Charge transfer in plasma assisted dry reforming of methane using a nanosecond pulsed packed-bed reactor discharge

This paper is aimed to investigate the effect of packing material on plasma characteristic from the viewpoint of charge transfer process.Both the charge accumulation and release processes in the dielectric barrier discharge reactor and packed-bed reactor were investigated by measuring voltage and current waveforms and taking ICCD images.The packing material was ZrO2 pellets and the reactors were driven by a parameterized nanosecond pulse source.The quantity of transferred charges in the dielectric barrier discharge reactor was enhanced when decreasing pulse rise time or increasing pulse width(within 150 ns),but reduced when the gas gap was packed with pellets.The quantity of accumulated charges in the primary discharge was larger than the quantity of released charges in the secondary discharges in the dielectric barrier discharge reactor,but they were almost equal in the packed-bed reactor.It indicates that the discharge behavior has been changed from the view of charge transfer process once the gas gap was packed with pellets,and the ICCD images confirmed it.

Reaction Selectivity Improvement for Reduction of Nitrobenzene in a Packed-Bed Electrode Reactor under Periodic-Current Control

Rectangular wave current control of the electrochemical reduction of nitrobenzene im-proves the selectivity for p-aminophenol(PAP) compared to direct current(d.c.) control at thesame average current density in a flow-by packed-bed reactor.Optimal increase in PAP selectivitycan be obtained at about a frequency of 50Hz and a duty cycle of 0.2.A mathematical model isset up to incorporate the effects of mass transfer,hydrogen evolution and double layer charging,and is solved using the Duhamel’s superposition principle and the modified Crank-Nicolson methodwith the upwind scheme.The conventional d.c.control cases are also calculated for comparison.Calculations can be applied to predict the reaction results under periodic current and d.c.control,but both display the same trends compared to experimental data.

Ozone generation enhanced by silica catalyst in packed-bed DBD reactor

In this paper,three dielectric barrier discharge(DBD)configurations,which were plain DBD with no packing,DBD with packed pure quartz fibers and DBD with packed loaded quartz fibers,were employed to investigate the effect and catalytic mechanism of catalyst materials in a packed-bed ozone generator.From the experimental results,it was clear that the DBD configuration with packed pure fibers and packed loaded fibers promotes ozone generation.For the packed-bed reactor,ozone concentration and ozone yield were enhanced by an increase of electric field in the discharge gap with the packed-bed effect.Meanwhile,the enhancement of ozone concentration and yield for the DBD reactor packed by loaded fibers with silica nanoparticles was due to the catalysis of silica nanoparticles on the fiber surface.The adsorption of silica nanoparticles on the fiber surface can prolong the retention time of active species and enhance surface reactions.

Numerical simulation of packed-bed reactor for oxidative coupling of methane

A three-dimensional geometric model of the oxidative coupling of methane （OCM） packed-bed reactor loaded with Na2WO4-Mn/SiO2 partic- ulate catalyst was set up, and an improved Stansch kinetic model was established to calculate the OCM reactions using the computational fluid dynamics method and Fluent software. The simulation conditions were completely the same with the experimental conditions that the volume velocity of the reactant was 80 mL/min under standard state, the ratio of CH4/O2 was 3, the temperature and pressure were 800 ℃ and 1 atm, respectively. The contour of the characteristics parameters in the catalyst bed was analyzed, such as the species mass fractions, temperature, the heat flux on side wall surface, pressure, fluid density and velocity. The results showed that the calculated values matched well with the experimental values on the conversion of CH4 and the selectivity to products （C2H6, C2H4, CO2, CO） in the reactor outlet with an error range of 4-2%. The mass fractions of CH4 and O2 decreased from 0.6 and 0.4 in the catalyst bed inlet to 0.436 and 0.142 in the outlet, where the mass fractions of C2H6, C2H4, CO and CO2 were 0.035, 0.061, 0.032 and 0.106, respectively. Due to the existence of laminar boundary layer, the contours of each component bent upwards in the vicinity of the boundary layer. This OCM reaction was volume increase reaction and the total moles of products were greater than those of reactants. The flow field in the catalyst bed maintained constant temperature and pressure. The fluid density decreased gradually from 2.28 kg/m3 in the inlet of the catalyst bed to 2.22 kg/m3 in the outlet of the catalyst bed, while the velocity increased from 0.108 m/s to 0.115 m/s.

