As the food for the development of the steel industry, the distribution, mining, composition and transportation of iron ore are of key significance to the development of the steel industry. From a global perspective, China's crude steel production capacity has exceeded 50% of global production capacity in recent years, and it consumes more than 60% of the world's iron ore. Therefore, the situation of iron ore and related raw materials cannot be overemphasized. In the past half year, the iron ore market has been booming, but now it suddenly encounters environmental protection and production restrictions. Where will iron ore go? Everything remains the same. Let’s first understand the basic knowledge and fundamentals of iron ore.

1

Overview

China Steel’s pig iron production capacity in 2018 is conservatively estimated at more than 700 million tons, accounting for more than 60% of the world’s pig iron production capacity. The main smelting forms of pig iron include blast furnace and direct reduced iron. Among them, blast furnace iron smelting has an absolute advantage in China. Blast furnaces consume a huge amount of iron ore, because China's iron ore is characterized by low grade, few rich ores, scattered distribution, and high mining costs. This is also the reason why China imports huge amounts of iron ore every year.

Global iron ore trade volume is increasing year by year, especially China’s iron ore import volume is increasing every year. Among the iron ore imports in 2015, China imported 950 million tons of iron ore, and the world's iron ore trading volume was 1.38 billion tons, with the former accounting for 68.84%. Therefore, in the international iron ore trade, the Chinese market occupies an absolute share.

Many technicians working in the steel industry are familiar with the steel process, but their understanding of ores is very limited. This article mainly introduces you to the basic knowledge and distribution of iron ore.

1. (PbFines/PbLumps): Produced in Australia, also known as Pilbara mixed ore (operated by BHP Billiton), the grade of powder is about 61.5%, some limonite, and the sintering performance is good; The grade of the block is about 62.5%, which is limonite with good reducing properties and average thermal strength. PB powder and blocks can be mixed from fine ore from Tom Price Mine, Parabudu Mine, Marandu Mine, Brookman Mine, Namudi Mine and West Angelas Mine.

2. Yandi Fines: Produced in Australia (operated by BHP Billiton), the grade is about 58%, the aluminum content is low, it is limonite, the crystallization water is high, and it is required for mixing materials It has high moisture requirements. Because of its loose structure, good sintering assimilation and reactivity, it can partially replace Newman Mountain fine ore or Brazilian fine ore. Containing relatively low Al2O3, and both of these ore powders are coarser than Hammersley ore powder, they both have reasonable smelting properties, but poor sintering properties.

3. MacFines: The normal grade of MAC powder is about 61.5%. Currently, most of the grades supplied to the Chinese market are about 58%. Some of them are limonite, have good sintering properties, and contain 5 % of crystal water, the burning loss during ironmaking is high. As the proportion increases, the sintering rate of sinter gradually decreases. According to research by the steel mill, when the MAC powder ratio is 15%-20%, the level of sinter less than 5mm is low, and the sintering yield is the highest when the ratio is 20%.

4. Newman Fines/Newman Lumps: Produced in the Newman Mountain Mine in Newman Town, East Pilbara, Australia. It is a hematite with good sintering performance and the grade of the powder is in The grade of the block is about 62.5%, and it is produced by BHP Billiton Company in Western Australia, Australia.

5. Robe River Fines/Robe River Lumps: Produced by Robe River Iron Ore United Company in Australia; the grade is about 57.5% and contains 3%-5% compound water, which will cause High fuel rate and low productivity; it belongs to limonite and has poor sintering performance, but its sinter has good smelting performance.

6. Rocket powder: also known as FMG (FortescuemetalGroup (FMG)) powder, produced by FMG, Australia's third largest iron ore producer; it is said to be used as a rocket engine A component of fuel, so it is called rocket powder. Its grade is about 58.5%, silicon is about 4, and aluminum is about 1.5. It belongs to limonite, has good sintering performance, large reserves and high single-fired grade, and crystal water is about 8%. . The chemical composition of FMG powder is worse than that of Yangdi powder, but its sintering performance and pelletizing performance are not as good as Yangdi powder.

7. Rocket powder: Rocket powder with a grade of about 57.5% produced by FMG Company, containing about 5 silicon and 2 aluminum, and other smelting properties are the same as rocket powder. The grade of super special powder is one grade lower than rocket special powder, at about 56.5%, silicon at about 6, aluminum at about 3, crystal water at about 8.5%, and other smelting properties are similar.

