I
A. M. KENNEDY Dominion Laboratory, Department of Scientific and Industrial Research, Wellington, N e w Zealand
Dilute Hydrochloric Acid
...
by a Simple Ion Exchange Process
Acid for muriatic casein can be produced from salt and sulfuric acid. Ion exchanger performance is little affected by changes in the operating variables Capacity of resins was experimental equipment
HYDROCHLORIC
ACID is not made in New Zealand, and 22' BC. acid imported from Australia costs $14.00 per 100 pounds. T o permit dairies to improve existing methods for casein manufacture, small-scale production of this acid was investigated, using salt brine with sulfuric acid as regenerant in the exchange reaction
Re.H
+ NaCl
-.f
Re.Na
+ HCl
The object was to produce hydrochloric acid a t a dairy for not more than $7.50 per 100 pounds. T h e acid strength required was 2 to 5y0 with a permissible salt content u p to 2 or 3%. Design and costing of a plant to produce the equivalent of 80 tons per year of 22' BC. hydrochloric acid, in New Zealand under the conditions recommended here, showed that acid suitable for casein manufacture could be made for approximately $6 to $7 per 100 pounds. This estimate is based on unit costs of $47 per ton of salt and $45 per ton of 60' B&.SUIfuric acid. T h e process, simple and relatively insensitive to changes in the operating variables, is well suited to the fluctuating demand and the available facilities and labor in the typical dairy. Although production of salt-free acid at higher concentrations has not been investigated here, ion exchange could offer a practicable starting point to the small-scale manufacture of hydrochloric acid in out-of-theway localities.
Experimental Apparatus. Laboratory-grade ZeoKarb 225-X8 (Permutit Co., Ltd., London), a high-capacity cation exchange resin
based on sulfonated cross-linked polystyrene (91,was used for the tests. The mesh range of this material as supplied is -16 50 British Standard mesh. A value of 0.56 mm. was obtained for the effective sphere diameter of the moist sodium-form resin, using the method outlined by Kressman and Kitchener (7). Equilibrium data (Figure 1) were determined by the column technique ( 6 ) . Average K values of 1.35 and 0.38, respectively, were obtained for the above reaction in 1.ON solution and the reverse regeneration step using 3.4N sulfuric acid. The resin was packed into a glass column, 2.9 cm. in internal diameter, to a
+
This process
would be economical b in remote locations b for small-scale use depth of 92 cm., measured after backwashing, draining, and settling the bed of resin in the sodium form. The bed volume at this depth, 610 ml., is used here in defining factors such as capacity and regenerant level. The resin bed was supported on glass wool sandwiched between 10-mesh stainless steel gauze. A dip-type conductivity cell (Mullard E 7592) was mounted at the outlet of the column and connected to a Philips conductivity measuring bridge (G.M. 4249). Thus, effluent conductivity could be metered continuously. Procedure. Feed solutions and rinse water were introduced into the column
determined
in this
from overhead constant-level Mariotte bottles. Feed rates were determined by measurement with soap-film meters of the rate at which air flowed into the bottles to replace liquid flowing out. Possible errors from changing head effects were less than 2%. Temperatures throughout were held approximately constant at 20 O C. A conventional operating cycle was used. The bed was first regenerated with a known amount of sulfuric acid at a given concentration and flow rate. The acid was followed immediately with water at the same flow rate to complete the regeneration process. Sodium chloride solution at a given concentration and treatment level was then applied and followed with a water rinse at the same flow rate. Finally, the bed was backwashed with demineralized water before regenerating again. Reagent grade chemicals were used throughout. I n early runs, the effluent during regeneration and saturation was collected continuously in 50- to 100-ml. samples and these were analyzed for hydrogen ion content by titration against standard alkali. In later runs, the operating capacity was determined by analysis of the bulk effluent without aliquot sampling. Titration against silver nitrate with potassium chromate as indicator was used for chloride estimation. Bed Capacity and Holdup. The total operating capacity of the bed, determined by complete saturation or regeneration, was 1170 meq., reproducible to within 1yo. This capacity determination was repeated at intervals without significant change. Information on liquid holdup was needed for analyzing column behavior and predicting commercial plant performance, because of the small quantities of liquid involved in a run. In measuring the holdup for a salt solution of given concentration, sufficient brine was run through the column to saturate the resin. The liquid level was then lowered to the top af the bed and the solution remaining was washed out with water. Chloride analysis VOL. 52, NO. 1 1
NOVEMBER 1960
909
Table
I.
