Energy-efficient coal dewatering using liquefied dimethyl ether

In this study, we dewatered sub-bituminous coal mined in Warra, Indonesia, by using liquefied dimethyl ether (DME); no heating was required in this dewatering process. We achieved this dewatering both in a laboratory-scale experiment and using previously developed bench-scale equipment. We also examined the properties of the coal before and after dewatering and measured the amount of energy required by the equipment. We found that the maximum water extraction efficiency of liquefied DME was 98.3%. Further, the properties of the coal did not change after the dewatering treatment. The wastewater obtained by dewatering can be treated by existing wastewater treatment technologies. The energy consumed by the bench-scale equipment was 2069 kJ/kg-water; thus, this dewatering process using liquefied DME was confirmed to be effective and energy efficient.     

Optimization of rubber seed oil extraction using liquefied dimethyl ether

The objective of this study was to find the optimal condition for the extraction of rubber seed oil (RSO), using liquefied dimethyl ether (DME). Response surface methodology with a spherical central composite design model was employed to determine the optimal extraction condition, consisting of a seed moisture content (%wt), a solvent to solid ratio (g/g), and an extraction temperature (°C). A quadratic regression equation suggested the optimal extraction condition was a moisture content of 56.4%wt, a solvent to solid ratio of 6.7 (g/g), and a temperature of 33.3?°C. At this condition, the RSO yield predicted by the model gave a slight deviation of 0.68% from the experimentally validated results (41.48 versus 41.20%). RSO has a kinematic viscosity of 36.8 cSt, an acid value of 10.7 KOH/g oil, a fatty acid content of 5.1% and an unsaturated fatty acid content of 80%, resulting in the potential production of biodiesel, biolubricants, and biodegradable plastics.     

二甲醚的制备与应用前景

综述了二甲醚的性质、制备方法、应用前景，比较了二甲醚制备方法的优缺点，其中，一步法生产二甲醚具有较高的经济价值。二甲醚作为一种重要的清洁能源和环境友好产品，其在车用燃料、民用燃料、化工原料方面的应用研究越来越受到重视，特别是作为燃料电池的燃料有着广阔的发展前景。     

Experimental study on the hazards of the jet diffusion flame of liquefied dimethyl ether

Dimethyl ether (DME) has been considered as a substitute for diesel fuel because it has a low auto-ignition temperature and produces less NO_x, SO_x, and particulate matter. However, the introduction of DME vehicles needs widely available DME supply stations. Moreover, the preparation of safety regulations for DME supply stations is very important, and so safety data is needed. Therefore, the present paper reports the hazards of the DME jet diffusion flame, which is one of several hazardous properties of DME, by studying the results of leaking gas and liquid DME. DME jets were released horizontally from circular nozzles whose diameters were 0.2, 0.4, 0.8 and 2 mm, and the release pressure was varied from the saturated vapor pressure to 2 MPa. When gaseous DME was released at the saturated vapor pressure, the flame was blown out. However, when liquefied DME was released, the flame formed. We obtained the experimental equations for estimating the scale and thermal hazards of DME diffusion flames.     

煤制二甲醚的生产与应用

介绍了煤制二甲醚的应用价值及其作为车用燃料替代能源的前景和可行性;重点分析了甲醇气相催化脱水法、甲醇液相脱水法、合成气直接合成法、二氧化碳加氢直接合成法等煤制二甲醚生产技术;提出了二甲醚工业发展存在的问题。     

甲醇及二甲醚的生产现状和发展前景

介绍了甲醇及二甲醚的生产现状和发展前景,叙述了二甲醚的制备方法及用途。     

Spent green tea leaves for decolourisation of raw textile industry wastewater

True colour measurements of wastewater samples, in terms of American Dye Manufacturers' Institute values, were used to evaluate the effectiveness of decolourisation of textile wastewater using spent green tea leaf powder waste. Raw wastewater samples with a true colour of 868 ADMI were used in the batch adsorption experiments. Results revealed that the true colour removal efficiency of the raw textile wastewater was high in acidic solution and at high temperature, indicating an endothermic nature of the system. The major functional groups of the green tea leaf powder waste involved in adsorption were identified by Fourier Transform‐infrared spectroscopy analysis. Adsorption kinetic data were modelled using the modified Freundlich and intraparticle diffusion kinetics equations. Fitting results of the Langmuir adsorption isotherm showed that the adsorption capacity of the green tea leaf powder waste was 775 ADMI g^?1, which is higher than that of powder activated carbon (526 ADMI g^?1). The low activation energy values (13.9 kJ mol^?1) suggested that adsorption was governed by a diffusion process and the reaction involved a physisorption mechanism. From the perspectives of waste utilisation, remarkable colour adsorption capacity and inexpensive and abundant availability, green tea leaf waste is an attractive alternative for decolourisaton of textile wastewater. Because high temperature favours colour removal, green tea leaf powder can be directly applied in raw textile wastewater treatment.     

