sponge iron industry –past-present-future - SIMA

More documents

Recommendations

Info

SPONGE IRON INDUSTRY –PAST-PRESENT-FUTURE S.C. KHATTOI, Managing Director PROJECT AND ENGINEERING CONSULTANCY, ODISHA Way back in 1980 sponge iron industry entered in to Indian market as an alternate route of steel making. India having good quality iron ore and non coking coal, the Sponge Iron process got stabilised with time. The standard size of coal base plant used to be 300 to 350 tons per day and 0.1mt per year. The plant cost used to be high due to some imported components used in the kiln & cooler. Gas base DRI plants using shaft kilns came closer to gas source in the west coast. The production capacity of single gas base units used to be two million tons per year & investment used to be very high. Hence limited number of gas based shaft kiln came in to existence. The main focus came to coal based sponge iron plants. Designers increased the capacity from 300tpd to 500tpd for each kiln by increasing the equipments size but the project cost still remained high. Lurgi’s pilot plant of 100tpd at Andhra Pradesh, which was set for testing Indian raw material, produced 30,000tons per annum. This small size became a viable model without having pollution control equipment in the off gas system. Some old cement kilns were modified to sponge iron units at a much lower cost. Then started mushrooming of Sponge Industries all over India. It is either nearer to iron ore source or coal source. The pollution level remained very high and was viewed leniently by government officials considering the new technology and industrial growth of the country. The higher capacity plants had ESP or Quencher scrubber as pollution control measure for their waste gas from the installation stage. Smaller plants even though installed the Pollution control equipments much latter like ESP and bag filters, still sponge iron units are considered as highly polluting industries to-day. Rotary kiln method became predominated in coal based sponge iron units. There are only few rotary kilns which have the capability to use coal, oil and gas individually or in combination. One major technological development was introduced by the author in the early days is to feed coal from discharge end by means of lean phase pneumatic conveying. The fresh carbon from discharge end coal helped to stabilize the process. It increased the kiln capacity by reducing coal quantity from the feed end which made space for iron ore. Presently this coal injection is a part of the whole system. Use of iron ore fines from 2mm to 6mm was also injected from discharge end. The maximum capacity went up to 2 tons per hour through dense phase conveying and it was discontinued after one year due to vigilant process control requirements. The raw material like iron ore, coal, limestone, dolomite used to tumble inside the kiln from 6.0Hours to 10.0Hours at 1050º C. The size of the raw material and its mean particle size became a major factor as smaller kilns have a retention time of 6.0 Hours. Different size kilns optimised their raw material sizes depending upon the residence time inside the kiln. As the raw material and product both used to tumble inside the kiln and cooler, a lot of fines are generated. To reduce the fines generation, the selection of raw material became stringent. Ore was selected on the basis of its higher tumbling index, meaning hard and massive ore. The minimum Fe content was fixed as 65% and tested for its reducibility character. Magnetite ore was rejected due to its structure as Fe3O4 and required a higher temperature for reduction. Considering all the required properties, specific iron ores are declared as sponge grade and restricted its use in the blast furnace. Similarly selection of coal was done mainly on ash fusion temperature and fixed carbon; the other properties considered are its reactivity, volatile matter & sulphur content. Good steam coal of B & C grade was declared as metallurgical coal for sponge iron making. Government was requested to preserve similar coal for metallurgical use rather than using it in boilers of power plants and railway steam engines. At the beginning the iron ore size used to be +6mm to -40mm. Due to process optimisation the size reduced to 25mm from 40mm in few years time and remained for some period. Then the size changed to 22mm and afterwards to 20mm and continued with JANUARY-2011/10
