Large column experiments

The incubation digest (7.0 ml) contained 1 ml of 0.022 M phenyl phosphate 2.5 ml of 0.1 M acetate buffer, pH 5.0 0.5 ml of test enzyme solution and 3.0 ml of solutions of acceptors giving a final concentration as shown in the third column. Incubation time, 30 min. Digests were inactivated by 3.0 ml of 10% trichloroacetic acid solution and were analyzed for phenol and inorganic phosphate. In the case of the standard acceptor, 1,4-butanediol, the expected transfer product, 1,4-butanediol phosphate, was isolated in a yield of 35% from a large-scale experiment. The hydrolysis of this phosphate ester by prostatic acid phosphatase liberated approximately equimolar amounts of 1,4-butanediol and inorganic phosphate. 

The accumulation of calcium carbonate in deep ocean sediments is a complex process. It is primarily governed by the interplay between biological production of calcium carbonate in the nearsurface ocean and the chemistry of deep ocean waters. After over 100 years of study, the major problem of determining the saturation state of deep ocean water remains largely unresolved. It is currently possible, using recent laboratory measurements, to arrive at saturation states that differ by as much as a factor of 2. Both laboratory and water column experiments indicate that calcium carbonate dissolution kinetics are not simply related to saturation state. It is our opinion that the saturation state problem must be resolved and considerably more detail added to our present knowledge of calcium carbonate dissolution kinetics and accumulation patterns before attempts to model the accumulation of calcium carbonate in deep ocean sediments can be truly successful. 

A large, pilot scale column measuring 671 cm in height and 66 cm in diameter was used to study this decommissioning option. Broken but uncrushed ores of about 6 inch size were placed in a column, and rinsing studies commenced after the completion of the copper extraction experiments. Clean water was fed into the top of the column, and leachate was collected weekly at the bottom of the Gaspe Large Column 2. 

The authors found that the model-predicted As concentration is close to the leachate concentrations from the column packed with dust from the continuous reactor (1 120 H.gL-1 versus 1 330 xgL-1), when the solubility product of scorodite from Robins (1990) and the triple layer model is used. Only 11% As in the system was sorbed onto hydrous ferric oxide surfaces. Arsenic concentrations in the leachate are largely controlled by scorodite solubility. It should also be pointed out that simulations using solubility only and without including surface adsorption resulted in a closer match (1 270 n-gL-1 versus 1330 piglA1). For the simulation of the column experiments using wastes from the batch-reactor, the triple layer model predicted too low an As concentration (33 jigL-1 versus 120 pigL-1). 

The one-dimensional column experiments and parameter-estimation procedure described in this work provides rate constants, or time scales, for sorption/desorption that are independent of the flow and the large-scale media geometry. By using model sorbents the rate constants can be related to the dominant binding interaction, which helps define their applicability. 

Bubbles in microbubble colunuis are observed to be separated by a liquid film from the wall at almost all gas space velocities. At low gas space velocities, the microbubble column experiences bubbly flow. The bubbly flow is defined by microbubbles, which are spherical and as large as the channel diameter. Since bubbles of this size are highly unstable without surfactants, the gas space velocity has to be low enough to allow enough space between bubbles in order to prevent coalescing. 

Well-known examples are absorption columns, for example, the absorption of HCl in an exhaust air by water. Experience shows that quite large columns are required for this purpose, whereas the equilibrium calculation just requires one theoretical stage due to the electrolyte character of hydrogen chloride. Columns like that can only be successfully designed by application of a rate-based model (see also Section 14.5). 

Fig. 1. Chromatograms illustrating difference between a small zone (a) and a large zone (b) size exclusion experiment. In the saull zone experiment, the elution volume, V, is taken as the apex of the peak In a large zone experiment, the elutxon volume is the centroid volume, V, of the leading boundary. The shaded areas represent the volume loaded onto the column in each case.

If the gas velocity becomes too large, the column experiences an overload (flooding). The liquid from one tray is then transported to the one above, and the... 

The advantage of this type of adsorption analysis evidently lies in the stability of the zones theoretically at.least one should be able to use as large columns as desired and therefore to carry out also very difficult separations. The main drawback of the elution method—the tailing— is eliminated. The fact that the different zones are in close contact is a difficulty which,- however, may be eliminated by interposing substances of intermediate adsorption and of a different chemical nature so that they may easily be removed afterwards. Examples of the application of tills procedure may be found in a paper by Hahn and the author (Tiselius and Hahn, 1943), in which various saccharides were separated, and some experiments on amino acids and peptides already mentioned. In case of strong adsorption, the affinity of the adsorbent has to be reduced by pre-treatment with suitable substances as described in the last mentioned paper. Nevertheless, losses are sometimes serious in this method. The experience so far seems to show that with the adsorbents now available the displacement method is applicable chiefly for mixtures of closely related substances, which are able to displace each other completely. However, for fatty acids in organic solvents on carbon the method has failed, but in the separation of gaseous hydrocarbons it seems quite satisfactory (Claesson, 1946). 

The copoly(N,N-dichlorosulfonamide S/DVB) oxidant in bead form used in a column process is a very efficient oxidant, of the poisonous nitrite ions even if they are in very diluted aqueous media. The nitrite ions are oxidized to the hrmdred fold less toxic rritrate ions. The reaction of nitrite oxidation by means of this water-insoluble heterogeneous oxidant, runs at favorable speed, as can be seen from the large flow intensities in the column experiments. 

Giovanni Boocaletti is gratefully acknowledged for the large number of experiments that paved the way to enantioselective Lewis-acid catalysis in water. Furthermore, we kindly thank the Syncom company for the use of the chiral HPLC column. 

The effect of increasing column diameter is to increase the tendency for circulation, and hence to increase the axial mixing (62,63). However, extremely few measurements of axial mixing at the industrial scale are available, so large-scale contactor design must still rely quite heavily on empirical experience with the particular type of equipment. 

Example 1 Calculation of FUG Method A large hutane-pentane splitter is to he shut down for repairs. Some of its feed will he diverted temporarily to an avadahle smaller column, which has only 11 trays plus a partial rehoiler. The feed enters on the middle tray. Past experience on similar feeds indicates that the 11 trays plus the rehoiler are roughly equivalent to 10 equilih-rium stages and that the column has a maximum top-vapor capacity of 1.75 times the feed rate on a mole basis. The column will operate at a condenser pressure of 827.4 kPa (120 psia). The feed will he at its huhhle point (q = 1.0) at the feed-tray conditions and has the following composition on the basis of... 

---