Secondary Stream Research Articles

Electrochemical Selectivity for Metals in Molten Sulfides

Molten sulfides show promise as an alternative electrolyte for production of metals such as copper and silver. They provide a means to sidestep the current emissions- and waste- heavy processes used both in primary (e.g. from ore) and secondary (e.g. recycled product) streams by direct reduction of a metal's sulfide form, such as Cu2S, to produce metal and sulfur. Experiments with molten sulfide electrolytes have shown high efficiency in the reduction of copper sulfides and iron sulfides to their metals. Data have also demonstrated high solubility of precious metals silver and gold, and stable electrochemical signals during reduction, evidence for a viable and streamlined method of precious metal refining and recycling. The current work focuses on predicting which metal, and of what purity, is reduced from the electrolyte. Because the standard-state reduction potentials of copper and iron sulfides are very close to each other (less than 100mv), and because the reduction potentials of silver and gold sulfides are also hypothesized to be close in value with each other, there is a possibility of co-deposition occurring, compromising the purity of the final metal product. By carefully tailoring the activities of the electrolyte species and cathode products, it is possible to bias the reduction reaction towards one species over another. Therefore, the thermodynamics of both the electrolyte and metal product should be very well defined. This talk will discuss experiments in determining metal/sulfide equilibria and how that equilibrium relates to efforts in modeling the cathode product.

Development of a Mixer Design Using Numerical Methods to Calculate Flow Hydrodynamics in the Working Volume

The influence of the location of inlet nozzles for a secondary liquid stream on the flow structure in the working volume of ejection mixers used to produce water-in-oil emulsions was studied using numerical methods. The parameters and physical properties of a working medium corresponding to those of process oil supplied to industrial electrical desalting plants were calculated using the SST k –ω turbulence model. The ergonomics of the developed apparatuses could be preliminarily evaluated by using numerical methods to analyze the distribution of velocity and pressure fields in the working volume. An even number of inlet pipes for the secondary reagent that were located opposite each other improved the mixing conditions in the mixers and used the energy of the primary stream to produce turbulence and disperse secondary-reagent streams.

Estimating increasing diversity and dissipative loss of critical metals in the aluminum automotive sector

As the demand for and consumption of products and services grow in the US, so does the concern for sustainable material usage. In the automotive industry, major sustainability issues revolve around advocating for improved fuel economy and the incorporation of materials with higher recyclability in order to reduce greenhouse gas (GHG) emissions. A popular strategy to achieve this in the automotive industry is light-weighting. Many studies in this field are focused on the environmental benefits of light-weighting, that is, how replacement of traditional steel in the automotive industry with aluminum, for instance, will help reduce the amount of CO2-eq emissions in the environment. The increasing use of aluminum in the industry for differing automotive applications broadens the range of alloying elements. Unfortunately, many of these elements are dissipatively lost and also deemed critical. Furthermore, some of the alloying elements accumulate as tramp (unwanted) elements in the secondary aluminum stream, hence posing as a barrier to effective recycling, thus leading to material and economic losses. We quantified the material losses and analyzed the economic losses attributed to the dissipation of critical metals and also examined the attendant accumulation of tramp elements in the recycled aluminum stream. Our results indicate that to achieve a more circular economy requires investment and further development of a) operational blending and batching strategies that comprehend alloying additions and the inherent variability of their actual composition, and b) economically feasible material identification and sorting technologies that will help in abating these material losses and associated economic losses.

