ENGINEERING. DESIGN. AND PROCESS DEVELOPMENT T h e differences between these values and the actual values shown in Table I1 clearly indicate the hazard of this procedure and indicate the utility of the Kynch method. Nomenclature
Acknowledgment
A
cross-sectional area, sq. ft. Concentration, tons/cu. ft. initial concentration, tons/cu. ft. concentration of pulp at pulp-water interface, tons/cu. ft. C , = concentration of underflow, tons/cu. ft. Ho = initial height, ft. H I = height of intercept of tangent t o point ( H z , ~and ) H axis,
= C = Co = C, =
ft. H z = pulp height at time h, ft. H , = height pulp would occupy if solids were at underflow concentration, It. = time, days = time required
t t’
-
to eliminate A(Hi H,) units of water, days = time at which pulp height is Hz,days = time a t intersection of tangent to point (H2,h) and H., days
tu
U = upward layer velocity, ft./day U A = unit area, sq. ft./ton solids/day V = particle settling velocity, ft./day V2 = particle settling velocity at concentration GI ft./day
T h e authors wish t o thank R. H. Van Note of the Dorr Co., for supplying the thickening data on the sugar beet industry. literature Cited (1) Anable, A., in Chemical Engineers Handbook (J. H. Perry, editor), 3rd ed., p. 397, McGraw-Hill, New York, 1950. (2) Coe, H. S., and Clevenger, G. H., Trans. Am. Inst. Mining Engrs., 55, 356 (1916). (3) Kynch, G. J., Trans. Faraday SOC.,48, 161 (1952). (4) Roberts, E. J., Mining Eng., 1, 61 (1949). RECEIVED for review May 10, 1954. ACCEPTED October 6, 1054. Presented before the Division of Industrial and Engineering Chemistry at the h’ew York, X. Y . 126th Meeting of the AMERICAN CBEMICAL SOCIETY,
Dynamic Adiabatic Air Drying with Bead-Type Desiccant H. G. GRAYSON Socony-Vacuum Oil
s
Co., Inc., 26
Broadwoy, New York
4, N. Y.
TRIPPED of individual refinements, dynamic gas drying
units operate on a few basic principles. The air or gas is forced through t h e bed of desiccant until the bed reaches a certain degree of saturation At this point the flow is directed to another bed of desiccant while t h e first bed is being reactivated by the application of heat. T h e most important properties of a desiccant in dynamic dehumidification are its moisture adsorption capacity and its ability to lower the dew point of the effluent gas stream. When a humid gas stream passes through a bed of desiccant, t h e first gas t h a t comes in contact Fith the desiccant is dried to the dew point characteristic of the desiccant. The layer of desiccant nearest the inlet becomes saturated rapidly during this phase and little or no drying of the gas occurs as it approaches the outlet side of the bed. As further increments of humid gas pass through the bed, the zone of saturated desiccant progresses steadily through the bed, but the dew point of the effluent gas remains practically constant. As the zone approaches the outlet side, the dew point of the effluent gas rises sharply and increases until it equals t h a t of the incoming gas stream. The bed is completely mturated at this point, and the amount of moisture adsorbed is known a8 the equilibrium capacity. The magnitude of the equilibrium capacity depends on the relative humidity of the incoming gas and is affected only slightly by temperature, as shown in Figure 1 for the range 50’ to 150” F Furthermore, air velocity and desiccant bed depth have no effect on this capacity (6). I n actual operation, a drying unit is seldom run so t h a t the desiccant reaches its equilibrium capacity If it were, its drying efficiency would decrease rapidly near the end of the cycle. A typical adiabatic drying run dew point curve (Figure 2) indicates a sharp rise in the dew point versus capacity curve. The instant of eitluent dew point rise is known as t h e break point, and the quantity of moisture adsorbed up t o that point is known as the break point capacity, dry gas capacity, or capacity at maximum efficiency. It is the break point capacity t h a t is of greatest importance to the designer and operator of drying units producing very low dew point effluents and not the equilibrium capacity January 1955
Much of the data published on air drying by solid desiccants have been obtained on laboratory scale equipment operated under isothermal conditions-Le., the heat of adsorption was removed by proper cooling to maintain a constant temperature (1,4, 6). The equipment used for the studies described in this paper was of sdmicommercial size containing 6.5 to 24.5 pounds of desiccant. depending on bed depth, and runs were made under “adiabatic” conditions. I n industrial installations truly adiabatic adsorption is never obtained because insulation is not sufficient to suppress heat losses entirely. Consequently, the term “adiabatic” is considered as meaning t h a t no attempt was made to remove the heat of adsorption, and that the equipment was insulated. Semicommercial Size Drying Tower I s Operated under Adiabatic Conditions
