<p>  </p> <p>Due to the difficulty in physically observing the phenomena inside the actual ladle furnace in the industry, to ascertain optimized methodology for high-grade steel production, an investigation was carried out using numerical modeling to simulate the behavior of alloying elements within the liquid steel bulk using ANSYS Fluent 2020 R1 (ANSYS Inc., Pittsburgh, PA, USA). The model solves the governing equations utilized in computing the trajectories of each particle in the discrete phase. Furthermore, a user defined (UDF) code maps the mass of each parcel based on the total amount of alloy injected. The code also defines the total time it takes for the shell formed around the added materials to melt or dissolve. The study consists of a two-step procedure: ladle stirring by argon inert gas injection and mixing study by injecting micro-alloying elements to capture the flow field, turbulence, and species transport occurring during the refining process. A generic dual plug ladle metallurgy furnace, dimensions, and data obtained from Nucor Steel is used to validate the CFD simulation results. Concise parametric studies consist of ladle geometry design adjustments, variations of argon gas flow rates, and different alloying elements. Though the efficiency of the LMF process is quantified using the mixing time, which decreases as initial gas flow rates increase, results from this study show that extremely high charging of ladles is optional in obtaining shorter mixing. Also, particles behave substantially differently when their densities are below or above that of steel, and their melting points and specific heat capacities influence the time it takes for them to melt or dissolve. The overall potential outcome for this study is to improve the mixing practices due to different optimal procedures required by some materials than others.</p>

Without a doubt, there is a consensus around the international community which suggests that our current way of life is unsustainable for a healthy planet, society and economy. One focal point that should be taken deeply into consideration is the steel industry as, globally, it accounts for 8% of global emissions. Thus, there is a dire need to incorporate drastic measures, if one wishes to reach net-zero emissions by 2050, in accordance with the Paris Agreement of 2015. Electric Arc Furnaces are seeing a rapid implementation in the steel industry. However, at 0.5 tonnes of CO2 emitted per tonne of liquid steel produced, this emissions rating is still significant considering the amount of steel being produced annually. Additionally, these furnaces emit off-gases which must be treated from the dust. This leaves operators with a conundrum as the dust content compromises the use of waste heat recovery boilers for energy recovery, due to constant breakdowns. Therefore, this study aims to analyse the feasibility of using bioenergy and carbon capture and utilisation (CCU) concepts to capitalise on the high off-gas energy and emissions content to remedy the dust issue, whilst producing higher value products. The proposed concept evaluates the effectiveness of using the off-gas as the energy carrier and feed-stock for a biogasificaiton unit. Three different cases based on different EAF off-gas compositions have been investigated. Case 1 suggested that the off-gas composition is very CO2-heavy, whichled to investigating the option of adopting a CO2 biogasification concept to directly use the CO2. Case 1 performed the best in terms of CO2 utilisation efficiency; being 0.293. The system energy utilisation also noted that 49.3% of the inlet streams energy was transferred to the desired product. On a broader picture, this means that around 11% of the total energy coming out of the EAF would be utilised in producing a value-added product in the form of syngas. This contrasts with allowing around 33% of the energy in the EAF either being completely dissipated to the environment or converting it into electricity via waste heat recovery. The following two cases, Case 2 and 3, indicate EAF off-gas composition containing 72% and 40% nitrogen respectively. For Cases 2 and 3, a steam biogasification process was integrated which did not yield positive results for CO2 utilisation, since is a more promising gasifying agent. In addition, significant energy from EAF off-gas is used in raising the temperature of steam to the design temperature of the gasifier. However, although the CO2 was not directly used in this part of the process, it allows for other opportunities of process integration, for example the reverse water-gas shift step.

