Difference between revisions of "Iron ore (fines)"
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Revision as of 10:33, 1 May 2020
|Infobox on Iron ore (fines)|
|Example of Iron ore (fines)|
|Origin||Russia, Brazil, China, Australia, India and the U.S.A.|
|Stowage factor (in m3/t)||Varying largely; several iron ore products are classified as heavy bulk cargo, which means that due to their dense structure overstressing of tank tops or ship's structures can occur in case improperly loaded and or distributed over a ships hold.|
|Humidity / moisture||Various|
|Ventilation||Usually not required|
|Risk factors||Liquefaction. Overstressing of ship's structures due to the density of certain iron ore products|
Iron ore (fines)
Iron Ore (fines)
Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in colour from dark grey, bright yellow, deep purple, to rusty red. The iron itself is usually found in the form of magnetite (Fe3O4), hematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH).n(H2O)) or siderite (FeCO3).
Ores carrying very high quantities of hematite or magnetite (greater than ~60% iron) are known as "natural ore" or "direct shipping ore", meaning they can be fed directly into iron-making blast furnaces. Most reserves of such ore have now been depleted. Iron ore is the raw material used to make Pig Iron, which is one of the main raw materials to make steel. 98% of the mined iron ore is used to make steel. Indeed, it has been argued that iron ore is "more integral to the global economy than any other commodity, except perhaps oil".
Iron ore is mined in about 50 countries. The seven largest of these producing countries account for about three-quarters of total world production. Australia and Brazil together dominate the world's iron ore exports, each having about one-third of total exports.
Iron (Fe) is a metallic element and composes about 5% of the Earth's crust. When pure it is a dark, silvery-gray metal. It is a very reactive element and oxidizes (rusts) very easily. The reds, oranges and yellows seen in some soils and on rocks are probably iron oxides. The inner core of the Earth is believed to be a solid iron-nickel alloy. Iron-nickel meteorites are believed to represent the earliest material formed at the beginning of the universe. Studies show that there is considerable iron in the stars and terrestrial planets: Mars, the "Red Planet," is red due to the iron oxides in its crust.
Iron is one of the three naturally magnetic elements; the others are cobalt and nickel. Iron is the most magnetic of the three. The mineral magnetite (Fe3O4) is a naturally occurring metallic mineral that is occasionally found in sufficient quantities to be an ore of iron.
The principle ores of iron are Hematite, (70% iron) and Magnetite, (72% iron). Taconite is a low-grade iron ore, containing up to 30% Magnetite and Hematite.
Hematite is Iron Oxide (Fe2O3). The amount of hematite needed in any deposit to make it profitable to mine must be in the tens of millions of tons. Hematite deposits are mostly sedimentary in origin, such as the banded iron formations (BIFs). BIFs consist of alternating layers of chert (a variety of the mineral quartz), hematite and magnetite. They are found throughout the world and are the most important iron ore in the world today. Their formation is not fully understood, though it is known that they formed by the chemical precipitation of iron from shallow seas about 1.8-1.6 billion years ago, during the Proterozoic Eon.
Taconite is a silica-rich iron ore that is considered to be a low-grade deposit. However, the iron-rich components of such deposits can be processed to produce a concentrate that is about 65% iron, which means that some of the most important iron ore deposits around the world were derived from taconite. Taconite is mined in the United States, Canada, and China.
Iron is essential to animal life and necessary for the health of plants. The human body is 0.006% iron, the majority of which is in the blood. Blood cells rich in iron carry oxygen from the lungs to all parts of the body. Lack of iron also lowers a person's resistance to infection.
It is estimated that worldwide there are 800 billion tons of iron ore resources, containing more than 230 billion tons of iron. It is estimated that the United States has 110 billion tons of iron ore representing 27 billion tons of iron. Among the largest iron ore producing nations are Russia, Brazil, China, Australia, India and the USA. In the United States, great deposits are found in the Lake Superior region. Worldwide, 50 countries produce iron ore, but 96% of this ore is produced by only 15 of those countries.
Iron ore is the raw material used to make Pig Iron, which is one of the main raw materials to make steel. Due to the lower cost of foreign-made steel and steel products, the steel industry in the United States has had difficult economic times in recent years as more and more steel is imported. Canada provides about half of the U.S. imports, Brazil about 30%, and lesser amounts from Venezuela and Australia. 99% of steel exported from the USA was sent to Canada.