A pathway for biosynthesis of divinyl ether fatty acids in green leaves

[1-¹⁴C]α-Linolenic acid was incubated with a particulate fraction of homogenate of leaves of the meadow buttercup (Ranunculus acris L.). The main product was a divinyl ether fatty acid, which was identified as 12-[1′(Z),3′(Z)-hexadienyloxy]-9(Z), 11(E)-dodecadienoic acid. Addition of glutathione peroxidase and reduced glutathione to incubations of α-linolenic acid almost completely suppressed formation of the divinyl ether acid and resulted in the appearance of 13(S)-hydroxy-9(Z), 11(E), 15(Z)-octadecatrienoic acid as the main product. This result, together with the finding that 13(S)-hydroperoxy-9(Z), 11(E), 15(Z)-octadecatrienoic acid served as an efficient precursor of the divinyl ether fatty acid, indicated that divinyl ether biosynthesis in leaves of R. acris occurred by a two-step pathway involving an ω6-lipoxygenase and a divinyl ether synthase. Incubations of isomeric hydroperoxides derived from α-linolenic and linoleic acids with the enzyme preparation from R. acris showed that 13(S)-hydroperoxy-9(Z), 11(E)-octadecadienoic acid was transformed into the divinyl ether 12-[1′(Z)-hexenyloxy]-9(Z), 11(E)-dodecadienoic acid. In contrast, neither the 9(S)-hydroperoxides of linoleic or α-linolenic acids nor the 13(R)-hydroperoxide of α-linolenic acid served as precursors of divinyl ethers.     

Modeling for the efficient separation of bio-active catechins from green tea leaves

Catechins are important bio-actives for the prevention of free radical induced diseases such as cancer, autoimmune disorders, aging etc. The extraction and recovery of catechins from their most abundant source, green tea leaves employ specific extractants (tributyl phosphate, TBP) in solvent (n-decane) for higher selectivity, and ethanol as extracting and recovery agents, respectively. The yields of extraction and recovery of catechins vary nonlinearly with the various process variables. Consequently, the influences of the variables on the yields are found out and satisfactory models (R² = 0.9866 and 0.9993 for extraction and recovery, respectively) are predicted through the Artificial Neural Network (ANN).     

二甲醚的开发与应用

1生产工艺二甲醚生产工艺有一步法和二步法两种,所谓一步法就是利用CO与H2直接合成;二步法则用甲醇脱水而制得。一步法工艺较复杂,但能耗、成本低,是当今世界上最先进的工艺技术。二步法工艺较简单,适合于自产甲醇的工厂,不仅投资少,且使甲醇增值,还可以简化二甲醚生产。1．　1一步法在220 ℃、有催化剂存在的条件下,由CO与H２直接反应生成二甲醚。杭州大学催化剂研究所已成功开发了由CO与H２直接合成二甲醚所用的催化剂,选择性几乎达100%,CO转化率在85%以上。目前我国正在合成氨厂进行该工艺的千吨级工业放大试验。1．　2…     

二甲醚氧化反应及其添加剂效应

采用加速量热仪（ARC）测定了二甲醚（DME）氧化反应温度变化和活化能（Ea）,考察了添加剂对DME热稳定性效应,分析热分解产物,探讨氧化反应机理. 结果表明,DME热氧化反应初始温度（To）为120 ℃,反应活化能Ea=167.3 kJ•mol-1.氧的存在是导致DME热稳定性下降重要因素,在氧化反应体系中添加Fe、Fe2O3、Al等时, To和Ea值减小,它们有促进氧化反应作用,特别是有过氧化物存在下,由于自由基的引发,显著降低DME热反应初始温度和反应活化能,抗氧剂能提高热稳定性.     

二甲醚的工业生产及开发

简述了二甲醚的工业生产方法及工艺特点,并指出了二甲醚的开发前景。     

A novel synthesis of diesel fuel additives from dimethyl ether using dielectric barrier discharges

A diesel fuel additive has been synthesized from conversion of dimethyl ether (DME) using dielectric barrier discharge (DBD) plasma at atmospheric pressure and low temperatures. A high conversion of DME has been achieved. The product of such conversion is a mixture of hydrocarbons and oxygenates that can be used as high-performance diesel fuel additives. The maximum conversion of DME reached 47.2% with a selectivity of liquid product (a mixture of dimethoxy-containing hydrocarbons) more than 39.0% at 120°C and a 30 ml/min flow rate of DME.     

