Conference Agenda

Who does not remember the Toyota Landcruiser that the team of Top Gear mistreated in their show? Despite all the abuse, each time the Toyota was brought back to life with a few simple tools. The Fume Treatment Centre (FTC) of Danieli Corus has many similarities; it does not matter what you do to it; it will perform. The original Pleno design was developed by a former maintenance manager at a primary aluminium smelter in the eighties. At that time, this maintenance manager was not pleased with the equipment given to him, so he decided to manufacture his own gas cleaning equipment. Currently the fifth generation of the Pleno Design is on the market. Experience shows that hot temperatures, sparks, tar, dust will all be handled. Also, poor operation or lack of maintenance has little effect on the operation of the FTC. In the paper we will show examples of the performance of the FTC during extreme conditions and how any damage could be repaired easily.

The Rhodax® process is the result of two parallel developments started in early 1990s. In early 2000s, Fives and Aluminium Pechiney (AP now Rio Tinto) joined their R&D efforts and co-patented the SCAP-RHODAX® process.

This paper summarizes in a first part, what are the key initial characteristics of this process, how it performed over the past 25 years.

In the second part, it describes how the return on experience from the customers, forced the evolution of this technology to address new challenges faced with either variability in raw coke properties, maintenance issues, continuous amperage creeping resulting in high anode current density requiring even higher stable anode quality or again better energy efficiency to lower their carbon footprint.

Then the paper presents the studied technology developments (equipment, process and digitization), those which have been successfully implemented and also those requiring further R&D work.

Extended surface filter bags (ESB), also known as StarBagsᵀᴹ, have been used for nearly twenty years in primary aluminium smelter gas treatment centres (GTC). They have repeatedly been used as a cost-effective way to increase the capacity of an existing GTC when potlines increase metal production with line amperage increase, thereby debottlenecking production increases without the need for capital upgrade in the GTC.

With the ever-increasing loads in GTCs with each incremental smelter amperage increase, the original and subsequently modified designs of ESB filters reached the limit of their capability in several primary aluminium smelters towards the end of the last decade. Low resistance, high flow PrimaFlow® ESB filters were developed to address this design limitation and continue to push through performance barriers in several aluminium smelter GTC applications.

Carbon bake fume gas treatment centres (FTC) sometimes also undergo increasing load with primary aluminium smelter amperage increases. FTC filter baghouses have their own technical challenges, meaning gas flow rate and filter differential pressure becomes increasingly difficult to maintain over the life of the FTC baghouse filters. Low resistance, high flow PrimaFlow® ESB filters have now also proven to be a cost-effective solution in aluminium smelter FTC baghouses, with long-term operational performance able to be maintained.

This paper will discuss the latest comparisons in computation fluid dynamics (CFD) modelling of ESB filter designs, which help explain the extended application capacity of the PrimaFlow® filters. This extended application capacity will be shown in the long-term operational performance of PrimaFlow® ESB filters in an aluminium smelter prebaked anode FTC application.

The anode baking process is highly energy-intensive, requiring approximately 2 GJ/t of baked anodes. In this process, refractory walls are heated by direct gas injection from the top of the furnace to bake the anodes. However, combustion emissions, particularly nitrogen oxides (NOx), have become a significant concern in industries that rely on fossil fuels. NOx generation in kilns results from a combination of thermal NOx, fuel NOx, and pitch volatiles combustion efficiency. Thermal NOx are formed during combustion of gas and air mixture at high baking temperatures (>1,170 °C) inside the flue. ALBA Kiln-5 had been experiencing high NOx levels (>250 mg/Nm3) since its inception, which was a major issue. Under the Environmental, Social, and Governance (ESG) initiative, reducing NOx emissions was a top priority for ALBA. This paper presents the experiences of ALBA in successfully reducing NOx emissions from >250 mg/Nm3 to below 100 mg/Nm3 consistently. This achievement was made possible through various in-house trials and optimization of baking parameters, and the installation of ultra-low NOx burner nozzles in all fire groups. The introduction of specially designed low NOx burner nozzles resulted in a significant reduction in NOx emissions without compromising the baking process, anode quality, or thermal homogeneity inside the flue wall.