The Saudi Arabian Mining Company (Ma’aden) and Alcoa (USA) joint venture is the largest fully integrated aluminium complex in Ras Alkhair, Kingdom of Saudi Arabia, and consists of an alumina refinery, an aluminium smelter and a rolling mill. The Aluminium smelter commenced operation on 12 December 2012 with 720 AP 37 technology reduction pots in two potlines at 370 kA. The potlines were upgraded to AP 40 from 2019 to increase amperage to 410 kA producing 805 kt/a of aluminium.

In November 2022, Ma’aden experienced a significant operational challenge when 304 pots were cut out due to a series of anode collapses and anode fall-offs in addition to other operational challenges. Remarkably, there was no power shutdown of the potline due to various preventative actions, taken to save the potlines. During five months of continuous pot cleaning, inspections and relining, all affected pots were back into operation safely at zero lost time incident, and production targets were back to normal. This paper explores the various factors that led to the sudden pot stoppages in pot operations, which significantly impacted metal production, and it gives details of the successful recovery. The incident provided a unique opportunity to perform extensive multiple cell autopsies, which in turn facilitated enhancements in cathode design, the assessment of diverse preheating techniques, and the examination of lining materials performance in addition to anode quality improvement.

It is well known that off-gases from electrolytic production of aluminium emit perfluorocarbons (PFCs). Several studies have concluded with high emission figures for CF4 and C2F6 during periods of anode effect (AE). Various methods for quantifying emissions have been launched, and the most widely used one today is the IPCC (2006) Tier 2 approach, which relies heavily on developed factors that have their basis in traditional measurements using FT-IR. However, the FT-IR method has limited sensitivity and is not ideal for analysis in potlines with low AE frequency. In the latter, questions have also been asked as to whether PFCs can be formed under operating conditions with no indication of AE. We have therefore extracted gas at the outlet of an electrolysis cell without any sign of AE to investigate the composition and level of PFCs in such an off gas. The measurements showed surprising results and revealed the presence of several PFCs, and hydrofluorocarbons (HFCs) not reported before in primary aluminium production. In total, nine compounds were identified and quantified by using sophisticate sampling and analysis techniques. Hypothesis about their formation will be presented.

To obtain reliable perfluorocarbon (PFC) measurement results requires expertise and competence in the measurement methodology and knowledge of the smelting technology. We enumerate different measurement methods that have been used to measure PFC emissions. The Fourier Transform Infrared method is the most versatile of all the methods and gives the most information about the smelting process. It has the best temporal resolution making 10 interferometer scans each second and can measure low voltage emissions at the same time as anode effect emissions. Both authors have extensive experience measuring PFC emissions (CF4 and C2F6) at aluminum smelters worldwide. We will present available measurement technology with a checklist to ensure accurate and reliable measurements.

Due to increasingly high sulphur content in carbon materials for electrolysis and using fuel oil for calcination of alumina, more and more smelters equip their gas cleaning facilities with wet scrubbing for catching sulfur compounds. Such gas wet scrubbing of aluminium reduction produces a spent solution containing fluorine and sulfur compounds, coal dust, etc. Due to increasing contents of said compounds, these solutions should be disposed to the tailing retention dyke suitable for liquids of a high class of hazard. A technology of processing the wet scrubbing spent solutions was developed to produce recycled cryolite, soda solution for gas scrubbers and soda-sulfate mixture. Said mixture contains ≥ 95 % berkeit Na2CO3×2Na2SO4 and is characterized by good whiteness. Soda-sulfate mixture is widely used in production of synthetic detergents and cellulose and paper. Pilot facility was built at Krasnoyarsk aluminium smelter to test the suggested technology. Scaling up of the facility allows preventing the extension of tailing disposal areas of aluminium smelters. The pilot facility produces the soda-sulfate mixture of > 80 % whiteness. Jointly with a chemical works, detergent production was established resulting in successful solution of the problem.