Influence of asphalt composition upon the thermodynamics performance of a mixing plant

Abstract

Pavement material production requires a highly intensive energy processing related to the drying and the heating of granular materials within a rotary kiln. Thus, a better prediction of thermophysical parameters of bituminous concrete materials during their transformation is required to improve the processes in order to reduce their environmental impact. The present paper deals with accurate thermodynamics balance in a mix-asphalt plant. We report input and output mass flows captured within an instrumented flight rotary kiln devoted to a large range of asphalt materials. Hot-mix (T_materials ∼170°C), warm-mix (T_materials ∼120°C) and Recycled Asphalt Products (so-called RAP) are compared. Computation of the macroscopic energy balance exhibits an averaged energy flux source equal to about 7 MW, the major amount being connected to the power gas burner. The heat sink related to the drying is different according to the formulation, RAP particles having non-negligible moisture content. In situ temperature sensors are used to validate an advanced thermodynamics model involving RAP feeding rate. The thermal degradation of the RAP particles emphasises significant heat release measured at the RAP injection position which is captured by the theoretical model.

Keywords:

• bituminous binder
• self-ignition
• rotary kiln
• Recycled Asphalt Products
• feeding system

Acknowledgements

The authors thank Olivier Burban, Fabienne Farcas and Laeticia Van-Schoors for fruitful discussions. Special thanks are extended to the organisers of the workshop on construction and demolition waste recycling between 3 and 5 May 2015 at UFRGS at Porto Alegre, Brazil.

Disclosure statement

No potential conflict of interest was reported by the authors.