A flotation column has been developed Incorporating the use of fine air bubbles (less than 100 microns) to remove ash-forming minerals from micronized coal. The microbubble generator used In this work has been characterized and found to yield a very narrow size distribution. Microbubble column flotation tests have been conducted to study a series of operating variables such as time, bubble size, feed rate, feed point, feed percent solids, column height, bubble number concentration, make-up water addition and countercurrent wash water addition. The results show that i) fine air bubbles are Inherently better suited for floating small particles; ii) both ash and recovery rates Increase with Increasing feed rate, distance of the feed point from the tailings port, feed percent solids and bubble number concentration; iii) taller columns result In Improved recovery and ash rejection; and iv) the countercurrent wash water addition minimizes the entrainment of mineral matter to the froth product. Proper control of these parameters makes It possible to produce super clean coal (< 2% ash). / M.S.

In recent years, a great deal of interest has been shown in developing methods for preparing super—clean coal containing less than 2% ash and 0.5% sulfur. New techniques for recovering fine coal, such as micro—bubble flotation, can achieve the desired result provided mineral matter is sufficiently liberated. To achieve sufficient liberation, however, it is often necessary to grind to a mean particle size finer than 10 microns. Since conventional ball mills are highly inefficient in this fine size range, the stirred ball mill has been proposed as a more suitable means for ultrafine grinding. / Master of Science

In order to demonstrate the ability of microbubble flotation to superclean coal to ash levels of less than 2%, several Eastern U. S. coals have been tested. The results show that the process is capable of producing superclean coal with improved recovery as compared to the conventional flotation process.To further improve and understand the microbubble flotation process, electrokinetic studies of the hydrocarbon oils used in flotation as collectors have been conducted. Also, the effect of oil emulsifiers on the zeta potential of oil droplets has been studied. In general, oil droplets are negatively charged and negative zeta potential is reduced with the addition of nonionic and cationic surfactants. On the other hand, the negative charge is increased with the addition of an anionic reagent. It has also been shown that the negative zeta potential of oil droplets increases with increasing hydrocarbon chain length.The effects of different collectors on induction time and flotation have been determined by conducting microflotation and induction time experiments using an Elkhorn seam coal sample. The results show that industrial oils combined with the coal have the shortest induction times and, therefore, the highest flotation yields as compared to pure hydrocarbon oils. It has also been shown that oil emulsifiers tend to increase flotation yield and reduce particle/bubble induction time. / Master of Science

The Chemical and Electrochemical Coal Cleaning (CECC) process, designed to remove mineral matter from coal, has been investigated by treating coal samples in acidified slurries. Various coals, characterized by different maceral structures and mineral matter contents, were subjected to several experimental procedures under mild conditions. Substantial amounts of mineral matter (up to 70%) could be extracted from coals which were resistant to physical cleaning, while 22% of sulfur could be removed from pyritic coals. The operating conditions of the CECC were studied in order to determine their influence on the process efficiency. Analyses conducted on solids and leachates resulting from the tests demonstrated that different mechanisms were achieving demineralization by the CECC. Between 50% and 95% of the feed mineral matter was removed by dissolution, whereas the balance could be ascribed to liberation. The CECC process is suitable for cleaning middlings, as well as for further extracting mineral matter from physically clean coals, especially from pyritic vitrinite and fusinite type coals. / Master of Science

A new method for demineralizing coal has been developed which is based on the osmotic pressures that occur when electrical double layers overlap. In this technique, coal is exposed to ferric ions in an acidic medium which causes the coal to lose electrons and become positively charged, thereby establishing ionic double layers in the vicinity of its surface. Inside the pores and crevices in which mineral matter is entrapped, the ionic double layers overlap and reduce the chemical potential of water, creating an osmotic pressure. The build-up of such pressure pushes the mineral matter out of the crevices, resulting in mineral liberation. Since the process, which is termed electro catalytically induced liberation (EIL), relies on surface-chemical reactions, the energy consumption is substantially lower than in conventional liberation processes based on comminution. Tests on several different seams of coal from varying geological locations have indicated that the process may be used to remove over 70% of the mineral matter present in coal. Mass balance studies conducted on a Wyodak coal indicate that approximately 90% of the ash removed is by the EIL mechanism, while the balance may be attributed to acid dissolution and the loss of material during handling. Scanning electron micrographs of the coal samples taken before and after treatment show morphological changes consistent with the proposed EIL mechanism. The technique has been used successfully to clean bituminous coals, low-rank coals and preparation plant refuse, and to further reduce the ash content of coals pre-cleaned by other means. A theoretical model has been developed to calculate the osmotic pressure that occurs inside a typical coal crevice during the EIL treatment. The changes in the aqueous chemical potential are calculated using semi-empirical equations derived from solution theory, while partial molar volume changes are accounted for in the final calculation of the osmotic pressure. The model indicates that pressures on the order of 4-7 atmospheres can develop inside crevices with walls 100-1000Å apart. These values are numerically consistent with those predicted by other models developed using different approaches. / Ph. D.