The energy demands in the world is rapidly increasing and with this,  a supply nuclear  power  is  of  much  interest.    Nuclear  fuel  is  relatively  efficient  when comparing to power sources like wind­ and hydropower plants. Pellets are used as fuel by many plants however, its main concern is to find maximize cost efficiency and  minimize  fuel­waste.   Studying  how  to  get  the  pellets  to  be  as  optimal  as possible is of massive importance and in huge focus in order to match the worlds power demand. These  pellets  are  sintered  in  a  furnace  type  known  as  ”pusher­type”  furnaces that functions continuously and is incredibly efficient when it comes to its heat transfer capacity and high­performance output.  In this sintering process, a gas­ flow from the opposite side from the pellets interacts with the solid pellets in order to get the desired reaction. However, the turbulence and the nature of the multi­ phase flow problem causes many unknown interactions and the main focus is do create a theoretical model based on the process parameters to understand what is happening in the furnace. In this study, a simplified model of the inside of the furnace chamber was created in order to observe where and when in the furnace a dissociation from CO2 to CO + O2 would occur. Data given by Westinghouse was put into a mathematical model created in MATLAB and parameters given by the thermodynamic model was in turn put in to ANSYS, a program based on Computational Fluid Dynamics for a simulation. The simulation was considered a success when the gas­mix goes from 3% CO2 to 0.4%. The CFD of the model estimates this to happen at 250 seconds, where as the thermodynamic model predicts the exchange time to be about 200 seconds.   This study is a major first step in understanding the dynamics of the furnace. / Energibehovet i världen ökar snabbt och då blir ett stadigt tillförsel av kärnenergi mycket intressant.  Kärnbränsle är relativt effektivt jämfört med kraftkällor som vind­  och  vattenkraftverk.    Pellets  används  som  bränsle  av många  kraftverk och då blir det ett upphov att hitta maximal kostnadseffektivitet och minimera bränsleavfall.  Att forska fram till hur man gör pellets så optimala som möjligt är av enorm betydelse och i stort fokus för att matcha världens energi behov. Dessa pellets sintras i en ugnstyp som kallas ”pusher­type” ugnar som fungerar kontinuerligt och är otroligt effektiva när det gäller dess värmeöverförings-kapacitet och högpresterande effekt.  I denna sintringsprocess startar ett gasflöde från motsatt sida från pelletsen med de fasta pelletsen för att få den önskade reaktionen.  Det blir ett flerfasigt flödesproblem och orsakar många okända interaktioner och huvudfokus är att skapa en teoretisk modell baserad på processparametrarna för att förstå vad som händer i ugnen. I  denna  studie  gjordes  en  förenklad  modell  av  ugnskammarens  insida för  att observera var och när i ugnen en dissociation från CO2 till CO + O2 skulle inträffa. Data från Westinghouse placerades i en matematisk modell skapad i MATLAB och  parametrar  som  gavs  av  den  termodynamiska modellen  lades  i  sin  tur  till ANSYS, ett program baserat på Computational Fluid Dynamics för en simulering. Simuleringen ansågs vara färdig när gasblandningen går från 3% CO2 till 0,4%. CFD:n  för  modellen  uppskattar att  detta  händer  vid  250  sekunder,  där  den termodynamiska modellen förutspår utbytestiden till cirka 200 sekunder. Denna studie är ett stort första steg för att förstå ugnens dynamik.

