1. B. BRAGG Packed Column Corp.,
30 Church St., N e w York 7,N. Y
Goodloe packing, knitted of Monel wires, has a high throughput capacity, a theoretical plate efficiency approaching the best, an unusually low pressure drop, and average holdup as compared with other packings
T H E R E is a sizable gap between the operating characteristics of Panapak packing and Stedman packing. Panapak packing has been shown by Scofield ( 9 ) to have a capacity somewhat greater than twice that of a conventional bubble tray and to exhibit a fractionating ability of about 0.7 theoretical plate per foot of packed height. Stedman packing has been shown by Bragg (5) to have a capacity of approximately one half that of a conventional bubble tray and to exhibit a fractionating ability of 3.5 to 4.5 theoretical plates per foot of packed height in commercial size columns ( 3 ) . I t was believed that a packing of intermediate characteristics was needed, and such a packing has been developed by the cooperative efforts of the Metal Textile Corp., Roselle, N. J., and the
1062
Packed Column Corp. The essential feature of the packing was devised by A. M. Goodloe of the Metal Textile Corp., and the packing has been named Goodloe packing. Description The packing used in the tests described below was made of 0.0045-inch diameter Monel wires with 12 filaments being used to form a strand wherein the 12 filaments were twisted approximately 0.4 turn per linear inch. The strand so formed was knitted on 30 needles to form a tube made up of loops that were approximately "8 inch wide; there were five courses per inch. The tube was then flattened to make a double thickness ribbon, approximately
INDUSTRIAL AND ENGINEERING CHEMISTRY
4.25 inches wide, which was crimped, the creases of the crimping being a t an angle of about 60' to the center line of the ribbon. The creases were 3 / 1 6 inch deep and "16 inch wide at the top, and were spaced 5/16 inch apart. Two ribbons were then arranged in reversed relationship so that the creases crossed each other and thereby determined the spacing of the adjacent ribbons. The tlvo ribbons were rolled together until a cartridge was formed having enough layers to provide a diameter to fit the column snugly. The open structure that results from the knitting and the space produced by the creases provides tortuous passageways for the vapor, resulting in continuous division and recombination of the vapor streams, thereby promoting effective mixing. The bunched wires are
of capillary nature and provide multiple tortuous channels for the flow of the liquid. These channels are in repeated contact with others where the bunched wires cross, which results in continuous division and recombination of liquid streams, providing effective mixing of the liquid. The cartridges were sized to fit the column snugly but not so tightly that the structure would be compressed. The bunched wires are resilient and conform well to the contour of the interior of the column. This characteristic, combined with the capillarity of the bunched wires, results in effective removal and distribution of liquid that may tend to run down the wall of the column. Testing The 25-mm.-diameter packing was tested in a glass column, packed to a depth of 24 inches, which was insulated with a silvered vacuum jacket. The 3-inch and 4-inch nominal diameter packings were tested in steel columns. The 3-inch column was packed to a depth of 355/8 inches, and the 4-inch column was packed to a depth of 35 inches. The 3-inch column was insulated with approximately 2.5 inches and the 4-inch column with approximately 2 inches of Fiberglas standard pipe insulation. The packing in the glass column rested on a “honeycomb” support which was designed to have a total cross-sectional area of the holes equal to the cross-sectional area of the column. The packing in the steel columns was supported on 2 X 2 mesh stainless steel screens of 3/32-inch diameter wire. These screens in turn rested on short pins made of the same material, driven into shallow holes drilled into the inside column wall. No distributors were used with any size of column, as preliminary tests indicated no substantial difference in the theoretical plate efficiency when operating with or without a distributor. Except for elimination of the vapor jacket on the steel columns, ultimate removal of the reflux rate measuring bottle as being inadequate, and electrical heating of both reboilers, the apparatus used was similar to that used by Bragg for the Stedman packing tests (2, 4 ) . Binary mixtures of benzene and ethylene dichloride were used in all tests, which were made a t atmospheric pressure and with total reflux. The reflux rates for the glass column were determined by turning the stopcock of the reflux collector below the column so as to interrupt the flow of reflux back to the reboiler and noting the time required to collect a definite amount of reflux. A determination was similarly made of the bottom reflux rate when the
Section of Goodloe packing, 3-inch diameter
VAPOR
00
05
I
-
VELOCITY
15
IO I ’
F E E T PER
20
I ’
I
25
’
I
’