This study analyzes a commercial by Gillette (2019) and a commercial by Pepsi (2017), which are based on the movements Me Too and Black Lives Matter. The purpose of the study is to examine the commercials with a multimodal critical discourse analysis (MCDA) and with the help of associated semiotic resources analyze communicative and visual performances that appear in the commercials. Through MCDA, the study aims to find underlying messages, portrayals and representations that may indicate to a performative brand activism or Woke Washing in each commercial. The study is based on theories about representation, brand activism, Woke Washing and gender studies. The results of the study indicate that Gillette's commercial has two themes that stand out. The first theme concerns masculinity and ethnicity. The result is that they almost exclusively portray white men in their commercial. The second theme concerns masculinity and women at a disadvantage, and the result is that they try to include themselves in the Me Too debate, which mainly concerns the female gender, while they are at the same time portraying women who are treated badly by men in the commercial. In their commercial, Gillette tries to sell a lifestyle rather than their own products, and this means that there is no performative brand activism occurring in the commercial. What indicates to Woke Washing in the commercial is that they have not done a consistent job to counteract the macho culture and its effects on the male and female gender.  In Pepsi's commercial, two themes were identified. The first theme concerns representation and ethnicity. The result is that they are more intersectional in the representation of different social groups in the commercial. However, they have made the choice to give Kendall Jenner, who is a white woman, interpretive precedence in a demonstration that has connections to Black Lives Matter and concerns black people. The second theme concerns representation and commercial framing, and the result is that, through their brand colors and soft drinks – Pepsi makes a consistent commercial framing throughout the whole commercial, and this means that a performative brand activism thus occurs. What indicates to Woke Washing in the commercial is the fact that they commercialize on an expression taken from a socio-political aspect. / I den här studien analyseras en reklamfilm av Gillette (2019) och en reklamfilm av Pepsi (2017), som tar avstamp i rörelserna Me Too och Black Lives Matter. Syftet med studien är att granska reklamfilmerna ur en multimodal kritisk diskursanalys (MCDA) och med hjälp av tillhörande semiotiska resurser analysera kommunikativa och visuella utföranden som ter sig i reklamfilmerna. Genom MCDA, ämnar studien att finna underliggande budskap, skildringar och representationer som kan indikera till en performativ varumärkesaktivism eller Woke Washing i respektive reklamfilm. Studien utgår från teorier kring representation, varumärkesaktivism, Woke Washing, genus och maskulinitet. Studiens resultat pekar på att Gillette’s reklamfilm har två teman som sticker ut i mängden. Första temat berör maskulinitet och etnicitet, där resultatet är att de nästan uteslutande skildrar vita män i sin reklamfilm. Andra temat berör maskulinitet och kvinnor i underläge, där resultatet är att de försöker inkludera sig själva i Me Too debatten som främst berör det kvinnliga könet, samtidigt som de skildrar kvinnor som blir illa behandlade av män i reklamfilmen. Gillette försöker i sin reklamfilm att sälja in en livsstil snarare än deras egna produkter, och det medför till att det inte förkommer en performativ varumärkesaktivism i reklamfilmen. Det som indikerar till Woke Washing i reklamfilmen är att de inte har gjort ett genomgående arbete för att motverka machokulturen och dess effekter på det manliga respektive kvinnliga könet.  I Pepsi’s reklamfilm identifierades två teman. Första temat berör representation och etnicitet, där resultatet är att de är mer intersektionella i representationen av olika samhällsgrupper i reklamfilmen. Däremot har de gjort valet att ge Kendall Jenner, som är en vit kvinna, tolkningsföreträde i en demonstration som har kopplingar till Black Lives Matter och berör svarta personer. Andra temat berör representation och kommersiell inramning, där resultatet är att de, genom deras varumärkesfärger och läskedryck, gör en genomgående kommersiell inramning under hela reklamfilmen, och det medför till att en performativ varumärkesaktivism således förekommer. Det som indikerar till Woke Washing i reklamfilmen är det faktum att de kommersialiserar på ett uttryck taget ur en sociopolitisk aspekt.

