Minerals for Sustainable cost and energy efficient chemical looping combustion technology

The primary objectives of Mineral SCOUT are to combine and exchange knowledge on materials solutions for CLC technology between partners and scientifically support the CLC community by presenting results in publications and workshops/conferences. The secondary objectives are; 1) search for natural occurring and waste materials or development of suitable combinations (mixtures) of such materials with required properties/performance for utilization in CLC technology, 2) perform the necessary characterization needed to prove the quality and performance of the materials, 3) develop kinetic data that community can use for advanced modeling of the CLC system 4) develop recipes for up scaling up of selected materials with tailored physical properties.

The first task was to locate mineral with searched Mn-Fe compositions with more Fe than Mn or with other elemental compositions that can be expected to be thermodynamically favourable. Ten minerals have been initially chosen, ordered and prepared by mechanical preparation methods (mainly crushing, grinding and sieving)(NTUA). The selected materials were firstly introduced to a fast cycling tests in a TG in the temperature interval 800-1000oC (step 50oC) between 5% O2 and H2 (20 cycles) and then CH4 (20 cycles) total 240 cycles. This in order to scan the sources related to; capacity, relative kinetics and reactivity towards CH4 conversion. The best ones will now be further studied in detailed when it comes to reactivity and conversion of CH4 in small scale pulse reactor and further in different equipment to study direct oxygen release into inert atmosphere for enhanced gasification of coal (CPERI, SINTEF, IChPW). The oxygen release as a function of oxygen partial pressure will also be mapped to gain more detailed on materials properties. The best materials will also be checked on degradation after prolong testing as well as attrition testing. Deeper understanding of the degradation phenomena in minerals, given by cation diffusion, swelling and degradation due to mechanical attrition of the mineral particles during fast redox cycling introduced under CLC condition will also be searched (investigated). The attrition strength of the minerals will be investigated in a hot 3kW rig at SINTEF, designed exclusively for this purpose. Cambridge will work on coal – mineral interaction and modelling of this process, which will be compared to results in their experimental rig. A larger rig of 10kW at IChPW will be used to study combustion efficiency of at least one of the selected minerals. NTUA Mineral Processing Laboratory focuses on different mechanical preparation and processing routes for production of minerals into various size fractions suitable for use in the CLC process in large scale.

The largest challenge in the project has surprisingly been to procure minerals from the large producers of minerals that are mainly interested in selling 1000 of ton of materials. But luckily several of them have been possible to convince to send a small test batches.
The results so far is that two promising minerals have been found which need only to be crushed, ground and sieved in various size fractions. A third candidate material presents also promising properties but still needs more treatment. The results (obtained from the use of) gained on these materials will be published as fast as sufficient data have been collected on these materials.