聚甲氧基二甲醚合成反应动力学研究进展

聚甲氧基二甲醚（PODE_n）作为一种潜在的柴油调和组分,能够有效减少柴油燃烧不充分所带来的污染排放。但是,由于反应器放大设计和操作存在技术瓶颈,现阶段国内外尚无达到规模化生产的运行装置。本文以反应器的模型化设计为最终目标,介绍了不同PODE_n合成工艺的反应动力学研究现状,总结了合成工艺中亟待解决的问题。分析表明,水对反应速率存在影响并且改变PODE_n的产品分布,而以甲缩醛为端基源的反应在无水参与下副产物少,不仅降低产品的分离难度,还可极大简化动力学模型。同时,简述了合成反应链增长机制的研究进展,指出在未来研究中探明PODE_n合成反应机理对普适动力学模型的建立至关重要,从而应用于工艺优化和反应器放大设计。     

Thermophysical properties of dimethyl ether at near- and supercritical pressures using generalized cubic EoS

The present work has devised the approach for efficiently estimating the thermophysical properties of dimethyl ether (DME) at high pressure conditions relevant to its potential application for compression ignition engines. From a practical standpoint, the thermodynamic properties such as density, heat capacity, enthalpy, entropy, and speed of sound are formulated based on a generalized cubic equation of state (EoS). Comparisons with reference data from a highly accurate empirical multi-parameter EoS demonstrate that the present thermodynamic model has reasonable accuracy for engineering purpose over a wide range of pressure and temperature. By combining it with a transport model which extends the kinetic gas theory with dense-fluid correction, the viscosity and thermal conductivity of DME are also reproduced well for the thermodynamic states from compressed liquid to supercritical fluid.     

Experimental and modeling studies on extraction of catechin hydrate and epicatechin from Indian green tea leaves

A systematic investigation of effect of various parameters, for example, temperature, speed of agitation, particle size, and solid loading, on the percentage extraction of catechin hydrate (CH) and epicatechin (EP) was conducted. The extraction was performed with water, methanol, and ethanol. Water was found to be the best solvent for both. Percentage extraction of CH was found to decrease with temperature beyond 46°C; however, this is not the case for epicatechin. The thermal stability analysis of both the compounds was performed to ensure decomposition. This supported the experimental observation of batch extraction. Size of particle has little effect on percentage extraction of EP, but it increases for CH with decrease in particle size, which is probably because of decrease in diffusion path length. Assuming flat geometry of the particles, the process is modelled and compared with experimental data at different experimental conditions. The experimental data fitted well with the model proposed by Wongkittipong. The effective diffusion coefficients through the solid matrix of Indian green tea leaves for CH and EP estimated from the diffusion model were found to be in the range 1.29 × 10^–13 to 3.40 × 10^–13 m²/s and 1.20 × 10^–13 m²/s to 3.38 × 10^–13 m²/s, respectively. The effect of temperature on diffusion coefficient of CH and EP was determined using the model. The energy of activation required for diffusion was found to be 32.78 and 30.28 kJ/kmol, respectively for CH and EP.     

The electro-oxidation of dimethyl ether on platinum-based catalyst

Cyclic voltammetry (CV) and stripping voltammetry were used to study the electro-oxidation of dimethyl ether (DME) on powder microelectrodes (PMEs) containing Pt black and Pt–Ru black. As evidenced by current–time curves of DME oxidation, Pt–Ru was better than Pt in catalytic oxidation of DME, which is due to the high concentration of OH_ads species on its surface. Results also showed that high temperature not only promotes the oxidation of DME, but also increases the concentration of OH_ads species formed by water decomposition. In addition, the performance of single direct DME fuel cell was investigated combined with gas chromatographic (GC) analyses of its anode outlet stream. Based on CV tests, a mechanism of DME electro-oxidation was tentatively proposed, indicating two kinds of DME adsorption modes, Pt–CO and Pt–COH existed on Pt surface.     

甲醇气相脱水制二甲醚的催化剂

采用硝酸铝和氨水中和方法得到拟薄水铝石为原料,制备了甲醇制二甲醚催化剂。考察拟薄水铝石制备过程中的中和pH值、中和温度以及催化剂制备过程中的煅烧温度对甲醇气相脱水制二甲醚性能的影响。结果表明,当中和pH值在8.0±0.2、中和温度为50～60 ℃以及煅烧温度在550～600 ℃时得到的甲醇制二甲醚催化剂活性最高。通过在催化剂上添加SiO2、SO42?、PO43?等对甲醇脱水催化剂进行改性表明,改性后甲醇脱水催化剂活性有明显的提高。     

二甲醚催化氧化合成醋酸乙烯

通过浸渍法制得负载型H_4SiW_(12)O_(40)-MoO_3/SiO_2催化剂,并在连续流动同定床反应装置上考察了其在二甲醚催化氧化合成醋酸乙烯的催化活性,研究了反应压力和助催化组分改性催化剂对二甲醚催化氧化合成醋酸乙烯的影响.结果表明,当原料气配比为n(DNE):n(O_2):n(Ar)=1.5:1:1,反应压力为0.25 MPa,CoO改性H_4SiW_(12)O_(40)-MoO_3/SiO_2催化剂催化氧化二甲醚合成醋酸乙烯的选择性由3.69%提高至7.09%,二甲醚的转化率由55.20%增加至61.18%.X射线衍射结果表明,CoO能促进MoO3和U_4SiW_(12)O_(40)在SiO_2载体表面上均匀分布.NH3程序升温脱附结果显示,添加氧化钴助催化组分能进一步调变H_4SiW_(12)O_(40)MoO_3/SiO_2催化剂表面酸性.