Inom medicin och kärnkraft ställs höga krav på olika komponenters renhetsgrad. Vid tillverkning av precisionskomponenter inom medicin och kärnkraftsteknik så används skärvätska för att kyla och smörja godset. Skärvätskan behöver tvättas bort innan komponenterna skickas till kunderna. För att kunna tvätta bort skärvätskan används en speciell tvättutrustning. Idag saknas en metod för att kunna påvisa att den speciella tvättutrustningen på ett tillförlitligt sätt uppnår gällande krav och standarder på renhet som ställs av branscherna, på komponenterna. Genom att verifiera tvättutrustningen mot en specifik kravbild, godkänns tvättutrustningens duglighet och således frisläpps utrustningen för produktion. Målet med studien är att ta fram ett underlag för att kunna verifiera en speciell tvättutrustning. Målet uppnås genom att undersöka vilka faktorer som påverkar renhetsgraden i tvättprocessen och utveckla metoder för att säkerställa att dessa faktorer beaktas. Några av metoderna som används i arbetet är Plan-Do-Study-Act (PDSA), Acceptanskontroll enligt attributsmetoden, intervju och observation. Resultatet av provgruppsmätningarna från laboratoriet, visar att komponenternas renhetsgrad ligger inom Willos kravställning på restkontamination av olja≤10 μg/cm^2 då komponenterna tvättats med tvättprogram två. Efter att provgupperna genomgått acceptanskontrollen står det klart att provgrupperna accepteras med en sannolikhet på 95,6% och att tvättprocessen är stabil. I studien har gamla och antagna mätvärdena använts eftersom det tar lång tid att ta laboratorieprover och tiden som examensarbetet pågår är begränsad. Med de gamla och antagna mätvärdena skulle den speciella tvättutrustningen kunna verifieras mot Willos kravställning, för att möta branschernas krav på renhetsgrad. Genom verifieringen kan man på så vis påvisa att tvättutrustningen levererar stabilt tvättresultat över tid. / In medical and nuclear power applications, high demands are placed on the level of cleanliness of various components. When precision components in medicine and nuclear power technology are manufactured, cutting fluid is used to cool and lubricate the raw stock. The cutting fluid needs to be washed away before the components are sent to customers. To be able to wash away the cutting fluid, special washing equipment is used. Today, there is no method to demonstrate that the special washing equipment reliably meets current requirements and standards for cleanliness set by the industries on the components. By verifying the washing equipment against specific requirements, the capability of the washing equipment is approved, and thus, the equipment is released for production. The study aims to produce a basis for verifying special washing equipment. The goal is achieved by examining which factors affect the level of cleanliness in the washing process and developing methods to ensure that these factors are taken into account. Some of the methods used in work are Plan-Do-Study-Act (PDSA), Acceptance sampling according to the attribute method, interview and observation. The results of the test group measurements from the laboratory show that the level of cleanliness on the components is within Willo's requirements for residual contamination of oil≤10 μg/cm^2 when the components have been washed with washing program two. After the sample groups have undergone the acceptance sampling, it is clear that the sample groups are accepted with a probability of 95.6% and that the washing process is stable. In the study, old and assumed measurement values have been used because of the time it takes to perform laboratory samples, and the time that the degree project progresses is limited. With the old and assumed measurement values, the special washing equipment could be verified to Willo's requirements in order to meet the industries' requirements for the level of cleanliness. Through the verification, it can be demonstrated that the washing equipment delivers stable washing results over time.