Methane conversion into higher hydrocarbons with dielectric barrier discharge micro-plasma reactor

We reported a coaxial,micro-dielectric barrier discharge(micro-DBD)reactor and a conventional DBD reactor for the direct conversion of methane into higher hydrocarbons at atmospheric pressure.The effects of input power,residence time,discharge gap and external electrode length were investigated for methane conversion and product selectivity.We found the conversion of methane in a micro-DBD reactor was higher than that in a conventional DBD reactor.And at an input power of 25.0 W,the conversion of methane and the total C2+C3 selectivity reached 25.10% and 80.27%,respectively,with a micro-DBD reactor of 0.4 mm discharge gap.Finally,a nonlinear multiple regression model was used to study the correlations between both methane conversion and product selectivity and various system variables.The calculated data were obtained using SPSS 12.0 software.The regression analysis illustrated the correlations between system variables and both methane conversion and product selectivity.

Precision Synthesis of a Long-Chain Silane Coupling Agent Using Micro Flow Reactors and Its Application in Dentistry

In dentistry, a wide range of materials is available for restorative treatment;a typical product of such restorative materials mainly consists of radically polymerizable monomer(s) and inorganic filler(s) (for added physical strength), as well as a surface modifier (e.g. silane coupling agent) for improved affinity between monomer and filler. It is favorable to use an optimal surface modifier depending on the respective restorative materials. However, commercially available surface modifiers, which are synthesized by the ton, are not always suited for what is required for properties of the many different dental restorative materials. As a potential solution to such a problem, we focused on the latest technology, “micro flow reactors” that enabled an on-demand low-volume synthesis of many types of surface modifiers. Using micro reaction fields of such flow reactors, we synthesized a novel long-chain silane coupling agent. Compared to the control system synthesized using a conventional reaction flask, the novel system enabled significant reduction in reaction time without inducing any major side reactions. A dental composite resin that was treated with the novel coupling agent exhibited higher toughness, suggesting that such a silane coupling agent was an effective surface modifier.

Improved catalytic performance of Ni catalysts for steam methane reforming in a micro-channel reactor

Milliseconds process to produce hydrogen by steam methane reforming （SMR） reaction, based on Ni catalyst rather than noble catalyst such as Pd, Rh or Ru, in micro-channel reactors has been paid more and more attentions in recent years. This work aimed to further improve the catalytic performance of nickel-based catalyst by the introduction of additives, i.e., MgO and FeO, prepared by impregnation method on the micro-channels made of metal-ceramic complex substrate. The prepared catalysts were tested in the same micro-channel reactor by switching the catalyst plates. The results showed that among the tested catalysts Ni-Mg catalyst had the highest activity, especially under harsh conditions, i.e., at high space velocity and/or low reaction temperature. Moreover, the catalyst activity and selectivity were stable during the 12 h on stream test even when the ratio of steam to carbon （SIC） was as low as 1.0. The addition of MgO promoted the active Ni species to have a good dispersion on the substrate, leading to a better catalytic performance for SMR reaction.

Micro-mixing in chemical reactors:A perspective

Micro-mixing is an important mechanism, which works simultaneously with macro-mixing in chemical reactors in process industries, for achieving the best selectivity with respect to desired products. In about a half century, a huge amount of data and knowledge has been accumulated from theoretical and experimental studies on micromixing. Nevertheless, those results are mostly composites of simplified theoretical and empirical models, and the true nature of interactions of flow inhomogeneity and micro-mixing with chemical reaction has not been fully unveiled. This article reviews the progress in micro-mixing study in chemical reactors to date. A few important topics related to the nature, experimental evaluation, and numerical simulation of micro-mixing are addressed.Some suggestions are given hopefully to motivate more chemical engineers to devote their efforts to better understanding of micro-mixing in chemical reactors.

