Railing salt mined from the Chaka salt lake of
Qinghai province, China; also an important boron
minerals resource but development is restricted
by poor transport and poor mining conditions.
Panoramio
Boron minerals are mainly used to
produce borax, boric acid, various boron compounds and
elemental boron.
These derivatives are important
chemical raw materials used in a range of sectors such as
metallurgy, construction materials, chemicals, nuclear
technology, medicine, and agriculture.
Even though China is comparatively
rich in boron resources (see panel), boron mineral
products are far from meeting the demands of domestic
markets.
In 2007, China’s boron mineral
production capacity was 145,000 tonnes and borax production
capacity was 400,000 tonnes. However, imported boron products
amounted to 648,700 tonnes.
The key issue that needs addressing
is the fact that China’s richest boron mineral resource is
becoming exhausted, and is now in a stage of dilution.
The primary boron mineral exploited
today in China is ascharite, from which is produced boric acid
and borax.
Indeed, over 95% of raw material
used by the Chinese boron industry is ascharite, although,
incredibly, the mineral only accounts for 6.64% of China’s
total boron reserves.
Paigeite accounts for 58.54% of
total reserves, but its exploitation is challenged by
complicated structure and outdated processing techniques.
The salt lake deposits mainly
distributed in the Qinghai Tibet Plateau account for 33.13% of
total reserves, but development here is restricted by poor
transport and poor mining conditions.
The majority of the low grade boron
minerals, such as ludwigite, owing to their low boron content
and high impurities, have not yet been exploited.
Therefore the primary aim for
sustainable development of China’s boron industry, and in
order to meet domestic demand, is to research and implement the
processing of alternative and low grade boron mineral
resources.
Boron production
China’s boron mineral production capacity is 487,000 tpa
(at standard 12% B2O3 grade). There are
eight main boron producing areas in China, and six of these are
in Liaoning, accounting for 90% of China’s total boron
production.
In Liaoning, boron mineralisation
is mainly distributed in the districts of Fengcheng, Kuandian,
and Dashiqiao.
The largest deposits are the
Fengcheng Wengquanguo deposit, Kuandian Huayuangou deposit,
Kuandian Errengou deposit, Kuandian Luanjiago deposit, Kuandian
Wudaoling deposit, and the Yinkou Houxianyu deposit.
The massive paigeite deposit of
Wengquanguo, Liaoning hosts a demonstrated reserve of 21.85m.
tonnes B2O3 and accounts for 58% of
China’s total boron reserves.
The deposit contains on average
7.5% B2O3 and 30% Fe. It has a planned
mine life of 50-100 years, but has not been fully exploited
owing to its complicated structure.
Qinghai province is the second
largest boron mineral resource province in China with five
large boron mineral deposits: the large Chaidan, small Chaidan,
Yiliping, Xitaijinaier, and Chaerhan salt lakes, and the medium
sized Dongtaijinaier lake.
Since the 1950s, the ulexite and
pinnoite mineralisation on the surface of the Chaidan lakes has
been thoroughly exploited, while the mass of diluted minerals
at the lakes’ bottom have not been fully exploited.
By the end of the 1980s, surface
mining conducted at Temilike, Qinghai, extracted about 1,000
tonnes of ulexite, and mining recovery was about 70% and
separation recovery 60-80%. However, in general, boron mineral
development in Qinghai remains small scale.
In Tibet, although the boron
resource is very rich, and surface mining is amenable, poor
transport conditions mean that only the high grade, 20%
B2O3, material is taken and the remainder
of the resource wasted.
Overall, only a small proportion of
China’s boron reserves are exploited, and the high grade
boron reserves are becoming depleted.
The majority of the remaining boron
resources are characterised by low grade, development
difficulties, and complex processing.
Examples include: paigeite at
Fengcheng, Wengquanguo, Liaoning, magnesium-calcium borate
sediments in the Tibet salt lake, the low grade boron at the
bottom of Qinghai large Chaidan Lake, and the low grade
ascharite in the north-east.
