2009/05/14

A Brief Review of Iron Ore Beneficiation & Trace Elements

Beneficiation is a variety of processes whereby extracted ore from mining is reduced to particles that can be separated into mineral and waste, the former suitable for further processing or direct use.

The beneficiation process improves the chemical or physical properties of the ore so that metal may be recovered profitably.

Based on this metaphor, the term has come to be used within an economic development and CSR (corporate social responsibility) context - to describe the proportion of the value derived from asset exploitation which stays 'in country' and benefits local communities.

For example, in the diamond industry, the beneficiation imperative argues that cutting and polishing processes within the diamond value-chain should be conducted in-country to maximize the local economic contribution

Iron Ore Trace Elements: Effects and Remedies (Silicon, Phosphorus, Aluminum and Sulfur)
The inclusion of even small amounts of some elements can have profound effects on the behavioral characteristics of a batch of iron or the operation of a smelter.

These effects can be both good and bad. Some catastrophically bad.

Some chemicals were deliberately added. The addition of a flux made a blast furnace more efficient.
Others were added because they made the iron more fluid, harder, or some other desirable quality.

The choice of ore, fuel, and flux determined how the slag behaved and the operational characteristics of the iron produced.

Ideally iron ore contains only iron and oxygen. In nature this is rarely the case. Typically, iron ore contains a host of elements which are often unwanted in modern steel.

Silicon

The major effect of silicon is to promote the formation of gray iron. Gray iron is less brittle and easier to finish than white iron. It was preferred for casting purposes for this reason. Turner (1900:192-7) reported
that silicon also reduced shrinkage and the formation of blowholes, lowering the number of bad castings.
Silica (SiO2) is almost always present in iron ore. Most of it is slagged off during the smelting process.
But, at temperatures above 1300/C some will be reduced and form an alloy with the iron.

The hotter the furnace, the more silicon will be present in the iron.
It is not uncommon to find up to 1.5% Si in European cast iron from the 16th to 18th centuries.
Phosphorus
Turner felt the ideal iron had 0.2-0.55% phosphorus
Phosphorus is a deleterious contaminant because it makes steel brittle, even at concentrations of as little as 0.5%. cannot be easily removed by fluxing or smelting, and so iron ores must generally be low in phosphorus to begin with.
The iron pillar of India which does not rust is protected by a phosphoric composition.
Phosphoric acid is used at a rust converter because phosphoric iron is less susceptible to oxidation.
Aluminum
Aluminum Is very hard to reduce. As a result aluminum contamination of the iron is not a problem.
However, it does increase the viscosity of the slag (Kato and Minowa 1969:37 and
Rosenqvist 1983:311). This will have a number of adverse effects on furnace operation. The thicker slag
will slow the descent of the charge, prolonging the process.
High aluminum will also make it more difficult to tap off the liquid slag. At the extreme this could lead to a frozen furnace.
There are a number of solutions to a high aluminum slag. the first is avoidance, don't
use ore or a lime source with a high aluminum content. Increasing the ratio of lime flux will decrease the viscosity (Rosenqvist 1983:311).
Sulfur

Sulfur dissolves readily in both liquid and solid iron at the temperatures present in iron smelting. The effects of even small amounts of sulfur are immediate and serious. Today iron with over 0.03% sulfur is avoided Sulfur causes iron to be red or hot short (Gordon1996:7)

Hot short iron is brittle when hot.

This was a serious problem as most iron used during the 17th and 18th century was bar or wrought iron.

Wrought iron is shaped by repeated blows with a hammer while hot. A piece of hot short iron will crack if worked with a hammer. When a piece of hot iron or steel cracks the exposed surface immediately oxidizes. This layer of oxide prevents the mending of the crack by welding.

Large cracks cause the iron or steel to break up. Smaller cracks can cause the object to fail during use.
The degree of hot shortness is in direct proportion to the amount of sulfur present.
Today iron with over 0.03% sulfur is avoided. In modern operations, sulfur is unwanted because it produces undesirable sulfur dioxide gases in the flue emissions from a smelter and interferes with the smelting process. Sulfur (S) is a frequent contaminant in coal and coke.

Iron sulfide (pyrite, FeS2), is a common iron ore. It is also present in small quantities in many ores.

It was the presence of sulfur that prevented the use of coal in blast furnaces until
1709.
They were one of the first worked out by iron makers.

To convert an oxide of iron to metallic iron it must be smelted or sent through a direct reduction
process Chemical reduction, or smelting, is a form of extractive metallurgy.