SECOND
35
30 I
I
I
40 IO
100
7
0.7
70
5
05
50
u 0.3
30
0.2
20
-10
3
W
2 l -
4
l k 5 01 007 0.7
2
0.5
5 z
,
0.3 0.2
0.05
m a: w
IO
I
’ 9 a
003
8 002 8
_I
3
4
0 2t; E
s
K
n 0.1 w 001 E
0.07
bl
0
I
0.2
REFLUX
2a
0.007
0
$ A
IF. 0.7
0 005
0.5
PRESSURE DROP
0 003
0.3
0 -
HOLDUP
0 002
0.2
X -
THEO. P L A T E S
0001
0. I
0.05
I
0.4
2
2
5 7 l55 a
LEGEND
0.6
0.8
RATE
-
1.0 GAL.
1.2
1.4
I6
I8
PER HOUR
Figure 1. Characteristics of 25.0-mm. diameter packing-24.0-inch packed depth VOL. 49, NO. 7
JULY 1957
1063
Table 1.
Reflux Rate, Gal./Hr.
Above packing
rl ‘D”
Below packing
E f f i c i e n c y Tests
Pressure Drop Mm. (Inches Hg Hz0)
Total Holdup, Liters
Theoretical Plates in Coluinn
-_
Cni.
H.E.T.P. (Inches)
25.0-h‘lm. (0.984-Inch) Diameter; 61.0-Cm. (24-Inch) Packed Lengt,h 0.003 0.006 0.015 0.044 0.069 0.089 0.089 0.121 0.158 0.168 0.237 0.264 0.277 0.333 0.385 0.435 0.485 0 491 0.512 0.587 0.620 0.640 0.698 0.771 0.786 0.802 0.834 0.863 0.910 0.942 1.06 1.17 1.21 1.21 1.28 1.32 1.38 1.44 1.57 1.61 1.69 -0.06 I
1.4901 1.49275 1.4913 1.4871 1.48055 1.4845 1.4834 1.4834 1.4807 1.4754 1.4734 1.4784 1.4570 1.47185 1.4576 1.47075 1.4585 1.4710 1.4593 1.4660 1.4705 1.4590 1.46945 1.4631 1.4688 1.4650 1.4640 1.46875 1.4657 1.46425 1.4592 1.45925 1.4625 1.46435 1.4637 1.4635 1.4636 1.4634 1.46325 1.4635
... ...
1.4485 1.45375 1.4540 1.4546 1.45235 1.4564 1.4555 1.4584 1.4591 1.4535 1.4541 1.4602 1.4469 1.4550 1.4476 1.4553 1.4483 1.4561 1.4487 1.4534 1.4557 1.4491 1.45635 1.4521 1.4555 1.45325 1.4527 1.4566 1.4535 1.45315 1,4498 1.4498 1.4517 1.45335 1.45295 1.4538 1.4530 1.4534 1.4536 1.4532
... ...
0.09
...
(0..05)
0.13 0.15 0.13 0.28 0.21 0.30 0.37 0.30 0.30 0.34 0.52 0.49 0.50 0.73 0.77 0.90 0.93 1.55 1.08 1.12 1.31 1.68 1.59 2.11 2.00 2.04 2.37 2.65 3.29 3.83 4.20 4.20 5.34 4.99 5.79 6.15 8.05 7.00 9.07
(0.07) (0.08) (0.07) (0.15) (0.11) (0.16) (0.20) (0.16) (0.16) (0.18) (0.28) (0.26) (0.27) (0.39) (0.41) (0.48) (0.50) (0.83) (0.58) (0.60) (0.70) (0.90) (0.85) (1.13) (1.07) (1.09) (1.27) (1.42) (1.76) (2.05) (2.25) (2.25) (2.86) (2.67) (3.10) (3.29) (4.31) (3.75) (4.86)
...
...
...
... ...
0.0153
...
0.0210
... ... ... ... ... 0.0294 ... ... 0.0329
... ... ... 0.0363 ... ... ...
... ...
0.0476 0.0409
... ... ... 0.0470 ...
0.0504 0.0527 0.0538 0.0552 0.0549 0.0543
...
0.0553 0.0569
...
