Abstract: The present invention concerns a process for producing calcium carbonate from a calcium-containing alkaline slag material, the process containing the steps of extracting the alkaline slag material in a series of extraction steps, including at least 2 extraction steps, using extraction solvent(s) containing salt in an aqueous solution, whereby a calcium-containing filtrate and a residual slag is formed in each extraction step, separating the residual slag from the filtrate after each extraction step, carrying each residual slag to the following extraction in the series of extractions, to be used as raw material in said following extraction, and discarding the residual slag separated from the last extraction, carrying each filtrate to the previous extraction in the series of extractions, to be used as extraction solvent in said previous extraction, and carrying the first filtrate, separated from the first extraction step, to a carbonating step, carbonating calcium as calcium carbonate from the first filtrate

Abstract: The present invention concerns a process for producing calcium carbonate from a calcium-containing alkaline slag material, the process containing the steps of extracting the alkaline slag material in a series of extraction steps, including at least 2 extraction steps, using extraction solvent(s) containing salt in an aqueous solution, whereby a calcium-containing filtrate and a residual slag is formed in each extraction step, separating the residual slag from the filtrate after each extraction step, carrying each residual slag to the following extraction in the series of extractions, to be used as raw material in said following extraction, and discarding the residual slag separated from the last extraction, carrying each filtrate to the previous extraction in the series of extractions, to be used as extraction solvent in said previous extraction, and carrying the first filtrate, separated from the first extraction step, to a carbonating step, carbonating calcium as calcium carbonate from the first filtrate

Abstract: The present invention concerns a method for producing calcium carbonate containing the steps of extraction of alkaline industrial waste or by-products using as a first extraction solvent an aqueous solution of a salt formed from a weak acid and a weak base, whereby a vanadium-enriched first residue is allowed to settle and a calcium-rich first filtrate is formed, filtration, whereby the first filtrate is separated from the first residue, carbonation of the calcium-rich first filtrate using a carbonation gas, whereby calcium carbonate precipitates and a second filtrate is formed, and a second filtration, whereby the calcium carbonate is separated from the second filtrate. Further, the present invention concerns a method for extracting calcium carbonate and vanadium from alkaline industrial waste or by-products.

Abstract: The present invention concerns a method for producing calcium carbonate containing the steps of extraction of alkaline industrial waste or by-products using as a first extraction solvent an aqueous solution of a salt formed from a weak acid and a weak base, whereby a vanadium-enriched first residue is allowed to settle and a calcium-rich first filtrate is formed, filtration, whereby the first filtrate is separated from the first residue, carbonation of the calcium-rich first filtrate using a carbonation gas, whereby calcium carbonate precipitates and a second filtrate is formed, and a second filtration, whereby the calcium carbonate is separated from the second filtrate. Further, the present invention concerns a method for extracting calcium carbonate and vanadium from alkaline industrial waste or by-products.