Compositional modeling and simulation of dimethyl ether (DME)-enhanced waterflood to investigate oil mobility improvement

Dimethyl ether （DME） is a widely used industrial compound, and Shell developed a chemical EOR technique called DME- enhanced waterflood （DEW）. DME is applied as a miscible solvent for EOR application to enhance the performance of conventional waterflood. When DME is injected into the reservoir and contacts the oil, the first-contact miscibility process occurs, which leads to oil swelling and viscosity reduction. The reduction in oil density and viscosity improves oil mobility and reduces residual oil saturation, enhancing oil production. A numerical study based on compositional simulation has been developed to describe the phase behavior in the DEW model. An accurate compositional model is imperative because DME has a unique advantage of solubility in both oil and water. For DEW, oil recovery increased by 34% and 12% compared to conventional waterflood and CO2 flood, respectively. Compositional modeling and simulation of the DEW process indicated the unique solubility effect of DME on EOR performance.

Multidimensional modeling of Dimethyl Ether(DME) spray combustion in DI diesel engine

In the present study a modified CFD code KIVA3V was used to simulate the spray combustion in a small DI diesel engine fueled with DME. The improved spray models consider more spray phenomena such as cavitation flow in nozzle hole, jet atomization, droplet second breakup and spray wall interaction. Otherwise, a reduced DME reaction mechanism is implemented in the combustion model, and a new turbulent combustion model?Partial Stirred Reactor (PaSR) model is selected to simulate the spray combustion process, the effects of turbulent mixing on the reaction rate are considered. The results of engine modeling based on those models agreed well with the experimental measurements. Study of temperature fields variation and particle traces in the combustion chamber revealed that the engine combustion system originally used for diesel fuel must be optimized for DME.

Direct Dimethyl Ether Synthesis

Dimethyl ether (DME) is a clean and economical alternative fuel which can beproduced from natural gas through synthesis gas. The properties of DME are very similar to those ofLP gas. DME can be used for various fields as a fuel such as power generation, transportation, homeheating and cooking, etc. It contains no sulfur or nitrogen. It is not corrosive to any metal andnot harmful to human body. An innovative process of direct synthesis of DME from synthesis gas hasbeen developed. Newly developed catalyst in a slurry phase reactor gave a high conversion and highselectivity of DME production. One and half year pilot scale plant (5 tons per day) testing, whichwas supported by METI, had successfully finished with about 400 tons DME production.

Attrition resistant catalyst for dimethyl ether synthesis in fluidized-bed reactor

Fluidized-bed reactor is a candidate for dimethyl ether （DME） synthesis from syngas because of its excellent heat removal capability. In order to improve the attrition resistance of catalyst, an amount of silica sol as binder was added to the catalyst composed of methanol synthesis component CuO/ZnO/Al2O3 and methanol dehydration component HZSM-5, which was prepared by coprecipitation and shaped by spray drying to get spherical particles. The effect of silica sol on the catalytic activity was investigated in a fixed-bed flow microreactor. Based on the experiment results, silica sol in the range of 0-20wt% had small effect on the catalytic activity. Generally, the CO conversion and DME yield decreased with the increase in concentration of silica sol, while the attrition resistance of catalysts increased with increasing silica sol, indicating that it was feasible to improve the attrition resistance without greatly sacrificing the activity of catalyst. In addition, the characterizations of catalysts were carried out using Brunauer-Emmett-Teller （BET）, X-ray powder diffraction （XRD） and temperature programmed reduction （TPR）.

Mathematical Simulation and Design of Three-Phase Bubble Column Reactor for Direct Synthesis of Dimethyl Ether from Syngas

A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether （DME） from syngas, considering both the influence of part inert carrier backmixing on transfer and the influence of catalyst grain sedimentation on reaction. On the basis of this model, the influences of the size and reaction conditions of a 100000 t/a DME reactor on capacity were investigated. The optimized size of the 10000 t/a DME synthesis reactor was proposed as follows： diameter 3.2 m, height 20 m, built-in 400 tube heat exchanger （Ф 38×2 mm）, and inert heat carrier paraffin oil 68 t and catalyst 34.46 t. Reaction temperature and pressure were important factors influencing the reaction conversion for different size reactors. Under the condition of uniform catalyst concentration distribution, higher pressure and temperature were proposed to achieve a higher production capacity of DME. The best ratio of fresh syngas for DME synthesis was 2.04.

