1 test
1.1 Test raw fuel
In a lead-zinc plant Hydrometallurgy alumina solid scrap residue for the study, test Jilinsengong anthracite as a reducing agent, pure hydrogen is oxidized to calcium flux analysis. The analysis results of iron-vanadium slag and anthracite are shown in the literature [6].
1.2 Test methods and procedures
The iron slag has a large water content (about 35%). Therefore, it is fully dried in a blast drying oven at 110 °C, and then iron slag, slaked lime, coal powder, binder and water are mixed in a mixer according to a certain ratio. After mixing evenly, the pelletizing machine is used to make the ball. The cold-solidified carbon-containing pellets are dried, and then weighed into corundum crucibles and placed in a silicon- molybdenum rod heating well furnace for reduction test. After the direct reduction, the metallized pellets were ground, and the content of total iron, metallic iron, lead and zinc in the reduced pellets were determined by chemical capacity method and ICP method, and the metallization rate and the volatilization rate of lead and zinc were calculated. The metallized pellets were ground and subjected to magnetic separation under the conditions of Φ50mm magnetic separation tube and magnetic field strength of 47.76～238.8 kA/m (60~300 mT, 1 mT=796 A/m) to calculate the magnetic separation iron concentrate grade. And iron recovery rate. Finally, in the 3 L single-flot flotation machine, the magnetic flotation iron concentrate is subjected to floating silicon and iron suppression, and the silicon gangue is removed to improve the iron concentrate grade.
2 Test results and discussion
2.1 Changes in metallization rate during direct reduction
The preparation of high metallization pellets is the basis for magnetic separation of iron concentrates. Test conditions: reduction temperature 1 300 ° C, carbon ratio 1.4, alkalinity 2.5 (the original alkalinity of iron-vanadium slag is 0.31, adjusted by the addition of calcium hydroxide), the test results are shown in Figure 1.
It can be seen from Fig. 1 that with the increase of reduction time, the metallization rate increases gradually, the metallization rate is 86.3% when the reduction is 10 min, and the metallization rate reaches 98.47% after 30 min reduction, and then tends to be stable. In the previous experiments, it was found that the melting point of pellets was low under natural alkalinity. The reduction temperature could not be set too high between 1 100 and 1 200 °C. The reduction metallization rate was only 90.60%, and the melting point increased after alkalinity. It is beneficial to carry out the gasification reaction of carbon at high temperature and promote the occurrence of direct reduction.
2.2 Changes in the volatilization rate of lead and zinc during direct reduction
Test conditions: reduction temperature 1 300 °C, carbon ratio of 1.4, alkalinity 2.5, the effect of reduction time on the volatilization rate of lead and zinc is shown in Figure 2. Figure 2 shows that with the prolongation of reduction time, the volatilization rate of lead and zinc increases gradually. The volatilization rate of lead and zinc is lower at 41 min reduction, which is 41.5% and 53.2%, respectively. When reducing for 30 min, the volatilization rates of lead and zinc are respectively It reached 86.26% and 98.54%, which increased by 44.76% and 45.34% respectively. After that, the zinc volatilization rate became stable and the lead volatilization rate increased slightly. When the reduction was 40 min, the lead volatilization rate was 90.1%. It can be seen that the direct reduction of carbon-containing pellets can effectively lead and lead, and finally lead and zinc can be recovered from the soot.
2.3 Magnetic separation test
In the direct reduction test, a metallized pellet having a metallization ratio of 98.47% was obtained, and after magnetic grinding, the magnetic separation test was performed. The magnetic separation equipment is DTCXG-ZN50 magnetic separation tube, the magnetic field strength is 0~450 mT, the magnetic separation tube diameter is 50 mm, and the magnetic pole spacing is 52 mm. The magnetic separation result is shown in Fig. 3. It can be seen from Fig. 3 that as the magnetic field strength increases, the recovery rate of iron gradually increases, and finally stabilizes at about 80%. The grade of iron concentrate decreased with the increase of magnetic field strength. The iron concentrate grade was 50.31% at 50 mT, but the yield was only 33.93%. Most of the sponge iron entered the tailings with the slag phase. Overall observation, the change of magnetic field strength has little effect on the grade of iron concentrate, and the impact on recovery rate is relatively large. For the sake of comprehensive consideration, a suitable magnetic field strength is 200 mT. At this time, the iron concentrate I grade reached 46.66%, and could not be sold as commercial iron ore fines, which is lower than the ordinary iron concentrate grade classification standard five (54.0~<60.0%, YB/T 4267-2011), and needs to be enriched. The impurity removal process improves the grade of iron concentrate.
2.4 Reverse flotation test
The reverse flotation test was carried out in an XFD III single-slot flotation machine with a power of 250 W, a volume of 3 L, an impeller diameter of 70 mm and a spindle speed of 1 400 r/min. Weigh 500 g of 46.66% magnetically-selected iron concentrate I to 3 L, and mix for 2 min; starch as an inhibitor of iron, add 200 g/t, stir for 3 min; sodium carbonate as pH adjuster (also for strengthening dispersant [7]), adding a ratio of 1 250 g / t, and stirring for 3 min; then adding the cationic collector dodecylamine (analytical grade) 300 g / t and stirring for 2 min; finally in the drum The reverse flotation was carried out for 6 min under the condition of gas pressure of 600 L/h. The test results showed that the grade of reverse flotation iron concentrate II increased to 60.30%, and the iron recovery rate was 83.15%, indicating that the process route is feasible.
3 Conclusion
(1) Under the conditions of carbon ratio of 1.4, alkalinity of 2.5 and 1 300 °C for 30 min, the direct reduction metallization rate of carbon pellets reached 98.47%, and the lead and zinc volatilization rates were 86.26% and 98.54%, respectively. . After grinding and magnetic separation, 46.66% of iron concentrate I is obtained, and then iron concentrate II with grade 60.30% can be obtained through reverse flotation process.
(2) Direct reduction of iron slag carbon-containing pellets - magnetic separation - reverse flotation process route comprehensive recovery of lead, zinc and high-grade iron concentrate is feasible.
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