This paper presents the numerical simulation of the technology of gaseous fuel utilisation for iron ore sintering. The proposed methodology is to partially replace the solid fuel by steelworks gases. A multiphase mathematical model based on transport equations of momentum, energy and chemical species coupled with chemical reaction and phase transformations was proposed to analyse temperature distributions of the process. A base case of actual industrial operation of a large sintering machine was monitored with thermocouples inserted into the sinter bed to validate the model. The model was used to predict four cases of fuel gas utilisation: feeding from N01 to N15 wind boxes with blast furnace gas (BFG); natural gas (NG); coke oven gas (COG); and a 50-50 mixture of BFG and COG. The model predictions indicated that for all cases the sintering zone is enlarged and the solid fuel consumption could be decreased. List of symbolsA surface area, m 2 m 23 C p heat capacity, J kg 21 K 21 d final solid agglomerated, m d initial initial micropellets charged, m d m solid component diameter, m d s solid phase mean diameter, m F s g interaction force on solid phase due to gas phase, N m 23 s 21 H enthalpy of the phase, kJ kg 21 P phase pressure, Pa Pr g~C p,g m g k g Prandtl number r m rates of chemical or phase transformations, kmol m 23 s R gas constant, J mol 21 K 21 Re g{s~r gŨ U g {Ũ U s m g d s particle Reynolds number S w source or sink terms for the w variables, (various) t time, s T temperature, KŨ U i phase velocity vector (i is the gas and solid), m s 21 x i spatial coordinates, m e i volume fractions, m 3 m 23 m phase effective viscosity, Pa s r i phase density (i is gas and solid), kg m 23 Q n mass fraction in equation (4) (calculated by the model), kg kg 21 w m solid diameter shape factor (m is the sinter feed, sinter return, limestone, fines, coke, mushy and bonding)
ResumoVisando a estudar novas alternativas para o processo de sinterização, a utilização de gases combustíveis tem proporcionado reduções significativas no consumo de combustíveis sólidos, além de propiciar maior controle da qualidade física e metalúrgica do sínter. Nesse estudo, é utilizado um modelo de sinterização para avaliar a injeção de gás de coqueria no processo. Foram analisados cinco casos de injeção de gás de coqueria, visando, sempre, a uma operação estável do processo. Os resultados de simulação indicam um menor consumo de combustível sólido com a injeção do gás de coqueria e alargamento da frente de combustão. Como resultado desse processo, houve um aumento da fração de cálcio-silicatos, o que propiciou uma melhoria na redutibilidade e uma redução na quantidade de CO 2 no gás de saída.Palavras-chave: Sinterização, gás de coqueria, simulação computacional. AbstractIn order to study new alternatives for the sintering, the use of gaseous fuels has provided a significant reduction in the consumption of solid fuels, and also propitiates better quality control of physical and metallurgical sinter properties. In this study, a sintering model is proposed to evaluate the injection of coke oven gas in the process. We analyze five cases of coke oven gas injection always seeking a stable operational process. The simulation results indicate a lower consumption of solid fuel with the injection of coke oven gas and an increase of the combustion front. As a result, this increased the fraction of calcium silicates, which consequently improved the reducibility and also reduced the amount of CO 2 in the output gas.
This paper deals with the numerical simulation of the new technology of gaseous fuel utilization on the sintering process of iron ore. The proposed methodology is to partially replace the solid fuel(coke breeze) by steelworks gases. A multiphase mathematical model based on transport equations of momentum, energy and chemical species coupled with chemical reaction rates and phase transformations is proposed to analyze the inner process parameters. A base case representing the actual industrial operation of a large sintering machine is used with thermocouples inserted into the sintering bed to record the inner bed temperatures and compare with model predictions in order to obtain model validation and parameters adjustment. Good agreement of the temperature pattern was obtained for the base case and thus, the model was used to predict four cases of fuel gas utilization: a) 2% of the wind boxes inflow from N01-N15 wind boxes of natural gas(NG), b) same condition with coke oven gas(COG), c) same condition with blast furnace gas(BFG) and d) mixture of 50% COG and 50% BFG. The model predictions indicated that for all cases, except only BFG, the sintering zone is enlarged and the solid fuel consumption is decreased about 8kg/t of sinter product. In order to maximize the steelworks gas utilization it is recommended the use of mixture of COG and BFG with optimum inner temperature distribution
O presente trabalho apresenta um modelo matemático capaz de prever a influência das propriedades de amolecimento e fusão da mistura de matérias primas na cinética de formação dos constituintes cálcio ferrita e dicálcio ferrita na sinterização de minério de ferro. O modelo é baseado na solução simultânea das equações de transporte de Momentum, energia e espécies químicas formuladas para sistemas multifásico e multicomponente, acoplado à cinética de reações químicas e transformações de fases que ocorrem no interior da esteira de sinterização. A solução numérica é obtida utilizando-se o método de volumes finitos validado com resultados de monitoramento de uma planta industrial de sinterização. Os resultados indicam que as temperaturas de início de amolecimento, contração volumétrica e intervalo de fusão são os principais parâmetros a serem controlados visando obtenção de formação de fase líquida que confere resistência mecânica e redutibilidade adequadas ao sínter. Neste estudo confirma-se que matérias primas com alto ponto de amolecimento e fusão combinado com alta contração volumétrica e grande intervalo de temperatura da zona pastosa podem diminuir até 20% o volume de fase líquida formada e, consequentemente, diminuir em mais de 30% a formação de cálcio ferritas o que deterioraria consideravelmente as propriedades finais do sínter.
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