Wetting,spreading and corrosion behavior of molten slag on dense MgO and MgO-C refractory

The wetting and spreading phenomena of molten slag were observed in situ on dense MgO and MgO-C refractory substrates. Parameters associated with wetting and spreading of molten slag, such as the contact angle, droplet height, diameter, and volume, were measured and calculated. The microstructure and chemical composition of the corroded dense MgO and MgO-C refractory were studied using SEM and EDS analysis. The droplet volume of molten slag on dense MgO declined faster than that on MgO-C refractory during the first 90?s of the testing period, whereas the droplet volume exhibited little difference across the two cases after 150?s. Molten slag penetrated the dense MgO and MgO-C refractory through grain boundaries and the channels which were formed by the dissolution of MgO. Besides, the slag also penetrated into the MgO-C refractory through the pores and channels formed by the redox reaction between slag and carbon, and a reaction product (Fe) was found at the interface. The dissolution of MgO and redox reactions changed the wetting process and increased corrosion of the MgO-C refractory.     

利用固体激发剂生产^#525碱矿渣水泥

本文阐述了碱矿渣水泥的应用前景及国内碱矿渣水泥研究中存在的问题，介绍了利用固体激发剂生产碱矿渣水泥的研究结果，找出了在试验条件下利用固体激发剂生产碱矿渣水泥的最佳参数，测试了所得碱矿渣水泥性能，初步探索了碱矿渣水泥性能优异的原因。碱矿渣水泥生产能耗低、生产成本低、性能优良，有可能成为一种有发展前途的新型水泥。     

Effects of Al/Na and heat treatment on the structure and properties of glass ceramics from molten blast furnace slag

Glass ceramics with different Al/Na molar ratio from blast furnace slag were prepared using conventional melting-casting method. The structure and properties of glasses or glass ceramics were investigated by DSC, Raman, MAS NMR, XRD, and SEM. The DSC results indicated that the thermal stability (ΔT = T_c-T_g) and crystallization temperature (T_c) of the parent glass firstly increased and then decreased when Al/Na exceeded 1.21. The Raman and ²⁷Al MAS NMR spectra analysis revealed that [AlO₆] increased positively with Al₂O₃/Na₂O. The calculation of Qⁿ ([SiO₄] units with bridging oxygen atoms number of n) suggested an obvious decline of (Q⁰+Q²)/(Q¹+Q³) and that [SiO₄] mainly existed in the form of Q¹ when Al/Na exceeded 1.21, which accorded closely with T_c variation. The crystallization results determined by XRD showed that as Al/Na increased, the main crystal phase was transformed from akermanite to gehlenite and nepheline disappeared. Glass ceramics with Al/Na of 1.48 nucleated at 780 °C for 2 h and crystallized at 880 °C for 3 h exhibited the maximum value of flexural strength. Orthogonal experiment (L9(3⁴)) were carried out to investigated the optimum heat treatment of glass ceramics with a Al/Na of 1.48. The analyses indicated that nucleation time variation has little influence on the flexural strength, and the optimum heat treatment was determined as 760 °C – 1 h–900 °C – 1 h and the flexural strength was characterized as 81.310 MPa.     

Al_2O_3－SiC－C质浇注料抗热震性和抗渣铁侵蚀性的研究

对新研制的Ａｌ２Ｏ３－ＳｉＣ－Ｃ质浇注料和现用出铁沟料的抗热震性和抗渣铁侵蚀性进行了研究、结果表明，该材料具有较高的抗渣铁侵蚀能力和较好的抗热震稳定性。调节Ｓｉ与Ｃ的比例可生成高强度、耐渣蚀的纤维状ＳｉＣ。     

Modification of interface chemistry and slag structure by transition element Cr

A comparative study on CaO–MgO–Al₂O₃–SiO₂ slag and CaO–MgO–Al₂O₃–SiO₂–Cr₂O₃ slag was conducted to investigate the distribution of the elements at the gas-slag interface. The effect of redox states of chromium on the distribution of sulfur and oxygen at the interface was revealed by gas-slag equilibrium method using X-ray photoelectron spectroscopy at 1873K. From the analysis of the S2p core-level spectra, the negative divalent sulfur(S^2?) was detected at the interface in the Cr-bearing slag, which directly proved that sulfur exists in the form of S^2? in the slag for the first time. However, the S^2? peak is very weak at the interface of Cr-free slag. The reason for the difference between the two slags may be due to chromium changing the interface structure. According to the O1s and Cr2p core-level spectra, non-bridged oxygen(O^?) increased, while bridged oxygen(O⁰) decreased with the etching depth deepened. The increase of NBO/BO and Cr²⁺/Cr³⁺ elucidates that Cr³⁺ can modify the structure of the slag as basicity substance, but its effect is weaker than that of Cr²⁺. Meanwhile, due to the affinity of sulfur and chromium, the addition of chromium may also lead to the enhancement of the S^2? peak at the gas-slag interface. Gradient change of elements at the interface proved the existence of the boundary layer.     

