Waste Material Recycling in the Circular Economy

This book highlights current challenges and developments in waste material recycling in the framework of a circular economy. The increase in the standard of living has resulted in the large consumption of several materials, mainly polymers. Therefore the problem of waste recycling, specifically polymer recycling, in an environmentally friendly way is more urgent than ever. Nowadays, more specialized recycling methods are required to manage a wide variety of wastes. Over fourteen chapters in three sections, this book addresses such topics as chemical recycling techniques, recycling of polyethylene, denim production and recycling, valorization of waste materials, urban mining, the circular economy, and much more

Acetaldehyde generation in preforms with the use of recycled PET

Dissertação de mestrado integrado em Engenharia de PolímerosThe production and recycling process for polyethylene terephthalate (PET) bottles for packaging soft drinks and mineral waters is still growing worldwide and improving constantly. Although, during the melting and processing of PET, especially recycled PET (rPET), degradation of the material occurs. The result of the degradation reactions is a severe drop in the molecular weight, which leads to the failing of intrinsic viscosity, melt strength and melt processability and finally, to poor usage properties and a low quality of the bottles obtained. One of the most common degradation products is acetaldehyde (AA). Due to its low boiling point, 21°C, AA is able to diffuse out of PET into the beverage content of the PET bottle. The diffusion of AA into packaged contents is of concern due to its limited threshold for the taste and odour that can be detected by consumers. The purpose of this study is to examine the AA generation, the failing of the intrinsic viscosity and the colour degradation from reprocessed rPET when exposed to different drying and injection conditions. An initial model was developed to analyse the interaction, magnitude and influence of each processing condition in a twin-tower desiccant dryer and a mono-cavity PET preform injection moulding system. It was found an optimal condition capable of reducing AA concentration in the preform, without compromising a significant failing of the intrinsic viscosity, with minimal impact in colour degradation. The modification of an existing drying and injection moulding program was applied under the optimal result given by the model and additional studies regarding moisture content and intrinsic viscosity were conducted. AA was reduced by 61% after drying, while the drop in the intrinsic viscosity was significantly reduced by heat preservation of the settled drying temperature. There was no significant impact in colour observed. An agreement between the modelling results and observed trends from mono-cavity injection moulding was achieved. The groundwork was placed and made further improvements in the industrial production of preforms containing 100% content of recycled PET.O processo de produção e reciclagem de garrafas em polietileno tereftalato (PET) em vários continua a crescer exponencialmente, fruto de um processo de aperfeiçoamento constante. No entanto, aquando do seu processamento e transição para o estado fundido, ocorre degradação do material, particularmente quando se utiliza PET reciclado (rPET). O resultado das reações de degradação traduz-se numa queda acentuada no peso molecular, levando a uma falha na viscosidade intrínseca, resistência do fundido e processabilidade do mesmo. Por consequência, a degradação do material nestas condições resulta em pobres qualidades do material em serviço e uma baixa qualidade das garrafas obtidas. Um dos produtos de degradação mais comuns é o acetaldeído (AA). Devido ao seu baixo ponto de ebulição, 21 ° C, o AA é capaz de se difundir do PET para o conteúdo da garrafa. Este processo de difusão de AA é preocupante porque altera o sabor e odor do conteúdo embalado e pode ser facilmente detetados pelos consumidores. O objetivo deste estudo é examinar a geração de AA, a falha na viscosidade intrínseca e a degradação de cor do rPET quando exposto a diferentes condições de secagem e moldação por injeção. Um modelo estatístico inicial foi desenvolvido para analisar a interação, magnitude e influência de cada condição de processamento de um sistema de moldagem por injeção e de secagem de dois tipos de rPET na produção de pré-formas. Foi encontrada uma condição ótima capaz de reduzir a concentração de AA na pré-forma, sem comprometer uma falha significativa da viscosidade intrínseca, com impacto mínimo na degradação da cor. A modificação das condições existentes de secagem e moldagem por injeção foi aplicada sob o resultado ótimo obtido pelo modelo, onde estudos adicionais sobre o teor de humidade e viscosidade intrínseca foram posteriormente realizados. O AA foi reduzido em 61% após a secagem e a queda na viscosidade intrínseca foi significativamente reduzida pela preservação da temperatura de secagem estabelecida. Não houve impacto significativo na cor observada. Atingiu-se um compromisso entre os resultados do programa estatístico e as tendências observadas na moldagem por injeção. A base foi lançada e foram feitas novas melhorias na produção industrial de pré-formas com 100% de teor de PET reciclado