<p>The electric arc furnace (EAF) is a highly energy intensive process used to convert scrap metal into molten steel. The aim of this research is to develop a dynamic model of an industrial EAF process, and investigate its application for optimal EAF operation. This work has three main contributions; the first contribution is developing a model largely based on MacRosty and Swartz (2005) to meet the operation of a new industrial partner (ArcelorMittal Contrecoeur Ouest, Quebec, Canada). The second contribution is carrying out sensitivity analyses to investigate the effect of the scrap components on the EAF process. Finally, the third contribution includes the development of a constrained multi-rate extended Kalman filter (EKF) to infer the states of the system from the measurements provided by the plant.</p> <p>A multi-zone model is developed and discussed in detail. Heat and mass transfer relationships are considered. Chemical equilibrium is assumed in two of the zones and calculated through the minimization of the Gibbs free energy. The most sensitive parameters are identified and estimated using plant measurements. The model is then validated against plant data and has shown a reasonable level of accuracy.</p> <p>Local differential sensitivity analysis is performed to investigate the effect of scrap components on the EAF operation. Iron was found to have the greatest effect amongst the components present. Then, the optimal operation of the furnace is determined through economic optimization. In this case, the trade-off between electrical and chemical energy is determined in order to maximize the profit. Different scenarios are considered that include price variation in electricity, methane and oxygen.</p> <p>A constrained multi-rate EKF is implemented in order to estimate the states of the system using plant measurements. The EKF showed high performance in tracking the true states of the process, even in the presence of a parametric plant-model mismatch.</p> / Master of Applied Science (MASc)

yes / The present paper reports the testing of 12 alkali-activated mortars and a control ordinary portland cement (OPC) mortar. The main aim is to develop cementless binder activated by sodium silicate powder. An alkali quality coefficient combining the amounts of main compositions of source materials and sodium oxide (Na2O) in sodium silicate is proposed to assess the properties of alkali activated mortars, based on the hydration mechanism of alkali-activated pastes. Fly ash (FA) and ground granulated blast-furnace slag (GGBS) were employed as source materials. The ratio of Na2O-to-source material by weight for different mortars ranged between 0.038 and 0.164; as a result, alkali quality coefficient was varied from 0.0025 to 0.0365. Flow loss of fresh mortar, and shrinkage strain, compressive strength and modulus of rupture of hardened mortars were measured. The compressive strength development of alkali activated mortar was also compared with the design equations for OPC concrete specified in ACI 209 and EC 2. Test results clearly showed that the flow loss and compressive strength development of alkali-activated mortar were significantly dependent on the proposed alkali quality coefficient. In particular, a higher rate of compressive strength development achieved at early age for GGBS-based alkali-activated mortar and at long-term age for FA-based alkali-activated mortar. In addition, shrinkage strain and modulus of rupture of alkali-activated mortar were comparable to those of OPC mortar.

In view of the challenges of decarbonisation of the cement industry, the use of low-clinker ternary cements especially with calcined clays is becoming increasingly important. The combination of Portland cement clinker (K), ground granulated blast furnace slag (S) and calcined clay (Q) in ternary cements is very promising in terms of cement and concrete properties. In this study the CO2 footprint of such cements as well as the energy required for their production was determined over a wide range of cement compositions systematically for the first time. The results were related to the strength development of the cements and the mineralogical com-position as well as the moisture of the used clays. Compared to an OPC (CEM I 42.5), both the CO2 and energy saving potentials for the production of ternary KSQ cements are between 25 and 55 % respectively, depending on the cement composition.

