Optimization of a continuous ultrasound assisted oxidative desulfurization (UAOD) process of diesel using response surface methodology (RSM) considering operating cost

A continuous-flow ultrasound-assisted oxidative desulfurization(UAOD) of partially hydro-treated diesel has been investigated using hydrogen peroxide-formic acid as simple and easy to apply oxidation system. The effects of different operating parameters of oxidation stage including residence time(2–24 min), formic acid to sulfur molar ratio(10–150), and oxidant to sulfur molar ratio(5–35) on the sulfur removal have been studied using response surface methodology(RSM) based on Box–Behnken design. Considering the operating costs of the continuous-flow oxidation stage including chemical and electrical energy consumption, the appropriate values of operating parameters were selected as follows: residence time of 16 min, the formic acid to sulfur molar ratio of 54.47, and the oxidant to sulfur molar ratio of 8.24. In these conditions, the sulfur removal and the volume ratio of the hydrocarbon phase to the aqueous phase were 86.90% and 4.34, respectively. By drastic reduction in the chemical consumption in the oxidation stage, the volume ratio of the hydrocarbon phase to the aqueous phase was increased up to 10. Therefore, the formic acid to sulfur molar ratio and the oxidant to sulfur molar ratio were obtained 23.64 and 3.58, respectively, which lead to sulfur removal of 84.38% with considerable improvements on the operating cost of oxidation stage in comparison with the previous works.     

Feasibility of CANON process for treating nitrogenous wastewater containing heavy metals

The appearance of heavy metals in wastewater brings a major burden to wastewater treatment plants, due to the high toxicity to microorganisms. Several commonly used heavy metals, including Zn(II), Cd(II), Hg(II), and Pb(II) were adopted to clear the individual and joint toxicity to the completely autotrophic nitrogen removal over nitrite (CANON) process in six sequencing batch reactors. The obtained results suggested that the nitrogen removal performances were transiently inhibited, but rapidly recovered. The restoration period under the stress of Hg(II) and Pb(II) was shorter than that under Zn(II), Cd(II), and the joint heavy metals. During the long-term exposure, Cd(II) in 1mg L⁻¹ slightly inhibited the nitrogen removal, while Zn(II), Hg(II), Pb(II), and mixture showed a negligible impact on CANON process. The defense of extracellular polymeric substances (EPS), the good adaptability of functional bacteria, and the inducement of resistant genera by heavy metals all contributed to the robustness and stability of CANON process. Therefore, it is feasible to treat nitrogenous wastewater containing low heavy metals using CANON process. © 2020 Society of Chemical Industry     

Evaluation of Transport Phenomena for Removing Vanadium from Petrochemical Industry Solid Waste

Transport phenomena are investigated which are involved in the electrokinetic remediation process used for removing vanadium from deactivated catalysts from oil catalytic cracking that are currently allotted to cement plants and class-I landfills. Variables such as the concentration of electrolyte, electric potential, and applied electric current were evaluated in order to determine the effects produced by electroosmosis, diffusion, hydraulic gradient, and electromigration on the removal of vanadium from the catalyst. It was observed that migration is the most relevant phenomenon in the remediation tests, and for the best remediation condition, the migratory flow accounted for about 87 % of the vanadium removal.     

A novel flow field with controllable pressure gradient to enhance mass transport and water removal of PEM fuel cells

An easily machined novel flow field with controllable pressure gradient across adjacent channels was designed and a two dimensional, across-the-channel, two-phase model was developed to study the gas transport and water removal of the novel configuration. The effect of channel-rib width ratio, GDL thickness and pressure gradient on the profiles of oxygen concentration and water saturation within the GDL were investigated. Special attention was paid to the mechanisms of the promoted mass transport and water removal rates under a pressure gradient. The model was validated by experiments with various channel-rib ratios and GDL thicknesses at different operating pressure. The results revealed that, oxygen concentration was increased, and the water saturation was reduced under the rib with a pressure gradient generated across the adjacent channels. The optimal pressure gradient is between 0.1 to 0.2 atm for the studied channel geometry and configuration. The mechanisms of the improved cell performance were elucidated.     

