Abstract: The invention relates to a process for drying timber in which the timber is fed gradually through a drying tunnel while at the same time being permeated by a drying air with a temperature below 80.degree. C. transported primarily in the longitudinal direction of the tunnel. Said drying tunnel is divided into two separate sections with said drying air divided into two circulating substreams, of which one flows through the first section of the tunnel in the direction of motion of the timber and the other through the second section of the tunnel contrary to the direction of motion of the timber, after which said substreams are conditioned and returned to their section.

Abstract: Process for causticizing a water solution containing alkali carbonate with calcium oxide and hydroxide by bringing the water solution containing alkali carbonate into contact with the calcium oxide or hydroxide and by separating the alkali hydroxide solution arisen in the causticizing from the calcium carbonate precipitate. The water solution containing alkali carbonate is conducted through a bed which has been formed by mixing calcium oxide and calcium carbonate in the causticized alkali solution and by removing the excess alkali solution.

Abstract: A method for the production of cellulose by the batch cooking process, wherein the digester is filled with chips and cooking liquor, and the batch is cooked at elevated temperature and pressure in order to obtain a delignified cellulose pulp in the digester. For the impregnation stage a cooking liquor is used which contains a substantially higher amount of active chemicals than is required for the cooking of the batch, and before the actual delignification stage the active-chemical batch for the cooking is adjusted and the excess amount of active chemicals is removed by replacing it by part of the hot spent cooking liquor recovered from a previous cooking.

Abstract: A process for continuous digestion of wood chips which are passed through a heating zone, a digesting zone and a cooling zone in contact with cooking liquor is disclosed. In this process the wood chips are fed into and the liquid phase removed from the input end of the heating zone in such relative quantities that their heat-capacity flows are of approximately the same order of magnitude.

Abstract: The invention relates to a method for evaporation of a solution in a recompression evaporation plant. The solution is evaporated first in known manner by indirect transfer of heat from the recompressed vapor through condensation of said vapor in one or more evaporation units. After pre-evaporation in this fashion the solution is finally evaporated by direct transfer of heat from the overheated vapor which is obtained by recompression of the vapor formed in evaporation. According to the invention this final evaporation is achieved by mixing the solution in finely-divided form with the overheated vapor and then after thermodynamic equilibrium between the vapor and liquid phases has been substantially attained separating the solution from the vapor. The solution thereby obtained can be further evaporated without the addition of heat but with a reduction of pressure by means of conducting it to an expansion vessel which is connected by a vapor line to the suction line of the compressor.

Abstract: In a device for adjusting the flow quantity and drop size of black liquor to be injected into a soda digester, an outflow opening with an adjustable cross-sectional area, relatively rotatable coaxial outer and inner pipes, the outer pipe being provided with an end piece covering a part of the outer end of the outer pipe and the inner pipe being provided with a nozzle piece covering a part of the outer end of the inner pipe, the outflow opening being formed by an opening remaining outside the areas covered by the end piece and the nozzle piece.

Abstract: A method of concentrating or evaporating water from water-containing liquids in a falling-stream or falling-film evaporator through which the liquid is caused to pass downwardly through ribbed tubes which are heated externally. The material to be evaporated is distributed uniformly to the evaporator tubes and driving steam is simultaneously introduced into the latter at a velocity so controlled with respect to the pressure that turbulence develops at the inlet to the tubes. The mixture of the material to be evaporated and drive steam is caused to rotate about the longitudinal axis of the evaporator tubes as the mixture traverses same and the concentrated product is separated from the steam and product vapors at the outlet end of the tubes.

Abstract: Heat exchange is improved in natural-circulation and flowthrough evaporators in which the liquid to be evaporated is admitted to heating tubes and evaporators therein as the fluid rises in the tubes. According to the invention the liquid is preheated under a higher hydrostatic pressure than at the inlet to the heating tubes by treatment with direct steam, preferably in a steam-jacketed siphon tube forming a downcomer from a separator removing concentrate from the vapors emerging from the evaporator.