The flux commonly used and Slag making reaction in Gold smel
2020-08-19 10:32Introduction：The flux commonly used and Slag making reaction in Gold smelting The flux commonly usedin the gold smelting process is divided into two categories: one is slag flux, mainly borax, quartz, sodium carbonate and so on, its function is to reac
The flux commonly used and Slag making reaction in Gold smelting
The flux commonly used in the gold smelting process is divided into two categories: one is slag flux, mainly borax, quartz, sodium carbonate and so on, its function is to react with base metal oxide to form slag, and the other is oxidation flux, mainly nitrite and manganese dioxide. Its function is to provide oxygen to oxidize base metals and sulfur in the charge for slagging.Borax: the molecular formula of borax is Na2B4O7. There are borax (Na2B4O7·10H2O) and anhydrous borax for metallurgical use. Borax for gold smelting is better for the latter, and the front can also be used after baking and dehydration of borax decahydrate. Because a large amount of water in borax decahydrate decomposes will reduce the furnace temperature, which is not conducive to the full use of oxidants. The melting point of borax is 741 ℃, the melting point of borax salt slag is low, and the fluidity of borax slag is good. In addition, borax has better slag properties to zinc oxide.
Quartz: the molecular formula of quartz is SiO2. The melting point of pure quartz is high , up to 1710℃, but when quartz and base metal form silicate, especially the melting point of mixed silicate system is greatly reduced.
Sodium carbonate: The molecular formula of sodium carbonate is Na2CO3. It is decomposed into Na2O and CO2 during the smelting process. It can react with SO3 to form Na2SO4 and thus make slag.
Borax and quartz are acidic fluxes and sodium carbonate is the basic flux.
Nitrostone: the molecular formula is NaNO3 or KNO3, melting point is 339 ℃, it will decompose at relatively low temperature to produce oxidation.
Manganese dioxide: the molecular formula is MnO2, and the melting point is 535 ℃. It is decomposed at a relatively high temperature to produce oxidation. In gold smelting, only one or both oxidants can be used.
Slag making includes oxidation of base metal and reaction process of slagging.
1. Oxidation reaction: under smelting conditions, the oxides formed by oxidation of base metals can now be fairly correctly determined.
When nitrite is used as an oxidant, the following reactions occur:
6Cu+2NaNO3+ heat＝3Cu2O+Na2O+2NO
3Me+2NaNO3+ heat=3MeO+Na2O+2NO (among reactionMe=Zn、Pb、Fe etc.）
S＋2NaNO3+heat＝Na2O+2NO＋SO3
When manganese dioxide is used as oxidant, the reaction is as follows:
2Cu+MnO2+heat＝Cu2O+MnO
Me+MnO2+heat＝MeO+MnO (among reaction Me=Zn、Pb、Fe etc.）
S+3MnO2+ heat＝3MnO+SO3
2. Slag forming reaction: the oxide formed by base metal oxidation can be combined with borax or quartz with different ratio, which can cause slag with different silicic acid degree. Slagging reactions are generally considered to follow the following pattern.
MeO＋SiO2＝MeO·SiO2
MeO＋Na2B4O7＝MeO·Na2O·2B2O3 (among reaction MeO=Cu2O、ZnO、PbO、FeO etc.）
SO3＋Na2CO3＝Na2SO4+CO2
Because the number of SiO2 or Na2B4O7 molecules combined with metal oxides can be one or several, the slagging reaction can be represented by the following general formula.
mMeO+nSiO2=mMeO·nSiO2
mMeO+nNa2B4O7=mMeO·nNa2O·2nB2O3
Because of the difference of m and n values, the silicic acid degree of slag is different.