Resin Contraction and Liquid Density Differences Affect Longitudinal Mixing Effluent 1'01. (7' Ml.) PA A B . 1'. , f'iC = fA = A '1 System A-B" PB M1. 0.06 0.95 hI1.
1.01%-NaCI-H20 H20-1. ON NRCI 3 . 4 s H2SOa-HzO H z 0 - 3 . 4 N HzS04
1.04 0.96 1.10 0.91
- 30
230d
t
260
+ 10
200 270
2 - 60
470 410 510 380
240 150 310 110
a Liquid A displaces liquid B at the same flow rate. Total change in bed volume duri::g test. Equals fraction of A in effluent. Liquid holdup in bed is approximately 310 ml.
of effluent collected from the start of the run, without attempting to correct the earlier points for water dilution. N I g is the hydrogen ion normality in the effluent for saturation as well as regeneration and N o , the influent normality-e.g., C1- or
so*-.
Prediction of Operating Capacity
Initial Experiments. The effects of regenerant level and acid and brine concentrations on bed capacity in cyclic operation to a specified break-through point
of the bulk washings allowed the holdup
to be estimated in terms of influent brine concentration. Regenerant acid holdup was similarly determined after converting the resin bed to the hydrogen form. By this means, solute occluded within the particles is accounted for as well as that retained in the column void-space. The net holdup within the bed for all solutions tested averaged 43.5% of the bed volume, measured in equilibrium with the solution. The free liquid surface was maintained at a level of 92 cm. above the bed support in all runs. The actual holdup at this level, including liquid below the support, varied slightly with solution concentration but approximated 310 ml. in most runs. Presentation of Results. Deviations from piston flow can be expected when a heavier liquid is displacing a lighter liquid ( 7 ) and when the resin undergoes shrinkage (2). Mixing effects were ex-
amined for the conditions of this investigation by observing effluent behavior following a sudden change from one influent liquid to another at the same flow rate. Results abstracted from the concentration histories (Table I ) show that there is significant mixing at the concentration levels used. Since the quantities of brine and acid applied in the exchange experiments varied from 1500 down to 300 ml., dilution of the effluent by water holdback at the start of saturation or elution persisted through a considerable part of the run. For this reason, the common practice-satisfactory at low concentrations-of subtracting the holdup from the first sample volume and plotting effluent concentration against the quantity of solution that emerges subsequently has not been adopted here. Instead, effluent concentration ("/No) has been plotted against the total volume ( V )
Cyclic Experiments Show Effects of Regenerant Level and Solution Concentrations on Operating Capacity" Sulfuric acid concn.b 2.2.7T 3.4-v Sodium chloride concn.E 0.75&Y 1 .oA0.75T 1.0\Acid loading, meq.
Table II.
