Alcan Gove "G3" Expansion Project Spent Liquor Evaporation System

Alcan Inc. announced a major expansion of the Alcan Gove Refinery in September of 2004. The $2.3 billion Alcan Gove Third Stage Expansion Project, known as'G3', will increase production capacity from 2.0 to 3.8 million tonnes per annum.

HPD was awarded the project for the spent liquor evaporation system. The evaporation system at the Alcan Gove G3 expansion required innovative process and mechanical engineering to achieve essential performance guarantees.

As a critical part of the alumina production process, the evaporation system requires 100% availability outside of annual shutdowns. HPD's evaporation plant design for the G3 expansion utilizes a single train that achieves 100% availability and evaporation capacity specified by Alcan. Site erection of the units was not a desirable option due to space constraints on the job site as well as significant costs associated with the remote location.

The sheer size of the equipment presented several challenges from both a mechanical design and logistics standpoint.

Designed to concentrate spent caustic liquor, the evaporation system recovers chemicals used in refining mined bauxite in alumina production to minimize chemical makeup costs and water from this liquor to make the liquor suitable for re-digesting bauxite and maintain the plant water balance. The clean condensate produced by the system is recycled back into the process for the washing of effluents and to reduce water intake to the plant.

HPD provided complete process system design, detailed engineering, process equipment, and commissioning supervision of the sodium aluminate system. The evaporator system at the Alcan Gove expansion is one of the largest of its kind with an evaporation rate of 280 t/h.

HPD's evaporation plant design utilizes a single train that achieves 100% availability and evaporation capacity specified by Alcan with a unique, flexible design:

• On-line chemical cleaning to remove scale
• 90% Nameplate capacity during cleaning cycle
• Low-pressure steam for optimal steam economy
• Reuse of condensate in effluent washing facility processes

To overcome the remote location of the job site and space constraints for the expansion, the evaporator train was constructed off-site as pre-assembled modules (PAMs) and transported to the site by sea.

The entire system is composed of three PAMs, ranging in size from 17 to 19.8 meters in height and as long as 29.5 meters each with a combined weight of approximately 2500 metric tons.

Commissioning of the G3 caustic evaporation system occurred during the month of May 2007, with the system processing spent liquor in June 2007.

To date, the system has met mill operation needs and performance guarantees by HPD.

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