The equipment, as shown in Figure 3, comprised the apparatus used for the adsorption and desorption runs. The flow was as follows: Laboratory air from a 100-pound main passed through a 6 X 12 inch filter pot filled with a desiccant to remove any entrained compressor oil or moisture, then through a fiberglass filter and strainer to complete the cleanup. The air flow was controlled by a hand-control valve and bypass. T h e control of the steam, which was injected to regulate the inlet humidity, posed somewhat of a problem, as the amount was as low as 0.04 pound per hour for the low velocity-low humidity runs. The source of steam from the 100-pound main was wet as the boilers were located several thousand feet away. The steam required not only throttling and accurate control, b u t also continuous bleeding t o remove any condensed water. The eteam system consisted of a hand-control valve (of the type used in instrument air throb tling), a separator pot with bleed line and pressure gage, a needle valve in the vapor line off the separator, and a restricting orifice just upstream of the steam-air mixing point. The size of the restricting orifice was determined by trial and error. Several orifices were drilled; the smallest size was tried first and found to be adequate to handle the total range of flows required.
INDUSTRIAL AND ENGINEERING CHEMISTRY
41
ENGINEERING. DESIGN. AND PROCESS DEVELOPMENT After i t was mixed, the humid air stream passed t h r o u g h a flowmeter (orifice with mercury displacem e n t t u b e s calibrated against a dry gas meter), past a a AIR ATSO'F. 77'F. dew point sampling o 100.F. point, and on to the x I50.F. top of the tower for the downward adsorption run. The tower itself JT-as 4 inches in inside diameter X 6 feet high with six thermometer ports spaced evenly along the length and was i n s u l a t e d with standard 85% m a g n e s i a insulat i o n , 11/2 inches 0 20 40 60 80 100 120 140 thick. The tower %RELATIVE HUMIDITY OF AIR MEASURED AT THE DESICCANT TEMPERATURE was constructed of 26-gage sheet metal Figure 1. Variation in Adsorption in order to be a s light as possible and Capacity of Sovabead with still airtight and Relative Humidity xas supported on a scale. This scale, which formed the basis for sizing the tower, had a capacity of 7 5 pounds, with 1ounce graduations which could be estimated to 0.1 ounce. The inlet and outlet of the tower were of flexible rubber hose in order to keep the scale a t equilibrium a t all times with no restraining force upon it. The effluent gas passed out of the bottom of the tower through a 12-mesh screen, used to prevent the beads from being blown out, and into the atmosphere after i t was sampled for dew point and temperature. Filling of the tower was accomplished by blowing the beads through a thermometer port using a special funnel; emptying was accomplished by blowing the beads out of a port. Dew points were measured by a conventional mirror cup using a dry ice-acetone or water-ice solution for the cooling medium. The bed was regenerated countercurrently using air electrically heated to a temperature of approximately 400 O F. 3
The physical charactcrietics of the bead-type desiccant are presented in Table I. The range of the variables studied u a s set by several factors. The maximum tower height was limited to 7 2 inches by the capacity of the scale. 11antell (6),Derr (e),and Socony-Vacuum (6')
Physical Characteristics of Sovabead
Apparent density lb./ou. f t . Specific heat, B.t:u./(lb.) (OF.) Residual moisture, % Tt. Particle size (av. diam.), inch
50 0.25
4-6 0.138
Representative Screen AnaIysis (Tyler Screen Scale) Mesh Retained on
Passed through
42
10
0 8
50,
I
,
During a n adsorption run readings were made of elapsed time, scale weight, inlet and outlet dry bulb and dew point temperatures, and desiccant bed temperatures. The readings were continued until sufficient data had been obtained beyond the break point. T h e variables that affect the break point capacity of a desiccant of given physical characteristics are: Superficial linear velocity Bed depth Inlet absolute moisture content Inlet dry bulb temperature Completeness of previous regeneration
Table I.
