Poor Iron Ore beneficiation in
China
/
Processo de Concentration de
Minério de Ferro pobre na
China
I Introduction
II Characteristics of Iron Ore in China
III Iron content ( TFe ) distribution
IV Influence of types of Iron Ore on
beneficiation
V Cases and direction of advance
VI Conclusion
VII Information Sources
1
George LIU
ABM, BH – 09/Dec/2014
I
Introduction
Main characteristics of Iron Ore resources in China are :
- predominance of poor ore ( some 90 % of the existent
resources ) with low TFe / iron content );
- many complex ores in which multielement coexists,
refractory and difficult for dressing;
- many co-association / interpenetration of different iron
ores in the same orebody;
- fine grain ore within a hard and compact matrix which
demand grinding to liberate the ore particles;
- geographic distribution between the iron ore resources
and the I&S mills is not rational;
- difficult to beneficiate these types of ore by
conventional physically based beneficiation methods
All these mentioned facts are part of the characteristics of
Iron Ore resources in China.
Since most of the iron ores in China are of low grade and
difficult to dress. So, during the last 15 to 20 years, because of
the strong demand of IO and lack of good domestic ore,
China was forced to work better with the poor ore.
⦁ Ore is hard, Ore is disseminated and very fine grains,
China has to find a way to crush and grind the iron ore
in a better way,
⦁ Ore is very poor, China has to develop some preselection process to maximize the efficiency
⦁ … multiple stage crushing X grinding
⦁ ….
Facing the difficulties, the IO miners and scholars defined
some beneficiation standard quite different from ours. It
doesn´t mean that they are better than us, but perhaps we
can take a look and get some lesson.
2
All the data set refers to 2012 as base and 2014 is inferred
data.
II
Characteristics of Iron Ore in China
II-01 Main types of Iron Ore Deposits
Table II-01-01 Main types of Iron Ore Deposits in China
Ore Deposit
Type
Iron Ore
Structure ( forms )
Iron Ore
Type
Gangue
Mineral
Phosed
Line / Bar
Magnetite
Quartz
Sedimentary
Granite-type
Hematite
Chlorite
Magmatic
Bulk / Band / Bar
Titano - Magnetite
Pyroxene
Differentiation
Disseminations
Ilmenite
Plagioclase
Sedimentary
Oolitic
Hematite
Pebble-types
Siderite
Bulk
Magnetite
Hydrothermal
Metasomatic
BaiYunBoe
Region
Location
%
Rese
AnShan / BenXi
5
PanZhiHua
1
Quartz
XuanHua
1
Diopside
DaYe / HanDan
Garnet
Line / Bulk / Bar
Magnetite
Fluorite
Disseminations
Hematite
Feldspar
BaiYunBoe
Pyroxene
Marine
Bulk
Magnetite
Quartz
Volcanic
Disseminations
Hematite
Feldspar
Intrusion
Reticulated
Continental
Bulk / Bar
Magnetite
Diopside
Volcanism
dissemination
Hematite
Actinolite
Intrusion
Reticulated
Siderite
ShiLu
Line / Bulk / Sheet
Magnetite
Disseminations
Hematite
DaHongShan
Iron-Chamosite
Siderite
3
Quartz
NingWu
HaiNan
By the table, it is easy to note that the main types of IO
deposits in China belong to the sedimentary metamorphic
( 56.2% )and late magmatic ( 14.0% ) deposits.
II-02 Main types of Iron Ore
Though there are many kinds of minerals with iron ( some
300 ) but only a few kinds are recognized for industrial
application with economic value under actual technical
condition. Also in China, within the main types of iron ore
deposits, only 6 types of iron ores are considered for
metallurgical usage :
⦁ Magnetite ( Fe3O4 ) : with strong magnetism, when
oxidized, it can turn to hermatite ( martite and
limonite ) but still maintaining it´s original crystalline
form. Also known as Black Ore with a black streak.
⦁ Hematite ( α - Fe2O3 ) : also known as Red Ore in
China, because of red streak.
⦁ Maghemite ( β - Fe2O3 ) : Transformation of Magnetite
under secondary change effect of oxidation
environment. Many times still maintaining the original
crystal form with magnetism. The streak may be blown.
⦁ Limonite ( Fe2O3.nH2O ) : In fact, a mixture of Goethite,
lepidocrocite, water molecules and slime. The
chemical composition may change a lot as well as the
moisture.
⦁ Ilmenite ( FeTiO3 ) : Streaks are steel grey or black, and
with no cleavage. It is weak magnetic. In the
vanadium titano-magnetite deposit in China ( such as
PanZhiHua ), the ilmenite normally occurs in flake or
granular forms inserted among the grains of magnetite.
