1. 1 INTERNATIONAL MARITIME COLLEGE OMAN PROCESS TECHNOLOGY & SYSTEMS (TPTS & PT-TPTS) PE (TPTS & PT-TPTS) (Chapter-3) Chapter - 3 Distillation Systems Textbook Reference: Process Technology Equipment & Systems by Charles E. Thomas

2. Distillation systems Contents: Principles of Distillation Two distillation examples Plate columns Plate distillation systems Packed columns PE (TPTS & PT-TPTS) (Chapter-3)2

3. Distillation Distillation involves boiling liquids & condensing the vapors The condensed liquid is referred to as the distillate The liquid that does not vaporize in a column is called the residue. PE (TPTS & PT-TPTS) (Chapter-3)3

4. Distillation Distillation is a process that separates the basic components or fractions of a mixture, as per their individual boiling points by boiling & condensation. During the distillation process, a mixture is heated until it vaporizes, then is re-condensed on the trays at various stages of the column PE (TPTS & PT-TPTS) (Chapter-3)4

5. Distillation column PE (TPTS & PT-TPTS) (Chapter-3)5 3 types of outputs

6. Systems of Distillation Unit A feed system A preheat system The distillation column The overhead system & The bottom system. PE (TPTS & PT-TPTS) (Chapter-3)6

7. Distillation Feed system blend & transfer the raw feed into the column. Feed system consists of tanks, pipes, valves, instrumentation & pumps. Preheating systems raise the temperature of the raw feed & bring to operating temperatures before it enters the distillation column. A shell & tube heat exchanger or a furnace is used. PE (TPTS & PT-TPTS) (Chapter-3)7

8. Distillation A distillation column is a tower with a series of trays or packing that provide contact points for the vapor and liquid. Plate columns have a series of trays stacked on top of each other. Packed columns are filled with packing material to enhance vapor-liquid contact. The function of each of these column types is to allow lighter components to rise up the column while heavier components drop down. PE (TPTS & PT-TPTS) (Chapter-3)8

9. Operation of Distillation tower Pre-heated feed enters the feed tray of the tower. Part of the mixture vaporizes as it enters the column, while the rest begins to drop into the lower sections of the tower. As vaporization occurs, the lighter components of the mixture move up the tower and are distributed on the various trays. PE (TPTS & PT-TPTS) (Chapter-3)9

10. Operation of Distillation tower The lightest component goes out the top of the tower in a vapor state and is passed over the cooling coils of a shell and tube condenser. As the hot vapor comes into contact with the coils, it condenses and is collected in the overhead accumulator. Part of this product is sent to storage while the rest is returned to the tower as reflux. PE (TPTS & PT-TPTS) (Chapter-3)10

11. Two Distillation Examples Ethanol and Water Distillation A mixture of 50% water and 50% ethanol can be separated through distillation. Ethanol boils at 78°C, and water boils at 100°C. As the mixture is heated, the ethanol vaporizes faster than the water. If the overhead vapors were analyzed, ethanol would make up the highest concentration. PE (TPTS & PT-TPTS) (Chapter-3)11

12. Two Distillation Examples Methanol and Water Distillation Methanol boils at 64.4°C, and water boils at 100°C. A 50/50 mixture, heated to 82°C to start the vaporization The vapor concentration would be 80% methanol and 20% water. This incomplete separation is called overlap. PE (TPTS & PT-TPTS) (Chapter-3)12

13. Two Distillation Examples The temperature at which this concentration is produced is referred as the effective cut point. If the mixture were heated to 100°C, both the methanol and water would vaporize, and a 50/50 vapor mixture would be obtained. PE (TPTS & PT-TPTS) (Chapter-3)13

14. Distillation columns (Tower) There are two types of distillation columns: – Plate or Tray column – Packed Column PE (TPTS & PT-TPTS) (Chapter-3)14

15. Plate or Tray column PE (TPTS & PT-TPTS) (Chapter-3)15

16. Plate or Tray column PE (TPTS & PT-TPTS) (Chapter-3)16 Diesel

17. Plate Column or Tray column The basic components of a plate column include: - the feed inlet - feed tray - rectifying or enriching section - stripping section - bottom & overhead outlet - reflux line - reboiler PE (TPTS & PT-TPTS) (Chapter-3)17

18. Plate Column Bubble-cap tray: These trays are most commonly used in distillation. This tray has many bubble-caps mounted on a riser, covered by liquid. As the vapor pressure increases from the bottom of the tower, the bubble-caps lift and allow a small amount of vapor through. PE (TPTS & PT-TPTS) (Chapter-3)18