Almost all of the iron ore that is mined is used for making steel. Raw iron by itself is not as strong and hard as needed for construction and other purposes. So, the raw iron is alloyed with a variety of elements (such as tungsten, manganese, nickel, vanadium, chromium) to strengthen and harden it, making useful steel for construction, automobiles, and other forms of transportation such as trucks, trains and train tracks.
While the other uses for iron ore and iron are only a very small amount of the consumption, they provide excellent examples of the ingenuity and the multitude of uses that man can create from our natural resources.
Powdered iron: used in metallurgy products, magnets, high-frequency cores, auto parts, catalyst. Radioactive iron (iron 59): in medicine, tracer element in biochemical and metallurgical research. Iron blue: in paints, printing inks, plastics, cosmetics (eye shadow), artist colours, laundry blue, paper dyeing, fertilizer ingredient, baked enamel finishes for autos and appliances, industrial finishes. Black Iron Oxide: as pigment, in polishing compounds, metallurgy, medicine, magnetic inks, in ferrites for electronics industry.
Though there is no substitute for iron, iron ores are not the only materials from which iron and steel products are made. Very little scrap iron is recycled, but large quantities of scrap steel are recycled. Steel's overall recycling rate of more than 67% is far higher than that of any other recycled material, capturing more than 1-1/4 times as much tonnage as all other materials combined.
Some steel is produced from the recycling of scrap iron, though the total amount is considered to be insignificant now. If the economy of steel production and consumption changes, it may become more cost-effective to recycle iron than to produce new from raw ore.
Iron and steel face continual competition with lighter materials in the motor vehicle industry; from aluminium, concrete, and wood in construction uses; and from aluminium, glass, paper, and plastics for containers.
Spathic ore is used for the production of hydrogen by steam iron contact process. The ore to be used must have a spongy structure in order to present the maximum surface contact. Generally ore of light yellow colour is preferred. It should not sinter together when subjected to the high temperature of 1.000ºC.
The ore is calcined before use to make it suitable for reduction and oxidation cycles. For the production of hydrogen, the calcined ore is first reduced at 700-1.000ºC by use of water gas or producer gas. Steam is then passed over it. The ore gets oxidised and the hydrogen is liberated from the steam. The oxidised ore is then subjected to the reduction cycle by passing water gas which makes the ore suitable for reuse.
The arrangement for the process of oxidation and reduction cycle is made automatic in the plant to get the supply of commercial hydrogen which is utilised for the hydrogenation of vegetable oils. Hydrogenation effects hardening of the oils.
Micaceous iron ore is generally soft and unctuous. It is used in the manufacture of welding rods (electrodes). It is also used as a coating material in the preparation of welding rods. Bog iron ore is used as purifying and desulphurising material of producer gas and municipal gases. The ore is filled in purifying tank through which gases are passed and purified. Magnetite is used for the preparation of heavy media in coal-washing plants. It has got distinct advantage over sand as magnetite particles adhering to coal can easily be separated by the magnetic separator.
Shipment / Storage / Risk factors
Iron Ore (fines) (Liquefaction)
‘Fines’ is a general term used to indicate the physical form of a mineral or similar cargo and, as the name suggests, such cargoes include a large proportion of small particles. The transportation of iron ore fines by sea from the Indian subcontinent has proved problematic in recent years when the moisture content has been too high at the time of loading. As a consequence the solid cargo has behaved as a liquid, sometimes with alarming results. This phenomenon is called liquefaction and leads to stability problems whereby the cargo can shift at sea under the influences of the motion of the vessel and the effects of vibration. Shifting can be sudden or progressive and lead to a ship developing a severe list, sometimes resulting in a capsize.
Cargoes from the Indian sub-continent have been particularly prone to this phenomenon in the monsoon season (June to September) because the fines are stored outside very often with no protection from heavy rain. Also, cargoes transported long distances by rail from mines to ports are prone to similar exposures. However, as explained below, such problematic cargoes would never have been loaded if properly sampled, tested and assessed before loading commenced. It is worth noting also that stockpiles can remain moist if left out in the open after the monsoon season. As such, care needs to be taken at all times and close attention paid to pre-loading test procedures. Liquefaction car occur in a cargo that outwardly appears dry on the surface or essentially so; it does not have to be ‘running wet’ with water for it to have the propensity to liquefy.