Massatvätt är ett viktigt steg i kraft-processen, då kokkemikalierna kan återvinnas och återanvändas i processen, vilket minimerar belastningen på miljön. Det är ett viktigt steg innan blekning av massan, då en låg kemisk syre-förbrukning (COD) är viktigt för att minska förbrukning av blekningskemikalier. Dessutom kan massatvätt även eliminera andra oönskade material, såsom metaller eller extraktivämnen. Syftet med studien var att utvärdera av tvätt-effektivitet av industriell massatvätt. Målen var att jämföra industriell tvättning med extensiv tvättning, att undersöka kvaliteten av tvättvätskor med analystekniker och att undersöka befintliga metoder för att beräkna tvätt-effektivitet. Den experimentella fasen var indelad i provtvättning och tvätt-serier, utförda med olika tvättvätskor, uppehållstider och industriell och extensiv utspädningsfaktor. Provtvättningen gav resultat som möjliggjorde det att utveckla tvätt-metoden. Resultaten för tvätt-serien visade att den extensiva utspädningsfaktorn generellt gav bättre resultat och en mer effektiv tvätt, och att en tvättvätska med en temperatur på 80°C generellt gav bättre resultat. Ljusheten påverkades inte av utspädningsfaktorn och kappanalysen visade en väldigt liten skillnad jämfört med originalmassan. Utvärderingen av befintliga metoder för att beräkna tvätt-effektivitet indikerade att alla undersökta metoder kunde ge felaktiga resultat, men beräkningarna tillsammans med andra metoder såsom COD, konduktivitet och med flera borde ge industrin en god indikation på tvätt-effektiviteten / Pulp washing is an important step in the kraft process, as it allows for the cooking chemicals to be recovered and reused in the process, which also minimizes the environmental load to the subsequent stages. It is also important before the bleaching plant, as a low chemical oxygen demand (COD) carry-over is important to minimize the consumption of bleaching chemicals. Furthermore, washing can also remove other unwanted materials, such as metals or wood extractives. The aim of the study was to assess washing efficiency of industrial washing. The objectives were to compare industrial washing with extensive washing, to investigate the quality of wash liquors using analytical techniques and to examine existing methods for calculating washing efficiency. The experimental phase was divided into trial washing and washing series, conducted with different wash liquors, residence times and dilution factors (DF). The trial washing yielded results that allowed for the washing methodology to be improved. The results from the washing series indicated the extensive DF in general gave better results and provided a more efficient washing, and that a wash liquor of 80°C gave better results. Brightness was not affected by the dilution factor and kappa number analysis showed that there was a very slight difference compared to the original pulp. The evaluation of existing methods for calculating washing efficiency indicated that all investigated methods could give inaccurate results, but that the calculations together with other methods such as COD and conductivity should give the industry a good indication of the washing efficiency.