The Intelligent Properties of Micro-reactors for Preparating Nanoparticles

TiO2 nanoparticles were synthesized by using micro-reactors. The shape and size of the nanoparticles produced from the original micro-reactors and the five times recycled micro-reactors mother liquor were investigated on transmission electron microscopy (TEM) by using the original sample, freeze prepared sample, and dyeing treated sample, respectively. UV-VIS spectrometry was used to study the growth process of TiO2 nanoparticles in main reactors. The results showed that micro-reactors with nanometer magnitude had spherical or oval structures, and could restore to their original structure after they were destroyed. The products prepared in the original micro-reactors were similar to that in the micro-reactors recycled for many times, suggesting that the micro-reactors had memory function.

Performance of Sequencing Biofilm Batch Reactor(SBBR) under Micro-aerobic Condition for Aniline-Contaminated Wastewater Treatment

The performance of sequencing biofilm batch reactor( SBBR) under micro-aerobic condition for aniline-contaminated wastewater treatment was investigated in this study. Dissolved oxygen( DO) and aniline concentrations were selected as the operating variables to analyze,model,and optimize the process. In order to analyze the process,5 dependent parameters,chemical oxygen demand( COD),aniline,ammonium,total nitrogen( TN),and total phosphorous( TP) removal as the process responses were studied. From the results, increase in DO concentration could promote the removal of COD,aniline,ammonium,and TN,while increase in aniline concentration has a slightly negative impact on the removal of pollutants. The optimum DO concentration was found to be 0. 4-0. 5 mg /L. The removal efficiencies for COD,aniline,ammonium,and TN at the optimum point( DO concentration0. 5 mg /L,aniline concentration 11 mg /L) were 95. 84%,100%,75. 72%,and 45. 39%,respectively. The oxidative deamination was the main degradation method for aniline under micro-aerobic condition. Simultaneously nitrification-denitrification( SND)process performed under micro-aerobic condition and about 20%-40% nitrogen was removed by SND.

基于裂变矩阵的谐波计算及其在气冷微堆功率监测中的应用

气冷微堆受限于堆芯体积及堆内高温高辐照运行环境,仅能布置少量堆外探测器用于功率监测。采用基于裂变矩阵产生高阶谐波的谐波展开法进行堆芯功率重构。通过反应堆蒙特卡罗程序RMC统计裂变矩阵,使用瑞利商迭代法求解特征向量,构造高阶谐波库;将堆芯三维功率分布用高阶谐波展开,结合探测器响应矩阵,实现三维功率在线监测。进一步研究了温度、燃耗、控制棒棒位对功率重构精度的影响,结果表明:温度、燃耗变化的工况下,气冷微堆节块平均功率的重构值与蒙特卡罗模拟参考值之间的均方根相对误差小于3%,最大相对误差小于5%;控制棒棒位变化对重构精度的影响较大,通过采用临近棒位的谐波组进行功率重构,均方根相对误差小于3%。验证结果为气冷微堆在线监测系统的后续研发提供参考。

一种月面微型热管堆电源概念设想

未来月球科研站建设及月面探测等任务需解决长期稳定能源及电力供给问题,受月面复杂环境影响,月面能源供给挑战极大。核反应堆电源具有长寿命、全天候、环境耐受力强等优势,是解决月面任务长期能源需求的理想选择,热管冷却型反应堆作为一种新型反应堆电源具有系统简单、结构紧凑、可靠性高等特点,且易于实现长寿命设计。针对目前月面能源问题,提出了采用500 W电功率月面微型热管堆电源供电的初步设想,并重点对其屏蔽设计及辐射防护问题进行了研究,提出了相关屏蔽设计方案及辐射防护措施。经过初步屏蔽设计研究,该电源可采用移动式、月面固定点位布置及浅坑式布置多种方式为月面用电设备供电,质量可约束在500 kg左右,轻质且微型,为科研站月面核反应堆电源屏蔽设计提供了思路。

