Abstract: A method for the preparation of pulp by means of alkaline cooking, in which method spent liquor is transferred to pressurized tanks, and at least one liquor is expanded corresponding to a temperature difference of 1 to 5° C. The generated steam is led to turpentine recovery. Thus, the removal of turpentine and gases dissolved in said liquor is effective, the amount of recovered turpentine increases, and pulp of better washability and higher quality is obtained.

Abstract: A method for the preparation of pulp by means of alkaline cooking, in which method spent liquor is transferred to pressurized tanks, and at least one liquor is expanded corresponding to a temperature difference of 1 to 5° C. The generated steam is led to turpentine recovery. Thus, the removal of turpentine and gases dissolved in said liquor is effective, the amount of recovered turpentine increases, and pulp of better washability and higher quality is obtained.

Abstract: A method for burning secondary sludge in a recovery boiler, in which method secondary sludge is mixed with black liquor. According to the method, an alkali is added to the secondary sludge so as to obtain a mixture having a pH of over 7, whereafter the mixture of alkali and secondary sludge is heated to a temperature of over 80.degree. C. and kept at this temperature for over 30 minutes. Thereafter the heat treated mixture of alkali and secondary sludge is supplied to the thick end of a black liquor evaporation plant.

Abstract: Method of reducing scaling of heat transfer surfaces in an evaporation plant of a sulphate cellulose mill when sulphate cellulose is manufactured. In the method, ash to be fed into black liquor is mixed thereto after soap separation when the dry solids content of the black liquor is so low that sodium sulphate and other soluble salts contained in the ash dissolve in the black liquor completely.

Abstract: An evaporator operating on falling film principle, has a shell (1) with a system (2) of evaporating tubes therein, whereby a liquid to be concentrated is fed on the outer surface of the evaporating tube system (2) and vapor is led to flow inside the tubes of the evaporating tube system (2). The evaporating tube system (2) is formed of evaporating elements, each evaporating element being formed of evaporating tubes (9) substantially on the same level. The upper ends of the tubes are connected to a common collecting chamber (8) and the lower end, respectively, to a common collecting chamber (10) in such a manner that there is a connection between both collecting chambers (8, 10) through each tube (9) between them, due to which the collecting chambers (8) of the upper end of the evaporating elements are interconnected through the upper connecting chamber (12), and respectively, the collecting chambers (10) of the lower end are interconnected through the connecting chamber (13) of the lower end.