Estimation of the overall mass flux in inclined standpipes by means of pressure fluctuation measurements

The mass and heat balances in circulating fluidized bed systems strongly depend on the overall solids flux recirculated, making it necessary to estimate or measure this flux. Many methods have been reported in literature to continuously monitor the solids flux, with the curve solids flux Gs vs. pressure drop in the riser ΔPriser as one of the most used approaches. In this work, we show that in a circulating fluidized bed equipped with an inclined standpipe the whole mass flux is well correlated with the standard deviation of the pressure fluctuations in the standpipe. Contrary to the correlation Gs vs. ΔPriser, our correlation results to be virtually independent of the superficial gas velocity in the riser in the range 3.1–7.5 m/s. This makes it applicable for the on-line monitoring of the solids flux in a broad range of superficial gas velocities. Moreover, it has been shown that from the data Gs vs. standard deviation it is possible to estimate the maximum solids flux achievable by the unit. From this information, we can know at which fraction of the maximum mass flux the circulating fluidized bed is operating.

► We have measured pressure fluctuations in the inclined standpipe of a CFB.
► The standard deviation of the pressure fluctuations is related with the solids flux.
► This relationship is not affected by the air velocity in the riser or the aeration.
► This relationship can be used for the on-line monitoring of the solids flux.
► This relationship gives the saturation capacity of the standpipe.