2,4,5-三碘基咪唑在微通道式反应器中的硝化反应

采用微通道式反应技术,以2,4,5-三碘基咪唑(2,4,5-TII)为原料,分别在20%、50%、65%、98%不同质量分数的硝酸中进行硝化反应,合成2,4,5-三硝基咪唑的咪唑盐(2,4,5-TNI咪唑盐);采用傅里叶变换红外光谱(FT-IR)、核磁共振光谱(NMR)、元素分析(EA)和熔点测定法等表征了产物结构。结果表明,采用微通道式硝化反应技术时,由2,4,5-TII制备2,4,5-TNI咪唑盐最优工艺条件为:2,4,5-TII与98%硝酸摩尔比为1∶20、在微通道式反应器停留时间6min、反应液温度70~72℃,得率为21.8%。微通道式反应工艺与常规釜式反应工艺相比,具有反应时间短、硝化试剂用量降低、反应温度略有降低、得率略有提高的优点,但也无法完全避免氧化副反应的发生。

基于谐波参数化方法预测控制棒棒位

微型堆中控制棒棒位的准确探测对于微纳型核能系统的远程实时监测和无人化智能化运营至关重要,也会影响功率在线监测的精度。本文提出了一种谐波参数化方法,将高阶谐波拟合为控制棒棒位的多项式函数矩阵,构造探测器响应方程,通过搜索棒位以最小化残差来实现精准的控制棒棒位预测,同时可得到对应的高阶谐波及堆芯重构功率。基于棱柱式气冷堆模型完成验证,数值结果表明,预测棒位的平均偏差为1.6 cm,预测精度较高;相比于固定高阶谐波,节块级功率重构的最大均方根相对误差从6.1%降至3%以内,最大相对误差从14.5%降至5%以内。这些结果验证了谐波参数化方法预测控制棒棒位以及改善堆芯功率重构精度的可行性,并为后续气冷微堆在线监测及故障诊断提供了一种思路。

1-甲基-2,4,5-三硝基咪唑的微通道合成技术

采用微通道式反应技术,分别以1-甲基-2,4-二硝基咪唑(2,4-MDNI)与硝硫混酸硝化反应、2,4,5-三硝基咪唑钾盐(2,4,5-TNIK)与硫酸二甲酯(DMS)甲基化反应,合成了1-甲基-2,4,5-三硝基咪唑(MTNI);采用傅里叶变换红外光谱(FT-IR)、核磁共振光谱(NMR)、元素分析(EA)、熔点等表征了其结构。结果表明,采用微通道反应技术,基于2,4-MDNI硝化工艺的最优条件为:2,4-MDNI和发烟硝酸摩尔比为2∶3、发烟硝酸和20%发烟硫酸体积比为1∶2、在微通道反应器中停留时间为12min、反应器中反应液温度为75℃,得率和纯度分别为78.1%和99.2%。基于2,4,5-TNIK甲基化工艺的最优条件为:2,4,5-TNIK、DMS和K2CO3摩尔比为1∶2∶2、在微通道反应器中停留时间为20min、反应温度为70℃,得率和纯度分别为71.3%和99.4%。由此可得,微通道式反应工艺与常规釜式反应工艺相比,具有反应时间短、硝化试剂用量少、反应温度略有降低、得率略有提高的优点。

A convenient method for measuring gas-liquid volumetric mass transfer coefficient in micro reactors

The research on gas-liquid multiphase reactions using micro reactors is becoming increasingly widespread, given their excellent mass transfer performance. Establishing an accurate and reliable method to measure the gas-liquid mass transfer performance of micro reactors is crucial for evaluating and optimizing the design of micro reactor structure. In this paper, the physical absorption method of aqueous solution-CO_(2) and the chemical absorption method of sodium carbonate solution-CO_(2) were proposed. By analyzing the chemical reaction equilibrium during the absorption process, the relationship between the mass transfer of CO_(2) and the solubility of hydroxide ions in the solution was established, and the total gas-liquid mass transfer coefficient was immediately obtained by measuring the p H value. The corresponding testing platform and process have been established based on the characteristics of the proposed method to ensure fast and accurate measurement. In addition, the chemical absorption method takes into account temperature factors that were not previously considered. The volumetric mass transfer coefficient measured by these two methods is in the same range as those measured by other methods using the same microchannel structure in previous literature. The methods have the advantages of low equipment cost, faster measurement speed, and simpler procedures, which can facilitate its wide application to the evaluation of the mass transfer performance and hence can guide the structure optimization of microchannel reactors.