indicated that superficial velocities of 20 to 120 feet per minute are normally encountered in industry. T h e inlet absolute humidity was varied in steps E O t h a t the moisture content was approximately doubled a t each step. Thus runs were made a t approximately 3 5 O S 60°, and 80" F. inlet dev- point and at bed depths of 18, 36, and 66 inches a t varying velocities. The inlet dry bulb temperature during the adEorption runs was held a t 80" =t5" F. The mass of the apparatus in conjunction with the normal room temperature was generally sufficient to maintain a reasonable approach to 80" F. No attempt has been made in these calculations to correct for these slight deviations in inlet temperature. I n the case of isothermal adsorption, the= variations would be significant. Their effect during adiabatic adsorption is greatly reduced, however, because a t the elevated bed temperatures small changes in temperatmureaffect the relative humidity and, therefore, capacity only slightly.
30
L
EXTRA POLLI TED EOUlLlRRlUM CAPACITY\
/
,
,
/
Y
10
/
-
0
/
1
I
2
4
/
I
WT X ADSORBED
Figure 2.
Typical Drying Curve
I n order to reduce errors caused by leaks in the system or faulty flowmeter reading. all flow rates to the apparatus were calculated by material balance. The flowmeter was used onlp as an indicator of approximate rate of flow. Break Point Capacity Is Affected by Bed Depth, Air Velocity, and Inlet Humidity
Figure 2 shows a decrease in effluent dew point before the constant outlet humidity period is reached. This is called the induction period and has been noted by Amero ( 1 ) and Jury and Licht ( 3 ) . This temperature drop may be attributed t o moisture in the outlet line or in the sampling apparatus which is removed during the initial portion of the run. The temperatures occurring in the desiccant bed during an adsorption run (Figure 4) show the manner in which the adsorption proceeds through the bed. Inspection of the temperature curves brings out the interesting fact that adsorption takes place in a continuous wave, with the break point phenomena occurring a t successive points in the bed. The break point for the total charge occurs when the adsorption zone reaches the outlet level. The break point for this run can be predicted from the temperature curves alone; it occurs a little after the last thermometer in the bed has reached its peak temperature The cooling t h a t takes place in a section of the bed after it has experienced its break point is of great importance in the final break point capacity of the whole bed While this section of the bed has stopped adsorbing efficiently, as it cools it continues t o
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 47, No. 1
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT The manner in which an increase in bed depth affects the break point capacity is two fold. First, it results in the cooling phenomena discussed above. Second, it is probable that the increased ' bed depth results in an increase in contact time which allows the adsorbed moisture to penetrate to the inner pores of the desiccant so that the vapor pressure of the outside surface of the desiccant will be maintained a t a low level and thus will permit adsorption of newly supplied moisture. Figure 7 shows contact time versus break point capacity a t three different bed depths for 61' F. dew point air. rlt a velocity that resulted in a contact time of 3.5 seconds for each bed depth, the break point capacity for bed depths of 18, 36, and 66 inches were, respectively, 4.0,4.3, and 6.9y0. These figures indicate that the cooling phenomenon has a great effect on the break point capacity, especially for deep beds. Figure 4 shows the effect of bed depth on the cooling phenomenon. For a 36-inch bed depth temperatures were from 10" to 20" F. higher a t the break point than for the same inlet absolute humidity in a 66-inch bed. I n Figure 4 the bed temperatures a t the break point for these two runs are also plotted. The advantages of greater bed deDth are. therefore. an increased break Doint capacity and decreased frequency of regeheration. However, these advantages should b e . weighed against the higher costs involved in forcing the air through the deeper bed. At an infinite bed depth the break point capacity would equal the equilibrium capacity. Effect of Inlet Humidity. I n general, for adiaba.tic operations, the inlet absolute humidity has the greatest effect on the break point capacity. One of the most interesting results of this adiabatic study has been the reversed effect of inlet humidity on the break point capacity. The work reported by Amero and associates ( I ) , Ledoux ( 4 ) , Socony-Vacuum (6), and others, showed that under isothermal conditions the amount of moisture
._-_____ FL EXlBLE CONNECTION
W GLOBE OR GATF VALVE
Db HANO CONTROL Ck NEEDLE VALVE
8 PRESSURE
' 0
VALVE
TEMPFRATURE TNzlrA?O? FLOWINDICATOR RESTRICTING ORIFICE DEW PCiNT CUP /NSUL A TED L IN€
@B
GAGE
++
Figure 3.
