For some of the pyrite-type arsenic pyrite gold ore leaching difficult, in addition to the firing process flue gas SO 2 is generated, there are dust, arsenic, mercury, cadmium, lead and other harmful elements, so the addition of SO 2 while, These harmful elements should be treated.
1. Treatment and recycling of arsenic-containing soot
During any firing operation, a certain amount of soot will be produced depending on the fineness of the charge and the firing conditions. A cyclone is used to recover soot from the exhaust. However, the dust fineness cannot be recovered by a general cyclone. Unrecovered soot must comply with dust emission regulations. Formula for determining allowable dust emissions in Nevada, USA:
(1) When the dry material feeding speed is less than 30000kg/h, E=0.0193W 0.67
(2) Feeding speed of dry material above 30000kg/h E=11.78W .011 -18.14
Where E - the allowable dust emission, kg / h;
W—process feed rate, kg/h.
If lime is used to purify the exhaust gas to control SO 2 , this method can sufficiently remove the dust to meet the air discharge regulations; if the dust is not sufficiently removed, an electrostatic precipitator or a bag filter must be used to reduce the dust.
Further, as described above, the amount of gold contained in the extremely fine dust generated at the time of baking is usually higher than the average value of the thick ore concentrate, and the fine dust which cannot be recovered by the cyclone may have a large amount of gold loss. Therefore, the installation of an electrostatic precipitator or bag filter can achieve a dual purpose; reducing the amount of dust emitted into the air and increasing the recovery of gold.
2. Treatment and recycling of arsenic and mercury containing gases
Many of the hard-to-lead gold mines currently found contain very low concentrations of arsenic and mercury. The arsenic content of the Lancefield arsenic pyrite in western Australia is very high. For low arsenic, Nevada states that the maximum allowable arsenic concentration at the inlet to the roasting operation is 1/42 of the threshold (TLV), and the current threshold is 0.2 mg/m 3 . The arsenic concentration was 4.76 μg/m 3 . The allowable mercury concentration is 1/42 of the threshold value. The threshold value of mercury is 0.05 mg/m 3 , and the mercury concentration calculated therefrom is 1.19 μg/m 3 .
If lime, sodium hydroxide or sodium carbonate is used to remove SO 2 , some of the arsenic, possibly some mercury, can be removed from the exhaust. If further removal of arsenic and mercury is required to meet atmospheric requirements, wet electrostatic precipitators are effective for collecting arsenic, and the removal of mercury from the activated carbon bed impregnated with sulfur compounds in carbon can be used.
The Western Australian Mining Company is the gas cleaning system used after the two-stage fluidized bed calciner. The system consists of a two-stage hot cyclone and an air-to-air heat exchanger that cools the gas to 400 °C before entering the dual zone electrostatic precipitator (ESP). The inlet gas to the electrostatic precipitator has a soot loading of about 38 g/m 3 , and the typical outlet soot amount is below 100 mg/m 3 . After electrostatic precipitator, the purified gas was cooled to 105 °C with outside air and passed through four baghouses. Each dust room has 84 Goretex dust bags with a length of 5505mm and a diameter of 130mm. These dust bags are cleaned with reverse air pulses based on the measurement data of the differential pressure sensor. About 92% to 95% of As 2 O 3 is collected and can be sold as a commercial port. Exhaust gas from the flue behind the baghouse is lower than Australia's 10mg/m 3 arsenic, antimony , cadmium, lead, and mercury.
In solving the problem of cloth material, the polyacrylonitrile cloth bag was used initially, and then the polytetrafluoroethylene was changed. Finally, the polyphenylene sulfide (Rytou) was found to have satisfactory performance, and the physical dust removal was improved. The arsenic damage recovered As 2 O 3 .
Semi-automatic Saw Blade Pipe Cutting Machine
1. Gearbox:
The gearbox is made of casting, so it is very solid. At the same time, it is formed by the horizontal machining center for one-time processing and forming, that accumulated tolerance is small. The core component gear of the gearbox are imported from Taiwan, which is using advanced grinding and vacuum heat treatment technology, with high precision and long service life. In the use process, the noise of the machine head is small, the transmission efficiency is ensured, and the service life is long.
2. A self-lubricating bearing:
It is added at the movable joint between the head and the connecting seat, which can lubricate the connecting shaft in order to prevent the direct friction causing abrasion, so it helps to improve the working life, and accuracy that reduce the vibration of Saw Blade.
3. Regulating valve:
Regulating valve: the control valve imported from Taiwan is adopted, with high machining accuracy, stable flow control and even cutting speed. Fast return speed, improve work efficiency.
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