Gas-solid circulating fluidized beds (CFBs) are for carbon capture process because of their remarkable heat and mass transfer characteristics in the target reactor. Bed-to-wall heat transfer is an important issue in designing a reactor to satisfy the required conditions. Bed-to-wall heat transfer is characterized by near-wall particle behavior. Thus, in this study, local bed-to-wall heat transfer and near-wall particle dynamic characteristics were measured in a lab-scale CFB riser. The clustered particle behavior near the wall was investigated primarily using a non-intrusive method, particle-imaging velocimetry (Ply), within the CFB riser. To determine the effects of bed instability on the clustered particle behavior at the wall, bed instability was controlled. Bed instability was estimated by the degree of pressure fluctuation in the riser, and the fluctuation effect was compared, depending on the fluidization regime. Ultimately, the clustered particle behavior on the adjacent wall was compared depending on the pressure fluctuations using the Ply system. We estimated the clustered particle behavior on the adjacent wall of the CFB riser considering fluidization instability. Detailed analysis of the relationship between the bed-to-wall heat transfer and the particle behavior was conducted. (C) 2017 Elsevier Ltd. All rights reserved.