Nov 2016, Volume 10 Issue 4

Cover illustration

  • (Renxing Wang, Zhenyu Liu, Leiming Ji, Xiaojin Guo, Xi Lin, Junfei Wu, Qingya Liu, pp. 517-525)
    Production of calcium carbide (CaC2) from coal-derived coke and lime is still an important coal-to-chemical process today. The autothermal technologies with pulverized coke and lime or pelletized feed have been developed for this process in recent years to replace the traditional electric arc technology due to reduction in energy consumption and CO2 emission. Reaction kinetics of these feeds required for simulation and design of reactors and process are limited and contradictive in the literature. Based on the reaction data obtained by TGA at 17001850°C applicable to industry, the kinetic model is determined with the isoconversional and model-fitting methods. It is found that the process is mainly influenced by heat transfer from the environment to the feed. The larger geometrical surface area of the powder feed yields a higher CaC2 formation rate in comparison with the pelletized feed. The reaction kinetics of both feeds can be described by the contracting volume model. The apparent activation energy and the pre-exponential factor of the pulverized feed are 353 kJ∙mol−1 and 5.9 × 107 min−1, respectively, while those of the pelletized feed are 305 kJ∙mol−1 and 3.6×106 min−1, respectively. [Detail] ...

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    Andrew Michelmore, Jason D. Whittle, James W. Bradley, Robert D. Short

    Functionalising surfaces using polymeric thin films is an industrially important field. One technique for achieving nanoscale, controlled surface functionalization is plasma deposition. Plasma deposition has advantages over other surface engineering processes, including that it is solvent free, substrate and geometry independent, and the surface properties of the film can be designed by judicious choice of precursor and plasma conditions. Despite the utility of this method, the mechanisms of plasma polymer growth are generally unknown, and are usually described by chemical (i.e., radical) pathways. In this review, we aim to show that plasma physics drives the chemistry of the plasma phase, and surface-plasma interactions. For example, we show that ionic species can react in the plasma to form larger ions, and also arrive at surfaces with energies greater than 1000 kJ?mol1 (>10 eV) and thus facilitate surface reactions that have not been taken into account previously. Thus, improving thin film deposition processes requires an understanding of both physical and chemical processes in plasma.

    Anan Wang,Helen H. Lou,Daniel Chen,Anfeng Yu,Wenyi Dang,Xianchang Li,Christopher Martin,Vijaya Damodara,Ajit Patki

    Industrial Flares are important safety devices to burn off the unwanted gas during process startup, shutdown, or upset. However, flaring, especially the associated smoke, is a symbol of emissions from refineries, oil gas fields, and chemical processing plants. How to simultaneously achieve high combustion efficiency (CE) and low soot emission is an important issue. Soot emissions are influenced by many factors. Flare operators tend to over-steam or over-air to suppress smoke, which results in low CE. How to achieve optimal flare performance remains a question to the industry and the regulatory agencies. In this paper, regulations in the US regarding flaring were reviewed. In order to determine the optimal operating window for the flare, different combustion mechanisms related to soot emissions were summarized. A new combustion mechanism (Vsoot) for predicting soot emissions was developed and validated against experimental data. Computational fluid dynamic (CFD) models combined with Vsoot combustion mechanism were developed to simulate the flaring events. It was observed that simulation results agree well with experimental data.

    Adrian W. K. Law,Chunyan Tang

    Industrial water treatment and industrial marine outfalls both function together to reduce the pollutant concentrations in the effluent and mitigate the potential impact on the environment. The former uses environmental treatment technology with energy and material cost considerations, while the latter utilizes the natural assimilation potential of the coastal water environment achievable at the outfall location. Because of their synergistic nature, marine outfalls are now commonly used for the disposal of partially treated domestic and industrial effluents in many coastal cities around the world, with many successful examples of low and acceptable risks to the environment. The objective of this paper is to review their balance from both environmental and economic considerations. We also discuss the end-of-the-pipe and mixing zone approaches for industrial effluents, and give some recommendations particularly for developing countries. Finally, we emphasize that a compulsory and vigorous monitoring program is essential regardless of how the balance is achieved.

    Guilan Chen, Xingfu Song, Shuying Sun, Yanxia Xu, Jianguo Yu

    The absorption of CO2 in insoluble organic amine is crucial for understanding the mechanism of coupled reaction-extraction-crystallization process between aqueous chloride and CO2. In this study, the solubility and diffusivity of CO2 in n-butanol+ N235 system were measured and reported. The absorption of CO2 in the system is a physical absorption behavior and the solubility of CO2 decreases with the increase of the mass fraction of N235. The diffusivity of CO2 increases firstly and then decreases with the increase in the mass fraction of N235. Moreover, the absorption mechanism of CO2 in the coupled reaction-extraction-crystallization process was investigated and identified by experiments. The results indicated that in the coupled reaction-extraction-crystallization process, CO2 is absorbed by the aqueous phase rather than by the organic phase and further transferred into the aqueous phase.