费托合成尾气脱碳工艺选择及试车问题分析与优化

综述了不同尾气脱碳工艺的优缺点及适用条件,指出热钾碱法是目前较适用于大型费托合成尾气中CO2脱除的方法。介绍了处理尾气规模为60万m3/h的某热钾碱脱碳工艺流程,针对该装置在投料试车过程中出现的再生系统能耗高、费托合成尾气水洗效果差、吸收塔填料易堵塞及再生气排放非甲烷总烃超标等问题,进行了原因分析,并提出了一系列工艺调整及设备改造措施。实际运行结果表明,所采取的优化措施能够有效解决上述问题。     

Polyacrylonitrile/α-Fe2O3 Hybrid Photocatalytic Composite Adsorbents for Enhanced Dye Removal

The potential of a novel α-Fe₂O₃/polyacrylonitrile (PAN) hybrid composite adsorbent to eliminate methylene blue (MB) from aqueous solution was evaluated. PAN was selected as the base composite. The presence of α-Fe₂O₃ as nanophotocatalyst on the surface of PAN introduced an efficient photocatalytic hybrid composite adsorbent for degrading MB. Effects of α-Fe₂O₃ nanopowder loading, pH, temperature, MB initial concentration, solar light, and contact time were investigated. Langmuir, Freundlich, and Temkin isotherms were applied to analyze the adsorption behavior. The Freundlich equation provided the best correlation with experimental data. Pseudo-first-order, pseudo-second-order, and intraparticle models were employed. Thermodynamic studies indicated an endotherm and spontaneous adsorption process in a defined temperature range.     

Electrospinning preparation and dye adsorption capacity of TiO2@Carbon flexible fiber

TiO₂@carbon flexible fiber was prepared by combining electrostatic spinning technology and hydrothermal synthesis method. The XRD, SEM, TEM and Zeta potential techniques were used to characterize the phase, microstructure and surface charge properties of the samples. The growth mechanism of TiO₂ nanoarray on carbon flexible fiber with different morphologies was studied, and the dye adsorption capacity of the samples was evaluated by methylene blue (MB) degradation effect. The results showed that proper doping amounts of TiO₂ particles improved the flexibility and the hydrophilic property of carbon fiber significantly, which was conducive to the deposition and growth of TiO₂ on the carbon fiber. With the increase of hydrothermal time, the TiO₂ nanoarray grew denser gradually along the [110] crystal surface. The negative charge on the surface of carbon fiber increased, which was benefited to the removal of MB. The dye adsorption capacity of TiO₂@carbon fiber was resulted from the synergistic effect of physical adsorption (carbon fiber) and photocatalysis (TiO₂) process.     

河流护岸多孔生态材料对水体中硝态氮去除试验

为进一步提升护岸材料对面源污染物的净化能力,采用骨料交联法制备了具有较高透水率的多孔生态砌块,研究骨料粒径与砌块透水率的关系,并采用动水挂膜法对不同透水率的生态砌块进行反硝化细菌表面负载,在此基础上,研究所制备的不同骨料粒径的生态砌块的透水率、比表面积等对水体中硝态氮去除率的耦合效应。结果表明:在相同孔隙率条件下生态砌块的透水率随比表面积的增加而降低,且随着骨料粒径的增大而提高;生态砌块对水体中硝态氮的去除率随透水率的增加呈现先增大再减小的趋势,其中骨料粒径为7~11 mm,透水率为6.6 m L/(s.cm~2)的多孔生态砌块对硝态氮的去除率可达90.3%。     

严重事故下吸湿性气溶胶的自然去除研究

反应堆发生严重事故时，堆芯释放出的吸湿性气溶胶会在潮湿的安全壳内增大，从而影响其自然去除过程。本文理论推导了吸湿性气溶胶的增大模型并通过多种方法对其进行了验证。模型计算结果表明，气溶胶的增大过程由于受到溶解度的限制而存在临界湿度值，在该临界值以下时气溶胶不发生吸湿，但这未被其他严重事故分析程序所考虑。同时，基于某三代先进压水堆的特定严重事故工况，本文分析了干颗粒半径及湿度对气溶胶的平衡半径和自然去除系数的影响。结果表明:气溶胶的自然去除系数随干颗粒半径的增大将先减小后增加，并在1 μm时达到最小值；相同湿度下，干颗粒半径对气溶胶半径的最大增大比例的影响不大；湿度的增加对不同干颗粒半径气溶胶去除系数的影响不同。      

渣油加氢催化剂的工业应用

考察了2种进口渣油加氢催化剂(RM系列和ICR系列)在中化泉州石化有限公司330万t/a渣油加氢装置上的工业应用情况。结果表明:2种渣油加氢催化剂均具有良好的加氢活性;在原料性质和操作条件相近的条件下,与ICR系列催化剂相比,RM系列催化剂的脱硫、脱残炭性能较优,脱金属性能略差,且RM前部反应器床层压差上升速率较慢。