In a dry, granular, well-trimmed cargo the individual particles are in contact with each other such that frictional forces prevent them sliding over one another. However, if there is enough moisture present then there is the potential for the cargo to behave like a liquid. This is because settling of the cargo occurs under the influences of vibration, overstowage and the motion of the ship. As such, the spaces between the particles reduce in size with an accompanying increase in water pressure between the particles. This results in a reduction in friction between the particles and can allow the cargo to shift suddenly.
Testing the Fines
Obviously, before a cargo is loaded the owners and charterers need to be satisfied that it is safe to carry. The International Maritime Solid Bulk Cargoes Code, published by the IMO, addresses this by requiring that the shippers ensure it is properly sampled, tested and assessed before it is loaded. Cargoes that are capable of liquefaction are classified Class A cargoes. The Code is mandatory under the provision of the SOLAS Convention.
The Code requires that the cargo be assessed by determining a property known as the flow moisture point (FMP). This is the lowest moisture content at which the material under test begins to exhibit flow (liquefaction). The Code requires that whatever the value of the FMP, it is reduced by 10% so as to incorporate a safety factor. This lower figure is then adopted as the Transportable Moisture Limit (TML) for the cargo; TML – 90% of FMP.
As such, tests to determine the actual moisture content of the cargo must then be carried out on a representative sample before it is loaded. If the moisture content is at the TML or exceeds it then the cargo should be declared unsafe and rejected. It is important to note that the moisture content determination on the cargo to be loaded must be carried out no more than seven days before the loading commenced. Moreover, if there has been significant rain between the time of testing and loading then further tests must be conducted to ensure that the moisture content of the cargo is still less than the TML. The IMSBC Code sets out the proper Laboratory Test Procedures, Associated Apparatus and Standards. The test should be carried out by a competent laboratory.
The IMSBC Code requires that the shipper shall provide certification to the Master to confirm the TML and actual moisture content of the cargo before loading can commence. Only if the cargo has a moisture content that is less than the TML can it be offered for safe carriage by sea. Masters should be vigilant and ensure that cargo is inspected for any signs that it may be above the TML. For example, free standing surface water, or spattering of cargo as it lands in the holds with resulting run marks are clear warning signs.
The IMSBC Code states that a Master may undertake his own check test, often referred to as the ‘can test’. If he considers that the cargo may not be as dry as is being claimed then he can adopt a complementary test procedure.
The test is to check for approximately determining the possibility of flow on board ship or at the dockside by the following auxiliary method: Half fill a cylindrical can or similar container (0,5 to 1,0 litre capacity) with a sample of the material. Take the can in one hand and bring it down sharply to strike a hard surface such as a solid table from a height of about 0,2 m. Repeat the procedure 25 times at one-or-two-second intervals. Examine the surface for free moisture or fluid conditions. If free moisture or a fluid condition appears, arrangements should be made to have additional laboratory tests conducted on the material before it is accepted for loading. “It is worthy of note that if the result of the ‘can test’ is negative this is not proof that the cargo is below the TML.
Summary Advice for Masters)
Follows the IMSBC Code requirements in relation to Class A cargoes.
- Ensure that certification showing the moisture contents of the cargo and the TML are presented before loading commences.
- The cargo shall only be accepted if the moisture content is below the TML.
- Confirm that the certification is from a reputable laboratory and that the moisture content determination was carried within a week of the start of loading. If it has rained in that intervening period then further laboratory tests should be carried out to establish the moisture content of the fines to ensure that it is still below the TML.
- Be vigilant during loading and watch out for any signs of wetness in the cargo. If unsure of the state of the cargo undertake a ‘can test’ which may assist in determining whether the cargo is at or above the TML. If any doubts remain then the Master should seek advice from the responsible person ashore.
- Once a cargo is on board it will be difficult to discharge at the load port as it will almost certainly be regarded as having been exported from India.
See also Ores (and Ores unprocessed)