Energy requirements for split sulfidity pulp mills

Mass and energy balances have been prepared for comparison of methods of pr eparing split sulfidity liquors by various means of green liquor fractionat ion together with causticising with lime or ferric oxide. Causticising with ferric oxide offers substantial energy savings if used with a compatible f ractionation process. Partial dissolution is the least energy demanding met hod, but is only suitable with lime causticising. Cooling crystallisation i s a moderate energy user, but the high degree of hydration of the crystals it forms results in a large energy demand in the ferrite kiln and none of t he potential means of reducing the degree of hydration is very attractive. Evaporative crystallisation is the most energy intensive method of fraction ation, but it permits energy savings elsewhere in the mill far in excess of its energy use.