Industrial symbiosis for improving the CO 2 - performance of cement production - Final report of the
We developed the solar chemical reactor technology to effect the endothermic calcination reaction CaCO3 → CaO + CO2 at 1200-1400 K. The indirect heating 10 kW multi-tube rotary kiln prototype processed 1-5 mm limestone particles, producing high purity lime that is not contaminated with combustion by-products. The quality of the solar produced quicklime meets highest industrial standards in terms of reactivity (low, medium, and high) and degree of calcination (exceeding 98%). The reactor’s chemical efficiency, defined as the enthalpy of the calcination reaction at ambient temperature (3184 kJ kg) divided by the solar energy input, reached 30-35% for quicklime production rates up to 4 kg h. The solar lime reactor prototype operated reliably for more than 100 hours at solar flux inputs of about 2000 kW m, withstanding the thermal shocks that occur in solar high temperature applications. By substituting concentrated solar energy for fossil fuels as the source of process heat, one can reduce by 20% the CO2 emissions in a state-of-the-art lime plant and by 40% in a conventional cement plant. The cost of solar lime produced in a 20 MWth industrial solar calcination plant is estimated in the range 131-158 $/t, i.e. about 2-3 times the current selling price of conventional lime.