Магистерская диссертация посвящена разработке программного обеспечения интеллектуальной системы анализа температуры холодильников системы охлаждения доменной печи. В ходе работы рассмотрены основные этапы реализации программного модуля: анализ предметной области, функциональное моделирование, проектирование и программная реализация web-приложения. Разработанная система предоставляет пользователю возможность отображения данных о температуре в графическом и табличном виде, а также проведение анализа и прогнозирования температуры тела холодильника в доменной печи. Она позволяет оперативно мониторить и контролировать температурные показатели, что является важным фактором для обеспечения эффективности и надежности работы печи. Научная новизна полученных в работе результатов заключается в разработке методов эффективной организации, ведения процесса разработки и сопровождения специализированного информационного, алгоритмического и программного обеспечения, включая базу данных доменного цеха и пользовательское приложение системы интеллектуального анализа температуры холодильников системы охлаждения доменной печи: использование гибкой методологии разработки (Agile, SCRUM) и таск-трекера Microsoft Azure DevOps для ведения проекта, взаимодействия с заказчиком во время разработки, отслеживания ошибок, визуального отображения задач и мониторинга процесса их выполнения; функциональное моделирование процессов и подсистем для реализации web-приложения подготовки технического отчета доменного цеха на основе методологии IDEF0 и средства реализации Ramus Educational; использование методики коллективного владения программным кодом на основе сервиса (удаленного репозитория) GitHub; применение методов машинного обучения для реализации алгоритма прогнозирования температуры холодильников системы охлаждения доменной печи. Практическая значимость результатов заключается в том, что разработанное программное обеспечение позволит: программное обеспечение позволит сэкономить время на получение, хранение, обработку данных, что положительно скажется на эффективности работы доменного производства, поможет снизить риск возникновения аварийных ситуаций и неплановых остановок доменных печей; специалистам отдела сопровождения информационных систем снизить трудозатраты на сопровождение, совершенствование и развитие системы с учетом пожеланий пользователей. Результаты работы могут быть использованы также в учебном процессе для обучения бакалавров и магистрантов по направлению «Информационные системы и технологии». Результаты работы представлены и обсуждены на международных и всероссийских конференциях: X, XI Всероссийских научно-практических конференциях студентов, аспирантов и молодых учёных «Теплотехника и информатика в образовании, науке и производстве» (ТИМ’2022, ТИМ’2023) с международным участием (г. Екатеринбург, УрФУ, 2022, 2023); Всероссийской научно-практической конференции (с международным участием) «Системы автоматизации (в образовании, науке и производстве)» AS’2022 (г. Новокузнецк, СибГИУ, 2022); международной научно-технической конференции «Состояние и перспективы развития электро и теплотехнологии» XXII Бенардосовские чтения (г. Иваново, ИГЭУ, 2023). / The master's thesis is devoted to the development of software for an intelligent system for analyzing the temperature of refrigerators in the blast furnace cooling system. In the course of the work, the main stages of the implementation of the software module were considered: domain analysis, functional modeling, design and software implementation of a web application. The developed system provides the user with the ability to display temperature data in graphical and tabular form, as well as to analyze and predict the body temperature of the refrigerator in the blast furnace. It allows you to quickly monitor and control temperature indicators, which is an important factor for ensuring the efficiency and reliability of the furnace. The scientific novelty of the results obtained in the work lies in the development of methods for the effective organization, management of the development process and maintenance of specialized information, algorithmic and software, including the database of the blast furnace shop and the user application of the system for intelligent temperature analysis of the refrigerators of the blast furnace cooling system: − use of flexible development methodology (Agile, SCRUM) and the Microsoft Azure DevOps task tracker for project management, interaction with the customer during development, tracking errors, visual display of tasks and monitoring the progress of their implementation; − functional modeling of processes and subsystems for the implementation of a web application for preparing a technical report for a blast furnace shop based on the IDEF0 methodology and the Ramus Educational implementation tool; − use of the methodology of collective ownership of program code based on the service (remote repository) GitHub; − application of machine learning methods to implement an algorithm for predicting the temperature of refrigerators in the blast furnace cooling system. The practical significance of the results lies in the fact that the developed software will allow: − the software will save time for receiving, storing, processing data, which will have a positive impact on the efficiency of blast-furnace production, help reduce the risk of emergencies and unscheduled shutdowns of blast furnaces; - specialists of the information systems maintenance department to reduce labor costs for maintenance, improvement and development of the system, taking into account the wishes of users. The results of the work can also be used in the educational process for training bachelors and masters in the direction of "Information Systems and Technologies". The results of the work are presented and discussed at international and all-Russian conferences: X, XI All-Russian scientific and practical conferences of students, graduate students and young scientists "Heat engineering and informatics in education, science and production" (TIM'2022, TIM'2023) with international participation (Ekaterinburg, UrFU, 2022, 2023); All-Russian scientific and practical conference (with international participation) "Automation systems (in education, science and production)" AS'2022 (Novokuznetsk, SibGIU, 2022); International Scientific and Technical Conference "Status and Prospects for the Development of Electrical and Thermal Technologies" XXII Benardos Readings (Ivanovo, ISPU, 2023).

