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13 pages, 4638 KiB

Open AccessArticle

Migration and Conversion of Al Element in the Hydrometallurgical Preparation of Al₂O₃ from Secondary Aluminium Dross

by Kepeng Huang, Changjiang Zheng, Qingda Li, Xinyang Qiu and Xuemei Yi

Processes 2025, 13(5), 1281; https://doi.org/10.3390/pr13051281 - 23 Apr 2025

Viewed by 158

Abstract

The amount of secondary aluminium dross in China exceeds one million tons annually, posing environmental and disposal challenges. This study explores acid leaching as an alternative to conventional alkali methods for recovering Al from secondary aluminium dross to produce Al₂O₃ [...] Read more.

The amount of secondary aluminium dross in China exceeds one million tons annually, posing environmental and disposal challenges. This study explores acid leaching as an alternative to conventional alkali methods for recovering Al from secondary aluminium dross to produce Al₂O₃. Research has focused on optimizing leaching conditions. Under optimized H₂SO₄ leaching conditions, an Al³⁺ leaching ratio of 86.5% is achieved. By maintaining a pH below 9 during hydrolytic precipitation and multiple washes, the leaching efficiency of Al from Al(OH)₃ reached 95.97%. The original dross, which is primarily composed of Al, Al₂O₃, and AlN, undergoes a transformation where AlN becomes Al(OH)₃ during washing. Thermal decomposition then yields Al₂O₃. The overall recovery of Al reaches 83.11%. Full article

(This article belongs to the Special Issue Recent Trends in Extractive Metallurgy)

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16 pages, 5079 KiB

Open AccessArticle

Thermodynamic Modeling and Research for Processing Complex Concentrate Blends in Custom Copper Smelters for Maximum Revenue

by Denis Shishin, Nagendra Tripathi, Svetlana Sineva and Evgueni Jak

Processes 2024, 12(12), 2820; https://doi.org/10.3390/pr12122820 - 9 Dec 2024

Viewed by 1208

Abstract

Custom copper smelters, which are dependent on purchased concentrates, are facing increasing economic pressures amid falling treatment and refining fees. With the declining availability of high-grade, low-impurity concentrates, copper demand is expected to surge to support the transition to renewable energy. This study, [...] Read more.

Custom copper smelters, which are dependent on purchased concentrates, are facing increasing economic pressures amid falling treatment and refining fees. With the declining availability of high-grade, low-impurity concentrates, copper demand is expected to surge to support the transition to renewable energy. This study, which is based on recent observations of Chinese custom smelters, examines their strategies to address the challenge of purchasing concentrates at record-low treatment and refining charges. By investing in slag flotation technology, smelters can enhance copper, gold, and silver recovery. By blending high-grade and low-grade concentrates, they can capitalize on the gap between the recoverable and payable metals, which are often referred to as “free metals”, while also benefiting from byproducts, mainly sulfuric acid. While this approach offers economic opportunities, it introduces operational complexities. To mitigate these, laboratory testing, combined with advanced digital predictive tools based on thermodynamics, is crucial. This study demonstrates the use of thermodynamic models supported by experimental work for analyzing furnace operations. FactSage^® software and a custom database are employed to define the operating window of two common flowsheets: (1) flash smelting + flash converting and (2) bottom-blown smelting + bottom-blowing converting. Full article

(This article belongs to the Special Issue Recent Trends in Extractive Metallurgy)

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34 pages, 5942 KiB

Open AccessArticle

Gold Recovery from Smelting Copper Sulfide Concentrate

by Elmira Moosavi-Khoonsari and Nagendra Tripathi

Processes 2024, 12(12), 2795; https://doi.org/10.3390/pr12122795 - 7 Dec 2024

Cited by 2 | Viewed by 2059

Abstract

Gold is a significant revenue source for custom copper smelters facing profitability challenges due to low treatment and refining charges, stricter regulations, and rising costs. Gold is also often blended with copper concentrates, but precise recovery rates from smelting processes are poorly documented [...] Read more.

