Clinker based on calcium looped meals from the Cleanker Project.

The Cleanker (CLEAN clinKER production by Calcium Looping process) project, financed in the framework of Horizon 2020 EU funding program, has demonstrated the feasibility of the integrated CaL concept at industrial scale in a new demo system realised in the Buzzi Unicem cement plant in Vernasca (IT). The Calcium Looping (CaL) CO2 capture process exploits the reversible reaction of limestone calcination/carbonation (CaCO3 ↔ CaO + CO2). The Cleanker pilot plant consists of the coupling of a carbonator and an oxyfuel calciner. When the flue gases from kiln (containing CO2) flow through the carbonator together with calcined meal, which acts as a CO2 sorbent, carbonation takes place and CO2 is fixed in calcium carbonate. CaO is then regenerated in the calciner, where the opposite reaction takes place, and the captured CO2 is released. When the lime/limestone looping is carried out through a carbonator and a calciner operated in oxyfuel, a concentrated CO2 stream is obtained that can be efficiently addressed towards CCS or CCUS processes. In the Cleanker Project, the possibility to use raw meal for clinker production has been exploited and the meals sampled at the outlet of the oxyfuel calciner have been characterised and used for producing clinker at a lab scale. Calcium looped (CaL) meals collected at different sampling point during the operation of the CaL plant were characterised by means of X‐ray fluorescence spectroscopy, X‐ray diffraction and particle size distribution. Electron scanning microscopy revealed significant differences in the surface of particles of the looped meals with respect to the original one, resulting from the loading and unloading of CO2 during the looping cycles. The meals were burnt in a laboratory furnace and the obtained clinkers have been characterised on a chemical, mineralogical and microscopical point of view, revealing the good burnability of all the meals and attesting the possibility to reintegrate the materials in the clinker production process. A lower alite/belite ratio in the clinker produced from the looped meals was observed: actually, the depletion of calcium during the recirculation of the meal in the calciner/carbonator system led to a reduction of the lime saturation factor influencing the mineralogical composition of the product. LAY DESCRIPTION: The reduction of CO2 emission associated to cement production is a challenge of last decades, and it can be reached only combining the use of alternative materials (natural or recycled) with new innovative technologies. Within the Cleanker (CLEAN clinKER production by Calcium Looping process) project, a European project financed in the framework of Horizon 2020 EU funding program, a system called 'calcium looping process' was successfully integrated in the cement production technology. Calcium looping consists of using calcium oxide to adsorb diluted CO2 and release it in a more concentrate gas flow that can be subsequently captured and reused or stored. The great innovation in the Cleanker Project was to combine the calcium looping technology with the ordinary production of clinker. Moreover, the raw meal commonly used for clinker production was used as adsorber instead of calcium oxide, in such a way that all the materials involved in the looping were already originally part of the clinker production process. A pilot plant was realised in Italy, demonstrating the feasibility of the project. Few meals were collected during the trials of the plant and the paper presents the result of a study conducted in order to verify the possibility of using such meals for the production of ordinary Portland clinker. The results were encouraging: all the meals revealed very good burnability and the differences in the mineralogical composition of the clinkers could be ascribed to the composition of the meals, more than to the technological process they underwent. [ABSTRACT FROM AUTHOR]