fi=218 Ympäristötekniikka|sv=218 Miljöteknik|en=218 Environmental engineering|https://www.doria.fi:443/handle/10024/916632024-03-28T00:15:37Z2024-03-28T00:15:37ZLife Cycle Assessment of Plastic Waste, its Treatment, and Application of the Upcycled Product : A Comprehensive Circular ApproachHameed Sultan Akbar Ali, Ashiq Ahamedhttps://www.doria.fi:443/handle/10024/1813782021-12-03T09:51:09Z2021-06-11T09:43:08ZLife Cycle Assessment of Plastic Waste, its Treatment, and Application of the Upcycled Product : A Comprehensive Circular Approach
Hameed Sultan Akbar Ali, Ashiq Ahamed
Plastic waste management is a growing global problem. Single-use flexible packaging plastic waste (FPPW) is one of the most challenging types of plastic waste to recycle due to its mixed composition (including bags, containers and films made of LDPE, HDPE, PP, PET and other materials), multi-material characteristic (multiple thin layered plastics adhered together for a single packaged product), and associated impurities (inks, adhesives and residual impurities from the packaged product). This type of plastic waste is often discarded as non-recyclable from the mechanical recycling streams. However, the use of plastics is unavoidable as the benefits outweigh other viable alternative materials in various applications. In this research, three holistic and comprehensive assessments have been conducted, including the (i) life cycle of plastic production and application, (ii) end-of-life pyrolysis treatment and upcycling to carbon nanotubes (CNTs), and (iii) application of CNTs in electrochemical sensing and end-of-life disposal of the CNTs, in order to address the FPPW management.
The specific case of the life cycle assessment (LCA) of grocery bags indicated that the environmental footprint of plastics is lower than the other prevailing alternatives, including cotton and paper, from the perspective of a metropolitan city with end-of-life incineration treatment. However, incineration of the plastic waste abnegates the circularity of material flow. Hence, a feasible and versatile integrated pyrolysis technology was developed for the FPPW treatment. The pyrolysis of plastics was evaluated using incineration ashes as a reforming catalyst in order to valorize the application of incineration ashes and to alleviate the environmental footprint associated with the utilization of synthetic catalysts. The incineration ashes demonstrated potential to be applied as a reforming catalyst in the pyrolysis of plastics to produce oil and non-condensable gas. However, further advancements in the form of pre-treatments are essential to generate performance comparable to commonly used zeolite catalysts. The LCA of the integrated pyrolysis process along with the upcycling of non-condensable gases from pyrolysis of FPPW to CNTs concluded superior environmental benefits when compared to the conventional pyrolysis of FPPW without CNTs synthesis. Notably, the integration of CNTs synthesis with the conventional pyrolysis process benefitted with diminishing the environmental footprint in terms of climate change, human toxicity, fossil depletion, ionizing radiation, and terrestrial ecotoxicity potentials. The inflexion point for the CNTs yield was identified as >2 wt.% to generate a positive effect on the environment.
Pyrolysis treatment of different waste fractions without significantly compromising the product quality highlighted the versatility of the integrated pyrolysis process. Furthermore, the synthesis of novel waste-derived CNTs (WCNTs) provides an additional revenue stream for the pyrolysis plants, enhancing their economic feasibility.
Subsequently, the synthesized WCNTs were tested in electrochemical sensing using screen-printed electrodes (SPEs) due to its enormous growth potential in diverse future applications. The electrochemical performance of WCNTs was comparable to the commercial CNTs in the detection ofheavy metals, therefore, corroborating WCNTs as a viable alternative in SPEs application. The LCA determined that the WCNTs demonstrated considerable environmental advantages in comparison with the predominantly used noble metals, including gold and platinum, as electrode material. Therefore, substitution of the noble metals by WCNTs is recommended.
In conclusion, the integrated LCA approach provided context of the accrued benefits of high-value CNTs derived from plastic waste. Furthermore, the integrated LCA approach provides a measure to enhance the circularity of the material flow by identifying suitable alternatives, accentuating recycling and upcycling technologies, and determining hotspots for improvement, thereby, facilitating the environmental sustainability. The method helps to improve the recycling rates and alleviate the existing unsustainable consumption patterns. Importantly, similar LCA studies are unique and crucial to advance towards a truly circular economy and achieve the sustainable development goals.
