Anders Kenneth Sorhuus

Possible Use of 25 MW Thermal Energy Recovered from the Potgas at ALBA Line 4

Many aluminium smelters currently choose amperage increase as a way to boost production over costly new plants. However, the increased pot amperage gives higher gas temperatures and higher gas flows to the Gas Treatment Centers (GTCs). The higher gas flows give capacity problems for the existing GTC’s and high gas temperatures (above 115°C) lead to poor scrubbing efficiency in the dry scrubbers. For more than seven years Alstom has successfully developed and tested heat exchangers to cool the pot gas including self-cleaning heat exchangers that has been in continuous operation for 6 years.

Pot Gas Treatment at High Gas Temperatures

HF regeneration due to submicron fluoride particles trapped inside the filter cloth reacting with the humidity in the pot gas is one likely mechanism that explains why the HF emissions increase with gas temperature and humidity in the dry scrubbers. A significant temperature effect is observed and gas cooling is in many smelters today necessary to keep the emissions under control. The GE heat exchanger (HEX) technology is one of the technologies that are now built and operated in full scale several places in the world. Results from the first full scale GTC installation document the positive effect of the cooling for the Abart GTC technology installed. The HEX cools the temperature with more than 25 °C down to less than 110 °C and HF emissions in the range 0.2–0.3 mg/Nm3 are measured at ambient temperatures higher than 40 °C, and high humidity.

AHEX‐A New, Combined Waste Heat Recovery and Emission Control System for Anode Bake Furnaces

Alstom has developed a new Fume Treatment Center (FTC) for improved emission control of Anode Bake Furnaces. The new compact FTC eliminates the conditioning tower with its use of compressed air and water with a patented heat exchanger system (AHEX) specially developed for the anode baking process. The adsorbent (alumina) is injected upstream the AHEX. This eliminates additional reactor stages downstream, and keeps the heat exchanger tubes free from fouling.

HEX Retrofit Enables Smelter Capacity Expansion

Aluminium Bahrain (Alba) is one of the largest producers of primary high quality aluminium in the world, and continues to consider further expansions such as the planned new line 6. In parallel the amperage on the existing AP30 pot lines 4 and 5 will be increased further.

Innovative Distributed Multi‐Pollutant Pot Gas Treatment System

Gas Treatment Centers (GTC) are traditionally arranged in the courtyard between pot rooms and handle vast quantities of pot gas (3 – 4 million m3/h) in a large number of filter compartments (15–30) with demanding space requirements and challenging control of operation.

Improved Abart Gas Treatment and Alumina Handling at the Karmøy Technology Pilot

At the Karmoy Technology Pilot (KTP), Hydro will aim to achieve significant step changes in the specific energy consumption and at the same time meet the lowest emissions. These goals will require energy improvements of all aspects of the production including the power for operating auxiliary equipment. In this process, Hydro selected to combine and integrate the entire material handling and gas treatment systems utilizing the Abart gas treatment system. The paper will describe the solutions selected including the dual duct systems for pot operation, anode cooling box suction, heat exchangers, the Alfeed alumina distribution, fluoride transport, and crushed bath mixing and transport. Significant technology improvements related to the new integrated heat exchanger will be shared including energy recovery potentials and improvements in HF absorption due to the improved pot gas and alumina mixing in the GTC reactors.

Alumina Handling in the Smelter — From Port to Pot

Alumina is the main raw material for primary aluminium production and the smelters rely on continuous, steady streams of alumina to the pots. At the pot, variations in the alumina quality shall be minimized. Fluoride content, particle size distribution, attrition, segregation, powder flowability and impurities all are important parameters that are affected and partly controlled by the alumina handling and treatments including the alumina silo storage, transport, screening and gas treatment /alumina enrichment systems upstream the pots.

Abart CDS — A New Compact Multi-Pollutant Pot Gas and Alumina Handling System

A new modular Abart CDS has been developed that integrates silos, alumina handling, heat exchangers, fans, SO2 scrubber and stack into a compact and efficient multi-pollutant pot gas treatment and recovery technology with incomparable footprint. The system is based on standardized modules that allows for short delivery time and early start-up. Each module includes an individual fan and optional SO2 scrubber located directly on top of the module. This compact design reduces overall pressure drop and energy requirements for operation of the fans. This paper updates the previously reported experiences from the first full scale installation in Norway with new results on the integrated SO2 scrubbers that were retrofitted in 2012/13.

Experiences with Alstom’s new Alfeed system at Emal

Alstom’s new pot feeding system (Alfeed) was successfully installed and commissioned on Emal’s 756 pots during 2009–2010.