Abstract: An apparatus for distillation of a liquid near or above its critical point wherein the liquid contains a dissolved solid. The apparatus includes a separation section wherein the liquid may be separated into a vapor and a liquid residue separated by a liquid surface. The apparatus includes a pump for pumping liquid into the apparatus so as to establish and maintain the liquid and vapor in the separation section at a desired pressure and a heat source for heating the liquid and vapor so as to establish a rising temperature profile in the separation section. The pump and heat source are cooperatively controllable for regulating the position of the liquid surface so that liquid residue can be discharged from immediately below the liquid surface.

Abstract: In a method in the operation of a firing plant of the type comprising a combustion furnace and heat exchanger means to transfer thermal energy from the flue gas of the furnace to its combustion air, wherein a vaporizable liquid, such as water, is added to the combustion air of the furnace, the combustion air pressure is reduced in the portion of the heat exchanger means where the said liquid is caused to evaporate, the necessary evaporation heat being taken from the flue gas of the furnace before the flue gas is discharged to the atmosphere. A plant for performing the method is characterized by containing a pump (11) which has a relatively small inlet opening (10) so that the pump (11) creates a negative pressure in the portion (12) of the heat exchanger (9) where the liquid, fed by means of a nozzle (13), evaporates. This allows large amounts of water to evaporate, and flue gas, which flows through the heat exchanger portion (14), is cooled to a low temperature.