Pilot-scale column

Under constant pattern conditions the LUB is independent of column length although, of course, it depends on other process variables. The procedure is therefore to determine the LUB in a small laboratory or pilot-scale column packed with the same adsorbent and operated under the same flow conditions. The length of column needed can then be found simply by adding the LUB to the length calculated from equiUbrium considerations, assuming a shock concentration front. 

In the literature one finds a wealth of flow-regime diagrams essentially obtained from pilot-scale columns of 0.30 m or less in diameter and under moderate operating conditions. 

It was derived from a much wider data base of commercial- and pilot-scale columns data. 

Cellular foam occurs at low vapor velocities in small columns, where the wall provides foam stabilization. It occurs with some systems or tray designs but not with others and is promoted by surface tension effects such as the Marangoni effect (99). Cellular foam is uncommon in industrial columns. The foam that causes problems in industrial installations is mobile foam, where the bubbles are in turbulent motion. Mobile foam is associated with the froth and emulsion regimes. Cellular foam is encountered in bench-scale and pilot-scale columns. If cellular foam occurs in the test unit, caution is required when scaling up the results. 

Wad flow (66,67,140,141-149). The tendency of liquid to flow toward the walls of packed columns is a fundamental phenomenon associated with packed-column hydraulics. The development of wall flow is illustrated in Fig. 9.4 using typical measurements by Hoek (140) in a pilot-scale column. The column diameter was 20 in, and the outer distributor nozzle was located about 1.5 in from the wall. In these experiments, wall flow was defined as the flow in the outer ring of the column (with an area of 16 percent of the column cross section). 

Previous hydrodynamic studies of trickle-beds are primarily experimental work involving pilot scale columns, for instance, constructing flow regime maps, and correlating pressure drop and liquid holdup data (1-5). Although these contributions have provided much insight, there is a lot of uncertainty in applying these data for industrial applications. 

This difficulty arises because the size and operating conditions of a large-scale reactor normally differ significantly from that of a pilot-scale column. Commercial hydrodesulfurization reactors are of size up to 20 by 30 ft. and may be operated at up to 70 atmospheres and 400°C. In contrast, pilot-scale hydrodynamic data are obtained from columns of a few inches, or less, in diameter and several feet in height, at near atmospheric pressure and room temperature. 

Figure 1 shows the comparison of theory for the trickling-pulsing transition with experimental results from pilot scale columns for air-water systems. Since most experimental studies did not mention the pressure inside the column, a value of 1.5 atm has been assumed. The agreement with the data of Weekman and Myers (1) is excellent and a good agreement with that of Chou et al. (8) is attained up to moderate gas flow rates. The theory would appear to be in poor agreement with Sato et al. however, in Sato s paper, porosity was not mentioned. Experimental data... 

Figure 1. (a,b,c). Comparison of theory with published trickling-pulsing transition data from pilot-scale columns. 

The average total liquid holdup in a trickle bed reactor decreases with increasing bed depth in a low pressure laboratory or pilot scale column. However, for commercial use where there is a moderate to high pressure input, the holdup is essentially constant (Figure 5). 

The above equation was used for scale-up calculations and design of both the pilot plant and full-scale Electropulse Column. A total of 18 experimental runs for uranium(VI) electrolytic reduction was performed on the 20-cm diameter pilot-scale column. (10) As shown in Figure 4, the predicted reduction efficiency calculated from equation (4) correlated well with the experimental values obtained during these runs. The same good correlation between the predicted and experimental R(u) values was achieved later during cold uranium tests in the full-scale unit (Figure 4). The accuracy of correlation was within the range of 6%. 

Aittamaa (1981) simulated a number of experiments with the systems ethanol-benzene-n-heptane, and chloroform-benzene-n-heptane (data were obtained at Hoffmann-La Roche in a fair size pilot scale column) and 1-butanol-ethanol-water in a 12 sieve-tray column. The Hoffman-La Roche data were taken in a column having 24 sieve trays and 30-cm inside diameter. Unlike many studies of distillation efficiency, these experiments were not carried out at total reflux. The measured flow rates and compositions of the feed, distillate, and... 

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. 

FIGURE 5.8-4 Structured packing (Flexipac) of the sheetmetal type (e) fabricated to (it a pilot-scale column and lb) arranged to fit through the manways of a larger-diameter colutrai (Koch Engineering Co.). 

Analyse the feasibility of different control structures by a controllability analysis for a distillation column methanol-water. Consider the data of the EboAkademi pilot-scale column (Haggblom Waller, 1992). 

Experimental confirmation of MSS in RD was provided by Thiel et al. [23] and by Rapmund et al. [24]. Mohl et al. [1] used a pilot scale column to produce MTBE and TAME. MSS were found experimentally when the column was used to produce TAME, but not in the MTBE process. The measured steady state temperature profiles for the low and high steady states for the TAME process are shown in... 

Figure 10.17 represents a comparison of the concentration profiles in two different ethyl acetate synthesis modes, with and without a decanter. The investigation is performed for the pilot-scale column, with a molar feed ratio acetic acid/ethanol equal to 1.2, reflux ratio equal to 3, and a total feed rate equal to 30kg/h. The distillate-to-feed ratio is set to 0.9. The simulations reveal that the conversion with the liquid-liquid separator is about 5% higher that without a decanter, since there is less water and more acetic acid in the catalytic section. Improved conversion and product enrichment due to liquid-liquid separation result in a significant (29%) improvement of the product purity. Finally, because there is less condensed water in the reflux to be evaporated, the heat duty is reduced by up to 26%. 

Figure 10.17 Concentration profiles with (solid lines) and without (dashed lines) liquid-liquid separation (ethyl acetate system, pilot scale column).

The packed hei t throng which a nonuniform profile persists is a function of column diameter (156). In pilot-scale columns, vapor maldistribution was found to posist for abed he t of the order of 1 ft (155,157). In large-diameter columns, this maldiattibution persists to a much greater hei t (15,152,154). In a number of 15-ft-diameter absorbers (154), vapor maldistribution persisted throu a 50-ft bed the efficiency was about balf that encountered during good vapor distribution. 

After the conditions for the enantiomer separation have been optimized, the loading (injected amount) on the analytical column (16-20 gm particle size) is increased in order to determine the maximum amoimt that will still guarantee the desired purity and recovery. With the assumption that a pilot-scale column shows an identical efficiency to an analytical column, the loading can be determined according to Eq. (11) ... 

Shah verified the effectiveness of the nonlinear estimator by both simulation studies and experimental tests on a pilot-scale column. The work of Weber and Mosler should also be noted. They proposed several control schemes using the sum of two or more temperatures, the difference between two temperatures, and the distillate-to-feed ratio to adjust manipulated variables. 

---