1,721,070 research outputs found
A review on management and recycling of spent selective catalytic reduction catalysts
No full textCatalysts for selective catalytic reduction are widely used for the reduction of nitrogen oxides into gaseous nitrogen in many industrial applications. These catalysts usually contain titanium, tungsten, and vanadium. Due to the increasing demand, a new strategy for the management of end-of-life catalysts is urgent, in particular for the recovery of valuable metals and the reduction of the material disposed of. Titanium, tungsten, and vanadium shall be recovered and reused for the production of new catalysts or other products, to establish a circular economy approach. In this paper, a systematic review of the main strategies adopted for the management of spent catalysts was proposed and, in particular, an overview of the regeneration and rejuvenation techniques, the current processes for the recovery of such catalysts and the treatments patented. The present study found that among the recycling processes for the extraction of metals, those based on alkaline roasting and/or leaching are the most used: vanadium and tungsten are indeed water-soluble, so that can be easily separated from titania during the leaching stage. Instead, the acid leaching is not developed because of the downstream stages required to separate the three metals from each other. The recovery of the metals is currently negligible at full scale. For this reason, the recovery of titanium, tungsten, and vanadium with high extraction yields and grades shall be pursued in the future at a large scale, and the research shall be oriented towards this scope, whereas landfilling, that is still the main option in the management of this material, shall be penalized with a disposal fee
Optimization of a plant for treatment of industrial waste solutions: Experimental and process analysis
No full textThe present paper deals with the optimization of an industrial plant that treats waste solutions coming from different manufacturing processes. In particular, an extensive experimental work was carried out to understand whether some streams could be diverted from the distillation column in order to recover solvents, suitable as secondary fuel. Experimental tests, including four full factorial designs, optimized the consumption of reagents in the Fenton process: the specific consumptions were 0.65 g L−1 of H2O2 and 0.42 g L−1 of FeSO4·7H2O, when treating the evaporated fractions from multiple-effect evaporator, concentrator and dryer, diverted from the distillation column. The application of the Fenton process increased the abatement of the chemical oxygen demand (COD) and the oxygen uptake rate (OUR). The optimization of the feed entering the distillation column led to a water content lower than 5%vol in the distilled fraction: hence, such solvents could be used as additional fuel in a dual-fuel boiler. The economic analysis showed that it could be possible to save around 420,000 € y−1
Wasted liquid crystal displays as a source of value for e-waste treatment centers: a techno-economic analysis
No full textThe management of waste from electrical and electronic equipment is always asking for innovative solutions. However, in order to make this business interesting for companies, more information is needed, especially economic data. To this aim, this work discusses the recycling of wasted liquid crystal displays (LCDs), both in technical and economic terms. In addition, a sensitivity analysis has been implemented to justify the soundness of the results and the effect of instability on some critical variables. Results demonstrated as spent LCDs are an interesting field in which to develop circular practices. The economic analysis defines that the recycling of wasted LCDs are profitable in the baseline scenario (134 thousand €) and this is determined mainly by both back cover and valuable printed circuit boards. Additionally, the project is not economically feasible without a disposal fee (−1.7 million €)
A socio-economic analysis of biomethane in the transport sector: The case of Italy
No full textThe transport sector has a low penetration of renewable energy, and this presents a serious obstacle to tackling climate change. Biomethane is seen as a decarbonisation solution, but only some European countries have pursued its development. Italy is one of these countries, having released a decree to stimulate development of the sector. The present work considers two typologies of substrate (the organic fraction of municipal solid waste and by-products) used in three sizes of plants (125 m3/h, 250 m3/h and 500 m3/h). A detailed socio-economic analysis is presented and policy implications are provided. The recovery of waste enables the creation of a circular economy, but the economic feasibility of such a model is verified in only some scenarios. A sensitivity analysis on the critical variables is conducted to support investment in this area. The use of green gas is found to be capable of significantly reducing greenhouse gas emissions in the transport sector, but the economic value of any environmental externality is low due to the value of carbon dioxide
Process for the recycling of alkaline and zinc–carbon spent batteries
No full textIn this paper a recycling process for the recovery of zinc and manganese from spent alkaline and
zinc–carbon batteries is proposed. Laboratory tests are performed to obtain a purified pregnant solution
from which metallic zinc (purity 99.6%) can be recovered by electrolysis; manganese is recovered
as a mixture of oxides by roasting of solid residue coming from the leaching stage. Nearly 99% of zinc
and 20% of manganese are extracted after 3 h, at 80 ◦C with 10% w/v pulp density and 1.5Msulphuric acid
concentration. The leach liquor is purified by a selective precipitation of iron, whereas metallic impurities,
such as copper, nickel and cadmium are removed by cementation with zinc powder. The solid residue of
leaching is roasted for 30 min at 900 ◦C, removing graphite completely and obtaining a mixture ofMn3O4
andMn2O3 with 70% grade of Mn. After that a technical-economic assessment is carried out for a recycling
plant with a feed capacity of 5000 t y−1 of only alkaline and zinc–carbon batteries. This analysis shows