The boron chemical industry of
China will be confronted with a severe shortage of raw
materials unless there are breakthroughs on separation
technology and new boron mineral resource exploitation.
Progress on separation
Much of the work to date on studying the development of Chinese
boron has focused on the endogenic deposits of Liaoning and
Jilin, and especially the paigeite at Fengcheng, Wengquangou,
Liaoning.
Routine separation
This process utilises gravity separation, magnetic separation,
and flotation according to the nature of the minerals.
In 2006, the Changsha Research
Institute of Mining & Metallurgy carried out separation
technology research and development on the paigeite at
Fengcheng, Wengquangou, Liaoning.
Tests were conducted on two mineral
samples of Yejiagou section ascharite magnetite type, and
Wengquangou section ludwigite magnetite.
The mineral composition was found
to be relatively complicated. The usable mineral is mainly
magnetite, and then ludwigite and ascharite, and limonite is
distributed in fragments. The metal sulphide is mainly
pyrrhotite and the gangue mineral is mainly serpentine.
During research, dry pre-separation
continuous grinding, magnetic separation, and flotation
separation was adopted where the iron and boron were separated
by high efficiency magnetic separation technology.
A boron concentrate of 14.37%
B2O3 was achieved, with a recovery of
35.03%, and a gross boron recovery of 65.74%.
The recovery process is being used
in the design of a 2.2m. tpa paigeite plant at Fengcheng
Wengquangou by Liaoning Capital Steel Paigeite Co.
The process flow sheet used by the
Liaoning Geologic Experiment Research Institute recovers boron
minerals by flotation from gravity separated tailings, takes
sulphuric acid as the modifier, soluble glass as the inhibitor,
and oxidised paraffin soap as the collector to obtain a boron
concentrate of >18% B2O3.
Zhengzhou Mineral Multipurpose
Utilization Research Institute of the Ministry of Geology and
Mineral Resources has adopted the use of spirals and a table
concentrator for recovery of ulichile in its gravity and
magnetic separation process.
At the Hunan Changning boron mine,
a relatively rare large deposit in south China, calcination is
employed which enhances the boron concentrate from 6.5% to 13%
with recovery at about 82%. However, the method has been
difficult to implement at industrial production levels.
Work on the deposit by the Changsha
Research Institute revealed that the boron minerals are mainly
holtonite and ascharite, and then ludwigite.
Processing tests showed that a
flotation separation magnetic separation combined flow sheet
realised a concentrate of 12.13 B2O3, and
a recovery of 77.55%. A single flotation separation flow sheet
yielded 12.13% B2O3, with a 76.78%
recovery.
The results demonstrated that the
methods were structurally simple and feasible for industrial
production.
Wet separation
The wet separation process mainly deals with boron bearing iron
concentrates obtained by magnetic separation. Boron is
extracted by acid leaching, boric acid is extracted from
lixivium, and then the leaching slag is magnetically separated
to obtain the iron concentrate, separating boron from the
iron.
Zhengzhou Mineral Multipurpose
Utilization Research Institute has carried out such processing
and concluded that the technique was characterised by high acid
consumption, high production costs, difficult processing of
effluent treatment, and hard to solve environmental protection
issues.
Pyrogenic separation process
The pyrogenic separation method is characterised by primary
iron making and secondary boron extraction, and can be divided
into the furnace method and the solid phase reduction fusion
separation method.
Northeastern University has put
forward its “Furnace Method” to develop paigeite: the
boron bearing iron concentrate is first obtained by separation,
and then an iron and boron separation test is conducted in a
13m3 furnace, with a processing capacity of 8,000
tpa, producing borax, boric acid, boron bearing pig iron, and
magnesium sulphate monohydrate.
Solid phase reduction fusion
reduces the 80-90% iron oxide in the raw paigeite or paigeite
processed by discarding tailings into metallic iron by
non-caking coking coal under 1,110ºC.