Recycling of spent NiMH batteries: Integration of battery leach solution into primary Ni production using solvent extraction

The utilization of existing metallurgical infrastructure and integration of secondary process streams into primary metals production can provide advantages over separate recycling plants. This paper focuses on the integration of a pregnant leach solution (PLS) into a nickel production plant that contains Ni, Co, Zn, Mn, Fe, Al and Cd ions, derived from a NiMH recycling stream. The solution composition highlights the challenge related to spent battery investigations, as although toxic Cd is not present in NiMH battery chemistries, it ends up into the battery waste collection and prevents direct integration of the battery waste into the primary process. The aim of the study is to remove Zn, Fe, Al, Mn and Cd ions from the PLS, so that the Ni and Co remaining in solution could be integrated into the nickel production process. A two-step solvent extraction process using Di-2-ethylheyxl phosphoric acid (D2EHPA) was developed. In the first step, Zn, Al and Fe were removed at pH 1.5, whereas in the second step Cd and Mn were removed at pH 2.3. Different process parameters (pH, O/A ratio, temperature, extractant concentration, kinetics) were optimized at each step of the solvent extraction. The purified and fully integrable PLS was found to contain Ni ~28 g/L and Co ~3.7 g/L.

ANALYSIS OF ENERGY FLOWS IN POWER SUPPLY SYSTEMS WITH NON-LINEAR LOAD

The problem of the non-sinusoidal modes analysis of the power supply system with non-linear elements and their influence on the efficiency of the power transmission are considered. It is carried out numerical analysis of electric energy flows for three phase power supply system with sinusoidal electromotive force source, linear active load and non-linear elements (diodes). Power transfer is considered as distribution of the primary power flow from source. The part of this flow is converted by non-linear elements and return into the network like secondary power stream of zero sequence and high harmonics which is consumed by resistance elements and causes additional power losses. As a result transporting efficiency and power factor are reduced and energy quality becomes worse. In order to improve the quality of electricity, it is proposed to normalize the relative value of the reactive power of distortion for non-linear electric collectors and to oblige manufacturers of electrical products to complete them with filters of higher harmonics. With the purpose of correct selection of the type and power of compensating devices and monitoring the parameters of the electric network mode, it is proposed to expand the functionality of electronic meters by dividing the reactive power into two components - shear power and distortion power, and for the objective analysis of energy flows, it is proposed to standardize the reactive power of distortion. It is shown that in such system current in neutral line increases due to overlaying of zero sequence harmonics currents. This should be taking into account during neutral line cross-section choice and power losses calculation.

Iodine immobilization by materials through sorption and redox-driven processes: A literature review.

Radioiodine-129 (129I) in the subsurface is mobile and limited information is available on treatment technologies. Scientific literature was reviewed to compile information on materials that could potentially be used to immobilize 129I through sorption and redox-driven processes, with an emphasis on ex-situ processes. Candidate materials to immobilize 129I include iron minerals, sulfur-based materials, silver-based materials, bismuth-based materials, ion exchange resins, activated carbon, modified clays, and tailored materials (metal organic frameworks (MOFS), layered double hydroxides (LDHs) and aerogels). Where available, compiled information includes material performance in terms of (i) capacity for 129I uptake; (ii) long-term performance (i.e., solubility of a precipitated phase); (iii) technology maturity; (iv) cost; (v) available quantity; (vi) environmental impact; (vii) ability to emplace the technology for in situ use at the field-scale; and (viii) ex situ treatment (for media extracted from the subsurface or secondary waste streams). Because it can be difficult to compare materials due to differences in experimental conditions applied in the literature, materials will be selected for subsequent standardized batch loading tests.

Reactive spark plasma sintering of Cs-exchanged chabazite: characterisation and durability assessment for Fukushima Daiichi NPP clean-up

ABSTRACT Ion-specific media (ISM) have played an integral role in the clean-up and remediation efforts at the Fukushima Dai-ichi disaster site, through the processing of contaminated wastewaters. The use of these materials generates a secondary nuclear waste stream, presenting its own series of engineering problems arising from stringent handling and long-term storage requirements. A reactive spark plasma sintering (SPS) method was investigated for conditioning of the spent cesium exchanged zeolite, chabazite. A natural form of the zeolite was used as an analogue to the engineered ISM used at the Fukushima NPP site. Simulant wasteforms were sintered using different temperature and pressure parameters followed by analysis of phase assemblage, density, and durability (using the product consistency test (PCT)). The results indicated that zeolite structure had collapsed completely, with the exchanged cesium partitioned primarily into a durable feldspar to assure stability of the sintered material for passively safe storage or geological disposal.

