초록 ▼

Flue gases exhausted from a lime kiln containing lime kiln dust are treated to produce a high purity calcium carbonate precipitate. This is accomplished by passing the flue gases from the lime kiln through a kiln dust separator so that lime kiln dust containing calcium oxide is removed from the rema

Flue gases exhausted from a lime kiln containing lime kiln dust are treated to produce a high purity calcium carbonate precipitate. This is accomplished by passing the flue gases from the lime kiln through a kiln dust separator so that lime kiln dust containing calcium oxide is removed from the remaining flue gas. The lime kiln dust is mixed with water so that an aqueous suspension of the lime kiln dust is formed. Quicklime or calcium oxide in the lime kiln dust is thus hydrated to form calcium hydroxide. The solids within the suspension are then allowed to settle so that a clear, saturated solution of calcium hydroxide having a pH of about 12.4 is formed. This solution is then contacted with carbon dioxide gas so that the calcium hydroxide reacts to form a high purity calcium carbonate precipitate. This high purity calcium carbonate precipitate is then allowed to settle from supernatant water of the solution. The high purity calcium carbonate is separated from the supernatant water, while the supernatant water is used as the water mixed with the lime kiln dust to form the aqueous suspension.

대표청구항 ▼

[ What is claimed is:] [1.] A method of producing high purity calcium carbonate, the method consisting essentially of:combining a source of calcium oxide or calcium hydroxide with water to form an aqueous suspension;allowing the calcium oxide in the aqueous suspension to hydrate to form calcium hydr

[ What is claimed is:] [1.] A method of producing high purity calcium carbonate, the method consisting essentially of:combining a source of calcium oxide or calcium hydroxide with water to form an aqueous suspension;allowing the calcium oxide in the aqueous suspension to hydrate to form calcium hydroxide;allowing solids within the suspension to settle so that the remaining supernatant water consists essentially of a clear, saturated solution of calcium hydroxide;contacting the supernatant water which consists essentially of the clear, saturated solution of calcium hydroxide with carbon dioxide gas so that the calcium hydroxide reacts with the carbon dioxide to form a high purity calcium carbonate precipitate;allowing the high purity calcium carbonate precipitate to settle from supernatant water of the solution; and thenseparating the high purity calcium carbonate from the supernatant water. [15.] A method of treating flue gases containing lime kiln dust exhausted from a lime kiln to produce high purity calcium carbonate having a generally cuboidal-shaped crystalline structure, the method comprising:passing flue gases exhausted from the lime kiln through a kiln dust separator so that lime kiln dust containing calcium oxide is removed from the flue gas;mixing the lime kiln dust with water so that an aqueous suspension of the lime kiln dust is formed, and wherein the calcium oxide in the lime kiln dust is hydrated to form calcium hydroxide;allowing solids within the suspension to settle so that a clear, saturated solution of calcium hydroxide having a pH of about 12.4 is formed;contacting the clear, saturated solution of calcium hydroxide with carbon dioxide gas so that the calcium hydroxide reacts with the carbon dioxide to form a high purity calcium carbonate precipitate in the form of particles having a generally cuboidal-shaped crystalline structure;allowing the high purity calcium carbonate precipitate to settle from supernatant water of the solution; thenseparating the high purity calcium carbonate precipitate from the supernatant water; and thenrecycling the supernatant water as the water mixed with the lime kiln dust to form the aqueous suspension. The method of claim 15, wherein:the solution of calcium hydroxide is contacted with carbon dioxide until the pH of the solution reaches about 8.0. The method of claim 15, wherein:the lime kiln dust separator is a wet scrubber and the lime kiln dust is mixed with water from the wet scrubber to form the suspension. The method of claim 15, wherein:at least 90% of the calcium carbonate precipitate has a particle size ranging between about 2 to 10 microns. The method of claim 15, wherein:the high purity calcium carbonate precipitate contains less than 1% impurities.