Liquor is fed into the top liquor chamber of the heat exchanger where it is distributed to each tube. The liquor accelerates in velocity as it descends inside the tubes because of the gravity and drag of the vapor generated by boiling. Liquid is separated from the vapor in the bottom liquor chamber of the heat exchanger and with a skirt-type baffle in the vapor body. A supplemental entrainment separator can be installed in the upper portion of the vapor body to reduce liquid entrained with the vapor to a minimum.
Concentrated liquor is discharged from the bottom liquor chamber and cone bottom of the vapor body.
Caustic Soda Evaporator Evaporation also occurs inside the tubes of the falling-film evaporator. Tube sizes and lengths are comparable to those for rising-film evaporators . The retention time for liquor in this evaporator is less than that for a rising-film evaporator. For some applications, however, it is necessary to supplement an insufficient quantity of feed liquor with product liquor pumped to the top liquor chamber to avoid vapor blanketing of the inside tube surface.