http://SaturnianCosmology.Org/ mirrored file For complete access to all the files of this collection see http://SaturnianCosmology.org/search.php ========================================================== Ironsands ...How is ironsand formed? ...How has the ironsand resource been developed? ...How is ironsand mined? ...How is ironsand turned into iron and steel? ...Where is the ironsand in New Zealand? ...Can ironsand be used for other products? ...How is a sandmine rehabilitated? ...How does a steel mill minimise its environmental effects? ...WORKSHEET [LINK] How is ironsand formed?...... In the North Island ironsand occurs along the west coast between Wanganui and Auckland. About one and a half million years ago (early Quaternary period) the volcano of Karioi, south of Raglan, erupted and other volcanoes became active between Raglan and the Waikato Heads. These eruptions continued until about a quarter of a million years ago (late Pleistocene) when volcanic activity started in Auckland and at Mount Taranaki (Egmont). Volcanic rocks were deposited both inland and along the coast. The erosion of this rock has provided the major raw material for the ironsand deposits. Measurement of the sediments carried by the Waikato River indicate that the major source of the Waikato North Head deposit is coastal erosion of the Taranaki volcanics rather than sand carried by the river from Ruapehu. Erosion of these volcanoes over several hundred thousand years, and the action of sea currents, waves and wind has concentrated the heavy minerals along the coast. These 'blacksands' were noted by Captain James Cook during his first voyage in 1769. He called the area 'The Desert Coast'. [LINK] How has the ironsand resource been developed?...... Many attempts have been made to work the ironsand deposits, the first in 1849. The main iron mineral in the sand is titanomagnetite, a compound of the elements titanium, iron, and oxygen (FeO) (Fe[2]O[3]) (TiO[2]). It was the presence of titanium which caused the usual iron making process to fail. The titanium oxide in the ore has a very high melting point and the slag blocks conventional blast furnaces. In addition the fine sand fell through the furnace and choked the hearth. Over the next 100 years at least six experiments to produce iron from ironsand were unsuccessful. In the late 1960s steel producers in Japan were looking for new suppliers of titanomagnetite. The same material which was known to block blast furnaces could now be used to preserve furnace linings and aid the steel making process. Extensive trials by the government using North Island ironsand, coal, and limestone led to New Zealand Steel being set up to develop an ironsand mining operation near the coast, north of the Waikato River and build a steel mill at Glenbrook, south of Auckland. Steel production started in 1970 with the Glenbrook mill pioneering the direct reduction of ironsand and coal to make iron and steel. The Glenbrook process is unique. No other steelmaking operation in the world makes steel in the same way. [LINK] How is ironsand mined?...... First the sand has to be mined. Bucketwheel excavators place the sand on shiftable conveyors. The conveyors discharge onto a main trunk conveyor which feeds a stockpile from which the sand is fed into the concentration plant. In the plant the titanomagnetite is separated from the other sand and unwanted materials. Titanomagnetite is magnetic and heavier than other minerals in the sand, so magnetic and gravity methods are used to separate it from other minerals. Mined sand firstly passes through revolving screens called trommels to remove stones and other impurities. Oversize material like stones, roots, and lumps of clay are sized out and discarded. Water is added to the sand to produce a slurry. Magnetic separators remove the titanomagnetite which accounts for about 20% of the sand, but some low grade sand is also trapped. This is removed by gravity in cone concentrators and spiral separators. Sand and water flow over the surface of the cone and the heavier iron minerals sink to the bottom and pass through the slots in the cone. A series of cones and spiral separators remove nearly all the light minerals. The final stage uses finely adjusted magnetic separators . Water is added to the ironsand concentrate so that it can be pumped through pipelines. The nonmagnetic sands which are not required are returned to the mining area. To view a photographic flow chart of the ironsand mining at North Head click here. [LINK] How is ironsand turned into iron and steel?...... Up to 1.2 million tonnes of concentrate is used each year, along with 800,000 tonnes of Waikato sub-bituminous B and C grade coal from Huntly and 1100 GWh of electricity. This is about the same amount of electricity used by Wellington City. Iron is produced from the ironsand concentrate using coal as a source of energy and as a chemical reagent which reduces the iron oxide in the ironsand to iron. Limestone sourced from Otorohanga is used as a purifying agent. When operating to capacity the steel mill uses 80,000 tonnes a year. The gas produced from the coal is used to generate some of the electricity used in the mill. Up to 1 million tonnes of water circulates through the steelmaking and finishing plants. About 20,000 tonnes of fresh water is added daily. Extensive recycling and the use of site stormwater assists in water conservation. Water is cleaned, cooled, and recirculated many times in each process. Ironsand together with Huntly coal is preheated in a furnace to 600ºC. This converts the coal to a charcoal. The mixture is then fed into a kiln with carbon dioxide. The carbon dioxide reacts with the charcoal to form carbon monoxide (2C+02=2CO). The carbon monoxide reduces the iron oxide releasing carbon dioxide in the process (FeO+CO=Fe+CO[2]). The kiln product is then fed through an electric melting furnace where the charcoal reduces the remaining iron oxide to pig iron with a carbon level of about 4%. The pig iron is fed into an oxygen steelmaking furnace where the carbon content is lowered again and it is refined as steel. Various alloying compounds are added to the molten steel, depending what the steel will be used for. The properties of steel depend on the proportion of alloying elements and the heat treatment of the metal. Glenbrook produces galvanised steel, colour coated steel for roofing and