Closed-loop hydrometallurgical treatment of end-of-life lithium ion batteries: Towards zero-waste process and metal recycling in advanced batteries

Abstract This work presents an enhanced hydrometallurgical process for recycling lithium ion batteries. First, end-of-life batteries were processed in a physical pre-treatment plant to obtain a representative electrode material. The resulting leachate was purified forth by iron-precipitation, liquid–liquid extractions, and an innovative Li–Na separation, in order to obtain valuable products. These products include high-grade graphite, cobalt oxide (Co3O4, purity 83%), cobalt oxalate (CoC2O4, purity 96%), nickel oxide (NiO, purity 89%), and lithium carbonate (Li2CO3, purity 99.8%). The recovery rate was quantitative for graphite, between 80% and 85% for cobalt depending on the nature of the recovery method, 90% for nickel, and 72% for lithium. Secondary streams were also valorized to obtain sodium sulfate (Na2SO4, purity 96%), and MnCoFe2O4 magnetic nano-sorbents according to the zero-waste concept. In order to close the loop, recycled Co3O4 and NiO were used as conversion-type anode materials for advanced lithium ion batteries showing promising performances.

Study of a full scale oxy-fuel cement rotary kiln

Oxy-fuel combustion has been shown to be an attractive technology to be implemented in cement production with CO2 capture from a process point of view. Due to the market situations and future perspectives it is necessary that the technology can be retrofitted into existing plants. As part of the H2020 EU project CEMCAP, the study presented here investigates the retrofitting of oxy-fuel combustion technology on a typical full-scale cement rotary kiln of 3000 ton/year clinker capacity. The flame generated by a commercial burner has been modelled by CFD with a seven steps combustion reaction model, the k-omega SST turbulence model, and the discrete ordinates radiation model with the Weighted Sum Grey Gas model. The burner is composed of an annular outlet where coal is fed and nozzles from which angled high velocity jets generate a swirling motion for flame stabilization and mixing purposes. As in all rotary cement kilns, a high temperature low velocity secondary oxidizer stream coming from the clinker cooler flows coaxially to the burner in the kiln for heat efficiency purposes. A flame developing in air has been used as a reference case and several oxy-fuel flames have been characterized and compared. The oxy-fuel inlet parameters that are varied in the study are the oxidizer composition and flow rates in both the primary and secondary streams. The work presented is part of an optimization procedure based on iterative interaction with the process modelling of the whole cement plant with full oxy-fuel capture (not presented in this article). With retrofit application in mind, the objective was to reproduce a heat radiation profile to the clinker equivalent to that obtained in the air reference case. The optimized oxy-fuel case is characterized by a primary burner oxidizer of lower flow rate, but with higher oxygen concentration of up to 52.1% to generate the necessary heat in the near burner region.

Experimental investigation of jet noise from a high BPR dual-stream jet in a static model-scale test

The noise characteristics of a dual-stream jet of bypass ratios greater than 10 were investigated in response to area ratio, nozzle-operating conditions, installation effect, and chevron effect. The key conclusions were as follows. (1) The area ratio impacted the noise by up to 3 dB at aft angles and at mid-frequency for heated conditions. (2) The spectral variation due to the change of primary stream parameters was constant at low Strouhal numbers and diminished at high Strouhal numbers. (3) The impact of the secondary stream pressure was described by the scaling law of single-stream jets for unheated conditions. The flow parameters of other jets were required to describe the spectra of Strouhal numbers between 0.2 and 2.0, based on the secondary jet for heated conditions. (4) The installed jet noise was quantified for various wing configurations and was more pronounced at forward angles. (5) The chevron nozzle reduced overall noise by up to 4 dB, though it became less attractive when installed. The quantified information is expected to improve the estimation of noise from a dual-stream jet of high bypass ratios.

