A review of the alumina production from coal fly ash, with a focus in Russia

Increasing the percentage of recycling of various industrial waste is an important step towards caring for the environment. Coal ash is one of the most large-tonnage wastes, which is formed as a result of the operation of thermal power plants. The aim of this work is to develop a technology for the complex processing of coal ash. The tasks to achieve this aim are to develop a technology for the complex enrichment and separation of coal ash into components, with the possibility of their use in various applications, in particular: processing the aluminosilicate part as a pozzolanic additive to cement; carbon underburning for fuel briquettes; the iron-containing part for metallurgy and fertilizers. Complex enrichment and separation into components of coal ash were carried out according to the author’s technology, which includes six stages: disintegration, flotation, two-stage magnetic separation, grinding, and drying. The aluminosilicate component has a fairly constant granulometric composition with a mode of 13.56 μm, a specific surface area of 1597.2 m2/kg, and a bulk density of 900 kg/m3. The compressive strength for seven and twenty-eight daily samples when Portland cement is replaced by 15% with an aluminosilicate additive, increases to 30–35%. According to the developed technology, high-calorie fuel briquettes are obtained from underburnt with a density of 1000–1200 kg/m3, a calorific value of 19.5–20 MJ/kg, and an ash content of 0.5–1.5%. The iron-containing component, recovered by two-stage magnetic separation, has the potential to be used in metallurgy as a coking additive, in particular for the production of iron and steel. In addition, an effective micro-fertilizer was obtained from the iron-containing component, which: is an excellent source of minerals; improves the quality of acidic soil; helps soil microorganisms decompose organic matter faster, turning it into elements available to plants; promotes rooting of seedlings; helps to more effectively deal with many pests and diseases. As a result, the complete utilization of coal ash in various applications has been achieved.

show abstract

“…Not only iron-containing components are used in metallurgy, but production waste is also used in the aluminum industry [ 68 ].…”

Section: Resultsmentioning

confidence: 99%

Coal Ash Enrichment with Its Full Use in Various Areas

Petropavlovskaya

Novichenkova²,

Sulman³

et al. 2022

Materials

View full text Add to dashboard Cite

show abstract

“…In addition, this approach treats raw materials depleted in valuable elements that, as a result, can lead to lower productivity of the process, a significant increase in the amount of metallic iron added at the extraction stage, a possible quality deterioration of scandium and titanium concentrates, alumina, and white carbon due to impurity contamination. Hence, the approach based on direct hydrochloric acid leaching is preferable for aluminum raw materials with lower iron content, such as coal fly ash [66], nepheline ore [67], high silicon bauxite [68], etc.…”

Section: Discussionmentioning

confidence: 99%

Recovery of Scandium, Aluminum, Titanium, and Silicon from Iron-Depleted Bauxite Residue into Valuable Products: A Case Study

et al. 2022

View full text Add to dashboard Cite

Bauxite residue is a high-iron waste of the alumina industry with significant contents of scandium, aluminum, and titanium. This study focuses on the recovery of Sc, Al, Ti, and Si from iron-depleted bauxite residue (IDBR) into valuable products. Iron depletion was carried out using reduction roasting followed by low-intensity magnetic separation to enrich bauxite residue in Al, Ti, and Sc and reduce an adverse effect of iron on scandium extraction. Hydrochloric high-pressure acid leaching, aluminum precipitation by saturation of the acid leachate, solvent extraction of scandium using di(2-ethylhexyl) phosphoric acid (HDEHP) and tributyl phosphate (TBP), alkaline leaching of the acid residue with subsequent silica precipitation were used to obtain appropriate selective concentrates. As a result, scandium concentrate of 94% Sc2O3, crude alumina of 93% Al2O3, titanium concentrate of 41.5% TiO2, and white carbon of 77% SiO2 were prepared and characterized. Based on the characterization of the treatment stages and the obtained valuable products, the prospect for the application of the suggested flowsheet was discussed.

show abstract

“…Currently, the comprehensive utilization of coal fly ash mainly focuses on concrete, bricks, adsorbents, insulation panels, and agricultural fertilizers, which lack high-value applications [6,7]. Although the extraction of Al 2 O 3 is an effective means to realize the high-value utilization of coal fly ash [8], such methods often fail to realize the effective utilization of SiO 2 , which is one of its main components; this not only fails to completely realize the true harmless utilization of coal fly ash but also greatly reduces its economic value. Therefore, it is necessary to develop a simple but efficient approach to extract Al 2 O 3 from coal fly ash and simultaneously achieve the high-value utilization of SiO 2 .…”

Section: Introductionmentioning

confidence: 99%

Recycling Coal Fly Ash for Super-Thermal-Insulating Aerogel Fiber Preparation with Simultaneous Al2O3 Extraction

Gu,

Liu,

Zhu

et al. 2023

Molecules

View full text Add to dashboard Cite

A large quantity of coal fly ash is generated worldwide from thermal power plants, causing a serious environmental threat owing to disposal and storage problems. In this work, for the first time, coal fly ash is converted into advanced and novel aerogel fibers and high-purity α-Al2O3. Silica–bacterial cellulose composite aerogel fibers (CAFs) were synthesized using an in situ sol-gel process under ambient pressure drying. Due to the unique “nanoscale interpenetrating network” (IPN) structure, the CAFs showed wonderful mechanical properties with an optimum tensile strength of 5.0 MPa at an ultimate elongation of 5.8%. Furthermore, CAFs with a high porosity (91.8%) and high specific surface area (588.75 m2/g) can inherit advanced features, including excellent thermal insulation, stability over a wide temperature range, and hydrophobicity (contact angle of approximately 144°). Additionally, Al2O3 was simultaneously extracted from the coal fly ash to ensure that the coal fly ash was fully exploited. Overall, low-cost woven CAFs fabrics are suitable for wearable applications and offer a great approach to comprehensively use coal fly ash to address environmental threats.

show abstract

A review of the alumina production from coal fly ash, with a focus in Russia

Cited by 34 publications

References 154 publications

Coal Ash Enrichment with Its Full Use in Various Areas

Coal Ash Enrichment with Its Full Use in Various Areas

Recovery of Scandium, Aluminum, Titanium, and Silicon from Iron-Depleted Bauxite Residue into Valuable Products: A Case Study

Recycling Coal Fly Ash for Super-Thermal-Insulating Aerogel Fiber Preparation with Simultaneous Al2O3 Extraction

Contact Info

Product

Resources

About