... 0.0043
45.9 1.33 42.3 1.44 39.1 1.56 31.8 1.92 27.1 2.25 26.5 2.30 26.2 2.32 23.2 2.63 19.6 3.11 20.5 2.98 17.9 3.40 16.2 3.76 17.2 3.54 15.4 3.96 15.3 3.98 14.1 4.32 14.3 4.26 13.4 4.55 14.1 4.32 12.4 4.91 13.4 4.55 12.9 4.72 11.8 5.16 11.6 5.25 12.2 5.00 11.7 5.20 11.6 5.25 11.0 5.54 12.0 5.07 11.2 5.44 11.7 5.20 11.8 5.16 11.6 5.25 11.1 5.49 11.0 5.54 9.7 6.28 5.59 10.9 10.2 5.96 6.21 9.8 5.80 10.5 Flood point Nondrainable holdup
(0.52) (0.57) (0.61) (0.76) (0.89) (0.91) (0.92) (1.03) (1.22) (1.17) (1.34) (1.48) (1.40) (1.56) (1.57) (1.70) (1.68) (1.79) (1.70) (1.93) (1.79) (1.86) (2.03) (2.07) (1.97) (2.05) (2.07) (2.18) (2.00) (2.14) (2.05) (2.03) (2.07) (2.16) (2.18) (2.47) (2.20) (2.35) (2.45) (2.28)
7.798-Cm. (3.070-Inch) Diameter; 90.49-Cm. (35.625-Inch) Packed Length 0.00 0.05 0.10 0.19 0.22 0.69 1.04 1.82 2.28 2.65 3.28 4.19 5.43 6.38 7.97 8.71 10.40 11.50 12.92 13.90 13.95 14.59 14.94 15.26 15.96
1064
...
...
1.4967 1.4965 I . 4906 1.48485 1,4808 1.4786 1.4769 1.4750 1.4737 1.4727 1.4700 1.4684 1.4678 1.4668 1.4663 1.4644 1.4636 1.4631 1.4634 1.46265 1.4630
1.4530 1.4531 1.4530 1.4535 1.4536 1.4536 1.4536 1.4536 1.4536 1.4535 1.4536 1.4537 1.4538 1.4539 1.4539 1.4534 1.4534 1.4534 1.4533 1.4532 1.4534
1.4633
1e 4533
... ...
...
...
INDUSTRIAL AND ENGINEERING CHEMISTRY
0.03 0.04 0.04 0.06 0.04 0.06 0.07 0.09 0.13 0.17 0.30 0.47 0.63 0.90 1.23 1.62 2.54 3.51 4.80 5.79 5.95 6.05 6.91 6.42 9.90
(0.015) (0.02) (0.02) (0.03) (0.02) (0.03) (0.04) (0.05) (0.07) (0.09) (0.16) (0.25) (0.34) (0.48) (0.66) (0.87) (1.36) (1.88) (2.57) (3.10) (3.19) (3.24) (3.70) (3.44) (5.30)
. I .
0.05 0.16 0.04 0.36 0.37 0.38 0.49 0.50 0.61 0.62 0.33 0.44 0.65 0.55 0.76 0.99 1.40 1.00 1.43 1.27 1.22 1.44 1.41
...
...
e . .
I..
55.3 54.2 39.2 30.3 25.7 23.4 21.8 20.0 18.8 18.0 15.6 14.1 13.5 12.5 12.1 11.0 10.3 9.9 10.3 9.8 9.8
1.63 1.67 2.31 2.98 3.52 3.86 4.15 4.52 4.81 5.03 5.80 6.41 6.70 7.23 7.47 8.21 8.77 9.13 8.77 9.23 9.23
(0.64) (0.66) (0.91) (1.18) (1.39) (1.52) (1.63) (1.78) (1.90) (1.98) (2.28) (2.53) (2.64) (2.85) (2.94) (3.24) (3.46) (3.60) (3.46) (3.63) (3.63)
10.2 Flood point
8.86
(3.49)
...
...
GOODLOE COLUMN P A C K I N G Table 1.
Reflux Rate, Gal. /Hr
s”D”
.
Above packing
Efficiency Tests (Continued)
Pressure Drop hlm. (Inches Hg HzOf
Below packing
Total Holdup, Liters
Theoretical Plates in Column
H.E.T.P. (Inches)
Cm.
