Electrosynthesis of H_(2)O_(2)via two-electron oxygen reduction over carbon-based catalysts:From microenvironment control to electrode/reactor design

The electrochemical production of hydrogen peroxide(H_(2)O_(2))by the two-electron oxygen reduction(2e^(-)ORR)process has the advantages of high safety,low energy consumption,and environmental friendliness.For 2e^(-)ORR,the catalyst/electrode is the key component as it strongly affects catalytic performance and cost.Carbon materials have the advantages of high electronic conductivity,good structural stability,easy control of nanostructures,and low cost.Therefore,it has been regarded as a promising catalyst/electrode material for the electrosynthesis of H_(2)O_(2)via 2e^(-)ORR.In addition,studies have also considered the optimization of the liquid/gas interface by tuning the electrode surface,electrolyte pH,and reactor configurations for further improving the activity and selectivity of catalysts.In this review,we provide an in-depth discussion of the recent research on the carbon-based electrocatalysts for 2e^(-)ORR,especially in terms of microenvironment tuning,catalyst/electrode interface engineering,and reactor design for achieving stable and efficient production of H_(2)O_(2).The challenges that we are still facing and the future development prospects will then be concluded,which we believe should help the future development in this field.

High-Con cent rat ion Electrosynthesis of Formic Acid/Formate from CO_(2):Reactor and Electrode Design Strategies

The electrochemical CO_(2)reduction reaction(CO_(2)RR),driven by renewable energy,provides a potential carbon-neutral avenue to convert CO_(2)into valuable fuels and feedstocks.Conversion of CO_(2)into formic acid/formate is considered one of the economical and feasible methods,owing to their high energy densities,and ease of distribution and storage.The separation of formic acid/formate from the reaction mixtures accounts for the majority of the overall CO_(2)RR process cost,while the increment of product concentration can lead to the reduction of separation cost,remarkably.In this paper,we give an overview of recent strategies for highly concentrated formic acid/formate products in CO_(2)RR.CO_(2)RR is a complex process with several different products,as it has different intermediates and reaction pathways.Therefore,this review focuses on recent study strategies that can enhance targeted formic acid/formate yield,such as the all-solid-state reactor design to deliver a high concentration of products during the reduction of CO_(2)in the electrolyzer.Firstly,some novel electrolyzers are introduced as an engineering strategy to improve the concentration of the formic acid/formate and reduce the cost of downstream separations.Also,the design of planar and gas diffusion electrodes(GDEs)with the potential to deliver high-concentration formic acid/formate in CO_(2)RR is summarized.Finally,the existing technological challenges are highlighted,and further research recommendations to achieve high-concentration products in CO_(2)RR.This review can provide some inspiration for future research to further improve the product concentration and economic benefits of CO_(2)RR.

Analysis and design of resistance-wire heater in MOCVD reactor

Metal organic chemical vapor deposition(MOCVD) is a key equipment in the manufacturing of semiconductor optoelectronic devices and microwave devices in industry. Heating system is a vital part of MOCVD. Specific heating device and thermal control technology are needed for each new reactor design. By using resistance-wire heating MOCVD reaction chamber model, thermal analysis and structure optimization of the reactor were developed from the vertical position and the distance between coils of the resistance-wire heater. It is indicated that, within a certain range, the average temperature of the graphite susceptor varies linearly with the vertical distance of heater to susceptor, and with the changed distances between the coils; furthermore, single resistance-wire heater should be placed loosely in the internal and tightly in the external. The modulate accuracy of the temperature field approximately equals the change of the average temperature corresponding to the change of the coil position.

