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 Select The Recent Technological Development of Intelligent Mining in China Jinhua Wang,Zenghua Huang Engineering    2017, 3 (4): 439-444.   DOI: 10.1016/J.ENG.2017.04.003 Abstract   HTML   PDF (1658KB) In the last five years, China has seen the technological development of intelligent mining and the application of the longwall automation technology developed by the Longwall Automation Steering Committee. This paper summarizes this great achievement, which occurred during the 12th Five-Year Plan (2011–2015), and which included the development of a set of intelligent equipment for hydraulic-powered supports, information transfers, dynamic decision-making, performance coordination, and the achievement of a high level of reliability despite difficult conditions. Within China, the intelligent system of a set of hydraulic-powered supports was completed, with our own intellectual property rights. An intelligent mining model was developed that permitted unmanned operation and single-person inspection on the work face. With these technologies, the number of miners on the work face can now be significantly reduced. Miners are only required to monitor mining machines on the roadway or at the surface control center, since intelligent mining can be applied to extract middle-thick or thick coal seams. As a result, miners’ safety has been improved. Finally, this paper discusses the prospects and challenges of intelligent mining over the next ten years.
 Select Advances in Cost-Efficient Thin-Film Photovoltaics Based on Cu(In,Ga)Se2 Michael Powalla,Stefan Paetel,Dimitrios Hariskos,Roland Wuerz,Friedrich Kessler,Peter Lechner,Wiltraud Wischmann,Theresa Magorian Friedlmeier Engineering    2017, 3 (4): 445-451.   DOI: 10.1016/J.ENG.2017.04.015 Abstract   HTML   PDF (3655KB) In this article, we discuss the leading thin-film photovoltaic (PV) technology based on the Cu(In,Ga)Se2 (CIGS) compound semiconductor. This contribution includes a general comparison with the conventional Si-wafer-based PV technology and discusses the basics of the CIGS technology as well as advances in world-record-level conversion efficiency, production, applications, stability, and future developments with respect to a flexible product. Once in large-scale mass production, the CIGS technology has the highest potential of all PV technologies for cost-efficient clean energy generation.
 Select Review on Alkali Element Doping in Cu(In,Ga)Se2 Thin Films and Solar Cells Yun Sun,Shuping Lin,Wei Li,Shiqing Cheng,Yunxiang Zhang,Yiming Liu,Wei Liu Engineering    2017, 3 (4): 452-459.   DOI: 10.1016/J.ENG.2017.04.020 Abstract   HTML   PDF (2517KB) This paper reviews the development history of alkali element doping on Cu(In,Ga)Se2 (CIGS) solar cells and summarizes important achievements that have been made in this field. The influences of incorporation strategies on CIGS absorbers and device performances are also reviewed. By analyzing CIGS surface structure and electronic property variation induced by alkali fluoride (NaF and KF) post-deposition treatment (PDT), we discuss and interpret the following issues: ① The delamination of CIGS thin films induced by Na incorporation facilitates CuInSe2 formation and inhibits Ga during low-temperature co-evaporation processes. ② The mechanisms of carrier density increase due to defect passivation by Na at grain boundaries and the surface. ③ A thinner buffer layer improves the short-circuit current without open-circuit voltage loss. This is attributed not only to better buffer layer coverage in the early stage of the chemical bath deposition process, but also to higher donor defect ($CdCu+$) density, which is transferred from the acceptor defect ($VCu−$) and strengthens the buried homojunction. ④ The KF-PDT-induced lower valence band maximum at the absorber surface reduces the recombination at the absorber/buffer interface, which improves the open-circuit voltage and the fill factor of solar cells.
 Select An Internet of Energy Things Based on Wireless LPWAN Yonghua Song,Jin Lin,Ming Tang,Shufeng Dong Engineering    2017, 3 (4): 460-466.   DOI: 10.1016/J.ENG.2017.04.011 Abstract   HTML   PDF (1225KB) Under intense environmental pressure, the global energy sector is promoting the integration of renewable energy into interconnected energy systems. The demand-side management (DSM) of energy systems has drawn considerable industrial and academic attention in attempts to form new flexibilities to respond to variations in renewable energy inputs to the system. However, many DSM concepts are still in the experimental demonstration phase. One of the obstacles to DSM usage is that the current information infrastructure was mainly designed for centralized systems, and does not meet DSM requirements. To overcome this barrier, this paper proposes a novel information infrastructure named the Internet of Energy Things (IoET) in order to make DSM practicable by basing it on the latest wireless communication technology: the low-power wide-area network (LPWAN). The primary advantage of LPWAN over general packet radio service (GPRS) and area Internet of Things (IoT) is its wide-area coverage, which comes with minimum power consumption and maintenance costs. Against this background, this paper briefly reviews the representative LPWAN technologies of narrow-band Internet of Things (NB-IoT) and Long Range (LoRa) technology, and compares them with GPRS and area IoT technology. Next, a wireless-to-cloud architecture is proposed for the IoET, based on the main technical features of LPWAN. Finally, this paper looks forward to the potential of IoET in various DSM application scenarios.
