Effect of biomass blending on hydrodynamics and heat transfer behavior in a pressurized circulating fluidized bed unit

The hydrodynamic and heat transfer characteristics at four different % mixing of biomass in sand (2.5%, 7.5%, 12.5% and 20%) have been investigated in a pressurized circulating fluidized bed. Experiments were performed at three superficial velocities of 6, 7 and 8 m/s. In each superficial velocity, experiments were conducted at three different system pressures of 1, 3 and 5 bar. Effects of recirculation rate have also been studied. The heat transfer characteristics have been studied at the upper splash region of the riser. Particle sizes of sand and biomass considered in the present study are 309 μm and 407 μm, respectively. From the study, it has been observed that, the heat transfer coefficient increases along the heat transfer probe and decreases with an increase in percentage blending of biomass in sand. Higher pressure and higher superficial velocity is found favorable for achieving a higher heat transfer coefficient. With increase in pressure, the heat transfer coefficient is found to be increasing with blending of biomass up to 12.5%, and then decreases as superficial velocity decreases. The heat transfer coefficient is also found to be increasing with increase in suspension density and operating pressure. Biomass blending of 12.5% in sand and a pressure of 5 bar are found to be the optimum to achieve a maximum wall to bed heat transfer coefficient and uniform circulation rate.