Mineral matter affect various coal properties as well as the yield and composition of products released during thermal processes. This necessitates investigation of the effect of the inherent minerals on the products derived during pyrolysis, as pyrolysis forms the basis of most coal utilisation processes. A real challenge in this research has been quantifying the changes seen and attributing these effects to specific minerals. Thus far it has been deemed impossible to predict product yields based on the mineral composition of the parent coal. Limited research regarding these aspects has been done on South African coal and the characterisation of pyrolysis products in previous studies was usually limited to one product phase. A novel approach was followed in this study and the challenges stated were effectively addressed. A vitrinite-rich South African coal from the Highveld coal field, was prepared to an undersize of 75 μm and divided into two fractions. HCl/HF acid washing reduced the ash yield from 14.0 wt% d.b. to 2.0 wt% d.b. (proximate analysis). Pyrolysis was carried out with the North-West University (NWU) Fischer Assay setup at 520, 750 and 900°C under N2 atmosphere and atmospheric pressure. The effect of acid washing and the addition of minerals on the derived pyrolysis products were evaluated. Acid washing led to lower water and tar yields, whilst the gas yields increased, and the char yields were unaffected. The higher gas yield can be related to increased porosity after mineral removal as revealed by Brunauer-Emmett-Teller (BET) CO2 adsorption surface area analysis of the derived chars. Gas chromatography (GC) analyses of the derived pyrolysis gases indicated that the acid washed coal fraction (AW TWD) derived gas contained higher yields of H2, CH4, CO2, C2H4, C2H6, C3H4, C3H6 and C4s when compared to the gas derived from the raw coal fraction (TWD). The CO yield from the TWD coal was higher at all final pyrolysis temperatures. Differences in gas yields were related to increased tar cracking as well as lower hydrogen transfer and de-hydrogenation of the acid washed chars. Analyses of the tar fraction by means of simulated distillation (Simdis), gas chromatography mass spectrometry (GC-MS) –flame ionization detection (–FID) and size exclusion chromatography with ultraviolet (SEC-UV) analyses, indicated that the AW TWD derived tars were more aromatic in nature, containing more heavier boiling point components, which increased with increasing final pyrolysis temperature. The chars were characterised by proximate, ultimate, X-ray diffraction (XRD), X-ray fluorescence (XRF), diffuse reflectance infrared Fourier-transform (DRIFT) and BET CO2 analyses. Addition of either 5 wt% calcite, dolomite, kaolinite, pyrite or quartz to the acid washed fraction (AW TWD) was done in order to determine the effect of these minerals on the pyrolysis products. These minerals were identified as the most prominent mineral phases in the Highveld coal used in this study, by XRD and quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) analyses. It was found that mineral activity decreased in the order calcite/dolomite>pyrite>kaolinite>>>quartz. Calcite and dolomite addition led to a decrease in tar yield, whilst the gas yields were increased. Markedly, increased water yields were also observed with the addition of calcite, dolomite and pyrite. Kaolinite addition led to increased tar, char and gas yields at 520°C, whilst the tar yield decreased at 750°C. Pyrite addition led to decreased tar and gas yields. Quartz addition had no noteworthy effect on pyrolysis yields and composition, except for a decrease in char yield at all final pyrolysis temperatures and an increased gas yield at 520°C. Regarding the composition of the pyrolysis products, the various minerals had adverse effects. Calcite and dolomite affected the composition of the gas, tar and char phases most significantly, showing definite catalytic activity. Tar producers should take note as presence of these minerals in the coal feedstock could have a significant effect on the tar yield and composition. Kaolinite and pyrite showed some catalytic activity under specific conditions. Model coal-mineral mixtures confirmed synergism between coal-mineral and mineral-mineral interactions. Although some correlation between the pyrolysis products derived from the model coal-mineral mixtures and that of TWD coal was observed, it was not possible to entirely mimic the behaviour of the coal prior to acid washing. Linear regression models were developed to predict the gas, tar and char yields (d.m.m.f.) with mineral composition and pyrolysis temperature as variables, resulting in R2 coefficients of 0.837, 0.785 and 0.846, respectively. Models for the prediction of H2, CO, CO2 and CH4 yields with mineral composition and pyrolysis temperature as variables resulting in R2 coefficients of 0.917, 0.702, 0.869 and 0.978, respectively. These models will serve as foundation for future work, and prove that it is feasible to develop models to predict pyrolysis yields based on mineral composition. Extending the study to coals of different rank can make the models universally applicable and deliver a valuable contribution in industry. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

