The evaluation of dioxin emissions from pilot scale incineration of organochlorine compounds.

Formation of the dioxins was investigated in case of two fuel types (kerosene-dichlorobenzene and kerosene-dichloroethane) on a pilot scale liquid waste incinerator. It was determined the effect of the molecule structure (aromatic, aliphatic) and Cl content (1, 3 and 6%) of the liquids and the combustion parameters (O2 content, residence time and temperature). In some experiments particulate matters (fly ash and soot) were injected. The measured dioxin concentrations ranged up to 160 ng/Nm3 or till 10 ng/Nm3 TEQ, except at addition of soot where extremely high dioxin concentrations (up to 750 ng/Nm3, or 30 ng/Nm3 TEQ) were measured. Main conclusions of the experiment are: The incineration of aromatic chlorinated products produce almost 10 times higher dioxin concentrations than the aliphatic ones. A relatively low dioxin concentration is caused at low (1 to 3%) feed Cl contents while over a threshold value of more than 3% Cl intensifies sharply the dioxin formation. The dioxin generation can be characterized with concentrations measured at 600-650 degrees C. Dioxin toxicity reduction occurs when cooling down to 200-250 degrees C. Changes between these sampling temperatures can be explained mostly by sorption phenomena occurring between dioxin content of flue gases and solid deposits.

Analysis of metabolic systems with complex slow and fast dynamics.

We briefly review the results of other authors concerning the analysis of systems with time hierarchy, especially the Tikhonov theorem. A theorem, recently proved by the authors, making possible rigorous analysis of systems with complex fast dynamics is stated and discussed. A model example of a simple enzymatic reaction with product activation and slow (genetically driven) enzyme turnover is rigorously studied. It is shown that even in such a simple model there exist certain regions of parameters for which fast variables oscillate. Thus the classical Tikhonov theorem is not applicable here and we are forced to use another method--for example the author's presented theorem--or a purely numerical solution. These two methods are compared.

The role of metal ions in oxygen activation.

The reaction of oxygen with a common organic molecule is a spin-forbidden process catalyzed by transition metal ions. Some reactions of this type were proved to be trace metal catalyzed. It is therefore reasonable to assume that all reactions of molecular oxygen with organic molecules are induced by trace metals; in the absolute absence of transition metal ions these reactions would not proceed at all. Based on detailed studies of two well known oxygen reactions the mechanism of trace metal catalysis was formulated. The experimental results are consistent with the conception that transition metal ions associate with all species present in the system to form complexes or clusters of various composition and stability. Some of them are redox reactive and represent true intermediates of the catalyzed reaction.