Alfons Buekens

Thermogravimetric desorption and de novo tests I: method development and validation.

Thermogravimetric analysis (TGA) has been combined with evolved gas analysis (EGA) with the purpose of simulating the thermal behaviour of filter dust samples under inert (desorption) and de novo test oxidising conditions. Emphasis is on studying de novo formation of dioxins, surrogates and precursors arising from filter dust derived from thermal processes, such as municipal solid waste incineration and metallurgy. A new method is tested for sampling and analysing dioxin surrogates and precursors in the TGA effluent, which are collected on sampling tubes; the adsorbed compounds are eventually desorbed and quantified by TD-GC-MS. The major sources of error and losses are considered, including potential sorbent artefacts, possible breakthrough of volatiles through sampling tubes, or eventual losses of semi-volatiles due to their incomplete desorption or re-condensation inside the TG Analyser. The method is optimised and validated for di- to hexa-chlorinated benzenes in a range of 10-1000 ppb with average recovery exceeding 85%. The results are compared with data obtained in similar studies, performed by other research groups. As a result, the method provides the means for simulating de novo synthesis of dioxins in fly-ash and facilitates reliable and easy estimation of de novo activity, comparable with results of other studies, in combination with wide flexibility of testing conditions.

Open burning as a source of dioxins

ABSTRACT This review critically collates data on the emissions of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like biphenyls (dl-PCBs), or in brief dioxins from a wide range of open burning sources. Open burning started raising attention in the nineties and has then been identified as one of the major global sources of dioxins, especially since evident guided emissions—principally from waste incineration and metallurgy—have been drastically curtailed. During combustion, dioxin emissions appear related to the proximate and ultimate analysis of the materials burning, to different combustion parameters (temperature, turbulence oxygen, etc.), to the successive phases in the development of a fire (flaming vs. smoldering), and to other factors influencing upon dioxins formation, such as heating, halogens, soot, ash, and catalytic transition metals. Although the roles of these factors are analyzed and discussed, they still remain difficult to evaluate and quantify, resulting in emission factor values ranging over several orders of magnitude, even after carefully controlled, repetitive experiments. Comprehensive comparisons of dioxins emission data are presented for both biogenic and anthropogenic sources, as well as some possible countermeasures toward reduction of dioxins from open burning.

Methods for Studying the de novo Formation of Dioxins at a Laboratory Scale

A new methodology is proposed for comparative study of filter dust samples regarding their organic load and their potency with respect to de novo synthesis (i.e. a catalytic oxidation of carbon and accompanying generation of dioxins, dioxin surrogates and precursors). It involves testing samples of filter dust, resulting from previous field studies, with the purpose of evaluating their original organic charge, as well as studying the details of carbon oxidation and associated formation of dioxin surrogates and precursors. Advantages as well as limitations of various test methods and applications, used in the study of dioxins at a laboratory scale are discussed.

Wood waste gasification as a source of energy

This paper relates to industrial experience and practical data in wood gasification, gathered in view of the construction of wood waste gasifiers. Two pilot plant gasifiers, coupled to a motor and a D.C. generator, have been erected and pilot tests have started recently.

CFD Modelling of Industrial Plant from a Viewpoint of Dioxins Formation

Design procedures of thermal industrial plant should take into account all aspects governing future plant emissions, in order to devise in due course all necessary primary (preventive) as well as secondary (curative) measures. For dioxin-sensitive operations, such as incineration and thermal metallurgical processes, the specific characteristics of dioxin formation and destruction should be carefully considered from the start. This means that different dioxin-relevant plant operating parameters, such as gas and particle flow, field of temperature, oxygen concentration and dust content of the off-gases, the residence times of entrained particles and — as far as possible — their contribution to dioxin formation should be established. The possibilities and limitations of the method are highlighted and a number of possible primary and secondary measures are presented.