19. Plate Column This vapor comes into direct contact with the liquid on the tray and transfers some heat energy. The liquid condenses the heavier components of the vapor, whereas the lighter components move up. A wire on the tray maintains a liquid level over the caps. PE (TPTS & PT-TPTS) (Chapter-3)19

20. Bubble cap tray PE (TPTS & PT-TPTS) (Chapter-3)20

21. Plate Column Sieve tray: Simplest type of tray. A sieve tray is a metal plate with small holes in it. As vapor comes through the holes, fast moving vapors stopped by the liquid level on the tray. PE (TPTS & PT-TPTS) (Chapter-3)21

22. Sieve tray-Plate tower PE (TPTS & PT-TPTS) (Chapter-3)22

23. Plate Column Valve tray: Have simple, movable plates. Plate movement depends on process flow. This type of tray is more efficient over a wider range of flow rates than the sieve tray. Each valve is a metal strip or a small metal disc that lifts under vapor pressure. PE (TPTS & PT-TPTS) (Chapter-3)23

24. Plate Column Rectifying or Enriching Section: A tower's rectifying or enriching section is located above the feed tray. The rectifying section of a tower has a higher concentration of light components than the stripping section has. PE (TPTS & PT-TPTS) (Chapter-3)24

25. Plate Column Stripping Section: The stripping section is located below the feed tray. When the hot feed drops from the feed tray to the lower trays, it heats up and strips the lighter components & heavier components flow to the bottom of the tower. Temperatures in the stripping section are usually much higher than in the rectifying section. PE (TPTS & PT-TPTS) (Chapter-3)25

26. Reboiler & Overhead condensor Reboiler Reboiler heats up the feed & is the main heat source for the separation processes. Kettle reboiler draw feed from the bottom section of the column by gravity. Bottom products enters the bottom shell side of a reboiler & gets heated up( steam inside the tube). PE (TPTS & PT-TPTS) (Chapter-3)26

27. Reboiler Designs PE (TPTS & PT-TPTS) (Chapter-3)27

28. Reboiler & Overhead condensor Overhead Condenser condensers are shell & tube heat exchangers which condenses the vapor, comes from the top of the column. The condensed liquid collects in an accumulator or drum. A pump splits the distillate to two locations. First one is to the product tanks or on for further processing; the second one is pumped back into the column as reflux. PE (TPTS & PT-TPTS) (Chapter-3)28

29. Plate Column Reflux: Distillation columns do not always work perfectly; Products from the tower usually have some composition overlap which can be controlled, by returning part of the overhead product to the tower. This process is referred to as refluxing, and the returned product is called reflux. PE (TPTS & PT-TPTS) (Chapter-3)29

30. Plate Column Reflux- Part of the Condensed distillation column product that is pumped back to the tower to increase product purity & control temperature. PE (TPTS & PT-TPTS) (Chapter-3)30

31. Packed Column Packed towers has specially designed packing materials in it, to provide more surface area, for maximum contact between gases and liquids. Liquids wet the surface of the packing as they migrate down the tower. Rising vapors come into contact with the wetted surface and exchange heat. PE (TPTS & PT-TPTS) (Chapter-3)31

32. Packed Column In a packed column, liquid travels down through feed distributors, hold-down grids, random and structured packing, support plates, redistributors, liquid collectors, structured grids, and finally into the bottom section. PE (TPTS & PT-TPTS) (Chapter-3)32

33. Packed Column 3 types of packing in a distillation column: Random, structured and stacked. Random packing contains pieces of packing that are randomly dumped or poured into a packed column. Structured packing has specific geometric shapes. Stacked packing has uniformly arranged packings inside a distillation column Typically, a combination of both random & structured type packing is normally used in a packed column. The packing inside a distillation column is supported by packing supports. PE (TPTS & PT-TPTS) (Chapter-3)33

34. Packing supports PE (TPTS & PT-TPTS) (Chapter-3)34

35. Common Packings PE (TPTS & PT-TPTS) (Chapter-3)35

36. Packed Column Bed Limiters &Hold-Down Plates: Bed limiters & hold-down plates keep fixed bed packing, from migrating or fluidizing out of the section. Hold-down plates rest on top of the packing, whereas bed limiters are attached to the inside wall of the column. PE (TPTS & PT-TPTS) (Chapter-3)36

37. Packed Column Liquid Distributor & Redistributor: Packed distillation columns use liquid distributors to disperse fluid evenly over the top of the packing, for more vapor liquid contac. Redistributor pulls the liquid off the walls & redirect into the centre. PE (TPTS & PT-TPTS) (Chapter-3)37

38. End of Chapter - 3 PE (TPTS & PT-TPTS) (Chapter-3)38