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Operation of a Multiple-Draw Distillation Column

5 days PSE/DSMSS-E
Level
Proficiency
Audience
  • Console operators in charge of multiple-draw-off columns, production supervisors, shift supervisors.
Purpose
  • To deepen understanding of the working principle and operational tuning of multiple-draw-off distillation columns through a hands-on experience.
Learning Objectives
  • To understand the main operating parameters of a multiple-draw-off distillation column.
  • To learn about the working principle and objectives of typical multi-draw column control loops.
  • To respond correctly and efficiently when faced with upset conditions and thus minimize product degradation.
Prerequisite
  • Participating to the course in "Distillation: Normal Operation, Optimization & Upsets" is recommended.
Ways and means
  • Use of a virtual column modeled on RSI IndissPlus dynamic simulator.

OPERATING PARAMETERS OF THE SIMULATED CRUDE DISTILLATION COLUMN 1 day
  • Analysis of the column: instrumentation, control loops, and analyzers. Analysis of various operating conditions and the significance of each operating parameter
  • Material balance, concepts of cut points, quality and fractionation capability
  • Total and partial pressures, pressure profiles along the column
  • Feed temperature, over flash and energy consumption
  • Role and operating parameters of the strippers, and stripping ratios
  • Energy balance, heat extraction by pumparounds, and partial condensation
  • Overhead condensation: and various control systems
  • Liquid and Vapor traffics, fractionation zone and heat transfer zones
  • Temperature profiles.
MODIFYING CUT POINTS 2 days
  • Control of the mass balance, and characteristics of the products.
  • Change in the side streams flow rates - Change in the overhead cut flow rate.
  • Practice changing the cut point between two side streams to meet quality specifications.
  • Tuning the operating parameters of the strippers; vapor, reboiling, stripping ratio, and flash point.
ADJUSTING ENERGY BALANCE 1 day
  • Modifying heat rates extracted by pumparounds: effects of changes to flow rates, internal traffics and properties of side streams.
  • Change in the transfer line temperature, and energy consumption. Influence of pressure and the consequence on feed heater and top degassing.
  • Consequence of changes to the energy balance, liquid and vapor traffics, and their effect on fractionation capability.
TUNING THE COLUMN 1 day
  • Adjusting the quality of the products.
  • Optimization criteria for the energy balance: adjustment of the pumparounds to get the desired fractionation capability.
  • Influence of the main disturbances: feed flow rate, stripping steam - Influence of a change in the crude oil quality.
  • Specific features of other multiple-draw columns like vacuum columns and fractionators.
SIMULATOR TRAINING
  • Exercises are conducted in small groups of 2 to 3 participants, each group operating its own virtual column. Each exercise includes: a pre-discussion of the problem; definition of the target exercise objective; adequate time to run the virtual columns; open analysis of the results, shared with all participants; and practical conclusions related to the operation of the columns.
  • Attendees are invited to bring descriptions of their specific column control strategies for group discussion and analysis. Conclusions drawn from the exercises on the simulator can be transposed to other actual control schemes.