1. Troubleshooting Distillation Simulations 398 1.1 VLE 398 1.2 Chemistry, Process Sequence 402 1.3 Does Your Distillation Simulation Reflect the Real World? 404 1.4 Graphical Techniques to Troubleshoot Simulations 407 1.5 How Good Is Your Efficiency Estimate? 407 1.6 Simulator Hydraulic Predictions: To Trust or Not to Trust 409 2.
Where Fractionation Goes Wrong 410 2.1 Insufficient Reflux or Stages; Pinches 410 2.2 No Stripping in Stripper 412 2.3 Unique Features of Multicomponent Distillation 412 2.4 Accumulation and Hiccups 413 2.5 Two Liquid Phases 419 2.6 Azeotropic and Extractive Distillation 421 3. Energy Savings and Thermal Effects 424 3.
1 Energy-Saving Designs and Operation 424 3.2 Subcooling: How It Impacts Towers 428 3.3 Superheat: How It Impacts Towers 430 4. Tower Sizing and Material Selection Affect Performance 431 4.1 Undersizing Trays and Downcomers 431 4.2 Oversizing Trays 431 4.3 Tray Details Can Bottleneck Towers 433 4.4 Low Liquid Loads Can Be Troublesome 434 4.
5 Special Bubble-Cap Tray Problems 436 4.6 Misting 437 4.7 Undersizing Packings 437 4.8 Systems Where Packings Perform Different from Expectations 437 4.9 Packed Bed Too Long 438 4.10 Packing Supports Can Bottleneck Towers 439 4.11 Packing Hold-downs Are Sometimes Troublesome 440 4.12 Internals Unique to Packed Towers 440 4.
13 Empty (Spray) Sections 440 5. Feed Entry Pitfalls in Tray Towers 441 5.1 Does the Feed Enter the Correct Tray? 441 5.2 Feed Pipes Obstructing Downcomer Entrance 441 5.3 Feed Flash Can Choke Downcomers 441 5.4 Subcooled Feeds, Refluxes Are Not Always Trouble Free 442 5.5 Liquid and Unsuitable Distributors Do Not Work with Flashing Feeds 442 5.6 Flashing Feeds Require More Space 443 5.
7 Uneven or Restrictive Liquid Split to Multipass Trays at Feeds and Pass Transitions 443 5.8 Oversized Feed Pipes 444 5.9 Plugged Distributor Holes 444 5.10 Low Î P Trays Require Decent Distribution 445 6. Packed-Tower Liquid Distributors: Number 6 on the Top 10 Malfunctions 446 6.1 Better Quality Distributors Improve Performance 446 6.2 Plugged Distributors Do Not Distribute Well 448 6.3 Overflow in Gravity Distributors: Death to Distribution 451 6.
4 Feed Pipe Entry and Predistributor Problems 454 6.5 Poor Flashing Feed Entry Bottleneck Towers 455 6.6 Oversized Weep Holes Generate Undesirable Distribution 456 6.7 Damaged Distributors Do Not Distribute Well 457 6.8 Hole Pattern and Liquid Heads Determine Irrigation Quality 458 6.9 Gravity Distributors Are Meant to Be Level 459 6.10 Hold-Down Can Interfere with Distribution 460 6.11 Liquid Mixing Is Needed in Large-Diameter Distributors 460 6.
12 Notched Distributors Have Unique Problems 461 6.13 Others 461 7. Vapor Maldistribution in Trays and Packings 462 7.1 Vapor Feed/Reboiler Return Maldistributes Vapor to Packing Above 462 7.2 Experiences with Vapor Inlet Distribution Baffles 465 7.3 Packing Vapor Maldistribution at Intermediate Feeds and Chimney Trays 465 7.4 Vapor Maldistribution Is Detrimental in Tray Towers 466 8. Tower Base Level and Reboiler Return: Number 2 on the Top 10 Malfunctions 468 8.
1 Causes of High Base Level 468 8.2 High Base Level Causes Premature Tower Flood (No Tray/Packing Damage) 470 8.3 High Base Liquid Level Causes Tray/Packing Damage 471 8.4 Impingement by the Reboiler Return Inlet 472 8.5 Undersized Bottom Feed Line 475 8.6 Low Base Liquid Level 475 8.7 Issues with Tower Base Baffles 476 8.8 Vortexing 476 9.
Chimney Tray Malfunctions: Part of Number 7 on the Top 10 Malfunctions 477 9.1 Leakage 477 9.2 Problem with Liquid Removal, Downcomers, or Overflows 478 9.3 Thermal Expansion Causing Warping, Out-of-Levelness 479 9.4 Chimneys Impeding Liquid Flow to Outlet 480 9.5 Vapor from Chimneys Interfering with Incoming Liquid 480 9.6 Level Measurement Problems 481 9.7 Coking, Fouling, Freezing 482 9.
8 Other Chimney Tray Issues 482 10. Drawoff Malfunctions (Non-Chimney Tray): Part of Number 7 on the Top 10 Malfunctions 484 10.1 Vapor Chokes Liquid Draw Lines 484 10.2 Leak at Draw Tray Starves Draw 486 10.3 Draw Pans and Draw Lines Plug Up 488 10.4 Draw Tray Damage Affects Draw Rates 488 10.5 Undersized Side-Stripper Overhead Lines Restrict Draw Rates 488 10.6 Degassed Draw Pan Liquid Initiates Downcomer Backup Flood 489 10.
