Experimental Study About The Cycling Condition In Catalytic Oxidation Pretreatment Of The Refractory Gold Ore With NOx In Threephase Fluidized Bed

With the decling of the easily leachable gold ores,developing a process which is ecnomic and practial and high efficiency to pretreat the refractory gold ores is imminent. Supported by the "863" fiancial,We had invented a process which was the catalytic oxidation pretreatment of the high arsenic gold concentrate in the threephase fluidized bed. After the initial design process, research, innovation, which had been formed and proved that the process was an economical, environmentally friendly and efficient pretreatment process to the refractory gold ores through a serials of tests. However, we discovered a problem that was the process generated much NOx owing to using HNO₃ as the oxidant when the process was running,which was that the conventional absorption process could not meet the process's requirenments.That may lead to the pressure in the system higher than the atmospheric perssure,which was likely to cause gas leakage,pollution and low utilization of the HNO₃. Therefore, developing a highly efficient NOx absorption process not only meet the regeneration requirements of HNO₃, but also to maintain the system atmospheric pressure or slightly negative pressure becomed urgen problemt.According to studying a large number of documents and the characteristics of the process of the catalytic oxidation pretreatment of the high arsenic gold concentrate in the threephase fluidized bed, a pneumatic spray device has been invented, which does not increase the cost of threephase fluidized bed operation and additional Power equipment, only rely on the power equipment diaphragm compressors owned by the fluidizedbed process.In the article, the feasibilty of the pneumatic spray device used in the fluidezed bed firstly is discussed through to simulate the operationg conditions of the catalytic oxidation pretreatment of the refractory gold ores in the threephase fluidized bed and find that the pneumatic atomization technology can meet the NOx absorption requirements and the most appropriate diameters of the jet tube are 0.5mm and 0.8mm, others can't meet the requirements.Sceondly, making use of the air compressors with the air and water as media tests the basic parameters of pneumatic atomizer, which the gasliquid volume ratio is selected as the reference index and derive that the liquid volume ratio is relatively smaller, when the Jet pipe diameter closes to the spray pipe diameter and each gasliquid jet nozzle has optimum pressure in which the liquid volume ratio is minimum and the optimum pressure has a certain relationship with the its critical pressure and the jet height. Thridly, making use of diaphragm compressor with NaNO₂,H₂SO₄ as the raw tests the temperature, the HNO₃ concentration of the absorption solution, the gasliquid contacted area and the fog zone height to the absorption effect and obtain that the gasliquid volume ratio can be as an index to measure and forecast the effect of the pneumatic atomization absorpting NOx and the conclusion from the air and water as media can be directly applied to the NOx absorption and when the HNO₃ concentration of the absorption solution is 4%8%and the fog zone height is not less than 40cm and the Jet pipe diameter closes to the spray pipe diameter,the absorption efficiency is highest,which is about 75%,but in the range of 60℃, the temperature has no significant effect on the absorption efficiency.Finally some debugging tests have been done by using the pneumatic atomizer in the threephase fluidized bed to pretreating the refractory gold ores and draw that when the pretreating effect is best,the pneumatic atomizer parameters are that the spray height is 0.74m, the diameter of the Jet pipe is 0.8mm,the diameter of the spray pipe is 0.5mm,the spray pressure is 0.170.20 mpa.