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.

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.

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.

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。

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。

新型欧姆加热式反应器强化甲烷蒸汽重整的过程分析和优化

传统甲烷蒸汽重整(SMR)反应器(cSMR反应器)中容易出现较大的径向温度梯度,增加了催化剂积炭失活的风险。提出了一种新型的含内外管欧姆加热蒸汽重整固定床反应器(eSMR反应器),以欧姆加热替代了传统工业反应器的燃烧供热方式。通过二维拟均相固定床反应器模拟,比较了eSMR与cSMR反应器的性能差异,分析了eSMR反应器结构及操作条件对其性能的影响。结果表明,相比于cSMR,eSMR反应器出口的平均甲烷转化率和平均温度分别高出26.6%和121 K,且径向温度分布更加均匀;eSMR反应器的内外管直径之比为0.589时,其径向温度梯度最小;增加入口温度、加热电压和水碳比均会提高eSMR反应器出口的平均甲烷转化率和平均温度,增加入口压力的影响相反。本研究可为欧姆加热蒸汽重整反应器的开发提供一定的借鉴。

生物质双流化床气固流动特性研究与数值模拟

依靠双流化床冷态装置考察流化风和松动风的流量对流化床流化形式、返料器料封高度以及固体循环量的影响。当流化风流量为5 m3/h时,流化床气化器内颗粒呈鼓泡流化。返料器料位与返料器两侧压差有关,压差越大,返料器内料封高度越低。气体反窜时返料器两侧压差变小,料位逐渐升高。不改变其他条件,在下松动风流量为3 m^(3)/h及以下时,增大松动风流量,颗粒循环量逐渐增加,一定条件下固体颗粒循环量达到最大为6.72 kg/h。对装置进行数值模拟,结果显示颗粒的流化形式与实验一致。

核主泵水力优化技术与水力稳定性研究进展

随着人们对能源安全、环境保护和可持续发展的关注不断增加,核能作为一种清洁、高效的能源形式备受瞩目。核主泵作为核电站的重要组成部分,其水力性能的好坏关系到整个核电站是否能够长期安全稳定高效的运行。本文针对核主泵水力优化技术与水力稳定性的研究进展开展论述,介绍了核主泵水力性能的影响因素及其研究方法。以水力优化设计与压力脉动特性等方面为切入点深入探讨了核主泵水力优化技术与水力稳定性的研究现状,并简要介绍了核主泵压力脉动的形成原因;总结了已有的研究成果,并根据现有的研究基础展望了核主泵未来的技术发展趋势。

基于多目标进化算法的反应堆辐射屏蔽优化方法研究

新型核能与核动力装置的发展对辐射屏蔽设计方法提出了更高要求。面对空间堆、船用堆等装置的小型化、轻量化设计需求,传统辐射屏蔽多目标优化方法存在优化目标少、优化参数单一、全局性差等缺陷,难以满足辐射屏蔽智能设计的需求。本文基于第三代非支配排序遗传算法和改进多目标人工蜂群算法开展面向反应堆屏蔽层重量、体积和特定区域辐射剂量等多目标约束条件下的辐射屏蔽优化方法研究,并对各算法的优化性能、优化方案进行对比分析。结果表明,本文方法相较于传统屏蔽智能设计方法展现了更好的优化性能,并在实际工程问题中体现了可靠性,可为辐射屏蔽设计优化提供新思路。

碱式碳酸镁射流碳化反应器优化设计

针对传统碳化反应器气、液接触面积小、碳化反应不完全、混合不均匀等问题,提出将射流器应用于碱式碳酸镁的碳化工艺中,利用射流器特有的结构增大气-液两相流体的接触面积,从而使气、液混合均匀。采用数值模拟的方法探究了碳化反应器的结构对混合效果及气相浓度分布的影响,同时,采用正交设计的方法对碳化反应器进行结构优化。结果表明,碳化反应器的高径比及射流器喷嘴在碳化反应器中的位置对混合效果影响较大,而射流器喷射角对其混合效果影响较小。确定碳化反应器的最佳高径比为3,射流器最佳喷嘴位置位于碳化反应器H/2处,射流器最佳喷射角为22°。

某全地埋污水处理厂的设计思考

某全地埋污水处理厂设计规模为5万m^(3)/d,近期按2.5万m^(3)/d实施。根据进出水水质和用地情况,污水处理采用改良AAO+MBR工艺,出水达到“准Ⅳ类”标准后用于周边绿地浇灌、道路冲洗和景观河道补水。污泥经浓缩脱水后达到80%含水率后,送到城市污泥处置中心进行进一步处置。通过详细介绍某全地埋污水处理厂的总体工艺设计路线,并对建设型式、处理工艺、雨季抗冲击负荷、防洪、防淹、消防防火分区的划分、除臭系统设计等重难点问题进行思考总结,为其他类似污水处理厂项目的建设提供借鉴。

基于ACE Reactor的BSC功能测试系统设计

GSM通信工程迫切需要对BSC系统进行各种功能测试,而软硬件环境的多样性和异构性,使得BSC平台架构上的测试相当困难。为了减少整个通信软件的成本,简化各种配置的复杂性,利用ACE中间件丰富的组件和Reactor框架设计模式,使用软件仿真硬件所实现的逻辑。通过引入两个插桩,来仿真两个物理的NetHawkServer卡,在LinuxOS下建立了基于IP通信的功能测试环境。实验证明了新测试系统的可靠性和健壮性,并解决了昂贵测试硬件短缺的问题。