METHOD FOR PREVENTING SCALE DEPOSITION IN MULTIPLE-EFFECT EVAPORATOR AND ITS WASHING METHOD

摘要

PURPOSE:To prevent the deposition of scale in an evaporator, and to increase the evaporation efficiency by operating normally (n-1)-number of circulating lines, and supplying a washing liquid to the remaining one circulating line in black liquor concentration. CONSTITUTION:Two branching parts 53a and 53b are opened, one branching part 53c is closed, and a black liquor of 47% concn. from the adjacent evaporator on the low-concn. side is supplied into circulating lines 45 and 46. The liquor is concd. to 63% concn. in an evaporation chamber 43, supplied into an evaporation chamber 42 through a communicating line 54 to concentrate the liquor to 70% concn., and taken out through a discharge line 55. A dilute black liquor or hot water is supplied into a circulating line 47 to wash the circulating line 47, a pump 52, and the inside of the evaporation chamber 44. The deposited scale is thus removed.