Voltage flicker limitation of electric utilities has been discussed in the past three decades. Arc furnace is one of the most disturbing loads that cause flicker problems in the power network. If displeasing flicker levels are predictable, then corrective solution such as static var compensation or furnace controls could be developed in cooperation between the utility and the customer. In the past, the electric fluctuations in the arc furnace voltage have been proven to be chaotic in nature. This thesis proposes a phase space approach based on nonlinearity chaotic techniques to analyze and predict voltage flicker. The determination of the phase space dimension and the application of Lyapunov exponent for flicker prediction are described. Test results have shown that accurate prediction results are obtainable for short term flicker prediction based on chaos theory.

The raceway in the ironmaking blast furnace is a void in front of the hot blast tuyeres where coke and supplementary fuel burn to supply heat to the ironmaking process. The air velocity through the tuyeres is high (around 200 m/s) and this causes the coke particles to circulate in a rotating flow field inside the raceway. The size and shape of the raceway determine the gas flow dstribution, the reactions that occur, and the temperature profiles in the lower part of the blast furnace. It is for these reasons that the raceway has been extensively researched in the past. . Literature review revealed that forming and breaking of the raceway has not been yet studied. So, in the present study, we have concentrated our effort to study the formation and breaking of the raceway for different blast and bed parameters. The experiments have been performed in two-dimensional glass models. An attempt has been made to develop a correlation for each case. The formation of the void has been studied with change in parameters like density and size of the particles, bed height. The theory of the void formation has been derived from the fundamental principles. The formation of raceway, has been studied with the change in blast parameters like particle density and diameter, bed height and model width. It was found that when raceway is formed there is a sudden increment in pressure drop. The condition for breaking of the raceway, has been studied with change in blast and bed parameters like particle size and density, bed height and model width. It was observed that during the breaking of raceway, pressure decreases continuously. New semi-empirical correlations have been developed using dimensional analysis for formation of void, formation of raceway, and breaking of the raceway. The raceway growth also characterized with change in model width, flow rate, particle diameter, density of the particles and bed height. A few experimental results have been compared with published data. New semi-empirical correlation have been developed using dimensional analysis for the growth of raceway. Velocity of the gas exiting from top of the bed has been measured with the help of hot wire anemometer. It was observed that the velocity leaving from the bed is more on top of the raceway compared to the velocity leaving from the other parts of the bed. High velocity was observed near the wall of the model. Coefficient of wall-friction and angle of internal friction in presence and absence of gas were studied to explain the effect of bed height on formation of the void and raceway. It was observed that in presence of gas, coefficient of friction between the particles and wall and angle of internal friction between particles decreased, compared to the values in absence of gas. To study the effect of mixed particles, on the formation and breaking of the raceway, different sized particles in fixed proportion were taken. It was found that the experiments were more reproducible in case of uniform sized particles compared to mixed particles. It was also observed that for the same average particle diameter, mixture particles requires more velocity to form the void and raceway. New semi-empirical correlations have been developed using dimensional analysis for the formation of void, formation of raceway, growth of the raceway, and breaking of the raceway. Finally, an attempt has been made to quantify the various forces (pressure, bed weight & frictional forces) present in the raceway. Results show that further investigation is required in quantifying these forces properly.

Thesis (MTech. degree in Chemistry)--Tshwane University of Technology, 2008. / This work is aimed at experimental verification of the theory about the advantages of the two-step sample vapour release in a fast-heated ballast furnace. The term “ballast” was introduced earlier in electrothermal atomic absorption spectrometry, as an alternative to a platform to describe a compact body of refractive material loosely located on the bottom of a tube furnace atomiser. The thermal behaviour of the ballast furnace is similar to that of the platform, but without restriction created by the platform area. Compared with the flat or concave platform, a compact ballast of similar mass to the platform should have less impact on gas temperature because of the smaller surface area. The theoretical predictions concerning atomisation efficiency in the fast-heated ballast furnace were examined by the determination of metals in organic and inorganic matrices using a Quantum Z.ETA atomic absorption spectrometer. The instrument provided fast heating of the tube atomizer, 10 K ms-1. It is shown that in the employed ballast furnace the vapour released into the gas phase occurs after interim condensation on the ballast. For the samples of tetraethyllead, base oil and aqueous solutions of various metals, analytical signals are observed after stabilisation of tube temperature, independent of volatility of the analyte and level of temperature setting. For those samples, a high gas phase temperature provides complete recovery of the analyte without involvement of chemical modifiers and the reduction of spectral interferences from chloride matrices.

published_or_final_version / Chemistry / Master / Master of Philosophy

Ultraviolet-visible chemiluminescent emission features in laboratory-scale flames have been shown by several researchers to correlate well with the flame's equivalence ratio, and it has been suggested that this relation could be used to actively control flames. This study investigated the feasibility of extending this knowledge to the industrial setting. Radiative emissions from basic oxygen furnace (BOF) and thermal generating station burner flames were mainly characterized by thermally-induced greybody spectra; emissions from electronically excited species of OH*, OH*, and CO2* were generally weak and did not offer any unique information that could be used as part of a flame diagnostic system. A sub-study which assessed the impact of biomass cofiring demonstrated that emissions of SO2, NOx, and fossil-CO2 could be reduced with direct fuel replacement. The sensor system could be used as a pyrometer, and as part of a burner balancing strategy to counter increased CO emissions and decreased efficiency.

