Environmental Engineering Reference
In-Depth Information
(France), Spent Catalyst Recycling (Germany), Taiyo Mining and Industrial Co. (Japan), Aura
Metallurgic (Germany), Sadaci (Belgium), Full Yield Industries (Taiwan), Metallurgy
Vanadium (USA), Metal-Tech (Isreal), Nippon Catalyst Cycle Co. (Japan), Moxba-Metrex
(The Netherlands), and Quanzhou Jing-Tai Industry Co. (China). The process technologies
used in these industries and the products recovered from spent hydroprocessing catalysts are
reviewed in this section. It is to be noted that for proprietary reasons, only limited information
is available in the open literature. This prevents technical/economic evaluations and/or
comparison of the commercial processes.
11.3.1 Gulf Chemical & Metallurgical Corporation Process
At GCMC's metals reclamation plant, an integrated process involving soda ash roasting and
electric smelting is used to recover all metals and alumina from spent hydroprocessing
catalysts
[566,567]
. A schematic diagram of GCMC's metal recovery process is shown in
Fig.
11.17 [567]
. Spent catalysts and sodium carbonate are roasted in a multiple hearth furnace to
burn off the hydrocarbons and some of the sulfur, and to convert the molybdenum, the
vanadium, and the remaining sulfur to water-soluble salts. The roasted material was milled,
leached with water to dissolve the molybdenum and vanadium compounds, and then filtered to
separate the solid containing alumina, cobalt, and nickel from the molybdenum and vanadium
in solution.
The Mo/V laden leach solution obtained from the GCMS process is first treated to remove
phosphorous, aluminum, and arsenic, and then, the purified solution is mixed with ammonium
sulfate and chloride to precipitate AMV. The AMV is calcined at 400-600
◦
C to decompose it
into ammonia and vanadium pentoxide. The granular V
2
O
5
is fused and quenched on a
rotating wheel to produce flakes typically containing over 99% V
2
O
5
. Ammonia is recovered
in a series of scrubbers using dilute hydrochloric and sulfuric acid and recycled for the
precipitation of AMV.
The filtrate from the AMV precipitation, containing the molybdenum, is treated with a
reducing agent, heated, and acidified to precipitate molybdic acid. After filtration and washing,
the molybdic acid is calcined to produce molybdic trioxide that is over 98% pure. In a separate
operation, molybdic acid is converted into high purity ammonium molybdate solution by
treatment with ammonia and nitric acid. The ammonium molybdate solution is sold to catalyst
manufacturers. Molybdenum and vanadium left in the filtrate from molybdic acid precipitation
are recovered by solvent extraction. The filter cake is smelted onsite in GCMC's electric arc
furnace. The products are high-grade fused alumina for refractory and abrasive applications
and an alloy containing 37 to 43% nickel and 12 to 17% cobalt, which is sold to nickel-cobalt
refineries.
