Alcan announced a major expansion of the Gove Alumina Refinery in 2004. The $2.3 billion Alcan Gove Third Stage Expansion Project, known as'G3', would increase production capacity from 2.0 to 3.8 million tonnes per annum.
Veolia Water Technologies was awarded the project for the spent liquor evaporation system. This system at the Alcan Gove G3 expansion required innovative process and mechanical engineering to achieve essential performance guarantees. Veolia provided complete process system design, detailed engineering, process equipment, and commissioning supervision of the sodium aluminate system.
Designed to concentrate spent caustic liquor from the Bayer process, the evaporation system recovers chemicals used in refining mined bauxite in alumina production. This significantly minimizes chemical makeup costs as the concentrated liquor is suitable for redigesting 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.
As a critical part of the alumina production process, the evaporation system requires 100% availability outside of annual shutdowns. Veolia's HPD® evaporation plant design for the G3 expansion utilizes a single train that achieves 100% availability and evaporation capacity specified by Alcan.
The unique, flexible design allows for:
- Online chemical cleaning to remove scale
- 90% Nameplate capacity during cleaning cycle
- Lowpressure steam for optimal steam economy
- Reuse of condensate in effluent washing facility processes
Modular Supply Expertise
The evaporator system at the Alcan Gove expansion is one of the largest of its kind with an evaporation rate of 280 t/h. The sheer size of the equipment presented several challenges from both a mechanical design and logistics standpoint.
Field 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. To overcome these obstacles, the evaporator train was constructed offsite as preassembled modules (PAMs). The system was fabricated and assembled in both Thailand and Vietnam 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 2,500 metric tons.
Commissioning of the G3 caustic evaporation system occurred with the system processing spent liquor in 2007.
To date, the system has met mill operation needs and performance guarantees.