 Select Particle Size and Crystal Phase Effects in Fischer-Tropsch Catalysts Jin-Xun Liu,Peng Wang,Wayne Xu,Emiel J. M. Hensen Engineering    2017, 3 (4): 467-476.   DOI: 10.1016/J.ENG.2017.04.012 Abstract   HTML   PDF (2496KB) Fischer-Tropsch synthesis (FTS) is an increasingly important approach for producing liquid fuels and chemicals via syngas—that is, synthesis gas, a mixture of carbon monoxide and hydrogen—generated from coal, natural gas, or biomass. In FTS, dispersed transition metal nanoparticles are used to catalyze the reactions underlying the formation of carbon-carbon bonds. Catalytic activity and selectivity are strongly correlated with the electronic and geometric structure of the nanoparticles, which depend on the particle size, morphology, and crystallographic phase of the nanoparticles. In this article, we review recent works dealing with the aspects of bulk and surface sensitivity of the FTS reaction. Understanding the different catalytic behavior in more detail as a function of these parameters may guide the design of more active, selective, and stable FTS catalysts.
 Select CCS Research Development and Deployment in a Clean Energy Future: Lessons from Australia over the Past Two Decades Peter J. Cook Engineering    2017, 3 (4): 477-484.   DOI: 10.1016/J.ENG.2017.04.014 Abstract   HTML   PDF (1065KB) There is widespread, though by no means universal, recognition of the importance of carbon capture and storage (CCS) as a carbon mitigation technology. However, the rate of deployment does not match what is required for global temperatures to stay well below 2?°C. Although some consider the hurdles to achieving the widespread application of CCS to be almost insurmountable, a more optimistic view is that a great deal is now known about CCS through research, demonstration, and deployment. We know how to do it; we are confident it can be done safely and effectively; we know what it costs; and we know that costs are decreasing and will continue to do so. We also know that the world will need CCS as long as countries, companies, and communities continue to use fossil fuels for energy and industrial processes. What is lacking are the necessary policy drivers, along with a technology-neutral approach to decrease carbon emissions in a cost-effective and timely manner while retaining the undoubted benefits of ready access to reliable and secure electricity and energy-intensive industrial products. In this paper, Australia is used as an example of what has been undertaken in CCS over the past 20 years, particularly in research and demonstration, but also in international collaboration. Progress in the large-scale deployment of CCS in Australia has been too slow. However, the world’s largest storage project will soon be operational in Australia as part of the Gorgon liquefied natural gas (LNG) project, and investigations are underway into several large-scale CCS Flagship program opportunities. The organization and progress of the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) Otway Project, which is currently Australia’s only operational storage project, is discussed in some detail because of its relevance to the commercial deployment of CCS. The point is made that there is scope for building on this Otway activity to investigate more broadly (through the proposed Otway Stage 3 and Deep Earth Energy and Environment Programme (AusDEEP)) the role of the subsurface in carbon reduction. There are challenges ahead if CCS is to be deployed as widely as bodies such as the International Energy Agency (IEA) and the Intergovernmental Panel on Climate Change (IPCC) consider to be necessary. Closer international collaboration in CCS will be essential to meeting that challenge.
 Select Development of CO2 Selective Poly(Ethylene Oxide)-Based Membranes: From Laboratory to Pilot Plant Scale Torsten Brinkmann,Jelena Lillepärg,Heiko Notzke,Jan Pohlmann,Sergey Shishatskiy,Jan Wind,Thorsten Wolff Engineering    2017, 3 (4): 485-493.   DOI: 10.1016/J.ENG.2017.04.004 Abstract   HTML   PDF (2074KB) Membrane gas separation is one of the most promising technologies for the separation of carbon dioxide (CO2) from various gas streams. One application of this technology is the treatment of flue gases from combustion processes for the purpose of carbon capture and storage. For this application, poly(ethylene oxide)-containing block copolymers such as Pebax® or PolyActive™ polymer are well suited. The thin-film composite membrane that is considered in this overview employs PolyActive™ polymer as a selective layer material. The membrane shows excellent CO2 permeances of up to 4 m3(STP)·(m2·h·bar)−1 (1 bar= 105 Pa) at a carbon dioxide/nitrogen (CO2/N2) selectivity exceeding 55 at ambient temperature. The membrane can be manufactured reproducibly on a pilot scale and mounted into flat-sheet membrane modules of different designs. The operating performance of these modules can be accurately predicted by specifically developed simulation tools, which employ single-gas permeation data as the only experimental input. The performance of membranes and modules was investigated in different pilot plant studies, in which flue gas and biogas were used as the feed gas streams. The investigated processes showed a stable separation performance, indicating the applicability of PolyActive™ polymer as a membrane material for industrial-scale gas processing.