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Behandling av plastavfall är ett växande globalt problem. Plastavfall bestående av flexibla engångsförpackningar (FPPW) är en av de mest utmanande typerna av plastavfall att återanvända på grund av dess blandade sammansättning (inkl. påsar, behållare och filmer av LDPE, HDPE, PP, PET och andra material), multimaterialegenskaper (flera tunna plaster sammanfogade i en enskild förpackningsprodukt) och orenheter (färger, lim och kontaminationer från den förpackade produkten). Denna typ av plastavfall avskiljs ofta som icke-återanvändbart från de mekaniska återanvändningsströmmarna. Användning av plaster är dock oundvikligt eftersom fördelarna överträffar andra möjliga alternativa material i många olika tillämpningar. I denna forskning har en holistisk, utförlig och integrerad studie genomförts inkl. livscykeln för plastproduktion, tillämpning, slutbehandling genom pyrolys, upparbetning till kolnanotuber (CNT), tillämpning av CNT i elektrokemiska sensorer, och slutförvaring av CNT, för att analysera behandlingen av FPPW.
Det specifika fallet gällande livscykelanalys (LCA) av plastkassar indikerade att det miljömässiga fotavtrycket av plast är lägre än för andra nuvarande alternativ, såsom bomull och papper, ur ett storstadsperspektiv med slutförbränning av avfall. Förbränning av plastavfall avviker dock från den cirkulära materialströmmen. Därför utvecklades en användbar, mångsidig och integrerad pyrolysteknologi för behandling av FPPW. Pyrolys av plast utvärderades genom användning av förbränningsaska som reformeringskatalysator för att uppgradera användningen av förbränningsaskor och för att minska det fotavtryck på miljön som användningen av syntetiska katalysatorer förorsakar. Förbränningsaskorna visade sig vara potentiellt användbara som en reformeringskatalysator vid pyrolys av plast för framställning av olja och icke-kondenserbara gaser. Ytterligare framsteg gällande förbehandling behövs dock för att upnå en prestanda som är jämförbar med vanligen använda zeolit-katalysatorer. En livscykelanalys (LCA) av den integrerade pyrolysprocessen tillsammans med uppgradering av icke-kondenserbara gaser från pyrolys av FPPW till CNT gav överlägsna miljöfördelar jämfört med konventionell pyrolys av FPPW utan syntes av CNT. Det var anmärkningsvärt att integreringen av CNT-syntesen med den konventionell pyrolysprocessen hade fördelen att minska det miljömässiga fotavtrycket i fråga om klimatförändring, toxicitet för människan, utarmning av fossila råvaror, joniserande strålning och ekotoxiciteten på land. Inflektionspunkten för utbytet av CNT identifierades vi till >2 vikt-% för att åstadkomma en positiv effekt på miljön. Pyrolysbehandling av olika avfallsfraktioner utan att märkbart försämra produktkvaliteten underströk den integrerade pyrolysprocessens mångsidighet. Framställning av nya CNT (WCNT) utgående från avfall erbjuder dessutom en extra inkomstkälla för pyrolysanläggningen, vilket förbättrar de ekonomiska förutsättningarna.
Följande steg var att testa framställd WCNT i elektrokemiska sensorer i form av av ”screen-printade” elektroder (SPE) på grund av deras enorma tillväxtpotential inom diverse framtida tillämpningar. Den elektrokemiska prestandan hos WCNT var jämförbar med kommersiell CNT vid detektering av tungmetaller, vilket visar att WCNT är ett beaktansvärt alternativ inom SPE-tillämpninar. Livscykelanalysen (LCA) visade att WCNT hade avsevärda miljöfördelar jämfört med de mest använda ädelmetallerna, såsom guld och platina, som elektrodmaterial. Därför rekommenderas att ädelmetaller
ersätts med WCNT.
