Loop Concept Research Articles

Calcium Looping technology demonstration in industrial environment: the CLEANKER project and status of the CLEANKER pilot plant

The CLEANKER (CLEAN clinKER production by calcium looping process) project got EC support from October 2017 to September 2021 under the Horizon 2020 call LCE 29 – 2017. CLEANKER (www.cleanker.eu) aims at demonstrating at TRL7 (Technology Readiness Level) the Calcium Looping (CaL) concept in a configuration highly integrated with the cement production process, making use of entrained flow reactors. There are currently no feasible methods to produce clinker, and thus cement, without releasing CO2 from CaCO3, and, given the lifetime of a cement plant, the technologies to be developed have to be retrofittable. In addition to oxyfuel combustion and post-combustion solvent-based capture technologies, which have attracted most of the research efforts up to now, Calcium Looping is recognized as another very promising emerging technology for CO2 capture in cement plants. The core activity of the project is the design, construction and operation of a CaL demonstration system including the entrained-flow carbonator (the CO2 absorber) and the entrained-flow oxyfuel calciner (the sorbent regenerator). This demonstration system, connected to the Buzzi Unicem kiln of the Vernasca cement plant (Italy), will capture the CO2 from a portion of the flue gases of the kiln, using as CO2 sorbent the same raw meal that is used for clinker production. The CLEANKER implementation plan spans four years from October 2017 to September 2021.The project is in its crucial phase: the erection of the demo plant is going to be completed by the end of August 2020 and the experimental campaigns will start immediately after.

Impact of used programming language for K-12 students' understanding of the loop concept

Impact of used programming language for K-12 students' understanding of the loop concept

H2S chemical looping selective and preferential oxidation to sulfur by bulk V2O5

The concept of chemical looping is applied for the first time to selective oxidation of H2S to elemental sulfur. An oxygen carrier (OC) is exposed to cyclic reduction by H2S and oxidation by O2. The properties of bulk V2O5 as OC are explored for this reaction in the 150−200 °C temperature range. Steady cyclic behavior can be obtained with high selectivity towards elemental sulfur. Some undesired SO2 is formed during exposure to H2S but more significantly during re-oxidation of the OC. This indicates that bulk V2O5 does not completely oxidize the adsorbed H2S in the reductant step. Characterizations indicate that V4+ and V5+ species are mostly involved in the process. Preferential oxidation in presence of CH4 is confirmed on this OC. Although optimization needs to be done, the potential of chemical looping concept for direct preferential oxidation of H2S in natural gas and biogas is demonstrated.

The microbial loop concept: A history, 1930–1974

The microbial loop as a leading concept in marine microbiology gained wide recognition in the 1980s, but it has roots extending back to the 1930s when microbiologists first began to take a more dynamic approach to investigating the roles of bacteria in ocean food webs and biogeochemical cycles. Here we present a history of the microbial loop concept with emphasis on the period starting in 1930, when marine bacteriologists in Russia and the West began to study explicitly the roles of marine bacteria in the sea. Selman Waksman at Woods Hole and Claude ZoBell at La Jolla relied on colony counts on agar plates as the basis of their work. We suggest that failure to accept direct microscopic evidence of high numbers of bacteria in seawater retarded conceptual development in the West well into the 1970s. Easterners pioneered direct count and radioisotopic techniques and created a dynamic marine microbiology integrating bacteria as important components of marine food webs by the 1960s. Yurii Sorokin and colleagues carried out extensive experimental studies of bacteria as food for marine grazers and provided data for Mikhail Vinogradov and his group to write the first numerical simulation models of ocean ecosystems incorporating microbial components. It had little impact on the Western modeling community, as other Russian work of the times. In spite of continuing technical shortcomings in the field, Lawrence Pomeroy constructed a new conceptual model, providing a synthesis pointing the way toward a modern view of marine microbial ecology that finally matured technically and conceptually in the West in the early 1980s.

