In the magnetite iron ore pelletization process, oxidation of magnetite followed by sintering of the oxidized magnetite (hematite) is desirable. Optimum preheating time & temperature and roasting time & temperature is required to get the desired properties of the pellets with magnetite, hematite, and hematite–magnetite blend. In order to utilize the magnetite resources in a current induration furnace, which is designed for hematite resources, detailed pelletization studies have been carried out to optimize the firing cycle for magnetite concentrate as well as magnetite with hematite concentrate. Under optimum conditions, such as preheating temperature 1000–1150 °C, preheating time 10 min, roasting temperature 1250 °C and roasting time 7.5 min, the cold compression strength (CCS) of magnetite roasted pellets was 325 kg/p, and this was due to recrystallization of secondary hematite particles, and development of the strong slag bond between primary and secondary hematite particles. The strength of hematite concentrate pellets was 260 kg/p. From laboratory studies, it was found that without disturbing the induration furnace firing cycle, which is designed for hematite ore ~5%, magnetite concentrate can be used along with hematite concentrate in pellet blend and the strength of the pellets was 270 kg/p. As the magnetite concentrate increases in the blend beyond 5%, the preheating zone residence time should be increased or a supply of extra oxygen is required. Laboratory as well as plant investigation has shown that the addition of magnetite to the hematite mix blend improved the strength of the pellets compared to hematite pellet alone.

中文翻译：

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磁铁矿精矿的硬化循环优化及其在赤铁矿精矿制球工艺中的应用

在磁铁矿铁矿石球团工艺中，需要先氧化磁铁矿，然后烧结氧化的磁铁矿（赤铁矿）。需要最佳预热时间和温度以及焙烧时间和温度，以获得所需的磁铁矿、赤铁矿和赤铁矿 - 磁铁矿混合物的球团特性。为了利用目前专为赤铁矿资源设计的烧结炉中的磁铁矿资源，已经进行了详细的球团研究，以优化磁铁矿精矿以及磁铁矿与赤铁矿精矿的烧成周期。在预热温度1000～1150℃、预热时间10min、焙烧温度1250℃、焙烧时间7.5min等最佳条件下，磁铁矿焙烧球团矿的冷压强度（CCS）为325kg/p，这是由于二次赤铁矿颗粒的重结晶，以及一次和二次赤铁矿颗粒之间强熔渣结合的发展。赤铁矿精矿球团的强度为 260 kg/p。从实验室研究中发现，在不干扰为赤铁矿设计的硬化炉烧成周期的情况下，磁铁精矿可以与赤铁矿精矿一起用于球团混合，球团强度为 270 kg/p。随着磁铁矿精矿在混合物中的增加超过 5%，预热区的停留时间应该增加或需要额外的氧气供应。实验室和工厂调查表明，与单独的赤铁矿球团相比，向赤铁矿混合混合物中添加磁铁矿提高了球团的强度。