2570 3690
1100 1145
1080 1120
1085 1140
1095 1125
Operating capacity is expressed as meq sodium converted to hydrogcn Acid flov late, 46 ml per minute in all runs Brine flow rate, 63 ml p e l minute and brine lei el 1200 meq
I .O
0.8
0.6
Figure 1. Equilibrium data for sodium-hydrogen exchange on Zeo-Karb 225 show that sodium is preferentially selected
0 \
+ z
0 0.4
0.2
0 0
0.2
0.4
0.6
0.8
",+/NO
910
INDUSTRIAL AND ENGINEERING CHEMISTRY
1.0
(2
=
0.5
) were
examined in
a two-level experiment for these factors, keeping other factors constant. T h e end points of the runs could not be esablished by recording effluent concentration or conductivity, because peak conversion of sodium to hydrogen was not always attained until after the start of the water rinse. A study of the concentration histories for the early runs showed, however: that the given end point could be reached in every case by applying a fixed quantity of 1200 meq. of sodium chloride solution and this brine levcl was used in all tests. Three complete cycles were carried out under each set of conditions and the operating capacities were averaged (Table 11). Within any set of results, the standard deviation was only once as high as 1% of the mean and in general less than 0.5%. Capacities estimated from regeneration and treatment results agreed closely. Two cycles performed at the end of the series under the same conditions as the first set of runs gave results which agreed with the earlier ones to within 0.770. The 0.75N brine appeared to give a slightly higher capacity a t a given flow rate than the 1.0.Vsolution but acid concentration showed little effect over the range considered. Regenerant level produced the most significant effect although the increase in acid consumption at the higher level was far in excess of the gain in capacity. I t seemed from these results that regeneration a t a much lower level might be economically desirable. Cyclic studies over wide ranges of acid and brine loadings offered a practicable route to establishing optimum levels, but the procedure was expected to be tedious. An attempt was therefore made to use these initial experiments for predicting operating capacity as a function of acid and brine levels without further cyclic work. Elution from Partly Saturated Beds. Hiester and Vermeulen ( 5 ) and Goldstein (3) have presented solutions to the problem of elution from partly saturated ion exchange columns, under conditions such that the eluting fluid follows immediately the saturating stream a t the same flow rate, with the eluting component replacing the saturating component at the same concentration. Pro-
H Y D R O C H L O R I C ACID I .o
0.8
0 0.6
z
1 I
*
0.4
0.2
0 0
500
v
1000
1500
2000
(MI.)
Figure 2. Effluent concentration histories for saturation of the partially regenerated b e d converge on the curve for the fully regenerated b e d 1.ON sodium chloride a t a flow rate of 1.1 ml. per second W Hydrogen remoining on bed after incomplete saturation with 1300 ml. of brine
vided enough saturating liquid has been used, the elution curves come together beyond a certain limit and follow a common path that does not depend on the degree of prior saturation ( 7 7). I n the work described here, partial regeneration of the bed with sulfuric acid was followed, after a downflow water rinse, by exhaustion with sodium chloride solution at a different concentration and flow rate. Equilibrium and rate constants for the two parts of the cycle differ, and the above equations cannot be used to give a quantitative description of the exhaustion process. At mod-
erately high regeneration levels, however, it may be expected by analogy that the effluent concentration plots for exhaustion should converge on the curve for exhaustion of the fully regenerated bed. Experimental evidence for this is provided in Figure 2 by the concentration histories for saturation of the bed with 1.ON sodium chloride solution, following regeneration a t sulfuric acid levels ranging from 1520 to 4500 meq. (complete regeneration). Results for 0.75N brine obey a similar pattern. T h e eventual convergence of the plots for the partially and fully regenerated
THESE CQNDITIONS ARE RECOMMENDED FOR A COMMERCIAL PLANT Brine Concentration level
F l o w rate
12 % 8 pounds per cubic foot 0.8 g.p.m. per cubic foot
Sulfuric Acid Concentration level
Flow rate
