Process for preventing scaling of heat transfer surfaces

Details Process for preventing scaling of heat transfer surfaces Process for preventing scaling of heat transfer surfaces

D - Textiles, Paper

21

C

D21C 3/22 (2006.01) D21C 1/00 (2006.01) D21C 11/10 (2006.01)

Patent

CA 2381414

In a batch process for kraft pulp production, fouling of heat transfer surfaces is reduced. The first impregnation liquor withdrawn from the digester is rich in dissolved calcium-containing material. This material, when heated, releases calcium which forms calcium carbonate. If this heating takes place at a heat exchanger surface, severe scaling may result. According to the invention, the calcium-rich liquor is introduced into the digester as an early displacement liquor following a finished cook. As the digester temperature is high at this process stage, the calcium-containing dissolved material breaks down and calcium carbonate precipitation takes place in the pulp in the digester, where scaling of heat transfer surfaces cannot occur.

L'invention concerne un procédé discontinu de production de pâte kraft dans lequel on réduit les dépôts de tartre sur les surfaces d'échange thermique. La première liqueur d'imprégnation, retirée à partir du lessiveur, est riche en matériau dissous contenant du calcium. Ce matériau, lorsqu'on le chauffe, libère le calcium, lequel forme du carbonate de calcium. Si le chauffage s'effectue au niveau d'une surface d'échange thermique, il peut en résulter un entartrage important de celle-ci. Selon l'invention, on introduit la liqueur riche en calcium dans le lessiveur, en tant que liqueur de chasse, après terminaison d'une cuisson. Etant donné que la température du lessiveur est élevée au niveau de cette étape du procédé, le matériau dissous contenant le calcium se décompose et le carbonate de calcium se précipite dans la pâte, dans le lessiveur, de sorte qu'il ne peut pas se produire d'entartrage des surfaces d'échange thermique.

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