The on line determination of mercury in process streams using atomic spectrometry

On-line systems for monitoring mercury in liquid and gaseous production and waste streams have been developed, utilising atomic fluorescence spectrometry (AFS) as the basis for detection. Instrumentation has been designed for unattended continuous operation. Laboratory chemistries for the vapour generation of mercury, normally performed off-line in batch mode, have been adapted and optimised for continuous, flow-injection analysis for varying sample types and chemical forms of mercury. The system has typical analysis cycle of 7 minutes, a limit of detection of 10 pg ml ˉ¹ a linear range up to 100 µg ml ˉ¹ and has been applied in industrial environments for the continuous monitoring of mercury in incineration wastewater and sulphuric acid. The system was validated by on-site trials for periods of one week, during which time comparative off-line laboratory measurements showed good agreement. An automated system for monitoring mercury in natural gas streams has also been developed and validated by laboratory and on-site industrial trials. A heated pressure let-down system was designed in order to facilitate sampling of high-pressure gas streams without condensation of heavier fractions. The heated sampling line was interfaced with an automated system for trapping mercury, from variable volumes of gas, onto gold amalgamation traps, with subsequent desorbtion and analysis by AFS. The method detection limit for a 58 litre sample of natural gas was 30 pg m ˉ³ which was sufficient to determine residual mercury in natural gas streams even after mercury scrubbing had been performed. The system was validated by laboratory trials and spiking experiments during on-site trials at a gas processing facility, which resulted in complete installation and commissioning.P.S. Analytical Ltd, Orpington, UK and Teaching Company Directorate, Oxford, U

Characterization of shrinkage effects in micro-injection moulding (µ-IM)

This thesis characterizes the effects on shrinkage in microinjection moulding. The literature review considers four branches of investigation (material properties, processing parameters, mould design and specimen design). Two research gaps rise from the analysis of the literature review: the absence of a standardized methodology for measuring shrinkage of moulded parts at the micro-scale, and the absence of optimization stage that implements multiple quality criteria. Adequate research routes are set in order to address these gaps. The conventional standard for determining shrinkage at the macro scale is adapted to the micro-scale and this bridges the first gap. The micro-mould replicates the same design of the standard, and a preliminary stage solves some mouldability problems: the implemented mould extended the mouldability range of processing parameters for improving the reliability of results. After the micro-mould validation, the study of shrinkage at the micro-scale considers the influence of five processing parameters: the mould and melt temperature, the holding time and pressure, then the injection pressure. The design of experiment approach identifies the critical parameters that affect moulding, post-moulding and total shrinkage in parallel to and normal to the flow direction within an interval of confidence of 95% for POM and 90% for 316L feedstock. Statistical tools analyse the results, and the trends of critical factors found confirmation in the literature. This methodology at the micro-scale can fill the first gap because it is on purpose designed for the micro-scale. Moreover, the binder of feedstock is a mixture of POM based polymers, and the use of a common platform permits to compare directly the two materials and highlight the influence of powder loading. The optimization stage adopts desirability functions for achieving optimized values that simultaneously fulfil two requests: minimize shrinkage and maximize moulded part mass. The analysis of the literature review shows that few papers adopt multiple quality criteria approach as methodology for optimizing the results, and none consider jointly part mass and shrinkage. The optimized processing parameters allow moulding “optimized specimens”, and results demonstrate that their total shrinkage and part mass achieve the requests. Even if the use of desirability functions produce results thatrepresents a compromise between the requests, the results show that overall shrinkage decreases and part mass increases. This approach demonstrates its reliability and bridges the second gap. The last part of the thesis investigates the 316L feedstock behaviour for filling micro-features parallel to and normal to the flow oriented. The moulded features are investigated for studying the replication quality and the effect of the orientation of channels with dimension close to the feedstock lower mouldability value. These informations are available in the literature only for polymers, and the contribution of this part of thesis is to fill this gap by analysing a feedstock. The statistical approach permits to identify the critical factors that affect the feature replication quality. Optical investigations allow to identify the 316L feedstock lower mouldability value and to observe the influence of the orientation of features with dimensions near the lower limit

KEER2022

Avanttítol: KEER2022. DiversitiesDescripció del recurs: 25 juliol 202

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018

Modelling and sustainability analysis of biorefineries using sugarcane lignocellulose to produce polyethylene, sorbitol, glucaric acid and levulinic acid at existing South African sugar mills

