Ph.D. student Bernd Wittgens

Status

I started my Ph.D. work in spring 1990 and plan to finish by spring 1997. From 1990 to autumn 1994 I was financed by DEMINEX. Since autumn 1994 I have been employed at the department of Chemical Engineering as researcher assistant, this work includes supervision of laboratory exercises of third and fourth grade students.

Research area

The working title of my PhD. thesis is 'Experimental verification of robust control theory'. At the department a pilot plant distillation column is installed and offers the possibility of practical experiments on distillation column control. During the experimental work the following issues will be addressed:

• Validation of model assumptions regarding complexity of the model, simplification and assumptions on uncertainties.
• Controller design where different control types will be tested
• Control configurations and their performance on the given system
• Measurement types to interfere the product compositions.

The research area was extended to batch distillation columns, in particular the separation of multi-component mixtures of solvents, in a new type of distillation column.

Activities

Simulation:

• Developed rigorous dynamic model in Speedup with rigorous tray hydraulics of vapor and liquid flows, the thermodynamics properties are computed by means of the Aspen Properties Plus Package. Simplified models with a linearized tray hydraulic models are developed and used in simulation to investigate the effect of the assumptions made during linearization.
• Simulations of a newly developed multivessel batch distillation column for the separation of multicomponent mixtures. During the work, the feasibility of the process was shown and possible energy savings are investigated. A new method of controlling the column was developed which is capable of controlling the process properly.

Experimental:

• Experiments are performed to determine operational parameters of the continuous distillation column and compare/verify the simulation results and enable improvement of the empirical correlation's.
• A multivessel batch distillation pilot plant was designed and build. Experiments have been performed which show the operability of the process and verify the simulation results. The control structure developed in the simulation work was implemented on the pilot plant.

Work at the department:

• Supervision of Process-laboratory for third grade students
• Supervision a 4th grade student project on the evaporation of milk
• Supervision a 4th grade student project on the evaporation of milk
• Supervision and administration of the process control laboratory for 4th grade students.
• Supervision and administration process laboratory for Trondhjems Ingeniør Høgskole.
• Through the "Batch Project" for the production of Fine Chemicals, industrial contact to Borregaard Fine Chemicals, Norsk Hydro and Nycomed is established, in this program I am responsible for the experimental activities, including maintenance of analysis and distillation equipment.

Conference attendance:

• 6th NPC-Workshop (Nordic Workshop on Process Control) Aaland, Finland, August, 1995
• Dycord'95 4th Symposium on Dynamics and Control of Chemical Reactors, Distillation Columns and Batch Processes, June, 1995
• HCM Workshop, Workshop on Modeling and Control of Distillation Columns, University of Stuttgart, July 1995

Publications

• DYCORD'95; 'Evaluation of Dynamic Models of Distillation Columns with Emphasis on the Initial Response, 4'th Symposium on Dynamics and Control of Chemical Reactors, Distillation Columns and Batch Processes, June, 1995
• Multivessel Batch Distillation, American Institute of Chemical Engineering, 1995 Annual Meeting, November 12-17, 1995, Miami Beach, USA
• Multivessel Batch Distillation Column, HCM Workshop on Modeling and Control of Distillation Columns, July 1995, University of Stuttgart, Germany

Plans 1996

The work on the multivessel batch distillation column will be continued to investigate further features of the process including start-up and operation procedures. Experimental work on the continuous distillation column is planned to include evaluation of multivariable control structures. The work at the department will include the supervision and administration of the process laboratory of third grade students and the process control laboratory for the fourth grade course.