10.226-Cm. (4.026-Inch) Diameter; 88.9-Cm. (35.0-Inch) Packed Length 0.33 0.52 0.78 0.95 1.16 1.49 1.54 2.04 2.44 3.66 4.87 5.58 6.52 7.24 9.03 9.71 10.28 10.63 11.12 11.55 11.63 12.00 12.52 13.18 13.47 13.96 14.39 15.01
1.4986 1.4920 1.4869 1.4822 1.4809 1.4791 1.4791 1.4774 1.4766 1.4737 1.4725 1.4708 1.4705 1.4703 1.4699 1.4677 1.4683 1.4649 1.4635 1.4658 1.4638 1.4643 1.4664 1.4650 1.4653 1.4653 1.4663 1.4646
0.02
1.4549 1.4548 1.4549 1.4554 1.4553 1.4549 1.4553 1.4554 1.4549 1.4549 1.4549 1.4552 1.4551 1.4549 1.4549 1,4547 1.4547 1,4549 1.4546 1.4551 1.4548 1.4549 1.4547 1 * 4549 1.4553 1.4552 1.4547 1.4548
reboiler was being heated at such a rate that the vapors just reached the top of the column, and this value was subtracted from the measured reflux rates so that the reflux rates reported represent the reflux entering the top of the column. The reflux rates for the steel columns were determined by calibration of the voltage readings on a n autotransformer that was used to control the heating rate. The voltage readings were calibrated against reflux rates determined with the measuring bottle. I t was soon found, however, that the line voltage varied enough to cause errors, and consequently a second calibration was based on the condenser inlet and outlet water temperatures and the water rate. T h e reflux rates determined by these two methods were averaged. The heat input necessary to overcome the heat losses and drive the vapors just to the top of the column was determined, as was the heat picked up by the condenser water from the room under the same conditions. Corrections were then made, so that the reflux rates reported for the steel columns also represent the
0.03 0.03 0.03 0.04 0.04 0.06 0.06 0.07 0.19 0.24 0.21 0.39
(0.01) (0.005) (0.015) (0.015) (0.015) (0.02) (0.02) (0.03) (0.03) (0.04) (0.10) (0.13) (0.11) (0.21)
0.50 1.12 0.99 1.18 1.21 1.44 1.10 1.61 1.64 1.46 1.85 2.28 2.26
(0.60) (0.53) (0.63) (0.65) (0.77) (0.59) (0.86) (0.88) (0.78) (0.99) (1.22) (1.21)
0.01
... (0.27)
...
VAPOR
0.0
0.14 0.035 0.25 0.42 0.53 0.63 0.56 0.52 0.57 0.68 0.69 0.81 1.10 1.21 1.52 1.30 1.03 1.09 1.41 1.64 1.50 1.28 1.34 1.66 1.73 1.66 1.75 1.97
-
VELOCITY
0.5
1.0
1.5
FEET
2.0
64.4 39.4 31.2 25.0 23.7 22.3 21.8 20.0 19.9 17.2 16.1 14.3 14.1
14.2 13.9 12.3 12.8 9.6 8.7 10.1 8.8 9.1 11.1
9.7 9.5 9.6 11.0 9.5
PER
2.5
I
g k
(0.54) (0.89) (1.12) (1.40) (1.48) (1.57) (1.61) (1.75) (1.76) (2.04) (2.17) (2.45) (2.48) (2.46) (2.52) (2.85) (2.74) (3.64) (4.02) (3.46) (3.98) (3.84) (3.15) (3.61) (3.68) (3.64) (3.18) (3.68)
SECOND
3.0
3.5
cn 0.5
$0! z
1.38 2.26 2.85 3.55 3.75 3.98 4.07 4.45 4.47 5.17 5.51 6.21 6.30 6.25 6.40 7.23 6.95 9.26 10.2 8.80 10.1 9.77 8.00 9.16 9.35 9.26 8.08 9.35
0.7
IO
10
100
7
7 5
50
5
70
1.0
1.5 2.0
U
3
30
2 l -
2
20
3.0 4 .O
1 8
I
3
W
5
m (1:
w
IO 7 5
0.7 0.5
3
5
07
5
0.5
I
0.3
I
0.3
02
.g
02
z
U
-J
2 3 04 2 2'5U -1
0
8
0
w
Q $
a
U
0. I
w“ +
01
”3
W
2
0.07
0.7
3 U
0.05
0.5
0.03
0.03
0.3
0.02
0.02
0.2
001
0.0 I
0.I
007 0.05
a
b Figure 2. Characteristics of 7.798cm. diameter pa~king--35~/~-inch packed depth
0
4 6 R E F L U X RATE
2
-
8 10 12 14 16 GAL. PER HOUR VOL. 49, NO. 7
JULY 1957
1065
VAPOR
VELOCITY
05
00
-
FEET
PER
each at lower rates. After the lowest rate, the boilup rates were increased by steps until the flood point was determined. Limitations imposed by the capacity of both the reboiler and the condenser prevented operation of the 4inch column over about one half of its flood point capacity. The reflux samples removed from above and below the packing were analyzed by refractive index, and the number of theoretical plates was calculated by the equation of Beatty and Calingaert ( I ) , using values of relative volatility determined by Bragg which are more consistent than values used in earlier papers (2, 4, 5 ) . These values are available as a table of theoretical plates us. refractive index and will be published in a subsequent paper.
