bottom part using the following equation: Flv ( Top) = 0.359 Flv ( Bot) = 0.394 Where, Lw = Liquid mass flow rate in Kg/s Vw = Vapour mass flow rate in Kg/s Ρv = is the vapor mass density in Kg/m3 Ρl = is the liquid mass density in Kg/m3

33. From the graph ,it the KTop and KBotwere found as 8*10-2 and 7.6*10-2 respectively.

34. Next step was to correct the surface tension for top either bottom as shown below , from HYSYS simulator the surface tension are S Top = 2.771 *10-3 N/m S Bot = 2.155 *10-3 N/m K'Top = 0.0538 By using the equation K’Bot = 0.0486

35. Then the flooding velocity was estimated using the equation Where, u f is the flooding vapor velocity in m/s K' is the correction value for the surface tension in top and bottom part u fTop=0.1387 m/s u’ fTop=0.1178m/s With 85 % flooding u fBot=0.1387 m/s u’ fBot=0.097 m/s

36. In order to find the Maximum volumetric flow rate , the following equation was used V top =0.074 m3/s V bot=0.077 m3/s Where, Vw = Vapour mass flow rate in Kg/s Ρv = is the vapor mass density in Kg/m3 In this step , the net area was calculated using the following equation Top = 0.628 m2 Bot = 0.802 m2

37. In this part, it was assumed that the downcomer area is 12% from the total as a trial step , the column cross –sectional area are Top = Bot = = 0.713 m2 = 0.911 m2 Finally , the column diameter column at top and bottom D top =0.952 m Where, D is the column diameter in m A is the net area D bot =1.01 m

38. By taking all assumption as below Weir height = 50 mm Hole diameter = 5 mm Plate thickness = 5 mm Total pressure drop ht = hd +( hw+ how)+ hr 100 mm liquid

39. Weeping Actual minimum vapor velocity = = 0.709 m/s Downcomer liquid back up Back –up in downcomer was estimated by hb = (hw + how) + ht + hdc = 178 mm

40. Entrainment = = 0.0875 m/s Number of holes Area one hole = 1.964 *10-5 m2 Number of holes = = 3869.6 = 3870

41. Results

42. Sweetening unit

43. Heat exchanger description Device that facilitate the exchange of heat between two fluids that are at different temperature without allowing them to mix

44. Heat Exchanger Types Most heat exchangers are classified in one of several categories on the basis of configuration of the fluid flow path through heat exchanger. The most common types of flow path configuration are: • Double-Pipe Exchangers • Compact Exchangers • Shell and Tube Exchangers • Plate and Frame Exchangers • Regenerative Exchangers

45. Shell and Tube Exchanger The advantage of this type are: The configuration gives a large surface area in small volume Easily cleaned Can be constructed from a wide range of materials

47. General design consideration Fluid location: shell or tube Corrosive fluid Tube Fouling fluid Tube Higher temperature Tube Higher pressure Tube More viscous Shell Low Flow rate Shell

48. Shell and tube fluid velocities For Tube (1-2) m/s For Shell (0.3-1) m/s Stream temperature The closer the approach temperature used, the larger will be the heat transfer area required. Minimum approach temperature = 20oC Pressure drop Selection of pressure drop depends on the economical analysis that gives the lowest operating cost.

49. Heat Exchanger Design Shell-side T1=121 oC Baffle Spacing Bundle Diameter Shell Diameter Tube Diameter Tube-side t1=31 oC Tube-side t1=55 oC Shell-side T1=89 oC Tube Length Baffle

50. Physical properties needed for calculation: Heat Exchanger Design