The main use of smelting is to produce a metal from its ore.

This includes iron extraction (for the production of steel) from iron ore, and copper extraction and other base metals from their ores.

It makes use of a chemical reducing agent, commonly a fuel that is a source of carbon such as coke, or in earlier times charcoal, to change the oxidation state of the metal ore; however, plants for the electrolytic reduction of aluminum are also generally referred to as smelters.

The carbon or carbon monoxide derived from it removes oxygen from the ore to leave the metal.

The carbon is oxidized, producing carbon dioxide and carbon monoxide.

As most ores are impure, it is often necessary to use flux, such as limestone to remove the accompanying rock gangue as slag (also called scoria or cinder).

Pre Test Review: Iron Ore Beneficiation & Trace Elements
1.
Beneficiation Is a variety of processes whereby extracted ore from mining is reduced to particles that can be separated into mineral and waste,the former suitable for further processing or direct use.

2.
Chemical reduction, or smelting, is a form of extractive metallurgy.

3.
To convert an oxide of iron to metallic iron it must be smelted or sent through a direct reduction process. The main use of smelting is to produce a metal from its ore.This includes iron extraction (for the production of steel) from iron ore.

4.
Most ores are impure, it is often necessary to use flux, such as limestone to remove the accompanying rock gangue as slag (also called scoria or cinder)

5.
The inclusion of even small amounts of some elements can have profound effects on the behavioral characteristics of a batch of iron or the operation of a smelter.

6.
Some chemicals are deliberately added; Others are added because they make the iron more fluid, harder, or some other desirable quality.

7.
Ideally iron ore contains only iron and oxygen but in nature this is rarely the case. Typically, iron ore contains a host of elements which are often unwanted in modern steel.

8.
The major effect of silicon is to promote the formation of gray iron.which is preferred for casting purposes.

9.
Silicon also reduced shrinkage and the formation of blowholes, lowering the number of bad castings.

10.
Gray Iron is less brittle and easier to finish than white iron.

11.
The hotter the furnace, the more silicon will be present in the iron. It is not uncommon to find up to 1.5% Si in European cast iron from the 16th to 18th centuries.

12.
Silica (SiO2) is almost always present in iron ore. Most of it is slagged off during the smelting process. But, at temperatures above 1300/C some will be reduced and form an alloy with the iron.

13.
Phosphorus is a deleterious contaminant because it makes steel brittle, even at concentrations of as little as 0.5%. cannot be easily removed by fluxing or smelting.

14.
the ideal iron should contain no more than 0.2-0.55% phosphorus

15.
Phosphoric acid is used at a rust converter because phosphoric iron is less susceptible to oxidation. The iron pillar of India which does not rust is protected by a phosphoric composition.

16.
Aluminum is very hard to reduce. As a result aluminum contamination of the iron is not a problem.

17.
Aluminum increases the viscosity of the slag resulting in a number of adverse effects on furnace operation.

18.
High aluminium makes it more difficult to tap off the liquid slag which can lead to a frozen furnace.

19.
There are a number of solutions to a high aluminum slag. the first is avoidance, don't use ore or a lime source with a high aluminum content. Increasing the ratio of lime flux will decrease the viscosity.

20.
The effects of even small amounts of sulfur are immediate and serious.

21.
Today iron with over 0.03% sulfur is avoided

22.
Sulfur causes iron to be red or hot short. The degree of hot shortness is in direct proportion to the amount of sulfur present.

23.
A piece of hot short iron will crack if worked with a hammer. When a piece of hot iron or steel cracks the exposed surface immediately oxidizes. This layer of oxide prevents the mending of the crack by welding.

24.
Large cracks cause the iron or steel to break up. Smaller cracks can cause the object to fail during use.

25.
Iron sulfide (pyrite, FeS2), is a common iron ore. It is also present in small quantities in many ores.


Sample Offer for Sale of Iron Ore

Iron Ore 63% Fe of Loei province, Thailand North Eastern origin for serious inquiries only. Detailed Product Description Iron ores are minerals from which metallic iron is extracted.
Most important use of iron is in the blast furnace for the production of pig iron. It is used in the furnace in the form of sinters and pellets as also lumpy ore. It is also consumed in the open health furnaces.

