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Articles by D. Subbarao
Total Records ( 4 ) for D. Subbarao
  U.B. Deshannavar , M.S. Rafeen , M. Ramasamy and D. Subbarao
  Fouling in crude preheat train heat exchangers in refineries is a complex phenomenon. Crude oil fouling undergoes different mechanisms at different stages of preheating. Understanding the fouling mechanisms is essential in formulating appropriate fouling mitigation strategies. The use of the concept of threshold fouling conditions is one of the approaches for mitigating fouling through operating conditions. In this study, an attempt has been made to review the various fouling models available in literature, their advantages and limitations.
  Y. Uemura , W. Omar , T. Tsutsui , D. Subbarao and S. Yusup
  In this study, the relationship between calorific value and elementary composition of torrefied oil palm wastes (empty fruit bunches, mesocarp fiber and kernel shell) and other lignocellulosic biomass is discussed. Several correlations for calorific value vs. elementary composition for biomass were examined for their applicability to torrefied lignocellulosic biomass. One of the correlations was selected as the most appropriate for the purpose, based on average absolute error between observed and estimated calorific values. In addition, the triangle plot of carbon, hydrogen and oxygen contents in untreated and pyrolyzed biomass is proposed as an appropriate tool for discussing biomass decomposition behavior.
  S.F.H. Tasfy , N.A.M. Zabidi and D. Subbarao
  Iron-based catalyst is the most common catalyst for Fischer-Tropsch Synthesis (FTS), which is a process to synthesize transportation fuel and chemicals feedstock from the syngas. The effect of synthesis technique, iron loading and catalyst supports on the physicochemical properties of iron-based catalyst was investigated. Impregnation and precipitation methods were used to synthesize the supported iron-based nanocatalysts containing various iron loadings. Silica and alumina silica were used as catalyst supports to modify the catalyst properties in producing well defined phases. The supported iron nanocatalysts were characterized using N2 physical adsorption, Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM) and Temperature-Programmed Reduction (TPR). For the catalysts prepared via impregnation method, the surface area remained at 23 m2 g-1 for catalyst containing different iron loading. However, for those prepared via the precipitation method, the surface area of the catalyst increased with increasing iron loading. Precipitation method resulted in highly agglomerated iron nanoparticles. The 6% Fe SiO2 nanocatalyst prepared via impregnation method resulted in relatively small and uniform dispersion of iron nanoparticles. However, bimodal distribution was observed for the 10 and 15% Fe SiO2. Similar trend was observed when Al2O3-SiO2 was used as a catalyst support. H2-TPR profiles for Fe SiO2 nanocatalysts synthesized via impregnation showed two reduction stages while those prepared using precipitation method resulted in three reduction peaks. The TPR peak positions remained the same for various iron loadings.
  R. Ahmed , C.M. Sinnathambi and D. Subbarao
  Kinetics of decoking of spent reforming catalyst has been studied using a Thermo Gravimetric Analyzer (TGA) in presence of N2 and air. It is found that the major portion of the coke species was hard coke which has activation energy equal to 86.3 kJ mol-1. Slow heating rate and appropriate temperature are monitored to optimize the de-Coking process. Fourier Transform Infrared spectroscopy (FTIR) analysis has been applied to study the structure of coke deposited on supported metal catalyst (soft coke).
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