Mineral matter affect various coal properties as well as the yield and composition of products released during thermal processes. This necessitates investigation of the effect of the inherent minerals on the products derived during pyrolysis, as pyrolysis forms the basis of most coal utilisation processes. A real challenge in this research has been quantifying the changes seen and attributing these effects to specific minerals. Thus far it has been deemed impossible to predict product yields based on the mineral composition of the parent coal. Limited research regarding these aspects has been done on South African coal and the characterisation of pyrolysis products in previous studies was usually limited to one product phase. A novel approach was followed in this study and the challenges stated were effectively addressed. A vitrinite-rich South African coal from the Highveld coal field, was prepared to an undersize of 75 μm and divided into two fractions. HCl/HF acid washing reduced the ash yield from 14.0 wt% d.b. to 2.0 wt% d.b. (proximate analysis). Pyrolysis was carried out with the North-West University (NWU) Fischer Assay setup at 520, 750 and 900°C under N2 atmosphere and atmospheric pressure. The effect of acid washing and the addition of minerals on the derived pyrolysis products were evaluated. Acid washing led to lower water and tar yields, whilst the gas yields increased, and the char yields were unaffected. The higher gas yield can be related to increased porosity after mineral removal as revealed by Brunauer-Emmett-Teller (BET) CO2 adsorption surface area analysis of the derived chars. Gas chromatography (GC) analyses of the derived pyrolysis gases indicated that the acid washed coal fraction (AW TWD) derived gas contained higher yields of H2, CH4, CO2, C2H4, C2H6, C3H4, C3H6 and C4s when compared to the gas derived from the raw coal fraction (TWD). The CO yield from the TWD coal was higher at all final pyrolysis temperatures. Differences in gas yields were related to increased tar cracking as well as lower hydrogen transfer and de-hydrogenation of the acid washed chars. Analyses of the tar fraction by means of simulated distillation (Simdis), gas chromatography mass spectrometry (GC-MS) –flame ionization detection (–FID) and size exclusion chromatography with ultraviolet (SEC-UV) analyses, indicated that the AW TWD derived tars were more aromatic in nature, containing more heavier boiling point components, which increased with increasing final pyrolysis temperature. The chars were characterised by proximate, ultimate, X-ray diffraction (XRD), X-ray fluorescence (XRF), diffuse reflectance infrared Fourier-transform (DRIFT) and BET CO2 analyses. Addition of either 5 wt% calcite, dolomite, kaolinite, pyrite or quartz to the acid washed fraction (AW TWD) was done in order to determine the effect of these minerals on the pyrolysis products. These minerals were identified as the most prominent mineral phases in the Highveld coal used in this study, by XRD and quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) analyses. It was found that mineral activity decreased in the order calcite/dolomite>pyrite>kaolinite>>>quartz. Calcite and dolomite addition led to a decrease in tar yield, whilst the gas yields were increased. Markedly, increased water yields were also observed with the addition of calcite, dolomite and pyrite. Kaolinite addition led to increased tar, char and gas yields at 520°C, whilst the tar yield decreased at 750°C. Pyrite addition led to decreased tar and gas yields. Quartz addition had no noteworthy effect on pyrolysis yields and composition, except for a decrease in char yield at all final pyrolysis temperatures and an increased gas yield at 520°C. Regarding the composition of the pyrolysis products, the various minerals had adverse effects. Calcite and dolomite affected the composition of the gas, tar and char phases most significantly, showing definite catalytic activity. Tar producers should take note as presence of these minerals in the coal feedstock could have a significant effect on the tar yield and composition. Kaolinite and pyrite showed some catalytic activity under specific conditions. Model coal-mineral mixtures confirmed synergism between coal-mineral and mineral-mineral interactions. Although some correlation between the pyrolysis products derived from the model coal-mineral mixtures and that of TWD coal was observed, it was not possible to entirely mimic the behaviour of the coal prior to acid washing. Linear regression models were developed to predict the gas, tar and char yields (d.m.m.f.) with mineral composition and pyrolysis temperature as variables, resulting in R2 coefficients of 0.837, 0.785 and 0.846, respectively. Models for the prediction of H2, CO, CO2 and CH4 yields with mineral composition and pyrolysis temperature as variables resulting in R2 coefficients of 0.917, 0.702, 0.869 and 0.978, respectively. These models will serve as foundation for future work, and prove that it is feasible to develop models to predict pyrolysis yields based on mineral composition. Extending the study to coals of different rank can make the models universally applicable and deliver a valuable contribution in industry. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015