The reduced mineral generates the
magnetic product with metallic iron and
B2O3 slag after magnetic separation, and
then the boron bearing pig iron or boron free semi steel or
high activity boron rich slag are obtained through fusion and
separation by electric furnace.
Recovery of
B2O3 and iron is over 95%, and the boron
rich slag contains >20% B2O3 and can
be used for producing boric acid and borax.
Conclusions
With the objective to alleviate the shortage of Chinese boron
minerals by targeting low grade domestic resources and
developing suitable processing methods to improve boron
concentrate grades and recovery, the industry is focusing on
four main areas of research.
New research on separation
Compared with wet and pryogenic separation processes, the
routine separation process is characterised by technical
applicability, low production costs, and easy industrial
application. Research on new separation processes for boron is
planned to be enhanced.
New equipment
Since the majority of boron mineralisation coexists with iron
mineralisation, and that both are distributed in fine grains,
certain high efficiency fine grinding, and separation equipment
for iron separation can be applied for boron and iron
separation.
Flotation separation agents
The majority of boron minerals are distributed as fine
grains and coexist with many gangue minerals, thus separation
is difficult. Flotation separation is an efficient method for
separation of boron minerals and gangue minerals and for
improvement of boron concentrate grades.
Combined separation-smelting
Domestic boron mineralisation is complicated in structure and
coexists with many other valuable elements making separation a
challenge. With research on a combined process of separation
and smelting, elements can be recovered, thus realising the
economic value of the mineral resource to its fullest
extent.
Source: adapted from “Development and
technical progress on separation of China’s boron mineral
resource” by Prof. Yu Yongfu, presented at Forum on
Development of Boron Industry, 28 September 2010, Shenyang,
China. Yu is a member of the China Academy of Engineering and
is supervisor of doctoral postgraduates of Ore Processing
Engineering discipline at Wuhan University of Technology. He
was also senior engineer, Changsha Mining & Metallurgical
Research Institute.
China’s boron resources
China’s boron resources, which host a
demonstrated reserve of just over 49m. tonnes, are mainly
concentrated in two regions: in the north-east, in Liaoning and
Jilin provinces; and in the south-west in Qinghai province and
Tibet autonomous region (see chart).
Three main metallogenic belts host
boron minerals: the Liaoning East Jilin South Sedimentary
Metamorphic Boron Mineral Metallogenic Belt; the Qinghai-Tibet
Plateau Salt Lake Boron Mineral Metallogenic Belt; and the
Jiangsu Liuheyeshan Guangxi Mount Zhongshan Huangbao Skarn
Boron Metallogenic Belt.
Chinese boron deposits are divided
into two types: continental salt lakes and skarn deposits, with
each further divided into exogenic and endogenic
deposits.
World boron reserves (total 210m. tonnes
B2O3 content)
Source: USGS
Exogenetic deposit types:
Ascharite type: eg. Zhuanmiaogou
and Houxianyu, Liaoning.
Ascharite magnetite serpentinite type: eg. Fengcheng, Liaoning;
Xiaodonggou, Jilin.
Ascharite magnetite type: eg. Wenguangou, Liaoning.
At Wengquangou, Fengcheng, Liaoning
there is a large boron reserve of 21.85m. tonnes.
Besides the dominant boron mineral
occurrences within the main regions (see map), Tibet
also has boron bearing lake mud and lake water.
The majority of boron mineral
reserves in China are characterised by low grade, with
³12% B2O3 accounting for 90.74%, and
³20% B2O3 only 8.54%.
Over 95% of raw material used by
the boron industry is ascharite, although, incredibly, the
mineral only accounts for 6.64% of China’s total boron
reserves.
Paigeite accounts for 58.54% of
total reserves, but its exploitation is challenged by
complicated structure and outdated processing techniques.
The salt lake deposits mainly distributed in the Qinghai
Tibet Plateau account for 33.13% of total reserves, but
development here is restricted by poor transport and poor
mining conditions.
Chinese boron resource rich regions showing dominant
mineral occurrences