8. Atlas powder: The iron ore produced by AtlasIron, Australia’s fourth largest iron ore producer, located in the Pilbara mine in Australia, has a grade of 57.5% and is limonite. , the crystal water is about 9%, the silicon content is high, about 8%, and the physical and chemical properties and smelting properties are similar to the super special powder of rocket powder.

9. KMG powder: Produced by KMG, an Australian private mining company. The mine is located in Perth, Australia. It is the closest Western Australian mine to China and close to the northernmost port of Western Australia.

The mine is expected to produce 67 million tons of ore within two years, mainly 58-59% low-grade coarse hematite, 8% silicon, 3% aluminum, 0.08% phosphorus, and 0.03% sulfur. The performance is similar to rocket special powder, but the silicon content is much higher than rocket special powder.

10. CSN powder and blocks: The iron ore produced by Brazil's CSN Company (full name: Brazilian State-owned Ferrous Metals Company) has an iron content of more than 65% and a silicon content of 1%-2%.

11. SSFT powder: A sinter powder specially formulated by Brazilian Vale Company for the Chinese market. The iron content of SSFT is about 65% and the silicon content is about 4.4%.

12. Card powder: The abbreviation of Carajas powder, the English abbreviation of SFCJ powder, the full name of SINTERFEED CArajas, the iron content is more than 65% (65-67%), and the silicon content is 1%-2%. Aluminum is about 1%, phosphorus is 0.033-0.045%, burning loss is about 1.6%, and moisture is 8-9%. The iron ore is produced in the Carajas mine in Brazil. Because the quality of the fine ore here is excellent, it will not be like the southern ore sources. It is so varied that it is very popular in the international market, and the price is higher than that of southern mineral sources.

13. Southern Brazil powder: This mine is located in the southern mineral source "Iron Four Corners" of Brazil, also known as southern Brazil powder. The main mines in the southern mining area include Itabira, Mariana, Mihas Centrals, Paraope BAl, VarGEm Grande, and Itabiritos, all in In the Iron Four Region of Brazil, the main mining method in the southern mining area is open-pit mining. This area is dominated by ferrite, with a high hematite content and an iron content of about 66%. Mainly includes SSFG powder (standard sintered powder in southern Brazil, iron grade 65%, silicon 3.2-3.8%, aluminum 1.2-1.8%, phosphorus 0.049-0.065%, manganese 0.25-0.40%, water 6.5-8.5%, burning loss 1.7% left and right), SFOT powder, etc.

14. Brazilian coarse powder: refers to Brazilian coarse-grained powder ore, which is the collective name for Brazilian coarse powder, including card powder, SSFT powder, CSN powder, southern powder, etc. The grade ranges from 65% to 58%, among which the ore powder produced in Tiiesijiao in the southeast has the best smelting performance.

15. Indian powder: refers to fine-grained powdered ore from India, but does not meet the coarse-grained particle size standards. The grade ranges from 40% to 63.5%. It belongs to hematite. The high grade has excellent smelting performance. The low grade has high silicon and aluminum content and has high smelting value.

2

Iron ore particle size classification

1. Ore particle size: The particle size and porosity of the ore have a great influence on the process of blast furnace smelting. . If the particle size is too small, it will affect the air permeability of the material column in the blast furnace and increase the resistance to rising gas. Excessive particle size will affect the heating of the charge and the reduction of the ore. Due to the large particle size, the contact area between gas and ore is reduced, making the central part of the ore difficult to reduce, thereby reducing the reduction speed and increasing the coke ratio.

2. Coarse powder: basically 0-10 mm, but generally no more than 10% above 10 mm, and no more than 35% below 0.15 mm.

3. Fine powder: basically domestically produced, below 200 mesh. Generally, coarse powder from foreign minerals is used in China, but now imported fine powder is also used, such as Russian fine powder, Ukrainian fine powder and Brazilian SSFT powder. Fine powder requires no less than 70% below 0.074mm.

4. Block ore: There are two types, one is standard block, with a particle size of 6-40 mm. The other type is the mixed block. The mixed block generally needs to be screened and crushed before it can be used.

5. Raw ore: Raw ore is mined from the mine without beneficiation or other technical processing, but the particle size of the raw ore should not exceed 300 mm. A small number of raw ores can be used directly, while most raw ores require beneficiation or other technical processing before they can be utilized. In mineral processing, the ore that enters the sorting operation after being crushed is called raw ore.

6. Powdered ore: Powdered ore, English name: fineore; minesmalls; orefines; smalls; its grade is lower than lump ore, and it needs to be separated by crushing and grinding to turn the lump into powder. To meet the grade requirements, the general requirement is 60-67%, and Pangang's grade is 57%.

