Process for the valorization of the lime muds from the causticizing cycle of the Kraft process

摘要

1. Process for the valorization of size slime in the causticization cycle for the preparation of Kraft pastes making it possible to recover a calcium carbonate more particularly usable as a paper couching pigment and comprising the operations of dissolving the salin by the weak white liquor resulting from the washing of the calcium carbonate, which leads to a green liquor, slaking of the quicklime, causticization, separation of the strong white liquor from the precipitate containing the calcium carbonate, washing the precipitate with water, recycling the weak white liquor and bleaching by the action of at least one oxidizing agent, characterized in that the green liquor is filtered at a temperature above 80 degrees C, the quicklime is slaked in the green liquor at a temperature of approximately 100 degrees C, the unboiled substances are eliminated prior to causticization, a granulometric fraction of the calcium carbonate in the white liquor, at a threshold of approximately 40 mu m, is carried out, if necessary, following causticization, the precipitate containing the sodium carbonate is washed with hot water, preferably at a temperature between 80 and 100 degrees C, the calcium carbonate is ground in at least one ball mill and the oxidizing agent for the bleaching is brought into the presence of the calcium carbonate before, during or after grinding.