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O controle das características da escória de refino primário pode ser realizado pela adição de fluxantes, sendo comumente utilizado a Fluorita (CaF2), isto porque a Fluorita aumenta a solubilidade de CaO e, por conseguinte, aumenta a capacidade de desfosforação de escória. Apesar disso, alguns estudos advertem sobre o risco de liberação de gás tetra fluoreto de silício, que tem caráter nocivo para o meio ambiente. Outro problema relatado é o aumento do desgaste do revestimento refratário impactando nos custos de produção. Neste trabalho de mestrado o uso de Sodalita Nefelínica como fluxante foi comparado com a Fluorita em relação ao desgaste de refratários a base de MgO-C e à fluidez. Os ensaios consistiram em dopar escória de conversor LD com diferentes quantidades de Fluorita e Sodalita (1, 2, 3, 4 % em massa). Os resultados demonstraram que a Fluorita fornece uma escória com menor ponto de fusão e mais fluida, porém ela causa maior desgaste no revestimento refratário, mais que o dobro do desgaste causado pela Sodalita. Acredita-se que isso tenha ocorrido devido a Fluorita ser capaz de aumentar a dissolução tanto do CaO presente na escória quanto do MgO presente no refratário. Este processo é intensificado pela baixa viscosidade apresentada com este fluxante. / The control of the slag characteristics from primary refining can be accomplished by adding fluxes, being commonly used Fluorite (CaF2). This happens because the fluorite increases the solubility of CaO and thus increases the ability of the slag dephosphorization. Nevertheless, some studies warn about the risk of releasing silicon tetra-fluoride gas which has harmful character to the environment. Another problem reported is the increased wear of the refractory lining impacting on production costs. In this master dissertation the use of Sodalite Nepheline as flux was compared with Fluorite concerning MgO-C based refractories wear and fluidity. The tests consisted of doping LD converter slag with different amounts of Fluorite and Sodalite (1, 2, 3, 4 % mass). The results showed that the Fluorite provides a slag with a lower melting point and becomes more fluid, but it causes greater wear on the refractory lining, more than double the wear caused by Sodalite. It is believed that this has occurred due Fluorite be able to enhance the dissolution of the CaO in slag as well as MgO present in the refractory. This process is intensified by the low slag viscosity presented with this flux.

The focus of this thesis is the study of behavior of brick waste in the mixture with high alumina cement. The result of this research should be a draft of a composition and production process for material that could partly or fully substitute forging accessories in the brick production industry. The aim of this work is to verify the use of brick waste for such purpose. Usage of brick waste for refractories can help the current long-term effort for wasteless production processes.

Thesis (M. Med. Community Health)--University of Pretoria, 2003. / Includes bibliographical references (leaves 73-77).

Thesis (MBA (Business Management))--Stellenbosch University, 2008. / ENGLISH ABSTRACT: RHI Refractories believe that the process of outsourcing certain activities of a companies’ value chain goes hand in hand with a complete new way of how management think and do things. The process of outsource the refractory activity of a company’s value chain is not just a matter of outsourcing a part of the value chain that cannot influence the company’s performance negatively, but it can stop the process. To achieve a true business relationship RHI and SASOL must have the same goals in their goal setting to make the contract successful. RHI Refractories and SASOL shared goals: • The target to reduce the Total Cost of Ownership involving the refractory material on SASOL. • Both parties need a 100% buy-in in this concept and need to lay down a guideline on mutual profit sharing to end up with a win-win scenario. • RHI to supply SASOL with a competent installation crew and technical assistance in exchange for remuneration. • RHI and SASOL to have a long term relationship to ensure installation crew is familiar with plant conditions on contract work as well as project work. RHI Refractory’s strategy to supply the service has two major advantages: a. these type of contract ensures a constant monthly cash flow; b. It lifts the entry barriers for rival companies that they are unable to compete cost effective on additional project work that’s not part of the outsourcing contract scope. From the financial results RHI was successful in their strategy by securing 100% of all the material and additional project work on the SASOL site. RHI wanted to establish a relationship that can be classified as – NETWORK ORGANIZATION. This relationship would better the marketing position of RHI Refractories, it would secure a long term relationship, both companies would benefit from a shared vision and this would lead to a win-win situation. RHI Refractories definitely benefit from outsourcing contracts as a service provider and in the same way it controls rival companies by setting high entry barriers through cost sharing between contract and project work. / AFRIKAANSE OPSOMMING: RHI Refractories glo dat die proses van uitkontraktering van sekere aktiwiteite van 'n maatskappy se waardeketting 'n kompleet nuwe wyse is waarop bestuur dink en besigheid doen. Die proses van uitkontraktering van die vuurvaste funksie van 'n maatskappy se waardeketting is nie net 'n geval van uitkontraktering van 'n gedeelte van die waardeketting wat die maatskappy negatief kan beinvloed nie, maar dit kan die proses stop. Om 'n ware besigheidsverhouding te verkry, moet RHI en Sasol dieselfde doelwitte in hulle doelstelling hê om die kontrak suksesvol te maak. RHI Refractories en SASOL se gedeelde doelwitte: • Om die Totale Koste van Eienaarskap te verminder ten opsigte van vuurvaste materiale; • Beide partye moet 100% inkoop in die konsep en moet riglyne neerlê vir wedersydse winsdeling wat lei tot ‘n wen-wen verhouding; • RHI moet SASOL voorsien van 'n bevoegde installasie span en tegniese bystand vir vergoeding; • RHI en SASOL moet 'n langtermyn verhouding opbou om te verseker dat die installasie span vertroud is met die aanleg omstandighede, kontrak- en projekwerk. RHI se strategie om 'n diens te verskaf het twee groot voordele: • Hierdie tipe kontrakte verseker ‘n konstante maandelikse kontantvloei; • Dit lig die intree vlakke van mededingende maatskappye in so ‘n mate dat mededingende maatskapye nie koste doeltreffend kan meeding op projekte wat nie deel is van die bestaande kontrak nie. Vanuit die finansiele resultate is dit duidelik dat RHI suksesvol was in hulle strategie deur 100% van alle materiaal en projekwerk verkry het op die SASOL aanleg. RHI wil ’n verhouding bewerkstellig wat geklassifiseer kan word as – NETWERKVORMEND. So ’n verhouding sal ’n beter bemarkingsaanslag vir RHI beteken, dit sal ’n langtermyn verhouding verseker, beide maatskappye sal voordeel trek uit ’n gedeelde doelwit wat sal lei tot ’n wen-wen verhouding. RHI trek voordeel uit uitkontrakteerde kontrakte as ’n diensleweraar en in dieselfde tyd beheer dit mededingende maatskappye deur die intreevlakke te beheer deur kostedeling tussen kontrakwerk en projekwerk.