 Select On Advanced Control Methods toward Power Capture and Load Mitigation in Wind Turbines Yuan Yuan,Jiong Tang Engineering    2017, 3 (4): 494-503.   DOI: 10.1016/J.ENG.2017.04.023 Abstract   HTML   PDF (2089KB) This article provides a survey of recently emerged methods for wind turbine control. Multivariate control approaches to the optimization of power capture and the reduction of loads in components under time-varying turbulent wind fields have been under extensive investigation in recent years. We divide the related research activities into three categories: modeling and dynamics of wind turbines, active control of wind turbines, and passive control of wind turbines. Regarding turbine dynamics, we discuss the physical fundamentals and present the aeroelastic analysis tools. Regarding active control, we review pitch control, torque control, and yaw control strategies encompassing mathematical formulations as well as their applications toward different objectives. Our survey mostly focuses on blade pitch control, which is considered one of the key elements in facilitating load reduction while maintaining power capture performance. Regarding passive control, we review techniques such as tuned mass dampers, smart rotors, and microtabs. Possible future directions are suggested.
 Select Flow-Induced Instabilities in Pump-Turbines in China Zhigang Zuo,Shuhong Liu Engineering    2017, 3 (4): 504-511.   DOI: 10.1016/J.ENG.2017.04.010 Abstract   HTML   PDF (20623KB) The stability of pump-turbines is of great importance to the operation of pumped storage power (PSP) stations. Both hydraulic instabilities and operational instabilities have been reported in PSP stations in China. In order to provide a reference to the engineers and scientists working on pump-turbines, this paper summarizes the hydraulic instabilities and performance characteristics that promote the operational instabilities encountered in pump-turbine operations in China. Definitions, analytical methods, numerical and experimental studies, and main results are clarified. Precautions and countermeasures are also provided based on a literature review. The gaps between present studies and the need for engineering practice are pointed out.
 Select An Empirical Study on China’s Energy Supply-and-Demand Model Considering Carbon Emission Peak Constraints in 2030 Jinhang Chen Engineering    2017, 3 (4): 512-517.   DOI: 10.1016/J.ENG.2017.04.019 Abstract   HTML   PDF (1234KB) China’s energy supply-and-demand model and two related carbon emission scenarios, including a planned peak scenario and an advanced peak scenario, are designed taking into consideration China’s economic development, technological progress, policies, resources, environmental capacity, and other factors. The analysis of the defined scenarios provides the following conclusions: Primary energy and power demand will continue to grow leading up to 2030, and the growth rate of power demand will be much higher than that of primary energy demand. Moreover, low carbonization will be a basic feature of energy supply-and-demand structural changes, and non-fossil energy will replace oil as the second largest energy source. Finally, energy-related carbon emissions could peak in 2025 through the application of more efficient energy consumption patterns and more low-carbon energy supply modes. The push toward decarbonization of the power industry is essential for reducing the peak value of carbon emissions.
 Select Computational Tools for the Integrated Design of Advanced Nuclear Reactors Nicholas W. Touran,John Gilleland,Graham T. Malmgren,Charles Whitmer,William H. Gates III Engineering    2017, 3 (4): 518-526.   DOI: 10.1016/J.ENG.2017.04.016 Abstract   HTML   PDF (1656KB) Advanced nuclear reactors offer safe, clean, and reliable energy at the global scale. The development of such devices relies heavily upon computational models, from the pre-conceptual stages through detailed design, licensing, and operation. An integrated reactor modeling framework that enables seamless communication, coupling, automation, and continuous development brings significant new capabilities and efficiencies to the practice of reactor design. In such a system, key performance metrics (e.g., optimal fuel management, peak cladding temperature in design-basis accidents, levelized cost of electricity) can be explicitly linked to design inputs (e.g., assembly duct thickness, tolerances), enabling an exceptional level of design consistency. Coupled with high-performance computing, thousands of integrated cases can be executed simultaneously to analyze the full system, perform complete sensitivity studies, and efficiently and robustly evaluate various design tradeoffs. TerraPower has developed such a tool—the Advanced Reactor Modeling Interface (ARMI) code system—and has deployed it to support the TerraPower Traveling Wave Reactor design and other innovative energy products currently under development. The ARMI code system employs pre-existing tools with strong pedigrees alongside many new physics and data management modules necessary for innovative design. Verification and validation against previous and new physical measurements, which remain an essential element of any sound design, are being carried out. This paper summarizes the integrated core engineering tools and practices in production at TerraPower.