Enhanced stability of Fe-modified CuO-ZnO-ZrO_(2)-Al_(2)O_(3)/HZSM-5 bifunctional catalysts for dimethyl ether synthesis from CO_(2)hydrogenation

A series of iron(Fe)modified CuO-ZnO-ZrO_(2)-Al_(2)O_(3)(CZZA)catalysts,with various Fe loadings,were prepared using a co-precipitation method.A bifunctional catalyst,consisting of Fe-modified CZZA and HZSM-5,was studied for dimethyl ether(DME)synthesis via CO_(2)hydrogenation.The effects of Fe loading,reaction temperature,reaction pressure,space velocity,and concentrations of precursor for the synthesis of the Fe-modified CZZA catalyst on the catalytic activity of DME synthesis were investigated.Long-term stability tests showed that Fe modification of the CZZA catalyst improved the catalyst stability for DME synthesis via CO_(2)hydrogenation.The activity loss,in terms of DME yield,was significantly reduced from 4.2%to 1.4%in a 100 h run of reaction,when the Fe loading amount was 0.5(molar ratio of Fe to Cu).An analysis of hydrogen temperature programmed reduction revealed that the introduction of Fe improved the reducibility of the catalysts,due to assisted adsorption of H2 on iron oxide.The good stability of Femodified CZZA catalysts in the DME formation was most likely attributed to oxygen spillover that was introduced by the addition of iron oxide.This could have inhibited the oxidation of the Cu surface and enhanced the thermal stability of copper during long-term reactions.

Experimental Study on Dimethyl Ether Combustion Process in Homogeneous Charge Compression Ignition Mode

Experimental study on homogeneous charge compression ignition （HCCI） combustion process was carried out on a single-cylinder direct injection diesel engine fueled with dimethyl ether（DME）. The influence of inert gas CO2 on the ignition and combustion process was investigated. The research results indicate that because of the high cetane number of DME, the stable HCCI operating range is quite narrow while the engine has a high compression ratio. The HCCI operating range can be largely extended when the inert gas is inducted into the charging air. HCCI combustion of DME presents remarkable characteristic of two-stage combustion process. As the concentration of inert gas increases, the ignition timing of the first combustion stage delays, the peak heat release rate decreases, and the combustion duration extends. Inducting inert gas into charging air cannot make the combustion and heat release of DME occur at a perfect crank angle position. Therefore,to obtain HCCI operation for the fuel with high cetane number,other methods such as reducing engine compression ratio should be adopted. Emission results show that under HCCI operation, a nearly zero NOx emission can be obtained with no smoke emissions. But the HC and CO emissions are high, and both rise with the increase of the concentration of inert gases.

Effect of Dimethyl Ether Co-feed on Catalytic Performance of Methane Dehydroaromatization over Mo/HZSM-5 Catalyst

The effect of dimethyl ether (DME) co-feed on the catalytic performance of methane dehy-droaromatization (MDA) over 6Mo/HZSM-5 catalyst was investigated as a function of DME concentration under reaction conditions of T=1023 K, p=101 kPa and SV=1500 ml/(g·h). A high benzene yield was obtained and the stability of the catalyst was improved by adding 1.5%DME to the CH4 feed. The C6H6 yield was as high as ca. 10% even after reaction for 6 h. The stability of the catalyst was further improved when DME concentration in the co-feed gas was increased to an appropriate value. TGA and TPO results of the used 6Mo/HZSM-5 catalyst showed that the amount of coke on the used catalyst was reduced and the chemical nature of the coke was changed. When 1.5%DME was added to the CH4 feed, the coke formed on the catalyst could be burned off more easily than that when only CH4 was used as reactant. It is supposed that the oxygen in DME may play a role in preventing the coke burnt off at lower temperature from transforming into the coke burnt off at higher temperature, which results in the improvement of the stability of the catalyst.

Advances in low-temperature extraction of natural resources using liquefied dimethyl ether

This review summarized the valuable works on the extraction technologies using pure liquefied dimethyl ether(DME)as the organic solvent.DME is a colorless gas with a slight ether-like fragrance at room temperature and pressure.Due to some special properties,such as the strong ability for extracting organic compounds and water,high extraction rate,cheap price,low extraction temperature,and energy consumption,environmental friend-liness,safety,and good compressibility,the application of liquefied DME to the extraction process shows many advantages and has strong potential market competitiveness.On the other hand,the drawbacks of liquefied DME extraction technology were also revealed,mainly on fire hazards,solvent loss,and lack of large-scale application.Furthermore,the previous studies on the application of liquefied DME extraction technology were divided into three parts based on the extracts(water,lipid/oil,and specific ingredients)and listed one by one.The research of the liquefied DME extraction process is still in development.In the future,it is expected that this technology can be continuously improved and optimized in both lab and industrial scales,together with the extension of its application range to more various natural resources.