L’aluminium est fabriqué en phase liquide à 1000°C dans une cuve à électrolyse par réduction de l’alumine dissoute dans un bain fluoré contenant essentiellement de la cryolithe Na3AlF6. Les parois latérales des cuves d’électrolyse sont revêtues par des briques réfractaires, dites « dalles de bordure », à base de SiC lié par Si3N4. Ces dalles, qui déterminent en grande partie la durée de vie de la cuve d’électrolyse, sont soumises à la corrosion par le bain, l’aluminium liquide et les gaz fluorés dégagés. Afin de contribuer à une meilleure connaissance des mécanismes de corrosion de ces dalles, l’étude des échantillons « post-mortem » prélevés des cuves industrielles a été effectuée. La mise au point d’un dispositif de simulation de corrosion en laboratoire a permis de suivre l’évolution du matériau en fonction de la composition de l’agent de corrosion. Ces études ont permis de mettre en évidence la forte réactivité de la phase liante de la dalle dans tous les zones de la cuve. Le rôle majeur de sodium, qui provient du bloc cathodique et la pâte de brasque, comme accélérateur de la corrosion de la dalle a été confirmé. La corrélation entre l’oxydation et la corrosion a été démontrée. La dissolution de SiO2 dans le bain fluoré a été étudiée par RMN haute température in situ et par RMN MAS à température ambiante sur les échantillons solidifiés. Nous avons montré la formation de phases aluminosilicatées (albite et néphéline) qui ont une solubilité non négligeable dans la cryolithe. / Aluminum is produced in liquid phase at 1000 °C in an electrolysis cell by reduction of alumina dissolved in a bath containing essentially cryolite Na3AlF6. The sidewalls of the electrolysis cells are lined with refractory bricks, called « edge slabs », based on Si3N4 bonded SiC. These slabs, which largely determine the lifetime of the electrolysis cell, are submitted to corrosion by the bath, the liquid aluminum and fluoride gas released. To contribute to a better understanding of the corrosion mechanisms of these slabs, the study of postmortem samples from industrial cells has been completed. A specific furnace for corrosion measurements in molten fluorides has been developed in order to characterize the evolution of the refractory with the composition of the corrosion agent. These studies highlight the high reactivity of the binding phase of the slab in all parts of the cell. The role of sodium, which comes from the cathode block and the ramming paste, and acts as an accelerator of corrosion has been confirmed. The correlation between oxidation and corrosion has been demonstrated. The dissolution of SiO2 in the cryolitic bath has been studied in situ by NMR at high-temperature and by NMR MAS on solidified samples at room temperature. We have shown the formation of aluminosilicate phases (albite and nepheline) which have a significant solubility in cryolite.

Lightweight refractory products are materials used for the construction of certain parts of industrial furnaces, especially for iron, but also in other sectors where is operated with high temperatures. There are special requests on refractories. The theoretical part contains an overview of used raw materials, production and properties of lightweight refractory products and description of not burnable lightener - chemical additives VUPPOR I and information about previously conducted trials dealing with these topics. The practical part is divided into four parts, which are evaluated by tests which were performed on a refractory clay with chemical additive Vuppor I (samples are lightened and not lightened) - it was primarily a test of sensitivity to drying, density, compressive strength, thermal insulating properties, etc.

The thesis deals with the possibility of utilization of fluid ash in refractory materials and its influence on resulting properties. This work studies the effect of bed and filter ash addition on properties of the droplet and resulting mechanical properties, bulk density, shrinkage and firing temperature of stove fireclay. The subject of this thesis is also reduction of SO2 emissions evolved burning of fireclay containing fluid ash rich of anhydrite. Emissions of SO2 were observed by TG-TDA-EGA method. Characterization of prepared samples and study of heat treatment processes was based on XRD, TG-DTA-EGA, TDA, SEM–EDS, heating microscope and isothermal calorimetry.

Thermal shock resistance is a key property of refractory materials. Its determination and prediction is essential for the design of structural refractories as well as lining materials. Young’s modulus of elasticity (E) is a crucial parameter for the calculation of thermal shock resistance. For all investigated carbon-bonded alumina composition a significant increase of E was observed. This increase was attributed to a mismatch of the coefficient of thermal expansion of the composite constituents. Besides others, the graphite content as well as the maximum alumina particle size were identified as crucial factors influencing E(T). Furthermore, the influence of the porosity on E was shown and existing models were fitted to the experimental data for future predictions of E. Finally a metal melt filter structure was investigated to investigate the relationship between its strut Young’s modulus and the structures’ E at high temperatures. Further research should address the filter topic since it was uncertain how to find the normal modes of those structures.