Patent ID: 7731921

Claim:
A process for sequestration of carbon dioxide comprising the following steps: (a) dispersing solid waste material comprising calcium oxide and a calcium-comprising mixed oxide in water to dissolve at least part of the calcium oxide and to form calcium oxide-depleted solid waste material in a calcium hydroxide solution; (b) separating the calcium hydroxide solution from the calcium oxide-depleted solid waste material; (c) converting the calcium hydroxide in the separated calcium hydroxide solution into precipitated calcium carbonate; (d) contacting an aqueous slurry comprising water and from 10 to 50 wt % of the calcium oxide-depleted solid waste material with carbon dioxide to form an aqueous solution of calcium bicarbonate for mineral carbonation of the carbon dioxide to form carbonated solid waste material; (e) separating part or all of the aqueous solution of calcium bicarbonate from the carbonated solid waste material; (f) precipitating calcium carbonate from the separated aqueous solution of calcium bicarbonate; and (g) recovering the precipitated calcium carbonate as product; in which process the calcium carbonate is precipitated from the separated aqueous solution of calcium bicarbonate in step (f): (i) by adding calcium hydroxide from the solution obtained in step (b) to the separated aqueous solution of calcium bicarbonate; and/or (ii) by removal of carbon dioxide from the solution of calcium bicarbonate and wherein the carbon dioxide removed in step (f) is added to the calcium hydroxide solution in step (c).