3

Types of iron ore smelting

1. Acidic sinter (acidsinter):

Alkalinity (CaO/SiO2) Sinter ore less than 0.5 is made by sintering iron concentrate or rich ore powder with no or less flux. Its iron-containing minerals are magnetite and hematite, and the main bonding phase minerals are fayalite (2FeOSiO2) and fayalite (CaOFeOSiO2). Red-hot acidic sinter does not naturally pulverize during the cooling process. It has high mechanical strength, but high FeO, poor reducibility, and low reflow temperature. If this type of ore is used alone for smelting in the furnace, a large amount of limestone needs to be added; and its poor reducibility results in low blast furnace output and high coke ratio. Modern blast furnaces no longer use this kind of sinter except in some special circumstances.

2. Iron ore concentrates (ironoreconcentrates):

High-grade iron ore powder obtained by fine grinding and selection of lean iron ore. Iron concentrate is the iron and steel metallurgical raw material for the production of artificial rich ores.

According to the different iron-containing minerals, iron concentrate can be divided into magnetite concentrate, hematite concentrate and limonite concentrate; according to the different mineral processing methods, it can be divided into weak magnetic concentrate, strong magnetic concentrate and flotation concentrate. Concentrates and gravity separation concentrates, etc. Usually magnetite concentrate is obtained by processing magnetite ore using magnetic separation method; hematite concentrate is obtained by using gravity separation method, flotation method, strong magnetic separation method, magnetization roasting-magnetic separation method, or using a combined process to process hematite ore Obtained; limonite concentrate is obtained by treating limonite ore by gravity separation, strong magnetic separation or magnetization roasting-magnetic separation.

There are generally four requirements for iron concentrate:

(1) The iron content should be high. The iron content of magnetite concentrate should be above 65%, hematite concentrate should be above 60%, and limonite concentrate should be above 50%. The fluctuation of iron content is less than ±0.5%.

(2) The moisture content should be low. Moisture has a great impact on storage and transportation, ore mixing, pelletizing, etc. Generally, the moisture of magnetite concentrate should be less than 10%, and the moisture of hematite concentrate and limonite concentrate should be less than 12%.

(3) The particle size is appropriate. The iron concentrate used to produce pellets requires that the particle size smaller than 0.074mm accounts for more than 70%, and the specific surface area is preferably 1200~2000cm2/g.

(4) The lower the content of impurities (such as sulfur, phosphorus, lead, arsenic, zinc, copper and other harmful elements), the better. The general requirements are s≤0.10%～0.19% and P≤0.05%～ 0.09%, Pb≤0.1%, As≤0.04%～0.07%, Zn≤0.1%～0.2%, Cu≤0.1%～0.2%.

The acidity and alkalinity of iron concentrate (including iron ore) refers to the pH of the gangue components in the ore, specifically the ratio of calcium oxide to silicon dioxide. If CaO/SiO2 is greater than 1, it is an alkaline ore. , CaO/SiO2 is less than 1, it is an acidic mineral. If the magnesium oxide and aluminum oxide content in the ore is high, (CaO+MgO)/(SiO2+Al2O3) is greater than 1 as an alkaline ore, and vice versa, it is an acidic ore.

The pH of the iron concentrate powder is related to the ironmaking index of the blast furnace. If the blast furnace uses alkaline slag for smelting (for better desulfurization), it is hoped to use alkaline ore; if the blast furnace uses acidic slag for smelting (for better desulfurization) Blast furnace utilization coefficient and reduction of coke consumption) it is hoped to use acidic ore. At present, domestic blast furnaces generally use alkaline ores, that is, they hope that the alkalinity (CaO/SiO2 value) of the iron ore is higher.

The pH of iron concentrate powder is calculated by the following formula:

(CaO+MgO)/(SiO2+Al2O3)>1.2; alkaline ore;

( CaO+MgO)/(SiO2+Al2O3)=0.8~1.2; Autolytic ore;

(CaO+MgO)/(SiO2+Al2O3)=0.5~0.8; Semi-autolytic ore;

(CaO+MgO)/(SiO2+Al2O3)

It can also be simplified to the CaO/SiO2 ratio for evaluation.

