超声波辅助插层-剥离法制备煤系高岭土微粉的研究

我国煤系高岭土储量丰富,为满足造纸、纺织等行业个性化的需求,通常要对其进行深加工。以山西朔州煤系高岭土为原料,分别在恒温磁力搅拌和超声波作用下探究了煤系高岭土/二甲基亚砜(DMSO)插层复合物制备的最佳条件,在插层复合物的基础上对煤系高岭土进行超声辅助剥离,制备得到高岭土微粉,并利用XRD、SEM、BET、TG-DSC等方法分析表征样品。正交实验结果表明在磁力搅拌条件下DMSO用量、插层时间以及插层温度均对插层率具有一定的影响,引入超声波有利于高岭土插层率的提升。插层复合物经超声辅助剥离后晶粒厚度明显减小,高岭土片层状结构大体上呈现碎片化,仅保留少部分大的片状结构,其边缘碎化,整体上也出现碎裂的趋势。剥离样品的比表面积和孔径均大幅度增加,为硬质高岭土的剥离和超微细粉体的制备提供了新的思路。     

Failure load prediction and optimisation for adhesively bonded joints enabled by deep learning and fruit fly optimisation

Adhesively bonded joints have been extensively employed in the aeronautical and automotive industries to join thin-layer materials for developing lightweight components. To strengthen the structural integrity of joints, it is critical to estimate and improve joint failure loads effectually. To accomplish the aforementioned purpose, this paper presents a novel deep neural network (DNN) model-enabled approach, and a single lap joint (SLJ) design is used to support research development and validation. The approach is innovative in the following aspects: (i) the DNN model is reinforced with a transfer learning (TL) mechanism to realise an adaptive prediction on a new SLJ design, and the requirement to re-create new training samples and re-train the DNN model from scratch for the design can be alleviated; (ii) a fruit fly optimisation (FFO) algorithm featured with the parallel computing capability is incorporated into the approach to efficiently optimise joint parameters based on joint failure load predictions. Case studies were developed to validate the effectiveness of the approach. Experimental results demonstrate that, with this approach, the number of datasets and the computational time required to re-train the DNN model for a new SLJ design were significantly reduced by 92.00% and 99.57% respectively, and the joint failure load was substantially increased by 9.96%.     

Impact of inorganic waste fines on structure of mullite microspheres by reaction sintering

The impact of waste composition and morphology on the properties of the mullite microstructure were studied by reaction sintering two types of siliceous waste powders with calcined alum sludge. Stoichiometric mixtures of fly ash or rice husk ash with the alum sludge were shaped into mullite microspheres by droplet coagulation. The mullitization reaction was followed by HT-XRD with a distinct difference in onset temperature. The specific powder composition of fly ash (presence of primary mullite) shifted the onset temperature to higher values as compared to the rice husk ash mixture. After sintering at 1600?°C, the mullitization reaction resulted in the same yield for both samples. Although the mullite content in the microspheres was equal, distinct differences on the microstructure could be observed. Reaction sintering of the fly ash mixture resulted in lower total porosity with smaller pore sizes.     

EB-PVD alumina (Al2O3) as a top coat on 7YSZ TBCs against CMAS/VA infiltration: Deposition and reaction mechanisms

Al₂O₃ was deposited as a top coat on a standard 7YSZ layer (or layers) by means of EB-PVD technique and the corresponding morphology of the Al₂O₃/7YSZ coatings was studied in detail. This multi-layer TBC system was tested against calcium-magnesium-aluminium-silicate (CMAS) recession by performing infiltration experiments for different time intervals from 5?min to 50?h at 1250?°C using two types of synthetic CMAS compositions and Eyjafjallajökull volcanic ash (VA) from Iceland. The results show that the studied EB-PVD Al₂O₃/7YSZ coatings react quickly with CMAS or VA melt and form crystalline spinel (MgAl_2-xFe_xO₄) and anorthite (CaAl₂Si₂O₄) phases. The presence of Fe-oxide in the CMAS has been found to be key element in influencing the spinel formation which was proved to be more efficient against CMAS sealing in comparison to the Fe-free CMAS compositions. Even though a rapid crystallization was assured, shrinkage cracks in the EB-PVD alumina layer produced during the crystallization heat treatment have proven to be detrimental for the CMAS/VA infiltration resistance. To overcome these microstructural drawbacks, an additional alumina deposition method, namely reaction-bonded alumina oxide (RBAO), was applied on top of EB-PVD Al₂O_3. RBAO acts as a sacrificial layer forming stable reaction products inhibiting further infiltration.     

