Ultrasound irradiation as an effective tool in synthesis of the slag-based catalysts for carboxymethylation

Waste minimization strategy was applied in the current work for synthesis of the catalysts from industrial solid waste, namely desulfurization slag. The starting slag material comprising CaCO₃, Ca(OH)₂, SiO₂, Al₂O₃, Fe₂O₃, and TiO₂ was processed by various treating agents systematically varying the synthesis parameters. A novel efficient technique – ultrasound irradiation, was applied as an additional synthesis step for intensification of the slag dissolution and crystallization of the new phases. Physico-chemical properties of the starting materials and synthesized catalysts were evaluated by several analytical techniques. Treatment of the industrial slag possessing initially poor crystal morphology and a low surface area (6 m²/g) resulted in formation of highly-crystalline catalysts with well-developed structural properties. Surface area was increased up to 49 m²/g. High basicity of the neat slag as well as materials synthesized on its basis makes possible application of these materials in the reactions requiring basic active sites. Catalytic performance of the synthesized catalysts was elucidated in the synthesis of carbonate esters by carboxymethylation of cinnamyl alcohol with dimethyl carbonate carried out at 150 °C in a batch mode. Ultrasonication of the slag had a positive effect on the catalytic activity. Synthesized catalysts while exhibiting similar selectivity to the desired product (ca. 84%), demonstrated a trend of activity increase for materials prepared using ultrasonication pretreatment. The choice of the treating agent also played an important role in the catalytic performance. The highest selectivity to the desired cinnamyl methyl carbonate (88%) together with the highest activity (TOF₃₅ = 3.89*10⁻⁷ (mol/g*s)) was achieved over the material synthesized using 0.6 M NaOH solution as the treating agent with the ultrasound pre-treatment at 80 W for 4 h.     

Characteristics of major dioxin/furan congeners in melted slag of ash from municipal solid waste incinerators

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in slag of fly ash from three municipal solid waste (MSW) incinerators were analyzed to observe any changes in characteristics and distribution of their congeners by melting process. Actual concentration and Toxic Equivalent (TEQ) concentration profiles of 17 major congeners of PCDDs/PCDFs for gas, fly ash and melted slag were compared. The distributions of PCDDs/PCDFs in different streams macroscopically showed similarities with the generally known profiles for emission gas from a municipal waste incinerator. The total concentrations of PCDDs/PCDFs in off-gas and fly ash have been known to be a function of incineration conditions and of air pollution control device utilization; however, their normalized distributions were independent of such conditions. The concentrations of PCDDs/PCDFs in the melted slag of fly ash were not related to the concentrations of PCDDs/PCDFs congeners in fly ash but were rather a function of the melting furnace type and operation. The total amount of PCDDs/PCDFs in the melted slag of fly ash contained almost 150–27,000 times less dioxin than that in fly ash, however, the TEQ of dioxin in the slag was reduced by 435–43,500 times, which could enable them to be utilized as recycled construction materials. In normalized TEQ concentration profiles of 17 congeners of PCDDs/PCDFs, the ratio of PCDFs to PCDDs changed from 1.32 to 2.19 by melting, which showed relatively higher portion of furans left in melted slag than those in fly ash. By comparing reduction ratios of different congeners, PCDDs (dioxins) were relatively easier to destruct than PCDFs (furans) during melting process. The most difficult congener to destruct could be octa-chlorinated dibenzofuran (OCDF) among major congeners. For slag cooling methods, dioxin concentration in TEQ of slow cooled slag by air was four times higher than that of fast cooled slag by water. Thus cooling by water is more appropriate with the added beneficial effect of producing granules/particles, which can be utilized as roadbed materials.     

矿渣粉加固粉土的理论分析及路用性能研究

提出了矿渣粉加固粉土的相关理论。将矿渣粉在加固土中的作用归结为火山灰胶凝效应和微集料填充效应,而火山灰胶凝效应又可进一步归结为水化作用、激发作用和离子交换作用;认为微集料填充效应与矿渣粉细度极为相关;用框图归纳了矿渣粉加固土的两种作用效应。进行了矿渣粉、石灰粉加固土无侧限饱水抗压强度、水稳定性、冻稳定性、温度收缩和干燥收缩等路用性能试验,并进行比较。结果表明,矿渣粉加固土所测路用性能指标优于石灰粉加固土。为工程应用提供了试验依据。     

Design and Application of a Set of Vitreous Standards for EDS-SEM Microanalysis of Melting Shop Slags

Non-metallic inclusions in steel are formed due to interactions between liquid steel and its environment in the melting shop (refractories and slags). Particles not trapped in the slag remain in the cast steel, impairing steel properties in service. Inclusion composition varies and certified standards covering the whole compositional range are unavailable.The present study describes the preparation of a set of homogeneous, glassy and crystalline standards with a wide compositional range for use in analysing non-metallic steel inclusions. For this, materials were designed based on knowledge of the compositional range of interest in the Al₂O₃–SiO₂–CaO–MgO–CaF₂ system, which is the matrix of the most frequent steel inclusions. The composition and microstructural homogeneity of the reference materials was verified.     

