A six-step, two-bed dual-reflux pressure swing adsorption process for air separation using LiLSX zeolite was first developed and studied systematically. Then two original integrated vacuum pressure swing adsorption processes were well designed ground on the analysis of the mass transfer behavior in the adsorption column, in order to overcome some difficult obstacles that exists in a dual-reflux process, such as low processing capacity and high energy consumption. The performance comparison results show that the adsorbent productivity of dual-reflux process, integrated process I and process II were 17.436, 34.007, and 36.741 NLO 2 /(kg h) and the energy consumption of those were 1.897, 0.681, and 0.762 kW h/Nm 3 O 2 , respectively. Accordingly, for integrated process I and process II, performance parameters of processing capacity and adsorbent productivity are almost twice than that of a dual-reflux process, yet energy consumption is only one-third that of a dual-reflux process. Then in-depth discussions for these results were analyzed in detail and comparison between two integrated vacuum pressure swing adsorption processes and dual-reflux process and comparison of two different integrated vacuum pressure swing adsorption processes themselves were also investigated systematically.
Suspension magnetization roasting followed by magnetic separation is an innovative and effective way to recover iron from refractory iron ores, and the particle size of the ore greatly affects the roasting index. To identify the effect of particle size on the reduction kinetics for the transformation of hematite to magnetite, a high-purity hematite ore with different size fractions were isothermally reduced using a suspension roaster. The pure hematite ore was divided into-1000+500 µm,-500+150 µm,-150+74 µm,-74+37 µm and-37 µm size fractions, while the gas mixture of CO and CO2 with a volume ratio of 1:4 was used as reductant. The results showed that the most suitable mechanism function for the reduction of-37 µm size fraction hematite ore is the Avrami-Erofeev model. In the case of-500+37 µm size fraction, the reduction process can be described by first-order chemical reaction model. For-1000+500 µm size fraction, the reduction of hematite ore is restricted by the second-order chemical reaction. In addition, scanning electron microscopy (SEM) analysis results demonstrated that the transformation of hematite particles to magnetite is in accordance with the characteristics of shrinking core model. The phase transformation primarily occurs at the edge of hematite particles and then develop towards the inner side of particles. The findings of this paper provide a theoretical basis for the development and utilization of refractory hematite ore via suspension magnetization roasting technology.
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