Controlling the formation of Na2ZrSiO5 in alkali fusion process for zirconium oxychloride production

•We discussed the effect of roasting temperature on the formation of Na2ZrSiO5.•We discussed the effect of NaOH/zircon mole ratio on the formation of Na2ZrSiO5.•We discussed the effect of particle size of zircon sand on the formation of Na2ZrSiO5.•The mechanism was studied.•The amount of Na2ZrSiO5 significantly decreased under the optimum conditions.

In the alkali fusion process for the production of zirconium oxychloride, the formation of the water-insoluble by-product, Na2ZrSiO5, largely affects NaOH recovery and results in the formation of silicon slags. Thus, controlling Na2ZrSiO5 formation is necessary. In this paper, we studied the effects of roasting temperature, NaOH/zircon mole ratio, and particle size of zircon sand on Na2ZrSiO5 formation. The optimum reaction parameters, when the roasting time was 1 h, were as follows: ⩾95 μm average particle size of zircon sand, 6:1 NaOH/zircon mole ratio, and 750 °C roasting temperature. To avoid an uneven roasting temperature during alkali fusion, the use of a rotary kiln reactor is recommended. The amount of Na2ZrSiO5 was significantly decreased under these optimum conditions, and the content of Na2O was reduced from 7.049% to only 2.21% after three water-leaching cycles.

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