⦁ Siderite ( FeCO3 ) : the aggregate may be coarse
grains to fine grains with yellow to light brown colour
and vitreous luster. The colour and density may change
a little bit because of substation of Fe by Mg or Mn.
4
Table II-02-01
Percentage of Iron Ore Type
Magnetite
Hematite
Siderite
Vanadium Titano Magnetite
Specularite
Mixed Ore
Limonite
Others
56%
18%
14%
5%
3%
2%
1%
1%
By the exposed table, one can see that the main dressed
iron ore in China is magnetite.
II-03 The Geographical Distribution of the main IO
resources / IO producing area
5
6
To simply the understanding, we can consider the China
Iron Ore in the following areas / regions :
⦁ Northeast China –
LiaoNing Province has the biggest orefield - AnShan
in resources in present China. Large scale ore bodies are
scattered in AnShan, which include the areas / deposits :
DaHuShan, YingTaoYuan, East & West AnShan,
GongChangLing and BenXi, with the areas / deposits :
LanFen, WaiTouShan, TongYuanBao … and some other
ore deposits near TongHua.
AnShan ore filed is the main raw material base for
AnGangl and BenGang.
The characteristics of iron ore in AnShan orefiled :
- except for a small quantity of rich ore, nearly 98% of the
reserves are low-grade ores with iron content from 20% to
40%, with an average of about 30%. For metallurgical
7
application, these ores have to be beneficiated before
the feed of furnaces;
- The ores and minerals are mainly magnetite and
hematite, partly martite and semi-martite;
- The gauge is well-distributed and dense, it is a little hard
for beneficiation and the iron ore is poor in reducibility.
- The gangue are consisted mainly by SiO2, some 40% to
50%, well distributed and hard for beneficiation;
- The iron ore of TongYuanBao / BenXi is autolyzed ores,
with the alkalinity (Ca+Mg/SiO2) exceeds 1;
- The Mn content in the ores is 1.29% to 7.5% and it can
substitute the manganese ore for use.
- The ores contain little S, P impurities.
⦁ North China –
Mainly in Hebei Provinces HeBei, ShanXi and Inner
Mongolia, scattered in regions as villages in XunHua,
QianAn, HanDan, WuAn, KuangShan of XingTai.
These raw material are bases for ShouGang, BaoGang,
TaiGang and steel plants in HanDan, XuanHua and
YangQuan.
QianLuan orefield iron ores are low-grade magnetite,
with acid gangue and low S, P impurities, easy to
concentrate.
HanXing orefield iron ores are mainly hematite and
magnetite with an iron content between 40% and 55%,
with some basic oxide gangue and some ores contain
high quantity of S.
⦁ Central South China –
Include the provinces HuBei, HuNan, HeNan,
GuangDong and HaiNan. The ore regions are mainly in
Daye, Hubei, other regions such as XiangTan in HuNan
Province, AnYang ,WuYang in HeNan, Guangdong
Province and Hainan Island have large scale ore
resources. WuGang, XiangGang and local medium and
8
small I&S mills are traditional consumers of this raw
material.
DaYe orefield is one the earliest mining iron orefields
in China, with many mines still in operation,as : TieShan,
JiShanDian, ChengCao and LingXiang. The ores are
mainly
⦁ Fe and Cu paragenetic minerals. The iron ores area
have mainly magnetite, with hematite and small
amount of chalcopyrite and pyrite. The iron content of
the ore may reach 40 to 50% with some portion as high
as 54% to 60%;
⦁ The minerals of gangue are calcite and quartz. The
gangue contains some 30% of SiO2 and;
⦁ is featured in low solvent resistance (CaO/SiO2 0.3)
⦁ and low P content (generally 0.027%), but
⦁ the S content in gangue may vary from 0.01% to 1.2%;
⦁ the gangue also contains Cu, Co and other non-ferrous
metals;
⦁ The ores are poor in reducibility and necessary to go
through sintering or pelletizing before feed in furnace
for smelting.
⦁ East China –
Iron Ore regions along the provinces AnHui, JianSu
and ShanDong. Such as the iron ore mines AoShan,
NanShan, GuShan, TaoChong, MeiShan and
FengHuangShan along Wuhu in Anhui to NanJing in
JiangSu. Besides, there are also rich iron ore resource in
JinLing Town and other places in ShanDong, which
become the raw material bases for MaAnShan I&S
Company and others.