Sammanfattningsvis kan nämnas att den integrerade livscykelananlysen (LCA) kunde påvisa fördelarna med värdefull CNT som framställdes från plastavfall. En integrerad LCA erbjuder ytterligare en metod för att förbättra cirkulariteten i materialströmmarna genom att identifiera lämpliga alternativ med betoning på teknologier för återanvändning och uppgradering, samt bestämning av centrala saker att förbättra, för att på så sätt gynna en miljömässig hållbarhet. Metoden hjälper till att förbättra återanvändningsgraden och att åtgärda de existerande ohållbara konsumtionssätten. Det är viktigt att notera att liknande LCA studier är unika och oumbärliga för att uppnå en verkligt cirkulär ekonomi och att uppnå hållbara utvecklingsmål.
2021-06-11T09:43:08ZSustainable steelmaking by process integrationGhanbari Toudeshki, Hamidhttps://www.doria.fi:443/handle/10024/1011112020-08-27T08:51:51Z2014-11-11T08:09:44ZSustainable steelmaking by process integration
Ghanbari Toudeshki, Hamid
Environmental issues, including global warming, have been serious challenges
realized worldwide, and they have become particularly important for the iron and steel
manufacturers during the last decades. Many sites has been shut down in developed
countries due to environmental regulation and pollution prevention while a large
number of production plants have been established in developing countries which has
changed the economy of this business.
Sustainable development is a concept, which today affects economic growth,
environmental protection, and social progress in setting up the basis for future
ecosystem. A sustainable headway may attempt to preserve natural resources, recycle
and reuse materials, prevent pollution, enhance yield and increase profitability. To
achieve these objectives numerous alternatives should be examined in the sustainable
process design. Conventional engineering work cannot address all of these substitutes
effectively and efficiently to find an optimal route of processing. A systematic
framework is needed as a tool to guide designers to make decisions based on overall
concepts of the system, identifying the key bottlenecks and opportunities, which lead to
an optimal design and operation of the systems.
Since the 1980s, researchers have made big efforts to develop tools for what today is
referred to as Process Integration. Advanced mathematics has been used in simulation
models to evaluate various available alternatives considering physical, economic and
environmental constraints.
Improvements on feed material and operation, competitive energy market,
environmental restrictions and the role of Nordic steelworks as energy supplier
(electricity and district heat) make a great motivation behind integration among
industries toward more sustainable operation, which could increase the overall energy
efficiency and decrease environmental impacts.
In this study, through different steps a model is developed for primary steelmaking,
with the Finnish steel sector as a reference, to evaluate future operation concepts of a
steelmaking site regarding sustainability. The research started by potential study on
increasing energy efficiency and carbon dioxide reduction due to integration of
steelworks with chemical plants for possible utilization of available off-gases in the
system as chemical products. These off-gases from blast furnace, basic oxygen furnace
and coke oven furnace are mainly contained of carbon monoxide, carbon dioxide,
hydrogen, nitrogen and partially methane (in coke oven gas) and have proportionally
low heating value but are currently used as fuel within these industries.
Nonlinear optimization technique is used to assess integration with methanol plant
under novel blast furnace technologies and (partially) substitution of coal with other
reducing agents and fuels such as heavy oil, natural gas and biomass in the system.
Technical aspect of integration and its effect on blast furnace operation regardless of
capital expenditure of new operational units are studied to evaluate feasibility of the
idea behind the research.
Later on the concept of polygeneration system added and a superstructure generated
with alternative routes for off-gases pretreatment and further utilization on a
polygeneration system producing electricity, district heat and methanol.
(Vacuum) pressure swing adsorption, membrane technology and chemical absorption
for gas separation; partial oxidation, carbon dioxide and steam methane reforming for
methane gasification; gas and liquid phase methanol synthesis are the main alternative
process units considered in the superstructure.
Due to high degree of integration in process synthesis, and optimization techniques,
equation oriented modeling is chosen as an alternative and effective strategy to previous
sequential modelling for process analysis to investigate suggested superstructure. A
mixed integer nonlinear programming is developed to study behavior of the integrated
system under different economic and environmental scenarios.
Net present value and specific carbon dioxide emission is taken to compare
economic and environmental aspects of integrated system respectively for different fuel
systems, alternative blast furnace reductants, implementation of new blast furnace
technologies, and carbon dioxide emission penalties. Sensitivity analysis, carbon
distribution and the effect of external seasonal energy demand is investigated with
different optimization techniques.