28 % 8.5 pounds per cubic foot 0 . 4 g.p.m. per cubic foot
beds explains why, in the cyclic experiments described, the bed could be exhausted to a fixed break-through point by applying the same quantity of brine in every run. Once the curves come together, the subsequent behavior of the effluent is not affected by the initial state of regeneration of the bed. Therefore, at any point on the common part of the curves, the state of saturation of the bed must also be independent of regeneration level ; and regeneration of the bed after it has been exhausted to such a break-through point should follow a fixed path. Thus, a single concentration history should describe regeneration of the bed a t all levels within the above range. This is supported by the results for regeneration under varying conditions of the backwashed bed (Figure 3). Again, results for one concentration only ( 3 . 4 N ) are shown, but these are fully representative of the elution data. Optimum Brine a n d Acid Levels. These observations simplify the problem of predicting operating capacity as a function of brine and regenerant levels, for given concentrations and flow rates. I n the first place, the complete saturation curve for the fully regenerated bed shows how the capacity is affected by operating beyond the initial break-through. U n used capacity at a particular brine level is given by the area below the curve beyond this level ; and predictions about the effect of brine level on capacity, based o n the common part of the curves, will apply a t lower regeneration levels. T h e curve also shows what quantity of brine must be applied to reach a given break-through point and this estimate will be the same whether the bed is fully or partly regenerated. Secondly, the complete regeneration curve for a bed exhausted to a specified break-through point enables the operating capacity at this end point to be determined as a function of regenerant level. This, in conjunction with the estimate of brine quantity, allows the total leakage or the fractional conversion of sodium to hydrogen to be estimated for the treatment step. Mindick (8) has described a similar application of the complete regeneration curve for the case where the bed is uniformly presaturated after regeneration. Under these conditions, however, saturation curves for the partly and fully regenerated beds d o not converge; and leakage occurring at the start of saturation cannot be identified with saturant remaining in the bed after regeneration. I n establishing optimum conditiofis for hydrochloric acid production, capacities were estimated from the area above the regeneration curve (Figure 3) for a fixed brine level of 1200 meq. and varying acid levels. R a w materials costs were comVQl. 52, NO. 1 1
NOVEMBER 1960
91 1
I*
o
0.a
r.
P0
r
\ I 0.4
0.2
0 0
200
400
800
600
v
io00
1200
1400
ieoo
(MI.)
Figure 3. A single effluent concentration plot describes the regeneration process and gives operating capacity, as a function of acid level, for a bed exhausted with a specified quantity of sodium chloride BS
Sodium remaining after incomplete regeneration with 1520 meq. acid. Saturation for each cycle, 1200 ml. of 1.ON sodium chloride. Acid flow rates, 0.75 ml. per second
HzS04 Regeneration 0 X I
rn
Ml.
Normality
1090 1090 765 765
3.4 3.4 3.4 3.4
puted from the ratios of salt and sulfuric acid used per unit of hydrochloric acid produced, to determine the optimum regenerant level. Capacities were then estimated for this acid level and various brine loadings (Figure 2) to find the effect on costs of changes in brine level. T h e optimum levels arrived at by this procedure were 1300 meq. of sodium chloride (equivalent to 8 pounds per cubic foot of resin) and 1520 meq. of sulfuric acid (7l/2 pounds per cubic foot). T h e estimated capacity for these loadings was 930 meq., compared with a saturation capacity of 1170 meq. T h e reliability of the prediction technique is shown by the fact that cyclic experiments under these conditions gave a measured capacity of 920 meq. (Figure 2). T h e actual limit on regeneration level above which the saturation curves may be expected to come together has not been studied. A material-balance approach of this kind might have application to other problems of elution from partly saturated beds and further work is being undertaken with a view to testing the wider utility of the method.