Air Drying Apparatus
adsorb, and for beds of great height the cooling would continue until that section of t h e bed was at the same temperature as the entering air and would be saturated. Effect of Bed Depth. Data plotted in Figures 5 and 6 and presented in Table I1 indicate the effect of bed depth on break point capacity. For any given set of conditions an increase in bed depth causes an increase in break point capacity.
Table AY. Inlet D e n Point,
AY. Inlet
-4~. Inlet
' F.
Dry Bulb T?mp., F.
Humidity, Grains/ Pound
Dry Desiccant,
35.5 31.0a 37.5 39.0 36.0 61.0 60.5 61.0 63.0 61.7 61.0 82.0 82.6 82.0
78 75 80 77 81 85 82 80 82 85 80 85 83 85
30.5 26.3 33.1 35.0 31.1 80.3 78.8 80.3 86.0 82.0 80.3 166. 7 159.3 166.7
104 104 104 104 104 104 104 104 104 104 104 104 104 104
02.
II.
Operation of Adiabatic Air Dryer Total Adsorbed a t Break Point OS. Wt. %
Calcd. Air Flow, Ft./Min.
Temp. Peak, 0
F.
Elapsed Effluent Time to Dew Point a t Break Point, Break Point, Rlin. 0 F.
Contact Time, Sec.
Bed Depth 18 Inohes 4.2 3.6 3.7 1.9 2.0 3.5 3.8 2.7 1.8 1.4 0.8 1.7 1.9 1.6
36.0 37.0 37.0 38.0 60.0 61.0 64.0 61.0 83.0 78.0 79.3 82.0 83.0
82 80 80 76 80 78 81 79 83 80 81 86 85
31.0 32.4 32.4 33.7 77.3 80.3 89.0 80.3 172.0 145.6 151.0 166.7 172.0
206 206 206 206 206 206 206 206 206 206 206 206 206
15.7 12.6 11.5 7.2 13.0 8.7 7.0 5.8 7.0 4.1 3.7 3.5 4.1
36.0 37.0 37.0 63.0 59 I O 61.0 81.0 79.3 79.0 79.0 82.0
77 80 79 83 80 79 83 83 81
31.0 32.4 32.4 86.0 74.7 80.3 161.3 151.0 150.7 150.7 166.7
393 393 393 393 393 393 393 393 393 393 393
34.2 27.5 24.4 31.4 29.5 26.7 25.9 17.3 17.1 16.1 12.6
24 61 62 110 130 26 32 60 56 62 75 24 20 46
103 97 108 105 107 150 146 153 146 152 147 187 188 198
394 155 136 34 37 131 109 40 34 23
Bed Depth 36 Inches 7.6 26 6.1 58 64 5.6 100 3.5 6.3 23 4.2 58 98 3.4 140 2.8 3.4 25 2.0 58 1.8 58 137 1.7 2.0 134
104 110 109 103 145 137 147 140 185 175 188 195 197
1760 466 400 148 478 131 60 36 121 32 29 11 13
109 I09 102 141 139 134 189 186 195 196 195
2494 864 472 885 260 225 3 69 123 121 87 50
4.0
3.5 3.6 1.8 1.9 3.4 3.7 2.6 1.7 1.35 0.8 1.6 1.8 1.5
11
24 42 15
Bed Depth 66 Inches
82
85
a Run 10 of Figure 2. b Poor regeneration caused
January 1955
8.7 7.0 6.2 8.0 7.5 6,s 6.6 4.4 4.35 4.1 3.2
31 69 112 30 64 104 31 68 67 88 110
- 76 - 65 - 45
- 72 - 50 -21 -- 34 35
- 40 - 34 - 32 - 25 - 22
- 24
- 5b --56 52 - 73 - 58 -- 70 15 - 35
-- 54 64 - 32 - 57 - 40 - 40 -47 - 40 - 23
- 19 - 39 - 26 -20 32 -31 - 20
-
3.8 1.5 1.45 0.81 0.70 3.4 2.8 1.5 1.6 1.45 1.2 3.8 4.5 1.95 6.9 3.1 2.8 1.8 7.8 3.1 1.83 1.29 7.2 3.1 3.1 1.32 1.35 10.6 4.8 2.95 11.0 5.2 3.18 10.6 4.9 4.9 3.75 3.00
low dew point,
INDUSTRIAL AND ENGINEERING CHEMISTRY
43
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT
B E D T E M P E R A T U R E S AT BREAK POINT
8 3 ' F GEW POINT
36' B E D D E P T H
120
1 i~
80
40
/PO
4.
