Solar calcination at pilot scale in a continuous flow multistage horizontal fluidized bed
Thibaut Esence, Emmanuel Guillot, Michaël Tessonneaud, Jean‐Louis Sans, Gilles Flamant
Abstract
Calcination of limestone for lime production was successfully performed in the continuous flow mode on a daily basis in a fluidized bed indirectly heated by concentrated solar radiation. Industrial calcium carbonate feedstock was decomposed at the focus of the CNRS 1 MW solar furnace in a pilot-scale solar reactor operating at an average power of 55 kW. The reactor was a four-stage horizontal fluidized bed, irradiated on a front metallic wall of 1 m long and 0.4 m high. A novel aiming strategy was applied to reduce the hot spots on the irradiated wall. The conversion degree was analyzed as a function of the fluidization conditions (air mass flow rate) and the particle mass flow rate. This latter parameter varied in range (14.5 – 25 kg/h), and the highest conversion degrees were obtained at high fluidization velocity. The best result was obtained for a calcite mass flow rate of 20 kg/h, resulting in a degree of conversion of 95.2%, a BET surface area of the lime of 5.39 m2/g, and 17% and 29% thermochemical and thermal efficiencies of the reactor, respectively. This achievement corresponds to a particle mass flow rate three times higher than the current state of the art for solar calcination of lime.