Study on neutronics design of ordered-pebble-bed fluoride-salt- cooled high-temperature experimental reactor

This paper presents a neutronics design of a 10 MW ordered-pebble-bed fluoride-salt-cooled high-temperature experimental reactor. Through delicate layout, a core with ordered arranged pebble bed can be formed,which can keep core stability and meet the space requirements for thermal hydraulics and neutronics measurements.Overall, objectives of the core include inherent safety and sufficient excess reactivity providing 120 effective full power days for experiments. Considering the requirements above, the reactive control system is designed to consist of 16 control rods distributed in the graphite reflector. Combining the large control rods worth about 18000–20000 pcm, molten salt drain supplementary means(-6980 to -3651 pcm) and negative temperature coefficient(-6.32 to -3.80 pcm/K) feedback of the whole core, the reactor can realize sufficient shutdown margin and safety under steady state. Besides, some main physical properties, such as reactivity control, neutron spectrum and flux, power density distribution, and reactivity coefficient,have been calculated and analyzed in this study. In addition, some special problems in molten salt coolant are also considered, including ~6Li depletion and tritium production.

Feasibility neutronic design for the reactor core configurations of a 5 MWth transportable block-type HTR

Small long-life transportable high temperature gas-cooled reactors(HTRs) are interesting because they can safely provide electricity or heat in remote areas or to industrial users in developed or developing countries.This paper presents the neutronic design of the U-Battery,which is a 5 MWth block-type HTR with a fuel lifetime of 5–10 years.Assuming a reactor pressure vessel diameter of less than 3.7 m,some possible reactor core configurations of the 5 MWth U-Battery have been investigated using the TRITON module in SCALE 6.The neutronic analysis shows that Layout 12×2B,a scattering core containing 2 layers of 12 fuel blocks each with 20% enriched235U,reaches a fuel lifetime of 10 effective full power years(EFPYs).When the diameter of the reactor pressure vessel is reduced to 1.8 m,a fuel lifetime of 4 EFPYs will be achieved for the 5 MWth U-Battery with a 25-cm thick graphite side reflector.Layouts 6×3 and 6×4 with a 25-cm thick BeO side reflector achieve a fuel lifetime of 7 and 10 EFPYs,respectively.The comparison of the different core configurations shows that,keeping the number of fuel blocks in the reactor core constant,the annular and scattering core configurations have longer fuel lifetimes and lower fuel cost than the cylindrical ones.Moreover,for the 5 MWth U-Battery,reducing the fuel inventory in the reactor core by decreasing the diameter of fuel kernels and packing fraction of TRISO particles is more effective to lower the fuel cost than decreasing the 235U enrichment.

Neutronic design investigation of a liquid injection-based second shutdown system for a typical research reactor using MCNPX

Safety systems, built on state-of-the-art technology, are essential for achieving acceptable levels of plant safety to minimize hazards to the reactor and the general public. The second shutdown system(SSS) as an engineered safety feature and a part of the reactor protection system(RPS) is a means for rapidly shutting down a nuclear reactor, keeping it in a subcritical state and serving as a backup to the first shutdown system(FSS). In this research, one SSS with two types of optimum chamber designs is proposed that take into account the main current characteristic features of the Tehran research reactor with improvements over earlier designs. They are based on a liquid neutron absorber injection that is preferably different, diverse, and independent from the FSS based on the rod drop mechanism. The major design characteristics of this SSS with two different chambers were investigated using MCNPX 2.6.0 code. The performed calculations showed that the designed SSS is a reliable shutdown system, assuring an appropriate shutdown margin and injection time, with no significant effects on the effective delayed neutron fraction while causing minimal variations to the core structure. Further, the reasonable financial cost and the prolongation of the operation cycle are additional advantages of this design.

