Process Intensification in a HIGEE with Split Packing

Abstract

Process intensification in rotating packed beds has attracted attention. The intensification is due to the large specific surface area of the packing and high liquid- and gas-side mass-transfer coefficients. Recent studies indicate that the slip velocity between the gas and the liquid in a rotating bed is in the same range as in conventional packed columns. Hence, the intensification is limited to a higher surface area of the packing if the resistance for mass transfer is on the gas side. To overcome this limitation, we proposed a rotating packed bed with split packing to promote the slip velocity as high as 30 m/s. To assess its efficacy, we have measured the mass-transfer coefficients on the gas side using the absorption of SO2 from air into aqueous NaOH solution and the one on the liquid side by the stripping of oxygen from water into nitrogen. The volumetric mass-transfer coefficients on the gas side and the liquid side, respectively, were in the ranges 35−280× and 25−250× compared to those of packed columns. Correlations for the local mass-transfer coefficients have been presented. The studies indicate a volume reduction of the units by 2 orders of magnitude is feasible.

Mass transfer characteristics in a rotating packed bed with split packing

“…4 plots the increase of a e and k y a e along with the gas velocity. The tendency of experimental data is in agreement with Reddy et al [16] and Rajan et al [22], a e and k y a e for counter-rotation are larger than those for co-rotation. This phenomenon may be explained by 1 84 116 2 132 164 3 182 214 4 230 262 5 280 312 6 328 360 the deduction that with the increasing gas velocity, the radial velocity at the inner periphery of the packing rings increase, it may lead to a stronger disturbance of gas-liquid phases and a better dispersion of the liquid, which result in an increase in k y a e and a e [23].…”

“…This phenomenon may be explained by 1 84 116 2 132 164 3 182 214 4 230 262 5 280 312 6 328 360 the deduction that with the increasing gas velocity, the radial velocity at the inner periphery of the packing rings increase, it may lead to a stronger disturbance of gas-liquid phases and a better dispersion of the liquid, which result in an increase in k y a e and a e [23]. When the two adjacent rings rotate in opposite directions, a larger tangential slip velocity between the gas and packing and a better liquid distribution onto the packing rings are obtained than those in corotation mode, which are beneficial to the mass transfer process [16,22].…”

“…This may be explained by the fact that with the increasing the rotational speed, the shearing force imposed on the liquid by the packing enhances, causing better liquid distribution onto the packing rings [23]. When the two adjacent rings rotate in opposite direction, a larger gas-liquid turbulence and tangential slip velocity are obtained than those of co-rotation [16,22], which lead to enlarge the relative velocity between gas and liquid and the contact area of gas-liquid [20,21], these factors are conducive to the mass transfer process. Fig.…”

“…For example, Reddy et al [16] measured the gas volumetric mass transfer coefficients (k y a e ) using the SO 2 -NaOH absorption system in a split packing RPB, and the results show that gas volumetric mass transfer coefficients are 2 orders of magnitude higher than those reported with a single packing [13,17]. Shivhare et al [18] determined the gasside mass transfer coefficient (k y ) via absorption of SO 2 in aqueous NaOH in the split-packing and conventional single-block RPB, and the results indicate that split-packing RPB was superior to conventional single-block RPB for gas-side mass transfer resistance controlled processes.…”

Computational Study of a Rotating Packed Bed Distillation Column

“…Emphasizing that Aspen PLUS only have available correlations of individual mass transfer coefficient for conventional packed columns, this work introduced correlations (using computational subroutine written in Fortran 11.0) for the liquid phase and vapour Rajan (2008) and Reddy et al (2006), respectively, for a HIGEE column (Table 1). Emphasizing that Aspen PLUS only have available correlations of individual mass transfer coefficient for conventional packed columns, this work introduced correlations (using computational subroutine written in Fortran 11.0) for the liquid phase and vapour Rajan (2008) and Reddy et al (2006), respectively, for a HIGEE column (Table 1).…”