Some principles to optimise an additively manufactured multi-component product

ABSTRACTDepending on the requirements, the design of a product may result in very different solutions. Topological optimisation is a mathematical tool that can be used to obtain lighter parts without decreasing their stiffness. As the optimised part shapes are often too complex to be manufacturable, additive manufacturing is generally used. Usually, the topological optimisation is performed on a single part. However, for a product, the decreasing of mass and inertia in each individual part has an impact on the loads applied onto all the parts of the system. Moreover, different paths can be used to optimise a product, e.g. optimising all the parts simultaneously or part after part. Therefore, the aim of this paper is to propose, based on a case study, some optimisation principles to find the best optimisation path to design an additively manufactured product. In order to do this, the concept of topological optimisation loops is first proposed. Then, several optimisation paths are compared. In comparison with a usual single topological optimisation, the proposed method leads to an additional gain in mass of up to 35% for the case study. Finally, some optimisation principles are suggested to choose the most adapted path according to the designer objectives.

Local loops and micro-mobilities of care: Rethinking care in egalitarian contexts

This introduction to the Special Issue Local loops and micro-mobilities of care: Rethinking care in egalitarian contexts argues for the importance of analysing local organizations of care. This is a necessary addition to current scholarship which has focused on the globalization of care. Yet, in many parts of the world, such as the Northern and Eastern European countries, on which this issue focuses, care provision continues to be mainly local and migrant care workers are complementary. Nevertheless, the daily organization of care can be as complex as in the global care chains. To address this local complexity, we propose two concepts: the notion of local care loops and care as patchwork. The concept of local care loops is a sensitizing one that emphasizes routine, daily practices and micro-mobilities of care that create loops around daily practices of care. Patchwork refers to practices that are simultaneously routinized activities but that are also changing from day to day, depending on the available resources and constraints (of time, money, and caregivers), as well as the local geographies and distances that need to be connected in the loops. The introduction also presents the six articles that make up this Special Issue. The articles identify similarities and differences in processes related to the commodification of childcare and transforming gender ideologies in post-socialist and social-democratic welfare societies.

Paid home-based childcare in Slovakia: Informal markets and care loops

Drawing on interviews conducted between 2013 and 2015 with childcare workers and their employers, this article focuses on the employment of paid home-based childcare in Slovakia, where local families prefer to employ local childcarers, rather than migrant childcarers. After a brief discussion of previous studies on home-based paid childcare and social policies, I introduce the concept of care loops and summarize family-oriented policies in Slovakia. I explain that relying on social networks and trust results in hiring local women rather than migrant childcarers. I then examine the motivations of working mothers for hiring childcare workers. I show how mothers use both structural (social policy) and cultural factors (ideals of motherhood and childrearing) to explain their childcare choices. I argue that hiring full-time childcare workers is both a way to fill the care gap and a response to a cultural preference for mother-like care for infants and toddlers. This cultural preference also results in hiring part-time childcare workers who are responsible for micromobilities of care and who help parents to manage care loops.

High-pressure rapid hydrogasification of pinewood for methane production using calcium looping concept

Pressurized hydrogasification of biomass is a direct method for methane generation from renewable energy sources, and the calcium looping gasification concept is usually used in the hydrogen production process. In this paper, the calcium looping gasification concept, using a high addition amount of coarse calcium oxide as catalyst, is proposed for biomass hydrogasification. Results indicate that the methane yield increased by 35% while the carbon dioxide fraction decreased from 12 to 5 vol% with a mass ratio of calcium oxide to biomass of 2 at 800 °C. Meanwhile, more naphthalene and light aromatics were observed after calcium oxide addition. The deactivation of calcium oxide in multicycle tests was mainly due to carbon deposition and calcium carbonate formation rather than sintering. The deactivated catalyst could be recovered by calcination in air at 800 °C.

Navigating Complexity Using Systems Thinking in Chemistry, with Implications for Chemistry Education

To remain relevant, chemists need to be able to understand their work in terms of systems. Since systems thinking is a framework to understand and manage systems, the introduction of systems thinking in chemistry education would assist learners to navigate complex, inter-related concepts typical of systems. At the same time, the adoption of systems thinking in chemistry education will require a major reorientation in how chemistry is taught. We consider several characteristics of system complexity that are key to systems thinking in chemistry–including purpose, scale, boundaries, hierarchies, constraints, loop concepts and emergence–and discuss their introduction in education and the benefits this will bring.