基于制备超细复合含能材料的对置受限式撞击流反应器微观混合性能

由于对置受限式撞击流反应器较高的传热及混合效率，能够制备出粒径小、均匀且分布范围窄的超细颗粒。本文采用碘化物-碘酸盐平行竞争反应体系研究入射速度、结构尺寸对对置受限式撞击流反应器微观混合效果的影响规律，并将混合腔尺寸同等比例放大一倍进行对比研究。结果表明，随着入射速度的增大，离集指数减小，微观混合效果提高。喷嘴间距与喷嘴直径比的增大使得离集指数增大，微观混合效果降低。离集指数随着混合腔高度、混合腔出口尺寸的增大呈现先增大后减小的趋势，且混合腔高度对混合效果的影响较混合腔出口尺寸显著。将对置受限式撞击流反应器混合腔尺寸扩大一倍，离集指数增加到原来的2.4倍，微观混合效果显著下降，但是在较大入射速度下，两种结构的混合效果差距减小。研究结果可为纳米复合含能材料的制备提供高效、安全的技术支持。     

粉煤灰基地质聚合物凝结时间的影响因素研究

以粉煤灰为原料,系统研究了水玻璃模数及掺量、水胶比、温度、外掺剂等参数对粉煤灰基地质聚合物凝结时间的影响。研究结果表明,随着温度升高,地质聚合物凝结时间显著降低; 在10 ℃条件下,地质聚合物凝结时间随着水玻璃掺量增加而增加,随水玻璃模数增加先增加后减小,水胶比对地质聚合物凝结时间影响较小,掺入Ca(OH)₂会促进地质聚合物的凝结。在粉煤灰掺量100%、水玻璃模数1.2、水玻璃掺量8%、水胶比0.35、养护温度10 ℃条件下,地质聚合物的初凝及终凝时间分别为65 min和114 min,在养护3 d和28 d后,地质聚合物的强度分别为23 MPa和51.7 MPa。     

Hydrometallurgical recovery of zinc from industrial hot dipping top ash

Top ash from hot-dip galvanizing plant was investigated as a source of secondary zinc to be returned to galvanizing bath. The waste material contained 63% Zn as metallic, oxide and hydroxychloride phases. It was leached in H₂SO₄ solutions (20% and 25%) at various bath loadings (100−300 g/L). Leaching behaviors of zinc, manganese, iron and chloride ions were investigated. A few strategies of iron elimination from leaching liquors were examined. Flocculant addition was harmful for subsequent filtration of iron precipitates due to increased viscosity of solution, while a combination of zinc oxide and calcium carbonate for rising pH resulted in the formation of dense suspension unenforceable to separate from zinc sulphate solution. Zinc electrowinning was carried out at different pH (from −0.5 to 2.8) using a range of current densities (3−10 A/dm²). Optimal conditions for pure metal recovery were: leaching in 20% H₂SO₄ solution at zinc ash content 100−150 g/L, Fe₂O₃·xH₂O precipitation using H₂O₂ and CaCO₃, zinc electrowinning at pH of 0.1−1.0 at 3−6 A/dm². Correlations between pH and free H₂SO₄ concentration in electrolyte solutions were also discussed. pH−acid concentration dependence for zinc electrolyte was between experimental and calculated curves for pure H₂SO₄ solutions, while the curve was shifted towards lower pH if ferric ions were in the solution.     

