PURPOSE: To recover and reuse the latent heat of generated steam efficiently by washing the evaporating steam contg. acidic gases with an aq. alkali soln. having the b. p. elevating value lower than the b. p. elevating value of the liquid in an evaporator then compressing and heating said steam thereby using as said steam as a heating source for liquid to be concentrated.

CONSTITUTION: The vapor contg. acidic gases of the temp. higher by elevation of b. p. than the saturation temp. generated in an evaporator 1 is introduced through a piping 8 into a steam scrubber 9 and while the steam descends in a packed tower 13, the steam comes into cocurrent contact with the alkaline washing liquid circulated and distributed on the packings from a liquid distributor 17, whereby the acidic gases in the steam are adsorbed away by reaction. The steam removed of the acidic gases without losing latent heat is sucked through a piping 26 into a turbo type compressor 6, by which the steam is compressed and heated to supersaturated steam which is conducted through a piping 27 into a temp. reducer 28 where the steam is brought into contact with the warm water sprayed through a piping 29, by which the steam is humidified and cooled to satd. steam. This satd. steam is introduced through a piping 7 into a heating vessel 2.