Biomass Pyrolysis in a Fluidized Bed Reactor. Part 2: Experimental Validation of Model Results Xiaoquan Wang, Sascha R. A. Kersten,* Wolter Prins, and Wim P. M. van Swaaij Department of Chemical Technology, Faculty of Science and Technology, University of Twente, Postbus 217, 7500AE Enschede, The Netherlands Various types of cylindrical biomass particles (pine, beech, bamboo, demolition wood) have been pyrolyzed in a batch-wise operated fluid bed laboratory setup. Conversion times, product yields, and product compositions were measured as a function of the particle size (0.7-17 mm), the vapor’s residence time (0.25-6 s), the position of the biomass particles in the bed (dense bed or splash zone), and the fluid bed temperature (250-800 °C). For pyrolysis temperatures between 450 and 550 °C, the bio-oil yield appeared to be maximal (in this work: about 65 wt %), while the water content of the bio-oil is minimal. The position of the biomass particles in the fluid bed, either in the dense bed or in the splash zone, does not affect the conversion time and product yields to a large extent during pyrolysis at 500 °C. In the small fluid bed used for this work, with a char hold-up of up to 5 vol % (or 0.7 wt %), the residence time of the pyrolysis vapors is not that critical. At typical fast pyrolysis temperatures of around 500 °C, it appeared sufficient to keep this residence time below 5 s to prevent significant secondary cracking of the produced vapors to noncondensable gas. Up to a diameter of 17 mm, the particle size has only a minor effect on the total liquid yield. However, for particles larger than 3 mm, the water content of the produced bio-oil increases significantly. The experimental results are further compared with predictions from a one-dimensional (1D) and a two-dimensional (2D) single-particle pyrolysis model. Such models appeared to have a limited predictive power due to large uncertainties in the kinetics and selectivity of the biomass decomposition. Moreover, the product quality cannot be predicted at all. 1. Introduction The first part 1 of this work was concerned with the literature review on biomass pyrolysis and pyrolysis modeling for the purpose of reactor design. In this companion paper, experimental results of lab-scale fluidized bed pyrolysis will be presented. The following parameters have been varied: the type of wood (beech, pine, bamboo, palletized demolition wood), the reactor temperature (250-800 °C), the particle size (0.7-17 mm), the vapor residence time in the gas phase (0.25-6 s), and the position of the biomass particles in the reactor (freeboard, splash zone, dense bed). Experimen- tal results are compared with predictions of existing single particle models as described in the first part 1 of this research report. On the basis of this comparison, the predictive potential, and the minimal level of modeling detail still giving sufficient accuracy for reac- tor design calculations, will be established. The signifi- cance of the presented work with respect to the design of a (fluid bed type) reactor for the pyrolysis of wood particles is discussed. 2. Experimental Equipment and Procedure Fluidized bed pyrolysis of cylindrical wood particles has been carried out at ambient pressure and tem- peratures in the range of 250-800 °C. These particles were made from beech, pine, bamboo, or demolition wood, and their diameters were varied from 1.5 to 17 mm while keeping their length constant at 42 mm. In addition to these cylindrical particles, saw dust with an average diameter of 0.7 mm has been used. Other particle properties relevant for the interpretation of the experimental results are listed in Table 1. Figure 1 shows a sketch of the experimental setup. The fluidized bed reactor was made of stainless steel and placed in an electric furnace for independent temperature con- trol. A 45 mm long cylindrical bottom section (26 mm internal diameter) was connected with a 90 mm long wider top section (60 mm internal diameter) by a coni- cal part with a height of 125 mm. The incoming gas (nitrogen) was preheated by passing it through a 400 mm long heating tube (10 mm internal diameter) coiled around the fluid bed reactor. A sintered metal plate underneath the bottom section served as a gas distributor. Silica sand with an averaged particle diameter (d 50 ) of 258 μm was used as a fluidized bed material. Its minimum fluidizing velocity at room temperature and ambient pressure was found to be 0.032 m/s. The fluidized bed temperature was recorded continuously by a submerged chromel-alumel thermocouple. Two sequential condensers, immersed in containers with iced water and dry ice/ethanol mixtures, respec- tively, were used to collect the pyrolysis liquid. Most of the pyrolysis vapors (80-90 wt %) coming from the fluidized bed reactor could be collected in the first copper-coil condenser where they were quenched to 5 °C. Low boiling point fractions were accumulated in the second washing bottle condenser in which temperatures down to -79 °C could be reached. Online infrared and TCD analyzers of Hartman and Braun (made in Ger- many), protected by additional paper filters, were used to measure the concentration of four main components * To whom correspondence should be addressed. Tel.: 31-53-489-4430. Fax: 31-53-489-4738. E-mail: s.kersten@ utwente.nl. 8786 Ind. Eng. Chem. Res. 2005, 44, 8786-8795 10.1021/ie050486y CCC: $30.25 © 2005 American Chemical Society Published on Web 10/11/2005