Seed In The Mother Liquor Evaporation Process Scaling And Scale Prevention Study

Impurities such as Na₂CO₃ etc easily precipitate to result in the formation of scale on the wall of heater during the evaporation process of spent liquor from seeded precipitation process, which badly influences the heat diffusion and material flow of this process, even block pipe. This is harmful to the production process. Therefore, investigation on the formation law of scale in the evaporation process of spent liquor from seeded precipitation process, study on the influence of anti-scale addictives on the retarding scaling and adoption of proper anti-scale measure are to regard as have a great applying prospect for alumina industry.The formation law of scale on the heating surface and the effect of various anti-scale addictives on the retarding scaling of heating surface during the evaporation process of spent liquor were studied in this paper. Results indicate that addictive type GR-4 and GR-5 etc can effectively retard the formation rate of scaling on the heating surface, restrain SiO₂ from precipitation and decrease the scale yield by 60～70％. Meanwhile, scale occurred on the heating surface can be easily cleaned because it becomes unconsolidated after adding addictive type GR-4, GR-5 etc in the evaporation process. The addition content and addition technology of anti-scale addictive type GR-4 are also determined through experimentation. Results of research on anti-scale addictive type GR-4 can provide a favorable reference for industrial application of scale inhibitor.Subsequently, the anti-scale mechanism of addictive during the evaporation process of spent liquor was investigated and discussed. Results show that scale inhibitor type GR-4 can greatly reduce the interfacial force of evaporating liquor and has flocculation and dispersion effect on the system, which contributes to anti-scale action.Industrial experimentation was performed in some alumina refinery of CHALCO according to the laboratory results. The result demonstrates that scale inhibitor type GR-4 can effectively retard the formation rate of scaling on the evaporator, prolong the run time of equipment and cleaning period. It is propitious to improve the efficiency of evaporation and decrease the production cost.