This tool can provide useful information concerning techno-environmental and
economic aspects for decision-making and estimate optimal operational condition of
current and future primary steelmaking under alternative scenarios. The results of the
work have demonstrated that it is possible in the future to develop steelmaking towards
more sustainable operation.
2014-11-11T08:09:44ZUtilization of steelmaking waste materials for production of calcium carbonate (CaCO3)Mattila, Hannu-Petterihttps://www.doria.fi:443/handle/10024/990112020-08-27T08:51:50Z2014-09-23T13:01:01ZUtilization of steelmaking waste materials for production of calcium carbonate (CaCO3)
Mattila, Hannu-Petteri
The steel industry produces, besides steel, also solid mineral by-products or slags, while it emits large quantities of carbon dioxide (CO2). Slags consist of various silicates and oxides which are formed in chemical reactions between the iron ore and the fluxing agents during the high temperature processing at the steel plant. Currently, these materials are recycled in the ironmaking processes, used as aggregates in construction, or landfilled as waste.
The utilization rate of the steel slags can be increased by selectively extracting components from the mineral matrix. As an example, aqueous solutions of ammonium salts such as ammonium acetate, chloride and nitrate extract calcium quite selectively already at ambient temperature and pressure conditions. After the residual solids have been separated from the solution, calcium carbonate can be precipitated by feeding a CO2 flow through the solution.
Precipitated calcium carbonate (PCC) is used in different applications as a filler material. Its largest consumer is the papermaking industry, which utilizes PCC because it enhances the optical properties of paper at a relatively low cost. Traditionally, PCC is manufactured from limestone, which is first calcined to calcium oxide, then slaked with water to calcium hydroxide and finally carbonated to PCC. This process emits large amounts of CO2, mainly because of the energy-intensive calcination step.
This thesis presents research work on the scale-up of the above-mentioned ammonium salt based calcium extraction and carbonation method, named Slag2PCC. Extending the scope of the earlier studies, it is now shown that the parameters which mainly affect the calcium utilization efficiency are the solid-to-liquid ratio of steel slag and the ammonium salt solvent solution during extraction, the mean diameter of the slag particles, and the slag composition, especially the fractions of total calcium, silicon, vanadium and iron as well as the fraction of free calcium oxide. Regarding extraction kinetics, slag particle size, solid-to-liquid ratio and molar concentration of the solvent solution have the largest effect on the reaction rate.
Solvent solution concentrations above 1 mol/L NH4Cl cause leaching of other elements besides calcium. Some of these such as iron and manganese result in solution coloring, which can be disadvantageous for the quality of the PCC product. Based on chemical composition analysis of the produced PCC samples, however, the product quality is mainly similar as in commercial products.
Increasing the novelty of the work, other important parameters related to assessment of the PCC quality, such as particle size distribution and crystal morphology are studied as well. As in traditional PCC precipitation process, the ratio of calcium and carbonate ions controls the particle shape; a higher value for [Ca2+]/[CO32-] prefers precipitation of calcite polymorph, while vaterite forms when carbon species are present in excess. The third main polymorph, aragonite, is only formed at elevated temperatures, above 40-50 °C.
In general, longer precipitation times cause transformation of vaterite to calcite or aragonite, but also result in particle agglomeration. The chemical equilibrium of ammonium and calcium ions and dissolved ammonia controlling the solution pH affects the particle sizes, too. Initial pH of 12-13 during the carbonation favors nonagglomerated particles with a diameter of 1 μm and smaller, while pH values of 9-10 generate more agglomerates of 10-20 μm.
As a part of the research work, these findings are implemented in demonstrationscale experimental process setups. For the first time, the Slag2PCC technology is tested in scale of ~70 liters instead of laboratory scale only. Additionally, design of a setup of several hundreds of liters is discussed. For these purposes various process units such as inclined settlers and filters for solids separation, pumps and stirrers for material transfer and mixing as well as gas feeding equipment are dimensioned and developed.
Overall emissions reduction of the current industrial processes and good product quality as the main targets, based on the performed partial life cycle assessment (LCA), it is most beneficial to utilize low concentration ammonium salt solutions for the Slag2PCC process. In this manner the post-treatment of the products does not require extensive use of washing and drying equipment, otherwise increasing the CO2 emissions of the process.
