Executive Summary : | The increasing energy demand and depleting petroleum sources have led to renewed interest in biomass–derived syngas as alternative feedstock to produce clean energy and value-added chemicals. Among various Gas-to-Liquid (GtL) technologies, methanol/ DME synthesis via catalytic hydrogenation of syngas is one of the most emerging industrial technologies to produce hydrocarbon fuels and chemicals using syngas derived from coal and biomass gasification. In the process a mixture of H2 and CO at high temperature and pressure is used for the synthesis of longer chains of hydrocarbons, in the presence of a fine solid catalyst. The reaction is exothermic, and hence the excess heat generated is removed by using an internal heat exchanging system, e.g., water tubes, jacketed vessels or cooling coils/ tubes. Different reactor configurations have been employed, such as the fixed and fluidized bed reactors were conventionally used, while three-phase slurry bubble column reactors (SBCR) are applied in the latest liquid-phase methanol (LPMeOH) processes. SBCR has gained increasing popularity due to the advantages of handling large volumes and providing a high interface area and heat and mass transfer characteristics, with the addition and removal facilities of catalysts during the process. However, the gas-liquid and liquid-solid interactions and their impact on small and large size bubbles make the hydrodynamics of such SBCRs very complicated. The heat and mass transfer characteristics involved in SBCRs are significantly affected by the bubble dynamics, viscous slurry properties, and the design of the internals (i.e. heat exchanging tubes, gas distributor, etc.). However, up-to-date knowledge of the impact of liquid-solid (viscous) medium and the internal heat-exchange system on bubble properties, and heat and mass transfer characteristics in a three-phase SBCRs is sparse. Therefore, it is important to understand and quantify the role of liquid/ slurry rheology (density/ viscosity) and internals on the gas-phase dynamics and heat and mass transfer characteristics in an SBCR to develop their design for scale-up in industrial applications. Not only, experimental characterization but computational modeling of such SBCR with adequate interphase momentum exchange model and with appropriate bubble sizes based on coalescence and breakup behavior, is very challenging to perform. The CFD models to include the effects of viscous slurry properties, and bubble size distribution on local and overall gas holdup and the resultant heat and mass transfer coefficients are also not readily available. Therefore, the primary objective of this proposed research work is focused on the experimental and computational investigations of the effect of the viscous slurry properties, and bubble size distribution on gas phase dynamics and heat and mass transport in SBCR equipped with mimicked internal heat exchange system involved in methanol/ DME synthesis using biomass-derived syngas. |