Method and device for carbonation

A method for converting a starting material containing waste materials and/or by-products, selected from the group consisting of concrete demolition waste, material left over from concreting, slag, ash, muds, and mixtures thereof, wherein the starting material contains at least 40 wt.-% of calcium silicon (hydr)oxide phases and calcium aluminum (hydr)oxide phases, said phases being selected from the group consisting of calcium silicon hydrates, alite, belite, rankinite, wollastonite, hydrogarnet, ettringite, calcium aluminum hydrates, calcium silicon/aluminum (hydr)oxides with additional elements, and mixtures thereof, into an SiO2 rich supplementary cementitious material and a calcium carbonate additive comprising the steps of:

• providing the starting material with a D90 of ≤1 mm;
• mixing the starting material with water or adjusting a water content of the starting material to provide a starting material slurry having a solid:
• liquid ratio from 2:1 to 1:100;
• passing the starting material slurry into a gravity separation reactor together with carbon dioxide;
• subjecting the starting material slurry and carbon dioxide to centrifugal motion provided by adjusting a rotational speed to range from 10,000 to 150,000 rev min-inside the reactor;
• and
• removing a heavy slurry of higher density particles comprising the calcium carbonate additive formed by reaction of carbon dioxide with calcium ions dissolved or leached from the starting material from a first outlet of the reactor, removing a light slurry of lower density particles comprising the undissolved SiO2 rich remains of the starting material from a second outlet of the reactor, and removing liquid from a third outlet of the reactor.