Large-Scale Consumption and Zero-Waste Recycling Method of Red Mud in Steel Making Process

Abstract

To release the environmental pressure from the massive discharge of bauxite residue (red mud), a novel recycling method of red mud in steel making process was investigated through high-temperature experiments and thermodynamic analysis. The results showed that after the reduction roasting of the carbon-bearing red mud pellets at 1100-1200 • C for 12-20 min, the metallic pellets were obtained with the metallization ratio of ≥88%. Then, the separation of slag and iron achieved from the metallic pellets at 1550 • C, after composition adjustment targeting the primary crystal region of the 12CaO•7Al 2 O 3 phase. After iron removal and composition adjustment, the smelting-separation slag had good smelting performance and desulfurization capability, which meets the demand of sulfurization flux in steel making process. The pig iron quality meets the requirements of the high-quality raw material for steel making. In virtue of the huge scale and output of steel industry, the large-scale consumption and zero-waste recycling method of red mud was proposed, which comprised of the carbon-bearing red mud pellets roasting in the rotary hearth furnace and smelting separation in the electric arc furnace after composition adjustment.

Reductive Smelting of Neutralized Red Mud for Iron Recovery and Produced Pig Iron for Heat-Resistant Castings

“…So, reduced silicon, titanium, and phosphorus can pass into metal according reactions, as shown in Equations (12)- (14) and (17).…”

“…A high content of alkali in RM (up to 12% Na2O [9]) leads to furnace lining destruction caused by high RM reactivity during the melting process. Despite this fact, most studies are devoted to the pyrometallurgical processing of the initial RM [10][11][12], because the alkali present in RM significantly reduces its melting point and improves the separation of slag and metal [13,14]. However, from our point of view, it would be more practical to regenerate the alkali for recirculation by autoclave leaching of bauxite [15,16], since during the smelting of red mud with high sodium content, the alkali goes into the gas phase, and its further regeneration is very difficult [17].…”

Global recycling experience of red mud - a review. Part i: pyrometallurgical methods

“…Показано, что в результате обжига шламоугольных окатышей из красного шлама на агломерационной ленте в течение 10 - 12 мин восстанавливается 55 - 65 % железа [60]. В работе [61] красный шлам CHALCO Shandong Co., LTD (Zibo, China) смешивали с углеродом и восстанавливали в интервале температур 1100 - 1200 °С в течении 12 - 20 мин, в результате чего были получены металлизованные окатыши с коэффициентом металлизации 88 %.…”

“…Основной целью восстановительной плавки красных шламов является перевод железа в отдельную фазу и получение шлака, пригодного для извлечения ценных компонентов, например глинозема, титана, РЗМ или использование его в строительстве, сельском хозяйстве, в качестве десульфуратора стали и т. д. В последнее время все больше работ направлено на разработку многостадийных схем переработки красных шламов с цель ю максимального использования всей массы шлама без образования дополнительных отходов. В зависимости от концентрации различных элементов в исходном шламе и цели дальнейшего использования шлака плавку ведут с получением чугуна или ферросилиция [62], железотитанкремнистой лигатуры [63,64], с добавками различных флюсов (в большинстве случаев извести), а также кварцевого песка [65,66], глинозема [61,67], CaSiO 3 [68].…”

Recovery of Alkali from Bayer Red Mud Using CaO and/or MgO

“…The pH of red mud ranges from 9.2 to 13.0 with an average value of 11.3 ± 1.0, and the high alkalinity of red mud is the primary reason for its classification as a hazardous material [2][3][4][5]. Although most alumina producers dispose of this residue in tailing dams [6], this is in no way a long-term solution considering the associated security, environmental and utilization problems [7][8][9][10].…”