Thesis (MScEng) --University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This thesis deals with the development of a new process for the production of Direct Reduced Iron (DRI), intended for use specifically by small scale Electric Arc Furnace (EAF) based steel mills, who require small volumes of DRI. The term development as used here is taken to include such aspects as conceptual design, theoretical verification and initial practical testing. The rise of EAF steelmaking brought about the metamorphosis of steel scrap from a waste product into a valuable raw material. Scrap prices rose steeply during the period 1995 to 2009 compelling EAF steelmakers, wishing to have more control over the cost of their input material, to seek for scrap supplements or alternatives. DRI has become an accepted and sought after supplement, or even complete alternative, to steel scrap. Adding DRI to an EAF charge has a range of advantages, including the dilution of tramp elements and possible cost benefits, but it does have negative effects. These include the lowering of the scrap to liquid metal yield and an increase in power consumed. The effect of charging DRI to a small EAF is quantified. The maximum DRI that may be added to the burden whilst still maintaining the present steelmaking volume, is shown to be as high as 50% if charged continuously, and the maximum price payable for DRI, is shown to be approximately 80% of base grade scrap price. Finally other requirements unique to small scale EAF operators are considered in order to prepare a schedule of requirements for a DRI plant specifically for small scale EAF steel mills. A review of published information on existing DRI production technology, processes and plants is undertaken is establish the fit of existing processes to the requirements set. Initially the thermodynamics and kinetics of iron ore reduction and coal gasification, specifically downdraft gasification are reviewed. Thereafter existing processes are reviewed. Shaft based processes and rotary kiln based processes are identified as possible suitors to the requirements. Limitations of these processes, specifically heat transfer in rotary kilns and the pressure drop over a reduction shafts are investigated. Finally a typical process in each of the main process classes is adjudicated against the set requirements. None is found to match the set requirements. A new process is proposed that is claimed to better suit to small scale operation. The uniqueness of the process is embodied in the combination of existing technologies of downdraft gasification and iron ore reduction in a shaft, in a single reactor. The process consists of two shafts, one placed above the other. Iron ore is charged into the top shaft, called the pre-heat shaft, where it is pre-heated and lightly reduced to wustite with gas from the bottom shaft, called the reduction shaft. The pre-heated ore is then charged together with coal into the reduction shaft. Gasification air is drawn into the top of the reduction shaft where the coal is gasified in a downdraft gasifier, generating reduction gas which reduces the ore as the gas moves concurrently with the iron ore. The exit gas is cleaned and pumped to the pre-heat shaft where it combusted with air to pre-heat the iron ore in the pre-heat shaft. The concept is analysed thermodynamically using amongst others, FactSage, and is shown to be thermodynamically viable. To test the concept process concept practically, an extremely small pilot plant with a production rate of 2kg DRI/h, consisting of only a gasifier/reduction shaft, was designed and constructed using reduction rate data obtained from literature supplemented with data obtained from thermogravimetric analysis of CO reduction of lump Sishen hematite. Pilot Plant trials were performed using various reductant sources. The degree of metallizaion was analysed using visual inspection of cut and polished samples compared to calibrated standards. Analysis of the results indicate that coal rate and production rate influence