Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2009.

Coal, as energy resource, possesses numerous characteristics and properties which all have an influence on its gasification behaviour. The two properties considered critically important when evaluating a coal source for gasification are its mineral content and slagging behaviour. Research has indicated that slag formation can be inhibited or even prevented by the addition of a fluxing agent. It is thus of great importance to understand the mineral interaction during gasification, in order to select a suitable fluxing agent for the prevention of slagging and clinker formation in the gasifier. The aim of this dissertation is to evaluate the slagging properties of a coal source with the addition of iron as a fluxing agent and to study the transformation of the mineral and added iron during gasification. A pre-determined amount of elemental iron (between 2 and 20 percentage by mass) was added to three different coal samples obtained from Sasol's operations in South Africa. The transformation of the iron in conjunction with the possible iron-containing minerals present in the coal was studied by means of Mossbauer spectroscopy. Typical characterisation analyses were also carried out on the original coal samples. The ash fusion temperature analyses (AFT) were used to study the slagging behaviour of the iron-spiked coal samples. Even though AFT analyses only provide an average flow property, it gives a good indication of the changes that the iron addition induces in coal properties. FactSage modelling was carried out in conjunction with the Mossbauer and AFT analyses. The AFT analysis on all of the samples indicated that the iron addition led to a 20% decrease in the AFT of all three the coal samples. The decrease observed, can be attributed to three main reasons: Formation of lower melting iron-containing phases, bridging of oxygen bonds by FeO and Fe203and the lowering of the viscosity by the iron-oxides, mainly hematite. Mossbauer spectra of the three original coal samples indicated that pyrite was the only iron-bearing mineral present / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2009.

Coal, as energy resource, possesses numerous characteristics and properties which all have an influence on its gasification behaviour. The two properties considered critically important when evaluating a coal source for gasification are its mineral content and slagging behaviour. Research has indicated that slag formation can be inhibited or even prevented by the addition of a fluxing agent. It is thus of great importance to understand the mineral interaction during gasification, in order to select a suitable fluxing agent for the prevention of slagging and clinker formation in the gasifier. The aim of this dissertation is to evaluate the slagging properties of a coal source with the addition of iron as a fluxing agent and to study the transformation of the mineral and added iron during gasification. A pre-determined amount of elemental iron (between 2 and 20 percentage by mass) was added to three different coal samples obtained from Sasol's operations in South Africa. The transformation of the iron in conjunction with the possible iron-containing minerals present in the coal was studied by means of Mossbauer spectroscopy. Typical characterisation analyses were also carried out on the original coal samples. The ash fusion temperature analyses (AFT) were used to study the slagging behaviour of the iron-spiked coal samples. Even though AFT analyses only provide an average flow property, it gives a good indication of the changes that the iron addition induces in coal properties. FactSage modelling was carried out in conjunction with the Mossbauer and AFT analyses. The AFT analysis on all of the samples indicated that the iron addition led to a 20% decrease in the AFT of all three the coal samples. The decrease observed, can be attributed to three main reasons: Formation of lower melting iron-containing phases, bridging of oxygen bonds by FeO and Fe203and the lowering of the viscosity by the iron-oxides, mainly hematite. Mossbauer spectra of the three original coal samples indicated that pyrite was the only iron-bearing mineral present / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2009.

The quality of aluminium cast billets is highly dependent on the cleanliness of the material. Hydro Extruded Solutions are casting billets in Sjunnen that are delivered for extrusion within the same company. In order to produce extruded profiles of high quality and also maintain the pressing tools, it is a good method to keep the billets as free from inclusions as possible. A fluxing agent in form of salt compounds is used to purify the material during melting, but also to protect it from further oxidation. Another task of fluxing agents is to minimize the aluminium amount in the dross phase. The purpose of this project was to investigate if the fluxing agent that is used by the cast house is having any impact on the quality of the billets. Therefore, for that purpose, samples with a variating amount of fluxing agent were processed by the cast house in order to be investigated. These samples were investigated with the Optical Microscopy-method in order to determine the area fraction of non-metallic inclusions inside them. The results did not reveal any significant difference in the quality of the different samples since most samples obtained a low OM-index after the investigation. That can be explained by the type of scrap that was used since new scrap is usually very clean and contains smaller amounts of inclusions. / Kvaliteten hos aluminiumgöt är starkt beroende av renheten i materialet. Hydro Extruded Solutions gjuter rundgöt i Sjunnen, som sedan levereras för strängpressning inom samma företag. För att producera strängpressade profiler av hög kvalitet och även upprätthålla pressverktygen, är en bra metod att hålla göten så fria från inneslutningar som möjligt. Ett flussmedel, i form av saltföreningar, används för att rena materialet under smältningen, men också för att skydda den från vidare oxidation. En annan uppgift som flussmedel har är att minimera mängden aluminium i slaggfasen. Syftet med detta projekt var att undersöka om flussmedelet som används av omsmältverket har någon inverkan på götkvaliteten. Därför, för detta ändamål har prover med en varierande mängd av flussmedel tillverkats i omsmältverket för att bli undersökta. Dessa prover undersöktes med den Optiskt Mikroskopiska-metoden för att bestämma areafraktionen av icke-metalliska inneslutningar inuti dem. Resultaten avslöjade inte någon signifikant skillnad i kvaliteten hos de olika proverna eftersom de flesta prover erhöll ett lågt OM-index efter undersökningen. Detta kan förklaras av vilken typ av skrot som användes, då process-skrot oftast är väldigt rent och består av mindre mängder innseslutningar.