The production of calcium oxide and barium sulphide from mixtures including calcium carbonate, barium sulphate, barium carbonate and calcium hydroxide

摘要

Calcium oxide and barium sulphide are prepared by heating a mixture including calcium PICT:0897589/III/1 carbonate, calcium hydroxide, barium sulphate and barium carbonate in a single reduction zone at a temperature between 700 DEG C. and 1,150 DEG C., with a reducing agent capable of reducing barium sulphate to barium sulphide, for example, a mixture of carbon and water, carbon monoxide, hydrogen, methane, or a carbon monoxide-hydrogen mixture. The process may be employed in the regeneration of alkaline sulphide pulping liquors from black liquors containing sodium hydroxide, sulphide, sulphate and carbonate, by oxidizing the black liquor to destroy organic matter therein, and to convert the sodium salts to the sulphate and carbonate by heating under pressure sufficient to maintain at least part of the reaction mixture in the liquid phase at elevated temperature with sufficient oxygen to convert the carbon to carbon dioxide and all the hydrogen to steam; adding a recycled previously kilned mixture of barium sulphide containing barium carbonate and calcium oxide to the resultant oxidized liquor to precipitate barium sulphate, barium carbonate, calcium hydroxide and calcium carbonate, which precipitate is separated from the supernatant regenerated liquor; and treating the precipitate by the process of the invention, which may then be used for further regenerations. The accompanying flow-sheet illustrates a cyclic process for pulping wood employing the regeneration treatment. Specifications 706,686 and 757,964 are referred to.ALSO:PICT:0897589/IV (a)/1 Calcium oxide and barium sulphide are prepared by heating a mixture including calcium carbonate, calcium hydroxide, barium sulphate and barium carbonate in a single reduction zone, at a temperature between 700 DEG C. and 1150 DEG C., with a reducing agent capable of reducing barium sulphate to barium sulphide, for example a mixture of carbon and water, carbon monoxide, hydrogen, methane or a carbon monoxide-hydrogen mixture. The process may be employed in the regeneration of alkaline sulphide pulping liquors from black liquors containing sodium hydroxide, sulphide, sulphate and carbonate, by (1) oxidizing the black liquor to destroy organic matter therein, and to convert the sodium salts to the sulphate and carbonate, by heating under pressure sufficient to maintain at least part of the reaction mixture in the liquid phase at elevated temperature with sufficient oxygen to convert the carbon to carbon dioxide and all the hydrogen to steam. (2) adding a recycled previously kilned mixture of barium sulphide containing barium carbonate and calcium oxide to the resultant oxidized liquor to precipitate barium sulphate, barium carbonate, calcium hydroxide and calcium carbonate, which precipitate is separated from the supernatant regenerated liquor; and (3) treating the precipitate by the process of the invention to give a product which may then be used for further regeneration. The flow-sheet (not shown) illustrates a cyclic process for pulping wood employing the regeneration treatment. Specifications 706,686 and 757,964 are referred to.