Most of the domestic iron ores are acidic ores with low CaO and MgO and high SiO2 and Al2O3

4

The influence of harmful elements

Harmful elements usually refer to sulfur (S), phosphorus (P), potassium (K), sodium (Na), lead (Pb), Zn (zinc), As (arsenic), and Cu. Usually the requirements for iron ore in blast furnace smelting are as follows:

1), Pb

2), sulfur (S): Sulfur is the most harmful component to steel, which causes the steel to produce " Thermal brittleness”. The high sulfur content in iron ore increases the cost of blast furnace desulfurization, so the less sulfur content in the iron ore entering the furnace, the better.

3) Phosphorus (P): Phosphorus is also one of the common harmful elements in steel. It causes "cold brittleness" in steel. Phosphorus in iron ore enters the pig iron 100% during blast furnace smelting and cannot be dephosphorized even during sintering. Controlling the phosphorus content of pig iron mainly relies on controlling the phosphorus content of iron ore. Dephosphorization can only be carried out through steelmaking, which increases the dephosphorization cost of steelmaking. Therefore, the lower the phosphorus content of iron ore, the better.

4) Alkali metals: The main alkali metals are potassium and sodium. The influence of potassium and sodium on the blast furnace is not proportional. The blast furnace itself has a certain ability to discharge alkali. Alkali metals have little impact on the blast furnace within the control range. However, the alkali metal content of the iron ore entering the furnace is too much, which exceeds the alkali discharge capacity of the blast furnace, resulting in alkali metal enrichment, resulting in alkali metal content in the middle and upper blast furnace charge greatly exceeding the original level of the charge. Iron ore contains more alkali metals, which can easily cause the softening temperature to decrease and the soft melt zone to move up, which is not conducive to the development of indirect reduction and causes the coke ratio to increase. The alkali metal contained in the pellets will cause abnormal expansion of the pellets, causing serious powdering, and worsening the air permeability of the material column. Alkali metals also seriously damage the performance of coke. In addition, alkali metal compounds in the middle and upper parts of the blast furnace adhere to the furnace walls, causing thickening and nodulation of the furnace walls and damaging the brick lining. Therefore, the lower the alkali metal content in iron ore, the better.

5) Lead (Pb): Lead is almost completely reduced in the blast furnace. Because the density is as high as 11.34t_m3, it sinks under the dead iron layer and easily damages the joints of the furnace bottom bricks, which may cause Burnt through the bottom of the furnace.

6) Zinc (Zn): Zinc is easy to gasify, and zinc vapor easily enters the brick seams, oxidizes into ZnO and then expands, destroying the refractory brick lining on the upper part of the furnace body.

7) Arsenic (As): Arsenic is also one of the harmful elements to steel. It causes cold brittleness in steel and worsens the welding performance of steel.

Arsenic in iron ore is basically reduced into pig iron, affecting the quality of pig iron. In addition, arsenic volatilizes during the sintering process, which has a greater impact on the environment.

8) Copper (Cu): Copper will make steel "hot brittle", making steel difficult to roll and weld. Small amounts of copper can improve the corrosion resistance of steel. In blast furnace smelting, all copper is reduced into pig iron.

9), Titanium (titanium): can improve the wear resistance and corrosion resistance of steel. However, during blast furnace smelting, the properties of the slag will deteriorate, and about 90% of the titanium will enter the slag. When the titanium content is low, it has little effect on the slag and the smelting process. When the titanium content is high, the slag becomes thicker and has poor fluidity, which has a great impact on the smelting process and is prone to nodules. Titanium has the function of protecting the furnace. Many blast furnaces specially buy titanium ore to add to the furnace protection.

5

Introduction to the four major global iron ore indexes

There are four main influential iron ore spot indexes in the international market. One is The Platts Index from Platts, the TSI Index from Steel Business Briefing (SBB), the MBIO Index from Metal Herald (MB), and the China Iron Ore Price Index. Due to the different compilation methods of the four indexes, the quotations are not the same, and even the trend directions are also different.

The Platts Index targets mines, traders, steel mills, freight forwarders, financial institutions, etc. for price inquiries. Platts editors will contact them every day to inquire about the day's transactions and prices. How to look at it, the price considered to be the most competitive on the day is finally selected as the "evaluation price".

The TSI index pays more attention to the actual transaction price every day. Steel mills, mines and traders are all their inquiry targets, and their proportions are basically based on the three-three system. They upload the actual transaction price every day. TSI’s Analysts compiled calculations and gave equal weight to steel mills, mines and traders, and finally summarized the CIF price of imported iron ore to Tianjin Port for two grades (62% and 58%).

The MBIO index is based on the 62% grade iron ore in Qingdao Port, China (CFR), and converts all 56% to 68% grade iron ore into 62% grade.