1,720,961 research outputs found
Techno-economic assessment of solar steam reforming of methane in a membrane reactor using molten salts as heat transfer fluid
No full textThis paper reports the results obtained in a techno-economic analysis of the Steam Methane Reforming (SMR) technology aided with solar heat, developed and demonstrated in the European FCH JU project CoMETHy: a compact membrane reformer heated with molten salt up to 550 °C allowed to simultaneously carry out methane steam reforming, water-gas-shift reaction and hydrogen separation. This reactor can be integrated with new generation Concentrating Solar Thermal (CST) systems to supply the process heat. Experimental validation of the technology has been successfully achieved in a pilot scale plant and the results recently published. In this paper, we introduce a fully-integrated scheme and operation strategies of a plant on the 1500 Nm3/h hydrogen production scale. Then, techno-economic analysis of this new solar-driven process is presented to evaluate its competitiveness. Considering a plant capacity of 1500 Nm3/h (pure hydrogen production) and today's costs for the methane feed and the CST technology, obtained Hydrogen Production Cost (HPC) are in the range of 2.8–3.3 €/kg for a “solar-hybrid” system with high capacity factor (8000 h/year operation) and 4.7 €/kg for a “solar-only” case, while HPC≅1.7 €/kg can be obtained with the conventional route under equivalent assumptions. However, a sensitivity analysis shows that the expected drop of the cost of the CST technology will bring the HPC around 2.4 €/kg for the “solar-hybrid” case and close to 3.4 €/kg for the “solar-only” case, thus making the cost of solar reforming closer to conventional SMR with CO2 capture and with wind/solar electrolysis in the future. In the “solar-hybrid” case total CO2 production can be reduced by 13–29% with 58–70% of produced CO2 recovered as pure stream (at 1.3 bar); in the “solar-only” case total CO2 production can be reduced by 52% and 100% of produced CO2 recovered as pure stream (at 1.3 bar). However, compared to the conventional route, CO2 avoidance costs are still relatively high (≥137 €/tonCO2) and process optimization measures required. Therefore, optimization measures have been outlined to increase the overall process efficiency and further reduce the HPC
Stochastic consequential Life Cycle Assessment of technology substitution in the case of a novel PET chemical recycling technology
Full text linkThe current traditional mechanical recycling of Polyethylene Terephthalate (PET) grinds the waste into granulate, yet the resulting secondary material quality is strongly dependent on the efficiency of the selection processes, leading to the requirement of an integration of fossil PET to assure the bottle-grade quality is reached. Instead, the novel chemical recycling gr3n technology depolymerizes the waste PET back into the constituent monomers with a resulting quality that is comparable to the virgin product, due to a more efficient separation of impurities. In order to estimate the environmental impacts related to the introduction of this technology in the related market, Consequential Life Cycle Assessment (CLCA) is particularly indicated. Among the consequential approaches, we adopt the Stochastic Technology Choice Model, as it is able to model the technological mixes typical of markets based on costs and production capacities, while its stochasticity suits the need to manage the uncertainty of future market conditions. Indeed, the assessment of the expected technological mixes contributing to the same function and the quality of the recycled material are key to evaluate the variation in marginal LCA impacts due to the introduction of the gr3n technology. We assess the marginal LCA impacts of the European bottle-grade PET market in two scenarios: one in which the gr3n technology is not available and one in which this technology is present. To correctly evaluate the difference between these two scenarios, we perform a paired simulation. Here we show that the populations related to this difference show more than 50% negative results in 12 out of 16 impact indicators and more than 75% of negative results in 9 out of 16 impact indicators. In particular, a median 0.13 kg CO2-eq per kg bottle-grade PET could be saved by the introduction of gr3n, equivalent to a 5% reduction. We show that the 5–95 percentiles range of the difference between the two scenarios is only 17.7% of the average range defined by the two separate scenarios distributions, confirming previous findings from the literature. The robustness of the results is tested through three sensitivity analyses. Therefore, policy makers should focus on limiting the increase in marginal demand of PET and on creating fair conditions for this chemical recycling technology to be deployed to complement mechanical recycling in reducing virgin PET production, thus decreasing potential environmental impacts and fostering a more circular economy. The positive performance of the novel technology is strongly related to the increased substitution of waste treatment processes, such as incineration and landfill, and to the increased quality of the recycled product: this environmental profile could further improve as the novel technology will scale up industrially
