Evaporation 515 not usually adaptable to compression evaporation. Mechanical compression evaporation sometimes requires more heat than is available from the com pressed vapor, so the evaporation rate can be controlled by regulating the makeup steam flow to maintain a constant liquor temperature. Usually mechanical compression results in slightly higher maintenance costs because of the compressor and its drive. Mechanical compression is best suited for atmospheric or pressure operation, for mildly corrosive vapors, for low boiling-point elevation liquids, low temperature differences across the calandria, and where energy economy is important Compressor Motor ar Thick Makeup steam→ Heate. Circulating pump Figure 19. Mechanical recompression applied to forced-circulation evaporator. (From Unit Operations of Chemical Engineering by W.L. McCabe and J.D. Smith(2nd ed 1967), P. 473. @McGraw-Hill. Used with permission of McGraw-Hill Book Company)Evaporation 51 5 not usually adaptable to compression evaporation. Mechanical compression evaporation sometimes requires more heat than is available from the com￾pressed vapor, so the evaporation rate can be controlled by regulating the makeup steam flow to maintain a constant liquor temperature. Usually, mechanical compression results in slightly higher maintenance costs because of the compressor and its drive. Mechanical compression is best suited for atmospheric or pressure operation, for mildly corrosive vapors, for low boiling-point elevation liquids, low temperature differences across the calandria, and where energy economy is important. Body I1 Mokeup steam -4 Heater 2 41 Condensate i II Circulating pump -, kf E Thick liquor discharge - +Feed Figure 19. Mechanical recompression applied to forced-circulation evaporator. (From Unit Operations of Chemical Engineering by W. L. McCabe and J. D. Smith (2nd. ed., 1967), p. 473. OMcGraw-Hill. Used with permission of McGraw-Hill Book Company)