Z, = k,a,
Previous H&04 Regeneration 111. Normality 1190 1090 1090 765
2.2 3.4 3.4 3.4
acid and brine concentrations and flow rates. To gain a fuller understanding of the process and of its probable cost structure, the effects of changes in these variables were examined. T h e possi-
QPbV
NoF
with k,a,
T h e previous discussion is limited to a single bed depth and to only one set of INDUSTRIAL AND ENGINEERING CHEMISTRY
=
60D, ~
dZP
(77)
Mid-po'int slopes have been evaluated from the break-through curves for 1.ON and 2.0147 salt solutions at 1.1 ml. per second on the 92 cm. bed and for l . 0 N solution a t the same flow rate on a 150 cm. bed (Figure 4). Values of Z p derived from these slopes are, respectively, 28, 16, and 45. Cross plots of mid-point slope against Z, at constant r have been drawn on log-log paper from Hiester's family of curves. These show, for values of ZPwithin the range 12 to 55, that the
THESE FACTORS AFFECT OPERATING CAPACITY
Effects of Other Variables
91 2
bility of re-using excess acid was considered and scale-up effects were investigated in a larger diameter bed, Saturation Variables. Hiester and others (4)have shown how to predict the controlling resistance in an ion exchange process with the aid of a mechanism Internal diffusion will conparameter trol the exchange rate if { is less than 0.3 is greater and external diffusion if than 3.0. Calculated values of { for the sodium-hydrogen exchange on ZeoK a r b 225 from 1 . O N and 2.0N sodium chloride solutions are, respectively, 0.4 and 0.2 a t a flow rate of 1.1 ml. per second, so that solid-phase diffusion must be rate-controlling. These authors present a graphical relation for diffusional cases between the mid-point slope of the break-through curve, the equilibrium parameter r, and a column-capacity parameter 8. The latter parameter is analogous to the number of transfer units in the column and, for solid-phase internal diffusion controlling, it is given by the relation
Regenerant level
Acid and brine concentration Saturation of bed Regeneration con d itio n s Re-use of excess acid
HYDROCHLORIC ACID
%r($,)o.s,
mid-point slope, expressed in the dimensionless form -
is propor-
tional to Lln, where n = 1 for a highly favorable equilibrium and 0.5 for a linear equilibrium. At r = 0.74, n = 0.78 so that, in a given ion exchange system (fixed Q, pa, k,a,) having this value of r , the dimensionless slope should be approximately proportional to
0.8
o0.6
z
>
(G~)"'~*, pro-
vided the rate process is governed by internal diffusion. Experimental results for the saturation of a fully regenerated bed agree closely with this expression (Figure 4 ) . T h e relation above can be used as a n index of column behavior under nonsaturation conditions. Thus, when other factors are constant an increase in brine concentration or flow rate should tend to diminish the slope of the break-through curve and lower the operating capacity. T h e earlier results for 0.75N and 1.ON brine (Table I) agree with this. A comparison of the effects of concentration for a fixed operating time rather than a fixed flow rate was of interest in this investigation. Altering the flow rate in inverse proportion to concentration, to give a constant time of contact between acid and resin, should not affect the relative sharpness of the break-through curve. T h e operating capacity should therefore be independent of concentration under these conditions. Cyclic experiments in the 92-cm. bed, using fixed quantities of brine and regenerant, confirm this (Table 111). The equilibrium parameter r increases slightly with concentration due to the fall in the solution activity coefficient ratio; this possibly accounts for the drop in capacity at the highest brine concentration. Cyclic studies at varying bed depths under nonsaturation conditions were not performed. However, the mid-point slope relation and the saturation experiments on 92- and 150-cm. beds show that a slight increase in capacity per unit volume should result when the bed length is increased with other factors remaining constant. For a fixed time of contact, the capacity should be largely independent of bed length. Regeneration Variables. When r is greater than 1 (unfavorable equilibrium) and equilibrium is maintained everywhere in the column, the equation for the concentration history is ( 7 7)
Differentiation of this equation leads to the following expression for mid-point slope :
0.4
0.2
0 500
1500
1000
2000
v
2500
(MI.)
Figure 4. Lengthening the bed or lowering the brine concentration increases the relative steepness of the break-through curve for saturation a t a given flow rate W 2.ON sodium chloride; 92 cm. bed,
chloride; 150 cm. bed.
V 1.ON sodium chloride; 92 cm. bed. 0 1.ON sodium Respective values of
Flow rates, 1.1 ml. per second.
0.0026, 0.0021 5, and 0.001 85 mI.-l
and of QpbV dx
NO (dV)s-o.i
1.46, 2.53, and 3.7
of the break-through curve cannot be altered by changes in bed length or in solution flow rate or concentration (unless the latter factor affects r ) . T h e average value of r for the equilibrium between 3.4N sulfuric acid and the sodium form of Zeo-Karb 225 is 2.6 (Figure 1). Experimental results for the regeneration, at this concentration, of the fully saturated bed can be fitted moderately well by the equilibrium-limit equation for this value of r (Figure 5). Predictions based on this equation may therefore be expected to apply approximately to the practical regeneration process, even though this is rate-limited. Thus, changes in acid concentration should have little effect on the operating capacity under nonsaturation conditions, when other factors remain constant.
