SUPERCRITICAL EXTRACTION AND DESULPHURIZATION OF BEYPAZARI LIGNITE BY ETHYL ALCOHOL/NaOH TREATMENT 1. EFFECT OF ETHYL ALCOHOL/COAL RATIO AND NaOH

ABSTRACT

The solubilization and desulphurization of Beypazari lignite with supercritical ethyl alcohol/NaOH was investigated. Supercritical experiments of 60?minutes were done in microreactors of 15?ml at 245°C by changing the ethyl alcohol/coal ratio from 3 to 20 under a nitrogen atmosphere. As the ethyl alcohol/coal ratio was increased the yield of solubilization and desulphurization also increased. Higher yields of extraction in the case of ethyl alcohol/NaOH experiments may be due to the fact that alcohols can transfer hydrogen more easily in the presence of bases. The average molecular weights of liquid products obtained in experiments with ethylalcohol/coal ratios of 3,6 and 20 were 430,450 and 465, respectively. In experiments with ethylalcohol/NaOH system as the ethylalcohol/coal ratio was increased from 3 to 20 the sulphur content of the coal decreased to 0·75%. In experiments with greater ethylalcohol/coal ratios mercaptane type sulphur chemicals have been extracted,disulphides were missing in these extracts.     

Ion Chromatographic Determination of Free Cyanide in Different Classes of Bottled Natural Mineral Water Consumed in Turkey

An ion chromatographic method for the quantitative determination of free cyanide in bottled natural mineral waters were measured in terms of selectivity, linearity, the limit of detection, limit of quantification, repeatability, precision, and accuracy. Chromatographic separation of free cyanide ions was accomplished with an anion-exchange column and detected by pulsed amperometric detection with a silver working electrode. The method was found to be selective, linear (r² = 0.999) at a concentration range of 0.5 to 134 μg L^?1, precise, and accurate. Recovery values of free cyanide in all classes of natural mineral water varied from 65.9 ± 1.6 to 95.2 ± 0.7 at different spiking levels (5–70 μg L^?1). Parameters (total dissolved solids, mineral interferences, and added sodium hydroxide) affecting the recovery values were studied in this project. The limit of detection and limit of quantification were found to be 0.295 and 0.983 μg L^?1, respectively. The proposed method was applied to 27 different brands of commercially available bottled natural mineral water products sold in Turkish markets. These natural mineral waters were classified as: (i) very low mineral concentration, (ii) low mineral concentration, (iii) intermediate mineral concentration, and (iv) high mineral concentration based on their total dissolved solids contents according to European Union Directive (Directive 80/777/EEC). Levels of free cyanide residues in the samples ranged from > limit of detection to 6.12 μg L^?1. The highest average concentration of free cyanide residues was found in the class of “high mineral concentration waters.” However, the determined free cyanide values in all of the tested natural mineral water samples were found to be within the limits of European Union legislation.     

Influence of surfactants on flocculation and dewatering of kaolin suspensions by cationic polyacrylamide (PAM-C) flocculant

This paper reports the result of studies on flocculation and dewatering of kaolin suspensions by cationic polyacrylamide (PAM-C) flocculants in presence of surfactants. The surfactants used were namely anionic sodium dodecyl sulphate (SDS), cationic cetyl trimethyl ammonium bromide (CTAB) and non-ionic TritonX 100, which is a polyoxyethylenic ether compound. The unflocculated kaolin has a very slow settling rate of about 0.03 cm/s and can be improved by more than ten times using PAM-C as a flocculating agent. PAM-C adsorbs on kaolin primarily through electrostatic attraction and the flocculation is governed mainly by charge neutralisation and bridging. Partial pre-coating of kaolin with all three surfactants leads to both physical adsorption as well as chemisorption at PAM-C. Pretreating the kaolin with surfactants can further increase or decrease settling rate depending on the type of surfactant used. However, the flocs thus formed shows better filtration and dewatering behaviour estimated in terms of reduction in specific resistance to filtration (SRF) and cake moisture. The minimum SRF occurs under conditions corresponding to far lower adsorption of PAM-C than that for best flocculation. Simultaneous addition of PAM-C and each of the three surfactants decreases settling rate and sediment volume markedly and does not reduce SRF any further but they all reduce cake moisture substantially. The reduction in cake moisture for different PAM-C: surfactant mixture is in the following order: PAM-C: SDS (1:1)>PAM-C: TX 100(1:1)>PAM-C: CTAB(1:1). Low cake moisture in comparison with PAM-C alone, may be a result of reduction in entrapment of excess water in the smaller flocs formed by simultaneous addition with surfactants and to some extent due to hydrophobicity caused by adsorption of surfactants.     

Effects of Nanoparticles on Film Properties of Waterborne Acrylic Emulsions

Waterborne acrylic emulsion was obtained by using methyl methacrylate, ethyl and butyl acrylate monomers. Emulsions containing nanoparticles were prepared by blending the stable dispersions containing SiO₂ or MMT nanoparticles. The films were prepared from emulsions and coating tests were applied. The physical properties of prepared emulsions are better than the commercial emulsions. The addition of the nanoparticles especially SiO₂ have positive effect on the resistance to environmental conditions of emulsions. Waterborne acrylic emulsions containing nanoparticles prepared in this study can be used in the manufacturing of the semi-lustrous emulsion type nano paint with low cost, high performance and environmentally friendly.     