The Statistical Experimental Design for Chemical Reactors Modeling

The Statistical Experimental Design techniques are the most powerful tools for the chemical reactors experimental modeling. Empirical models can be formulated for representing the chemical behavior of reactors with the minimal effort in the necessary number of experimental runs, hence, minimizing the consumption of chemicals and the consumption of time due to the reduction in the number of experimental runs and increasing the certainty of the results. Four types of nonthermal plasma reactors were assayed seeking for the highest efficiency in obtaining hydrogen and ethylene. Three different geometries for AC high voltage driven reactors, and only a single geometry for a DC high voltage pulse driven reactor were studied. According to the fundamental principles of chemical kinetics and considering an analogy among the reaction rate and the applied power to the plasma reactor, the four reactors are modeled following the classical chemical reactors design to understand if the behavior of the nonthermal plasma reactors can be regarded as the chemical reactors following the flow patterns of PFR (Plug Flow Reactor) or CSTR (Continuous Stirred Tank Reactor). Dehydrogenation is a common elimination reaction that takes place in nonthermal plasmas. Owing to this characteristic, a paraffinic heavy oil with an average molecular weight corresponding to C15 was used to study the production of light olefins and hydrogen.

Design and Comparative Analysis of Small Modular Reactors for Nuclear Marine Propulsion of a Ship

The fast growth in the size and difficulty of nuclear power plant in the 1970s produced an interest in smaller, modest designs that are intrinsically safe over the usage of design features. With the development of nuclear technology, there is the need for revolution in the Maritime sector, especially the advance marine propulsion. In current years, numerous reactor manufacturers are dynamically improving small modular reactor designs with even superior use of safety features. Several designs integrate the ultimate in greater safety. They totally remove specific accident initiators from the design. Other design features benefit to reduce different types of accident or help to mitigate the accident’s consequences. Although some safety features are mutual to maximum SMR designs, irrespective of the coolant technology, other features are specific to liquid-metal cooled, water, gas, or SMR designs. Results: There have been more reactor concepts investigated in the marine propulsion area by different assemblies and research laboratories than in the power generation field, and much can be learned from their experience for land applications. The extensive use of safety features in SMRs potential to make these power plants extremely vigorous, protecting both the public and the investor. Conclusion: For these two considerations, it is recognized that a nuclear reactor is the ideal engine for naval advanced propulsion. The paper will present the work to analyze the concept design of SMRs and design a modular vessel consisting of a propulsion module.

泳池式低温供热堆用衰减筒的设计

衰减筒是池式低温供热堆的主要部件,其功能是保证堆芯出口的放射性冷却水在衰减筒内的滞留时间不低于100s,使短周期放射性核素在池内大量衰减,从而使一回路的放射性水平显著降低。根据整体布置要求,该衰减筒的筒体结构为不规则扇形结构,并在内部设置有分流板和孔板。其设计工作主要包括结构设计、冷却水衰减时间计算以及结构件的强度分析计算,并通过相关计算结果对设计进行优化。最终的设计结果表明,衰减筒的结构设计满足功能要求,冷却水在衰减筒内的衰减时间不低于100s,且强度分析计算满足设计要求。

Computer Aided Design and Performance Analysis of Inverse Fluidized Bed Biofilm Reactors with Special Reference to Bioplastic Synthesis

Poly Laevo Lactic Acid (PLLA), in spite of being an excellent bioplastic, has exorbitantly high market price due to the high cost of raw material (lactose, glucose, sucrose). Hence, its manufacture is being attempted starting from waste effluents such as cheese whey and molasses. Earlier studies on the same in fluidized bed and semifluidized bed biofilm reactors yielded encouraging results. The present study therefore involves design and analysis of inverse fluidized bed biofilm reactors for lactic acid synthesis. The performance features of the bioreactor have been studied both mathematically as well as experimentally. The inverse fluidized bed biofilm reactor has been found to provide more than 75% conversion of sucrose/lactose even at high capacities (high feed flow rates) exceeding 56,000 L/hr, within a reasonably low reactor volume. The fractional substrate conversion increases, though sluggishly, with increase in feed flow rate due to bed expansion and also with increase in cell mass concentration in biofilm due to enhancement in intrinsic rate of bioconversion. The inverse fluidized bed biofilm reactor of proposed design could be safely recommended for the commercial synthesis of polymer grade lactic acid from waste effluents such as cheese whey and molasses. The low operating cost of the bioreactor (due to downflow mode of operation) enhances the economy of the process. This would also help in significantly lowering the market price of the green plastic (PLLA) and shall promote its large scale manufacture and utilisation.

