الفهرس 
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Abstract
The main two components in HYL direct reduction of iron ore plants are pressurized reactor and steam reformer. Reactor is used to reduce iron ore to direct reduced iron (DRI), while reformer is used for generating the reducing gases(H2,CO). The reduction process of iron ore inside the reactor takes from 8- 14 hours based on residence time. Normally the physical sample to evaluate the quality of the product takes the same time which is risky if negative results are obtained. In this study, it is proposed to establish two models one to predict product quality and the second to calculate reformer efficiency for HYL iii module, at an 1.9 million tons annual capacity industrial plant. In both models, Visual Basic for Application “VBA” is used during model’s development The Reactor model is developed based on the theory of thermodynamics of reduction process. Reactor model can easily predict DRI metallization and carbon content through the mass balance simulation, Model was validated by using measurements from plant which showed maximum difference near to 2 % between actual and calculated one. Steam reformer model is established based on the concept of steam reforming and reactions equilibrium theory. Steam reformer consists of seven heat exchangers bundles to recover waste heat coming with flue gas from reformer firing box. Reformer model is used to evaluate its efficiency, catalyst activity and also prediction of reformed gas quality and chemical composition. Model was validated by using actual measurements from plant that was implemented to the mass and heat balance model which consists of two sub models, mass balance and heat balance, results showed conformity of both actual and calculated results. By studying effect of steam to carbon ratio, temperature of reaction and Natural gas composition, the following results were obtained: by varying different operating parameters for steam reformer such as Steam to carbon ratio (S/C) “ H2 in reformed gas increased from 71.5 to 75% when S/C increased from 2.6 to 3.1. “Reformed gas outlet temperature “H2 in reformed gas increased from 74.6 to 75.8 % when Temperature increased from 750 C to 825 °C. “Natural gas composition “increasing CH4 methane in natural gas affected directly efficiency of reformer as methane is much easier to be reformed rather than other heavy hydrocarbons”. Further reformer model was used after validation to study the effect of steam to carbon ratio and temperature of reformed gas on reducing gas quality entering reactor, regarding both reducers’ ratio “(H2+CO)/(H2O+CO2)” and H2+CO percentage in reducing gas. iii | P a g e It was found that increasing S/C ratio will increase H2 and CO percentages in reducing gas until a certain value normally 2.5 then it will decrease again, reducers ratio will always decrease when increasing steam to carbon ration because of formation of CO2. Regarding effect of temperature, it was observed that increasing of reformed gas temperature is always favorable for producing H2 and CO but equipment design limits must be considered.