Evaluation of Calcium Aluminate Slags and Pig Irons Produced from the Smelting-Reduction of Diasporic Bauxite

This work evaluates the characteristics of calcium aluminate slag and pig iron samples obtained from the smelting of calcined and reduced diasporic bauxite ore. The study is conducted in the Pedersen process framework, which is a method to produce alumina from low-grade resources. Parameters such as the effect of crucible type, lime addition, and atmospheric conditions are studied considering the characteristics of the product pig irons and calcium aluminate slags for further uses. The behavior of the bauxite and distribution of the species between slag and metal was assessed based on the applied analytical techniques and thermodynamic calculations. Iron was reduced and separated from the slags in the presence of carbon (graphite crucible) for both the reduced and calcined bauxite. Si and Ti were mainly concentrated in the slags. Iron was separated from the slag in the absence of carbon (alumina crucible) for the H2-reduced bauxite. The results show that slags with increased lime additions are composed mainly of 5CaO.Al2O3 and CaO.Al2O3, that are considered highly leachable compounds. An optimum CaO/Al2O3 mass ratio of 1.12 was suggested. The presence of O2 and/or OH- in the furnace atmosphere will result in the formation of 12CaO.7Al2O3.

“LIQUEFACTION” AND “DYNAMIC SEPARATION” DIFFERENT ASPECTS OF THE SAME PROBLEM

In 2015 the Bulk Jupiter sank during bad weather loaded with bauxite. Nearly automatically everybody considered “liquefaction” to be the prime cause of this accident. Liquefaction is a phenomenon where solid bulk cargo, triggered by the ship movements, starts to behave has a high density viscous liquid in the holds. The stability is negatively influenced by the free surface effect and further research, especially by the Global Bauxite Working Group or GBWG showed that bauxite ore simply will not liquefy even under the worst case shipping conditions. Evidence from real world shipments of bauxites shows that instabilities due to moisture cannot be explained by liquefaction phenomena, but can be under a “dynamic separation” mechanism of instability. Both liquefaction and dynamic separation are caused by an excessive moisture of the bauxite cargo. However, the influence on the stability of the ship is fundamentally different.

Geotechnical Properties of Bauxite: A Case Study in Bukit Goh, Kuantan, Malaysia

The research focuses on the basic and morphological characteristics to ensure bauxite ore reached the International Maritime Solid Bulk Cargoes Code (IMSBC Code) standard before being exported to other countries. The testing procedure, referred to as Geo-spec 3: Model Specification for Soil Testing, was performed to discover the basic parameters of the soil, including pore size distribution, water content, particle density, and morphology qualities. At Bukit Goh, Kuantan, about four (4) samples were chosen, whereas two (2) samples were from the stockpile and two (2) samples were from the Bukit Goh mine. The results illustrated that the mean water content of the soil is 20.64% which is above 10% of the recommended value. The value of Bulk Density is not in the range of 1190 kg/m3 to 1389 kg/m3, which is 2836.25 kg/m3 and the particle size distribution for fine material is greater than 30%, and coarse material is less than 70%. The SEM examination revealed a high concentration of tiny particles in bauxite samples. Bukit Goh bauxite cannot be classified as group C under the IMSBC Code. As a result, the bauxite does not meet the criteria and cannot be shipped.

Review of the Valorization of Normalized Red Mud as Environmentally Sustainable Waste Management

The Red Mud has focused through major industrial and scientific research in industrial waste valorization. Red mud is the discarded produce of alumina extraction processes from its parent the bauxite ore. Its high alkalinity causes it to be kept in large quantities, resulting in increased deforestation. Annually, it is estimated that 64.2 MMT of red mud wastes are formed around the world, and India produces about 9MMT with less hope of being reused, posing a serious threat of pollution and contamination of both soil, ground water and the environment. Large numbers of research have shown that this bauxite solid waste can be refurbished to make construction bricks, pavement tiles, ceramic materials, but no full large-scale benign re-utilization have been made. The intent of the research is to probe in to the applications of red mud in the construction and various sectors, giving emphasis on Indian context. Other researchers' observations were considered and analyzed in terms of environmental, economic, and technical feasibility to fulfill zero waste demand due to red mud.

