Effect of Atmosphere on the Removal of Arsenic in Limonite
Limonite, prodnced in Hokkaido, contains arsenic.
As arsenic cannot be removed during the refining process in both blast furnaces and open hearth furnaces, it must be removed during the ore benefication process.
Therefore this investigation is conducted to find out the effect of atmosphere on the removal of arsenic in limonite during the ore roasting process, one of the ore benefication processes and the following results are obtained.
(1) Arsenic in limonite exists as Scorodite (FeAsO4·2H2O)
(2) The effects of atmosphere on the removal of arsenic in limonite during ore benefication Process are as follows:
(a) CO gas is very effective to the removal of arsenic and only about 5% of CO cohtent in the atmosphere accelerates the arsenic removal reaction.
(b) N2, a neutral gas, has no effect on the arsenic removal reaction.
(c) CO2 gas has a weak hindering action on the arsenic rewoval reaction.
(d) O2 gas has a strong hindering action on the arsenic removal reaction.
(3) Under the conditions of ore size of -100 mesh (As 1.91%, 5.12%), heating temperature 900°C, heating time of about 20mn and in the atmosphere of waste gas from incomplete combustion (CO 5%, CO2 15%, N2 80%), high arsenic removal ratio, about 97%, is obtained.
And under the conditions of sample ore size of 17mm, heating temperature of 900°C, heating time of about 1h and in the atmosphere of weak reduction, containing about 10% CO, 95% arsenic removal ratio is obtained.
(4) In the case of removal of arsenic in limonite by a weak reduction atmosphere, good arsenic removal ratio is obtained when it is reduced to the artificial magnetite.