Mass Balance Simulation for Steam Reformer in Direct Reduction of Iron Ore by Hyl III Process.

Abstract

HYL direct reduction of iron ore process uses a reducing gas composed of a mixture of H2 and CO in order to reduce iron oxide pellets to metallic iron (DRI). This process is mainly dependent on a reformer to supply the reducing gas. In the reformer, natural gas is catalytically converted into reducing gas by reaction with steam at a temperature of 800 to 850°C and pressure between 8 and 8.5 bars in the presence of Nickel based catalyst. In order to analyze the reformer operation, it is necessary to estimate the reformed gas composition for some specific process conditions. The present work is based on the solution of a set of non-linear equations describing mass balances of carbon, hydrogen, oxygen and higher hydrocarbons, to enable the calculation of reformed gas composition for a steam reformer. The procedure can assist both process engineers tackling the problem of estimating output from a primary reformer at the design stage and plant operating engineers. The mass balance equations are solved by using the equilibrium constants for the reforming and water gas shift reactions. This includes simultaneously solving non-linear equations relating to the composition of reactants and other variables as temperature and pressure at which reactions take place. In addition, amount of carbon contained in natural gas compared to amount of steam used in steam reforming reaction is also considered during calculations. The basic requirements to establish the model are a set of reactions and values of equilibrium constants for the reforming and water gas shift reactions.