Some physical and chemical properties of ferric oxide (a-Fe
2O
3, hematite) produced by spray roasting of HCl pickling liquor were examined in order to elucidate following subjects.
(1) The effect of FeCl
2 concentration in sprayed liquor and roasting temperature on mean particle size of fine hematite.
(2) Forming process of hematite granules (agglomerated particles), thermal decomposition process from FeCl
2 to iron oxide and dechlorination process of hematite.
The results are summarized as follows:
(1) The mean particle size of hematite is almost determined by FeCl
2 concentration and roasting temperature.
(2) The thermal decomposition of FeCl
2 is an exothermal reaction. When the roasting temperature is below the melting point of FeCl
2, the reaction product mainly consists of a-Fe
2O
3. At higher temperatures, the Fe
3O
4 content increases.
(3) The weight change of hematite by firing in air coincides with the sum of the decrement of H
2O and chlorides through desorption and decomposition and the increment of combined oxygen through oxidation of Fe (II) to Fe (III). The desorption of H
2O and HCl on hematite is completed at about 250°C. Other chlorides in hematite are recognized as FeCl
2 and FeCl
3.
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