QUALIFICATION OF ADSORBED CHLORINATED SPECIES ON ASHES. ON-LINE ANALYSIS OF THE GAS PHASE RESULTING FROM POLLUTED ASHES
Laboratoire de Genie des Precedes Plasmas et Traitement de Surfaces, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05, France
Laboratoire Genie Precedes Plasmas - ENSCP 11, rue Pierre et Marie Curie - 75005 Paris- France
Laboratoire de Genie des Precedes Plasmas Universite P. et M. Curie, ENSCP 11 rue P. et M. Curie 75005 Paris France
The incineration of Municipal Solid Waste generates toxic products like fly ashes containing heavy metals and high chlorine compounds. The presence of these materials in the fly ashes makes their treatment and valorisation very difficult. In the present work, a radio frequency (13.56 MHz) low pressure plasma (<500 Pa) process has been developed in order to study the dynamic desorption of chlorinated compounds which lead to the formation of toxic species as dioxins. The chemical analyse of exhaust gases was performed on-line by mass spectrometry for the detection of traces. The chemical and physical evolution was performed by ex-situ analysis. The process allows to follow chlorinated rate and demonstrates the effect of the plasma that inhibited the formation of toxic compounds.
The hydrogen addition leads to a decrease of the reactive chlorine species and simultaneously, an increase of HCl. Also, experiments with a second fluidized bed of CaO were carried out to evaluate the competition between the trapping in HCl or in CaCl2. The simulation of these experiments shows the influence of different parameters in the formation of toxic products. The fluidized bed was modelled in order to show the process efficiency (spouted bed, chlorine desorption, HCl trapping). Polluted ashes qualification requires a real on-line toxic analysis process in order to treat desorbed species. Our process is a quite good solution to propose a better knowledge of the physical and chemical behaviour of pollutants.