Impact of used programming language for K-12 students' understanding of the loop concept

Block-based programming languages are becoming a favourite learning tool for programming novices while the traditional way of teaching programming mostly uses text-based programming languages. The purpose of this study was to compare the impact of used visual and textual programming languages on K-12 students' understanding of the loop concept. Participants were 312 elementary school students from 5th to 8th grade using visual programming language Scratch (n = 59), and textual programming languages Logo (n = 185) and Python (n = 68). Tests for all languages were equivalent, differing only in the used programming language. Results showed that students achieved statistically significant higher scores when using block-based programming language compared to students using textual programming languages. These results show that K-12 students need concrete experience to understand abstract concepts, as the loop concept, which Scratch as a block-based programming language provides.

Reconfiguration of distribution system with distributed generation using an adaptive loop approach

Abstract A new concept of switches selection in the meta-heuristic optimization process of optimal distribution network reconfiguration has been proposed. Based on the adaptive set of selectable candidates, the proposed concept determines the switch status. This approach prevents the creation of unfeasible solutions (non-radial and unconnected configurations), and significantly reducing the number of searches and accelerating the optimization process. Unfeasible solutions, created by meta-heuristic optimization rules, can be corrected by means of the proposed adaptive loop concept. The correct parts of the unfeasible solution are retained, while only the defective parts are replaced by the adaptively formed loops from the currently available conditions that respect the correct switching operations. In this way, the basic characteristics of the optimization process have been retained to the greatest possible extent. Tests were performed on a two different size standard distribution networks.

An advancement in CO2 utilization through novel gas switching dry reforming

This study is the first experimental demonstration of CO2 capture and utilization for dry methane reforming using a novel chemical looping concept, “Gas Switching Dry Reforming” (GSDR) to produce syngas. The new reactor concept utilizes a single fluidized bed reactor to complete redox (reactions) cycles by alternating air and gaseous fuel feeds, generating heat and near pure CO2 for usage in a consecutive dry reforming stage. Autothermal operation of GSDR was achieved using NiO/Al2O3 oxygen carrier, in a three-stage configuration where pure CO is used in the reduction stage while CH4 and CO2 are fed simultaneously in the reforming stage. Most of the heat duties of the process is generated by the exothermic oxidation reaction. The reforming stage is very sensitive to temperature with very good CH4 and CO2 conversion achieved at 850 °C but dropped rapidly at lower temperatures. Carbon deposition is a major issue affecting the performance of GSDR process although this is found to be minimized by a combination of high operating temperature and larger CO2/CH4 ratio, but also led to low H2/CO molar ratio driven by the reversed water gas shift reaction. Reducing the utilization of the oxygen carrier by 50% also proves to decrease carbon deposition by 62% due to the presence of latent oxygen on the oxygen carrier. However, CH4 and CO2 conversion are affected negatively resulting in a drop of ∼22%. An excellent opportunity for maximizing the energy efficiency of the GSDR is by integration with a Gas-To-Liquid (GTL) Fisher Tropsch to use outlet gas stream from the reforming as feedstock to GTL while the unconverted hot gasses from GTL process is fed to the reduction stage of GSDR.

Particle scale modeling of CuFeAlO4 during reduction with CO in chemical looping applications

