Development of Compartment Models for Diagnostic Purposes

The importance of recognizing the presence of process faults and resolving these faults is continuously increasing parallel to the development of industrial processes. Fault detection methods which are both robust and sensitive help to recognize the presence of faults in time to avoid malfunctions, financial loss, environmental damage or loss of human life. In the literature, the use of various model-based fault detection methods has gained a considerable degree of popularity. Methods usually based on black-box models, data-based techniques or models using symbolic logic, e.g.\ expert systems, have become widespread. White-box models, on the other hand, have been applied less despite their considerable robustness because of multiple reasons. Firstly, their complexity and the relatively vast amount of technological and modelling knowledge needed to construct them for industrial systems. Secondly, their large computational demand which makes them less suitable for online fault detection. In this study, the aim was to resolve these problems by developing a method to simplify the complex Computational Fluid Dynamics models employed to describe the equipment used in the chemical industry into less complex model structures. These simpler structures are Compartment Models, a type of white-box model which breaks down a complex system into smaller units with idealized behaviour. In the case of a small number of compartments, the computational load of such models is not significant, therefore, they can be employed for the purposes of online fault detection while providing an accurate representation of the system. For the purpose of identifying the compartmental structure, fuzzy logic was employed to create a model which approximates the real behaviour of the system as accurately as possible. Our future objective is to explore the possibility of combining this model with various diagnostic methods (expert systems, Bayesian networks, parity relations, etc.) and derive robust tools for the purpose of fault detection.

Modelling of the Pyrolysis Zone of a Downdraft Gasification Reactor

The increasing amount of municipal solid waste (MSW) is a growing challenge that current waste-treatment practices are having to face. Therefore, technologies that can prevent waste from ending up in landfill sites have come to the fore. One of the technologies that produces a valuable product from waste, namely synthesis gas, is gasification. The raw material of this technology is the so-called Refuse-Derived Fuel, which is made from MSW. Three separate zones are located in downdraft gasification reactors: the pyrolysis, oxidation and reduction zones. This work is concerned with the determination of kinetic parameters in the pyrolysis zone. It also discusses the estimation of the product composition of this zone, which defines the raw material of the following zone.

Micropreparative fraction collection in microfluidic devices

Micropreparative fraction collection following microchip-based electrophoretic analysis of biomolecules is of major importance for a variety of biomedical applications. In this paper, we present a microfabricated device-based fraction collection system. Various size DNA fragments were separated and collected by simply redirecting the desired portions of the detected sample zones to corresponding collection wells using appropriate voltage manipulations. The efficiency of sampling and collection of the fractions was enhanced by placing a cross channel at or downstream of the detection point. Following the detection of the band of interest, the potentials were reconfigured to sampling/collection mode, so that the selected sample zone migrated to the appropriate collection well of the microdevice. The potential distribution assured that the rest of the analyte components in the separation column was retarded, stopped, or reversed, increasing in this way the spacing between the sample zone being collected and the immediately following one. By this means, a precise collection of spatially close consecutive bands could be facilitated. Once the target sample fraction reached the corresponding collection well, the potentials were switched back to separation mode. Alternation of the separation/detection and sampling/collection cycles was repeated until all required sample zones were physically isolated. The integrated device consists of a sample introduction, separation, fraction sampling, and fraction collection compartments. The feasibility of the fraction collection technique was tested on a mixture of dsDNA fragments. The amounts of DNA collected in this way were enough for further downstream sample processing, such as conventional PCR-based analysis.

Microfabricated devices in biotechnology and biochemical processing

In the past few years, interdisciplinary science and technologies have converged to create exciting challenges and opportunities, which involve a new generation of integrated microfabricated devices. These new devices are referred to as 'lab-on-a-chip' or Micro Total Analysis Systems. Their development involves both established and evolving technologies, which include microlithography, micromachining, Micro Electro Mechanical Systems technology, microfluidics and nanotechnology. This review summarizes the key device subject areas and the basic interdisciplinary technologies, and gives a better understanding of how these technologies can be used to provide appropriate technical solutions to fundamental problems. Important applications for this novel 'synergized' technology in chemical and biotechnological processing, in addition to the application of simulation methods in the development of microfabricated devices, will also be discussed.