Reduction at source of PAHs during pyrolysis operations

Polycyclic Aromatic Hyrocarbons (PAHs) are chemical compounds that are sometimes highly toxic, or indeed that are considered by some to be proved carcinogens. A variety of sectors of activity cause PAH emissions: incineration, pyrolysis, diesel engines, petrochemicals, or coking plants.

The main objective of this study is to limit exposure to PAHs for workers doing maintenance operations on facilities in which pyrolysis reactions have taken place. The aim is to change the core of the process by treating the pollutant “at source” while also guaranteeing the quality of the industrial products that are manufactured. For this purpose, it is necessary to improve knowledge about the parameters that influence emissions of the various PAHs in pyrolysis reactors in order to determine the operating conditions (thermodynamic and kinetic conditions), and the geometrical configurations of the process so as to minimise formation of the PAHs.

A first part of the work will be to model a pyrolysis oven by incorporating the radical kinetic models of all of the reactions involved. In parallel, a study will be conducted on the structure of the ovens and on how their insides are fitted out. The idea is to apply process intensification methodology to gas-solid catalytic reactions and to find space and time scales that make it possible to reduce PAH generation. The work will be conducted in partnership with CNRS. Finally, the kinetic models will be validated experimentally at the scale of the laboratory on the INRS site, and on an industrial pilot of an SME specialised in designing carburising furnaces.

The results obtained at the end of the study will make it possible to develop a methodology that will take account of the developments in new technologies, of the occupational health constraints, and of the financial possibilities of the industrial companies. It will then be possible for this methodology aimed at treating worker exposure at source to be applied to other pyrolysis operations such as atmosphere carburising, carbonitriding, and, beyond that, to combustion phenomena.

Planned dissemination: Presentations and publications will be produced nationally and internationally. As regards occupational safety and health, articles will be written to inform the occupational medicine services, the OSH networks, the managers, and the health, safety and working conditions committees (CHSCTs) of the various industrial sites in question.