Parametric optimization of packed bed for activated coal fly ash waste heat recovery using CFD techniques

Coal fly ash is an industrial solid waste generated from coal preparation during the processing and cleaning of coal for electric power generation. Comprehensive investigation on the reutilization of waste heat of activated coal fly ash is of great economic significance. The method of recovering the waste heat, proposed in this study,is the transfer of heat from activated coal fly ash to gas with the movement of air using the packed bed, providing valuable energy sources for preheating the raw coal fly ash to reduce the overall energy consumption. The investigation is carried on the heat transfer characteristics of gas–solid(activated coal fly ash) phases and air temperature fields of the packed bed under some key conditions via computational fluid dynamics. A two dimensional geometry is utilized to represent key parts of packed bed. The distribution mechanism of the temperature field for gas phase is analyzed based on the transient temperature contours at different times. The results show that the obtained rule of gas–solid heat transfer can effectively evaluate the influences of operating parameters on the air temperature in the packed bed. Simultaneously, it is found that no temperature differences exist in the hot air at the outlet of the packed bed. The investigation provides guidance for the design and optimization of other similar energy recovery apparatuses in industries.     

准东煤灰提取氧化铝和白炭黑技术研究

为实现准东煤灰的绿色化综合利用,笔者研究设计了从准东煤灰中制取氧化铝和白炭黑的工艺流程,确定了最佳工艺条件,并通过SPSS双变量分析比较不同影响因素对提取率影响程度。试验采用准东煤--将军庙原煤,破碎并用马弗炉模拟煤粉炉静态燃烧方式制取灰样。准东煤灰的成分分析和元素分析表明:SiO2占48.84%,Al2O3占31.26%。参照标准制备灰样,对灰样进行SEM分析,发现粘黏性严重,因此试验前先进行机械研磨。采用煤灰与硫酸铵焙烧法制备氧化铝,工艺分为焙烧过程和酸浸过程。因滤液中含有大量杂质铁、钙等元素,采用pH调节法除杂并对除杂效果进行检验,检验结果为除杂率接近100%。从提铝渣中制备白炭黑分为碱浸过程和多次碳分过程。在提铝工艺焙烧过程中,通过提铝率变化曲线及节能角度确定了各因素的最佳试验条件为:焙烧温度600℃,焙烧时间60 min,焙烧配料比1∶6;在提铝工艺酸浸过程中,得到最佳试验条件为:酸浸温度60℃、酸浸时间20 min、H2SO4浓度0.2 mol/L、酸浸液固比50。从提铝渣制备白炭黑研究中,通过SEM观察到提铝渣疏松多孔,有利于进一步的提硅试验。通过XRD对提铝渣分析,得出提铝渣中含有大量硅、钙元素;用K值法(RIR法)求得提铝渣中Si含量及经提铝后的Si损失率为7.64%。得出碱浸过程最佳试验条件为:碱浸温度60℃、碱浸时间30 min、碱浸NaOH浓度3 mol/L、碱浸液固比70,此时Si提取率为99%。采用多次碳分法进行提硅能够满足不同硅含量纯度要求,得到最佳碱浸工艺条件为碳分pH=9.5、CO2通气速率24 m L/min、碳分NaOH浓度0.2 mol/L、碳分液固比80。通过双变量相关性分析,得到各因素对提铝率、SiO2提取率及H2SiO3沉淀率影响程度大小分别为:焙烧温度>焙烧时间>焙烧配料比,酸浸时间>酸浸温度>H2SO4浓度>酸浸液固比,碱浸液固比>碱浸温度>NaOH浓度>碱浸时间,碳分pH>碳分液固比>碳分NaOH浓度>CO2通气速率。通过经济性及可行性分析,说明提出的工艺能有效实现准东煤灰的绿色化综合利用。从提铝后的滤液中重新提取(NH4)2SO4,实现生产原料的再利用;碳分过程后的Na2CO3溶液可通过加入石灰苛化的方式实现NaOH可循环利用于提取工艺生产;本工艺除生产氧化铝和白炭黑外,还能获得Na2SO4等附加产品。     

生活垃圾焚烧炉渣水稳定性试验研究

以福州红庙岭生活垃圾焚烧炉渣为试验对象,测试不同吸水时间和干湿循环次数下炉渣试件无侧限抗压强度和CBR的变化规律,揭示炉渣填料在水作用下的强度变化特征。结果表明:炉渣试件无侧限抗压强度和CBR随吸水时间和干湿循环次数的增加而增大,具有良好的水稳定性。炉渣的强度主要依靠水泥熟料和活性物质化学反应产生水化产物形成的,这使得炉渣在潮湿路基的回填、管槽周边的回填具有显著优势。