by Dimitris E. Tsakonitis (Refractory Business Unit Manager, GRECIAN MAGNESITE S.A Polygyros, GREECE)

Transcription

1 Presentation 20/06/2000 MAGNESIA FOR REFRACTORY APPLICATIONS by Dimitris E. Tsakonitis (Refractory Business Unit Manager, GRECIAN MAGNESITE S.A Polygyros, GREECE) 1. MAGNESIA Magnesia or Magnesium oxide (MgO), is the most important basic refractory raw material since its exhibits a very high melting point at approximately oc. Commercially, it is usually produced from the thermal decomposition of naturally occurring MgCO3 or Mg (OH)2 obtained from seawater or magnesium rich brines. Because it is ''basic'' in chemical character it is compatible (weakly reactive or non reactive) with basic slags. It is available in purities exceeding 98 % MgO in tonnage scale quantities. For these reasons it ranks of equal importance with alumina in refractories (i.e. both magnesia and alumina are the most important high purity oxides available for use in refractories). Caustic calcined MgO is produced at temperatures between oc and is characterized by high chemical reactivity, fine crystal size, high porosity and low bulk density. Caustic calcined MgO occasionally finds use in the metallurgical industry as slag conditioner but rarely employed in refractory products and never as a major aggregate ingredient. Dead burned MgO is produced at temperatures greater than oc and is characterized by low chemical reactivity, large crystal size, low porosity and high bulk density. Fused MgO is produced be melting caustic calcined MgO in an arc furnace at temperatures greater than oc. Table No 1 indicates the temperatures of calcining and the properties of the different types of Magnesia. Table No 1 Production Temperatures and properties of Magnesia Products Type Temperature C Surface Area m2/gr Caustic Calcined Crystalline Size microns Porosity % < 0,3 50 Dead Burned > < Fused > < 0,1 > 500 < 0,1 Source : Grecian Magnesite and Martin MariettaAs we mentioned above, Fused Magnesia produced in electric arc furnaces is in general a high performance product that was, until recently, disqualified from many refractory applications on cost grounds. The reason is that it is one of the most energy - demanding of refractory raw materials (see_table_no_2).

2 Table No 2 Energy consumption for the manufacture of typical refractory materials Raw Material Energy per tonne Sintered Alumina 10 GJ Seawater Magnesia (99 % MgO) 43 GJ Fused Alumina (98 % Al2O3) 36 GJ Fused Magnesia 97 GJ Source : Materials Technology Publications 2. SUPPLY Deposits of natural magnesite are widespread worldwide and reserves are very large. A number of deposits which are commercially exploited occur extensively in Southern, Central and East Europe, Turkey, Australia, Korea, Brasil and of course in China. There are about 60 producers of natural and synthetic sourced dead burned magnesia worldwide. Production of dbm outside China and Russia has been estimated at just over 3m tpa with the main producers being Australia, Austria, Brazil, Greece, Ireland, India, Israel, Italy, Japan, Netherlands, Mexico, Slovakia, Spain, Turkey, UK and the USA. Most of the Russian production (about tpa) is consumed inside the country. China produces some 1.8m. Table No 3 shows the major producers of dbm. Table No 3 World Leading Producers of Deadburned Magnesia Country/Company Type DBM Capacity Production/Sales Europe JSC Kombinat Magnezit N tpa (1999) SMZ Jelsava N tpa t Grecian Magnesite N tpa (DMB & CCM) tpa Magnesit AS N tpa est t Nedmag B tpa tpa Kutahya Magnesite Works Corp. N tpa NA Magnesitas Navarras SA N tpa (DMB & CCM) tpa DMB Premier Peridace Ltd S tpa est tpa Britmag S tpa est t (2000)

