Optimisation of recyclable beta plaster using plaster waste in a continuous reactor with a mobile helical element

Abstract

Experiments were performed to investigate optimised operational conditions for the production of recyclable plaster based on plaster waste from construction and demolition projects or the plasterboard industry in a continuous furnace with a mobile helical element on a bench scale. After the definition of the granulometry that provided the reaction conditions with no diffusive effects, a 22 rotational central composite design (CCRD) had been used for the experimental planning, where the factors of which were mean reactor temperature (148 °C and 162 °C) and gauge pressure (0.2–0.8 bar). The statistical analysis of the results based on the response surface methodology allowed the identification of the optimised operational conditions (162.4 °C and 0.5 bar). Under these conditions, the Avrami-Eurofe'ev equation was tested and confirmed (n = 2) for the kinetics of the thermal dehydration process. The capacity of the equipment to produce recyclable beta plaster was tested and confirmed by Scanning Electron Microscopy of the plaster crystals.