Microwave Pretreatment Technique Of Refractory Gold Ores

Gold is a special metal, because it is intimate correlation with national economy and people'daily life, quantity demanded is increasing.Gold resources of easy-handled in the world is becoming less shortening with gold resources exploited and used,so people begin gradually to develop and use refractory gold resources, especially, the gold price is persitent high, and this gives a good chance of refractory gold resources, and it makes them become major resources of extracting gold.The gold of refractory gold resources makes up 60% gold storage capacities in the world.The gold of majority countries in the world are originating from hydrotherm mineral deposits except South Africa, because their compositions are very complex, it is a well-known puzzle in the world which the gold is extracted from refractory gold resources.The samples are concentrates bearing sulfur and concentrates bearing arsenic and carbon which have representations in refractory gold ores in this article.The influences are studied by microwave pretreating them, then on the base of warming-up, the change regular patterns of sulfur, arsenic and carbon in the samples with temperature change are studied, in order that qualified concentrates cyanided easily are achieved. The reaction mechanics of gold concentrates in the microwave oven are inferred by measuring reaction process.The main results are as follows.1) Microwave reactor of rectangle with three power sources is designed and made with originality innovation by using cross polarization mode according to frequency and wavelength of rectangle.lt mkes electromagnetic field distribute more homogeneous and rational in the microwave cavity, erase electromagnetic field distribute irrational phenomenon in the refitted microwave oven.There are pre-heating equipment and the gas recoveried set out of microwave oven, and protective gas may be given inside the microwave, so the samples in it don't react with oxygen. 2) With thermodynamic theory, electromagnetic field theory, chemical reaction theory and dynamics theory, what microwave can improve and strengthen chemical reaction is discussed and analysed.3) The protective gases are given in the course of the tests, they may control sulfur and arsenic in the gold concentrate not to react with oxygen of in the air, without producing harmful gases and poison materials, so it is favorable to protect environment and ecosystem.4) The warming-up speeds of gold concentrates in the microwave field are different between the change of the microwave powers and sample quantities. The warming-up speeds of gold concentrates lower with increasing sample quantities when microwave powers are rated; but the speeds run-up with microwave power raised, both of them have diffrrent zone of warming-up.5) The gold concentrates may be pre-heated and warmed up with outer heating set, so the residual heat of microwave reaction may be used to heat samples in the industry.The way of traditional heating combination with microwave heating makes the sulfur and arsenic in the gold concentrates percent dislodging higher, and react more promptly and thoroughly. The way of microwave heating may lower the reaction temperature.6) The data of sulfur, arsenic and carbon content change are gained in microwave heating tests, then the curves are fitted by using these data, and reaction models can be obtained.Because the chemical reactions can be aroused in different temperature zone, there are different reaction models at different temperature with the same samples.7) After the samples are handled in microwave oven, the tests show that the gold leaching rate of concentrates handled by microwave is higher than that of not handled by microwave with the same gold concentrate, especially the gold concentrate bearing arsenic and carbon, its leaching rate increase 164.98 percent.The dosage of sodium cyanide is lowered very much, and the dosage account for 33.33 percent and 31.25 percent that of not handled by microwave separately.This approves that microwave pretreatment refractory gold concentrate is feasible.8) The reaction courses of gold concentrates bearing sulfur and bearing arsenic and carbon are determined by a series of studies of magnetic, microwave, gravity treatment and chmicaltests.The reaction courses of gold concentrate bearing sulfur are that pyrite is changed into pyrrhotite and sulfur when the temperature is 270-430℃and the pyrrhotite changed into iron and sulfur when 430-650℃. The reaction courses of gold concentrate bearing arsenic and carbon are that arsenopyrite is changed into iron sulfide and arsenic when the temperature is 200-320℃, and pyrite changed into pyrrhotite and sulfur when 270-430℃, the iron sulfide changed into iron and sulfur when 400-650℃, the pyrrhotite changed into iron and sulfur when 430-650℃and the carbon reacts with oxygen in the air into carbon dioxide when 640-700℃.The research has guiding significance on developing and using refractory gold resources high efficiently.