Thesis (PhD)--Stellenbosch University, 2021.ENGLISH ABSTRACT: The sugar industry in South Africa and the region has been plagued by factors including the low international sugar prices, reduced cane yields due to climate change and competition from new market entrants producing sweeteners. Therefore, to remain relevant and sustainable, this industry seeks to generate extra revenue by producing bio-based chemicals and bio-energy from part of the bagasse and brown leaves in biorefinery complexes, alongside sugar products. Using a rapid screening approach, bio-based chemicals polyethylene, sorbitol, glucaric acid and levulinic acid were shortlisted for possible production in such biorefineries (objective one). Conceptual biorefinery process flow diagrams were designed in Aspen Plus® v 8.6 producing the aforementioned chemicals with electricity cogeneration in combined heat and power plants, annexed to a conventional sugar mill (objective two), including a base case scenario that only produced electricity. This was followed by determining the techno-economic viability of the bio-energy self-sufficient biorefineries using developing countries’ economic parameters and a discounted cash flow rate of return methodology on real terms using a 9.7% hurdle rate that reflects South Africa’s and developing countries’ economic conditions (objective three). The internal rate of return (IRR), net present value (NPV) and minimum product selling price (MPSP) were indicators used to determine profitability. The most economically viable scenario coproduced levulinic acid, gamma valerolactone, furfural and electricity (LA-GVL-F-E) and attained a 23% IRR and US$253 million NPV at a 9.7$ 139 million. At present, most second generation bio-based chemicals cannot compete with first generation or fossil–based counterparts due to the large capital investment costs associated with processing lignocelluloses. A substantial premium is required on second-generation bio-based products if they are to compete with fossil-based or first generation products. In addition to economic viability, the overall sustainability of profitable biorefineries was assessed based on their environmental and social impacts (i.e. job creation) in objective four. For the environmental impact, a “cradle to factory gate” life cycle assessment in SimaPro® was used and the AWARE methodology applied for the water footprint. The most sustainable scenario produced glucaric acid via dilute acid pretreatment (Glucaric.DA) followed by LA-F-E. Objective five was a multi criteria decision assessment (MDCA) on profitable scenarios that ranked and scored the biorefineries based on equal and varied national sustainable (economic, environmental and social) representative weightings. When equal representative weightings of 33.33% were applied to the sustainability indicators, scenario LA-F-E attained the highest aggregate score followed by Glucaric.DA and Sorbitol.DA (chemicals produced via dilute acid pretreatment) and lastly, LA-GVL-F-E. The generated results can inform key sugar industry stakeholders of the most sustainable biorefineries for future feasibility studies. Therefore, potential exists at typical sugar mills for the sustainable valorisation of lignocelluloses for revenue generation and the advancement of a green economy. Future studies should investigate the sustainability of biorefineries utilising first and second generation feedstocks and also valorising part of the lignin to produce high-value chemicals.AFRIKAANSE OPSOMMING: Die suikerindustrie in Suid-Afrika en die streek word deur faktore geteister soos die lae internasionale suikerpryse, verlaagde rietopbrengs as gevolg van klimaatsverandering en kompetisie van nuwe markdeelnemers wat versoeters vervaardig. Daarom, om relevant en volhoubaar te bly, poog die industrie om ekstra inkomste te genereer deur bio-gebaseerde chemikalieë en bio-energie uit ’n gedeelte van die bagasse en bruin blare in bioraffinaderykompleks, saam met suikerprodukte, te produseer. Deur ’n vinnige siftingsbenadering, is bio-gebaseerde chemikalieë poliëtileen, sorbitol, suikersuur en levuliniensuur gekortlys vir moontlike produksie in sulke bioraffinaderye (doelwit 1). Konsepsuele bioraffinaderyprosesvloeidiagramme is ontwerp in Aspen Plus® v 8.6 wat die voorafgenoemde chemikalieë met elektrisiteitkogenerasie produseer in aanlegte wat hitte en krag kombineer, geannekseer aan ’n konvensionele suikermeul (doelwit 2), insluitend ’n basis scenario wat slegs elektrisiteit produseer. Dit is gevolg deur die bepaling van die tegno-ekonomiese uitvoerbaarheid van die bio-energie selfonderhoudende bioraffinaderye deur ontwikkelende lande se ekonomiese parameters te gebruik, en ’n korting op kontantvloeiopbrengsmetodologie op reële terme deur ’n 9.7% versperringskoers te gebruik wat Suid-Afrika en ontwikkelende lande se ekonomiese kondisies reflekteer (doelwit 3). Die interne opbrengskoers (IRR), netto huidige waarde (NPV) en minimum produkverkoopsprys (MPSP) was indikators wat gebruik is om winsgewendheid te bepaal. Die mees ekonomies uitvoerbare scenario het levuliniensuur, gamma valerolaktoon, furfuraal en elektrisiteit (LA-GVL-F-E) koproduseer en het ’n 23% IRR en US$253 miljoen NPV gehad by ’n 9.7$139 miljoen. Tans kan meeste tweede-generasie bio-gebaseerde chemikalieë nie met eerste generasie of fossiel-gebaseerde teenbeelde kompeteer nie as gevolg van die groot kapitaalbeleggingkostes geassosieer met prosessering van lignosellulose. ’n Aansienlike premie word vereis op tweede-generasie bio-gebaseerde produkte as hulle met fossiel-gebaseerde of eerste-generasie produkte wil kompeteer. Saam met ekonomiese uitvoerbaarheid, is die algehele volhoubaarheid van winsgewende bioraffinaderye geassesseer gebaseer op hul omgewings- en sosiale impak (i.e. werkskepping) in doelwit 4. Vir die omgewingsimpak is ’n lewenssiklusanalise van die “begin tot fabriekshek” in SimaPro® gebruik en die AWARE-metodologie toegepas vir die watervoetspoor. Die mees volhoubare scenario het suikersuur via verdunde suur voorbehandeling (Glucaric.DA) produseer, gevolg deur LA-F-E. Doelwit vyf was ’n multikriteriabesluitassessering (MDCA) op winsgewende scenario’s wat bioraffinaderye rangskik en punte gee gebaseer op gelyke en gevarieerde nasionale volhoubaarheid (ekonomies, omgewing, en sosiaal) verteenwoordigende gewigstoekennings. Toe gelyke verteenwoordigende gewigstoekennings van 33.33% toegepas is op die volhoubaarheidsindikators, het scenario LA-F-E die hoogste aggregaattelling behaal, gevolg deur Glucaric.DA en Sorbitol.DA (chemikalieë geproduseer via verdunde suur voorbehandeling), en laaste, LA-GVL-F-E. Die gegenereerde resultate kan sleutel suikerindustriebelanghebbers van die mees volhoubare bioraffinaderye inlig vir toekomstige uitvoerbaarheidstudies. Potensiaal bestaan daarom by tipiese suikermeule vir die volhoubare valorisasie van lignosellulose vir inkomstegenerasie en die bevordering van ’n groen ekonomie. Toekomstige studies moet die volhoubaarheid van bioraffinaderye wat eerste- en tweede-generasie toevoermateriale gebruik, ondersoek, en ook die valorisering van ʼn gedeelte van die lignien om hoë waarde chemikalieë te produseer.The financial assistance of the National Research Foundation (NRF) towards this research is hereby acknowledged. Opinions expressed and conclusions arrived at, are those of the author and are not necessarily attributed to the NRF

