要約

Pressurized circulating fluidized bed (PCFB) is mostly subjected to the variations in hydrodynamics and heat transfer due to the fluctuations in demand in utilities. Therefore investigation of transient heat transfer and hydrodynamics in PCFB becomes critical. Transient heating and cooling also occur in PCFB during the startup and shutdown process. However the behavior of PCFB during these transient periods is not fully understood in spite of its high significance.

The present work includes experimental investigation of the transient behavior of a PCFB unit. The riser of the PCFB in this study is fabricated with stainless steel pipe of height 2 m, an inner diameter of 50 mm and wall thickness of 3 mm. The upper splash region is considered as a test section for the study which is heated electrically with a heater coil attached to an electrical circuit to study the heat transfer characteristics. K- type thermocouples are used to measure the surface and bed temperatures. The locations of the thermocouples from the distributor plate are 1.4m, 1.5m, 1.6m, 1.7m and 1.8m. Fluidizing air is supplied by a high pressure compressor. The air flow rate is regulated by an airflow control valve and is measured using a rotameter and a orifice plate. Static pressures are measured along the riser column at heights of 13cm, 25cm, 49.5cm, 69.5cm, 91.5cm, 118cm, 142cm, and 176cm respectively. Fine wire mesh (BS 400) and filters are used at the pressure tapings to minimize pressure fluctuations and prevent leakage of sand. Pressure drops are measured using piezo resistive type pressure transducers.