Nickel ores, leaching

Sulfuric acid plants are located throughout the industrialized world, Fig. 2.2. Most are located near their product acid s point of use, i.e. near phosphate fertilizer plants, nickel ore leach plants and petroleum refineries. This is because elemental sulfur is cheaper to transport than sulfuric acid. Examples of long distance sulfur shipment are from natural gas purification plants in Alberta, Canada to acid plants near phosphate rock based fertilizer plants in Florida and Australia. A new sulfur-burning sulfuric acid plant (4400 tonnes of acid per day) is costing 75 million U.S. dollars (Sulfuric 2005). 

In metallurgy, hydrogen sulfide is used to precipitate copper sulfide from nickel—copper-containing ore leach solutions in Alberta, Canada, or to precipitate nickel and cobalt sulfides from sulfuric acid leaching oflaterite ores in Moa Bay, Cuba (120) (see Metallurgy, extractive metallurgy). 

Rice, N. M. Gibson, R. W. Solvent extraction with Cyanex 301 and 302 for the upgrading of chloride leach liquors from lateritic nickel ores. Value Adding through Solvent Extraction, [Papers presented at ISEC 96], Melbourne, Mar. 19-23, 1996, 1, 715-720. 

Falconbridge Also called the matte leach process. A process for extracting copper and nickel from matte (a sulfide ore that has been roasted to remove most of the sulfur). Most of the nickel is leached out with hydrochloric acid and recovered as nickel chloride crystals. The leach residue is roasted and leached with sulfuric acid to dissolve the copper. The process has been operated in Canada and Norway since 1970. 

Hybinette A process for extracting nickel from sulfide ores. The nickel ore that occurs in Canada is a mixture of the sulfides of nickel, copper, and iron. Several methods have been used to separate these metals. In the Hybinette process, the ore is first smelted in a blast furnace, yielding a nickel-copper matte (i.e., a mixture of their lower sulfides). This is roasted to remove sulfur and leached with dilute sulfuric acid to remove copper. The resulting crude nickel oxide is used as the anode of an electrochemical cell. The nickel deposits on the cathode, which is contained in a cloth bag. Precious metals collect in the anode slime. The process was invented by N. V Hybinette in 1904 and operated at the Kristiansand refinery, Norway, from 1910. 

Dreisinger, D.B., Clucas, J.D., 2011. Low Acid Leaching of Nickel and Cobalt from Lean Iron Containing Nickel Ores , PCT Patent Filing, fritemational Publication Number WO 2011/120127 Al, January 20, 2011. 

The base case for our calculations will be the slurry that results from the acid leach of nickel ores addressed in Illustration 7.8. After depressurization, the slurry exiting the leach reactor stabilizes at a temperature of 90°C and a sulfuric acid concentration of 5% by weight. It now has to be cooled to a level acceptable for further processing, say 30°C. The tonnage rate is set at 1 ton/s, which corresponds roughly to e projected output of the Goro facility. These are the parameters to be used here. 

HydrometallurgicalProcesses. HydrometaHurgical refining also is used to extract nickel from sulfide ores. Sulfide concentrates can be leached with ammonia (qv) to dissolve the nickel, copper, and cobalt sulfides as amines. The solution is heated to precipitate copper, and the nickel and cobalt solution is oxidized to sulfate and reduced, using hydrogen at a high temperature and pressure to precipitate the nickel and cobalt. The nickel is deposited as a 99 wt % pure powder. 

HydrometaHurgical Processes. The hydrometaHurgical treatments of oxide ores involve leaching with ammonia or with sulfuric acid. In the ammoniacal leaching process, the nickel oxide component of the ore first is reduced selectively. Then the ore is leached with ammonia which removes the nickel into solution, from which it is precipitated as nickel carbonate by heating. A nickel oxide product used in making steel is produced by roasting the carbonate. 

In the acid-leaching process, the oxide ore is leached with sulfuric acid at elevated temperature and pressure, which causes nickel, but not iron, to enter into solution. The leach solution is purified, foHowed by reaction with hydrogen sulfide and subsequent precipitation of nickel and cobalt sulfides. 

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