This was suggested by the earlier results (Table 11) and confirmed by cyclic experiments at sulfuric acid concentrations ranging from 10 to 20y0 (2.2 to 4.7N). Raising the flow rate resulted in a slight fall in the capacity of the 92 cm. bed (Table IV), possibly because of increased axial mixing. For a given time of contact between acid and resin, the 20% acid would be the most efficient regenerant. Changes in bed depth were not investigated for the partially saturated bed. However, lengthening the bed should not alter the specific capacity a t a given flow rate but might tend to lower it slightly if a constant operating time is maintained. Re-use of Excess Acid. T h e sulfuric acid regeneration of a resin like Zeo-
Table 111. Bed Capacity Varies Only Slightly with Brine Concentration When Contact Time Is Fixed
Table IV.
Brine Normality 1.0 1.5 2.0 3.0
Brine Flow Rate,= Ml./Min. 65 43 33 22
Operating Capacity, Meq. 932 924 922 893
a Flow rates proportioned to give a constant time of contact between brine and resin of 20 minutes; 1300 meq. of sodium chloride used and bed regenerated in each cycle with 1520 meq. of 4.7N H2S04 at 33 ml. per minute.
Increasing Acid Flow Rate Lowers Capacity
Sulfuric Acid Loading, Meq.
Flow Cyclic NormalRate, Capacity, ity Ml./Min. Meq.
1520
3.4
1520
4.7
1690
4.7
22.5 45 16.5 33
947a 920 95Zb 922
10 33
99Se 972
a 1300 meq. of 1.ON NaCl at 65 ml. per 1300 meq. of minute used as saturant. 2.ON NaCl at 33 ml. per minute. 1300 meq. of 2.ON NaCl at 65 mi. per minute.
This shows that the relative sharpness VOL. 52, NO. 1 1
NOVEMBER 1960
91 3
K a r b 225 is comparatively inefficient (Figure 3) and the re-use of acid collected during the latter stages of regeneration is sometimes recommended (70). An operating capacity of 930 meq. was obtained with the 92-cm. bed on applying 650 ml. of 2.ON sodium chloride solution a t 33 ml. per minute and regenerating with 330 ml. of 4.71V sulfuric acid at 16 ml. per minute. Acid re-use was investigated at these loadings and flow rates by separately collecting the last 300 ml. of acid effluent and using this at the start of the next regeneration, before applying fresh acid. Under these conditions, the capacity increased by only 37, to 980 meq. A similar test, in which 440 ml. of 4.7N acid was applied with each regeneration and only the final 220 ml. of effluent collected for re-use, raised the capacity from 1020 to 1070 meq. T h e slight extent by which the capacity increased in these experiments can be attributed to the unfavorable nature of the acid-resin equilibrium ( K o 0 . 3 8 ) and to suppression of the sulfuric acid dissociation in sulfate solution. T h e gain in capacity is not commensurate with the increased complexity of the regeneration procedure and the longer operating time needed. I t may be concluded that acid recycling would not improve the economy of the process.
