ABSTRACT
Kish graphite is a typical byproduct of steel production, and its enrichment and purification are essential prerequisites for its high value and comprehensive utilization. To solve the problem of recovery and application of difficult-to-treat kish graphite with a small particle size obtained from metallurgical dust, kish graphite in blast furnace tapping yard dust was effectively enriched and purified by a comprehensive flotation-acid leaching treatment process in this study. The influence of the flotation agents on the flotation process was explored. The results showed that the optimized flotation agent dosage was 500.0 g·t-1 (collector) and 120.0 g·t-1 (frother), respectively. Based on the optimized flotation scheme, a graphite concentrate (FG) with 79.12 % carbon content and 93.5 % carbon recovery was obtained. After the leaching treatment with a HCl-HF mixed acid solution, the carbon content of the graphite concentrate increased to 95.55 %. The ID/IG value of the graphite concentrate was 0.145, and the average lattice spacing was approximately 0.3354 nm. The SEM results showed that the leaching-treated graphite concentrate (AFG) had a loose, fragment-like structure. When used as an anode material for lithium-ion batteries, The AFG still provided a high reversible capacity of â¼370 mAh·g-1 and excellent coulombic efficiency of 99.6 % after 350 cycles. In addition, an industrial-grade recycling and utilization path for kish graphite based on a circular supply chain strategy was proposed. The results of this study may serve as a conceptual basis for the recovery and application of kish graphite from metallurgical dust.
Subject(s)
Graphite , Carbon , Dust , Electric Power Supplies , MetallurgyABSTRACT
Recycling of waste plastics is of great significance for human society. The pulverization of waste film plastics is a key technical link in the development of collaborative utilization of waste plastics in the steel industry. In this study, waste polyvinyl chloride film plastics were first heated at different temperatures; then the de-chlorination ratio pulverization and the properties of the pulverized products closely related to blast furnace injection, such as powdery properties, combustion and explosiveness, were further analyzed. The weight loss ratio increased significantly with an increase in temperature and was not obvious between 370 °C and 400 °C. The highest de-chlorination ratio was approximately 84% at 370 °C, and the relative chlorine content in the product was 9%. The crushing performance of heat-treated polyvinyl chloride film increased with increasing temperature. Before 370 °C, there were more pores in the samples, and the surface of the sample seemed to be damaged with the temperature was further increased. The pulverized polyvinyl chloride had better fluidity and strong jet flow compared to industrial injection coals. At the same time, compared with other carbonaceous materials, it also exhibited better combustion performances. The pulverized polyvinyl chloride belonged to non explosiveness substance despite its high volatile content. The obtained results demonstrated that the pulverized polyvinyl chloride obtained under the present conditions could be used for blast furnace injection to some extent.
ABSTRACT
Herein, the influences of CO2 dilution, N2 dilution, and CO2/N2 (in which half of the N2 is replaced by CO2) dilution on the combustion characteristics of a turbulent, partially premixed CO/H2-air flame were experimentally investigated in terms of the flame structure, flame temperature, and CO and CO2 concentrations in flames. TDLAS (tunable diode laser absorption spectroscopy) technique and an infrared gas analyzer were used for such purposes. CO2 dilution not only increases more momentum but also reduces the reaction rate. This results in a much longer flame length than that under N2 dilution. Compared with N2 dilution, the L H (axial length of the high-temperature reaction zone) values for the same levels of CO2 dilution and CO2/N2 dilution are much longer. The highest CO concentration in the CO2 diluted flame is higher than that in the CO/H2 flame and that in the CO2/N2 diluted flame is higher than in that the N2 diluted flame. The sizes of the main chemical reaction zone in CO2 and CO2/N2 diluted flames are larger than that in the N2 diluted flame. The inflection points in the rates of variation of the flame temperature and the CO and CO2 concentrations verify that CO2 dilution creates lower intensities and lower rates of chemical reactions, compared with N2 dilution.
ABSTRACT
Developing electrocatalytic nanomaterials for green H2 energy is inseparable from the exploration of novel materials and internal mechanisms for catalytic enhancement. In this work, nano-petal N-doped bi-metal (Ni, Co) and bi-valence (+2, +3) (Ni1-x Co x )2+Co2 3+O4 compounds have been in situ grown on the surface of Ni foam. The N3- atoms originate from the amino group in urea and doped in the compound during annealing. The as-synthesized N-doped (Ni1-x Co x )2+Co2 3+O4 nano-petals demonstrate commendable hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) bi-functional catalytic efficiency and stability. Electrochemical measurements confirm that the nitrogen doping significantly improves the catalytic kinetics and the surface area. Density functional theory calculations reveal that the improved HER and OER kinetics is not only due to the synergistic effect of bi-metal and bi-valence, as well as the introduction of defects such as oxygen vacancies, but also it more depends on the shortened bond length between the nitrogen N3- atoms and the metal atoms, and the increased electron density of the metal atoms attached to the N3- atoms. In other words, the change of lattice parameters caused by nitrogen doping is more conducive to the catalytic enhancement than the synergistic effect brought by bi-metal. This study provides an experimental and theoretical reference for the design of bi-functional electrocatalytic nanomaterials.
