experimental study on fluidization of biomass-sand … · for the studied biomass-sand mixtures 4....

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: deyber@fem.unicamp.br, +55 (19) 9970-45616