Chlorination roasting of gold-containing arsenic pyrite (1)

In order to determine as a gold - arsenic sulphide concentrate feed - preparation stage cyanidation step chlorination roasting process results, and study the phase transition sequence of the structural transformation of arsenic pyrite produced during the heat treatment, and with a noble metal sulphide The physico - chemical properties of the calcined product .

Comparison (FIG. 1) of gaseous chlorine kinetic curves generated with silver salt quantitative method, oxidation of sulfide sulfur in an amount determined by iodine titration, arsenopyrite oxidation - chlorination roasting process and in a single - The initial temperature of the reaction in the oxidative roasting process is completely the same, and the FeAsS decomposition temperature zone is completely consistent in the above two cases, etc., and it can be confirmed that the decomposition of the solid chlorine agent in the chlorination roasting is not the result of the solid phase reaction. It is due to its interaction with sulfur dioxide generated during the oxidation of sulfides:

    2NaCl+SO 2 +O 2 =Na 3 S0 4 +Cl 2

Decomposition of sulfur present in the original gaseous active agent can be chlorine dense reinforcing structure: iron arsenopyrite only requires oxygen in air to oxidize, and the need for effective chlorination to progress - further exploded chloride And the formation of porous oxides. Therefore, the degree of oxidation of sulfide in the oxidative chlorination roasting process is more sufficient than in the case of single - oxidation roasting.

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YPC-50HM 》 Study on the phase composition of the calcined solid product by X -ray phase analysis of the cooled sample shows that the sulfide type sulphur plays a special role in the decomposition process of the solid chlorine agent. Therefore, the FeS phase, which was first discovered and rapidly disappeared during oxidative roasting of arsenic pyrite , is not fixed. Oxidation - fired chloride, after decomposition of arsenopyrite - a product is magnetite (Fe 2 O 3). It slightly exceeds the calcination temperature 600 °C At that time, it will be completely converted into the final phase of hematite (α- fe 2 O 3 ). When the presence of chlorine, arsenic arsenopyrite oxidation process, only - compounds is fixed, i.e. ferric arsenate, which is not mentioned in the reference phase φ 1, (the peak of d = 3.02 ~ 311A ) the composition of iron arsenate.

The diffraction pattern analysis shows that the φ 1 phase exists only in the crystallites with magnetite ( Fe 3 O 4 ). The arsenate may be a composite salt of magnetite and non-volatile arsenic pentoxide of the above composition, Fe 3 O 4 · As 2 O 5 or Fe 3 O 4 . This compound is the most stable of all iron arsenates in chlorine media. It can only be converted from magnetite to hematite after decomposition.

The phase transition of arsenic pyrite during chlorination - reduction calcination is similar to that of oxidative - chlorination roasting. In this case, the carbon reduction added to the charge will cause the magnetite phase to exist for a longer period of time (in 700 °C Within the temperature range). This explains in this - amount of iron arsenate temperature range is increased.

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