Published: August 15, 2011 r2011 American Chemical Society 4077 dx.doi.org/10.1021/ef200635v | Energy Fuels 2011, 25, 4077–4084 ARTICLE pubs.acs.org/EF Numerical Study on the Hydrodynamics of a Self-Heating Biomass Fast Pyrolysis Reactor Huiyan Zhang, Shanshan Shao, Rui Xiao,* Qiwen Pan, Ran Chen, and Jubing Zhang School of Energy and Environment, Southeast University, Nanjing 210096, People’s Republic of China ABSTRACT: A novel, self-heating biomass fast pyrolysis reactor named internally interconnected fluidized beds (IIFB) was proposed for the efficient production of bio-oils and chemicals by catalytic fast pyrolysis of biomass. The IIFB reactor mainly consisted of a pyrolysis bed (biomass pyrolysis) and a combustion bed (char burning and catalyst regeneration) connecting through a draft tube and a dipleg. Each bed was designed for the continuous operation. The hydrodynamic characteristics of the reactor, such as solid circulation rate, pressure distribution, and volume fraction of particles were performed using numerical simulation in this study. A non-steady-state, Eulerian multi-fluid model was used. The gas phase is modeled with a kε turbulent model, and the particle phase is modeled with the kinetic theory of granular flow. The experiments were carried out in an IIFB experimental system to verify the model. The simulation results show that the solid circulation rate was kept as a constant of 110 kg/h after 12 s of computational time compared to the value of 104.5 kg/h obtained in the experiments. The time-averaged values of the pressures at different positions after 12 s of computational time were also close to the experimental data. The particles in the dipleg were monitored to drop downward at a uniform speed of 0.07 m/s. In comparison to that in the draft tube, the velocity magnitude (including vertical or horizontal directions) of the particles decreased along the height of the draft tube, whereas the vertical velocity of the particles first underwent a disturbed flow because of the solidsolid and solidwall collisions, then increased rapidly, and last were kept at an almost uniform magnitude. The results can provide a conceptual guide for designing, building, and operating the system of biomass (catalytic) fast pyrolysis. 1. INTRODUCTION The shortage of fossil fuels, especially petroleum resources, is stimulating the interest to search for renewable energy to sub- stitute for traditional fuels. 13 Lignocellulosic biomass is the most abundant and the renewable source of carbon, which can be converted into liquid fuels and chemicals. 4,5 However, biomass is a low-energy-density resource compared to fossil fuels, which make transportation, storage, and handling more costly per unit of energy. 6 Biomass fast pyrolysis (BFP) can convert biomass to considerable liquid fuel, named as bio-oil, which can reduce transport cost up to 87%. BFP is a simple and inexpensive technology for biomass conversion. 7 It has been shown to be 23 times cheaper than biomass conversion technologies based on gasification and fermentation processes. 8 During the last 20 years, several types of reactors, e.g., fluidized beds, transported and circulation fluidized beds, spouted beds, and ablative and vacuum pyrolysers, have been developed for the BFP process. 916 The pyrolysis process is an endothermic reaction; heat is required for biomass pyrolysis. To increase the economic potential of BFP, pyrolysis char is usually combusted to serve the heat needed in the process. Recently, BFP with catalysts, called catalytic fast pyrolysis (CFP), has attracted numerous interests because of the versatility and potential of sustainable production of liquid fuels and chemicals. However, the catalysts are deactivated obviously and need to be regener- ated in a regeneration bed. 1724 Externally interconnected fluidized beds (EIFB) reactor has been used for the BFP process and catalyst regeneration. 12,25 The char, catalyst, and sand are separated from pyrolysis gas by the cyclone separator and sent back into the combustion bed. However, it requires a high separating efficiency of the cyclone separator or more cyclone separators. 26 Furthermore, the solid circulation between the pyrolysis bed and combustion bed is difficult to control. To overcome these problems, we proposed a novel reactor, internal interconnected fluidized beds (IIFB). The IIFB reactor can realize a three-in-one process: CFP of biomass, regenera- tion of catalyst, and energy reduction by direct heat transfer. Its configuration and working principle are shown in Figure 1. The IIFB reactor has two beds, i.e., a pyrolysis bed (the draft tube and fountain region) and a combustion bed (the annulus), separated by a draft tube and conical dipleg. Mass and heat are transferred through slots at the bottom of the draft tube. Biomass is fed into the draft tube with N 2 or noncondensable gas produced from biomass pyrolysis through the bottom of the reactor. Hot particles (sand/catalyst/their mixture) are intro- duced into the draft tube from the combustion bed through the slots. The bed materials transfer heat rapidly to biomass, increase the temperature, and lead to (catalytic) fast pyrolysis in the draft tube. In the fountain region, char and bed materials separate from pyrolysis vapors because of their gravity, fall into the dipleg, and then slip into the combustion bed. Some small particles that are blown out of the pyrolysis bed are captured by a cyclone and recycled into the combustion bed. In the combustion bed, the high carbon-containing char is combusted and releases heat to the bed materials. The heated bed materials in the combustion bed are entrained into the draft tube again. Received: April 24, 2011 Revised: August 14, 2011