Blast Furnace Iron production
History of industrial agglomeration of iron ore originates from the first commercially successful project "Gröndal» - production of briquettes from magnetite iron ore fines (1899, Finland). Briquettes were produced by the brickmaking press available at that time. They had the shape and size of the conventional bricks and were produced from wet iron ore without using any binder. Raw briquettes were subjected to strengthening firing in tunnel kiln with temperatures in the combustion zone up to 1400° c. Despite the unusual dimensions for blast furnaces, these briquettes have been successfully used in ironmaking plant in Pitkaranta. In the process of oxidative firing sulfur and iron content has decreased, in the briquettes it was 90% of the original iron content in the ore. Porous briquettes had high reducibility, and their use has led to a reduction of Coke rate and to the growth of the furnaces productivity. The success of the project contributed to its rapid spread, and in 1913 there were already 38 similar briquetting lines in operation (16 in Sweden, 12 in England, 6 in the United States).
At the beginning of the 20’s of the last century the briquetting technology – the only agglomeration technology available at that time - has been widely used for the agglomeration of the iron ore fines and waste. For example, briquettes share in the charge of BF plant “West” in the Calbe (Germany) reached 30–40%, and in the low-shaft BF plant Maxhütte (Germany) -100%. These briquettes were made from iron ore fines, coke and limestone dust. In the BF plant of the Kuvshinovskyi metallurgical plant (Russia) the share of the briquettes in the charge was as high as 25%. Briquettes in amounts up to 100 thousand tons per year were used in the BF of the Kerch and Taganrog metallurgical
plants (Russia). However, with the advent and development of high-productive iron ore and concentrates sintering method briquetting was not able to compete with this new technology due to the low capacity of the briquetting equipment.
At present time the agglomeration of the anthropogenic and natural iron containing substances by cold briquetting with the mineral or organic binders is obtaining increasing
application in BF production. Three basic briquetting technologies are being applied – roller-pressing, vibropressing and the stiff vacuum extrusion. Application of the stiff vacuum extrusion for the agglomeration of fine ores and disperse metallurgical wastes has been mastered in the early 21th century by the J. C. Steele&Sons, Inc. (USA). This modern technology comprises pushing of the homogeneous wet (moisture contents 12–16%) mix of the substances
under the pressure of 3.0–3.5 Mpa through the die holes under the vacuum in the working chamber of the extruder. In 2012 the term BREX (briquettes of extrusion) has been
introduced to distinguish these kinds of agglomerates from traditional briquettes. The capacity of the industrial stiff extruders of J. C. Steele ranges from 15 to 115 tons per hour. The self-cost for the production of one ton of the BREX varies from 2 to 10 USD depending on the extrusion line capacity.
The first application of the auger extrusion for agglomeration of ore and metallurgical wastes took place in the 90-ies of the 20th century when the industrial stiff extrusion briquetting line with the capacity of 20 tons per hour of the sludge and flue dust briquettes was commissioned at the Bethlehem Steel company (USA). These briquettes were melted in blast furnaces. The line was in operation till 1996 up to the cessation of main production
In April 2011 Suraj Products Ltd Company in Rourkela (India) began operating the industrial briquetting line for the production of BREX for blast furnace made of metallurgical wastes (sludge and flue dust) and iron ore fines by stiff extrusion technology. The capacity of this line is 20 t/h or an average of 6000 tons per month when two shift working schedule is used, which fully meets the needs of blast furnace process in briquetted charge. BREX on the cement binder with optimal and adjustable dimensions and managed chemical composition are considered as the charging material of new generation.
The first industrial experiment in application of BREX in BF as a major component of the charge successfully transformed into routine operation. More than 2.5 years BF worked on charge, consisting of BREX on 80% of the charge and for about a year this BF uses 100% BREX charge. The success of the project has been made possible, inter alia, as a result of a comprehensive study of metallurgical properties of BREX and improve modes of their use as a component of the charge, made by I.F.Kurunov and A.M.Bizhanov together with colleagues in India.