EVAPORATION RETROFIT WITH MECHANICAL VAPOUR RECOMPRESSION: A PATHWAY TO DECARBONISATION

The alumina industry can be viewed from both sides of the sustainability ledger – aluminium can be a green metal of the future, yet alumina production is fossil fuel based, energy intensive, and its carbon emissions are considered difficult to abate. As a low margin commodity industry, significant capital investment and technology risks associated with the energy transition are two critical challenges. In the face of these challenges, and with a likely long-term shift towards electricity as the primary energy source for steam generation, the technology of Mechanical Vapour Recompression (MVR) when coupled with green electricity becomes an attractive option. MVR has been around in other industries for decades and its high efficiency compared to other steam electrification options can offer significant operating cost and capital cost advantages.
Retrofitting MVR to existing evaporation assets provides a logical initial electrification step for an alumina refinery. MVR recovers an evaporator’s waste heat and water, with electricity replacing steam as the main energy source. An initial MVR evaporator installation can provide site learnings to de-risk future MVR installations across the refinery and be optimized to suit various evaporator designs and site constraints. This paper presents and discusses the potential retrofit options of Evaporation MVR together with the associated benefits and challenges. Potential solutions are also discussed to overcome the challenges and de-risk the retrofit.