    Xue Zou,Jin Li

    Membrane fouling has been investigated by using a polysulfone ultrafiltration membrane with the molecular weight cutoff of 20 kDa to treat crushed coal pressurized gasification wastewater. Under the conditions of different feed pressures, the permeate flux declines and rejection coefficients of pollutants referring to three parameters (total organic carbon (TOC), chroma and turbidity) were studied. The membrane fouling mechanism was simulated with three classical membrane fouling models. The membrane image and pollutants were analyzed by scanning electron microscopy and gas chromatography-mass spectrography (GC-MS). The results indicate that the permeate flux decreases with volume reduction factor before reaching a constant value. The rejection coefficients were also measured: fTOC = 70.5%, fC = 84.9% and fT = 91%. Further analysis shows that the higher the feed pressure is, the sooner the permeate flux reaches constant value and the more sharply the permeate flux declines. Constant flux indicates a nonlinear growth with feed pressure (PF): when PF equals 1.2 bar, the mark for the critical flux, slight membrane fouling occurs; when PF exceeds 1.2 bar, cake layer pollution aggravates. Also the rejection coefficients of global pollutant increases slightly with PF, suggesting the possibility of cake compression when PF exceeds 1.2 bar. Through regression analysis, the fouling of polysulfone ultrafiltration membrane could be fitted very well by cake filtration model. The membrane pollutants were identified as phthalate esters and long-chain alkenes by GC-MS, and a certain amount of inorganic pollutants by X-ray photoelectron spectroscopy.

    Suvidha Gupta,R. A. Pandey,Sanjay B. Pawar

    The Chlorella microalgae were mixotrophically cultivated in an unsterilized and unfiltered raw food-processing industrial wastewater. Both inorganic carbon (CO2-air) and organic carbon (wastewater) were provided simultaneously for microalgae growth. The aim of the study is to find out the utilization rates of total organic carbon (TOC) and chemical oxygen demand (COD) under mixotrophic conditions for a given waste water. About 90% reduction in TOC and COD were obtained for all dilutions of wastewater. Over 60% of nitrate and 40% of phosphate were consumed by microalgae from concentrated raw wastewater. This study shows that microalgae can use both organic and inorganic sources of carbon in more or less quantity under mixotrophic conditions. The growth of microalgae in food-processing industrial wastewater with all studied dilution factors, viz. zero (raw), 1.6 (dilution A), and 5 (dilution B) suggests that the freshwater requirement could be reduced substantially (20%–60%). The degradation kinetics also suggests that the microalgae cultivation on a high COD wastewater is feasible and scalable.

    Yuqi Chen,Yakai Feng,Jingqi Zhao,Jingbo Shen,Menghuang Feng

    Oil bleed is a serious problem in elastomeric thermal silicone conductive pads. The components of the oil bleed and the effect of the silicone chemical parameters on the amount of oil bleed have been determined. The main components of oil bleeds are the uncrosslinked silicones in the cured resins, which include the unreacted silicone materials and the macromolecular substances produced by the hydrosilylation reaction. Cured resins with a high crosslinking density and a high molecular weight of vinyl silicone residues had a lower amount of oil bleed. In addition, a low Si-H content also reduced the amount of oil bleed.

    Renxing Wang,Zhenyu Liu,Leiming Ji,Xiaojin Guo,Xi Lin,Junfei Wu,Qingya Liu

    The production of CaC2 from coke/lime powders and compressed powder pellets are low cost and fast processes. A number of studies have reported the reaction kinetics of these reactions but they are still not well understood and the proposed kinetic models are not comparable due to differences in the reaction conditions. Therefore the reaction behavior of CaO/C powders (0.074 mm) and cubes (5 mm × 5 mm × (4.6–5.1) mm) compressed from a mixture of powders have been studied using thermal gravimetric analysis (TGA) at 1700– 1850 °C. Kinetic models were obtained from the TGA data using isoconversional and model-fitting methods. The reaction rates for the compressed feeds were lower than those for the powder feeds. This is due to the reduced surface area of the compressed samples which inhibits heat transfer from the surrounding environment (or the heating source) to the sample. The compression pressure had little influence on the reaction rate. The reaction kinetics of both the powder and the compressed feeds can be described by the contracting volume model f(α) = 3(1−α)2/3, where α is the conversion rate of reactant. The apparent activation energy and pre-exponential factor of the powder feed were estimated to 346–354 kJ?mol1 and 5.9 × 107 min1, respectively, whereas those of the compressed feed were 305–327 kJ?mol1 and 3.6 × 106 min1, respectively.