Influence of Fe2O3 and V2O5 on Crystalline Structure of Mg-Al Spinel Synthesized by Waste Aluminum Slag

Mg-Al spinel is synthesized by using industrial waste-residue and basic magnesium carbonate in the aluminum factory as the main raw materials. The influence of V2O5 and Fe2O3 mineralizers on the structure, cell parameters and microscopic morphology of synthesized Mg-Al spinel has been discussed. The Mg-Al spinel is characterized by using XRD, SEM and relevant analytical software, such as Philips plus, Rietveld quantification and so on. The experimental results show that certain amounts of V2O5 and Fe2O3 are beneficial to the formation of Mg-Al spinel, and the optimum addition of V2O5 and Fe2O3 is respectively 2wt% and 3wt%. V2O5 has few effects on cell parameters of Mg-Al spinel; but Fe2O3 can form solid solution with Mg-Al spinel in which Mg-Fe spinel can also dissolve to form continuous solid solution. Therefore, with the increase of Fe2O3 content, the cell parameters of Mg-Al approximately present linear increase.     

Suppression of slag foaming by a sound wave

The aim of this work was to study the effects of sound frequency, sound intensity and viscosity of slag on the slag foaming rate and the steady-state foam height. Experiments were carried out using two slags (BaO–B₂O₃) melted at a temperature of 1223 or 1273 K, as well as water–glycerin solutions at room temperature. Low frequency sound waves (<1.3 kHz) are found to be more effective in the slag foaming suppression than high frequency waves (1.3–12 kHz). The steady-state foam height decreases abruptly when the sound pressure reaches a threshold value that depends on sound frequency and liquid viscosity. The results can be explained in terms of enhancing the rates of liquid drainage and film rupture induced by sound.     

CaO-SiO2-Al2O3-MgO-TiOx-FeOy体系氧化动力学

用电动势和化学分析方法研究了富钛还原熔渣－ＣａＯ－ＳｉＯ２－Ａｌ２Ｏ３－ＭｇＯ－ＴｉＯ２－ＦｅＯｙ体系的氧化动力学,得出了氧在熔渣中的扩散速率常数分别为０．６６＊１０＾－５ｍ．ｓ＾－１和１．９８＊１０＾－５ｍ．ｓ＾－１,研究表明：固体电解质构成的氧浓差电池法得出的结果不仅可靠,且方法快速,简便。     

Fast vacuum slag analysis in a steel works by laser-induced breakdown spectroscopy

Samples taken from the liquid slag layer in a vacuum degasser station of a steel works are analyzed after solidification by laser-induced breakdown spectroscopy (LIBS) without any further sample preparation. The mass fractions of the major components of the vacuum slags are in the range of 50–60% for CaO, 0.5–12% for SiO₂ and 20–40% for Al₂O₃. The species are distributed heterogeneously in the solid samples having diameters of 35 mm. Furthermore the color and structure of the samples is varying significantly. A fast spatial averaging of representative sample areas is realized by spatial laser beam shaping. Multivariate calibration and its validation is carried out with calibration and validation sets of production samples which are analyzed by X-ray fluorescence measurements or as borate beads for reference. The laser-induced breakdown spectroscopy instrument is installed in the steel works at a distance of about 10 m from the vacuum degasser. The laser-induced breakdown spectroscopy analysis runs automatically after the sample placement and it takes 80 s including data transfer to the host computer of the steel works. Operational tests are carried out to demonstrate the feasibility of a fast slag analysis in the harsh environment of the vacuum degasser plant.     

自由定标激光诱导击穿光谱技术在炉渣成分定量分析中的应用

采用自由定标激光诱导光谱技术(CF-LIBS)对炉渣中几种主要成分(CaO,SiO2,Al2O3,MgO)进行了定量分析.利用Nd:YAG激光脉冲在空气中烧蚀炉渣样品产生等离子体,等离子体光谱由中阶梯光栅光谱仪记录.通过几种主要元素的原子谱线和离子谱线的玻尔兹曼图,计算了等离子体的温度.利用Ca的一条谱线Stark展宽...     

Effect of slag basicity and oxygen potential on the distribution of boron and phosphorus between slag and silicon

The distribution of boron and phosphorus between Al₂O₃-CaO-MgO-SiO₂ and Al₂O₃-BaO-SiO₂ slags and silicon metal was examined for the purposes of establishing the possibility of refining metallurgical-grade silicon to solar grade silicon. Distribution coefficients of B and P were normalized with the estimated oxygen partial pressure of the system to isolate the influence of basicity as the composition of the slag was varied in terms of the basicity (as CaO:SiO₂ ratio) and oxygen potential (as Al₂O₃:SiO₂ ratio) of the former and of the basicity (as BaO:SiO₂ ratio) of the latter slag systems. For both of these impurity elements, the normalized distribution showed a different dependence on corrected optical basicity in each slag system studied. Values were highest in the Al₂O₃-CaO-MgO-SiO₂ slag with varying SiO₂:Al₂O₃, where the impurities are thought to associate with Mg, and lowest in the Al₂O₃-BaO-SiO₂ slag, where the impurities are thought to associate with Ba. The different dependence on basicity in each system is attributed to the differing manner in which the activity coefficient of the actual impurity compound in the slag varies with basicity. From thermodynamic calculations it was concluded that the difference in normalized distributions between the slag systems is attributed to the magnitude of the ratio of equilibrium constant to activity coefficient of the impurity oxides. It was found that where basicity is equal and the form of the impurity oxide in the slag is equivalent, phosphorus is expected to have a much smaller activity coefficient in the slag than boron.