The pipe method is to use the pipe dissolver to make the cyanide leaching with gold under the favorable conditions of heating and pressurized oxygen supply, thereby greatly increasing the dissolution rate and leaching rate of gold, and it is difficult to handle the conventional cyanidation process. Ore.
The basic reaction of gold leaching is:
4Au+8NaCN+O 2 +2H 2 0 â†â†’ 4 NaAu(CN) 2 +4Na0H
In the above reaction, under high temperature and high pressure (oxygen partial pressure), the reaction accelerates to the right, thereby improving the leaching efficiency. Based on this, piped dissolution is used for gold leaching. This is the basic working principle of the pipeline cyanidation method.
West Druchi Chemical Metallurgical Co., Ltd. conducted a pipeline cyanidation test on gold concentrate in the laboratory.
They used a complex ore containing 17.6 g/t of gold as a test material. 300 g of the sample was slurried in 1 L of water, 3.5 g of Ca(OH) 2 was added to make the pH=11.5, 0.15 g of NaCN was added by stirring, and leaching was carried out for 24 h at normal temperature and normal pressure, and the leaching rate was 96%.
They used the same raw materials for the pipeline cyanidation test. The partial pressure of oxygen was about 2 MPa. When the temperature was 50 °C, only 30 min was leached, and the leaching rate reached 96%.
The test results show that the advantages of the pipeline cyanidation method are: fast leaching, high leaching rate, and can handle complex gold ore. It can be expected that this method is very promising.
The industrial pipe dissolver designed by Lurgi is a continuous operation autoclave. In 1978, a semi-industrial test was carried out using l0 t ore containing 10.2 g/t of gold, adding water to a solid content of 960 g/t, adding lime to adjust the pH to 11.5, slurry temperature of 30 ° C, and pressure in the pipeline of 2 500 kPa. (25.5 kg/cm 2 ), the oxygen supply is 6 kg/t ore, and the sodium cyanide is pumped into the water supply pipe dissolver by a 1 kg/t mining piston diaphragm pump. The flow rate of the slurry in the pipe is 2.5 m/s. The residence time is 8 min and the throughput per hour is 2.5 m 3 . The consumption of sodium cyanide is 0.89 kg/t ore, and the leaching result contains 0.2 g/t of gold in the leaching residue, and the dissolution rate of gold is 98%.
The pipeline cyanidation method is still in the research stage. From the perspective of development prospects, it may become the most effective means to overcome various shortcomings of conventional cyanidation.
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