Desorption column

The reactive distillation column was not a distillation column, but a desorption column, as in a distillation column the liquid phase must boil. 

The isobutane dissolved in the liquid stream drawn off from the reactors is also recovered at the top of a distillation column, at 0.15.10 Pa absolute (15 trays). The oxygenated compounds obtained at the bottom of this third column and of the desorption column are then fractionated (10 trays) at pressure less than 0.5. I06 Pa absolute. The distillate, consisting of solvent, residual isobutaoe. and a little r-butyl alcohol, is sent to the desorption stage. The drawn-off stream essentially contains hydroperoxide and r-butanoL ... 

Calculate the volume of packing required for the desorption column. V apor-liquid equilibrium data from Example 16.4 can be used and KaO = 4 Ibmole/hr ft atm (partial pressure). 

Acetylene recovered by the absorption process is reused for lithium acetylide production in stage I of the process. For this, the acetylene-containing ammonia from the central ammonia-acetylene buffer tank is fed into a desorption column where the acetylene is driven off from the ammonia by heating and is obtained as overhead product. Ammonia from the bottom of the column is reused for dissolving metallic lithium or absorbing acetylene. 

The refrigeration process uses compressors and an expander system. The proximity of the refrigeration machinery enables the compressed hot ammonia to be used as a source of heat in the etinol plant. Thus, the acetylene desorption column used to drive off dissolved aratylene is heated by waste heat from the refrigeration machines. Only the excess heat is removed by a cooling tower, and this requires a minimum amount of cooling water. 

These results show that reasonable designs for adsorption and desorption columns can be used to provide high levels of CO2 removal. Removal of CO2 does not remove significant quantities of valuable components (H2, CH4 and CO). The product gas streams are high purity CO2 (when a reboiler is used) or CO2/CH4 mixtures when CH4 is used as a stripping gas. The recovered CO2, either as a neat stream or as a CO2/CH4 mixture, can be fed to the syngas generator. 

This section discusses a solvent recovery process developed by Kureha Engineering Co. Ltd., Japan. In this continuous process, spherical particles of activated carbon (AC) circulate in the adsorption and desorption columns by fluidization. In the adsorption column, the particles form fluidized beds on multi-trays to adsorb the solvent in counter-current contact with the feed gas. The cleaned gas is released from the top of the adsorption-column to the atmosphere. 

The carbon absorber with adsorbed solvent is electrically heated (150-250°C) at the upper part of the desorption column and solvent is desorbed by nitrogen, whieh is supplied from the bottom of the desorption column. Nitrogen is eontinuously reeyeled in the desorption column. The solvent in the carrier gas is fed to a condenser for its reeovery. Features of the process ... 

The occurence of the complete adsorption of macromolecules forms a base of the full adsorption-desorption liquid chromatography-like separation method, FAD (Berek and Nguyen, 1998). A very weak mobile phase is employed, which acts as an adsorb for n-1 sample constituents. They are completely retained within the appropriate full adsorption-desorption column packed with nonporous particles. The unretained sample constituent is directly forwarded to an online SEC column for its molecular characterization. In the next stage, eluent strength is stepwise increased and sample constituents are successively one-by-one desorbed and forwarded into the SEC column. Successful separation of up to six distinct polymers with help of FAD method was reported. In the FAD method, solvents are chosen so that they always act as a desorb just for one sample constituent. 

The following discussion of the pressure drop in counterflow columns which is applied to rectification columns is also valid for absorption and desorption columns. 

FIGURE 8.7 Computer graphics visualizations of various stages of adsorption and desorption in an open-ended slit geometry. The adsorption column corresponds to a sequence of increasing pressures (from top to bottom) the desorption column corresponds to a sequence of decreasing pressures (from top to bottom). (Adapted from Sarkisov, L. and Monson, P. A., Langmuir, 17 7600, 2001. With permission.)... 

The concentration profiles of the regeneration (desorption) column at different times are shown in Fig. 6.18. 

In fact, in case of water, the wetting angle rises with increasing pressure until a constant remaining value at high pressures. Thus, a falling aqueous film may detach in contact with dense carbon diojdde operated in a desorption column at high... 

Adsorptive distillation is an integrated operation in, which adsorption is combined with distillation to separate the close boiling components or constant boiling liquid mixtures. It is a three-phase mass transfer operation in which the adsorbent, usually in the form of (fine) fluidized powder, is introduced into the eolumn along with an inert carrier gas. The adsorbent selectively adsorbs one of the eomponents and flows into the desorption column in, which the adsorbed eomponent is desorbed. Thus adsorptive distillation is successful in separation and in avoiding the formation of azeotropes. Most commonly used adsorbents in the industry are silica gel, activated carbon, zeolite and alumina. Though adsorptive distillation has been reported long back, its industrial and commercial applications are very limited. However, potential application fields for adsorptive distillation inelude separation of toluene/methyl eyclohexane, naphtha reformates, p-xylene/ m-xylene, etc. 

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