船用金属氢化物储氢技术研究综述

金属氢化物储氢是一种基于化学吸收原理的氢气储存方法,具有高体积储氢密度和高安全性的特点,在船舶储氢领域的应用潜力备受关注。在此背景下,对于金属氢化物储氢技术在船舶上的应用,有着材料性能、反应器性能、热管理系统、成本等一系列有待研究的问题。首先,对金属氢化物储氢技术进行归纳,总结梳理金属氢化物的工作原理及材料性能方面的研究进展,并介绍金属氢化物在船舶上的应用情况;然后,结合氢能船舶的应用环境及需求,分析金属氢化物储氢技术在船舶上应用的技术、经济可行性,并以满足氢能船舶对氢气储量和放氢速率要求为目标,介绍船用金属氢化物储氢系统的研究,包括储氢系统性能研究、储氢反应器结构、反应器结构优化、耦合船舶燃料电池的热管理系统和储氢系统设计思路;最后,结合上述研究内容,对船用金属氢化物储氢系统的研究方向进行总结与展望。

Engineering design and numerical design for chemical looping combustion reactor: A review

Chemical looping combustion(CLC)has emerged as a cost-effective technology for carbon capture at the combustion source.The reactor,being central to the implementation of CLC,primarily adheres to two technological pathways:the dual fluidized bed reactor and the packed bed reactor.However,the intricate interaction between gas-solid reaction flow and heat/mass transfer processes in these reactors gives rise to diverse operational principles at both macroscopic and microscopic levels across various reactor forms and scales,making performance prediction challenging.Consequently,the rational design of CLC reactors poses a significant challenge in advancing this technology to commercial viability.This article offers an extensive review of the prevailing reactor designs in CLC,delving into reactor characteristics,pivotal aspects of the design process,methodologies,and representative studies in the field.The predominant reactor design approaches are categorized into engineering and numerical methods.The former encompasses phenomenological and similarity analysis methods,whereas the latter consists of macroscopic and computational fluid dynamics simulation methods.Each method possesses its theoretical framework,distinctive characteristics,appropriate applications,and respective advantages and limitations.In practical applications,integrating these aspects is essential.For instance,the engineering design,which is less costly but also less precise,is effective for quickly screening numerous potential design scenarios.In contrast,the numerical design,despite its higher computational demand and greater model complexity,offers improved predictive accuracy and is optimal for validating and refining engineering design solutions.

Calculation and Design of Dry-type Air-core Reactor

Based on the method of compound and additional conditions under the conditions of the equal temperature rise and the equal potential drop (P.D.) of resistance, the application of design software of dry-type air-core reactor is introduced in this thesis. The analytical methods of the inductance are also given. This approach is proved entirely feasible in theory through the simplification with Bartky transformation, and is able to quickly and accurately calculate reactor inductance. This paper presents the analytical methods of the loss of dry-type air-core reactor as well.

实验快堆堆顶固定屏蔽的研制

对实验快堆的堆顶固定屏蔽进行研制,具体包括结构设计、包装设计、焊接工艺、现场安装。采用累计厚度650mm的蛇纹石混凝土,对中子辐射和高温热辐射进行屏蔽。设置厚度145mm的绝热矿渣棉隔热层,强化隔热效果。针对堆顶固定屏蔽分体式结构特点,采用反变形法、辅助横梁等措施,在重力载荷、安装载荷、焊接变形等因素影响下,现场组装后最大中心挠度约为8mm,满足我国实验快堆的屏蔽需求。

田湾核电站堆顶电缆拆装工具的设计与应用

针对田湾核电站1~4号机组反应堆堆顶电缆大修维护仅能通过人力进行拆装且存在所需人力多、耗时长、效率低等问题,为提高设备检修效率,实现设备维护自动化,从实际使用需求出发,通过结构设计、电气设计以及设计计算对堆顶电缆拆装工具进行设计,并在现场验证其高效可用性。