results for the design of a factory unit, concentrations and flow rates selected were: sulfuric acid, 207, (4.7.4‘) a t 0.4 gallons per minute per cubic foot (33 ml. per minute); and sodium chloride solution, 1270 (2.221‘) at 0.8 gallons per minute per cubic foot (65 ml. per minute). The figures in parentheses refer to the 92 cm. bed. T h e design was based on this bed depth although, as the results show, a longer bed could be used without greatly affecting the performance. An examination of the experimental saturation and regeneration curves for the above conditions showed that 8.5 pounds of sulfuric acid (100%) and 8 pounds of salt should be used per cubic foot of resin, for optimum performance. Equivalent loadings for the 92-cm. bzd are, respectively, 1690 and 1300 meq. The measured capacity of the bed for these conditions was 972 meq. This figure, representing 827, of the total capacity of the bed, corresponds to the production of 3.6 pounds of 1007, hydrochloric acid per cubic foot per cycle. T h e concentration of the bulk acid so produced would be 4 to 4.57, with a salt content of approximately 2y0, and the over-all operating time (including rinsing and backwashing) would be 1 hour per cycle. To examine the effects of increasing the column diameter, a few cycles were carried out for the above conditions in a 92-cm. bed, 10 cm. in diameter. A drop of 3.57, in the capacity per unit volume resulted. Liquid distribution was less uniform in the 10-cm. than in the 3-cm. column and brine-water displacement experiments showed that longitudinal mixing was more severe. I t was anticipated that liquid distribution as uniform as that in the 10-cm. bed could be obtained in a larger plant (2 to
Selection of Process Variables
T h e conversion process is relatively insensitive to changes in operating conditions over quite wide ranges. The choice of variables could be adapted to meet the normal requirements of a specific dairy and peak demands could be countered by raising the flow rates without much loss in capacity. I n utilizing the
3 feet in However: below the for design
diameter) by careful design. a 10% reduction in capacity laboratory results was allowed purposes.
Acknowledgment
The author is grateful for the assistance given by W. J. Ritchie in carrying out the experimental work and wishes to thank the Director, Dominion Laboratory, for permission to publish the results. Nomenclature
d,
= mean diameter of resin particle,
0,
diffusivity, sq. cm ./sec. = volumetric flow rate. ml./sec. = particle-phase mass-transfer coefficient, set.-' equilibrium constant for exchange, dimensionless hydrogen ion concentration in effluent, eq./l. influent concentration or total concentration in liquid, eq. ’1. ultimate capacity of resin, eq.1 g. dry resin
cm.
F k,a,
= particle-phase
(=i),
equilibrium parameter, dimensionless bulk-packed volume of column,
1. volume of saturating solution fed to column, 1. 2L-H ,‘.\b. dimensionless void fraction of column as packed. dimensionless fluid density, g.11. bulk-packed density of dry resin, g./l. column-capacity parameter for diffusional cases. dimensionless mechanism parameter, defined in Eq. 6, ref. (4)
Literature Cited
v
”0
500
1000
v
EXPERIMENTAL
I500
I ~ o - c ~ BE^.
2000
(MI.)
Figure 5 . Experimental break-through curves for regeneration of the fully saturated b e d can b e fitted approximately b y an equilibrium-limit equation
914
INDUSTRIAL AND ENGINEERING CHEMISTRY
(1) Baddour, R . F.. Goldstein, D. J., Epstein, P.: IND. ENG.CHEM.46, 2192 11954). ( 2 j Byrne, E. B., Lapidus? L., J . Am. Chem. SOC.69, 2830 (1947). (3) Goldstein. S., Proc. Roy. Soc. London A219, 151. 171 (1953). (4) Hiester, N. K., Radding, S . B., Nelson, R . L., Vermeulen, T., A.I.Ch.E. Journal 2, 404 (1956). ( 5 ) Hiester, N. K., Vermeulen, T., J . Chem. Phvs. 16. 1087 11948’1. (6) Klam.;. K.; Linssen, J. C. H., van Krevelen, D. W., Chem. Eng. Sci. 7, 204 (1958). ( 7 ) Kressman, T. R . E., Kitchener, J . A., Discusszons Faraday SOC.7, 90 (1949). ( 8 ) Mindick. M., IND. ENG. CHEhf. 47, 96 (1955). (9) Permutit Co. Ltd., London, “ZeoKarb 225 and De-Acidite FF,” 1952. (10) Tooper, E. B., Wirth, L. F., “Ion Exchange Technology,” Academic Press, New York, 1956. (1 1) Vermeulen, T., “Advances in Chemical Engineering,” Vol. 11, Ibid., 1958.
RECEIVED for review March 2, 1959 RESUBMITTED April 25, 1960 ACCEPTEDJune 13. 1960
