Pickling sludge can be produced from metal surface treatment process. Researches showed that the pickling sludge contained a large amount of Fe, which was a potential recyclable resource. However, the existing high-temperature reduction roasting processes mostly used coke or coal as reductant, which resulted in the disadvantage of high reaction temperature, energy consumption large and easy to produce greenhouse gases. Using biomass as reductant, the factors affecting the reduction-magnetic separation process of acid-washed sludge at low and medium temperature were conducted by employing a pyrolysis-magnetic separation process in this work. The chemical composition and phase analysis of pickling sludge and product were analyzed by XRF and XRD. According to the thermodynamic analysis, the possible reduction reaction in the process of biomass reduction of magnetic separation and pickling sludge was proposed. The effects of pyrolysis temperature, varieties and quantity of straws, magnetic field strength and magnetic particle size on product grade and recovery were investigated. The results showed that without reducing agent, the recovery rate of iron was low, which was 63.79% at 700℃. The reduction magnetization of pickling sludge promoted by adding biomass, and the recovery rate of the product reached the maximum value of 92.65% when the dosage of cotton stalks was 5wt%. The addition of biomass had little effect on the Fe content of products. The increase of magnetic field intensity improved the recovery of Fe, but the grade of product decreased. The magnetic particle size had little influence on the recovery rate. The optimum technological conditions of experiment were pyrolysis temperature of 700℃, addition of 5wt% cotton stalks, magnetic particle size less than 0.074 mm particles accounted for 70% of the total quality, magnetic field intensity of 200 mT. Under the conditions of the process, the iron grade of product recovered from pickling sludge was 67.72wt%, and the recovery rate was 91.83%.
Yi ZHANG Qiang SONG Xinqian SHU
. Reduction?magnetic separation of stainless steel pickling sludge by biomass[J]. The Chinese Journal of Process Engineering, 2019
, 19(6)
: 1111
-1119
.
DOI: 10.12034/j.issn.1009-606X.219134
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