Waste cooking oil is a kind of biomass energy that has not been used very well. In this work, waste cooking oil was used as reducing agent to reduce the copper slag by pyrolysis at different temperatures. The pyrolysis experiments at high temperature (1373?1573 K) showed that the pyrolysis products were mainly small molecule reductive substance such as C, H2, CO and CH4. At 1373, 1473 and 1573 K, the conversion rates of carbon deposits were 78.36%, 79.83% and 80.07%, respectively, so after pyrolysis the carbon element in waste cooking oil mainly existed in the form of carbon deposits. Thermodynamic analysis showed that these pyrolysis products had good reduction activity to magnetic (Fe3O4) at high temperature, it was feasible to use waste cooking oil instead of traditional fossil reductant to realize the reduction of magnetic in copper slag. Using N2 as the carrier gas was not only conducive to the waste cooking oil blowing into copper slag at high temperatures, but also agitates the slag through the momentum transfer, increasing the chance of the tiny copper droplets aggregating and growing. Under the optimum conditions of melting temperature 1573 K, flow rate of waste cooking oil 2.055 mL/min, flow rate of carrier gas 3 L/min, blowing time 4 min and settling time 50 min, the content of Fe3O4 in copper slag decreased from 33.40wt% to 1.60wt%, the content of Cu in copper slag decreased from 4.49wt% to 0.49wt%, the Fe3O4 phase was transformed into 2FeO?SiO2 phase. According to the Einstein?Roscoe equation, the decrease of Fe3O4 in slag was favorable to the decrease of viscosity, thus improving the settling conditions of copper droplets. However, increasing the blowing time of waste cooking oil to deeply reduction of Fe3O4 would increase the impurity content in the deposited metal and prolonging the settling time, because of the mechanical entrainment and chemical dissolution of copper slag to the copper, it could not bring a better settlement effect. The final recovery rate of copper in experiment was 89.09%.
Guangping DAI Yu SHI Shiwei ZHOU Bo LI Yonggang WEI
. Reduction and dilution of melting copper slag by blowing waste cooking oil[J]. The Chinese Journal of Process Engineering, 2019
, 19(4)
: 759
-766
.
DOI: 10.12034/j.issn.1009-606X.219114
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