Gold is a significant revenue source for custom copper smelters facing profitability challenges due to low treatment and refining charges, stricter regulations, and rising costs. Gold is also often blended with copper concentrates, but precise recovery rates from smelting processes are poorly documented despite gold critical economic importance. This paper aims to provide the first comprehensive estimates of gold first-pass recovery across various operational units within the copper sulfide concentrate processing flowsheet. It evaluates the effectiveness of different copper smelting and converting technologies in recovering gold. Optimizing gold first-pass recovery is especially important to enhance immediate financial returns and responsiveness to market dynamics, allowing companies to capitalize on favorable gold prices without delays. Given the absence of direct measurements for gold recovery rates, this research develops an estimation method based on understanding gold loss mechanisms during smelting. This study identifies and analyzes key input and output parameters by examining data from various copper producers. By correlating these parameters with gold loss, the research estimates gold first-pass recovery rates within the copper smelting process. Among integrated smelting-converting routes, the flash smelting to Peirce–Smith converting route achieves the highest gold first-pass recovery (98.8–99.5%), followed by the Mitsubishi continuous smelting and converting process (94.3–99.8%), bottom-blowing smelting to bottom-blowing converting (95.8%), flash smelting to flash converting (95.5%), Teniente smelting to Peirce–Smith converting (95.2%), and the Noranda continuous smelting and converting process (94.8%). The final recovery rates are expected to be higher considering the by-products’ internal recirculation and post-processing within the copper flow sheet. Additionally, superior gold recoveries are attributed to advanced metallurgical practices and control systems, which vary even among companies with similar technologies. This research demonstrates that copper smelting can effectively recover over 99% of gold from sulfide concentrates. Gold accumulates up to 1000 times its original concentration in anode slime during electrolytic refining, generating 5–10 kg of slime per ton of copper, which is further processed to recover gold and other by-products. Major smelters operate precious metal plants where recovering gold from highly concentrated anode slime is both cost-effective and efficient. Full article

(This article belongs to the Special Issue Recent Trends in Extractive Metallurgy)

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11 pages, 4048 KiB

Open AccessArticle

Effects of Room-Temperature Center Gas Distributor Injection on the H₂ Shaft Furnace Process: A Numerical Study

by Lei Shao, Hongfu Yu and Chenxi Zhao

Processes 2024, 12(8), 1666; https://doi.org/10.3390/pr12081666 - 8 Aug 2024

Viewed by 1218

Abstract

In the current work, a computational fluid dynamics-based model was utilized to investigate the performance of the H₂ shaft furnace under a scenario where room-temperature H₂ is injected through a center gas distributor (CGD) installed at the unit bottom. Modelling was [...] Read more.

In the current work, a computational fluid dynamics-based model was utilized to investigate the performance of the H₂ shaft furnace under a scenario where room-temperature H₂ is injected through a center gas distributor (CGD) installed at the unit bottom. Modelling was conducted to simulate scenarios where the CGD operation is applied with different feed gas rates (ranging from 0 to 250 Nm³/t-pellet). The results showed that a high temperature level and thus a better internal thermochemical state can be maintained with a proper CGD gas feed rate. However, an overly high CGD feed rate (being 150 Nm³/t-pellet or a higher value) induces a detrimental scenario where the thermal energy recycled by the room-temperature CGD gas is insufficient to compensate for the decrease of sensible heat of the preheated feed gas from the bustle-pipe. This eventually results in a noteworthy chemical reserve zone of high H₂ content and little solid reduction in the furnace center. A large quantity of H₂ consequently remains unutilized and leaves the furnace from the top. Under the investigated conditions, the final solid reduction degree rises to maximal value when the CGD gas feed rate is 100 Nm³/t-pellet. The findings of this work revealed that the room-temperature CGD gas injection operation holds significant promise for practical applications. Full article

(This article belongs to the Special Issue Recent Trends in Extractive Metallurgy)

