Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报(英文版)

Transactions of Nonferrous Metals Society of China

Vol. 29    No. 6    June 2019

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Reaction kinetics and mechanism of calcium oxide in dilute sodium aluminate solution with oxalate based on lime causticization
Bai-yong ZHANG1,2, Xiao-lin PAN1, Jiang-zhou WANG1, Hai-yan YU1, Gan-feng TU1

1. School of Metallurgy, Northeastern University, Shenyang 110819, China;
2. Shenyang Aluminum & Magnesium Engineering & Research Institute Co. Ltd., Shenyang 110001, China

Abstract:The formation kinetics and mechanism of tricalcium aluminate hydrate and calcium oxalate in dilute sodium aluminate solution and sodium oxalate solution were studied respectively based on the lime causticization, and the optimal conditions for removing the oxalate in dilute sodium aluminate solution as well as the mechanism were finally obtained. The formation processes of tricalcium aluminate hydrate and calcium oxalate are mainly controlled by the chemical reaction and the inner diffusion respectively, and the corresponding reaction rate equations as well as the apparent activation energy were calculated. The hydrocalumite with a spatially interleaved structure will form in dilute sodium aluminate solution with sodium oxalate, greatly removing the oxalate impurity by absorption. Calcium oxalate can be converted to tricalcium aluminate hydrate with the increasing reaction time. The oxalate causticization efficiency and the alumina loss rate can be over 90% and below 31% respectively when reacted at 50 °C with a stirring rate of 200 r/min.

 

Key words: Bayer process; lime causticization; oxalate; kinetics; sodium aluminate solution

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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