Abstract: An aqueous solution containing sulphur dioxide and sodium in high percentages is obtained by bringing sulphur dioxide into contact with a recirculating aqueous solution of sodium hydroxide and previously absorbed sulphur dioxide to obtain a ratio between SO.sub.2 and the sum of SO.sub.2 and Na.sub.2 O of 0.61-0.66, preferably 0.63-0.65, and a concentration of SO.sub.2 and Na.sub.2 O amounting to 85-98%, preferably about 95% of the solubility maximum of the solution at the ratio and storage temperature in question.The invention also relates to a solution having the aforesaid ratio of SO.sub.2 /(SO.sub.2 +Na.sub.2 O) and concentation and its use for sulphite cooking purposes or for bleaching purposes.

Abstract: The present invention relates to a method of recovering chemicals from spent liquors while at the same time utilizing energy liberated during the process. The spent liquors are gasified and partially disintegrated in a reactor (1), external thermal energy independent of combustion being simultaneously supplied to the reaction zone (2) of the reactor, after which the resultant melt is separated (at 9) at substantially the temperature prevailing at combustion, the gaseous product thereby formed being quenched in a quenching and cooling zone (6), to a temperature below 950.degree. C. A product gas is thus obtained which contains substantially no sulphur impurities, an alkali product with high sulphide content and an alkali product substantially free from sulphide and having low Na.sub.2 CO.sub.3 content.

Abstract: The present invention relates to a method and means of increasing capacity and improving the chemical recovery process when using a conventional soda recovery boiler for recovering chemicals out of spent sulphate liquors. The spent sulphate liquor is supplied in full or in part to a liquor gasifier (8) while external energy independent of combustion is simultaneously supplied (at 16, 17). The temperature and oxygen potential are carefully controlled independently of each other by means of controlled supply of the energy. The product thus obtained is thereafter introduced in full or in part into a soda recovery boiler (1).

Abstract: The invention relates to the recovery of chemicals from waste liquor from wood pulp process, primarily black liquor, while utilizing energy liberated. Controlled total vaporization of the pulp waste liquor at high temperature and low oxygen potential is achieved by the external supply of energy. During the subsequent condensation and separation of melt or water solution is obtained which, without causticizing, can be used for the preparation of white liquor, and also an energy rich gas and mainly free from sulphur, consisting primarily of carbon monoxide and hydrogen.

Abstract: There is provided a method for producing compositions which can be used for preparing sodium dithionite, in which sulphur dioxide is brought into contact with a recirculating aqueous solution of sodium hydroxide and previously absorbed sulphur dioxide to a ratio of sulphur dioxide and the sum of sulphur dioxide and sodium oxide of 0.61-0.66, whereafter the resultant mixture is pressurized and liquid sulphur dioxide introduced therein to a ratio between sulphur dioxide and the sum of sulphur dioxide and sodium oxide of 0.75-0.81, and the water content is adjusted to a concentration of sulphur dioxide+sodium oxide of 10-13 percent by weight. The invention also relates to the use of the prepared composition for the manufacture of dithionite.

Abstract: The invention relates to the recovery of chemicals from waste liquor from wood pulp process, primarily black liquor, while utilizing energy liberated. Controlled total vaporization of the pulp waste liquor at high temperature and low oxygen potential is achieved by the external supply of energy. During the subsequent condensation and separation a melt or water solution is obtained which, without causticizing, can be used for the preparation of white liquor, and also an energy rich gas and mainly free from sulphur, consisting primarily of carbon monoxide and hydrogen.