the degree of reduction positively and negatively. The conclusions arrived at include the fact that the process is thermodynamically viable, that it was possible to reduce iron ore in a simplified pilot plant, and that the process was found to be stable and controllable. It is recommended that a larger scale pilot plant, embodying the full proposed flow sheet be erected to test the process more completely. / AFRIKAANSE OPSOMMING: Die tesis handel oor die the ontwikkeling van ‘n nuwe proses vir die vervaardiging van sponsyster. Die proses is beoog spesifiek vir gebruik deur kleinskaalse Elektriese Boogoond (EBO) gebaseerde staal aanlegte, wat kleiner hoeveelhede sponsyster benodig. Die term ontwikkeling soos hier gebruik word aanvaar om aspekte soos konseptuele ontwerp, teoretiese verifikasie en aanvanklike toetsing te behels. Die vinnige groei van EBO staalvervaardiging het skroot getransformeer van weggooiproduk tot waardevolle grondstof. Die prys van skroot het skerp gestyg gedurende die periode 1995 to 2009. EBO gebaseerde staal produsente, in ‘n poging om meer beheer te hê oor die koste van hul insetmateriaal, het hul in ‘n toenemende mate tot skrootalternatiewe gewend. Sponsyster het ‘n aanvaarde en gewaardeerde byvoeging, en selfs alternatief tot staalskroot geword. Die byvoeging van sponsyster by die lading van ‘n tipiese EBO het besliste voordele, maar het dit ook nadelige effekte. Die voordele sluit die verdunning van reselemente en moontlike kostevoordele in, terwyl van die nadele die verlaging van die skroot tot vloeistaal opbrengs, en ‘n verhoging in kragverbruik, is. Die effek van die byvoeging van sponsyster tot ‘n EBO lading word gekwantifiseer. Daar word getoon dat die maksimum hoeveelheid sponsyster wat by ‘n EBO lading gevoeg kan word terwyl die hoeveelheid staal geproduseer konstant gehou word, ongeveer 50% is indien die sponsyster kontinue gelaai word, en die maksimum prys wat vir die sponsyster betaal kan word, word bereken op ongeveer 80% van die prys van basisgraad skroot. Ander vereistes uniek aan kleinskaal EBO bedrywers word oorweeg ten einde ‘n lys van vereistes vir ‘n sponsysteraanleg, uniek aan kleinskaal EBO bedrywers, te kan bepaal. ‘n Oorsig van gepubliseerde inligting oor sponsysterproduksietegnologie word onderneem ten einde die passing van bestaande prosesse met die gestelde vereistes te kan bepaal. Nadat die termodinamika en kinetika van ysterertsreduksie en steenkoolvergassing be-oordeel is, word bestaande sponsysterprosesse beskou. Skag- en Roterende oond gebaseerde prosesse word as moontlik gepaste prosesse identifiseer. Hitte-oordrag en die drukval oor gepakte beddens, synde tipiese beperkings eie aan die twee prosesse, woord beskou. Tipiese prosesse in elk van die hoofklasse van prosesse word ten laaste be-oordeel aan die gestelde kriteria. Daar word bevind dat geeneen van die bestaande prosesse aan die vereistes voldoen nie. ‘n Nuwe proses, wat skynbaar die behoefte van kleinskaalse EBO gebaseerde staalprodusente beter bevredig, word voorgestel. Bestaande tegnolgie word in ‘n unieke opstelling geïntegreer. Reduksie word in ‘n reduksiekag gedoen as gevolg van die ooglopende massa- en hitte-oordragvoordele van ‘n skag. Reduksiegas word verkry van steenkoolvergassing in ‘n afstroomvergasser ten einde teerverwydering in ‘n naverwerkingsstap oorbodig te maak. Die uniekheid van die proses is beliggaam in die kombinasie van ‘n steenkoolvergasser en reduksieskag in ‘n enkele reaktor. Die proses bestaan uit twee skagte, een bo die ander. Ystererts word in die boonste skag, wat die voorverhitskag genoem word, gelaai. Hier word die erts voorverhit en moontlik lig gereduseer tot wustiet met gas van die onderste skag, wat die reduksieskag genoem word. Die voorverhitte erts word saam met steenkool in die reduksieskag gelaai. Vergassingslug, word in die reduksieskag gesuig waar die steenkool in ‘n afstroomvergasser vergas word. Hierdeur word reduksiegas gegenereer wat die erts verder reduseer soos dit saamstromend met die erts af beweeg. Die uitlaatgas