Environmental Engineering Reference
In-Depth Information
sulfates are used for production of Ni and Co powders. The alumina residue is used for
production of the refractories. Recovery efficiencies of more than 90% for Mo and Co are
achieved in this process.
11.3.7 Quanzhou Jing-Tai Industry Process
In China, Quanzhou Jing-Tai Industry Co. has developed a simple process for the recovery of
metals from spent hydrotreating catalysts using H
2
O
2
for leaching
[694]
. The process first
subjects the catalysts to a low-temperature calcination step, followed by grinding of the
calcined material. The ground material is then leached with 10-20% v/v hydrogen peroxide to
recover metals, such as Mo, V, and Ni or Co. This step has a selectivity that is greater than
95% for the metals. The undissolved residue, which contains mainly Al
2
O
3
and SiO
2
, can be
dewatered and used in the production of masonry bricks. The pH of the leach liquor is then
adjusted to between 0.5 and 2.5 by adding dilute sulfuric acid to co-precipitate Mo and V with
a recovery rate of greater than 99%. The lean liquor contains mostly dissolved Ni or Co, which
can be recovered through precipitation at a pH of between 8.5 and 9.5 by caustic additions.
The final liquor is then sent to an ion exchange step for final recovery and cleanup of residual
metals. The effluent is then discharged after a simple waste water treatment process, which has
been found to meet all environmental requirements. The entire process has been found to be
simple, cost-effective with minimal environmental impacts while achieving the goal of
complete resource recovery from spent catalysts commercially.
11.3.8 Metallurg Vanadium Process
Metallurg Vanadium (Ohio, USA) uses a proprietary pyrometallurgical process to convert
metals (V, Ni, Mo, Co, W) present in spent hydroprocessing catalysts to alloys, such as
ferrovanadium, (FeNiMo), and other ferroalloys, which are sold to steel companies
[695]
.
11.3.9 German Processes
In Germany, there are three metal reclamation companies, namely GfE Metalle and
Materialien GMBH, AURA Metallurgie GMBH, and spent catalyst recycling (SCR) GMBH.
Both pyrometallurgical and hydrometallurgical processes are applied at GfE's metal recovery
plant
[696]
. Hydrometallurgical process is used to produce molybdenum chemicals, Co/Ni
solution, and aluminium oxides. The pyrometallurgical process serves for the generation of
cast vanadium concentrate (CVC) from which high purity vanadium chemicals are extracted.
At SCR, spent metal catalysts and metal residues containing Ni, Co, Mo, V, and W are
processed to reclaim the metals. Process details are not available for this plant
[697]
. Aura's
metal recovery facility at Helba, Germany, has been in operation since 2001 with a capacity to
treat up to 10 000 tons of spent HDS catalyst (NiMo/Al
2
O
3
and CoMo/Al
2
O
3
) per year.