Iron ores in WuNing region are mainly hematite with
magnetite and small amount of chalcopyrite and pyrite.
To some extend, part of the iron content of the ore is high,
( 50% to 60% ) and can be feed directly into the blast
furnaces for smelting. Poor ores go through dressing and
9
sintering before being put into the blast furnaces. The ores
of this region have a very good reducibility. But the main
problem of these iron ores are :
⦁ the minerals of the gangue, quartz, calcite, apatite
and rutile.
⦁ The ores contain high S, P impurities, P 0.5 % to 1.6% and
the S in Meishan iron ore can reach 2% to 3%
⦁ featured in certain solvent resistance, since the
average alkalinity of rich ore in AoShan and MeiShan
can reach 0.7 to 0.9
⦁ some ores contain V, Ti and Cu and other ferrous
metals.
⦁ Other non mentioned parts / regions of China –
There are other regions and different kinds of richer
iron ores besides of the above mentioned areas. Such as
provinces in Southwest and Northwest China : SiChuan,
YunNan, GuiZhou, GanSu, XinJiang, NingXia. These iron
ores regions provide raw materials for I&S mills of
PanGang, ChongGang and KunGang and also for the
other medium and small scale mills.
II-04 Iron Ore classification in China regarding to
TFe
The classification is not an international standard, mainly
applied by China because of the poor iron ore content. Take a
look at the following table :
Table II-04-01
TFe
Classification
≥ 50%
35% ≈ 50%
Rich Ore
Low Grade Ore
10
% of Resource /
Reserve
2%
25% ≈ 35%
25% ≤
98%
Poor Ore
Very Poor Ore
Source : BaiDu / Remodle : George LIU
In the past, part of the Poor Ore and most of the Very Poor
Ore suffered no beneficiation because of high mining and
concentration cost, giving no profit. But during the last decade,
due to quick and high increase in demand, China is making his
best, investing in technology, equipment and research,
enabling the poor ore and very poor ore usage.
III Iron content ( TFe ) distribution
III-01 According to the regions
Fig III-01-01 Provinces with more than 82% of the
national resources / reserve and TFe ROM
11
Table III-01-01 Provinces with more than 82% of the
resources / Reserves of IO in China
Province
1
3
2
6
7
8
5
4
9
10
11
LiaoNing
SiChuan
HeBei
AnHui
ShanXi
YunNan
ShanDong
Inner Mongolia
HuBei
GuangDong
HaiNan
Resources / Reserve
% % Acum. Abs. Ton.
21,0%
16,0%
12,0%
6,5%
6,0%
5,8%
4,7%
4,6%
4,4%
1,5%
0,4%
12
21,0%
37,0%
49,0%
55,5%
61,5%
67,3%
72,0%
76,6%
81,0%
82,5%
82,9%
15.624.000.000
11.904.000.000
8.928.000.000
4.836.000.000
4.464.000.000
4.315.200.000
3.496.800.000
3.422.400.000
3.273.600.000
1.116.000.000
297.600.000
others
Total
17,1%
100,0%
100,0%
12.722.400.000
74.400.000.000
The Fig III-01-01 should be read together with the Table
III-01-01to get a clear idea, correlated the province producer
with the resources / reserves and the TFe of ROM intervals.
Table III-01-02 Provinces with more than 80% of annual
concentrate production TFe 62%
Resources / Reserve
Annual Production TFe-62%
Province
% % Acum. Abs. Ton.
% % Acum. Abs. Ton.
1
3
2
6
7
8
5
4
9
10
11
LiaoNing
SiChuan
HeBei
AnHui
ShanXi
YunNan
ShanDong
Inner Mongolia
HuBei
GuangDong
HaiNan
others
Total
21,0%
16,0%
12,0%
6,5%
6,0%
5,8%
4,7%
4,6%
4,4%
1,5%
0,4%
21,0%
37,0%
49,0%
55,5%
61,5%
67,3%
72,0%
76,6%
81,0%
82,5%
82,9%
17,1%
100,0%
100,0%
15.624.000.000
11.904.000.000
8.928.000.000
4.836.000.000
4.464.000.000
4.315.200.000
3.496.800.000
3.422.400.000
3.273.600.000
1.116.000.000
297.600.000
16,0%
6,0%
27,0%
4,0%
6,0%
6,0%
4,0%
7,0%
2,0%
2,0%
1,0%
16,0%
22,0%
49,0%
53,0%
59,0%
65,0%
69,0%
76,0%
78,0%
80,0%
81,0%
80.000.000
30.000.000
135.000.000
20.000.000
30.000.000
30.000.000
20.000.000
35.000.000
10.000.000
10.000.000
5.000.000
12.722.400.000 19,0%
74.400.000.000 100,0%
100,0%
95.000.000
500.000.000
One can see that the province LiaoNing with the largest
resources / reserves doesn´t mean the largest IO concentrate
producer. It has more to do with the location distribution of the
I&S mills and the downstream users.