臭氧微纳米气泡-高级氧化耦合工艺深度处理工业废水

工业废水具有水量大、水质复杂、污染物浓度高、毒性强、腐蚀性强及难降解等特点,传统处理技术难以取得良好效果。本研究首次将压力强化臭氧微纳米气泡与高级氧化工艺耦合,构建了新型压力强化臭氧微纳米气泡—高级氧化耦合工艺反应器。从污染物去除率、不同条件下反应器内气泡粒径差异、液体中臭氧浓度、溶解氧浓度及尾气中臭氧浓度等多角度明确了反应器的最优参数为0.3 Mpa的出水压力及0.5 L/min的进气流量,明确了反应器的最佳使用温度范围为15℃至25℃。并从活性自由基的角度阐明了压力强化臭氧微纳米气泡耦合高级氧化工艺去除水中难降解污染物过程中的机制。本研究的研究成果有望为实现控制工业废水处理成本、提高COD去除率和矿化难降解污染物,为臭氧微纳米气泡技术的高效运行及安装优化提供理论依据和技术支持。

微通道反应器制备纳米硫酸钡的工艺研究

利用微通道反应器,以硫酸钠和硫化钡为原料反应并进行纳米硫酸钡粒子制备研究,考察了微通道反应器制备纳米硫酸钡粒子的影响因素,并对产品进行激光粒度检测和TEM测试。结果表明,该法可以制备出平均粒径50~80 nm、分布窄的纳米硫酸钡粒子。

铅冷微堆SMILE典型无保护瞬态热工安全分析

核能系统小型化是核能未来发展的重要方向,其中小型铅冷快堆是技术路线之一。在小型铅冷快堆研发过程中,瞬态工况下热工水力安全特性是重要的研究内容之一,这不仅是对反应堆安全特性的重要验证,也对反应堆系统的后续设计完善具有重要参考价值。兆瓦级铅冷快堆SMILE是国家电投集团科学技术研究院有限公司提出的高安全、紧凑型铅冷快堆方案。为研究SMILE的安全特性,使用系统分析程序ATHLET对其进行典型无保护瞬态热工水力性能分析。结果表明,SMILE在应对典型无保护瞬态事故时具备良好的固有安全特性。

基于PCA的气冷微型堆堆芯在线监测方法研究

先进微型堆的研发面临仅依靠少量堆外探测器信号实现堆芯在线监测的挑战。本研究提出一种通过主成分分析和堆外探测器空间响应函数进行堆芯功率重构和棒位预测的方法,并在气冷微型堆上初步验证其可行性。研究结果表明,通过核设计程序构建不同工况下堆芯节块功率分布数据库,可以选择少于堆外探测器信号个数的主成分实现堆芯功率分布的降维,且样本恢复精度在2.5%以内;为保证主成分的适用性,应使功率分布数据库包含尽量全面的工况因素;堆外探测器响应函数受其与堆芯节块的相对位置影响显著,轴向探测器响应受前后反射层厚度影响明显,径向探测器响应与全堆燃料组件列均有映射关系;节块级功率重构可基于主成分降维和堆外探测器信号通过最小二乘法实现,重构误差在2.9%以内;轴向芯块级功率重构可基于重构的节块级功率通过多项式拟合实现,最大功率因子拟合误差在0.2%以内;棒位预测可通过构建棒位与功率在主成分上的投影系数之间函数映射模型和非线性最小二乘法拟合实现,棒位预测偏差在0.5 cm以内。该堆芯在线监测方法功率重构、棒位预测精度高,不受堆型和工况限制,可应用在各种先进微堆研发中。