Particle scale models that couple reaction phenomena to changes in the solid-state chemistry of an oxygen carrier system are critical to the advancement of the chemical looping concept by allowing for a means to assess process scale up. This work presents an analysis of the reduction for a CuFeAlO4 oxygen carrier with Carbon Monoxide (CO). The analysis was utilized to aid in the application of particle scale model representation of the carrier system. An experimentally driven study was conducted to provide an array of operational/parametric data sets for the analysis and their impact accessed. Quantification of the cubic spinel oxide phase and changes due to lattice oxygen depletion from reduction were explored to link the solid-state chemistry changes to the reaction progression. Reduction occurred in a multistep process as oxygen was depleted from the structure. Oxygen bound to Cu cations were the first to react with CO. As oxygen was depleted further phase re-orientation occurred resulting in an iron based aluminate (FeAl2O4) with discrete metallic copper present. FeAl2O4 was further depleted of oxygen to metallic Fe and alumina. The multistep process was emulated through the use of a multi-interface Grainy pellet model. To add to the utility of the model, the effects of product gas, CO2, on the reaction progression were incorporated into the description. In addition, the catalytic effects of the Boudouard reaction were examined and incorporated into the representation adding to the novelty of the work.

HYPERLOOP – The Sustainable Transportation

Due to rapid urbanization and emergence of mega-cities, urban transportation infrastructures are stressed leading to traffic congestion, high fuel consumption as well as increasing number of accidents and fatalities. Present transport sector globally is largely two-dimensional and may not be able to cope up with the growth of cities which is three-dimensional in nature, the environmental pollution, the traffic congestion, the sustainability, etc. This has led to efforts towards three dimensional transportation systems such as passenger drones, flying cars, cars moving through multi-layer underground tunnels etc. The overall concept of three-dimensional transportation demonstrates that the transportation sector has made a significant progress towards comprehending the necessity of a proper and sustainable transit system, which otherwise has implications on environment, health, infrastructure and sustainability as well. However, some of these futuristic options may be associated with safety and security concerns – both for them, as well as caused by them. Some of these options envisage utilization of artificial intelligence and even augmented reality. Technological challenges, the potential for cost-effectiveness, and their socio-economic impacts are also important considerations. Through deep and critical study, in this journal, the author will try to analyze the concept of hyper loop and its practicality; about its various components, its working, global acceptance of hyper loop and its possible advantages and unaddressed issues. Some critics are of the opinion that hyper loop is more of a hypothetical idea which is totally impractical and impossible, but optimistic experts say that it just needs some hard work, a decade’s time and huge amount of money which would then result in revolution of the whole transportation system in a unique, unpredictable and sustainable way. A cross-impact analysis to evaluate possible future scenario for this will also be taken up.

CLEANKER – Clean Clinker by Calcium Looping Process for Low-CO2 Cement Production

