Effect of Twisted Tape Baffles on Pressure Drop, Fluctuation and Expansion Ratios in gas - Solid Fluidized Bed

In the present work an attempt has been made to study the effect of the twisted tapes as bed internals, on the performance of the gas-solid fluidized beds. Experimental investigation has been carried out in cylindrical column with and without twisted tapes. Twelve numbers of twisted tapes of three different widths with four values of the twist ratios for each width were studied at different static bed heights. Twist ratio (y) is the ratio of axial distance for 1800 rotation of the tape (H) and the width (W) of the twisted tape.  By using twisted tape the change in pressure drop, fluctuation ratio and expansion ratio have been studied as compared to “without twisted tape”. Incorporation of twisted tapes as baffle decreases the fluctuation ratio and expansion ratio thereby improving the fluidization quality as compared to the “without twisted tape”. However the increase in pressure drop due to presence of twisted tape is only marginal and of the order of, 5.25 to 14.9 percent over that of without twisted tapes. The maximum decrease in fluctuation ratio (r) for the tapes of various twist ratio has been found to be 11.6 to 20.5 percent based on the case of “without twisted tape”, thereby indicating a corresponding improvement in the quality of fluidization with reduced degree of bubbling and slugging. Quantitatively the maximum decrease in R for the twisted tapes of various twist ratios has been found to be 17 to 23 percent based on the case of “without twisted tapes”. However, the pressure drop, fluctuation and expansion ratio were in general found to decrease with decrease in twist ratio of a twisted tape. Different correlations have been developed for pressure drop, fluctuation ratio and expansion ratio and compared with their corresponding experimental values.