ENERGY SAVING BY RECONSTRUCTION OF DIGESTION SYSTEMS
Solymár, K. and Steiner, J.
The low and high temperature, one- and two-stream bauxite digestion systems using occasionally direct steam injection for heating up the bauxite slurry are analysed from the aspect of technology and energy.
Based on the experience gained with the tube digestion equipment in Hungary the tube-in-tube type heat exchanger elements of the tube digester were successfully adapted to the conventional digestion systems for heating up the bauxite slurry before predesilication and for the replacing of the heated autoclaves.
By this solution, when preheating the slurry up to 140 to 145˚C only, approx. 10 to 15 % energy saving can be realised which can be increased by a further 10 % at full development of the new heating system (preheating up to 200 to 205˚C) at high pressure digestion of 240˚C.
Based on the above, the effect of this solution along with the effect of the conversion of direct heating of bauxite slurry to indirect one will be analysed in cases of various (one- and two-stream) digestion systems.
According to the calculations, the reconstruction of the conventional digestion systems might result in a 20 to 25 % energy saving depending on the technological solution applied.