Fixed bed column

If the solution were removed from Tank 1 and added to Tank 2, which also contained 1 eq of resin in the X ion form, the solution and resin phase would both contain 0.25 eq of Y ion and 0,75 eq of X ion. Repeating the procedure in a third and fourth tank would reduce the solution content of Y ions to 0.125 and 0.0625 eq. respectively. Despite an unfavorable resin preference. using a sufficient number of stages could reduce the concentration of Y ions in solution to any level desired. This analysis simplifies the column technique, but it does provide insights into the process dynamics. Separations are possible despite poor selectivity for the ion being removed. Most industrial applications of ion exchange use fixed-bed column... 

In the SMB operation, the countercurrent motion of fluid and solid is simulated with a discrete jump of injection and collection points in the same direction of the fluid phase. The SMB system is then a set of identical fixed-bed columns, connected in series. The transient SMB model equations are summarized below, with initial and boundary conditions, and the necessary mass balances at the nodes between each column. 

In fact, it is extremely difficult to operate a TMB because it involves circulation of a solid adsorbent. Thus, the concept must be implemented in a different way where the benefit of a true countercurrent operation can be achieved by using several fixed-bed columns in series with an appropriate shift of the injection and collection points between the columns. This is the SMB implementation as presented in Fig. 10.2. 

A further novel reduced-resin design is the ISEP from Advanced Separation Technologies, Inc. This employs a carousel holding 30 fixed bed columns of resin that continuously rotate to match 20 fixed top and bottom ports. This design also provides for high purity water and reduced regenerant demand and wash volumes, but at a significant capital cost. 

Regarding submerged plants, sorption of Cu(II) by Myriophyllum spicatum L. (Eurasian water milfoil) has been shown to be fast and fits isotherm models such as Langmuir, Temkin, and Redlich-Peterson. The maximum sorption capacity (c/lll l j ) of copper onto M. spicatum L. was 10.80 mg/g, while the overall sorption process was best described by the pseudo-second-order equation.115 Likewise, Hydrilla verticillata has been described as an excellent biosorbent for Cd(II). In batch conditions, the qmsx calculated was 15.0 mg/g. Additionally, II. verticillata biomass was capable of decreasing Cd(II) concentration from 10 to a value below the detection limit of 0.02 mg/L in continuous flow studies (fixed-bed column). It was also found that the Zn ions affected Cd(II) biosorption.116... 

In fixed bed columns (batch columns), the fluid and solid phase concentrations are functions of both position and time. Considering a conventional, idealized,... 

Gisi D, Stncki G, Hanselmann K W (1997) Biodegradation of the pesticide 4,6-dinitro-w//io-cresol by microorganisms in batch cultures and in fixed-bed column reactors, Applied Microbiology Biotechnology 48 441-448. 

Countercurrent gas-liquid flow in solid fixed-bed columns... 

For the normal arrangement in a fixed-bed column operating in countercurrent flow, the liquid is evenly distributed over the top of the packing, runs down over it in thin layers, films, rivulets, etc., and leaves at the bottom. The gas enters as a continuous phase at the bottom and leaves at the top. 

An offline measurement apparatus is usually not directly mounted on the reactor, but is fed with samples withdrawn from it manually or automatically. This is the typical case of chromatography, a widely used measurement device for gas and liquid composition. Both gas and liquid chromatographies are based on the separation of the sample by means of selective adsorption on a solid substrate posed in a fixed bed column, and on the detection of the change of a suitable property of the (gas or liquid) carrier, usually thermal conductivity. 

Focusing discussions on carbon adsorption processes, in a pulsed-bed adsorber, the carbon moves countercurrent to the liquid. The effect is of a number of stacked, fixed-bed columns operating in series. Spent carbon is removed from the bottom of... 

The study under pressure with countercurrent flow has shown that the operating pressure has no effect on hold-up. In fact for a liquid flow rate of 4.63 kg/rrPs and constant gas velocity of 0.037 m/s, liquid hold-up is 0.21 for pressure ranging between 0.1 and 1.3 MPa. This result is in agreement with the conclusions of Van Gelder el al. [1] concerning the influence of pressure on liquid hold-up in a packed column operating with cocurrent flow. Larachi el al. [4] report the same observations in a fixed bed column with cocurrent flow. 

The residence-time distribution in the liquid phase of a cocurrent-upflow fixed-bed column was measured at two different flow rates. The column diameter was 5.1 cm and the packing diameter was 0.38 cm. The bed void fraction was 0.354 and the mass flow rate was 50.4 g s l. The RTD data at two axial positions (which were 91 cm apart in Run 1 and 152 cm apart in Run 2) are summarized in Table 3-2. Using the method of moments, estimate the mean residence time and the Peclet number for these two runs. If one assumes that the backmixing characteristics are independent of the distance between two measuring points, what is the effect of gas flow rate on the mean residence time of liquid and the Peclet number Hovv does the measured and the predicted RTD at the downstream positions compare in both cases ... 

---