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13 pages, 2244 KiB

Open AccessArticle

Zinc Extraction from Primary Lead Smelting Slags by Oxidant Alkaline Leaching

by Juana María Najera Ibarra, Ma. de Jesus Soria-Aguilar, Antonia Martínez-Luevanos, Nallely Guadalupe Picazo-Rodriguez, Isaias Almaguer-Guzman, Josue Chaidez-Felix and Francisco Raúl Carrillo-Pedroza

Processes 2024, 12(7), 1409; https://doi.org/10.3390/pr12071409 - 6 Jul 2024

Cited by 1 | Viewed by 1536

Abstract

The purpose of this work is to obtain the optimum conditions for leaching the zinc contained in an industrial lead smelting slag. In this type of slag, zinc oxide, sulfide, and ferrite are contained. Zinc extraction from these compounds consists of using a [...] Read more.

The purpose of this work is to obtain the optimum conditions for leaching the zinc contained in an industrial lead smelting slag. In this type of slag, zinc oxide, sulfide, and ferrite are contained. Zinc extraction from these compounds consists of using a single aqueous medium, where oxidant alkaline leaching with NaOH and NaClO was used. The parameters evaluated during the experiment were as follows: percentage of solids, NaOH/NaClO ratio, and temperature. The maximum amount of recovered Zn obtained during the leaching was 58%. This percentage was achieved by using the following optimal conditions: temperature of 60 °C, 0.22 of NaOH/NaClO ratio, 10% of solids, and a reaction time of 40 min. The calculated values of activation energy confirmed that the rate-limiting step of the reaction using the decreasing particle model is diffusion. The maximum percentage of zinc obtained could only have been achieved if the zinc oxide and part of the zinc sulfide (both present in almost equal proportions in the sample) were leached into the alkaline aqueous medium in the presence of NaClO. Full article

(This article belongs to the Special Issue Recent Trends in Extractive Metallurgy)

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15 pages, 4120 KiB

Open AccessArticle

Hydrometallurgical Processing of a Low-Grade Sulfide Copper–Nickel Ore Containing Pt and Pd

by Elena Latyuk, Andrey Goryachev, Vitaliy Melamud and Aleksandr Bulaev

Processes 2024, 12(6), 1213; https://doi.org/10.3390/pr12061213 - 13 Jun 2024

Cited by 1 | Viewed by 1326

Abstract

The goal of the present work was to study the recovery of copper, nickel, and platinum group metals (PGMs) (Pt and Pd) from low-grade copper–nickel ore containing pyrrhotite, pentlandite, and chalcopyrite by column bioleaching followed by cyanidation. The ore sample contained the following: [...] Read more.

The goal of the present work was to study the recovery of copper, nickel, and platinum group metals (PGMs) (Pt and Pd) from low-grade copper–nickel ore containing pyrrhotite, pentlandite, and chalcopyrite by column bioleaching followed by cyanidation. The ore sample contained the following: Ni—0.74%, Cu—0.23%, Fe—14.8%, S_total—8.1%, and S_sulfide—7.8%. The Pt and Pd contents in the ore sample were 0.2535 and 0.515 g/t, respectively. Biological leaching in columns was carried out at 25, 35, and 45 °C for 140 days. A mixed culture of acidophilic microorganisms was used as an inoculum. Cu and Ni extraction depended on temperature, and at 45 °C, copper and nickel recovery was the highest, being 2.1 and 1.8 times higher than that at 25 °C, respectively. As a result, up to 35% of nickel and up to 10% of copper were recovered by bioleaching within 140 days. Bioleaching resulted in an increase in Pt and Pd recovery by cyanidation, but the effect on Pd recovery was insignificant. Pt recovery varied in the range of 3–40% depending on process conditions; Pd recovery was 44–55%. Full article

(This article belongs to the Special Issue Recent Trends in Extractive Metallurgy)

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27 pages, 7061 KiB

Open AccessReview

Review of the Chinese Aluminum Industry’s Low-Carbon Development Driven by Carbon Tariffs: Challenges and Strategic Responses

by Tianshu Hou, Lei Zhang, Yuxing Yuan, Yuhang Yang and Hongming Na

Processes 2024, 12(12), 2707; https://doi.org/10.3390/pr12122707 - 30 Nov 2024

Viewed by 2368

Abstract

Carbon tariffs are designed to prevent carbon leakage and encourage global industries to adopt low-carbon practices, which present significant challenges for China’s aluminum industry. A critical issue for China’s aluminum sector is how to effectively reduce carbon emissions while maintaining competitiveness in the [...] Read more.

