Influence of hydrodynamic parameters on particle attrition during fluidization at high temperature

Abstract

In a fluidized bed, attrition both increases the number of particles and reduces particle size, which may affect reactor performance; fluidizing properties, operating stability and operating costs. Most fluidized applications are conducted at high temperature, but in the past most attrition correlations were performed at room temperature, so the attrition rate at high temperature could not be predicted. In contrast, this study investigates the attrition rate of fluidized materials at high temperature. Silica sand was used as the bed material; the operating parameters included temperature, particle size, static bed height and gas velocity to assess the attrition rate. Then an appropriate correlation was developed by regression analysis to predict attrition rate at high temperature. Experimental results indicated that the attrition rate increases with increasing temperature. In addition, the particle attrition increased as average particle size decreased because the probability of collision increases with surface area. The attrition rate increased with increasing gas velocity because of increased kinetic stress of particle movement. The actual density and viscosity of air at specific fluidization temperature were modified and an Ar number was introduced to fit our experimental data. The experimental correction agrees with the experimental results, which can predict particle attrition rate at high temperatures

Influence of Temperature on Fluidized‐Bed Catalyst Attrition Behavior

“…Chen et al [36][37][38] investigated the attrition of limestone by impact tests in a circulating fluidized-bed combustor at temperatures from 25°C to 850°C. They stated that the attrition decreased with increasing temperature, which is in contrast to the findings of Lin and Wey [34,35]. The attrition of calciumbased sorbents for removing sulfur dioxide (limestone, dolomite, lime etc.)…”

“…They concluded that attrition of the F-T catalyst was induced by both the mechanical stress from particles' collisions and the chemical stress due to phase transformation. Lin and Wey [34,35] studied the attrition of silica sand at high temperature in a bubble fluidized-bed incinerator. They found that prediction results from existing correlations derived at room temperature could not coincide with their experimental results achieved at high temperatures, whereas the attrition rate increased with higher temperature.…”

Study of limestone particle impact attrition

“…Removal of product (CaSO 4 ) layer by attrition decreased the diffusion resistance of SO 2 , thereby increasing the reaction rate and limestone conversion. Lin and Wey (2005) found that the rate of attrition of silica sand in a bubbling fluidized-bed at 850 • C increased with increasing temperature (at the same air flow), decreasing particle size and increasing gas velocity.…”

A stepwise process for carbon dioxide sequestration using magnesium silicates

“…Lin and Wey [14] on the other hand, studied the attrition of silica sand and found that attrition instead increased with increasing temperature because particles move faster at higher temperatures with the same airflow. Considering these two studies, increasing the temperature and using sand as a fluidisation medium could also have negative effects on Mg(OH) 2 carbonation.…”