Time-resolved monitoring of aromatic compounds in an experimental incinerator using an improved jet-resonance-enhanced multi-photon ionization system Jet-REMPI

Abstract

REMPI (Resonance Enhanced Multi-Photon Ionization) mass spectrometry has a large potential for continuous in-line monitoring, for example, in incineration. Through the introduction of Jet-REMPI, a sensitivity enhancement of several orders of magnitude can be achieved and this gives access to an increased number of compounds that are relevant for thermal processes, but further improvements are needed to exploit this multicomponent capability fully within reasonable measurement times. In order to scan over all relevant or accessible components, a tunable laser is needed capable of covering a wide wavelength range in a short time without the necessity of changing dyes or other means of adjustment. This wide laser wavelength range is demonstrated by measurements of laboratory spectra of some compounds typically found as PICs (products of incomplete combustion) along with an NO spectrum as an example of monitoring in the far UV. Further successful tests of the new monitor have been carried out in conjunction with an experimental incinerator. A nearly perfect match was found between the wavelength dependent spectra obtained with laboratory test gas mixtures and those in the incinerator flue gas. This apparent absence of interferences is the most important result of the present paper. Measurements conducted in parallel using conventional methods indicate a Jet-REMPI detection limit for 1,2 dichlorobenzene in the sub-ppt range.