experimental study on fluidization of biomass-sand … · for the studied biomass-sand mixtures 4....
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1. INTRODUCTION
The application of biomass in power generation processes such as the
combustion, pyrolysis and gasification, operating with fluidized bed
technology, has received increasing attention in recent decades. Among
the biomass with potential for sustainable power generation is the
bamboo, that presents properties similar to other biomass applied in
energy generation processes, with the advantage of rapid growth, easy
propagation, vigorous regeneration and quick maturity [LONDOÑO, 1998;
SCURLOCK, 2000; PEREIRA E BERALDO, 2007].
The objective of this work is to study the hydrodynamics behavior of
mixtures of particles composed by sand and bamboo (in natura and in the
form of coal from the pyrolysis process) aimed at obtaining parameters
inherent to fluidization of these mixtures, as well as to analyze the effect of
thermal degradation on bamboo particles fluidization.
2. MATERIALS AND METHODS
Bamboo D. giganteus Munro stems (approximately 5-year old) harvested
at University of Campinas in Brazil were air-dried and ground to obtain
particles smaller than 12 Mesh. The bio-coal was obtained from a slow
pyrolysis process at 500 oC. Five sizes of sand particles were tested
named sand 1 (231 µm) to sand 5 (920 µm). Table 1 shows the physical
properties of biomass and sand particles: mean particle diameter (dp),
particle density (ρp), bulk density (ρm), bed porosity (m), minimum
fluidizing velocity (Umf) and Geldart’s classification of each material. Tests
were performed for binary mixtures composed by 5 %wt of biomass
particles and 95 %wt of sand particles. Three heights of the static bed (H)
were tested: 0.10; 0.15 and 0.20 m. Bed pressure drop measurements
were made in the experimental system shown in Fig. 1, from the bubbling
fluidized bed regime to the fixed bed regime by reducing the gas flow
through the bed. Three replications of the tests for each material were
performed.
Table 1. The physical characteristics of the material
nf = bubbling fluidizing regime not observed
Regarding the fluidization process of bamboo in natura and coal (without
the presence of sand particles), the bubbling fluidizing regime was not
observed due to the agglomeration of the biomass particles reaching the
slugging flow regime as the air flow was increased (Fig. 2).
Figure 2: Slugging bed for (a) bamboo
particles e (b) bamboo pyrolytic coal .
Figure 1: Experimental system.
3. RESULTS AND DISCUSSION
The experimental determinations of Umf, Ufi (onset fluidization) and Ucf
(complete fluidization) were based on the analysis of the hydrodynamics
curves of bed pressure drop (ΔPbed) versus superficial gas velocity (U0),
Figs. 3 and 4.
Figure 3: Hydrodynamics curves for the studied sand particles and
mixtures composed by 5 %wt bamboo and 95 %wt sand (H = 0.1 m).
.
Figure 4 Hydrodynamics curves for three static bed heights (binary
mixture: 5 %wt bamboo and 95 %wt sand 3).
Table 4: Results of 𝑈𝑚𝑓, 𝑈𝑓i and 𝑈𝑓c for the studied biomass-sand mixtures
4. CONCLUSIONS
Particles of bamboo and bamboo coal present a tendency to
agglomeration showing the slugging fluidization regime if a large amount
of sand particles was not added in the bed. The experimental tests using
bamboo (5 %wt) – sand (95 %wt) mixtures allowed the determination of
important velocities that characterize the fluidization processes of binary
mixtures as a function of sand size and static bed height. The best quality
of bamboo-sand fluidization was obtained using sand particles 460 µm
diameter and 0.10 m static bed height.
REFERENCES LONDOÑO, XIMENA. Evaluation of bamboo resources in Latin America. A
Summary of the Final Report of Project No. 96-8300-01-4, Internatinoal
Network for Bamboo and Rattan, Cali, Colombia, 1998.
PEREIRA, M. A. R.; BERALDO, A. L. Bambu de corpo e alma. Canal 6,
projetos editoriais, p. 240. Bauru, São Paulo, Brasil, 2007.
SCURLOCK, J. M. O. Bamboo: an overlooked biomass resource? Biomass
and Bioenergy, v. 19, p. 229–244, 2000.
EXPERIMENTAL STUDY ON FLUIDIZATION OF
BIOMASS-SAND MIXTURES D. A. RAMIREZ-QUINTERO* and A.A.B.PÉCORA
University of Campinas, School of Mechanical Engineering, Campinas, Brazil.
*Corresponding author: [email protected], +55 (19) 9970-45616