Magnetic separation for a continuous solar-two-step thermochemical cycle for solar hydrogen/CO production using ferrites

A novel solar-two-step thermochemical concept for continuous production of H$$_2$$2 or CO from solar energy and H$$_2$$2O or CO$$_2$$2 using the redox pair MOFe$$_2$$2O$$_3$$3/MO as reactive particles is proposed and assessed. Here, an efficient continuous separation mechanism is devised by the use of an external magnetic field and the weak magnetization of MOFe$$_2$$2O$$_3$$3 at the working temperatures. The mechanism is suitable for systems of ferrites with a Curie temperature in the range 500–800 $$^{\circ }$$∘C where water or CO$$_2$$2 decomposition occurs. One of the most promising candidates is the Fe$$_3$$3O$$_4$$4/FeO system. Pyromagnetic coefficients for Fe$$_3$$3O$$_4$$4 were obtained experimentally. A simple magnetic trap was employed and the separation ratios Fe$$_3$$3O$$_4$$4/FeO were obtained. The results are encouraging and motivate the development of full-scale solar reactor prototypes. © 2015, The Author(s).