Abstract: Eenrgy and process chemicals are recovered from spent liquor in pulp preparation by thermally decomposing the spent liquor to solid and gaseous products at an elevated pressure and with addition of oxygen. The supply of oxygen should be less than that stoichiometrically required for a complete combustion and the temperature at the decomposition should be below the temperature at which a melt is formed.After recovery of sulfur-containing compounds the gas formed can give off energy in a gas turbine, thereafter generate steam and finally be used for drying fuel which is subsequently gasified under pressure and provides a further contribution of energy in the form of a combustible gas.Process chemicals are recovered from the solid products in known manner.

Abstract: The invention relates to a process of increasing the solids content of black liquor at its recovery in a sulfate pulping process. According to the invention, the liquor is first heated at a pressure which is so high that no boiling occurs at the heating temperature, after which the liquor is led to a tank where its pressure is released to a value below the saturation pressure of steam at the relative temperature of the liquor such that water is evaporated. The liquor thus concentrated can be led to the liquor combustion in the recovery process.

Abstract: The invention relates to a process for the washing of pulp with a maximum recovery of energy, the pulp after digestion being washed in a plurality of successive washing steps at a pressure above atmospheric in at least one of the steps and washing filtrate from a following step or fresh water being used as diluting and washing liquid in a given step. The outgoing washing filtrate from a washing step should be heat exchanged against incoming diluting and washing liquid to the subsequent step and a part of the filtrate (21) from the second step should be heat exchanged against washing filtrate (10) from the first step and then be combined with cooking liquor (23) for the digestion of the pulp. As diluting and washing liquids in the last two steps (4, 5), fresh water is used, which has also been heat exchanged against outgoing washing filtrate (54, 10) from the last and the first washing step.