Experimental device for dioxin vapour generation: A steady and adjustable source of gaseous 2,3-DCDD

摘要

PCDD/Fs are Persistent Organic Pollutants (POPs), generated by incomplete combustion of carbonaceous and chlorinated compounds. Because of their toxicity, they have to be monitored at emission, from stationary sources like waste incinerator. In the framework of the development of an on-line analyser, the laboratory prototype requires a gaseous dioxin source. We detail the principles of a dynamic generator based on the sublimation of solid sample and on the diffusion method. Such a device has to supply a polluted flow at steady and adjustable concentration of dioxin.The dioxin generation rate is determined by the weight loss of the solid sample. It is constant during time for temperatures ranging between 75 and 100 ℃ and for generation flow rates greater than or equal to 50 mL min~(-1). Variation of generation rate with temperature is predictable. With the increasing of temperature, emitted concentration increases while the increase of the inlet pressure decreases the concentration. Helium carrier gas leads to a higher generation rate than with N_2 in agreement with mass and molecular volume ratio. Thus, the outlet concentration and flow rate can be settled independently in the range of 3-100 ppm and 50-200 mL min~(-1).