Stage processes leaching

The process is operated in heated, batch reactors under an inert atmosphere. Two companies (Deeside Titanium, North Wales, and New Metals Industries, Nihongi, Japan) operate a one-stage process. Reactive Metals Industries Company, Ashtabula, OH, operates a two-stage process in the first stage, at 230°C, the trichloride and dichloride are formed. In the second, more sodium is added and the temperature is raised to 1,000°C. The sponge product is mixed with sodium chloride, which is leached out with dilute hydrochloric acid. Based on the work by M. A. Hunter at Rensselaer Polytechnic, New York in 1910. See also Kroll. 

Institute of Chemical Metallurgy, Division III, Staged Fluidized Leaching of Products of Chioridizing Roasting of Pyrites Cinder—Preliminary Process Design (in Chinese, unpublished), 1965-7-31 (1965). 

There has also been some interest in heap leaching of low-quality refractory ores. This is a two-stage process, as bacterial leaching of the ore must be followed by leaching with alkaline cyanide to solubilize the gold. The heap must also be washed and neutralized before the cyanide leach can be applied (103). 

Lai, Lee, Huang, and Wu (2008) developed a combined acid-leaching and fluidized-bed electrolysis process. In their study, the electrolytic cell was equipped with a glass bead medium, an iridium oxide mesh anode, and a stainless steel plate cathode. The target metals (Mo, Ni, and V) were first recovered in the first stage of leaching and then further recovered in the subsequent fluidized-bed electrolytic cell (Figure 14.9). 

Calcitization of the sulphates can be a multi-stage process (Scholle et al., 1992), which begins with (1) dissolution (or at least corrosion) of anhydrite, (2) hydration of anhydrite and gyjjsum formation, (3) dissolution of gypsum (this process can be accompanied by the formation of collapse breccia), and afterwards (4) precipitation of calcite inside free spaces and pores arisen after leached sulphates. Sometimes sulphur is the secondary product of calcitization of sulphates (see fig. 18.). 

During the initial stages of leaching, the solute loading is high and may approach the equilibrium solubility limit, while at the latter stages kinetic and mass transfer limitations are responsible for relatively lower concentration of the solute. Both coffee decaffeination and hops extraction arc popular commercial successes of this application. Further, typical applications include food processing, environmental... 

One, the CLEAR process, was investigated by Duval Corporation near Tucson, Arizona (29). It involves leaching copper concentrated with a metal chloride solution, separation of the copper by electrolysis, and regeneration of the leach solution in a continuous process carried out in a closed system. Elemental sulfur is recovered. Not far from the Duval plant, Cypms Mines Corporation operated a process known as Cymet. Sulfide concentrates undergo a two-step chloride solution leaching and are crystallized to obtain cuprous chloride crystals. Elemental sulfur is removed during this stage of the process. 

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