Thermochemical cycles over redox structured reactors

Abstract

Structured bodies from redox materials are a key element for the implementation of thermochemical cycles on suitable reactors for the solar H 2 O splitting. In the current work different configurations of nickel ferrite were investigated with respect to their performance in H 2 O splitting: i) powder, ii) disk, iii) honeycomb flow-through monoliths. The structured bodies were prepared via pressing and extrusion techniques. The performance of the different structures was affected significantly by differences in the structural characteristics. Alternative approaches involving casting techniques for the structuring of nickel ferrite porous bodies were also investigated. This work constitutes a preliminary attempt towards tuning such characteristics to achieve enhanced and cycle-to-cycle stable production yields.

Hλιοθερμοχημικοί Αντιδραστήρες Για Παραγωγή Καυσίμων Με Ουδέτερο Αποτύπωμα Άνθρακα

“…This inactive mass acts as a large reservoir of oxygen in the internal area ( ) and oxidizes the surface via diffusion of oxygen from the internal region to the external. Examples in figures 2.8a-2.8c show the agreement between experimental and modelled results for monoliths extruded at 90cpsi (higher porosity), 150cpsi (medium to higher porosity) and 200cpsi (lower porosity, see [69]).…”

“…Three different structures (foam, extruded honeycomb monolith, cast monolith), consisting entirely of NiFe 2 O 4 , were evaluated in the tubular reactor installed in the high flux solar simulator [73]. Details on the synthesis and manufacturing techniques and physical characteristics of the various structures are described in detail in [69] and are presented here only briefly for completeness:…”

“…• a casting process for the structuring of NiFe 2 O 4 into honeycomb monolithic bodies employing specially fabricated molds via 3D-printing [69].…”

Green Synthetic Fuels: Renewable Routes for the Conversion of Non-Fossil Feedstocks into Gaseous Fuels and Their End Uses

“…The use of mixed metal oxides could decrease the reduction temperature required and increase the melting point. Mixed metal oxides are generated by the partial substitution of the primary materials with dopants including Mn, Co, Ni, YSZ and Zn for ferrite cycles [103][104][105][106][107][108], and Zr, Hf, La, Pr, Sm, Gd and Tb for ceria cycles [109][110][111][112][113]. The theoretical energy conversion efficiency of the iron oxide cycle is 39% and up to 75% by recuperating the high-temperature heat and 28% for un-doped ceria without heat recovery [114,115].…”

Nickel ferrite supported on calcium-stabilized zirconia for solar hydrogen production by two-step thermochemical water splitting

“…Previous works in the literature have shown the NiFe2O4 system as one of the most investigated composition with promising efficiency for H2 production via 2step water splitting thermochemical cycles [5]- [9] . The reduction and oxidation steps on NiFe2O4 have been also investigated and modelled via computational chemistry [10] and their structuration for use in solar reactors was also recently addressed [11] .…”