| 摘要 |
A method of producing sodium hydroxide from the waste water stream of the production process of fibre pulp, which stream comprises organic waste and sodium bound to it. According to the present method, the waste water stream is concentrated and then burnt under oxidising conditions, in order to break up the organic waste and the sodium compounds. According to the present invention, borate or a compound which forms borate, is added into the waste water stream, after which the sodium compounds are brought to an autocausticising reaction. The reaction is carried out at a temperature which is high enough to evaporate the sodium and the sodium is mainly in oxide form. The, at least partial, conversion of sodium carbonate into sodium hydroxide, according to the present invention, improves the usability of the alkali which is recovered for instance by using the Alrec process, which, in turn, lowers the costs of chemicals and reduces the energy consumption required for the def?bring of wood chips, which is subsequent to impregnation. |