Figure
., / / / I ,
10
L _ _ _ L . . _ -
20
30 40 BED D E P T H - I M C H E S
_I~ -.
50
I
SO
I
70
5. Effect of Bed Depth on Break Point Capacity
Tor all except several 66-inch bed depth runs the break point capacity varied inversely with inlet humidity. Data obtained a t the 66-inch bed depth indicate that, except a t very low velocities, the 61' F. dew point runs showed greater break point capacities than the 37" F. runs. This can be explained by the great,er cooling encountered a t this bed depth. The cooling effected during the 61" F. runs a t the higher velocities produced higher relative humidities than the 3 i " F. runs. The 81" F. runs shoxed the lowest capacities. It is to be expected that a t bed depths beyond 66 inches the additional cooling effect would finally produce the greatest break point capacities for the highest inlet humidity air. Effect of Velocity. Figures 8 and 9 and Table I1 show the variation of break point capacity with superficial velocity through the bed. With all other conditions remaining unchanged, the capacity a t the break point will decrease with an increase in velocity; the effect is more noticeable for shallow beds. This effect is especially apparent a t low velocities where the break point capacity increases rapidly with a decrease in velocity. Figures 5 and 6 indicate that the humidity curves converge to definite values of bed depth at zero adsorption. This indicates that for a contact time below that indicated by the above bed depth and run velocity, there will be no break point but rather the effluent
44
pAol
0
40
20
60
80
I 0
% O F m T A L B E D DEPTH
Bed Temperatures during Drying Run
adsorbed by a desiccant either when it is completely saturated or a t the break point is a direct function of the relative humidity 'of the air with which it is in contact. The heat of adsorption during adiabatic operations raises the bed temperatures considerably. Runs made a t 37" F. inlet dew point showed peak temperatures of 100' to 110" F.; 61' F. inlet dew point showed temperatures of 135' to 150" F.; and 80" F. inlet dew point resulted in temperatures of 1%' to 19.5' F. This rise in temperature considerably reduces the relative humidity of the gas actually passing over the desiccant. The relative humidity of the air a t the peak temperature in the bed for the 3 i 0 , 61", and 81" F. runs yere 10.5, 9.3, and 5.5yc,respectively.
0
2
i
TIME-M'NUTES
Figure
o!
?bo
l$o
240 0-005
TIWE-MINUTES
I /
dew point curve will rise immediately with no horizontal portion a t all. This critical contact time a t isothermal conditions is about 0.4 second for all inlet humidities (6). The data obtained under adiabatic conditions indicate that the critical contact time is a function of inlet humidity, increasing with increase in inlet humidity. ThiEi can be explained by the increase in gas velocity through the bed because of expansion of the gas a t the raised bed temperature, and also by the hypothesis that the higher temperature has a retarding effect on the instantaneous adsorption power of the desiccant. Figure 10 shows the relation between inlet humidity and critical contact time. The critical contact time for the low humidity data approaches the isothermal critical contact time because of the diminished heat effect. For the 37', 61', and 81' F. runs the critical contact time was 0.50, 0.85, and 1.0 second, respectively. h decreaso in velocity, other conditions being constant, will cause an increase in break point capacity because of the increased contact time. This increased contact time will allow the adsorbed moisture to diffuse into the iiiterior of the bead, thereby alloning the entrance to the pore to remain open and capable of further adsorption. Thus, the advantage of using low velocities is in the ability of n bed of fixed depth to adsorb more nioipture before reaching the break point. Also, the decreased velocity results in a low pressure drop through the bed, reducing operating costs. The effluent dew points obtained ranged from -76' to -5" E' although the higher dew point readings n ere probably affecbd by moisture in the line to the dew point cup. The effluent dew point is not affected by bed depth. or by velocity (provided t h a t the critical velocity is not exceecietl): however, the inlet humidity does affect the dew point because the rise in temperature rakes the vapor pressure of the beads, as small as it is. The average
AVERAGE VELOCITY, 6 2 ' / M ! N
00 RED D E P T H - I N C H E S
Figure 6.
Effect
of Bed Depth on Break Point Cap a city
INDUSTRIAL A N D ENGINEERING CHEMlSTRY
Vel. 47, No. 1
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT
1
I N L E T HUMIDITY BE0 DEPTH. 36"
INLET HUMIDITY
$ T W I N T
b 3 7 % DEW POINT
81 ' f : DEW PUINT
61 '6 OEW W I N T
l '
00
1
4
6
8
IO
I
I2
C O Y T ~ C T T I M E - S E C , BASED ON S U P E R F I C I A L /ELOCITY
Figure 7.
