The effects of operating pressure and temperature on the flow behavior in the riser of a high-density circulating fluidized bed have been numerically studied using the two-fluid model coupled with the EMMS-based drag model. When the operating pressure is below 0.4 MPa, the flow regime in the riser experiences the fluid dominated (FD) zone, the transition zone from FD to the particle-fluid compromising (PFC), and the PFC zone with the increase of solids circulating flux. Under the same solids circulating flux, the solids axial velocity increases while the solids volume fraction decreases with the increase of operating pressure. In terms of axial profiles of solids volume fraction and axial velocity, there exists a critical operating pressure, above which the axial profile changes little with further increase of operating pressure, while it is hard to find a critical pressure in terms of radial profiles. When the gas density is kept the same, the increase of gas viscosity caused by higher temperature has only minor effect on the axial profiles of solids volume fraction, but it makes the solids axial velocity increase in the core zone and decrease slightly near the wall. (C) 2017 Elsevier B.V. All rights reserved.