building, as well as sheet steel, pipes, structural steel, and many other products which are used in New Zealand and exported. [LINK] Where is the ironsand in New Zealand?...... As well as the ironsand mining operation at North Head, two similar ironsand mining operations were developed on the west coast of the North Island at Waipipi near Wanganui in 1971 and further north at Taharoa in 1972. Gravity and magnetic separation are used to produce concentrate which was pumped through pipelines to an offshore buoy for loading into specially designed ships. The Waipipi plant closed in 1987 having produced about 15.7 million tonnes of concentrate. The Taharoa operation continues to produce titanomagnetite concentrate for export, with about half of New Zealand's total ironsand concentrate output currently being exported. The ironsand resources of the North Island are very large. Detailed investigations of only parts of the coast have given resource estimates of 1444 million tonnes of titanomagnetite and 8.4 million tonnes of ilmenite. These resources would keep the existing scale of operation going for several hundred years. Barrytown and Westport in the South Island have significant ironsand resources. These sands are rich in ilmenite, the same as that found in schist from the Southern Alps. The ironsands of the South Island had been formed, weathered, transported, and concentrated in the same way as those in the north, but their makeup is significantly different. COASTAL IRONSAND RESOURCES IN NEW ZEALAND (millions of tonnes) TITANOMAGNETITE Taharoa 595 Waikato Heads 570 Other North Island deposits 279 TOTAL 1444 ILMENITE 8.4 Auckland 8.4 Westport 16.5 Barrytown 12 Other West Coast deposits 6.9 TOTAL 43.8 [LINK] Can ironsand be used for other products?...... The South Island reserves could produce titanium dioxide (TiO[2]), a white pigment used in the production of paint, paper and plastic. Titanium dioxide is non toxic and lasts longer than potentially poisonous lead which has been used in the past as a white pigment. The metal titanium is used extensively in aircraft, ships, and marine fittings. It is also used in golf club shafts and cycle components. Its light weight coupled with its strength make it ideal for a variety of high tech applications. [LINK] How is a sandmine rehabilitated?...... The sand left over after the ironsand has been removed is returned to the mining area. It is planted with marram grass and radiata pine trees to stabilise the area and return it as close as possible to its previous condition. As with all modern mining operations, rehabilitation is an integral and important part of the total operation. [LINK] How does a steel mill minimise its environmental effects?...... Large amounts of solid, liquid, and gaseous wastes are generated during the steel making process. In New Zealand the Resource Management Act places requirements on companies to manage the effects their operations have on the physical and natural environment. New Zealand Steel has a commitment to the environment in which it operates. The company has developed and implemented a formal Environmental Management System. This provides a formal structured process to monitor and improve environmental performance New Zealand Steel has resource consents for: * discharges to air * extracting fresh water * discharging treated wastewater and stormwater into water * discharging water containing wastes onto land * operation of a landfill for non-hazardous wastes In addition the mill recycles, reuses, and sells many byproducts of the steelmaking process. Air There are three main types of air emissions associated with the Glenbrook steelmaking operation: * dust which arises from stockpiles, material handling, vehicle movements on unsealed roads and the like * dust, steam and hot gasses which are discharged from a vent or stack * odour arising from chemicals and the emergency release of process gas There are two main methods of cleaning emissions to air: * Wet scrubbers which wash dust out of process gases are used to control air pollution. More than three million cubic metres of waste gas are cleaned each hour the steel mill is working at full capacity. * A dry bag system which works just like a gigantic vacuum cleaner. The largest baghouse can clean a million cubic metres of dust -laden air each hour. Between five and ten tonnes of dust per hour can be removed from discharges to air by this method. wet scrubber Water Water is used during the ironsand extraction process, to transport the ironsand as a slurry to the steelmill, and in the steelmaking process. Water is extracted from the river at a point about 14 kilometres from the mouth of the Waikato River. About 20,000 tonnes of water is extracted each day. This represents around 0.06% of the average total flow. The water intake is designed to avoid the uptake of fish. Water is recycled to reduce both the required water intake and the amount of waste water. To achieve maximum water conservation water is cleaned, cooled, and recirculated many times in each process.All waste water and storm water is treated to the high standard required by the Auckland Regional Council and the resource consents prior to discharge into the Waiuku Estuary. Landfill About 140,000 tonnes of waste is deposited in the steelmill's landfill each year. At this rate the site will provide for 20 years of operation. The landfill has been carefully constructed and designed for unwanted non-hazardous materials. A compacted clay liner and a series of drains capture any landfill leachate and direct it through treatment ponds. As each area is filled it is covered with compacted clay then topsoil. The area is sown with grass seed and then used to graze livestock. schematic profile Recycle & Reuse The steelmill produces about 700,000 tonnes of solid and liquid waste each year. 550,000 tonnes of this is recycled, reused, or sold. Many products have been developed from slag which is a by-product of steelmaking. Coarse slags are used for drainage, roading, and wetlands. High free-lime slags are blended as a soil conditioner and used for road stabilization. By-products which cannot be reused or recycled are disposed of in the landfill . You can find more information on ironsand in the five Mineral Resources Series booklets produced by the New Zealand Minerals Industry Association. Click here to access further information. home/top