Carbon tariffs are designed to prevent carbon leakage and encourage global industries to adopt low-carbon practices, which present significant challenges for China’s aluminum industry. A critical issue for China’s aluminum sector is how to effectively reduce carbon emissions while maintaining competitiveness in the face of increasingly strict carbon regulations. This review is based on an extensive examination of high-quality, authoritative research literature, industry data, and policy reports. Accurate data have been systematically summarized, and key findings from reputable studies have been extracted to support the perspectives presented in this review. On this basis, this review systematically analyzes the current status of China’s aluminum industry, emphasizing its reliance on fossil fuels, slow transition to low-carbon technologies, and the inadequate use of recycled aluminum. The potential impacts of carbon tariffs are assessed, highlighting increased carbon costs, reduced production scales, and diminished market competitiveness in foreign markets. To address these challenges, the study proposes several pathways for carbon reduction in China’s aluminum industry, including accelerating the adoption of recycled aluminum, enhancing energy efficiency, advancing low-carbon innovations, and developing supportive policy frameworks. Implementing these measures is vital for decreasing carbon emissions and ensuring the long-term sustainability of the industry amid global climate initiatives. Full article

(This article belongs to the Special Issue Recent Trends in Extractive Metallurgy)

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30 pages, 7687 KiB

Open AccessReview

Copper Anode Slime Processing with a Focus on Gold Recovery: A Review of Traditional and Recent Technologies

by Elmira Moosavi-Khoonsari and Nagendra Tripathi

Processes 2024, 12(12), 2686; https://doi.org/10.3390/pr12122686 - 28 Nov 2024

Viewed by 1993

Abstract

Copper anode slime (CAS) contains high concentrations of precious metals, particularly gold, which can reach up to 11 wt%. During copper anode electrorefining, 5–10 kg of CAS is generated per ton of copper cathode. Processing CAS is crucial for economic reasons, as gold [...] Read more.

Copper anode slime (CAS) contains high concentrations of precious metals, particularly gold, which can reach up to 11 wt%. During copper anode electrorefining, 5–10 kg of CAS is generated per ton of copper cathode. Processing CAS is crucial for economic reasons, as gold significantly contributes to revenue for both miners and custom copper smelters. This paper provides a comprehensive review of industrial processes and technologies for CAS treatment, with a focus on gold recovery, covering studies from the early 1930s to the present. It documents traditional and recent trends and analyzes the advantages and disadvantages of existing methods. Key factors affecting revenue, such as gold production lead time, in-process inventory, and first-pass recovery rate, are discussed to mitigate losses in fluctuating gold markets. CAS processing routes are categorized into two main groups: traditional hybrid routes (involving hydrometallurgy, pyrometallurgy, and electrorefining/electrowinning) and rather recent purely hydrometallurgical routes. Traditional methods can take up to 45 days, with gold recovery occurring late in the process and losses arising in the anode, cathode, electrolyte, or slag. In contrast, purely hydrometallurgical routes have total processing times of 7–8 days, achieve early gold recovery, and can attain first-pass recovery rates as high as 99%. Additionally, the hydrometallurgical routes are more environmentally friendly, with lower pollution levels and reduced energy consumption compared to hybrid routes. These findings indicate that purely hydrometallurgical routes outperform traditional hybrid methods. This paper aims to serve as a guideline for industrial CAS processing, assisting custom copper smelters in navigating challenging market conditions marked by low treatment and refining charges, with an emphasis on enhancing gold recovery to promote sustainability. Full article

(This article belongs to the Special Issue Recent Trends in Extractive Metallurgy)

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