PhD ceremony Mr. P. Krijgsman: Syntheses and destruction of compounds in supercritical water
|Fr 01-03-2013 at 14:30
PhD ceremony: Mr. P. Krijgsman, 14.30 uur, Academiegebouw, Broerstraat 5, Groningen
Dissertation: Syntheses and destruction of compounds in supercritical water
Promotor(s): Prof. F. Picchioni, Prof. M.W.M. Boesten, Prof. V.A. Mazur
Faculty: Mathematics and Natural Sciences
The aim at writing this thesis is, as partly stated in the acknowledgement, mainly three-fold , i.e.:
a) Try to introduce unique scientific ways that can be transferred into industrial applications serving mankind;
b) Stipulate the importance of water as a solvent, thereby emphasising the super critical domain (> 647 K and > 22.1 MPa);
c) The development of a process that functions both to create new materials (by means of syntheses) as well as an efficient, low cost process to destruct environmental hazardous compounds.
Chapter 1 is an introduction to the explanation of the super critical state of water and the ramifications about its extensive use in industry. It further elucidates the awareness of scientists at the end of the 18th century of capillary and the behaviour of water in nature and subsequently in industry. This lasted to the beginning of the 20th century when it, almost overnight, became a backwater of physics (page 28 of this thesis).
Furthermore, this chapter is a direct “hommage” to Johannes Diederik van der Waals, the contents not only are based on extensive literature search resulting in the production of a facsimile of his dissertation (from the original copy obtained from the library of the University of Leiden) that he defended on June 14, 1873, but also on the original text of the author of this thesis.
Out of a glossary of that, there remains much to be “said” (1.2.8 Preliminary Conclusion), I have chosen those topics that are signified with an asterix (*) and are covered in appendix 1 belonging to this chapter.
Chapter 2 is a three-fold division of aspects dealing with super critical water, i.e.:
a. behaviour of water in the super critical domain;
b. solubility of fluids in the super critical domain;
c. chemical equilibria and reaction kinetics in super critical water.
Appendix 1 to this chapter is an extension (continuation of application) of a prior, to the author, granted U. S. Patent (4,238,240 dated December 9, 1980) and subsequently to be followed by the granting of U. S. Patent (6,241,953 B1 dated June 5, 2001) and concerns with the automatic discharge of “loads” from a batch reactor. Ref. page 103, 2 “Description of the Related Art”.
Chapter 3 is confined to the hydrothermal formation of alpha aluminium oxide ( a -Al2 O3 ) using Bayerite/Gibbsite [Al(OH)3 ] via Boehmite [Al(OOH)] at a temperature > 673 K and a pressure > 33 MPa . Both Particle Size Distribution and X-Ray Diffraction analyses were carried out.
All aforementioned analyses were involved in the syntheses at both constant temperature and saturated steam pressure. This in spite of the fact that crystal growth is dependent on the residence time in the reactor. (this thesis, page 119, conclusions).
Chapter 4 is concerned with the hydrothermal formation of a mineral called Trevorite (NiFe2 O4 ).
Trevorite is formed on meteorites over a mere span of time exceeding hundreds of millions of years. It is a non-existing mineral on this globe; and it is scarcely found in those areas where meteorites struck the earth.
It is the first time that this very strong magnetic material was synthetically formed under supercritical conditions using water as a solvent and making use of standard available, though pure, bulk chemicals.
A historical review is given in the introduction of this chapter and is followed by the conditions based on which X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and Particle Size Distribution (PSD) analyses were obtained., whereas the theoretical saturation ( s s ) in emu.cm3 (Ms( versus temperature (K) for a poly-cristalline sample is depicted in figure.1 of this chapter.
Measurement, after compaction and sintering (under atmospheric conditions), of the real part ( m ’) and the imaginary part ( m ’’) as a function of frequency (kHz) is depicted in figure 1 of appendix 2 to this chapter This synthetic formation is elucidated by the granting of a U. S. Patent (6,416,682 B1, dated July 9, 2002). In addition, an extensive appraisal is given in appendix 3 of this chapter on the technical applications of magnetic materials in both civilian life and industry.
Chapter 5 involves the hydrothermal destruction of environmentally hazardous compounds of which the solutions, to remedy these shortcomings, are listed in the small brochure of Ceramic Oxides International B.V. and is handed to you with the thesis while being present. The contents of this chapter are given in the overall listings of this manuscript and are self explanatory.
Great emphasis is given to both the practical process conditions (in order to destroy unwanted compounds) and the physical design of the process. It is of paramount importance to establish a balance of the number of hazardous waste streams and the operating conditions. The aim is to design a multi functional process to be capable to handle a wide variety of unwanted compounds.
The design calculations are independently double checked by Prof. dr. ir. A. A. H. Drinkenburg from the Technical University of Eindhoven and Prof. dr. ir. J. de Graauw from the Technical University of Delft.
Recommendations made by a large variety of chemical and pharmaceutical companies have proven the viability of this process operating at supercritical conditions by means of a continuous plug flow reactor system.
Although initially calculated at an operating temperature of 673 K, recent results that a maximum of 773 K should be envisaged, this because of the carbon formation at the inside of the reactor-wall. One has to bear in mind that the operating conditions in a reactor take place in a stationary (low Reynolds number) environment, whereas in a continuous plug flow reactor the treatment is carried out under turbulent conditions that – when taking the necessary precautions – will yield a higher heat transfer coefficient.
Independent analyses carried out at Tauw Laboratories in Deventer, Netherlands, show a significant decrease in the amount of chemical oxygen demand (COD). In order to fully recuperate – and at the same time serving the environment – a modest subsequent treatment with either aerobic or anaerobic microbes would fulfill this demand.