it. Smaller kiln preferred the size to be maximum 16mm where as bigger kiln at 20mm. since the upper limit drastically reduced, the fines(-6mm) generation in crushing went up to 40% while producing calibrated ore ( +6 to -16mm). To increase the usability of ore, the lower cut off line changed to +5mm instead of +6mm. Hence the main calibrated ore produced by the crushing unit became +5mm to – 16mm OR +5mm to -20mm depending up on the requirement and the fines generation came down to 35%. Different crushing methods were adopted and cone crushers were used to further bring down the fines (-5mm) generation below 35%. Even with all those high set parameters, iron ore cost still remained much lower in comparison to coal cost. It used to be a buyers market for iron ore. High grade steam coal was available at the beginning of the sponge iron industries but with increasing number of units, there were shortage of high coal. Getting linkage from Coal India became difficult. Necessity being the mother of invention, trial started with E & F grade coal. The process became successful, at the cost of product quantity. A 100tpd plant produced 80tpd and a campaign life of 60 to 90days. The cost of E & F grade coal being low and availability is high; it opened a new scenario for industries survival. Coal Washery became a necessity to improve the coal quality from E & F grade. Some units installed hydraulic Batac Jigs to up grade the coal by gravity separation. Many merchant coal washeries came into existence for up grading the E & F grade coal for sponge iron kilns. The washery used- heavy media separation, Hydro cyclone, Hydro zigging, pneumatic zigging, x-ray and gamma ray shorting methods. The main recovery used to be low, the middling went to power plants and the rejects for land filling. The cost of washed coal in a washery became high without rejects being used in the power plant. All the options remained with the user including the availability of imported coal to make it cost effective. At the beginning in 1984 the profit margin in sponge industry was very low as scrap is the major raw material for arc and induction furnaces. The use of sponge iron in the furnaces increased slowly, the price picked up so is the profit margin. The sales price of sponge iron got linked to scarp and it varied depending upon scrap market. The average profit margin remained for some time until mines owners started their own sponge iron industry. The profitability from mines to sponge became clear to them. They decided to transfer the profit from sponge industry to iron ore mines. Then the cost of iron ore started shooting up. It exceeded much more than coal cost and merchant sponge manufacturers had difficulties in keeping the plant running. Then started the forward and backward integration of individual units for their survival but this industry never remained lucrative any more. Power plant from the waste heat became a silver lining for all sponge industries. Sale of power to grid or use in own steel melting unit kept the plants rolling. Power sale through national grid was more beneficial than selling to local distributors which have a low tariff rate. In the recent past years steel market shoot up very high so is the sponge iron rate. But mines owner linked the ore price to sponge price which again affected the profitability of the unit. The main profit went to the mines owner. If the cost of making the calibrated ore from mines is within Rs 2000/-per ton, the sales price went up to Rs 5000/-per ton. The financial stability of each mine owner became very high and ore being a non perishable item they dictated the terms. The buyers market changed to a sellers market. Government having no control over the sales price, again the merchant sponge iron unit became sick. To over-come the situation, low grade iron ore having 62 to 63% Fe content which was once a rejected material became the main raw material. Some plants started using soft ore of +10mm to - 40mm considering the ore will break in tumbling inside the kiln to smaller sizes and reduce to Fe metallic. As the price of this ore being low, it gave some profit margin at the cost of sacrificing the campaign life. This process continued for some time until the same practice adopted by many plants and the mines owner increased the ore price. To day all the Sponge Iron plants are becoming sick as iron ore price are high. Coal prices have also gone up due to Coal India policy. Availability of good coal and iron ore is scarce and prices are very high. The sales price of sponge iron is low. Iron ore fines cost JANUARY-2011/11
Page 2 and 3: CHAIRMAN V S BAPNA VICE CHAIRMAN B
Page 4 and 5: UPGRADING QUALITY OF INPUTS TO AUGM
Page 6 and 7: There is acute shortage of high gra
Page 8 and 9: SUCCESSFUL STARTUP AND OPERATION OF
Page 10 and 11: GSPI Micro-Module Control Room Gulf
Page 14 and 15: JANUARY-2011/12
Page 16 and 17: From a meager production of 1.31 mi
Page 18 and 19: tubes. The newly reformed gas, cont
Page 20 and 21: Process Advantage l Proven performa
Page 22 and 23: Annexure I Map of Natural Gas pipel
Page 24 and 25: SIMA DELEGATE TO CHIN JANUARY-2011/
Page 30 and 31: CONTRIBUTION OF SECONDARY STEEL SEC
Page 32 and 33: in total crude steel production wou
Page 34 and 35: New product developments Sabyasachi
Page 36 and 37: advantages over the conventional he
Page 38 and 39: Description “Graspan Tri Flo ® P
Page 42 and 43: Moreover, some analyst suggest that
Page 44 and 45: BRIEF REPORT ON ONE DAY SEMINAR ON
Page 46: JANUARY-2011/44

sponge iron industry –past-present-future - SIMA

Create successful ePaper yourself

Delete template?

Save as template?