Simulation and control of bench-scale distillation columns using a switched reflux strategy (original) (raw)

Control of reflux and reboil flow rates for milli and micro distillation

Chemical Engineering Research and Design, 2013

An accurate control of reflux and reboil flow rates for small scale distillation unit has been evaluated. Its feasibility was studied with a distillation column with good results. The distillation column was planar in shape, and it was operated in a horizontal orientation. Porous, open-cell metal foam was used as the column packing. The distillation unit could be operated at extremely low mass fluxes. The operation of the distillation unit was extremely stable, which was achieved thanks to the rigorous control of the fluid flow rates, and heat losses. The heat loss model was regressed based on distillation experiments with total reflux, and the model was used to optimize the temperature of the column shell in order to minimize the heat losses from the column. The volume of the reboiler, the preheaters, and the heat exchangers was minimized with the use of flat channels for intensified heat exchange. The total liquid holdup of the system was less than 40 cm 3 . The efficiency of the distillation unit was characterized for two binary and one ternary system.

Modeling and Control of Heat Integrated Distillation Columns: A Case Study

2012 ASEE Annual Conference & Exposition Proceedings

, Downtown. Tzouanas earned a diploma in chemical engineering from Aristotle University, a master's of science degree in chemical engineering/process control from the University of Alberta, and a doctorate of philosophy degree in chemical engineering/process control from Lehigh University. His research interests focus on process control systems, process modeling, and simulation. His industrial professional experience includes management and technical positions. He is a member of AIChE.

Tuning a Distillation Column Simulator

2011

A dynamic simulation model for binary distillation is presented. The model is based on mass, component and energy balances as well as pertinent expressions for the thermodynamic properties of the binary mixture. The model includes a total condenser, producing a reflux with a varying degree of subcooling, and a thermosyphon reboiler, which introduces several operating parameters. Parameters related to the operation of the condenser and the reboiler as well as tray efficiencies and heat losses from the column are determined by fitting to experimental data.

FLUID DYNAMIC MODEL AND CONTROL OF DISTILLATION COLUMN WITH DISTRIBUTED HEATING

Distillation columns require well adjusted control systems to quickly reject disturbances. To assist this purpose, a new distributed control strategy using electrical resistances on intermediate plates of a distillation column was proposed. A fluid dynamics study of the liquid vapor flow on the plates of a distillation column was conducted to improve understanding in microscopic level, of the mechanisms that occur in cases of separation and to evaluate the influence of resistance on the hydrodynamics of the trays. The data of the turbulent liquid vapor flow from the CFD technique encouraged the implementation of a control strategy with the use of resistances on the surfaces of the trays since the results showed that these do affect deleteriously tray hydrodynamics. In sequence, experimental studies were carried out, assessing the dynamics and control of a pilot scale distillation unit with the new design. The comparison of the experimental results with the distributed control (base, top and second tray of the column) with the results of a similar experiment carried out with the conventional approach (control at the base and top of column) showed that the distributed control led to a less oscillatory behavior and reduced the transition time.

A new approach to control distillation column: Use of intermediate action

Even a well adjusted control system of distillation process is not sufficient to eliminate the operation transients since this is an intrinsic feature of the process. One aspect that contributes to this situation is the centralization of the control action on the variables at the bottom and top of the column. In this work, a change in this control configuration is proposed through the introduction of heating points distributed among the trays throughout the column. The new approach was tested in a experimental distillation process where temperature feed disturbances occur with an ethanol-water mixture applying a conventional approach (control at bottom and top only) and the proposed distributed configuration (bottom, top and column trays). Results showed a significant reduction in the time required for the column to stabilize after the disturbance, if compared with the conventional approach, making faster dynamics possible.

Operation and experimental results on a vapor recompression pilot plant distillation column

Industrial & Engineering Chemistry Research, 1992

The open-loop steady-state and dynamic operation of a vapor recompression pilot-plant distillation column is studied under direct digital control of the loads to the process. Data acquisition, process control, and operator interface are programmed in a distributed control system. An ethanol-water mixture is separated. The manipulated inputs are cooling water flow rate and heat transferred a t the reboiler-condenser. Energy savings were of the order of 50% as compared to conventional distillation. The process presents quasi-linear stationary and dynamic behavior when subjected to small departures in heat input at the reboiler condenser. Time lags and delays are higher than in conventional distillation due to process interactions at the reboiler-condenser.

Optimal reflux rate policy determination for multicomponent batch distillation columns

Computers & Chemical Engineering, 1987

This paper describes a procedure to obtain optimal reflux or optimal distillate rate policy for multicomponent batch distillation columns using the Pontryagin's continuous maximum principle. For application to multicomponent systems, a reduced order model is used using short-cut procedure developed specifically for analysis and design of batch columns.

Distillation Column Process Control Strategies

2017

This review paper contains the control strategies used for the working of distillation and how they are applied using various formulae. It will also give a brief idea of what points a process engineer should keep in mind while deciding the control strategy. Through this paper, one would get to know the basic process control strategies and how to select a suitable strategy for the distillation column to work in the desired way.