Sinters were produced in the pilot plant using four different ore mixtures with varying proportions of iron ores, fluxes and coke. All the resulting sinters were characterised by chemical and granulometric analysis, degradation testing during reduction in the blast furnace (RDI test), cold resistance testing (Tumbler test), reducibility testing, determination of softening and melting temperatures, and determination of the sinter structure by electron microscopy. The obtained result allow for the establishment of better operation conditions to manufacture sinters.KEY WORDS: sintering; quality of sinter; ore mixtures; iron ores; blast furnace. 1089© 2010 ISIJ line with the ores present, but is three percentage points lower in mixtures 3 and 4 due to the inclusion of 'Goa Silicioso' ore with its lower total iron content. The ferrous content between 3.1 and 4.8 % can be considered as low as correspond to the hematitic nature of the iron ores that make up part of the mixtures. The alkalis content is low. Granulometric AnalysisGranulometric analysis has been performed using a ROT-TAP unit, which combines reciprocating eccentric rotary screening with a percussion system on the screen column. Figure 1 displays the granulometric curve for ore mixture 1, with an average particle size of 1.69 mm. Table 5 lists these values for the four different mixes. Granulation FitnessThe ore mixtures are subjected to granulation treatment prior to sintering in order to increase the average size of the very fine grained ores, with the aim of improving their dynamic behaviour during sintering.The granulation treatment is of basic importance in iron ore sintering, because good sinter bed permeability to a large extent determines the sintering rate and thus the plant's productivity.Granulation fitness testing of each iron ore and each ore mixture has been carried out following the SAFE (Size Analysis on Frozen Elements) standard procedure established by Centro Sviluppo Materiali (CSM) of Italy. Figure 2 shows the granulometry curve of ore mixture 1 before and after the SAFE test. Table 5 indicates the average particle size of the ore mix- ISIJ International, Vol. 50 (2010), No. 8 4) 1090© 2010 ISIJ Table 1. Chemical analysis of iron ores (wt%). Table 2. Chemical analysis of fluxes (wt%). Table 3. Composition of ore mixtures (wt%). Table 4. Chemical analysis of ore mixtures (wt%). tures after undergoing the SAFE test. All the mixtures present good granulation fitness. ReducibilityA reducibility test has been performed at 900°C following the ISO standard for sinters, adapted for ore mixtures of the 3.3-2.0 mm fraction.5) The results are displayed in Table 5. The R 60 value ranges between 50-56 % and may be considered good. Softening and Melting TemperaturesThe test to determine softening and melting temperatures of the ore mixtures has been carried out using a LECO AF-600 unit, with an oven that reaches a maximum temperature of 1 650°C, in which the following parameters have been fixed with the help of a computer: ASTM standard with inert ...

The sintering process involves a large number of parameters, more than 500, each of which exerts a greater or lesser influence and needs to be controlled, within the possible limits, in order to optimise productivity, process stability, and standardise the composition and quality of the sinter produced. To comply with environmental legislation, a pollution control system must monitor the particle matter and gases generated and emitted into the atmosphere by the sinter plant. Automation and control systems are vital tools to assist plant operators in the monitoring of each stage of the sinter production process.

Replacement of metallurgical coke by pulverized coal (PC) injected in blast furnace (BF) tuyeres is a major economical challenge, due to the high price of coke and unfavorable effect of its production for the environment. But the difficulty consists in necessity of complete gasification of coal particles within raceway and compensating for the negative changes in technology. Theoretical Increase of flame temperature due to increment of oxygen concentration was compensatedby increasing natural gas (NG) and PC consumptions.Productivity in account to equal conditions with rela-36 (1996), No. 10

Iron ores, fluxes and tuyere injected coals used as burden materials in the blast furnace have been characterised by chemical and granulometric analysis, moisture, density and porosity, softening and melting temperatures, reductibility, X-ray diffraction, electronic microscopy and thermoanalysis. Theoretical calculations on the influence of both the chemical composition and ash content of coals on some aspects of the blast furnace operation have been carried out. The combustion behaviour of pulverised coals in a pilot plant equipped with a combustion chamber has been studied to indicate what the behaviour of each type of coal will be, when injected in blast furnace tuyeres.

A range of iron ores were used in varying proportions to prepare 28 different ore mixtures. Each mixture was classified according to its granulation index and sintered in a pilot plant. The resulting sinters were characterised by chemical analysis, degradation during reduction in the blast furnace (reduction degradation index test), cold strength (tumbler test), coke consumption and process productivity. Sinter quality was assessed in relation to the granulation index of the ore mixture.