Adsorption of sodium oleate at the microfine hematite/aqueous solution interface and its consequences for flotation

The adsorption of sodium oleate(NaOL)at the microfine hematite/aqueous solution interface was investigated in this paper.Experimental research indicated that negative effects stemmed from the dissolution of the microfine hematite(D50=19.21μm)could be effectively eliminated via the appropriate dosage of NaOL at alkali pH conditions.Solution chemistry calculation and adsorption test results indicated that RCOO
and(RCOO)_(2)^(2-) ions were responsible for microfine hematite flotation at pH 8.2.Zeta potential and FTIR measurements confirmed the co-adsorption of molecular and ionic oleate species occurred at pH 8.2.X-ray photoelectron spectroscopy(XPS)results further indicated that oleate species interacted with hematite surfaces mainly through chemisorption,giving rise to molecule/colloid formation of oleate and Fe―OL complex compound.Time-of-flight secondary ion mass spectrometry(ToF-SIMS)results demonstrated that oleate species adsorbed onto the hematite surfaces with a thickness of a few nanometers.Furthermore,the normalized peak intensity of C4H7+ions on the hematite sample at pH 8.2 increased remarkably comparing with corresponding result of hematite sample at pH 6.8.The new findings of the present study well revealed the dissolution of microfine hematite and the pH effects on the hematite flotation,as well as the adsorption characteristics of oleate species.

含方向纵联的邻线闭锁式配电网电流保护配置方案

本文首先概述了邻线闭锁式电流保护的设计思路,随后基于双端故障的方向纵联保护原理,设计了一种含方向纵联的邻线闭锁式配电网电流保护配置方案。该方案中采用光纤通道传输电气信息,在比较双端信息的基础上实现对故障的准确定位。在确定故障后,及时切断故障所在线路,然后立即重合闸让配电网恢复正常运行。使用Matlab仿真软件对该方案进行了仿真验证,结果表明断路器能准确、快速的将人为设定的故障切除,在0.6 s后完成重合闸,该保护方案具有可行性。

基于光伏并网系统的变步长最大功率追踪研究

针对定步长电导增量法小步长追踪响应速度慢、大步长易出现振荡的缺点,提出了一种改进型变步长电导增量算法。同时分析了光伏三相并网发电系统的控制策略,利用PSCAD仿真软件搭建了光伏三相并网发电系统的仿真模型。在该模型中,通过改变光照和温度条件,对改进型变步长电导增量算法进行了仿真验证,相同条件下对定步长电导增量法进行了仿真,并与变步长算法进行了对比。仿真结果对比表明,改进型变步长电导增量算法不仅兼顾了对最大功率的快速响应追踪和最大功率保持稳定的优点,同时还改善了光照强度或温度下降的情况下产生的功率过冲现象,有效地提高了光伏并网系统的效率和稳定性。