Adsorption Capacity versus Contact Time
'0
I20 160 40 80 SUPERFICIAL VELOCITY F T / M I N
4k-27-Zk-m
ZOO
SUPERFICIAL
Figure 8. Effect of Velocity on Break Point Capacity
effluent dew points for the 3 5 O , 61 O, and 81O F. runs were - 5 5 O , -36", and -34" F., respectively. The effluent dew point is also affected by the conditions of regeneration. It has been demonstrated that a slight variation in the residual moisture content of Sovabead will result in a considerable variation in effluent dew point. It follows that the residual moisture content of the desiccant is controlled by the regeneration temperature and by the moisture content of the air which drives off the released moisture during regeneration, for a t the conclusion of regeneration the desiccant is in reality, a t equilibrium capacity with that air. While this equilibrium capacity is small under such conditions of low relative humidity, even minor variations in that equilibrium capacity will be reflected in changes in the dew point (6).
VELOCITY
FT/MIN
Figure 9. Effect of Velocity on Break Point Capacity
Increase in superficial velocity decreases break point capacity. This is especially noticeable a t low bed depths. Increase in bed depth increases break point capacity. Acknowledgment
The author wishes to express his appreciation to SoconyVacuum Oil Co. for granting permission to publish this information and to Paul F. Bruins of the Polytechnic Institute of Brooklyn for his help and advice during the course of the investigation.
"'350
Adsorptive Capacity during Adiabatic Operation Is Less Than under Isothermal Conditions
PmNT
/37sf;
Table I11 is a brief tabulation of some of the results of this investigation compared with isothermal data ( 6 ) . Since the isothermal data were obtained a t 70° F., these data have been adjusted by means of the Sovabead-water vapor isopiestic chart, to correspond to an 80" F. dry bulb temperature. The difference between the isothermal and adiabatic results obtained a t low huniidity is much smaller than a t higher humidities, because of the reduced heat effect.
Table 111.
Comparison of Isothermal and Adiabatic Operation Water
Water Adsorbed at Break Point, Wt. % 36-Inch Bed a__-_ t Dew Point of 66-Inch Bed a t Dew Point of *ir Veloo35' F. 60° F. 60° F. 35O F. ____.._ ity, _____ ____-_ Ft./ IaoAdiaIsoAdiaIsoAdiaIsoAdiaMin, thermal batic thermal batic thermal batic thermal batic 30 7.4 20 0 5,6 8.7 11.0 12 0 22.0 8.0 60 8.0 5.8 16.8 4.2 9.7 7.2 19.0 7.5
l
l
CONTACT
T I M E - S E C , BASE0 ON SUPERFICIAL
Figure 10.
/
VELOCITY
Critical Contact Time versus Inlet Humidity
Conclusions
Literature Cited
The adsorptive capacity of Sovabead when drying air a t atmospheric pressure under dynamic adiabatic conditions is considerably below the isothermal break point capacity. This reduction is caused by the effect of the heat of adsorption which raises the bed temperature. In adiabatic adsorption the break point capacity decreases Fith an increase in inlet a,bsolute humidity a t low bed depths. At greater bed depths, cooling is effected a t the top of the bed so that the over-all capacity a t the break point increases with an increase in inlet absolute humidity.
(1) Amero, R. C., Moore, J. W., and Capell, X. G., Chem. EILQ. Prog., 43,349,1947. (2) Derr, R. B., IND. ENQ.CHEM.,30, 384 (1938). (3) Jury, S. H., and Licht, W., Jr., Chem. Eag. Progr., 48, 102 (19.52). \----,-
(4) Ledoux, E., "Vapor-.4dsorption," Chemical Publiahing Co., Brooklyn, 1945. (5) Mantell, "Adsorption," RIcGraw-Hill Book Co., N e w York, 1945. ( 6 ) Socony-Vacuum Oil Co., 26 BroadFay, New York. Tech.
Bull. T-17,October 1947. RECEIVED for review January 12, 1954.
A C C E P T ~September D 1. 1954.
END OF ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT SECTION January 1955
INDUSTRIAL AND ENGINEERING CHEMISTRY
45