Environmental and economic assessment of gasification wastewater treatment by life cycle assessment and life cycle costing approach
No full textThis study compared the sustainability of six alternatives for the treatment of industrial wastewater from a gasifier, considering both environmental and economic aspects by the approaches of: uses Life Cycle Assessment (LCA) and Life Cycle Cost (LCC). The processes have been developed under the zero liquid discharge approach and included a chemical removal of pollutants by using Fenton and neutralization, evaporation and crystallization to concentrate salts and stripping for the removal of ammonia from distillate of evaporation step and recover water useful for industrial reuses. The scenarios differed for the type of utilities used for the operation (steam and hot water from thermal waste) and from an optimization of the crystallization that provided a reduction of the amount of waste and an energy recovery from distillate. LCA indicated that the six scenarios produced comparable results, since the common chemical treatment (raw material and waste disposal) causes the highest contribution. The optimal scheme used hot water as utilities and had an optimization of the crystallization section (scenario B2), this options allowed a decrease of emission to air of 25% and reduction of 15% of deposited goods. Scenario B2 is much more financially attractive than the other proposed treatment, having a total cost of 123 €/t, with a reduction of 17% respect to the current disposal of 150 €/t. LCA and LCC results prove the effectiveness of thermal waste use as utilities for the wastewater treatment operations and the optimization of crystallization unit is the most environmentally and economically favourable alternative
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Experimental validation of a pilot membrane reactor for hydrogen production by solar steam reforming of methane at maximum 550 °C using molten salts as heat transfer fluid
No full textAn innovative steam reformer for hydrogen production at temperatures lower than 550 °C has been developed in the EU project CoMETHy (Compact Multifuel-Energy To Hydrogen converter). The steam reforming process has been specifically tailored and re-designed to be combined with Concentrating Solar plants using “solar salts”: a low-temperature steam reforming reactor was developed, operating at temperatures up to 550 °C, much lower than the traditional process (usually > 850 °C). This result was obtained after extensive research, going from the development of basic components (catalysts and membranes) to their integration in an innovative membrane reformer heated with molten salts, where both hydrogen production and purification occur in a single stage. The reduction of process temperatures is achieved by applying advanced catalyst systems and hydrogen selective Pd-based membranes. Process heat is supplied by using a low-cost and environmentally friendly binary NaNO3/KNO3 liquid mixture (60/40 w/w) as heat transfer fluid; such mixture is commonly used for the same purpose in the concentrating solar industry, so that the process can easily be coupled with concentrating solar power (CSP) plants for the supply of renewable process heat. This paper deals with the successful operation and validation of a pilot scale reactor with a nominal capacity of 2 Nm3/h of pure hydrogen from methane. The plant was operated with molten salt circulation for about 700 h, while continuous operation of the reactor was achieved for about 150 h with several switches of operating conditions such as molten salts inlet temperature, sweep steam flow rate and steam-to-carbon feed ratio. The results obtained show that the membrane reformer allows to achieve twice as high a conversion compared to a conventional reformer operating at thermodynamic equilibrium under the same conditions considered in this paper. A highly pure hydrogen permeate stream was obtained (>99.8%), while the outlet retentate stream had low CO concentration (<2%). No macroscopic signs of reactor performance loss were observed over the experimental operation period
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Case study on technical feasibility of galvanic wastewater treatment plant based on life cycle assessment and costing approach
No full textThis study uses Life Cycle Assessment (LCA) and Life Cycle Cost (LCC) to compare three process design alternatives for treating wastewater from galvanic industry. The proposed processes have been developed in according to a zero-liquid discharge, ZLD, approach and included reverse osmosis for the concentration, evaporation and crystallization of salts, mainly calcium chloride. The various scenarios differ for the type of utilities used for the operation (steam and as alternative hot water from thermal waste) and from an optimization of the crystallization step that provided an energy recovery from distillate. Results show that by using thermal waste as utilities for the operation of evaporation, crystallization and the optimization of crystallization unit is the most environmentally and economically favourable alternative
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