Demineralization of a UK bituminous coal using HF and ferric ions

A UK bituminous coal has been used to study demineralization by two-stage chemical leaching. The first-stage uses hydrofluoric acid (HF) at 65 °C and reduces the ash content from 5.30 wt% to 1.37 wt% by mainly removing Al and Si containing minerals. Subsequent leaching by ferric ions decreases the ash content further to 990 ppm by removing most of the pyrite and fluorides formed during the HF leaching. Calorific value of the coal shows no change following leaching, which suggests no oxidation is occurring to the coal carbonaceous matrix. The mercury and sulfur contents after the two-stage leaching sequence decrease by 40% and 26%, respectively.     

废弃焦粉提纯新工艺研究

针对高灰分焦粉大量废弃堆存的状况,采用不同浸出剂对高灰分焦粉进行脱灰实验,确定了碱-酸联合浸出的脱灰工艺,研究了碱-酸联合浸出脱灰过程温度与脱灰率的关系.使用光谱分析、XRF和化学分析方法,分析了原料焦粉、碱浸焦粉、碱浸后酸浸焦粉灰分中主要杂质元素铁、铝、钙、硅的存在形态和含量,探讨了提纯过程的反应机理.焦粉经碱-酸联合浸出后,灰分由28.6％降至3.85％,脱灰率达到86.5％.     

脱盐水装置之反渗透系统污堵原因解析

介绍了脱盐水装置反渗透系统生产运行中产生的污堵现象和相关数据;简述了垢样分析和模拟分析的试验结果;分析了反渗透系统污堵的原因;提出了及时对设备反冲洗、控制药剂用量、调整过滤器等技改方案.结果表明,技改后的反渗透系统运行稳定,不仅解决了污堵问题,而且可节省药剂费和耗材费约260万元/a.     

超高压机组供热后的化学水汽品质监督浅析

超高压、汽包炉自然循环机组经设备改造后向外供热,供热后机组的水汽品质与供热前有一定的差异。通过比较机组水汽品质监督数据的差异,分析原因并采取有针对性的措施。通过化学监督管理手段,切实有效地提高了机组的水汽品质。     

Estimation Method for Exchange Capacity of Mixed Bed Using Monitoring Minicolumns

The methods of estimation of the exchange capacity of mixed bed demineralizer used in nuclear power plants were studied for the purpose of protection against contamination of condensed water with leaked sea water flowing as a coolant in the heat exchanger. It was identified by numerical calculations and experimental works that the performance of mixed bed could be represented by the model for a system of single sort of ion exchange resin and single solute.

The intraparticle diffusivities and ion exchange equilibrium constants for the monitoring minicolumns can be obtained experimentally with the breakthrough curves for different packed height and the equilibrium constant for lm packed height can be known by extrapolation. The constants for 1 m packed height are substituted to the theoretical approximate formula which has been already recognized as a solution for the transient behavior of the adsorption system of a single solute, then the breakthrough time for actually working column of 1 m packed height can be calculated. For the rough estimation of degree of degradation for the deteriorated resin, a simple prediction method was presented in which the relations between the initial concentrations of the effluent from the minicolumns and the packed heights were applied.     

Influence of pH cycling and mechanical loading on the resin-dentin microtensile bond strength

The durability of adhesive interfaces is still a problem in adhesive restorations in dentistry. Laboratorial ageing methods have been proposed to predict the performance of materials, but they still require standardization. The objective of this study was to evaluate the resin-dentin microtensile bond strength of composite restorations subjected to pH cycling and different levels of mechanical loading. Resin blocks were built over a flat superficial dentin of bovine incisors (n = 40), using a three-step adhesive system. Half of the specimens were submitted to 10 cycles of pH cycling, followed by mechanical loading (0, 500,000; 1,000,000; 2,000,000 cycles – 98 N, 4 Hz). The other half was directly subjected to mechanical loading. After ageing, all groups were subjected to a microtensile bond test. Data were analyzed using two-way ANOVA and Tukey’s test (α = 0.05). The frequency of the early de-bonding was compared using the Chi-square test (α = 0.05). The statistical analysis revealed that the cross-product interaction ‘pH cycling’ vs. ‘number of mechanical loading cycles’ (p = 0.72) as well as the main factor ‘pH cycling’ (p = 0.49) was not statistically significant, and they were not able to reduce the resin–dentin bond strength values. Regarding the number of mechanical loading cycles, the groups subjected to 2,000,000 cycles showed lower bond strength values than the others (p = 0.003). The frequency of debonded specimens increased with mechanical loading. Therefore, it can be concluded that in this restorative model, at least 2,000,000 mechanical cycles are need to decrease the microtensile strength and simulate the ageing of the interface.     

Different bacterial models for in vitro induction of non‐cavitated enamel caries‐like lesions: Microhardness and polarized light miscroscopy analyses

The aim of this study was to compare different bacterial models for in vitro induction of non‐cavitated enamel caries‐like lesions by microhardness and polarized light microscopy analyses. One hundred blocks of bovine enamel were randomly divided into four groups (n = 25) according to the bacterial model for caries induction: (A) Streptococcus mutans, (B) S. mutans and Lactobacillus acidophilus, (C) S. mutans and L. casei, and (D) S. mutans, L. acidophilus, and L. casei. Within each group, the blocks were randomly divided into five subgroups according to the duration of the period of caries induction (4–20 days). The enamel blocks were immersed in cariogenic solution containing the microorganisms, which was changed every 48 h. Groups C and D presented lower surface hardness values (SMH) and higher area of hardness loss (ΔS) after the cariogenic challenge than groups A and B (P < 0.05). As regards lesion depth, under polarized light microscopy, group A presented significantly lower values, and groups C and D the highest values. Group B showed a higher value than group A (P < 0.05). Groups A and B exhibited subsurface caries lesions after all treatment durations, while groups C and D presented erosion‐type lesions with surface softening. The model using S. mutans, whether or not it was associated with L. acidophilus, was less aggressive and may be used for the induction of non‐cavitated enamel caries‐like lesions. The optimal period for inducing caries‐like lesions was 8 days. Microsc. Res. Tech. 78:444–451, 2015. © 2015 Wiley Periodicals, Inc.     

煤化学净化的新发展—温和化净化

煤的深度净化需利用化学净化方法，但传统的化学净化方法反应条件苛刻，操作成本十分昂贵，过程的经济性抑制了这些方法的工业化。本文介绍几种该领域最新开发的煤的温和化净化方法，这些新方法的独特性是温和化、高效率、高选择性。有趣的是这些新方法大部分采用有机溶剂抽提煤，溶剂均可通过简单的物理方法加以回收、重新利用。这使得这些新方法在经济上更具吸引力。     

锅炉水质安全与节能

锅炉作为能源消耗大户,其节能、节水十分重要。通过对锅炉水质的软化以及提高蒸汽凝结水的回收率,可收到较好的节能降耗效果,冷凝水回收率在80%时,每年可节约燃料油470t,每年再生剂用量从200t降到140t左右。