Ph. D. programs

Ph. D. Programs

Optimal operation of polymer production and processing

Optimal grade switching
Optimal operation of polymer production is an interesting theme for research, especially when multiple products are manufactured. In this case optimal grade switching is of crucial importance, in order to reduce the production of twilight product. The goal of one project is to investigate quality control during normal operation and during product changeover in the pilot plant production of bi-modal polypropylene. Research topics include modeling of the molecular weight distribution and the design and implementation of quality control strategies for both types of operation.

Adaptive control strategies
A second project focuses on the development of non-linear multivariable (adaptive) control strategies for polymer production during start-up and normal operation. During the start-up phase the process dynamics change significantly and these changes have to be accounted for in the control strategy.

Multivariate statistical control techniques
A third project is the use of multivariate statistical process control techniques in order to achieve the desired improvements in polymer processing. The focus of this project is not to continue development of the MSPC technique, rather to define the boundary conditions for its successful application in the polymer industries. In addition, the statistical framework is integrated with fuzzy techniques in order to account for process non-linearities. The research developments are tested on the prediction of polymer properties in a polymer production process and on adjustment of an extrusion process for feeds with varying properties.

Optimal operation of membranes

Bastiaan Blankert & Edwin Zondervan

Membrane filtration is a promising technology in the field of water purification, because of its high selectivity and economic scalability. However, the performance of Ultra Filtration is limited by fouling. Consequently, periodic cleaning of the membrane is necessary. Currently, the process settings are based on rules of thumb and pilot plant studies. As the resulting settings are generally quite conservative, it is expected that operating costs can be significantly reduced by means of optimization.

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The goal of this research is to develop a complete, online, dynamic optimization system for the cyclic operation of Ultra Filtration installations, to attain maximal savings in operation costs over their entire lifetime.

Research topics:
The project can be divided in three subjects:
1) development of (hybrid) dynamic models, for fouling, cleaning and aging. These models are the basis for optimization and process data analysis;
2) optimizer. This includes development of the hierarchical control policy and adaptation at each level.
3) inspector. This consists of an ensemble of offline and online measurements, to support the control strategy.

Relevant Links:
Vitens | Aquacare | Hatenboer | Norit

Carbon reduction in steelmaking

Carolien kattenbelt

Introduction
Basic Oxygen Steelmaking (BOS) is one of the methods for making steel. Oxygen is blown into a furnace or BOS vessel, consequently oxidizing carbon and other unwanted elements.

Carbon is oxidized to carbon monoxide, which can, after cleaning, be used as fuel gas. Other elements are converted into acidic oxides, which produce slag. The oxidation process is exothermic and the temperature of the vessel increases during blowing. After the blow, which typically takes about 20 minutes, the carbon contents and the temperature of the steel should be at its specification and the vessel can be tapped.

Goal
The goal of this research is to develop online control of the carbon content and bath temperature in order to monitor the oxidation process.Furthermore, to increase production capacity, the process is dynamically optimized.

On-line measurements
For on-line control it is necessary to know how far operation is from set point. However, due to the high temperatures in the BOS vessel (1300- 1600 °C), obtaining direct measurements of bath temperature and carbon content is difficult. Hence, indirect measure-ments are being developed.

Indirect measurements are based on for instance:

· The quantity and the content of the fumes leaving the BOS vessel.

· The sound produced by the vessel.

Control strategy
Basic oxygen steelmaking is a batch process. In which raw materials are loaded into the vessel after which batch operation commences. In the control strategy this division is reflected.

1. A set-up model calculates the amount of raw materials to be used, based on heat and mass balances.
2. A dynamic model is being developed, to attain online control of the process.

Relevant Links:
Corus

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