 Select Some Challenges of Deep Mining Charles Fairhurst Engineering    2017, 3 (4): 527-537.   DOI: 10.1016/J.ENG.2017.04.017 Abstract   HTML   PDF (4649KB) An increased global supply of minerals is essential to meet the needs and expectations of a rapidly rising world population. This implies extraction from greater depths. Autonomous mining systems, developed through sustained R&D by equipment suppliers, reduce miner exposure to hostile work environments and increase safety. This places increased focus on “ground control” and on rock mechanics to define the depth to which minerals may be extracted economically. Although significant efforts have been made since the end of World War II to apply mechanics to mine design, there have been both technological and organizational obstacles. Rock in situ is a more complex engineering material than is typically encountered in most other engineering disciplines. Mining engineering has relied heavily on empirical procedures in design for thousands of years. These are no longer adequate to address the challenges of the 21st century, as mines venture to increasingly greater depths. The development of the synthetic rock mass (SRM) in 2008 provides researchers with the ability to analyze the deformational behavior of rock masses that are anisotropic and discontinuous—attributes that were described as the defining characteristics of in situ rock by Leopold Müller, the president and founder of the International Society for Rock Mechanics (ISRM), in 1966. Recent developments in the numerical modeling of large-scale mining operations (e.g., caving) using the SRM reveal unanticipated deformational behavior of the rock. The application of massive parallelization and cloud computational techniques offers major opportunities: for example, to assess uncertainties in numerical predictions; to establish the mechanics basis for the empirical rules now used in rock engineering and their validity for the prediction of rock mass behavior beyond current experience; and to use the discrete element method (DEM) in the optimization of deep mine design. For the first time, mining—and rock engineering—will have its own mechanics-based “laboratory.” This promises to be a major tool in future planning for effective mining at depth. The paper concludes with a discussion of an opportunity to demonstrate the application of DEM and SRM procedures as a laboratory, by back-analysis of mining methods used over the 80-year history of the Mount Lyell Copper Mine in Tasmania.
 Select Monitoring, Warning, and Control of Rockburst in Deep Metal Mines Xia-Ting Feng,Jianpo Liu,Bingrui Chen,Yaxun Xiao,Guangliang Feng,Fengpeng Zhang Engineering    2017, 3 (4): 538-545.   DOI: 10.1016/J.ENG.2017.04.013 Abstract   HTML   PDF (30146KB) This paper reviews the recent achievements made by our team in the mitigation of rockburst risk. It includes the development of neural network modeling on rockburst risk assessment for deep gold mines in South Africa, an intelligent microseismicity monitoring system and sensors, an understanding of the rockburst evolution process using laboratory and in situ tests and monitoring, the establishment of a quantitative warning method for the location and intensities of different types of rockburst, and the development of measures for the dynamic control of rockburst. The mitigation of rockburst at the Hongtoushan copper mine is presented as an illustrative example.
 Select Opportunities and Challenges in Deep Mining: A Brief Review Pathegama G. Ranjith,Jian Zhao,Minghe Ju,Radhika V. S. De Silva,Tharaka D. Rathnaweera,Adheesha K. M. S. Bandara Engineering    2017, 3 (4): 546-551.   DOI: 10.1016/J.ENG.2017.04.024 Abstract   HTML   PDF (2003KB) Mineral consumption is increasing rapidly as more consumers enter the market for minerals and as the global standard of living increases. As a result, underground mining continues to progress to deeper levels in order to tackle the mineral supply crisis in the 21st century. However, deep mining occurs in a very technical and challenging environment, in which significant innovative solutions and best practice are required and additional safety standards must be implemented in order to overcome the challenges and reap huge economic gains. These challenges include the catastrophic events that are often met in deep mining engineering: rockbursts, gas outbursts, high in situ and redistributed stresses, large deformation, squeezing and creeping rocks, and high temperature. This review paper presents the current global status of deep mining and highlights some of the newest technological achievements and opportunities associated with rock mechanics and geotechnical engineering in deep mining. Of the various technical achievements, unmanned working-faces and unmanned mines based on fully automated mining and mineral extraction processes have become important fields in the 21st century.