固相还原法处理铬渣的研究及工业应用

铬渣作为一种工业危险废弃物,多年来对环境造成了严重污染,迫切需要有效、适用的无害化、资源化处理处置技术。本文介绍了国内外研究较多的固相还原法处理铬渣的解毒方法、研究进展及工业应用,并着重阐述了铬渣作为炼铁熔剂、制砖和旋风炉附烧技术的资源化利用。     

Effect of cooling rate and alumina dissolution on the determination of temperature of critical viscosity of molten slag

In slagging gasifiers with crystalline slag, the fluctuation in temperature near the temperature of critical viscosity (T_cv) can rapidly increase the molten slag viscosity and cause an accumulation of slag inside the gasifier. In order to prevent operational problems caused by the slag, one therefore needs to obtain an accurate measurement of T_cv. The effects of cooling profile and the extent of alumina dissolution on the experimentally determined T_cv were investigated. A synthetic slag was prepared using a composition of Alaskan Usibelli ash, which exhibited crystalline slag behavior, and T_cv was determined under constant cooling and equilibrium conditions. The T_cv measured under 2°C/min of constant cooling was 33°C lower than the T_cv under equilibrium conditions. The effect of alumina dissolution was determined using a platinum (Pt) lined crucible. At a 2°C/min cooling rate, the T_cv measured using a bare alumina crucible was 23°C higher than that from the Pt-lined crucible, offsetting the difference caused by constant cooling. In order to determine a safe gasification temperature range, however, the measurement of T_cv under constant cooling conditions should be avoided.     

The capacitance of the diffuse layer of electric double layer of electrodes in molten salts

Similarly to aqueous electrolytes, the electric double layer of electrodes in molten salts is assumed to be composed of compact and diffuse layers. The charge density of the compact layer, formed as a monolayer of specifically adsorbed anions (primary ionic shell), is calculated as the difference between the charge of the primary ionic shell and the charge removed by the exchange current density. The centre of the specifically adsorbed anions create the inner Helmholtz plane (iHp). The counterions to the specifically adsorbed anions in the primary ionic shell, take place in the numerous neighbouring holes, introduced into the molten salt structure by the melting process, and being subjected to thermal motion, create the diffuse layer. The electrostatically adsorbed metal cations form the outer Helmholtz plane (oHp) with the value of the inner potential equal φ₂. Using the Boltzman and Poissone equations, the equation for the capacitance of the diffuse layer of the metallic electrode in molten salt is derived and tested on some literature experimental results.     

改性对高钛渣酸解性能的影响研究

以碳酸钠为改性剂,研究了改性剂配比、焙烧温度和焙烧时间对高钛渣酸解性能的影响。研究结果表明焙烧改性的适宜条件：焙烧温度为850 ℃,碳酸钠与高钛渣质量比为0.7,焙烧时间为3 h。对改性后的高钛渣进行酸解,在溶解温度为60 ℃、溶解时间为4 h、固液质量比为1∶6条件下,钛的溶出率可以达到97.48%。     

Enhanced dissolution of silymarin/polyvinylpyrrolidone solid dispersion pellets prepared by a one-step fluid-bed coating technique

Solid dispersion systems have been widely used to enhance the dissolution and oral bioavailability of poorly water-soluble drugs. However, the formulation process development and scaling-up present a number of difficulties greatly limiting the commercial applications. In this study, solid dispersions of silymarin (SM) with polyvinylpyrrolidone (PVP) were prepared by a one-step fluid-bed coating technique. The process involved the spray application of the ethyl alcohol solution of SM and PVP and subsequent deposition of the coprecipitates onto the non-pareil pellets in drying air flow in a fluid-bed coater. The central composite design/response surface methodology was employed to investigate the effects of the two independent variables, PVP/SM ratio and coating weight gain, on the dissolution of SM. The results demonstrated that the dissolution of PVP/SM solid dispersions was enhanced greatly at PVP/SM ratios of over 4/1. The results of the central composite design suggested that both PVP/SM ratio and coating weight gain affected the dissolution rate significantly. Second-order or third-order polynomial non-linear equations were employed to estimate the relationship between dissolution responses and the two independent variables. Response surface graphs were delineated based on the best-of-fit equations and the optimal experimental range was identified as: PVP/SM, 4/1−5/1; coating weight gain, 80%−120%. The results indicate that the fluid-bed coating technique has the potential use in the preparation of solid dispersions.     

Combustion synthesis of porous TiC/Ni composites under high gravity

Abstract

Porous TiC/Ni composites were prepared by combustion synthesis under high gravity. In TiC/Ni composites, hollow spheres of 50–200 μm were produced, and their walls were composed of large TiC grains and small Ni particles. A larger average size of the spheres was observed in the samples prepared under high gravity compared with those obtained under normal gravity. Phase segregation was observed under high gravity, and Ni was enriched in the lower part of the samples. It is proposed that the mobility and collision frequency of liquid droplets will increase, and thus, the agglomeration of primary droplets can be enhanced under high gravity.     