III-02 According to the feed for IO beneficiation
Table III-02-01 TFe average of ROM before Feed
for 2012-2013-2014
Average Feed in IO dressing Plants
13
2012-2013-2014
%
% Feed
ROM
Feed
Acumu
TFe
14,0%
14,0%
15,0%
15,0%
29,0%
23,0%
26,0%
55,0%
28,0%
35,0%
90,0%
33,0%
6,0%
96,0%
40,0%
4,0%
100,0%
45,0%
Average % TFe
28,50%
2015 onward
Trend
↘
↘
↗
↗
↗
↗
↗
The average TFe of ROM was dropping sharply from 2012 to
2013 , somewhere around 23.50%, and then going up quickly to
28.50% ( estimated ) in 2015 because of the fallen price of
seaborne IO and stoppage of the high production cost IO
mines. Looking forward, the overcapacity & oversupply of IO,
the dropping price will eliminate a big portion of high
production cost mines and consequently low grade IO mines.
Naturally, the considered final concentrate IO product is
compactible with the imported IO with 62% of TFe.
14
IV Influence of type of Iron Ore on Beneficiation
Essentially, we can consider two cases in China to start our
analysis :
⦁ Strong Magnetism Iron Ore beneficiation process :
This process is normally applied to low grade Magnetite
of AnShan type ore. The main characteristics of AnShan
Type ore is the strong magnetism, easy grinding and easy
classification. But in function of particle size of mainly ore
and gangue, normally multiple stage grinding ( from 2
stages to 3 stages ) is applied for fine particles and
disseminations, while one stage grinding for coarse
particles. Nowadays, most of the IO mines in China is
applying the fine screen, vibrating and regrinding
technology upgrading the TFe of concentrate from 62%
to 66%.
15
FS IV-01-01 Typical Flowsheet of Magnetite Ore dressing
– GongChangLing / AnGang
⦁ Weak Magnetism Iron Ore beneficiation process :
The involved types of Iron Ore for this process are the Red
Ores ( Hematite, Limonite, Specularite, Siderite, Martite
and mixed ore ). These ores are low grade, complex
mineral composition, very fine disseminated grains and
difficult in sorting. Anyhow, new technology improvement
16
in roasting and magnetic separation, wet strong
magnetic separation, weak magnetic floatation
separation and heavy medium separation, new machines
and new reagents helped to improve the total recovery
( metal and mass )
FS IV-01-02 Typical Flowsheet of Hematite Ore dressing
– QiDaShan / AnGang
17
FS IV-01-03 Typical Flowsheet of Beneficiation Process of
Vanadium , Titanium, Magnetic ( hematite ) 1/2
18
19
FS IV-01-04 Typical Flowsheet of Beneficiation Process of
Vanadium , Titanium, Magnetic ( hematite ) 2/2
20
FS IV-01-05 Typical Flowsheet of Beneficiation Process of
Roasted Red Ore – JiuGang
21
V Cases and Direction of advance
V-01 Some cases of success
Case 1 : QiDaShan / AnGang – Hematite Dressing
Original process : Continuous Grinding weak magnetic
separation strong magnetic separation anionic reverse
flotation / Feed Raw TFe 29.69% IO Concentrate 66.50%,
recovery 84.00%
Optimized process : Stage Grinding gravity concentration
weak magnetic separation strong magnetic separation
anionic reverse flotation / Feed Raw TFe 28.00% IO
Concentrate 68.00%, Tail TFe 11.00%
Case 2 : NanFen / BenGang – Magnetite Dressing
NanFen is one of the biggest magnetite beneficiation plant in
China.
The original process : multiple stage grinding fine screening
self circulation single magnetic separation process
The present process : one more unit operation is added at the
end, after the magnetic separation of the big diameter drum,
one more magnetic separation column is added to improve
the concentrate quality and better elimination of impurities.
The result is fantastic with TFe of concentrate steady around
68.50% and SiO2 under 5.00%.
Case 3 : JianShan / TaiGang –
In search of a better operational efficiency, cost effect,
JianShan applied a combined process of weak magnetic
separation & reverse flotation. After introducing the
modification, JianShan has a concentrate product with TFe
around 69.12% and SiO2 less than 3.56%. Specially the annual
22
economic effect is more than US$ 24.000.000.
