Pressure fluctuation frequency characteristics in a spout-fluid bed by modem ARM power spectrum analysis

Pressure fluctuation frequency characteristics were investigated in a two-dimensional spout-fluid bed with its cross section of 300 mmx30 mm and height of 2000 mm. A multi-channel differential pressure sampling system was established to obtain pressure fluctuations and the modem ARM (Auto-Regressive Model) power spectrum was developed to estimate the pressure fluctuation major frequency. Effects of spouting gas velocity, fluidizing gas flow rate and static bed height on the pressure fluctuation major frequency were systematically examined. Differences of the major frequencies at various bed regions were analyzed. Experimental results show that the pressure fluctuation major frequency increases with increasing spouting gas velocity, while it decreases with increasing static bed height at any bed region; for Q(f/)Q(mf)<= 1.0, the major frequency at any bed region increases with increasing fluidizing gas flow rate; for Q(f/)Q(mf)> 1.0, the major frequency above the V-type distributor region decreases with increasing fluidizing gas flow rate, while the major frequency within the V-type distributor region increases all along with increasing fluidizing gas flow rate. In addition, a digital camera and a digital video were used to record the gas-solid two-phase interactions in bed. Preliminary investigation on the flow characteristics with the pressure fluctuation major frequencies indicates a promising way to study the complex gas-solid interactions and flow pattern transitions in spout-fluid beds. Some suggestions were also proposed for the operation of spout-fluid bed coal gasifiers. (c) 2005 Elsevier B.V All rights reserved.