基于生活问题的反应器设计类比教学探索与实践

化学反应工程是一门基于数学模型研究工程问题的基础学科,其中反应器设计是该学科的重要内容。化学反应工程课程团队以生活中的问题“为什么不能狼吞虎咽”导入,将人体的口腔、胃和肠道分别类比为间歇釜式反应器、连续流动釜式反应器、连续流动管式反应器,进而将生活中的问题转化为可量化的化学反应工程问题,以帮助学生理解反应器的结构和特点;同时通过三个相关的例题展开理想反应器设计的教学,从定量的角度回答“为什么不能狼吞虎咽”,从而形成了教学闭环。基于生活问题的类比教学可提高学生的学习兴趣,激发学生的学习内驱力,让学生深刻领悟数学建模的过程,为学生后续学习反应器串联组合的内容打下基础。

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。

液态燃料熔盐堆停堆后主回路自然循环特性研究

液态燃料熔盐堆在停堆后通过建立熔盐自然循环,将堆芯中的衰变余热非能动地传导至环境,但主回路中熔盐的衰变发热将影响回路排热能力。为得到该种非能动系统的热工特性,给出自然循环模型的分析依据,明确熔盐物性、回路结构和设备阻力系数K对自然循环的影响。利用自编Python分析程序,建立液态燃料熔盐堆的非能动余热排出回路自然循环模型,分析回路中熔盐的温度分布;考察反应堆堆芯在余热排出过程中,关键因素对余热排出能力的影响规律。研究结果表明:当系统回路中熔盐存在衰变热时,堆芯熔盐可通过自然循环带走的热量相对减少。根据重要性分析结果,燃料盐密度、比热容和冷热芯高度差等是影响自然循环能力的重要参数,当这三个参数值分别增加15%时,余热排出能力分别提升26.02%、15.00%和18.59%。由此可见,熔盐物性、回路结构和设备阻力系数均会影响自然循环排热能力。

大肠杆菌高密度发酵制药废水处理工艺设计实例

大肠杆菌高密度发酵制药的废水包括发酵产生的工艺废水和清洗、冷却产生的低污染废水,前者水量小但污染物含量高,后者量大但污染物含量低。分析比较吹脱法、折点加氯法、生物法、离子交换法和化学沉淀法,确定对污染性强的工艺废水采用化学沉淀法、活性污泥法相结合的处理工艺,先MAP沉淀除氨脱磷,再用低污染废水10倍稀释后进行SBR生化处理,达标排放。MAP沉淀除氨脱磷药剂选用氯化镁和磷酸氢二钠,pH值9.5,投药比采用n(Mg^(2+))∶n(NH_(4)^(+))∶n(PO_(4)^(3-))=1.2∶1∶1,氨氮去除率达83%,COD Cr的去除率达19%,稀释10倍后氮磷含量符合SBR生化处理要求。该工艺污水综合处理成本约为51.8元/m^(3),但处理量小,污水处理总费用约为88元/d,综合费用低,且副产物MAP可用作肥料。

冶金固废提锌技术的发展现状与展望

传统的固废直接送往铁前工艺循环,灰泥中的锌被直接引入高炉,不仅影响运行炉况,还会富集导致设备损坏和综合生产效率下降。因此,探索有效的提锌工艺,减少锌在高炉中的富集,对于提高钢铁生产的经济性和环保性具有重要意义。本文基于钢铁冶金灰泥提锌的化学反应和动力学、热力学特征,系统分析了包括回转窑法、转底炉法及多级浸出法等主要提锌工艺的特点及其适用性。现有传统工艺虽然具有一定的技术优势,但在实际应用中仍存在能耗高、操作复杂和环境影响大的问题,因而提出了优化反应器设计、引入预处理技术和智能化控制系统以及多工艺集成的改进措施,以提高综合效率。未来的冶金灰泥提锌技术将向更高效、环保和智能化的方向发展,推动钢铁行业的可持续发展。