Kamoto Refinery & Roaster Refurbishment

Designed

to South African Bureau of Standards specifications

5.6%

under budget when completed

8 metre-diameter

large roaster

Challenges

A 1960s cobalt-copper mine that had been shut down needed new equipment when its refinery was restarted. The roaster at the existing brownfield site needed to be replaced with higher-capacity, greenfield equipment.
Large, high-temperature fluid-bed roasters are subject to higher thermal stresses than others. This results in structural integrity problems. Here, this weakness was further compounded by the fact that the existing solids transfer boxes at the mine were maintenance-heavy and causing significant downtime.

Solutions

Two new copper-cobalt-concentrate fluid-bed roasters were designed and built to replace three existing roasters.
Feed-samples testing and extensive thermal and structural modeling of process equipment was performed. This was done to ensure structural integrity and reduce maintenance requirements.
Innovative designs were developed for tuyere plate, grillage beam, and expansion joints, improving thermal stress relief and increasing structural integrity.
Detailed fabrication drawings and equipment specifications were produced. Equipment was procured. Refractory installation and hot-commissioning support was added, leading to faster ramp-up.

Highlights

A novel roaster tuyere-plate was designed to improve thermal stress relief, and a hot shell helped avoid acid condensation and extended the roaster's service life.
Complete thermal and structural modeling of the roaster shell, roof, tuyere plate, expansion joint, grillage beams and windbox was performed.
Solids were directly discharged through the seal leg rather than transfer boxes, reducing maintenance and downtime.
Improved distribution of tuyeres enabled a more homogeneous introduction of fluidizing air to the roaster, while maintaining complete structural integrity of the vessel elements.

Project numbers

20 t/hr slurry-solids feed rate
700°C fluidized roaster
150°C fluidized calcine cooler
2 new 8-metre-diameter roasters replace 3 old ones