Fire performance of residential shipping containers designed with a shaft wall system

seven story building made of shipping containers is planned to be built in Barcelona, Spain. This study mainly aimed to evaluate the fire performance of one of these residential shipping containers whose walls and ceiling will have a shaft wall system installed. The default assembly consisted of three fire resistant gypsum boards for vertical panels and a mineral wool layer within the framing system. This work aimed to assess if system variants (e.g. less gypsum boards, no mineral wool layer) could still be adequate considering fire resistance purposes. To determine if steel temperatures would attain a predetermined temperature of 300-350ºC (a temperature value above which mechanical properties of steel start to change significantly) the temperature evolution within the shaft wall system and the corrugated steel profile of the container was analysed under different fire conditions. Diamonds simulator (v. 2020; Buildsoft) was used to perform the heat transfer analysis from the inside surface of the container (where the fire source was present) and within the shaft wall and the corrugated profile. To do so gas temperatures near the walls and the ceiling were required, so these temperatures were obtained from two sources: (1) The standard fire curve ISO834; (2) CFD simulations performed using the Fire Dynamics Simulator (FDS). Post-flashover fire scenarios were modelled in FDS taking into account the type of fuel present in residential buildings according to international standards. The results obtained indicate that temperatures lower than 350ºC were attained on the ribbed steel sheet under all the tested heat exposure conditions. When changing the assembly by removing the mineral wool layer, fire resistance was found to still be adequate. Therefore, under the tested conditions, the structural response of the containers would comply with fire protection standards, even in the case where insulation was reduced.Postprint (published version