Research
on the Gold Extraction Process of Alkaline Hot
Pressure Oxidization and Cyanidation
1. Brief Introduction：
This project is one of the national scientific
and technology key projects of the “Ninth Five
Year Plan”, “Research on the Development and Utilization
of Refractory Gold Resources (in Mining, Mineral
Processing and Metallurgy)”. This research is
targeted at the refractory gold ore in the deep
part of Jilin Hunjiang Gold Mine. This ore is
of low sulfide, extra-fine, and disseminated gold
ore. or super-fine-occluded gold ore, in which
the content of carbonate minerals in the ore is
up to 59.5%, and about 50% of the gold bearing
minerals are occluded in pyrite, arsenopyrite,
and gangue minerals in the state of extra-fine
or super-fine particulate or ultramicroscopic
state, and moreover, it also contains detrimental
impurities to gold extraction such as arsenium
and stibium. If by conventinal cyanidation method,
the leaching recovery for gold is only 47％. While
by this process, using alkaline hot pressure oxidization,
the sulfide minerals like pyrite and arsenopyrite
are effectively dissolved, and the occluded gold
is liberated so as to be recovered by cyanidation,
to achieve the goal of greatly improving the leaching
ratio.
Through lab test and scale up test, this research
developed process of alkaline hot pressure oxidation
and in-the-autoclave fast cyanidation, due to
which the national invention patent was awarded.
This technique has the following obvious technical
features:
(1) Since the pre-oxidation is conducted in an
alkaline system, it is less corrosive to the equipment,
therefore, it has simple requirements for material
quality, and is facilitate to following cyanidation
operation.
(2) An autoclave without mechanical agitation
is used, which has simple structure and is benefitial
to the diffusion and dissolution of the gas phase
in the pulp, and good for the oxidation process.
(3) Oxygen in the air is used to replace pure
oxygen, which may significantly reduce engineering
construction cost.
The original system of alkaline pressure oxidation
is utilized to conduct cyanide leaching, and the
cyanide leaching may be quick finished, which
simplifies the structure of the process and saves
capital investment, consisting one of the innovations
of this process.
2. Main Techno-economical Indices and Benefits
要技术经济指标及效益
This process mainly includes the operations of
alkaline hot pressure oxidation and pressure cyanidation
leaching, and its main parameters are as the following:
For alkaline hot pressure oxidation operation,
the temperature: 100~140C; dosage of NaOH: 20Kg/t;
air pressure: 1.5~2.0Mpa, oxidization duration:
2~3h; milling particle size: -0.007mm with 98%,
liquid-to-solid ratio 1 .8~2.0:1.
For pressure cyanidation, leaching temperature:
20~120C; air pressure: 0.5~2.0Mp, dosage of NaCN:
1.0 Kg/t; leaching duration: 20~60 min. Using
this technique, in the pre-production test plant
with a capacity of 1000 Kg/d, refractory ore of
Hunjiang Gold Mine was treated and leaching recoveries
as good as 91~93% were achieved.
3. Application and Prospects
Alkaline pressure oxidation -- cyanidation gold
extraction is suitable for treating the low sulfide
and extrafine refractory gold ores dominated by
carbonate minerals. The results of the pilot test
show that for a refractory gold ore with direct
leaching recovery being only 47%, while this technique
achieves a leaching recovery up to 91%~93%. It
not only enables these “dead” resources to be
developed and utilized, but also obtained obvious
economic benefits. There are 1000 tons of indicated
refractory resources in China to be developed
and utilized. Among these refractory gold resources,
the carbonate dominated, low sulfide, and extrafine
refractory ore takes a big proportion, and they
are distributed in Guizhou, Sichuan, Gansu, Shanxi,
Guangdong and Jilin Provinces. So this technique
has a broad application future.
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