SECOND
15
IO
20
m O5 0.7
2 IO '
15
0- 2 0 ii-
$
30
40
Results
0
- HOLDUP
0
2
4
THE0
6
REFLUX R A T E
-
002
002
02
001
001
01
PLATES
8
IO GAL.
12 PER
14
16
HOUR
Figure 3. Characteristics of 10.226-cm. diameter packing-35.0-inch packed depth reflux entering the top of the columns. The drainable portion of the holdup of the glass column was determined by shutting off the heat to the reboiler and as quickly as possible dropping the electric heating coil away from the reboiler, removing the pinch clamp from a connection from the reboiler to an auxiliary condenser, and turning the stopcock to prevent return of reflux to the reboiler. Vapors formed by residual heat in the walls of the reboiler and by the reduction in pressure escaped to the auxiliary condenser. The reflux that collected was the drainable portion of the holdup of the column. The nondrainable portion was determined by pouring a measured quantity of the binary mixture through the previously dried column at room temperature and a t a high rate, so that the packing was thoroughly wet, and measuring the quantity of liquid that would drain from the packing. This portion of the holdup is indicated by the zero bottom column reflux rate holdup value which corresponds to -0.06 gallon per hour a t the top of the column and equals the heat loss rate of the column. The holdup of the steel columns was determined by noting the liquid level in the reboiler with a calibrated level gage glass before starting the run, while the liquid was at the boiling temperature, and then noting the level after equilib-
1 066
rium conditions had been attained. The difference between the initial level and the levels during the tests, corrected for the amounts of liquid removed as samples, represented the amount of the binary mixture in the column, condenser, and reflux collector both as liquid and vapor. This figure is not entirely correct as a representation of the holdup of the column, but the error is on the high or conservative side. This method of determination, combined with the difficulty of reading the level accurately, gave somewhat erratic results a t times. The flood points were determined by increasing the distillation rates by steps until an increasing pressure drop and a decreasing reboiler level at a steady heating rate indicated that the column was loading. The loading could also be observed through an unsilvered slit in the silvered vacuum jacket of the glass column. While some improvement in efficiency might have been obtained by flooding the packing before testing, it was felt desirable to obtain results representative of non-preflooded operation. Consequently, the testing procedure was to start a series of tests at a relatively high rate of perhaps 80 to 90% of the flooding rate. The first test data were obtained after about 8 hours and succeeding tests \vere made for at least 4 hours
INDUSTRIAL AND ENGINEERING CHEMISTRY
The results obtained on the three sizes of packing are shown in Table I and in Figures 1 to 3. Comparison of the results obtained with those reported for other high efficiency packings (2, 4, 6-8) indicates that the Goodloe packing has a higher throughput capacity than most, if not all, other such packings. This high capacity is combined with a theoretical plate efficiency that approaches that of the best of the other packings at equivalent reflux rates. The pressure drop of the Goodloe packing is usually low, being lower per theoretical plate a t the flooding point and of the order of 10 to 60% of the pressure drop per theoretical plate at equivalent reflux rates, compared with most other high efficiency packings. The holdup is about average, higher than some packings and lower than others at equivalent reflux rates. The packing is more convenient to handle than many others, requiring no special tolerances in the column diameter and still being in the form of units rather than a multiplicity of small pieces.
literature Cited (1 ) Beatty, H. A , , Calingaert, G., IND. ENG.CHEM. 26, 504-8 (1934). ( 2 ) Bragg,L. B.,Zbid., 33,279-82(1941). 131 Ibid.. 45.1676-7 11953). Bragg, L. B.: IND. ENG. CHEM.,ANAL. ED. 11, 283-7 (1939). Bragg, L. B., Trans. Am. Inst. Chem. Engrs. 37,19-50 (1941). Cannon, M. R., IND.ENG.CHEni. 41, 1953-5 (1949). Fisher, A. W., Jr., Bowen, R. J., Chem. Eng. Progr. 45, 359-69 (1949 ). (8) Henleinj A . C., Manning, K. E., Cannon, M. R., Ibid., 47, 344-6 (1951). ( 9 ) Scofield, R. C., I b i d . , 46, 405-14 (1950).
RECEIVED for review September 15, 1956 ACCEPTED December 17, 1956