 Select The Use of Data Mining Techniques in Rockburst Risk Assessment Luis Ribeiro e Sousa, Tiago Miranda, Rita Leal e Sousa, Joaquim Tinoco Engineering    2017, 3 (4): 552-558.   DOI: 10.1016/J.ENG.2017.04.002 Abstract   HTML   PDF (1307KB) Rockburst is an important phenomenon that has affected many deep underground mines around the world. An understanding of this phenomenon is relevant to the management of such events, which can lead to saving both costs and lives. Laboratory experiments are one way to obtain a deeper and better understanding of the mechanisms of rockburst. In a previous study by these authors, a database of rockburst laboratory tests was created; in addition, with the use of data mining (DM) techniques, models to predict rockburst maximum stress and rockburst risk indexes were developed. In this paper, we focus on the analysis of a database of in situ cases of rockburst in order to build influence diagrams, list the factors that interact in the occurrence of rockburst, and understand the relationships between these factors. The in situ rockburst database was further analyzed using different DM techniques ranging from artificial neural networks (ANNs) to naive Bayesian classifiers. The aim was to predict the type of rockburst—that is, the rockburst level—based on geologic and construction characteristics of the mine or tunnel. Conclusions are drawn at the end of the paper.
 Select Key Technology Research on the Efficient Exploitation and Comprehensive Utilization of Resources in the Deep Jinchuan Nickel Deposit Zhiqiang Yang Engineering    2017, 3 (4): 559-566.   DOI: 10.1016/J.ENG.2017.04.021 Abstract   HTML   PDF (2291KB) To understand the resource features and geology in the deep Jinchuan nickel deposit, difficult geological conditions were systematically analyzed, including high stress, fragmentized ore rock, prevalent deformation, difficult tunnel support, complicated rock mechanics, and low mining recovery. An integrated technology package was built for safe, efficient, and continuous mining in a deep, massive, and complex nickel and cobalt mine. This was done by the invention of a large-area continuous mining method with honeycomb drives; the establishment of ground control theory and a technology package for high-stress and fragmented ore rock; and the development of a new type of backfilling cement material, along with a deep backfilling technology that comprises the pipeline transport of high-density slurry with coarse aggregates. In this way, good solutions to existing problems were found to permit the efficient exploitation and comprehensive utilization of the resources in the deep Jinchuan nickel mine. In addition, a technological demonstration in an underground mine was performed using the cemented undercut-and-fill mining method for stressful, fragmented, and rheological rock.
 Select Insights into the Organotemplate-Free Synthesis of Zeolite Catalysts Yeqing Wang,Qinming Wu,Xiangju Meng,Feng-Shou Xiao Engineering    2017, 3 (4): 567-574.   DOI: 10.1016/J.ENG.2017.03.029 Abstract   HTML   PDF (3194KB) As the most important nanoporous material, zeolites, which have intricate micropores, are essential heterogeneous catalysts in industrial processes. Zeolites are generally synthesized with organic templates under hydrothermal conditions; however, this method is environmentally unfriendly and costly due to the formation of harmful gases and polluted water. This article briefly summarizes the role of organic templates and describes designed routes for the organotemplate-free synthesis of zeolites, aided by zeolite seeds and zeolite seeds solution. Furthermore, this review explicates that the micropore volume decreases with an increase of the Si/Al ratios in the organotemplate-free synthesis of zeolite products, where Na+ exists as an alkali cation. This feature is very important in directing the synthesis of zeolite catalysts with controllable Si/Al ratios under organotemplate-free conditions, and is thus important for the efficient design of zeolites.
 Select Improved Oxygen Evolution Kinetics and Surface States Passivation of Ni-Bi Co-Catalyst for a Hematite Photoanode Ke Dang,Tuo Wang,Chengcheng Li,Jijie Zhang,Shanshan Liu,Jinlong Gong Engineering    2017, 3 (3): 285-289.   DOI: 10.1016/J.ENG.2017.03.005 Abstract   HTML   PDF (1314KB) This paper describes the combinational surface kinetics enhancement and surface states passivation of nickel-borate (Ni-Bi) co-catalyst for a hematite (Fe2O3) photoanode. The Ni-Bi-modified Fe2O3 photoanode exhibits a cathodic onset potential shift of 230 mV and a 2.3-fold enhancement of the photocurrent at 1.23 V, versus the reversible hydrogen electrode (RHE). The borate (Bi) in the Ni-Bi film promotes the release of protons for the oxygen evolution reaction (OER).
 Select Membrane Engineering for Green Process Engineering Francesca Macedonio,Enrico Drioli Engineering    2017, 3 (3): 290-298.   DOI: 10.1016/J.ENG.2017.03.026 Abstract   HTML   PDF (693KB) Green process engineering, which is based on the principles of the process intensiﬁcation strategy, can provide an important contribution toward achieving industrial sustainable development. Green process engineering refers to innovative equipment and process methods that are expected to bring about substantial improvements in chemical and any other manufacturing and processing aspects. It includes decreasing production costs, equipment size, energy consumption, and waste generation, and improving remote control, information ﬂuxes, and process ﬂexibility. Membrane-based technology assists in the pursuit of these principles, and the potential of membrane operations has been widely recognized in the last few years. This work starts by presenting an overview of the membrane operations that are utilized in water treatment and in the production of energy and raw materials. Next, it describes the potential advantages of innovative membrane-based integrated systems. A case study on an integrated membrane system (IMS) for seawater desalination coupled with raw materials production is presented. The aim of this work is to show how membrane systems can contribute to the realization of the goals of zero liquid discharge (ZLD), total raw materials utilization, and low energy consumption.