word gesuiwer en na die voorverhitskag gepomp waar dit verbrand word om die erts te voorverhit. Die konsep is termodinamies analiseer met gebruikmaking van onder andere FactSage, en werkbaar bevind. ‘n Baie klein, vereenvoudigde proefaanleg, met ‘n produksievermoë van 2kg DRY/uur, bestaande uit slegs ‘n reduksiekag, is ontwerp en gebou met gebruikmaking van kinetika inligting uit die literatuur aangevul met inligting uit termogravimetriese analise van die CO reduksie van Sishen hematiet. Proefaanleglopies is uitgevoer met ‘n reeks reduktantbronne. Die metallisasiegraad is bepaal deur visuele inspeksie van gesnyde, gepoleerde monsters wat vergelyk is met gekalibreerde standaarde. Analise van die resultate toon dat die steenkoolkoers ‘n positiewe verband, en die produksiekoers ‘n negatiewe verband met die metallisasiegraad het. Die slotsom waartoe gekom is, is dat die proses termodinamies werkbaar is, dat reduksie van ystererts in ‘n vereenvoudigde proefaanleg bewerk kon word, en dat die prose stabiel en beheerbaar voorgekom het. Die aanbeveling word gemaak dat ‘n groter proefaanleg wat die volledige voorgestelde vloeiskema verteenwoordig, opgerig behoort te word, ten einde die proses meer volledig te kan toets.

<p>Highly polluted urban storm water from e.g. highways can contain large amounts of heavy metals that may cause harm if they are discharged into recipients. To remove the heavy metals a possible low-cost method that does not require much maintenance, could be the use of reactive filters with filter materials consisting of industrial residues or other cheap mineral based materials. Dissolved metal ions are removed by reactive filters through the processes of ions binding to active sites on the surface of the filter materials, or by formation of insoluble precipitates.</p><p>The ability of CaO-treated granulated blast-furnace slag, iron oxide coated sand, olivine and nepheline to remove seven heavy metals (Cr, Cd, Cu, Ni, Zn, Pb and Hg) from urban storm water was studied. Initially batch experiments were performed where the effect of pH, dissolved organic carbon (DOC) and dissolved ions on the adsorption efficiency was studied. The experiments were conducted with urban storm water and with a reference solution (10 mM NaNO3), both containing the same concentration of heavy metals (approx. 1 μM). The two materials with the best results were further investigated in a column study, where the capacity of the filter was tested. Chemical equilibrium calculations using the program Visual MINTEQ were performed in order to assess the role of precipitation as a mechanism for removal.</p><p>The results show that the blast-furnace slag was the most effective filter material and that it has great potential to be used as a heavy metal remover. Also the iron oxide coated sand worked satisfactory. The highest degree of removal was obtained for lead, cadmium and nickel, for which the removal efficiency exceeded 90% after a load of 300 times the water volume in the columns. For some metals, mainly copper, chromium and mercury the dissolved organic matter affected the removal negatively. The chemical mechanisms causing the removal are specific adsorption to the surfaces of the materials, and for the blast-furnace slag probably precipitation of insoluble metal sulfides.</p> / <p>Starkt förorenat dagvatten som rinner av från exempelvis motorvägar, kan innehålla betydliga mängder tungmetaller som kan orsaka skada om de kommer ut i omgivande vattendrag. En billig metod för tungmetallavskiljning, som inte kräver så mycket underhåll, skulle kunna vara att använda reaktiva filtermaterial bestående av restprodukter eller andra mineraliska lågkostnadsmaterial. Reaktiva filter fungerar som metallavskiljare genom att de lösta metalljonerna binder till ytgrupper på filtermaterialen eller att svårlösliga utfällningar bildas.