The low solvent concentration Slag2PCC process causes negative CO2 emissions; thus, it can be seen as a carbon capture and utilization (CCU) method, which actually reduces the anthropogenic CO2 emissions compared to the alternative of not using the technology. Even if the amount of steel slag is too small for any substantial mitigation of global warming, the process can have both financial and environmental significance for individual steel manufacturers as a means to reduce the amounts of emitted CO2 and landfilled steel slag.
Alternatively, it is possible to introduce the carbon dioxide directly into the mixture of steel slag and ammonium salt solution. The process would generate a 60-75% pure calcium carbonate mixture, the remaining 25-40% consisting of the residual steel slag. This calcium-rich material could be re-used in ironmaking as a fluxing agent instead of natural limestone. Even though this process option would require less process equipment compared to the Slag2PCC process, it still needs further studies regarding the practical usefulness of the products.
Nevertheless, compared to several other CO2 emission reduction methods studied around the world, the within this thesis developed and studied processes have the advantage of existing markets for the produced materials, thus giving also a financial incentive for applying the technology in practice.
2014-09-23T13:01:01ZReactive dissolution of sedimentary rocks in flue gas desulfurization : modeling and experimental investigationDe Blasio, Cataldohttps://www.doria.fi:443/handle/10024/663672020-08-27T08:51:51Z2010-12-21T11:47:46ZReactive dissolution of sedimentary rocks in flue gas desulfurization : modeling and experimental investigation
De Blasio, Cataldo
Svavel förekommer i kol och olja och oxideras vid förbränning till svaveldioxid (SO2). Årligen utsläpps stora mängder svaveldioxid som åstadkommer sura regn, minskning av stratosfäriskt ozon och sjukdomar. Av dessa orsaker är det nödvändigt att minska utsläppen av svaveldioxid. Den teknologi som rör planering av reaktorer och processer för rökgasavsvavling (FGD) har utvecklats kraftigt och idag använder man olika typer av lösningar. De vanligaste alternativen för FGD är våtskrubber- och semitorra skrubbersystem (Spray Dry Scrubbers, SDS) och injektionsprocesser för absorbenter. SDS-processer har studerats bland annat av Ahlbeck [4] och Klingspor [5] och injektionsprocesser av Alvfors [6]. Kalksten, som i huvusak består av kalciumkarbonat, används i rökgasavsvavling på grund av sin förmåga att binda svavel i form av sulfatsalter. Den vanligaste rökgasavsvavlingsmetoden är våtskrubbning, där det sedimentära stenmaterialets upplösningshastighet är en av de faktorer som påverkar resultatet mest. Utvärdering av kalkstensreaktivitet är därför speciellt viktig vid planering och drift av anläggningar för rökgasavsvavling.
Målsättningen med detta arbete var att modellera upplösningen av olika typers kalksten för att få en kvantitativ utvärdering av kvaliteten på de analyserade proverna. Därtill testades även karbonatbiprodukter från stålindustrin för att utvärdera möjligheter att använda andra råmaterial. Det transienta förloppet har analyserats, varvid upplösningshastigheten modellerades bl.a. i avseende på tid och pH. Under arbetets gång har antalet empiriska korrelationer minskats till fördel för fysikaliska modeller av diffusiva och konvektiva masstransportfenomen. En målsättning var att skapa en effektiv och snabb metod för att testa olika absorbenter för rökgasavsvavling under transienta förlopp. I arbetet användes PSD-analys, gjordes pH-mätningar och andra utvärderingar av de fysikaliska parametrar som ingår i beräkningarna. On-line mätningar för de icke-stationära variablerna tid och pH ger möjlighet att eliminera osäkerheter. Vissa modeller kan vara komplicerade. En modell för upplösningshastigheten med mer detaljerad utvärdering av parametrar och färre approximationer är därför nödvändig då man vill utvärdera reaktionshastigheten för fasta partiklar i sur miljö. Arbetet utfördes under fyra år och fem peer review-artiklar ingår i avhandlingen.
2010-12-21T11:47:46Z