    Boreum Lee,Sunggeun Lee,Ho Young Jung,Shin-Kun Ryi,Hankwon Lim

    New and efficient reactor systems were proposed to treat perfluorinated compounds via catalytic decomposition. One system has a single reactor (S-1), and another has a series of reactors (S-2). Both systems are capable of producing a valuable CaF2 and eliminating toxic HF effluent and their feasibility was studied at various temperatures with a commercial process simulator, Aspen HYSYS®. They are better than the conventional system, and S-2 is better than S-1 in terms of CaF2 production, a required heat for the system, natural gas usage and CO2 emissions in a boiler, and energy consumption. Based on process simulation results, preliminary economic analysis shows that cost savings of 12.37% and 13.55% were obtained in S-2 at 589.6 and 621.4 °C compared to S-1 at 700 and 750 °C, respectively, for the same amount of CaF2 production.

    Yinlong Hu,Shuang Zheng,Fumin Zhang

    Heterogeneous catalysts with convenient recyclability and reusability are vitally important to reduce the cost of catalysts as well as to avoid complex separation and recovery operations. In this regard, magnetic MIL-100(Fe)@SiO2@Fe3O4 microspheres with a novel core-shell structure were fabricated by the in-situ self-assembly of a metal-organic MIL-100(Fe) framework around pre-synthesized magnetic SiO2@Fe3O4 particles under relatively mild and environmentally benign conditions. The catalytic activity of the MIL-100(Fe)@SiO2@Fe3O4 catalyst was tested for the liquid-phase acetalization of benzaldehyde and glycol. The MIL-100(Fe)@SiO2@Fe3O4 catalyst has a significant amount of accessible Lewis acid sites and therefore exhibited good acetalization catalytic activity. Moreover, due to its superparamagnetism properties, the heterogeneous MIL-100(Fe)@SiO2@Fe3O4 catalyst can be easily isolated from the reaction system within a few seconds by simply using an external magnet. The catalyst could then be reused at least eight times without significant loss in catalytic efficiency.

    Mani Abirami, Krishnan Kannabiran

    We present the microbial green synthesis of silver nanoparticles (NPs) by Streptomyces ghanaensis VITHM1 strain (MTCC No. 12465). The secondary metabolites in the cell free supernatant of this bacterium when incubated with 1 mmol/L AgNO3, mediated the biological synthesis of AgNPs. The synthesized AgNPs were characterized by UV-visible spectrum, X-ray diffraction (XRD), atomic force microscope, scanning electron microscopy equipped with energy dispersive spectroscopy, transmission electron microscopy, FT-IR spectroscopy, dynamic light scattering and zeta potential. They were highly stable and, spherical in shape with the average size of 30?50 nm. The secondary metabolites involved in the formation of AgNPs were identified gas chromatography-mass spectrography. The 3D structure of the unit cell of the synthesized AgNPs was determined using XRD data base. The synthesized AgNPs exhibited significant antibacterial activity against tested bacterial pathogens, and did not show haemolysis on human red blood cells. This green synthesis could provide a new platform to explore and use AgNPs as antibacterial therapeutic agents.

    Ziyan Li,Yaodong Huang,Dongli Fan,Huimin Li,Shuxue Liu,Luyuan Wang

    Two series of 5-iodo-1,2,3-triazole derivatives containing azobenzene group(s) were synthesized and their gelling properties were tested. Those containing two azobenzene groups (B series) have better gelation performance than those containing one azobenzene group (A series). The microstructure of organogels and the driving force of gelation were investigated by scanning electron microscopy and 1H NMR, respectively. It was found that π-π stacking, van der Waals interaction, and dipole-dipole interaction were the main forces of gelation. All the tested organogels are photoresponsive and those from B series are smarter than that from A series. Henry δp-δh diagrams of compounds A1, A2, and B2 were constructed on the basis of their gelation performance and the Hansen solubility parameters of related solvents. The constructed Henry δp-δh diagrams can be used to estimate the behavior of three compounds in any untested solvent.

    Baicang Liu,Chen Chen,Pingju Zhao,Tong Li,Caihong Liu,Qingyuan Wang,Yongsheng Chen,John Crittenden

    To advance commercial application of forward osmosis (FO), we investigated the effects of two additives on the performance of polysulfone (PSf) based FO membranes: one is poly(ethylene glycol) (PEG), and another is PSf grafted with PEG methyl ether methacrylate (PSf-g-PEGMA). PSf blended with PEG or PSf-g-PEGMA was used to form a substrate layer, and then polyamide was formed on a support layer by interfacial polymerization. In this study, NaCl (1 mol?L−1) and deionized water were used as the draw solution and the feed solution, respectively. With the increase of PEG content from 0 to 15 wt-%, FO water flux declined by 23.4% to 59.3% compared to a PSf TFC FO membrane. With the increase of PSf-g-PEGMA from 0 to 15 wt-%, the membrane flux showed almost no change at first and then declined by about 52.0% and 50.4%. The PSf with 5 wt-% PSf-g-PEGMA FO membrane showed a higher pure water flux of 8.74 L?m−2?h−1 than the commercial HTI membranes (6–8 L?m−2?h−1) under the FO mode. Our study suggests that hydrophobic interface is very important for the formation of polyamide, and a small amount of PSf-g-PEGMA can maintain a good condition for the formation of polyamide and reduce internal concentration polarization.