Experimentally and numerically investigating cell performance and localized characteristics for a high-temperature proton exchange membrane fuel cell

This paper is to experimentally and numerically investigate the cell performance and the localized characteristics associated with a high-temperature proton exchange membrane fuel cell (PEMFC). Three experiments are carried out in order to study the performance of the PEMFC with different operating conditions and to validate the numerical simulation model. The model proposed herein is a three-dimensional (3-D) computational fluid dynamics (CFD) non-isothermal model that essentially consists of thermal–hydraulic equations and electrochemical model. The performance curves of the PEMFC predicted by the present model agree with the experimental measured data. In addition, both the experiments and the predictions precisely demonstrate the enhanced effects of inlet gas temperature and system pressure on the PEMFC performance. Based on the simulation results, the localized characteristics within a PEMFC can be reasonably captured. These parameters include the fuel gas distribution, liquid water saturation distribution, membrane conductivity distribution, temperature variation, and current density distribution etc. As the PEMFC is operated at the higher current density, the fuel gas would be insufficiently supplied to the catalyst layer, consequently causing the decline in the generation of power density. This phenomenon is so called mass transfer limitation, which can be precisely simulated by the present CFD model.     

Flame stretch analysis in diffusion flames with inert gas

1niwtonInveshgations to enhance combushon efficiencyhave been irnportan in the past decad. Most of theimProvementS were coneennd on bog thendulent fluctUations and flow intensihes. The jettodetboinging setup is widely used in rocke engines withseif ignition proPellantS. The pUrPOse of thes reseaxC istO examine the imPinging effeCt on the jet-imPingementdiffesion flame.Two asPeCs of the twinging flame, jetboingeInen heating and combushon enhaneement havebeen inveshgatal. Milson and Chig…     

Suggested methods for optimum rotative motion of point attack type drag tools in terms of skew angles

ABSTRACT

Rotation of point attack picks in their tool holders is of crucial importance for an efficient performance of machines used for tunnelling and underground excavations of rocks and coal. With current machines, skew angle has been extensively employed to achieve tool rotation. There has, however, been no common definition and suggestion on application of skew angles, due to the differences between the results of research investigations conducted in this field. This paper sets out the findings of long-term practical research during tunnelling and underground excavation operations with roadheaders and drum shearers in order to bring a common understanding in rotation of point attack picks. Mechanism of tool rotation was discussed, and a number of formulas were derived and suggested for optimum cutting conditions for roadheaders and mechanical miners, respectively. The results showed that with drum shearers tool rotation is possible without skew angles, due to the asymmetry between adjacent grooves which generates sideways forces inducing rotative movement of picks. Skew angles were, however, found to be a must for roadheaders in consideration with tool holder damage which was significantly influenced by different settings of skew angles. Furthermore, point attack picks with small-diameter shanks were found to suffer from shank breakage resulting from high values of tool forces, when fitted on the nose portion of roadheaders cutting heads.     

Effects of magnesium and chromium addition on stability,activity and structure of copper-based methanol synthesis catalysts

Cu/ZnO/Al₂O₃-based catalysts for methanol synthesis are prepared through co-precipitation by addition of Mg and Cr. Precursors are characterized by XRD and Air-TGA. Catalysts, calcined at 450 °C, are examined by XRD and BET. Reduction characteristics of the catalysts are analyzed via H₂-TPR and H₂-TGA. Surface acidity of the catalysts is determined by TPAD-TGA. Addition of Mg and Cr causes formation of smaller CuO crystallite size, and increases surface area of catalysts by improving dispersion of CuO. Cr also improves stability of the catalysts against ambient conditions and prolongs their shelf life. The catalyst containing 6.4 mol % Cr has a methanol selectivity of 83.5% and a catalytic activity of 14.2 g methanol production which is the highest among other synthesized catalysts. High Cr loadings (32 mol %) reduce the catalytic activity. Cr containing catalysts continue to produce the highest amounts of methanol as compared with the catalysts without Cr where Cr prevents deactivation and sintering.     

Synthesis and characterization of whitlockite from sea urchin skeleton and investigation of antibacterial activity

In the present study, undoped whitlockite and ZnO doped-Whitlockite, which is the second most abundant inorganic material in bone structure, were synthesized from sea urchin skeleton. The obtained bioceramic materials were characterized by XRD, FT-IR, and SEM and their antibacterial activities were determined using the inhibition zone diameters of Escherichia coli and Pseudomonas aeruginosa as gram negative bacteria and Staphylococcus aureus as gram positive bacterium after 24 h incubation. The characterization studies showed that nano size homogenous biocereamic whitlockite (Ca_2.86Mg_0.14(PO₄)₂) was synthesized from the sea urchin skeleton. After dopping process, the main structure of the whitlockite keeps stable, showing a dopping concentration-independent character. On the other hand, the peaks belonging to ZnO were started to seen in the XRD pattern with increasing the level of ZnO-concentration (after 7 %). All experimental results point out that the obtained whitlockites are viable nominate candidates for bioceramic materials and the results of antibacterial sensitivity prove the inhibitory effect towards Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus for ZnO-doped-whitlockite.