MODIFICATION THE PEDERSEN PROCESS THROUGH THE STUDY OF THE EFFECT OF CAO FLUX SUBSTITUTION BY NA2CO3 FLUX IN BAUXITE SMELTING-REDUCTION STAGE

• Main Author: Satiafdi Hasibuan, Mhd.Managor
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/47276
• Institution: Institut Teknologi Bandung

Aluminium metal is obtained from alumina (Al2O3) which is processed through Hall Heroult process. Alumina is obtained from bauxite ore in nature which is processed through Bayer process. However, Bayer process produces by-product (red mud) that is considered to be hazardous to the environment and still containing aluminium with significant amount. There is an alternative process that converts bauxite to alumina, that is Pedersen process. Pedersen process was used around 40 years by a factory in Hoyanger, Norway. This process uses combination of pirometallurgy and hydrometallurgy processes. In pyrometallurgy stage CaO is used as flux and pig iron is produced which can be used as raw material for steel making process. While in hydrometallurgy stage Na2CO3 solution is used, alumina and by-product (grey mud) are produced. The latter can be used as raw material for cement production. However, the process ceased to be used commercially in 1969 due to economic reason. This is because the process involves smelting at high temperature of more than 1500°C. Moreover, in the past, high grade bauxite was available and more economic to be processed through Bayer process and the red mud was not considered as serious problem. Decreasing high grade bauxite reserve and increasing environmental awareness encourage study to find alternative for bauxite processing. In this study, the Pedersen process has been revisited through the study of the effects of CaO and Na2CO3 as flux respectively operating temperature on bauxite smelting-reduction (pyrometallurgy) stage to the resulting metal product. The study was done by performing smelting-reduction experiments using briquettes that were made by mixing of bauxite and flux with coal bed reductor in crucible inside muffle furnace. The CaO dosage was 0%, 25%, 50%, and 75% (ratio to weight of bauxite) and the Na2CO3 dosage was 40%, 85%, 140% (equivalent with Na2O 25%, 50%, and 75%). At each dosage the smelting-reduction experiments were carried out at temperatures of 1450°C, 1500°C, and 1550°C. The experiments at each condition were repeated three times. The result shows that increasing Na2CO3 addition leads to increasing metal formation. For the CaO flux, the experiments show optimum result at 50% CaO addition. Experiment with Na2CO3 addition produce more metal than with CaO addition. In general, decreasing operating temperature leads to decreasing metal formation.