The CLEANKER project got EC support from October 2017 to September 2021 under the Horizon 2020 call LCE 29 – 2017 . CLEANKER (www.cleanker.eu) aims at demonstrating at TRL7 the Calcium Looping (CaL) concept in a configuration highly integrated with the cement production process, making use of entrained flow reactors. The cement industry is a key-sector for the reduction of CO2 emissions. CO2 generation in cement production processes in fact, cannot be disregarded due to the calcination of limestone (CaCO3 dissociated to CaO and CO2), the most important raw material. Around 60% of the direct CO2 emissions from the clinker burning process are due to this reaction. In addition, there are the emissions from combustion of mostly fossil fuels, as well as the generation of electric power required by the process (e.g. grinding), as indirect CO2 emissions. Cement production is thus responsible for about 27% of global anthropogenic CO2 emissions from industrial sources worldwide and for 5% of anthropogenic global CO2 emissions . According to IEA and ZEP studies, cement industry should contribute to the largest CO2 emission reduction through CCS in Europe, in order to meet the target of 2°C of global temperature increase (IEA 2DS scenario). There are currently no feasible methods to produce clinker, and thus cement, without releasing CO2 from CaCO3, and, given the lifetime of a cement plant (30-50 years), the technologies to be developed have to be retrofittable. In addition to oxyfuel combustion and post-combustion solvent-based capture technologies, which have attracted most of the research efforts up to now, Calcium Looping is recognized as another very promising emerging technology for CO2 capture in cement plants. Calcium looping (or carbonate looping) is a regenerative process, which takes advantage of the capacity of calcium oxide-based sorbents to capture CO2 at high temperatures. The process is divided in two basic steps: (1) the capture of CO2 by “carbonation” of CaO to form CaCO3 in a reactor operating around 650°C; and (2) oxyfuel calcination in a reactor operating above 900-920°C, which makes the CaO available again and releases a gas stream of nearly pure CO2. The highly integrated Calcium Looping process configuration allows achieving high-energy efficiency, with CO2 capture efficiency target over 90%. The overall energy consumption can be kept low by proper integration with raw meal preheating and heat recovery from the kiln flue gases. The adoption of entrained flow gas-solid reactors is particularly suitable for this Calcium Looping configuration, because in such reactors, the same very fine raw material can be used for clinker production (CaO) and for CO2 sorption without additional milling requirements. Moreover, entrained flow reactors are already commonly used in cement plants. The core activity of the project is the design, construction and operation of a CaL demonstration system including the entrained-flow carbonator (the CO2 absorber) and the entrained-flow oxyfuel calciner (the sorbent regenerator). This demonstration system, connected to the Buzzi Unicem kiln of the Vernasca cement plant (Italy), will capture the CO2 from a portion of the flue gases of the kiln, using as CO2 sorbent the same raw meal that is used for clinker production. Other activities will include: (i) screening of different raw meals to assess their properties as CO2 sorbent, (ii) reactors and process modelling, (iii) scale-up study, (iv) economic analysis, (v) life cycle assessment, (vi) CO2 transport, storage and utilization study, (vii) demonstration of the complete value chain, including mineral carbonation of waste ash with the CO2 captured in the pilot system, (viii) exploitation study for the demonstration of the technology at TRL>7 and for its first commercial exploitation based on CO2 transport and storage opportunities. It integrates the research of 13 organizations: • Representatives from the academia: Politecnico di Milano (Italy), Tallinn University of Technology (Estonia), Lappeenranta University of Technology (Finland); University of Stuttgart (Germany) and Tsinghua University (China); • Research centres: LEAP (Italy), CSIC (Spain) and VDZ (Germany); • SME: Quantis (Switzerland); • Technology provider: IKN (Germany); • End users: Buzzi Unicem and Italcementi – Heidelberg Group (Italy); • Environmental organization: Amici della Terra (Italy). Thus including all the necessary expertise and access to the industrial facilities to reach the ambitious aim of the project. The project is coordinated by LEAP. Acknowledgements: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 764816. This work is supported by the China Government (National Natural Science Foundation of China) under contract No. 91434124 and No. 51376105. Disclaimer: The European Commission support for the production of this publication does not constitute endorsement of the contents which reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

Mutual Influence-aware Runtime Learning of Self-adaptation Behavior

Self-adaptation has been proposed as a mechanism to counter complexity in control problems of technical systems. A major driver behind self-adaptation is the idea to transfer traditional design-time decisions to runtime and into the responsibility of systems themselves. To deal with unforeseen events and conditions, systems need creativity—typically realized by means of machine learning capabilities. Such learning mechanisms are based on different sources of knowledge. Feedback from the environment used for reinforcement purposes is probably the most prominent one within the self-adapting and self-organizing (SASO) systems community. However, the impact of other (sub-)systems on the success of the individual system’s learning performance has mostly been neglected in this context. In this article, we propose a novel methodology to identify effects of actions performed by other systems in a shared environment on the utility achievement of an autonomous system. Consider smart cameras (SC) as illustrating example: For goals such as 3D reconstruction of objects, the most promising configuration of one SC in terms of pan/tilt/zoom parameters depends largely on the configuration of other SCs in the vicinity. Since such mutual influences cannot be pre-defined for dynamic systems, they have to be learned at runtime. Furthermore, they have to be taken into consideration when self-improving their own configuration decisions based on a feedback loop concept, e.g., known from the SASO domain or the Autonomic and Organic Computing initiatives. We define a methodology to detect such influences at runtime, present an approach to consider this information in a reinforcement learning technique, and analyze the behavior in artificial as well as real-world SASO system settings.

