__________________________________
Foundation item: Project supported by National Natural Science Foundation of China (50574031); Scientific
Research special Foundation of Doctor subject of Chinese Universities (20030145015);
Biography: Bian Xue (1980-), Born in Shenyang, Male, Doctor.
E-mail: bxbx80_2003@163.com
1
Study on CaO decomposing bastnaesite in assistant of NaCl-CaCl
2
Bian Xue, Wu Wenyuan, Chang Hongtao, Peng Kewu, Xu Jingyu, Sun Shuchen, Tu Ganfeng
(School of Materials & Metallurgy, Northeastern University, Shenyang Liaoning 110004, China)
Abstract: Now in process of bastnaesite decomposed, fluorine gives out as gas phase. Therefore, fluorine resource
is wasted, and the environment is also polluted. In order to find new cleaning metallurgy method, the
decomposition reactions of heading mineral roasting by CaO-NaCl-CaCl
2
are studied by means of TG-DTA and
XRD methods. The relationship between decomposition ratio and four factors is studied by the quadratic
regression orthogonal analysis, and then the regression equation is obtained. The optimum process conditions are
obtained as follows: roasting temperature: 700℃, CaO addition: 15%, NaCl-CaCl
2
addition: 10%, roasting time:
60min, the decomposition ratio: 92.14%. Through analysis, because CaO is added, fluorine exists in roasting
products as CaF
2
solid, and the formation of gas phase fluorine is restrained. Thus it is shown that the method is a
cleaning metallurgy technology in this thesis.
Key words: bastnaesite, roasting, CaO-NaCl-CaCl
2
, CaF
2
CLC number: O614.3 Document code: Article ID:
Bastnaesite is the biggest one in rare earth ore reserves, and it is widely used in the industry.
Bastnaesite is the material that is used to extract Ce, La and other light rare earth, and it is also the
material that is used to produce RE-ferrosilicon alloy and mixed rare earth metal. Roasting
bastnaesite is referred in these technologies, therefore, study on roasting bastnaesite has important
significance to rare earth industry
[1-6]
.
Now, used roasting method, the producing HF release to atmosphere, and not only does it
pollute environment, but also waste F resource. Otherwise, bastnaesite can be completely
decomposed in 510℃, but a part of rare earth exists as 2CeO
2
•CeF
3
[7-9]
. CeF
3
is hard to dissolve
in leaching process, so receiving ratio of rare earth scales down. If this problem wants to be solved,
CeF
3
should be roasted to oxide in high temperature. According to document
[10]
, when roasting
temperature reach to 1000℃, bastnaesite just is roasted to rare earth oxide. In this paper, the
purpose is that the problem of F giving out as gas phase to pollute environment can be solved in
roasting process, and bastnaesite can be completely decomposed to rare earth oxide in low
roasting temperature, and rare earth receiving ratio can increase. The tenet is that a new clearing
bastnaesite decomposition technology can be exploited.
1. Experiment
1.1 Experiment materials
The bastnaesite is supplied by feitian rare earth Company in Chengdu, and habitat is
Mianning in Sichuan province. Chemical constitution is arrayed in table 1, and the other reagents
in the experiment are analytically pure.
Table1. The constitutions of bastnaesite
Constitutions RExOy CaO BaO Fe2O3 F
content/%(mass)
71.4 0.4 1.5 0.2 5.0
1.2 Experiment process
The roasting experiment is carried out in roasting furnace. The processes are that according to
scheme of regression-orthogonal designing, mixed concentrate, CaO and NaCl-CaCl
2
are mixed in
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