Methodology and calculation model for recycling of composite construction products

The circular economy development has increased awareness on how construction products are treated at the end-of-life stage (EoL). With a growing recognition of the finite nature of primary resources, manufacturing processes are being shifted from the traditional take-make-dispose approach to a greater holistic practice, where valuable and/or scarce substances are recovered at the end of a product’s life. Life Cycle Assessment (LCA) is gaining wider attractiveness, as assessment of environmental impacts constitutes an effective quantitative decision tool to identifying sustainable solutions. At the same time, existing guidelines, technical specifications and methods for LCA assessment at EoL are rather heterogeneous regarding modelling and calculation of related secondary material and energy streams. For construction products, category rules for Environmental Product Declarations (EPD) according to EN 15804 (issued through the European Committee for Standardization) and the Product Environmental Footprint (PEF) (developed by the European Commission) currently represent the most advanced methodological references. The study presents the methodological approach per EN 15804, describing the benefits and loads beyond the typical disposal stage. Thus, the environmental impacts of a construction element can be credited in accord to its material and energetic recycling potential. An applied model is realized for water pipes made of composite material. The calculation is exemplified and comparative results of allocation scenarios per EN 15804 and PEF are discussed, demonstrating correlations between the normative requirements and their application. The results support further identification, assessment and ranking of recycling alternatives (i.e. mechanical, thermal, chemical).

Numerical studies on ejector with swirl generator

This paper presents three-dimensional numerical studies of ejector with swirl generator (SG) using computational fluid dynamics (CFD) software, ANSYS, FLUENT 15.0. Performance analysis is carried out with two different configurations of swirl generators, namely solid vane type and cavity type. As expected, swirl increases the entrainment performance due to better momentum exchange between the motive and secondary streams compared to the ejector without swirl generator. Also, it is confirmed from the studies that, cavity type SG, imparts higher swirl strength to the flow stream than that of the solid vane type, due to the sweep angle in addition to the camber angle. Hence the studies are further extended with cavity type SG, at camber angle of 10° with various sweep angles like 10°, 20° and 30°, for analyzing the swirl effect over the performance of the ejector. The increase in entrainment ratio observed is about 15% with SG, compared to ejector without SG.

Development of a methodology for obtaining physiologically complete drinking water

The current state of the problem of diselementosis in the territory of the Russian Federation is analyzed and a list of elements is identified, the lack of which in food and water has a negative impact on human health. The author substantiates the development of a technique for conditioning drinking water to achieve its physiological usefulness and prevent diselementosis among servicemen who serve in the Arctic zone of the Russian Federation, where snowmelt is the source of drinking water. A salt composition was selected for conditioning low-mineralized water. For this, the initial stream of low-mineralized water is divided into two approximately equal secondary waters, and those mineralizing components that form sparingly soluble compounds are introduced into different secondary streams, which are then combined in a common tank. It is shown that for all the criteria studied, conditioned water meets the requirements of chemical safety Sanitary rules and regulations 2.1.4.1074-01, and also contains essential macro- and microelements in quantities corresponding to the standards of physiological potency of drinking water according to Sanitary rules and regulations 2.1.4.1116-02. The method of conditioning drinking water when it is introduced into the practice of water supply for servicemen of the Ministry of Defense of the Russian Federation will improve the quality of drinking water by enriching with essential macro- and microelements, increasing its physiological usefulness, which will serve as an effective measure to prevent the morbidity of servicemen due to the imbalance of nutrient elements in the body.

Technical and environmental assessment of selective recovery of tin and lead from waste solder alloy using direct anodic oxidation

The current study aimed the selective recovery of tin and lead from waste SnPb alloy obtained as a secondary stream in the recovery process of copper from waste printed circuit boards. The recovery of the two metals was achieved through selective direct anodic dissolution of the waste SnPb alloy samples in H2SO4 solutions coupled with the simultaneous electrowinning of a tin rich cathodic deposit. The optimal operating conditions were identified based on the influence of current density, H2SO4 concentration and electrolyte flow rate on the main technical performance indicators. The most favorable operating conditions for the electrochemical process were obtained at 0.5 M H2SO4 concentrations, 60 A/m2 current density and at a flow rate of 45 mL/min. Based on the experimental results the process was scaled-up, modeled and simulated using process flow modeling software CHEMCAD. The mass balance data corresponding to the recycling of 100 kg/h waste solder in the identified optimal operating conditions was used for the environmental assessment of the process. The General Effect Indices, for the input and output streams of the process, obtained through the Biwer-Heinzle method indicate that the developed recovery process it is not only efficient but environmental friendly as well.