Mechanism and catalytic performance for direct dimethyl ether synthesis by CO2 hydrogenation over CuZnZr/ferrierite hybrid catalyst

Direct synthesis of dimethyl ether(DME)by CO2 hydrogenation has been investigated over three hybrid catalysts prepared by different methods:co-precipitation,sol-gel,and solid grinding to produce mixed Cu,ZnO,ZrO2 catalysts that were physically mixed with a commercial ferrierite(FER)zeolite.The catalysts were characterized by N2 physisorption,X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),temperature programmed desorption of CO2(CO2-TPD),temperature programmed desorption of NH3(NH3-TPD),and temperature programmed H2 reduction(H2-TPR).The results demonstrate that smaller CuO and Cu crystallite sizes resulting in better dispersion of the active phases,higher surface area,and lower reduction temperature are all favorable for catalytic activity.The reaction mechanism has been studied using in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS).Methanol appears to be formed via the bidentate-formate(b-HCOO)species undergoing stepwise hydrogenation,while DME formation occurs from methanol dehydration and reaction of two surface methoxy groups.

Exergy losses in premixed flames of dimethyl ether and hydrogen blends

A second-law thermodynamic analysis was conducted for stoichiometric premixed dimethyl ether(DME)/hydrogen(H2)/air flames at atmospheric pressure.The exergy losses from the irreversibility sources,i.e.,chemical reaction,heat conduction and species diffusion,and those from partial combustion products were analyzed in the flames with changed fuel blends.It is observed that,regardless of the fuel blends,chemical reaction contributes most to the exergy losses,followed by incomplete combustion,and heat conduction,while mass diffusion has the least contribution to exergy loss.The results also indicate that increased H2 substitution decreases the exergy losses from reactions,conduction,and diffusion,primarily because of the flame thickness reduction at elevated H2 substitution.The decreases in exergy losses by chemical reactions and heat conduction are higher,but the exergy loss reduction by diffusion is slight.However,the exergy losses from incomplete combustion increase with H2 substitution,because the fractions of the unbumed fuels and combustion intermediates,e.g.,H2 and OH radical,increase.The overall exergy losses in the DME/H2 flames decrease by about 5%with increased H2 substitution from 0%to 100%.

Developments of Catalysts for Hydrogen Production from Dimethyl Ether

1 Results Dimethyl ether (DME) is expected as a clean fuel of the 21st century.I have developed new catalysts for hydrogen production by steam reforming of DME.Cu-Zn/Al2O3 catalysts prepared by the sol-gel method produce large quantities of H2 and CO2 by DME steam reforming under lower reaction temperature[1].However,the sol-gel catalysts will be more expensive than general catalysts prepared by impregnation methods and coprecipitation methods,because the precursor,alkoxides are very expensive.For pract...

二甲基醚(DME)燃烧特性研究

作者在定容燃烧弹上用火焰直接成像法研究二甲基醚 (DME)燃烧过程 ,研究了 DME的滞燃期和火焰传播特性以及不同环境温度和压力对燃烧过程的影响。研究结果表明 ,DME的滞燃期比柴油短 ,燃烧室内的温度和压力升高时 ,滞燃期缩短 ;DME的着火位置靠近喷嘴一侧 ,柴油与 DME的体积相同时 ,DME的燃烧持续期比柴油短 ;DME的燃烧火焰亮度比柴油小 ,表明 DME的燃烧温度比柴油低。燃烧后期 ,燃用 DME时 ,喷嘴有明显的泄漏现象。此外 ,作者在单缸直喷式柴油机上进行了燃用 DME的燃烧特性试验研究 ,研究结果表明 ,DME的预混合燃烧放热率比柴油低 ,缸内最大爆发压力和最大压力升高率比柴油低。由于喷油持续期延长 ,DME的燃烧持续期比柴油长 ,在上止点后 80° CA出现一个较大的放热峰值。

高温环境下二甲基醚(DME)喷雾特性的实验研究

对二甲基醚 (DME)在高温条件下的喷雾特性进行了实验研究。研究结果表明 :与常温条件相比 ,DME喷雾体喷雾核心面积变小 ,喷雾体呈薄雾状发展 ,DME蒸发极为迅速 ;高温条件下 ,喷油前期DME的嘴端压力比常温下小 ;在所实验的温度范围内 ,环境温度对喷雾体的贯穿距离没有影响 ;环境密度对喷雾体贯穿距离的影响也较小 ,环境密度增大时 。