Recovery of bauxite ore particles -1mm from tailings of the Tan Rai bauxite processing plant by mechianical classifiers

Tailings of the Tan Rai bauxite mineral processing plant contain a relatively high proportion of fine bauxite ore particles of less than 1mm. This amount of discarded fine bauxite particles necessarily leads to a high loss of valuable bauxite mineral and also require more tailings dam space. Recovery of such fine bauxite ore particles may produce certain economic and environmental effects to the current processing plant. The paper presents results of the study on recovery of fine bauxite ore particles -1 mm from tailings of the Tan Rai - Lam Dong bauxite mineral processing plant by the use of mechanical classifiers. The obtained +0.5 mm bauxite concentrate are suitable for blending with the +1 mm concentrate of the current plant. The study results showed that recovery of fine bauxite ore particles -1mm from the plant tailings may produce additional amount of valuable concentrate to ensure the supply requirements to the alumina plant and also add some values to the effective mineral resource utilization and bring some economic efficiency.

Assessment of Naturally Occurring Radioactive Materials (NORM) in Mining Residues and Environmental Material from Sefwi, Awaso Bauxite Mine

Gamma ray spectrometry was used to quantify level of NORM in mining residues sampled at Awaso bauxite mine and surrounding communities. The radionuclides of interest were 238U, 232Th and 40K and the radioactivity levels were determined in soil, bauxite ore, red mud and water samples from wells. The radioactivity concentrations in soil, bauxite ore and red mud 238U, 232Th and 40K were 18.01±1.96 Bqkg-1, 19.07±2.12 Bqkg-1 and 103.21±1.74 Bqkg-1; 39.42±4.18 Bqkg-1, 97.32±10.63 Bqkg-1 and 14.68±1.82 Bqkg-1; 44.85±4.79, 64.23±6.58 and 125.30±18.72 Bqkg-1. The activity levels for both 232U and 232Th were above world-wide average values while Potassium-40 levels were lower. The mean activity concentration values of 238U, 232Th and 40K in water samples were 1.49±0.45 Bql-1, 3.68±0.69 Bql-1 and 15.69±0.28 Bql-1 respectively and were within the world average activity concentrations except for bauxite ore and red mud. The committed effective dose was 0.74 mSv and annual effective dose estimated to be 0.136 mSv which is below recommended dose limit of 1 mSvyear-1 for public exposure.

Extraction of Aluminum and Iron from Bauxite: A Unique Closed-Loop Ore Refining Process Utilizing Oxalate Chemistry

The Bayer process holds an exclusive status for alumina extraction, but a massive amount of caustic “red mud” waste is generated. In this work, three oxalate reagents: potassium hydrogen oxalate (KHCO), potassium tetraoxalate (KHCO·HCO), and oxalic acid (HCO) were investigated for the Al and Fe extraction process from NIST SRM 600 – Australian Darling range bauxite ore. More than 90% of Al and Fe was extracted into the aqueous phase in less than 2 h with 0.50 M CO for all three reagents. The Fe and Al can be selectively precipitated by hydrolyzing the aqueous phase. By acidifying the Al and Fe free filtrate, 80% of the CO can be precipitated as KHCO·HCO. Greater than 90% of the aqueous acid can also be recycled using a cation exchange resin. The proposed closed-loop process is an energy-efficient, cost-effective, environmentally-friendly route for extracting Al and Fe from bauxite ore.

The Utilization of Bauxite Residue with a Calcite-Rich Bauxite Ore in the Pedersen Process for Iron and Alumina Extraction

Metallurgical grade alumina is produced worldwide through the well-known Bayer process, which unavoidably generates bauxite residue (BR, also known as red mud) in almost equal amounts to alumina. This study aims the valorization of BR through a smelting-reduction process to obtain calcium aluminate slags that can be a proper feed for alumina recovery via the Pedersen process. It investigates the thermodynamics and characteristics of the slags and pig iron produced from mixtures of BR, a bauxite beneficiation byproduct, and lime. In this context, the evolution of the different phases in the slags is studied with advanced analytical techniques and thermodynamic calculations. According to the results, a CaO/Al2O3 mass ratio within 1.3 to 1.4 in the slags can yield more Al2O3-containing leachable phases, such as CaO·Al2O3 and 12CaO·7Al2O3. The cooling dictates the amount and the characteristics of these phases, and the slower cooling rate yields improved slag characteristics. The distribution of the elements between the slag and metal phases shows that iron is separated, and the majority of the P, Cr, Ni, and V are distributed in the produced pig iron, while S, Ti, and Si are mostly concentrated in the slags.