842
H. B. Wang et al.
increases greatly. When the amount of calcium chloride increased from 12 to 28%,
the volatilization rate of zinc, copper, and indium increased from 26.33% to 99.43%,
from 15.38% to 97.90%, and from 17.77% to 75.91%, respectively. The volatilization rate of lead and silver increased slowly under the content of calcium chloride
of 12%, but both maintained a high volatilization rate, which reached 93.2% and
86.62%, respectively.
The volatilization rate of lead and silver is relatively high, which is less affected
by the addition amount of calcium chloride. The volatilization rate of zinc, copper,
and indium metal is greatly affected by the addition of chlorinating agent. When the
content of calcium chloride added is of 24%, zinc, lead, and copper can obtain better
volatilization results, which are 99.43%, 99.86%, and 97.90%, respectively. If only
lead and silver are recovered, the chlorinating agent is added in an amount of 16%,
and the volatilization rate can reach 99.02% and 95.21%, respectively. If multiple
elements are recovered in the same process, the chlorinating agent content should be
increased to 24%.
By comparing Figs. 4 and 5, it can be found that under the condition of 3% addition of reducing agent pulverized coal, the volatilization rates of lead, zinc, copper,
and silver are all increased, and the evaporation rate of lead and silver is particularly significant. The volatilization rate of lead and silver increases from 30.21%
to 93.20% and from 37.46% to 86.62%, respectively, under the content of calcium
chloride added of 12%. This is supposed to be the addition of pulverized coal to
create a CO reducing atmosphere, which can accelerate the reduction in lead and
zinc and increase the volatilization rate. However, the volatilization rate of indium
is significantly reduced from 55.67 to 17.77% under the same conditions. So, the
addition of pulverized coal is not conducive to the volatilization of indium.
Effect of Roasting Temperature Under Pulverized Coal
The effect of roasting temperature on the volatilization rates is investigated under
pulverized coal. The roast temperature was varied from 800 to 1200 °C using calcination time of 2 h, chlorinating agent content of 24%, total feed amount of 50 g,
and pulverized coal addition amount of 3%. The effects of the volatilization rates of
copper, silver, and indium are shown in Table 4 and Fig. 6.
It can be seen from Fig. 6 that the influence of roasting temperature on the
volatilization rate of different metals is obviously different. The temperature has
little effect on the volatilization rate of lead and indium, and the degree of influence
on the volatilization rate of zinc, copper, and silver is large. During the roast temperature increase from 800 to 1200 °C, the volatilization rate of lead element is almost
always maintained at a high volatilization rate of 96–99%. The volatilization rate of
indium element is only maintained in the range of 52–58%. The volatilization rate
of zinc, copper, and silver element increased from 58.68% to 98.26%, from 21.84%
to 94.78%, and from 12.03% to 97.31%, respectively.
H. B. Wang et al.
increases greatly. When the amount of calcium chloride increased from 12 to 28%,
the volatilization rate of zinc, copper, and indium increased from 26.33% to 99.43%,
from 15.38% to 97.90%, and from 17.77% to 75.91%, respectively. The volatilization rate of lead and silver increased slowly under the content of calcium chloride
of 12%, but both maintained a high volatilization rate, which reached 93.2% and
86.62%, respectively.
The volatilization rate of lead and silver is relatively high, which is less affected
by the addition amount of calcium chloride. The volatilization rate of zinc, copper,
and indium metal is greatly affected by the addition of chlorinating agent. When the
content of calcium chloride added is of 24%, zinc, lead, and copper can obtain better
volatilization results, which are 99.43%, 99.86%, and 97.90%, respectively. If only
lead and silver are recovered, the chlorinating agent is added in an amount of 16%,
and the volatilization rate can reach 99.02% and 95.21%, respectively. If multiple
elements are recovered in the same process, the chlorinating agent content should be
increased to 24%.
By comparing Figs. 4 and 5, it can be found that under the condition of 3% addition of reducing agent pulverized coal, the volatilization rates of lead, zinc, copper,
and silver are all increased, and the evaporation rate of lead and silver is particularly significant. The volatilization rate of lead and silver increases from 30.21%
to 93.20% and from 37.46% to 86.62%, respectively, under the content of calcium
chloride added of 12%. This is supposed to be the addition of pulverized coal to
create a CO reducing atmosphere, which can accelerate the reduction in lead and
zinc and increase the volatilization rate. However, the volatilization rate of indium
is significantly reduced from 55.67 to 17.77% under the same conditions. So, the
addition of pulverized coal is not conducive to the volatilization of indium.
Effect of Roasting Temperature Under Pulverized Coal
The effect of roasting temperature on the volatilization rates is investigated under
pulverized coal. The roast temperature was varied from 800 to 1200 °C using calcination time of 2 h, chlorinating agent content of 24%, total feed amount of 50 g,
and pulverized coal addition amount of 3%. The effects of the volatilization rates of
copper, silver, and indium are shown in Table 4 and Fig. 6.
It can be seen from Fig. 6 that the influence of roasting temperature on the
volatilization rate of different metals is obviously different. The temperature has
little effect on the volatilization rate of lead and indium, and the degree of influence
on the volatilization rate of zinc, copper, and silver is large. During the roast temperature increase from 800 to 1200 °C, the volatilization rate of lead element is almost
always maintained at a high volatilization rate of 96–99%. The volatilization rate of
indium element is only maintained in the range of 52–58%. The volatilization rate
of zinc, copper, and silver element increased from 58.68% to 98.26%, from 21.84%
to 94.78%, and from 12.03% to 97.31%, respectively.