ZS195柴油机燃用二甲醚(DME)—柴油混合燃料的试验研究

二甲醚粘度低,会使高压供油系统产生泄漏及早期磨损。在二甲醚中添加低比例的柴油(简称二元燃料),其柴油既参与燃烧,又相应提高了混合燃料的粘度。首先对二甲醚添加低比例的柴油进行优化并对柴油机供油量、供油提前角和针阀开启压力进行优化匹配,然后对ZS195柴油机燃用二元燃料进行试验研究。结果表明:在ZS195柴油机上燃用二元燃料,其功率和转矩略优于原柴油机,发动机在全负荷范围内接近无烟排放,NOx大幅度下降。试验还表明,采用这种二元燃料可使供油系统长期稳定地工作。

二甲基醚(DME)喷雾一般特性的试验研究(英文)

介绍了在高压环境下对二甲基醚 (DME)喷雾一般特性的试验研究结果 ,并与柴油的喷雾特性进行了比较。试验研究是在定容燃烧弹上进行的 ,用阴影法通过高速数字摄影机拍摄了二甲基醚和柴油的喷雾发展过程 ,应用计算机图像处理进行喷雾过程图像再现。研究结果表明 :DME的喷雾贯穿距离比柴油小 ,喷雾锥角比柴油大 ;在喷雾自由发展过程中 ,DME的蒸发速度比柴油快 ;环境密度对 DME喷雾特性的影响与柴油相似 ,即密度增大 ,锥角增大 ,贯穿距离减小。在燃烧室壁面附近 ,柴油的喷雾锥角迅速增大 ,而 DME喷雾锥角几乎没有明显的变化。

直喷柴油机掺烧低比例二甲醚(DME)和高比例柴油的试验研究

在直喷柴油机上掺烧低比例二甲醚(DME)和高比例柴油二元混合燃料进行试验研究,除低压供油系统进行技术改造外,原柴油机的结构和参数不做任何改变。试验结果表明:掺烧30%二甲醚与70%柴油二元混合燃料,不采取任何尾气处理措施,碳烟排放比原柴油机降低67%,NOx排放与原柴油机相当,燃油消耗率比原柴油机降低19.3%;直喷柴油机掺烧低比例二甲醚和高比例柴油二元混合燃料在降低碳烟和燃油消耗率方面的优越性能。

二甲醚(DME)制冷性能的实验研究

在二甲醚热物理性质分析的基础上，对二甲醚的制冷性能进行了实验研究，并与常用制冷剂R134a的制冷性能进行对比，结果表明：在同一实验装置上，在相同冷凝温度、不同蒸发温度下的二甲醚的制冷量比R134a约低10％～15％，制冷系数（COP）比R134a低约3％～9％，DME可以直接充注用于R134a制冷系统，可以作为R134a的直接替代物。通过对不同种类的润滑油的实验测试表明：常用的脂类油和矿物油均可用作二甲醚制冷系统的润滑油，使用脂类油时二甲醚排气温度比使用矿物油时稍高，矿物油更适于应用于二甲醚制冷系统。

二甲基醚(DME)碰壁喷雾特性和燃烧特性试验研究

用阴影法和火焰直接成像法对二甲基醚 (DME)碰壁喷雾特性和燃烧特性进行了试验研究。研究结果表明 ,二甲基醚碰壁后沿壁面发展特性与柴油极为相似 ,即沿壁面径向扩散 ,形成油雾的爬壁现象 ,二甲基醚沿壁面发展速度比柴油慢 ,但碰壁后的反弹量比柴油多 ;加热条件下二甲基醚碰壁试验研究表明 ,热碰壁沿壁面的发展速度比冷碰壁快 ,反弹量比冷碰壁多。在平板上方有一个明显的浓度梯度变化区域 ,碰壁后期在平板与燃烧室壁面存在一个二甲基醚浓度高的三角区域。二甲基醚碰壁对燃烧滞燃期影响不大 ,但着火位置靠近壁面 ,大部分的二甲基醚都是着壁之后燃烧 ,并且燃烧火焰在高浓度的三角区域持续较长时间 ,因而碰壁燃烧持续期略有延长 ,与柴油相比 ,二甲基醚燃烧火焰几乎经过整个壁面上部燃烧室的区域 ,火焰经过的面积大。