Study of a solar installation for olive mill sludge treatment

•Higher drying air temperature was obtained by using parabolic trough solar collector.•The effective diffusivity variations related to the activation energy of the olive sludge were involved.•The developed drying chamber is improved by the optimization of trays distribution.•The drying kinetic to reach the moisture level needed for ulterior sludge valorization is enhanced.•Solar thermal energy supplied annually, leads to avoiding an important amount of CO2 emission. Olive mill sludge treatment was performed using a parabolic trough solar collector (PTC) to supply thermal energy. The proposed prototype, composed of a drying chamber coupled with a heat exchanger and a PTC, allows the treatment of up to 80 kg of wet olive oil pomace in about 1 hour and 40 min, the equivalent of 112 tons during the post-production period of olive oil. Due to the presence of oil, which delays evaporation, the drying process was studied at relatively high temperatures between 120 and 140 °C. The obtained results show that the effective diffusivities varied from 2.59 10−7 to 1.36 10−6 m²/s with an activation energy of 27.9 kJ/mol. The sludge dryer performance has also been analyzed and optimized numerically with MATLAB software. The indirect solar dryer using a PTC showed a relevant level of stability, fewer temperature fluctuations, and better control of the drying parameters compared to the direct solar dryer. The overall analysis reveals that the maximum thermal efficiency of 43% was recorded with total thermal energy produced throughout the year of 23,909 kWh, while the Levelized cost of heat was 0.34 $/kWhth. The proposed system leads to the avoidance of about 15,900 kg of CO2 emissions. [Display omitted]