 Select A Technological Overview of Biogas Production from Biowaste Spyridon Achinas,Vasileios Achinas,Gerrit Jan Willem Euverink Engineering    2017, 3 (3): 299-307.   DOI: 10.1016/J.ENG.2017.03.002 Abstract   HTML   PDF (1252KB) The current irrational use of fossil fuels and the impact of greenhouse gases on the environment are driving research into renewable energy production from organic resources and waste. The global energy demand is high, and most of this energy is produced from fossil resources. Recent studies report that anaerobic digestion (AD) is an efficient alternative technology that combines biofuel production with sustainable waste management, and various technological trends exist in the biogas industry that enhance the production and quality of biogas. Further investments in AD are expected to meet with increasing success due to the low cost of available feedstocks and the wide range of uses for biogas (i.e., for heating, electricity, and fuel). Biogas production is growing in the European energy market and offers an economical alternative for bioenergy production. The objective of this work is to provide an overview of biogas production from lignocellulosic waste, thus providing information toward crucial issues in the biogas economy.
 Select Design of Photobioreactors for Mass Cultivation of Photosynthetic Organisms Qingshan Huang,Fuhua Jiang,Lianzhou Wang,Chao Yang Engineering    2017, 3 (3): 318-329.   DOI: 10.1016/J.ENG.2017.03.020 Abstract   HTML   PDF (1481KB) Photosynthetic microorganisms are important bioresources for producing desirable and environmentally benign products, and photobioreactors (PBRs) play important roles in these processes. Designing PBRs for photocatalysis is still challenging at present, and most reactors are designed and scaled up using semi-empirical approaches. No appropriate types of PBRs are available for mass cultivation due to the reactors’ high capital and operating costs and short lifespan, which are mainly due to a current lack of deep understanding of the coupling of light, hydrodynamics, mass transfer, and cell growth in efficient reactor design. This review provides a critical overview of the key parameters that influence the performance of the PBRs, including light, mixing, mass transfer, temperature, pH, and capital and operating costs. The lifespan and the costs of cleaning and temperature control are also emphasized for commercial exploitation. Four types of PBRs—tubular, plastic bag, column airlift, and flat-panel airlift reactors are recommended for large-scale operations. In addition, this paper elaborates the modeling of PBRs using the tools of computational fluid dynamics for rational design. It also analyzes the difficulties in the numerical simulation, and presents the prospect for mechanism-based models.
 Select Fluidized-Bed Bioreactor Applications for Biological Wastewater Treatment: A Review of Research and Developments Michael J. Nelson,George Nakhla,Jesse Zhu Engineering    2017, 3 (3): 330-342.   DOI: 10.1016/J.ENG.2017.03.021 Abstract   HTML   PDF (980KB) Wastewater treatment is a process that is vital to protecting both the environment and human health. At present, the most cost-effective way of treating wastewater is with biological treatment processes such as the activated sludge process, despite their long operating times. However, population increases have created a demand for more efficient means of wastewater treatment. Fluidization has been demonstrated to increase the efficiency of many processes in chemical and biochemical engineering, but it has not been widely used in large-scale wastewater treatment. At the University of Western Ontario, the circulating fluidized-bed bioreactor (CFBBR) was developed for treating wastewater. In this process, carrier particles develop a biofilm composed of bacteria and other microbes. The excellent mixing and mass transfer characteristics inherent to fluidization make this process very effective at treating both municipal and industrial wastewater. Studies of lab- and pilot-scale systems showed that the CFBBR can remove over 90% of the influent organic matter and 80% of the nitrogen, and produces less than one-third as much biological sludge as the activated sludge process. Due to its high efficiency, the CFBBR can also be used to treat wastewaters with high organic solid concentrations, which are more difficult to treat with conventional methods because they require longer residence times; the CFBBR can also be used to reduce the system size and footprint. In addition, it is much better at handling and recovering from dynamic loadings (i.e., varying influent volume and concentrations) than current systems. Overall, the CFBBR has been shown to be a very effective means of treating wastewater, and to be capable of treating larger volumes of wastewater using a smaller reactor volume and a shorter residence time. In addition, its compact design holds potential for more geographically localized and isolated wastewater treatment systems.