</p><p>Förmågan att avskilja sju tungmetaller (Cr, Cd, Cu, Ni, Zn, Pb och Hg) ur dagvatten har undersökts för fyra mineraliska filtermaterial, kalciumoxiddopad masugnsslagg, järnoxidsand, olivin och nefelin. Studien inleddes med skakförsök där adsorptionens pH-beroende undersöktes. Försöken gjordes dels med dagvatten, dels med en referenslösning (10 mM NaNO3) med samma tungmetallkoncentration (ca 1μM). Detta gjordes för att studera effekter av löst organiskt material och andra ligander på adsorptionen. Därefter testades de material som uppvisat bäst resultat i skakförsöket i kolonnförsök, ett försök som mer efterliknar en praktisk tillämpning och där filtrets kapacitet kan studeras. Genom kemiska jämviktsberäkningar med programmet Visual MINTEQ var det möjligt att undersöka om bildningen av svårlösliga metallutfällningar bidrog till metallavskiljningen.</p><p>Resultaten visar att slaggen var det effektivaste filtermaterialet och att detta har stor potential att användas för avskiljning av tungmetaller. Även järnoxidsanden fungerade tillfredsställande. De metaller som avskiljdes bäst var bly, kadmium och nickel, för vilka avskiljningen var > 90 % i kolonnförsöket efter en belastning motsvarande 300 gånger vattenmängden i kolonnerna. För vissa metaller, främst koppar, krom och kvicksilver, försämrades avskiljningen betydligt när löst organiskt material fanns närvarande. Mekanismerna som står för avskiljningen är till störst del adsorption till grupper på filtermaterialens ytor, men bildning av svårlösliga metallsulfider är också tänkbar för slaggen.</p>

This master thesis presents the effects of fly ash on the properties of alkali activated slag concrete, commonly referred as Geopolymer concrete (GPC). Cement manufacturer are major producers of CO2 which negatively affects the environment. Due to the increased construction activities and environmental concern, it is necessary to introduce alternative and eco-friendly binders for concrete. Slag and fly ash based concrete, which is by-product from industrial waste, is probably the best replacement for OPC concrete due to less or nil environmental issue. Most of the researchers have already concluded that slag and fly ash can be used as binders in concrete by activating them with alkali activator solution (e.g. by sodium silicate or sodium carbonate). In the present work concretes were produced by varying the proportion of slag to fly ash (40:60, 50:50, 60:40 &amp; 80:20); amount of alkali activators (5, 10 &amp; 14) and chemical modulus of sodium silicate (Ms) (0.25, 0.5 &amp; 1).  Setting times and compressive strength values were evaluated. Results showed that decrease in fly ash content irrespective of % of alkali activators and alkali modulus (Ms), the compressive strength was increasing and setting time was getting shorter. The produced concretes showed increasing compressive strength with increase in % of alkali activator for Ms 0.5 and 1, while for Ms=0.25 the strength was decreasing with increase in % of alkali activators. From this it can be concluded that, Ms=0.5 was the optimum point below which the reaction got slower. Based on the initial investigations, mix S8:F2-SS10(1) and S8:F2-SS10(0.5) showed most promising results in terms of fresh and hardened concrete properties and were easy to handle. Consequently, the above mentioned mixture was chosen to be studied in more detail. The experimental program for these mixes included determination of slump flow, compressive strength (7, 14, 28 days) and shrinkage (drying and autogenous). The results shows that, strength increased with time and comparatively mix with Ms=0.5 showed higher compressive strength than mix with Ms=1, due to higher alkalinity of the pore solution. Mix with Ms=1 showed higher drying shrinkage compared to mix with Ms=0.5, which was explained by higher alkalinity of the solutions (Ms=0.5) leading to rapid formation of aluminosilicate gel. Autogenous shrinkage appeared to be higher for mix with Ms=0.5. This was associated with lower modulus which leads to densification of concrete microstructure at early ages. Pore diameter decrease and the water trapped in the pores exerted increasing tensile stress resulting for higher autogenous shrinkage.