3 Sardamag S tpa NA RHI Group N NA tpa DBM Israel Dead Sea Periclace Ltd B tpa NA N. & S. America Magnesita SA B tpa t RHI America B tpa t Martin Marietta B tpa est t Quimica del Rey SA de CV B tpa t Asia China (various companies) N tpa (exported) Ube Material Industries S tpa t Australian Magnesium Company (Qmag) N tpa ( ) Source : Industrial Minerals MAGNESIA IN REFRACTORIES The refractory industry consumes almost all the amount of dbm which is produced world wide. The main reason is its strong resistance to molten basic slag. Therefore magnesia plays a key role as a raw material to manufacture refractories for iron and steel industry, cement industry and non - ferrous metal industry. Unfortunately the usage of magnesia in the refractory industry shows a continuous decrease over the last 22 years and a slight decrease is expected for the next 10 years. The refractory industry uses dbm, fused magnesia and some caustic calcined is a few applications. The two main categories for the application of dbm are the basic shaped refractories and the basic unshaped refractories. Table No 4 gives us an idea of the Magnesia based or basic Refractory shaped products. Table No 4 Energy consumption for the manufacture of typical refractory materials Product Magnesite bricks Composition - 80 % MgO Magnesite - chrome bricks 55 % > MgO % Chrome - magnesite bricks 25 % - MgO < 55 % Chromite bricks Cr2O3-25 % and MgO > 25 %

4 Magnesia - spinel bricks - 40 % MgO Spinel bricks 20 % > MgO % & 55 % < Al2O % Fired mag - carbon bricks Carbon - bonded magnesia bricks Carbon - bonded mag - carbon bricks Dolomite bricks < 2 % C < 7 % C - 7 % C 60 % CaO and 40 % MgO Mag - dolomite bricks 50 % > MgO % Source : Materials Technology Publications The main parameters that characterizes the refractory magnesia are the crystal size, the purity and the bulk density. Each of the above parameter is important according to the application. In the basic unshaped refractories we have products like gunning, dry fettling, dry ramming, tundish coating usually helping to make repairs in the steel and iron industry. 4. FUTURE, DEMAND AND OUTLOOK In the last four years there have been numerous consolidations in the refractory industry. They aimed at the reduction of the raw material cost and making a common effort in R & D to improve the quality and lifetime of the refractories. Nevertheless the consumption of refractory products has decrease. The reason is that refractory producers trying to compete one another have been making better products with the result that the specific consumption has decreased. According to a research made by Industrial Minerals in 2000, when steel industries replaced the open hearth furnaces, specific consumption which was 35 Kg/ton of steel in 1970 dropped to 23.5 Kg/ton of steel in 1980 in Germany. Today specific consumption of refractories in steel industry is about 10 Kg/ton of steel and is expected to drop even lower in the years to come. The universal demand of the refractory magnesia amounts to around 2m tones per year. Because of the competition with the Chinese fused magnesia the dbm will continue to have problems on a price/performance basis. Refractory companies have already began research to replace the qualities from high quality magnesia to dbm from natural magnesite. It is also true that the continuous study of the customers ' problem will lead to a better knowledge of the product to offer, so the blending of various qualities of dbm is inevitable. We believe that the demand for lower qualities will result in a growth of monolithics in the market which has already been using low qualities. The future of refractory magnesia is connected to the future of steel industry. The tendency towards the growing demand of steel appears in the developing countries. In the following years Asia will obtain 50 % of the global steel demand. We have already experienced the closing of steel plants in the USA and Europe and a shifting of steel production towards Asia. If we take into consideration the changes that take place in the steel production technology the consumption of refractories will be continuously dropping. Table No 5 shows steel production from 1985 to Table No 5

5 Source : IISI Some refractory companies believe that it is important for the production to be close to the customer in order to avoid the logistical disadvantage of long supply routes and a lot of them have done so. It is also true that long - term contracts between refractory producers and customers are to the interest of them both, because they have better logistics and production planning which lead to a lower production cost. Grecian Magnesite is a mining company established in We process and sell a wide range application - specific grades of raw magnesite, caustic calcined, dead burned magnesia and since 1999 basic unshaped refractories. Our annual sales in 2001 were tons of raw magnesite, tons of caustic calcined, tons of dead burned magnesia and approximately tons of basic unshaped refractories. We believe that a dead burned magnesia producer, having the advantage of the raw material,should not leave the opportunity to use it making refractories. Our wide range of dead burned magnesia qualities give us a variety of refractory products. So, since 1999, our company has started producing unshaped refractories which cover a wide range of applications like gunning, dry ramming, dry fettling, tundish spray mixes, tap hole filler materials etc. specially for Iron & Steel Industry. The sales course of refractories is displayed in table No 6. Table No 6

6 * estimation Source: Grecian Magnesite SA Struggling in a world of consolidations and merging, our company believes that its size allows us to be flexible and effective in a market with a lot of ups and downs. Finally, though we are still new in this field of refractories, we have made quite a few steady steps towards a better future and we have faith in it.