An enormous amount of heat energy is available in the cyclone and downcomer of a circulating fluidized bed (CFB). The downcomer section can thus be a major source of heat recovery. There is scope for investigation on prospects of recovering heat along the downcomer. In the present work, an attempt is made to utilize the heat from the downcomer of a laboratory-scale Pressurized circulating fluidized bed (PCFB) set up by incorporating a spiral type of heat exchanger inside it. Transient behaviour of the heat recovery for various transient operating conditions such as superficial air velocity and power input which are operated under either step and ramp increase or decrease are reported. The PCFB unit in the present study consists of a riser of 2000 mm height and 54 mm inner diameter. The length of the downcomer is 1465 mm with an inner diameter of 54 mm. The results indicated that a maximum amount of around 350 W of heat could be recovered in the downcomer. It is also observed in some cases that this heat recovery fluctuates in phase with the transients in various operating conditions while it fluctuates with delays and phase shifts in others.

循环流化床（CFB）的旋风分离器和降液管中提供了大量的热能。降液管部分因此可以是热回收的主要来源。对于沿降液管回收热量的前景存在研究范围。在当前的工作中，试图利用来自实验室规模的加压循环流化床（PCFB）的降液管的热量，该流化床是通过在其内部结合螺旋型热交换器而建立的。报告了在各种瞬态运行条件下的热回收的瞬态行为，这些瞬态运行条件是在阶跃和斜率增大或减小下操作的表观空气速度和功率输入。本研究中的PCFB单元由高度为2000毫米，内径为54毫米的立管组成。降液管的长度为1465毫米，内径为54毫米。结果表明，降液管中最多可回收约350 W的热量。在某些情况下，还可以观察到，这种热回收在各种工况下都与瞬变同相波动，而在另一些情况下，则随着延迟和相移而波动。