Hematite process

The most familiar of the C-frame, matrix-type industrial magnetic separators are the Carpco, Eriez, Readings, and Jones devices. The Carpco separator employs steel balls as a matrix, Eriez uses a combination of expanded met matrices, and the Readings and Jones separators have grooved-plate matrices. Capacities for this type of unit are reported to up to 180 t/h (in the case of Brazdian-hematite processing). 

Figure 5.46 The Vielle Montagne goethite process. Figure 5.47 The hematite process.

The hematite process is practised by Akita Zinc Company in Japan. A flowsheet of the process is shown in Figure 5.47. 

Fig. 9.7 Comparison of the process schemes of the hydrometallurgical zinc production with iron precipitating as jarosite and the direct pressure-leaching of zinc ore concentrate with iron precipitating as hematite. Comparison of the average noble metal yield from the jarosite and hematite processes (v. Ropenack 1991 modified by Gock et al. 1996).

With this Hematite process, the step of jarosite precipitation is avoided (v. Rbpenack... 

After the reduction of Fe(III) by zinc blend concentrate and after the separation of the solute noble metals, ferrous iron is oxidized to ferric iron which then precipitates in the form of hematite. The intermediate noble metal yields from the Jarosite and Hematite processes are compared in Figure 9.7. The quality of the hematite produced permits its utilization in the cement industry as a coloring material. For use in the steel industry, the zinc content of hematite must be reduced from 1% to 0.1%. 

Automation is an effective way to reduce costs by means of saving labor. Especially, house keeping in the cell room is most labor intensive because of the transportation of numerous d osited cathodes and blanks with manually operated cranes. We developed a new type of automatie machine that was introduced into the operations since 1994, and the last machine was installed in 1998. We developed a new process for the recovery of rare metals in the hematite process in order to inerease revenue. Production for zinc was expanded by 30,000 t/y in 1997 and by 10,000 t/y in 1999. 

The target point of the capacity expansion was set at 30,000 t-zinc annually, with minimum investment. At first, we checked bottle necks at each process, when all the equipment was in full action. Then we examined measures to increase the operation of every piece of equipment up to the maximum. Mainly, gas handling in the roasting process, iron removal capacity in the hematite process, rectifiers for zinc electrolysis, cooling capacity for the electrolyte, and a transformer at the main transforming station, were considered. 

The zinc concentrate contains iron as the main impurity. It is necessary to increase the capacity for iron removal according to the expansion of zinc production. We installed an additional autoclave of the vertical type in one of the three existing hematite lines. As a result, the capacity for iron removal increased from 2,303 t/month to 2,650 t/month. The details about the improvements concerning the hematite process were presented at the Zinc and Lead Processing Conference in 1998 (5). 

The lijima Refinery is the only refinery in the world which applies the hematite process for iron removal. This process is excellent for recovering Au, Ag, Cu, Pb and rare metals, and for the precipitation of iron oxide usable in cement production, because of its high iron content. Furthermore, we are trying to develop a new process to recover more rare metals and to purify the iron oxide to broaden its application base. 

Arsenic in iron oxide is one of the major limitations for applying this material in some industries. Since the hematite process started, we have examined many procedures to remove arsenic in the iron oxide production process. In 1998, we developed one of the best processes to purify iron oxide and reported the results (5). After that, we examined in more detail wa to reduce the investment and operating costs. Now, the process is in the final stage of commissioning. 

T. Yamada, S. Kuramochi, S. Sato and Y. Shibachi, The Recent Operation of the Hematite Process at the lijima Zinc Refinery, Zinc and Lead Processing. J. E. Dutrizac, J. A. Gonzalez, G L. Bolton and P. Hancock, Eds., The Canadian Institute of Mining, Metallurgy and Petroleum, Montreal, Canada, 1998,627-638. 

Hematite process. The leaching in the hematite process is the same as that used in the goethite process, but the precipitation of iron is conducted inside an autoclave at 180 to 200°C without neutrahzation ... 

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