IRON ORE HANDLING
The design of the processing circuit is designed to feature a jaw crusher equipped with a rock-breaker followed by a two stage crushing and screening operation with horizontal washing screen to produce both lump and fines 0-50 mm size or as client's request. Capacity at 1,000 Mt per day and plan for 4,000 mt
Sufficient stockpiles of ore will be maintained at the processing facilities to allow for uninterrupted trucking/barging to Ayutthaya/Sriracha port.
Specifications;
Iron as Fe: 63 % min : Volumatic test method
Sulfur as S: 0.02%-0.08% max :
Phosphorus as P: 0.02%-0.05% max : Based on ASTM E278-01
Silica as SiO2: 2% to 3.5% max : Gravimatric test method
Aluminum as Al2O3: 0.98%-3.5% max : ICP test method
Specific gravity from 4.0 to 4.5.
Moisture content: Humidity at 105 deg.c on received basis 8%, Rainy season Max.10%.

More information: Iron Ores Chemical Analysis Sizes: Fine and Lump Fines are defined as iron ore with the majority of Individual particles measuring less
than 10 millimeters diameter. Conversely, lump is iron ore Majority of individual particles measuring more than 10 Millimeters diameter. Iron ore lumps varies from + 10 mm to + 75 mm.
More information: Iron ores size control
Fe Content: Iron of as high-grade as possible is required because an increased of 1% Fe in the burden increased the productivity by 2% and decreased the coke rate by 3%. In the THB Mining, the range of the Fe content in iron ore lumps is 60.52% to 66.5%.
Silica: 1.5% decreased of silica causes reduction in the slag volume of 65kg per ton of pig iron. Increase of 100-kg slag per tonne of pig iron raised fuel consumption by 40 kg of coke per tonne of pig iron. In the Thailand Plants, the range of silica in iron ore lumps varies from 1.6% (max.) to 3.5% (max.).
Alumina: If the ore is high in alumina, the fluidity of slag is affected. It should not also be too low. In the Indian Plants, alumina content in the ore varies from 3% to 3.5% Generally.
Phosphorus should not exceed 0.05%
DISTANCE ADVANTAGE:
The closest distance to China, Korea and Japan than other iron ore deposits, the transportation of the iron ore to China and Japan requires shorter time than other exporters. (Approximately 2,600 Nautical miles, India approximately 4,000 Nautical miles, Australia approximately 3,600 nautical miles, and Brazil approximately 10,000 nautical miles to China)
LOCATION OF anywhere PROVINCE, IRON ORES DEPOSITS
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Chemical Analysis / per our standards
Iron as Fe - Iron Oxide Fe2O3
As a commercial mineral Iron Ore often also contains small amounts of the following:

Silica as Si - Silicon Dioxide SiO2 :

Silica occurs commonly in nature as sandstone, silica sand or quartzite and ores.
Method of analysis: -Spectrophotometer*
Aluminum as Ag - Aluminum Oxide Al2O3 :
Aluminum oxide is an amphoteric oxide of aluminum with the chemical formula

Al2O3. It is also commonly referred to as alumina in the mining, ceramic and materials science communities. Method of analysis: -Titrimetry (fluorine method)
Titanium as Ti - Titanium Dioxide TiO2 :
Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally
occurring oxide of titanium, chemical formula TiO2. Method of analysis:
-Spectrophotometer*

Magnesium Mg - Magnesium Oxide MgO
Magnesium is a white solid mineral that occurs naturally as periclase and is a source
of magnesium. Method of analysis: -Spectrophotometer*

Manganese Mn - Manganese Oxide MnO Manganese is a chemical element that has the symbol Mn and atomic number 25. It is found as the free element in nature, often in combination with iron, and in many minerals. Method of analysis: Spectrophotometer*
Sulfur S - Sulfur dioxide SO2 (also sulphur dioxide)
Sulphur is the chemical compound with the formula SO2. This important gas is the main product from the combustion of sulfur. Method of analysis: Gravimetry*
Calcium as Ca - Calcium oxide CaO
Calcium commonly known as lime. Method of analysis: Spectrophotometer*
Loss On Ignition - LOI
Whilst it is desirable to have low contaminant levels of the elements mentioned above, it is considered the opposite for an LOI measure. Essentially, the LOI is a measure of the water content of the ore, which evaporates when the ore is fed into a blast furnace. A typical iron ore analysis should include an LOI determination at 1000 deg. C, normally undertaken by Thermo gravimetric Analyzer (TGA).
*Method accredited: international level for accreditation web site see http://www.cengeolab.com/argaCh_e.htm

1 comment:

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