A domestic scale fluidized bed dryer is designed, fabricated and used to measure the drying rates of wood chips and ground nuts at various operating conditions. Experiments were conducted at two different bed temperatures viz. 100C and 115C and also at three different fluidization velocities. The design was carried out using SOLIDWORKS and fabrication was done in a workshop using most basic processes. The purpose of keeping the cost of the facility was achieved. Different drying rates at different times, conditions, and materials were noticed. Drying times were lower for higher fluidization velocities and also at higher bed temperature. However, the influence of fluidization velocity is found to be greater than bed temperatures.
This paper presents a detailed review of experimental and modeling work carried out on devolatilization of different kinds of wood under fluidized bed combustion/pyrolysis conditions. Laboratory scale experimental studies as well as analytical, phenomenological and numerical modeling works have been reviewed and presented. It has been found that attempts to determine the kinetics in actual fluidized bed conditions have been carried out. There is no single devolatilization model that incorporates all the physical and chemical phenomena occurring during devolatilization. Moreover, the physical phenomenon of primary fragmentation has not been adequately incorporated in the models. Also, non-intrusive temperature measurement techniques need to be developed and demonstrated.
This work presents the results of experiments conducted to quantify primary fragmentation of wood (Casuarina Equisetifolia) during the devolatilization in a bubbling fluidized bed combustor. Cylindrical wood particles having five different sizes ranging from 10 to 30 mm and aspect ratio (l/d=1) have been used for the study. Experiments were conducted in a lab scale bubbling fluidized bed combustor having silica sand as the inert bed material and air as the fluidizing medium. Studies have been carried out at three different bed temperatures (Tbed=750, 850 and 950 °C), two inert bed material sizes (mean size dp=375 and 550 µm) and two fluidizing velocities (u=5umf and u=10umf). Limited experiments were also conducted at a bed temperature of 850 °C to study the influence of the presence of wood bark. Primary fragmentation was found to be most severe for larger sizes and at higher bed temperatures. Also, fragmentation did not show any conclusive influence on the devolatilization time.
Efficient drying of cereals, pulses and pellets in rural India has always been hindered in rainy seasons and during cloudy days. This can lead to wastage of agricultural products during storage in both farms and individual homes. We present the method of designing a Fluidized Bed Dryer for drying purposes. This simple and efficient system based on the fluidization process has been designed in SolidWorks software. The design has been thermally analyzed using Ansys. Stress analysis and flow simulation has also been carried out using Ansys. Our studies showed that the design can withstand the working conditions and hence a compact working model of the design was fabricated. Further tests and experiments can be conducted on the fabricated model for other uses including polishing and smoothening of rough particles for industry. We conclude that the design can effectively be used in for drying purpose both at domestic and industrial scale.