超重力技术在脱硫液再生中的探索性研究

用超重力旋转填充床替代再生槽,进行了超重力法再生脱硫液的研究。实验证明,用1台7L的超重力旋转填充床替代原有的320L再生槽,可以达到更好的再生效果。经超重力旋转填充床再生的脱硫液可提高脱硫效率、减少脱硫液的再生时间,且脱硫后出口净化气的硫化氢质量浓度均低于20 mg/m~3,满足了天然气运输的要求。     

超重力法制备纳米材料的研究现状

纳米材料的合成与制备技术已成为全球的研究热点。介绍了一种独创性的纳米材料合成方法即超重力法。论述了超重力法的理论依据,并介绍了目前根据该法合成碳酸钙、氢氧化铝、硫化锌、氧化锌、硫酸钡、钛酸钙等纳米粉体材料的制备方法和工艺流程。     

含钒钢渣对镁碳砖的侵蚀

用感应炉浸渍试验法(熔池温度1650℃左右,侵蚀时间20min)研究了V2O5含量分别为0、1.34%、2.0%、3.15%的钢渣对镁碳砖的侵蚀。结果表明:由于V2O5降低了渣的熔化温度与粘度,含钒钢渣对镁碳砖的侵蚀性明显高于不含钒的普通钢渣,随渣中V2O5含量由0增加到3.15%,镁碳砖的熔损指数由14.3%上升到42.9%,渗透深度比采用普通钢渣时提高1.2倍。渣中V2O5和TiO2随液相渗入砖中,一部分与基质中的碳反应,导致碳的氧化和MgO颗粒在渣中的溶解;另一部分则侵入MgO晶界中肢解镁砂,使骨料破坏,加速对MgO-C砖的破坏。     

固化铬渣的解毒研究

为了处理某含有较低毒性的固化铬渣,首先通过超声破解的方法浸出固化铬渣中的六价铬,再利用水合肼对浸出液中的六价铬进行还原处理,并探讨多种因素对六价铬还原的影响。结果表明：超声处理5 h可以使大部分的六价铬从固化铬渣中浸出;在碱性范围内,投料比、反应温度、反应时间及pH对六价铬的还原影响显著。反应的最佳实验条件为：反应温度为60 ℃、浸出液的pH为8.5、n（水合肼）∶ n（六价铬）=130∶1、反应时间为30　min。在最佳实验条件下,六价铬的去除率达到了98.6%,六价铬的最终质量浓度为0.09 mg/L。     

Application of an improved testing device for the study of alumina dissolution in silicate slag

This study entailed a dissolution study of alumina fine ceramics in a CaO–Al₂O₃–SiO₂–MgO silicate slag system with a CaO/SiO₂ weight ratio of 0.65. Finger-test experiments with several corrosion steps were carried out in a contemporary continuous wear testing device at 1450, 1500, and 1550 °C with 200 rpm. The corroded sample profiles were measured using a high-resolution laser scanner, and the processed measurement data were used to extract the dissolution parameters (i.e. corroded volume, surface area, mean radius, tip radius and immersion length). The diffusivity determination method using Sherwood relations was developed for the dynamic finger-test setup. The diffusivities for all corrosion steps were determined from these dissolution parameters, and those obtained from the Sherwood relations were compared with the ones received by a simulation approach that includes deviations from the cylindrical shape. The results obtained using Sherwood relations are sufficiently accurate in several cases.     

f-CaO含量对钢渣高温蒸压粉化性能影响

钢渣中f-CaO含量高是造成其长期稳定性差的主要原因之一,因此研究不同f-CaO含量钢渣的高温蒸压粉化性能对钢渣的稳定化处理及综合利用具有十分重要的意义。本文通过采用化学成分、岩相特征及X射线衍射等检测手段,研究不同f-CaO含量钢渣的高温蒸压粉化性能、显微结构及物相成分的变化情况,结果表明：在温度1 000 ℃、蒸气压力0.4 MPa、蒸压时间4 h的条件下,随着钢渣中f-CaO含量的升高,钢渣的高温蒸压粉化率不断提高;钢渣中f-CaO含量≥4.0%时,钢渣的蒸压粉化率可达到80%以上。通过钢渣高温蒸压粉化处理,使不同f-CaO含量的钢渣实现了稳定化处理。     

不同煤熔渣对水煤浆加压气化炉用高铬砖的侵蚀

为研究不同煤熔渣对高铬砖的侵蚀机制,选取4种物理化学性能差异较大的典型气化炉用后煤熔渣,采用化学分析、XRD、SEM及EDS等研究了不同煤熔渣的性能及其对w(Cr2O3)≥90%的高铬砖的侵蚀、渗透情况。结果表明:气化炉中煤熔渣主要由SiO2、CaO、Al2O3、Fe2O3、MgO组成,但不同煤熔渣的化学组成差异较大,矿物组成及熔融特性温度也不同;在相同条件下,高铬砖侵蚀的主要影响因素是温度和熔渣的化学组成,随温度升高,煤熔渣对高铬砖的侵蚀急速加剧;煤渣中的熔融指数较低时,煤熔渣对高铬砖的侵蚀渗透较为严重;煤熔渣中低熔点相向材料内部渗透、渣中SiO2等对材料中ZrO2等的反应溶解是造成高铬砖失效的直接原因;高铬砖表面形成镁铝铬铁复合尖晶石致密层可以有效降低高铬砖的侵蚀程度。