Pertraction of volatile fatty acids through biodiesel-based liquid membranes

Volatile fatty acids (VFAs) are ideal substrates for mixed microbial cultures to synthesize polyhydroxyalkanoates. Therefore, VFA pertraction from anaerobic diluted fermentation broths to slightly alkaline aerobic medium becomes a crucial step to develop a closed loop concept in which VFAs are used for polyhydroxyalkanoate production. New liquid membranes (LMs) based on lipophilic amines and biodiesel were proposed for this purpose. The performance of each LM was tested through a VFA distribution coefficient test and pertraction kinetic experiments. The transfer of VFAs from LM to receiving solution was the main limiting step of the process, with flux rates of 0.001–0.04 cm3 cm−2 h−1 (best LM with 10 wt% of trioctylamine). The biocompatibility of trioctylamine -biodiesel LM towards anaerobic bacteria was confirmed through a 15-d acidogenic fermentation test. Trioctylamine-biodiesel LM was finally tested in a specifically designed continuous pertraction module, where VFA transfer rates of 1–3 h−1 were achieved.

Blockchain-Driven on-Demand Control Loops Over Iot Environments

The feedback control loop is the atomic unit in a control system. Typically, feedback control loops are rigid objects that involve a dynamical system, or plant, which has a set of its output states measured by dedicated sensors, which in turn feed a processing unit, known as controller, that calculates actions to be applied as inputs to the plant, via elements known as actuators, in order to drive the outputs to a desired value or trajectory. The appearance of the Internet of Things (IoT) paradigm, where a large number of sensors and processing units interact over a communication network, offers an underlying infrastructure to operate and configure control loops using a different logic: an on-demand strategy. This work introduces the concept of on-demand control loop, and proposes the use of blockchain technology as the enabling infrastructure for generating on-demand control loops over large-scale IoT environments. General design guidelines are given and a simple implementation example over the Ethereum blockchain is presented, which shows the feasibility of the proposed technique.

Solids Flow in a “Particle-in-Tube” Concentrated Solar Heat Absorber

Fluidized particle-in-tube solar absorbers are increasingly investigated both as receivers in a solar power concept or as a receiver/reactor for the thermal decomposition of minerals or for gas–solid reactions such as CO₂ looping concepts and thermo-chemical energy storage. Such applications require a high heat transfer rate from the tube wall to the upflowing suspension of particles and a strict control of the particle residence time. Conversion and heat transfer depend upon the particle mixing, its residence time (RT), and residence time distribution (RTD). Both parameters are hence important in fluidized bed applications. The present research experimentally investigated the use of an Upflow Bubbling Fluidized Bed (UBFB) as a particle-in-tube concentrated solar receiver and/or reactor. The RTD was determined by tracer response and compared with predictions from different models. Both a cascade of stirred tank reactors and a plug flow with dispersion model provide a good fitting of the experimental results. The former is however preferred, with a number of cascade mixing cells between 3 and 4, slightly dependent on both the operating air velocity and the particle circulation rate. The commonly applied ratio of the superficial fluidization velocity and the minimum fluidization velocity of the particles is between 3 and 20, whereas solid circulation fluxes up to 100 kg/m² s are used. Design equations are derived. The results are moreover used in test cases of a concentrated solar power absorber and in the use of a UBFB as solar limestone calcination furnace. The approach can also be applied to processes of, for example, heat absorption or drying provided kinetic data are known.

Nonuniform C-Band Loop Antenna: A New Approach for Future UWB Applications

Antenna design becomes very difficult at very small wavelengths and a special lab is required to manufacture a small antenna which costs a lot. A new approach is proposed to enhance the bandwidth of the loop antenna which can be designed at very high frequency using conventional PCB design. The proposed antenna is a nonuniform loop and covers UWB frequency range. The nonuniform structure of the loop is designed using the concept of both thin and thick loop antenna together which leads to an improvement in the antenna bandwidth. The proposed nonuniform loop antenna covers a band of 91.4% which is higher than any existing printed loop antenna. The frequency ranges from 3.54GHz to 9.5GHz and the measured result is in agreement with the simulated result. This technique can be very helpful in designing UWB antennas in the range of Ku or higher than this.