The combined feeding of coal and air to a cold model fluidized bed using valve caps

A study has been conducted to test the concept of using a valve cap as a fluidization and coal feeding device for an atmospheric fluidized bed combustor. The investigation was considered necessary due to problems encountered with systems currently in use. The study required the design and construction of a cold (ambient temperature) test facility which can be used for future testing of different types of fluidization and coal feeding devices.

The investigation is limited in scope since the tests were conducted at ambient conditions instead of the hot conditions of an operating bed. Comparisons made to a multi-orifice grid plate show several distinct advantages of the valve cap feeder system including type of flow, type of mixing, bed pressure oscillations and overall pressure drop. Equations have been developed from experimental results to predict the pressure drops encountered with a valve cap feeder when used as a fluidization device. The valve cap feeder was able to distribute imitation "coal" as well as single point injection using a multi-orifice grid plate as a fluidization device. The valve cap feeder creates distinct circulation patterns which may aid in sorbent utilization and temperature distribution.