Selective recovery of cobalt from the secondary streams after NiMH batteries processing using Cyanex 301

Cobalt is considered to be a critical raw material for the European Union. Since it has limited supply, substantial efforts should be made to develop sustainable methods to recover cobalt from alternative sources. Hydrometallurgical processing of spent NiMH batteries generates a concentrated stream containing, preferably, Co (11.8 g/L) and impurities (2.3 g/L Ni, 0.2 g/L Al, 9.3 g/L Mn and 4.6 g/L rare earth elements) in the nitric acid media. In this study, the selective separation of Co from the other ions present was investigated. Co was selectively separated from Al, Mn and REEs using 1 M Cyanex 301 in kerosene. The different kinetic behaviour during extraction with Cyanex 301 was utilized to separate Co and Ni ions selectively. The calculated ΔH for the Co extraction process equals – 11.37 ± 0.5 kJ/mol, which indicates that the extraction of Co in the system tested is an exothermic reaction. The effect of temperature on the Co extraction was used to obtain better selectivity towards Ni. Co was recovered by selective stripping with 4 M HCl at ambient temperature. The final purity of the stripping product was 99.9%.

Outcomes of the PELGRIMM project on Am-bearing fuel in pelletized and spherepac forms

The PELGRIMM project was a FP7-European project (funded by the European Commission, Grant Agreement No. 295664), carried out from 2012 to 2017. It was devoted to the investigation of spherepacked and pelletized fuel forms for Minor Actinide transmutation in homogeneous and heterogeneous recycling modes. PELGRIMM aimed at constituting a new step in the long term process in the assessment of Minor Actinide-bearing fuel, initiated within the European projects ACSEPT, F-BRIDGE, CP-ESFR and FAIRFUELS. The present paper provides an overview of the main technical outcomes gained within PELGRIMM. The developments of alternative processes in order to simplify synthesis routes and to limit secondary waste streams for Minor Actinide-bearing fuel preparation are detailed. The first results of behaviour under irradiation of spherepacked and pelletized fuel forms are provided from Post-Irradiation Examinations on (U,Pu,Am)O2 and (U,Am)O2 fuels respectively irradiated during SPHERE and MARIOS experiments, along with the description of the latest irradiation experiment, MARINE. In parallel, the capabilities of existing models and calculation codes have been improved to describe Minor Actinide-bearing fuel behaviour under irradiation in a more reliable way, and their predictive results have been compared to available Post-Irradiation Examinations. Finally, to start linking fuel behaviour with core neutronic problematics, a preliminary design of a Sodium-cooled Fast Reactor core loaded with spherepacked (U,Pu,Am)O2 fuels was built and correlated preliminary safety assessments have been performed.

Calibration and validation of and results from a micro-simulation model to explore drivers’ actual use of acceleration lanes

This study investigates the actual use of acceleration lanes by means of traffic micro-simulations in proximity to the convergence between the main and the secondary traffic streams.The data needed to develop the micro-simulation model were collected videotaping two acceleration lanes of an Italian highway, near the village of San Liberato. The relevant microsimulation model has been developed utilizing a commercial software, the TransModeler traffic simulation package, while the calibration and validation phases have been realized based on real-life data.Thanks to the microsimulation model, six different scenarios based on various presentation speeds have been analyzed, in a less expensive, quicker and more secure way compared to field observations. A quantitative and qualitative analysis of the results has been discussed to examine both geometric and kinematic aspects of the merging maneuvers and to compare road users' behaviors with theoretical road design guidelines. The analyses have been focused on vehicles coming from the on-ramp, in terms of entrance points dispersion into the main traffic stream along the acceleration lanes, merging speeds, and reached acceleration rates. The mutual influence between the two flows (main and secondary traffic streams), combined with vehicle performances and characteristics of drivers, led to a first assessment of the main variables from which the required length of the specialized lanes depends.

