Abstract: A method including evaporating aqueous solutions containing ammonia, adding an acid to the evaporated vapor flow to form an ammonium salt, and condensing the vapor flow to form a liquid containing the salt. By this method the ammonia formed into a salt is not present as an inert gas layer which would impede condensation on the condenser surfaces.

Abstract: The invention relates to a heat exchange element (1) which is made up of a bag of a film material, such as plastic film, and to a heat exchanger made up of such heat exchange elements, the heat exchanger being suitable, for example, for the evaporation of effluents which contain solid matter, such as effluents from bleaching. The transfer of heat takes place in the bags (1) from a vapor condensing in the interior (3) of the bags to a liquid evaporating on their exterior surfaces (2). The forming evaporated vapor may be recycled via a compressor to the interior of the bags as heating vapor so that the heat exchanger will function as a distillation apparatus.

Abstract: A liquid distributor for distributing liquid over the heat transfer surface of an evaporator includes a channel array including one or more supply channels and downwardly deviating distribution channels. Each distribution channel has a step-shaped expansion located downstream with respect to the supply channel and connecting therewith via a sharp point, restricting the liquid suction created in the distribution channel. Sharp points provided in the supply channel or channels further restrict the liquid suction.

Abstract: The method relates to a film heat exchanger and a method for constructing the same. The heat exchanger comprises bags (1) made of film material in order to transfer heat from the steam to be condensated inside the bags to the liquid to be evaporated on the outer surfaces (18) thereof, as well as feed channel arrays for distributing steam (10) and liquid onto the internal and external heat transfer surfaces of the bags. According to the invention, inside the top end (2) of each bag (1), there is provided an essentially straight strip (11) bordering the steam channels (10), to which strip the bag is fastened; in connection with the fastening, the top edge of the bag is pulled straight by bending the bag, so that the middle part of the bag is raised in relation to the sides (12) thereof, and the thus straightened edge is then attached to the strip provided inside the bag.