Ultraviolet-visible chemiluminescent emission features in laboratory-scale flames have been shown by several researchers to correlate well with the flame's equivalence ratio, and it has been suggested that this relation could be used to actively control flames. This study investigated the feasibility of extending this knowledge to the industrial setting. Radiative emissions from basic oxygen furnace (BOF) and thermal generating station burner flames were mainly characterized by thermally-induced greybody spectra; emissions from electronically excited species of OH*, OH*, and CO2* were generally weak and did not offer any unique information that could be used as part of a flame diagnostic system. A sub-study which assessed the impact of biomass cofiring demonstrated that emissions of SO2, NOx, and fossil-CO2 could be reduced with direct fuel replacement. The sensor system could be used as a pyrometer, and as part of a burner balancing strategy to counter increased CO emissions and decreased efficiency.

Antrojoje darbo dalyje aprašyta gaminio paskirtis ir panaudojimo galimybės bei alternatyvos, išnagrinėti pakūrą sudarantys elementai: mazgai, mechanizmai. Atlikta katilo pakūros mazgų konstrukcijos variantų apžvalga – įvairiausių detalių, standartinių gaminių, konstrukcinių sprendimų palyginimas. Atlikti gaminio techniniai skaičiavimai (šiluminės izoliacijos ir nuostolių skaičiavimas, hidrostotelės elementų skaičiavimas, ardelių judinimo hidraulinių cilindrų skaičiavimas, pelenų šalinimo mazgo techniniai skaičiavimai). Trečiojoje darbo dalyje išanalizuota vienos detalės, iš kiekvieno pakūros mazgo, technologiniai maršrutai, nustatyti apdirbimo operacijoms reikalingi įrengimai, apskaičiuotas jų kiekis. Atliktas užlaidų, pjovimo režimų nustatymas bei techninis normavimas. Ketvirtojoje darbo dalyje pateikiama žmonių ir aplinkos saugos reikalavimai eksploatuojant įrenginį, jo ergonomiškumas ir įtaka aplinkai. Penktojoje darbo dalyje atlikti ekonominiai skaičiavimai, kurių pagalba nustatyta ir pagrįsta 1,5 megavato katilo pakūros savikaina. / The aim of the study is to design Boiler-stove furnace of 1,5 megawatt. The first part of bachelor thesis analyses the main technical parameter of boiler-stove furnace of 1,5 megawatt, its operating efficiency, the production volume is provided. The second part describes the function of the product, its usability and possible options, the assemblies and mechanisms - elements constituting the furnace are examined. The review of boiler furnace assembly options design is carried out – various details, standard products, constructive solutions are compared. Technical calculations of the product are performed (calculation of thermal insulation and loss, calculation of hydro-station elements, fire bars moving hydraulic cylinders calculation, technical calculation of ash removal unit). In the third part technological routes of one detail from every furnace component are analyzed, the equipment necessary for processing operations is assigned, calculated its amount. The allowance, determination of cutting regimes and technical rationing is accomplished. The fourth part presents human and environmental safety requirements while operating a device, its ergonomics and environmental impact. Economic calculations are fulfilled in the fifth part. With the help of them the cost of 1,5 megawatt boiler stone Furnace is determined and justified.

Secondary (recycled) aluminum constitutes around 48% of the total aluminum used in the United States. Secondary aluminum melting is accomplished in large reverberatory furnaces, and improving its energy efficiency has been one of the major interests to aluminum industries. To assist the industries in improving energy efficiency in aluminum melting, an experimental research furnace (ERF), with 907 kg (2000 lbs) capacity, has been built at the Albany Research Center of the U.S. Department of Energy as part of this multi-partner research program. To verify that the experimental results obtained in the ERF furnace are valid for the operation of industrial furnaces, we used scale modeling technology to assist the validation. In this thesis, scaling laws, which are applied to the thermal conduction loss through the model furnace, were developed and the partial modeling relaxation technique was applied to the development of modeling to derive achievable scaling laws. The model experiments were conducted in the model furnace, which was a one-fourth scaled-down version from the ERF furnace (as a prototype), and then compared to the tests in the ERF furnace. The temperature distributions across both the model and prototype were shown to be in good agreement. Confirmation of the scaling laws demonstrated the usefulness of the scale modeling concept and its applicability to analyze complex melting processes in aluminum melting.

The PCI technology is well established for reducing the consumption of economic and environmentally expensive coke in blast furnace iron-making. Often, coal blends show unexpected combustion performance which cannot be explained on the basis of individual coal properties particularly coal rank and volatile matter. Several coals were combusted in this study under controlled conditions in a drop tube furnace. Fixed bed reactor, XRD, SEM and BET analyses were used to understand the mechanism of combustion of coal blends. Burnout of the coal blends did not change linearly with volatile matter of blends. The study demonstrated that combustion behaviour of coal blends was influenced by several properties of individual coals and cannot be estimated by using any single coal parameter. Carbon structure of coal as well as the interaction of volatile matter of individual coals was found to have a strong influence on the burnout of coal blends. Pet-cokes were generally found to burn with a greater difficulty. Carbon structure of pet-cokes was found to have a significant effect on the burnout such that coal blends with highly ordered pet-coke indicated lower burnout. The study shows that up to 10% of pet coke did not change the burnout of PCI blends significantly. As far as combustion is concerned, the drop tube furnace test provides a reasonable distinction of the effect of coal properties for PCI application.

Thesis -- Departmental honors in Chemistry. / Bibliography: ℓ. 26-28.