the economic feasibility of that plant, supposing a battery price surcharge of 0.5 D kg−1, with a return on
investment of 34.5%, gross margin of 35.8% and around 3 years payback time
A techno-economic assessment of biogas upgrading in a developed market
No full textThe development of renewable energies was impressive in recent years on a global scale. This produced changes regarding production processes, citizens' habits, industrial investments and consumer decisions. In this context, the policy-maker played a crucial role. The subsidies are able to determine the development of a specific market. Biogas market spread globally, while biomethane market concentrated in some territories. Green gas can be used as vehicle fuel or injected into the gas grid but also burnt for co-generation. The present work proposes a techno-economic analysis for an existing biogas plant. In particular, the analysis was focused on the comparison between two possible strategic plans, in order to establish which one was the best in terms of profitability: the first one is the expansion of the plant to upgrade biogas to biomethane, whereas the second one is to continue the production of biogas as planned when the plant was constructed. The Discounted Cash Flow (DCF) method was proposed in this paper, and the Net Present Value (NPV) is the main index used. One 250 m3/h biomethane plant located in Italy using pressure swing adsorption (PSA) technique is analysed. The results demonstrated the positive environmental impact deriving from the use of zeolites synthesized from spent fly ash and the profitability is verified only in some scenarios. However, they are limited only to the construction of new biomethane plants, while the upgrading of existing biogas plants are always unprofitable. A Break-Even Point (BEP) analysis quantifies the value of subsidies of biogas and biomethane by which the profitability could be reached. Biomethane can contribute to the development of circular economy models, while the sustainability targets are achieved only in some scenarios
The case study of a photovoltaic plant located at the university of L'Aquila: An economic analysis
No full textSolar energy has contributed significantly to the energy transition towards a low carbon society. Public offices – including universities – are being called to participate in the solar energy transition, as the availability of their rooftops represents an opportunity. The present study aimed at evaluating the economic feasibility of a photovoltaic (PV) plant at the University of L'Aquila, approximately 10 years after an earthquake devastated the region. The reconstruction process is ongoing, and a solar PV plant could potentially move the city in a sustainable direction. The development of sustainability models requires the economic verification of relevant projects and a complete list of indicators for decision-makers. The present work found that a 210 kW PV plant at the University of L'Aquila would reduce emissions by 184.9 t CO2eq/year and generate 1500 € profits for each kW installed; and a 115 kW PV plant would reduce emissions by 101.5 t CO2eq/year and generate profits of 1370 € for each kW installed. The analysis of alternative scenarios gave solidity to the results, confirming the pivotal role of the share of self-consumed energy. Level of insolation and plant size were also found to significantly influence economic performance. Finally, the adoption of a bonus to encourage the production and self-consumption of energy may increase investors’ attention towards environmental issues
Oxidative desulfurization of benzothiophene derivatives with cis-dioxomolybdenum(VI) catalyst precursors, under extractive conditions
Full text linkMetal recovery from spent refinery catalysts by means of biotechnological strategies
No full textA bioleaching study aimed at recovering metals from hazardous spent hydroprocessing catalysts was carried out. The exhaust catalyst was rich in nickel (4.5mg/g), vanadium (9.4mg/g) and molybdenum (4.4mg/g). Involved microorganisms were iron/sulphur oxidizing bacteria. Investigated factors were elemental sulphur addition, ferrous iron addition and actions contrasting a possible metal toxicity (either adding powdered activated charcoal or simulating a cross current process by means of periodical filtration). Ferrous iron resulted to be essential for metal extraction: nickel and vanadium extraction yields were 83% and 90%, respectively, while about 50% with no iron. The observed values for molybdenum extraction yields were not as high as Ni and V ones (the highest values were around 30–40%). The investigated actions aimed at contrasting a possible metal toxicity resulted not to be effective; in contrast, sequential filtration of the liquor leach had a significant negative effect on metals extraction. Nickel and vanadium dissolution kinetics resulted to be significantly faster than molybdenum dissolution ones. Furthermore, a simple first order kinetic model was successfully fitted to experimental data. All the observed results supported the important role of the indirect mechanism in bioleaching of LC-Finer catalysts
Adsorption of CO2 by synthetic zeolites
No full textThe paper reports on a possible way to recycle fluid catalytic cracking catalysts (FCCCs), widely used in oil refining operations. This research proposes a novel approach that leads to a near zero-waste process. The spent FCCC was leached by 1.5 mol/L of HNO3, HCl and H2SO4 solutions at 80°C, for 3 h with a solid to liquid ratio of 20 %wt/vol. The leaching yields for cerium and lanthanum were in the range 69-82 %. The solid residues from the leaching stage were used as base material for the synthesis of the zeolites by means of a combined thermal-hydrothermal treatment. The characterization of the zeolites demonstrated that the Na-A phase was predominant over the Na-X phase. The zeolites were tested as sorbent material for CO2 separation from CH4, in order to simulate the upgrading of biogas to biomethane. The maximum adsorption rate of CO2 was 0.778 mol CO2/kg of zeolite at 3 bar, with a resulting CH4 recovery of 62 % and purity of 97 %vol. The zeolites synthesized from spent FCCC represent a feasible solution to recover such industrial waste
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