7 Other Problems with Tower Liquid Draws 489 10.8 Liquid Entrainment in Vapor Side Draws 490 10.9 Reflux Drum Malfunctions 490 11. Tower Assembly Mishaps: Number 5 on the Top 10 Malfunctions 491 11.1 Incorrect Tray Assembly 491 11.2 Downcomer Clearance and Inlet Weir Malinstallation 491 11.3 Flow Passage Obstruction and Internals Misorientation at Tray Tower Feeds and Draws 492 11.4 Leaking Trays and Accumulator Trays 493 11.
5 Bolts, Nuts, Clamps 493 11.6 Manways/Hatchways Left Unbolted 493 11.7 Materials of Construction Inferior to Those Specified 494 11.8 Debris Left in Tower or Piping 494 11.9 Packing Assembly Mishaps 495 11.10 Fabrication and Installation Mishaps in Packing Distributors 496 11.11 Parts Not Fitting through Manholes 498 11.12 Auxiliary Heat Exchanger Fabrication and Assembly Mishaps 498 11.
13 Auxiliary Piping Assembly Mishaps 498 12. Difficulties during Start-Up, Shutdown, Commissioning, and Abnormal Operation: Number 4 on the Top 10 Malfunctions 499 12.1 Blinding/Unblinding Lines 499 12.2 Backflow 500 12.3 Dead-Pocket Accumulation and Release of Trapped Materials 501 12.4 Purging 501 12.5 Pressuring and Depressuring 502 12.6 Washing 502 12.
7 On-Line Washes 504 12.8 Steam and Water Operations 506 12.9 Overheating 506 12.10 Cooling 507 12.11 Overchilling 507 12.12 Water Removal 508 12.12.1 Draining at Low Points 508 12.
12.2 Oil Circulation 508 12.12.3 Condensation of Steam Purges 508 12.12.4 Dehydration by Other Procedures 508 12.13 Start-Up and Initial Operation 509 12.13.
1 Total-Reflux Operation 509 12.13.2 Adding Components That Smooth Start-Up 509 12.13.3 Siphoning 509 12.13.4 Pressure Control at Start-Up 510 12.14 Confined Space and Manhole Hazards 510 13.
Water-Induced Pressure Surges: Part of Number 3 on the Top 10 Malfunctions 512 13.1 Water in Feed and Slop 512 13.2 Accumulated Water in Transfer Line to Tower and in Heater Passes 513 13.3 Water Accumulation in Dead Pockets 513 13.4 Water Pockets in Pump or Spare Pump Lines 514 13.5 Undrained Stripping Steam Lines 515 13.6 Condensed Steam or Refluxed Water Reaching Hot Section 516 13.7 Oil Entering Water-Filled Region 517 14.
Explosions, Fires, and Chemical Releases: Number 10 on the Top 10 Malfunctions 518 14.1 Explosions Due to Decomposition Reactions 518 14.2 Explosions Due to Violent Reactions 523 14.3 Explosions and Fires Due to Line Fracture 524 14.4 Explosions Due to Trapped Hydrocarbon or Chemical Release 527 14.5 Explosions Induced by Commissioning Operations 528 14.6 Packing Fires 529 14.7 Fires Due to Opening Tower before Cooling or Combustible Removal 533 14.
8 Fires Caused by Backflow 534 14.9 Fires by Other Causes 535 14.10 Chemical Releases by Backflow 536 14.11 Trapped Chemicals Released 536 14.12 Relief, Venting, Draining, Blowdown to Atmosphere 537 15. Undesired Reactions in Towers 539 15.1 Excessive Bottom Temperature/Pressure 539 15.2 Hot Spots 539 15.
3 Concentration or Entry of Reactive Chemical 539 15.4 Chemicals from Commissioning 540 15.5 Catalyst Fines, Rust, Tower Materials Promote Reaction 540 15.6 Long Residence Times 541 15.7 Inhibitor Problems 541 15.8 Air Leaks Promote Tower Reactions 542 15.9 Impurity in Product Causes Reaction Downstream 542 16. Foaming 543 16.
1 What Causes or Promotes Foaming? 543 16.2 What Are Foams Sensitive To? 546 16.3 Laboratory Tests 547 16.4 Antifoam Injection 548 16.5 System Cleanup Mitigates Foaming 551 16.6 Hardware Changes Can Debottleneck Foaming Towers 555 17. The Tower as a Filter: Part A. Causes of Plugging--Number 1 on the Top 10 Malfunctions 558 17.
1 Piping Scale/Corrosion Products 558 17.2 Salting Out/Precipitation 559 17.3 Polymer/Reaction Products 560 17.4 Solids/Entrainment in the Feed 561 17.5 Oil Leak 561 17.6 Poor Shutdown Wash/Flush 562 17.7 Entrainment or Drying at Low Liquid Rates 562 17.8 Others 562 18.
The Tower as a Filter: Part B. Locations of Plugging--Number 1 on the Top 10 Malfunctions 563 18.1 Trays 563 18.2 Downcomers 564 18.3 Packings 565 18.4 How Packings and Trays Compare on Plugging Resistance 565 18.5 Limited Zone Only 567 18.6 Draw, Exchanger, and Vent Lines 569 18.
7 Feed and Inlet Lines 570 18.8 Instrument Lines 570 19. Coking: Part of Number 1 on Tower Top 10 Malfunctions 571 19.1 Insufficient Wash Flow Rate, Refinery Vacuum Towers 571 19.2 Other Causes, Re.