Exploring “Internet+Recycling”: Mass balance and life cycle assessment of a waste management system associated with a mobile application

Individual users cannot readily access the collection channels is a persistent problem in municipal solid waste (MSW) management, resulting in low MSW collection rates. A new waste management model, “Internet+Recycling”, has come into being; this model enables individuals to arrange collection appointment through various online platforms, then the collectors pick up the waste on-site. It is believed that “Internet+Recycling” can be a solution to mitigate the collection barrier in MSW management, as it provides individuals a convenient access to formal waste management systems. However, whether this emerging MSW collection model would bring environmental benefits is yet unknown. We here quantitatively examine the mass balance and environmental performance of MSW recycling associated with the use of such a “Internet+Recycling” mobile application - Aibolv. All transactions occurred on the mobile application within a period of six monthare included, and all related activities are modeled using the methodology that combines material flow analysis (MFA) and life cycle assessment (LCA). According to the extant MSW management legislation in China, we classify the collected MSW into three categories, subsidized waste electric and electronic equipment (WEEE) like television and refrigerator – T1, unsubsidized WEEE like mobile phone – T2, and other recyclables like paper and fabric – T3. The MFA results show that plastics and common metals are the dominate secondary material streams, and glass, precious metals and battery metals are mainly recovered from WEEE. The LCA results indicate that the disposal of the T2 waste has the highest environmental savings, due to the recovery of precious metals. Increased remanufacturing rates impart negative impacts, while increments in the quantity of spent mobile phones could significantly improve overall environmental performance. Based on the acquired results, recommendations are provided for facilitating the future development of “Internet+Recycling”, and limitations of this work are identified as well.

The compound-choking theory as an explanation of the entrainment limitation in supersonic ejectors

While the limitation of the entrainment ratio in supersonic ejectors is a well-known phenomenon, there is still a need to gain insight on the choking phenomena at play in on-design operation. In state-of-the-art simplified models of supersonic ejectors, the secondary stream is assumed to reach sonic velocity in a hypothetical throat (Fabri-choking). However, an alternative explanation of the entrainment limitation known as the compound-choking theory states that a nozzle flow with two streams at different stagnation pressures may be choked with a subsonic stream if the other one is supersonic. In this paper, the compound-choking is highlighted in a supersonic ejector through a thorough analysis of numerical simulations validated against experimental data. In addition, comprehensive experimental data of supersonic ejectors are used to assess the performance of the compound-choking theory to predict the entrainment ratio in the on-design regime in various configurations. Most predictions are in the ±10% range when compared to the experimental data. Compared to state-of-the-art 1D models relying on the Fabri-choking assumption, the compound-choking theory is shown to generally perform better regarding the prediction of the on-design entrainment ratio. This study suggests that the compound-choking theory is well suited to model the choking process in supersonic ejectors.

Demand-side management via optimal production scheduling in power-intensive industries: The case of metal casting process

The increasing challenges to the grid stability posed by the penetration of renewable energy resources urge a more active role for demand response programs as viable alternatives to a further expansion of peak power generators. This work presents a methodology to exploit the demand flexibility of energy-intensive industries under Demand-Side Management programs in the energy and reserve markets. To this end, we propose a novel scheduling model for a multi-stage multi-line process, which incorporates both the critical manufacturing constraints and the technical requirements imposed by the market. Using mixed integer programming approach, two optimization problems are formulated to sequentially minimize the cost in a day-ahead energy market and maximize the reserve provision when participating in the ancillary market. The effectiveness of day-ahead scheduling model has been verified for the case of a real metal casting plant in the Nordic market, where a significant reduction of energy cost is obtained. Furthermore, the reserve provision is shown to be a potential tool for capitalizing on the reserve market as a secondary revenue stream.