V-02 Advance Direction - Pre-Selection : Application &
Development
Case 01 : Application of Pre-selection conception in
GongChangLing / AnGang introducing the “Dry Magnetic
Pulley” after the primary and secondary crushing system of
beneficiation plants. The already low grade intensified by the
existent mineral argilization worsen the separation index with
high mixed rocks and increasing the sorting price. So, after the
“pre-selection”, the grinded ore grade increased by 2.50% and
the discarded rock increased by 10.0%. The efficiency gain and
cost reduction is significant.
Case 02 : The Iron Ore in QiDaShan / AnGang is a marginal
very poor magnetite ore, high SiO2, low S & P, After research by
AnGang Institite, they decidsed to apply the pre-selection
process – “Dry Seperation and Discard Tail”, “stage grinding /
particle classification”, “gravity separation – magnetic
separation – middling fraction regrinding process”. The lab test
results indicate a positive result of the pre-selection – the dry
separation discard some 22% of the non magnetic tails,
reducing the feed of the downstream process. The feed raw
ore with TFe of 33.29% and the iron content of the concentrate
is around 65.69% and a tail of 12.27% with a metallic recovery
of 66.49%.
V-03 Advance Direction - Pre-Selection : Equipments &
Technology
Case 01 : Conveyor belt system with magnetic roller for preselection process of Hematite
23
Case 02 : High Pressure Roller Press ( HPRP )
Case 03 : X-Ray Radiation Separator
When ore is exposed to X-Ray, different minerals with different
atoms have different answer and different effect. Some
produces absorption, others scattering and others reflection
phenomenon. According to the defined effects, this behavior
can be applied for sorting.
Pre-selection applied this technology to eliminate the gangue
or enrich the poor ore. The working block size is between 20
mm to 300 mm. It can discard in advance some 30% to 40% of
the tail after the primary crushing so as to enrich the feed to
downstream process, such as grinding.
24
Case 04 : Fluidized bed magnetizing roasting combined with
magnetic separation method for beneficiation of low grade
iron ores of hematite, limonite, siderite and iron-containing
tailings .
The newly-developed low-temperature fluidized bed
magnetizing roasting technology, including reduction intrinsic
kinetics, process intensification, simulation and modeling,
technology development like preheating of iron ore powder,
feeding/discharging, roasted ore cooling and stable
combustion of roasting off-gas.
V-04 Energy Consumption consideration
According to the general reading, along the whole chain
of Iron Ore production - mining and beneficiation activities,
beneficiation holds the most intensive energy consumption unit
operations. As a thumb-rule, we can consider some 60% to 80%
of the energy consumption is absorbed by crushing and
grinding in beneficiation step.
25
Table V-04-01 Energy Consumption considering
only the Unit Operations of Beneficiation process
Total % of Energy
Unit
Operation
Consumption
LI
LS
average
Crushing
Grinding
Others
5,0%
50,0%
20,0%
15,0%
70,0%
40,0%
10,0%
60,0%
30,0%
It is easy to observe that between all the involved unti
operations in beneficiation process, such as crushing, grinding,
sizing, floatation, jigging, magnetic separation, conveyer
belting …. The two unit operations that deserve a deep look
and analysis are “Crushing & Grinding”. One must take care
and improve the match between the two unit operations so as
to optimize the operational cost and efficiency.
VI Conclusion
I will cite some philosophic phrases mentioned by Ms. Tian
from CIE about the direction of Low Grade Iron Ore Dressing
direction :
⦁ Collect the goods as early as possible
⦁ Discard the waste as early as possible
⦁ Discard the waste as much as possible
⦁ Discard the waste before grinding
⦁ Grinding and beneficiating in stages
As I said at the beginning, it is more important for us to
understand the philosophy, so that we can create our own
route based on the right logic.
Within the same direction, I will corroborate with some
additional phrases :
⦁ Make a good match between Cushing & Grinding
⦁ Rethink about the multiple stage unit operations ( such
26
as crushing, grinding, sizing … )
⦁ Work hard with pre-selection process
⦁ Think about the new equipment and technology
⦁ Learn with who already acquired experience
⦁ Search of the chain optimization ( cost & efficiency )
rather than segment optimization
Thanks very much,
&
Xie Xie /谢谢
VII Information Sources
⦁ USGS
⦁ UMETAL
⦁ CUSTEEL
⦁ Presentation CIE
⦁ Presentation CITIC
⦁ BaiDu
⦁ MySteel
⦁ Personal notes
27