 Select Recent Developments in the Crystallization Process: Toward the Pharmaceutical Industry Zhenguo Gao,Sohrab Rohani,Junbo Gong,Jingkang Wang Engineering    2017, 3 (3): 343-353.   DOI: 10.1016/J.ENG.2017.03.022 Abstract   HTML   PDF (2534KB) Crystallization is one of the oldest separation and purification unit operations, and has recently contributed to significant improvements in producing higher-value products with specific properties and in building efficient manufacturing processes. In this paper, we review recent developments in crystal engineering and crystallization process design and control in the pharmaceutical industry. We systematically summarize recent methods for understanding and developing new types of crystals such as co-crystals, polymorphs, and solvates, and include several milestones such as the launch of the first co-crystal drug, Entresto (Novartis), and the continuous manufacture of Orkambi (Vertex). Conventional batch and continuous processes, which are becoming increasingly mature, are being coupled with various control strategies and the recently developed crystallizers are thus adapting to the needs of the pharmaceutical industry. The development of crystallization process design and control has led to the appearance of several new and innovative crystallizer geometries for continuous operation and improved performance. This paper also reviews major recent progress in the area of process analytical technology.
 Select Progress of Pharmaceutical Continuous Crystallization Dejiang Zhang,Shijie Xu,Shichao Du,Jingkang Wang,Junbo Gong Engineering    2017, 3 (3): 354-364.   DOI: 10.1016/J.ENG.2017.03.023 Abstract   HTML   PDF (1797KB) Crystallization is an important unit operation in the pharmaceutical industry. At present, most pharmaceutical crystallization processes are performed in batches. However, due to product variability from batch to batch and to the low productivity of batch crystallization, continuous crystallization is gaining increasing attention. In the past few years, progress has been made to allow the products of continuous crystallization to meet different requirements. This review summarizes the progress in pharmaceutical continuous crystallization from a product engineering perspective. The advantages and disadvantages of different types of continuous crystallization are compared, with the main difference between the two main types of crystallizers being their difference in residence time distribution. Approaches that use continuous crystallization to meet different quality requirements are summarized. Continuous crystallization has advantages in terms of size and morphology control. However, it also has the problem of a process yield that may be lower than that of a batch process, especially in the production of chirality crystals. Finally, different control strategies are compared.
 Select Tantalum (Oxy)Nitride: Narrow Bandgap Photocatalysts for Solar Hydrogen Generation Mu Xiao,Songcan Wang,Supphasin Thaweesak,Bin Luo,Lianzhou Wang Engineering    2017, 3 (3): 365-378.   DOI: 10.1016/J.ENG.2017.03.019 Abstract   HTML   PDF (6167KB) Photocatalytic water splitting, which directly converts solar energy into hydrogen, is one of the most desirable solar-energy-conversion approaches. The ultimate target of photocatalysis is to explore efficient and stable photocatalysts for solar water splitting. Tantalum (oxy)nitride-based materials are a class of the most promising photocatalysts for solar water splitting because of their narrow bandgaps and sufficient band energy potentials for water splitting. Tantalum (oxy)nitride-based photocatalysts have experienced intensive exploration, and encouraging progress has been achieved over the past years. However, the solar-to-hydrogen (STH) conversion efficiency is still very far from its theoretical value. The question of how to better design these materials in order to further improve their water-splitting capability is of interest and importance. This review summarizes the development of tantalum (oxy)nitride-based photocatalysts for solar water spitting. Special interest is paid to important strategies for improving photocatalytic water-splitting efficiency. This paper also proposes future trends to explore in the research area of tantalum-based narrow bandgap photocatalysts for solar water splitting.
 Select Green Production Technology of the Monomer of Nylon-6: Caprolactam Baoning Zong,Bin Sun,Shibiao Cheng,Xuhong Mu,Keyong Yang,Junqi Zhao,Xiaoxin Zhang,Wei Wu Engineering    2017, 3 (3): 379-384.   DOI: 10.1016/J.ENG.2017.03.003 Abstract   HTML   PDF (3181KB) After two decades’ endeavor, the Research Institute of Petroleum Processing (RIPP) has successfully developed a green caprolactam (CPL) production technology. This technology is based on the integration of titanium silicate (TS)-1 zeolite with the slurry-bed reactor for the ammoximation of cyclohexanone, the integration of silicalite-1 zeolite with the moving-bed reactor for the gas-phase rearrangement of cyclohexanone oxime, and the integration of an amorphous nickel (Ni) catalyst with the magnetically stabilized bed reactor for the purification of caprolactam. The world’s first industrial plant based on this green CPL production technology has been built and possesses a capacity of 200?kt·a−1. Compared with existing technologies, the plant investment is pronouncedly reduced, and the nitrogen (N) atom utilization is drastically improved. The waste emission is reduced significantly; for example, no ammonium sulfate byproduct is produced. As a result, the price difference between CPL and benzene drops. In 2015, the capacity of the green CPL production technology reached 3?×?106?t·a−1, making China the world’s largest CPL producer, with a global market share exceeding 50%.
