Particle Residence Time and Particle Mixing in a Scaled Internal Circulating Fluidized Bed

Abstract

A process is under development for the steam gasification of biomass to produce a hydrogenrich gas for use with a fuel cell to generate electricity on a local scale. A pilot plant is currently under construction in southern Italy operated with a circulating fluidized bed, and to predict the fluid dynamic conditions within the plant, a cold laboratory rig was built according to existing scaling laws, and experimental studies were carried out. In this paper, we present the experimental results concerning the solids residence time of particles introduced into the system and the particle mixing in the "gasifier" section of the model. Both parameters are of fundamental importance for the operation of the pilot plant as they determine the performance of the gasification process. It is shown that the biomass particles spend sufficient time in the gasifier to be fully gasified, and an equation is derived to predict the mean residence time of the biomass particles as a function of the dimensionless mass turnover of the circulating bed material. In addition, it is shown that the biomass particles are well mixed within the circulating bed material. One reason for this is a result of the geometric design of the apparatus.

Comparative scaling analysis of two different sized pilot-scale fluidized bed reactors operating with biomass substrates

“…The larger reactor shows undoubtedly higher mixing performance than the smaller unit. The gas velocity influence on mixing and segregation results are consistent with previous information drawn from the volume fraction distribution along the bed height profiles, the mean volume fraction contours, and the current literature [36].…”

Detailed Modeling of Biomass Gasification in Dual Fluidized Bed Reactors under Aspen Plus

“…It is a useful tool to improve prediction of reactor behavior and gas composition with basic assumption of ideal hydrodynamics. Biomass particle residence time is most of the time long enough in LVFB to achieve a complete pyrolysis. ,− Consequently, the apparent rate of pyrolysis, which depends on a complex coupling among bed hydrodynamic, external and internal (inside the particle) heat transfers, and intrinsic pyrolysis chemical kinetic, does not need to be modeled for our purpose (modeling of product composition under Aspen). Pyrolysis is assumed to be complete and to occur in a perfectly stirred reactor (PSR) inside the solid bed material.…”

Discrete element study of solid circulating and resident behaviors in an internally circulating fluidized bed

“…By introducing different gas flow rates into these different chambers, the internal circulation of solid phase is established in the system. Compared with other fluidizing apparatuses, the ICFB exhibits many favorable advantages in the practical application, such as the reduced height and construction cost, the nice process identification, comparatively small heat loss from the system, high conservation transfer efficiency and a wide range of load control, and so on [5,6]. Thus, it has been utilized in many industrial processes, such as catalytic coal gasification [7,8], the thermal treatment of industrial solid wastes [9,10], desulfurization [11], combustion of liquid bio-fuels [12], biomass pyrolysis and gasification [13,14].…”