Abstract: The present invention refers to a method to recover chemicals in mechanical pulping by evaporating mechanical pulping or recycled fibre plant effluent and burning the received concentrate under oxidative atmosphere to yield sodium carbonate. According to the invention said sodium carbonate is dissolved into water together with CaO in order to convert said sodium carbonate into sodium hydroxide at least partly.

Abstract: The invention relates to a method for bleaching mechanically defibered pulp with peroxide in alkaline conditions and for washing the bleached pulp and recovering chemicals from the spent liquor the bleaching step by concentrating and combusting the spent liquor and subsequently dissolving the ash thus formed into water. According to the invention, the alkaline conditions of the bleaching step are obtained by adding sodium aluminate to the pulp to be bleached, at least a part of the added sodium aluminate being the ash dissolved in water.

Abstract: The invention relates to a method for combusting an organic waste concentrate, which contains alkali metal compounds, under oxidative conditions for recovering the alkali metal compounds as alkali metal carbonates. According to the invention, the combustion is carried out at a temperature of at least about 850° C. The formed flue gases are cooled below a sticking temperature range of the alkali carbonates by mixing, and simultaneously water (8) is poured on the walls (9) of a cooling zone (2) at least at the sticking temperature range.

Abstract: The invention relates to a method for combusting an organic waste concentrate, which contains alkali metal compounds, under oxidative conditions for recovering the alkali metal compounds as alkali metal carbonates. According to the invention, the combustion is carried out at a temperature of at least about 850° C. The formed flue gases are cooled below a sticking temperature range of the alkali carbonates by mixing, and simultaneously water (8) is poured on the walls (9) of a cooling zone (2) at least at the sticking temperature range.

Abstract: The invention relates to a method for bleaching mechanically defibered pulp with peroxide in alkaline conditions and for washing the bleached pulp and recovering chemicals from the spent liquor the bleaching step by concentrating and combusting the spent liquor and subsequently dissolving the ash thus formed into water. According to the invention, the alkaline conditions of the bleaching step are obtained by adding sodium aluminate to the pulp to be bleached, at least a part of the added sodium aluminate being the ash dissolved in water.

Abstract: The invention relates to a method for enriching rosin acids from a hardwood-containing sulfate soap, in which the soap is partially acidified at a temperature higher than room temperature with an inorganic or organic acid so as to give the resulting mother liquid a pH of 4.5-7, thus enabling the rosin acids to be enriched from the soap into the fraction converted to the acid form, and the fatty acids to be enriched in the soap.

Abstract: The invention relates to acidification of soap, wherein the acidification is performed with a sodium bisulphite solution produced by absorbing the SO.sub.2 entrained in the flue gases obtained from the combustion of odor gases derived from a chemical pulp mill into an alkaline sodium solution which is NaOH or oxidized white liquor, or with a sodium bisulphite solution which is NaHSO.sub.3 -containing mother liquid obtained from SO.sub.2 or NaHSO.sub.3 acidification of soap. The acidification can be conducted in one or more steps and by the cross-current and/or counter-current method by recycling the Na.sub.2 SO.sub.3 mother liquid obtained from the acidification.