 Select Effects of Potassium and Manganese Promoters on Nitrogen-Doped Carbon Nanotube-Supported Iron Catalysts for CO2 Hydrogenation Praewpilin Kangvansura,Ly May Chew,Chanapa Kongmark,Phatchada Santawaja,Holger Ruland,Wei Xia,Hans Schulz,Attera Worayingyong,Martin Muhler Engineering    2017, 3 (3): 385-392.   DOI: 10.1016/J.ENG.2017.03.013 Abstract   HTML   PDF (4082KB) Nitrogen-doped carbon nanotubes (NCNTs) were used as a support for iron (Fe) nanoparticles applied in carbon dioxide (CO2) hydrogenation at 633 K and 25 bar (1 bar= 105 Pa). The Fe/NCNT catalyst promoted with both potassium (K) and manganese (Mn) showed high performance in CO2 hydrogenation, reaching 34.9% conversion with a gas hourly space velocity (GHSV) of 3.1 L·(g·h)−1. Product selectivities were high for olefin products and low for short-chain alkanes for the K-promoted catalysts. When Fe/NCNT catalyst was promoted with both K and Mn, the catalytic activity was stable for 60 h of reaction time. The structural effect of the Mn promoter was demonstrated by X-ray diffraction (XRD), temperature-programmed reduction (TPR) with molecular hydrogen (H2), and in situ X-ray absorption near-edge structure (XANES) analysis. The Mn promoter stabilized wüstite (FeO) as an intermediate and lowered the TPR onset temperature. Catalytic ammonia (NH3) decomposition was used as an additional probe reaction for characterizing the promoter effects. The Fe/NCNT catalyst promoted with both K and Mn had the highest catalytic activity, and the Mn-promoted Fe/NCNT catalysts had the highest thermal stability under reducing conditions.
 Select Harnessing the Beneficial Attributes of Ceria and Titania in a Mixed-Oxide Support for Nickel-Catalyzed Photothermal CO2 Methanation Ee Teng Kho,Salina Jantarang,Zhaoke Zheng,Jason Scott,Rose Amal Engineering    2017, 3 (3): 393-401.   DOI: 10.1016/J.ENG.2017.03.016 Abstract   HTML   PDF (1680KB) Solar-powered carbon dioxide (CO2)-to-fuel conversion presents itself as an ideal solution for both CO2 mitigation and the rapidly growing world energy demand. In this work, the heating effect of light irradiation onto a bed of supported nickel (Ni) catalyst was utilized to facilitate CO2 conversion. Ceria (CeO2)-titania (TiO2) oxide supports of different compositions were employed and their effects on photothermal CO2 conversion examined. Two factors are shown to be crucial for instigating photothermal CO2 methanation activity: ① Fine nickel deposits are required for both higher active catalyst area and greater light absorption capacity for the initial heating of the catalyst bed; and ② the presence of defect sites on the support are necessary to promote adsorption of CO2 for its subsequent activation. Titania inclusion within the support plays a crucial role in maintaining the oxygen vacancy defect sites on the (titanium-doped) cerium oxide. The combination of elevated light absorption and stabilized reduced states for CO2 adsorption subsequently invokes effective photothermal CO2 methanation when the ceria and titania are blended in the ideal ratio(s).
 Select Facile and Scalable Preparation of Fluorescent Carbon Dots for Multifunctional Applications Dan Wang,Zhiyong Wang,Qiuqiang Zhan,Yuan Pu,Jie-Xin Wang,Neil R. Foster,Liming Dai Engineering    2017, 3 (3): 402-408.   DOI: 10.1016/J.ENG.2017.03.014 Abstract   HTML   PDF (2717KB) The synthesis of fluorescent nanomaterials has received considerable attention due to the great potential of these materials for a wide range of applications, from chemical sensing through bioimaging to optoelectronics. Herein, we report a facile and scalable approach to prepare fluorescent carbon dots (FCDs) via a one-pot reaction of citric acid with ethylenediamine at 150 °C under ambient air pressure. The resultant FCDs possess an optical bandgap of 3.4 eV and exhibit strong excitation-wavelength-independent blue emission (λEm= 450 nm) under either one- or two-photon excitation. Owing to their low cytotoxicity and long fluorescence lifetime, these FCDs were successfully used as internalized fluorescent probes in human cancer cell lines (HeLa cells) for two-photon excited imaging of cells by fluorescence lifetime imaging microscopy with high-contrast resolution. They were also homogenously mixed with commercial inks and used to draw fluorescent patterns on normal papers and on many other substrates (e.g., certain flexible plastic films, textiles, and clothes). Thus, these nanomaterials are promising for use in solid-state fluorescent sensing, security labeling, and wearable optoelectronics.
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