This work is a part of the development and study of a fluidized-bed combustor with a cone-shape bed (referred to as ‘conical FBC’) using quartz sand as the inert bed material. Generally, in shallow conical beds, solid particles of 1-mm size or coarser (i.e., belonging to the group-D of the Geldart classification [13]) are fluidized in the spouting fluidization mode for wide ranges of cone angle and static bed height [14] and [15]. However, at the cone angle of about 40°, Geldart-D particles with relatively small size (e.g., 1–2 mm) may exhibit the bubbling fluidization regime [15]. As revealed by the studies on fluidization in conical air–sand beds with cone angles of 30–60°, the particles of 180–1180 μm sieve size (i.e., Geldart-B and Geldart-D groups) and 20–40 cm static bed height are basically fluidized in the bubbling fluidization regime [16], which, compared to the spouting fluidization mode, is more preferable for the fluidized-bed combustion system [1] and [17].