Packed column having pressure-absorbing mechanism

When a packed column having a pressure-absorbing mechanism satisfies the following conditions, the pressure absorbing mechanism has a sufficient packings-supporting ability in spite of its simplicity, the disorder of flow of fluid is slight and the effect of separation of materials is high: (1) the inside diameter (D cm) is 10 cm or more, (2) the aforesaid pressure-absorbing mechanism comprises solid parts and passage spaces through which packings can pass, (3) the specified circumference ratios of most of said passage spaces are 10/D or more and their lengths in the flow direction are larger than the -1.5th power of the circumference ratio, (4) the above passage spaces exist within 1 cm from any position on the upper and lower sides of the aforesaid solid parts, and (5) the specified shielding degree of the pressure-absorbing mechanism is 0.01 or more and 0.8 or less.

This invention relates to a packed column having a mechanism for reducing a 
pressure to be applied to packings. 
When materials are industrially separated by using a packed column, it is 
necessary to use a large packed column. However, large packed columns have 
been disadvantageous in that the pressure loss increases because of, for 
example, distruction or deformation of packings. In order to solve such a 
problem, it is known to use, for example, a pressure-absorbing mechanism 
for supporting packings in the middle of the packed column, as disclosed 
in British Pat. No. 1,203,439. As said pressure-absorbing mechanism, there 
have generally been used those having such a structure that the packings 
are partitioned and supported by a net or the like through which a fluid 
can pass but the packings cannot. However, such pressure-absorbing 
mechanisms having a structure through which packings cannot pass have been 
disadvantageous not only in that the structures of the mechanisms are per 
se complicated but also in that the structure of the packed column and the 
packing operation are complicated, because pipe, valves, nozzles and the 
like are required to be provided in order to pack the packings into each 
packing section partitioned by said mechanism, or the packed column is 
required to be designed so that sections can be assembled which packing 
successively them with packings. 
In order to solve these problems as to the packed columns having such a 
conventional pressure-absorbing mechanism, the present inventors have 
conducted extensive research, and have consequently developed a 
pressure-absorbing mechanism which has a simple structure and causes only 
slight mixing of a moving phase fluid. It has also been found that when 
this pressure-absorbing mechanism is used packed column having excellent 
performance characteristics can be obtained. 
According to this invention, there is provided a packed column having a 
pressure-absorbing mechanism, characterized in that (1) the inside 
diameter [D(cm)] of the column is 10 cm or more, (2) the 
pressure-absorbing mechanism comprises solid parts and passage spaces 
formed thereby through which packings can pass, (3) the circumference 
ratios as defined herein of most of the passage spaces are (10/D) or more 
and their lengths (cm) in the flow direction are larger than the -1.5th 
power of the circumpference ratio, (4) the passage spaces exist within 1 
cm from any position on the upper and lower sides of most of the aforesaid 
solid parts, and (5) the shielding degree as defined herein of the 
pressure-absorbing mechanism is 0.01 or more and 0.8 or less. 
According to this invention, it is possible to simplify the structure of 
the packed column, to impart a sufficient supporting ability to the 
column, and to reduce the disorder of flow of fluid, by allowing the 
packed column to have the above-mentioned pressure-absorbing mechanism. 
According to this invention, it is sufficient that an inlet for charging 
packings is provided only in the upper part of the packed column, and the 
structure and piping of the packed column can be made very simple as 
compared with those of packed columns using a conventional 
pressure-absorbing mechanism which requires an inlet for each section. 
Further, this invention is characterized in that since packings can 
substantially uniformly be placed in the whole column by supplying the 
packings to the highest section of the column, this invention, as compared 
with conventional apparatus, facilitates not only the initial packing of 
the column but also additional packing, for example, in the case where the 
height of the packing layer or the like varies in the course of operation 
and it becomes necessary to additionally supply the packings. 
The pressure-absorbing mechanism in the packed column of this invention 
comprises solid parts subjected to the pressure of a packing layer and 
passage spaces.

As to the reference numerals in the drawings, 1 shows a solid part of a 
pressure-absorbing mechanism, 2 a passage space of the mechanism, 3 a beam 
supporting a pressure-absorbing mechanism, 4 an outlet-inlet of a 
distributor-collector, 5 the A surface of the distributor-collecter, 6 the 
B surface of the distributor-collector, 7 a cavity of the outlet-inlet, 8 
the column body, and 9 a groove of the distributor-collector. The unit of 
the sizes in FIGS. 15 to 30 is mm. 
The term "passage spaces" used herein means spaces in the 
pressure-absorbing mechanism as shown by the reference numeral 2 in FIG. 2 
and correspond to the unhatched portions in FIGS. 3(i) to 3(vii). Each of 
the spaces is defined by the walls of the solid parts surrounding the 
space, the plane or curved surface having the minimum area contacting the 
upper ends of the said solid parts and the plane or curved surface having 
the minimum area contacting the lower ends of the said solid parts. 
However, when the inside wall of the packed column is a part of the 
surfaces defining the passage space, the aforesaid planes or curved 
surfaces are extrapolated perpendicularly to the inside wall of the packed 
column and the inside wall part between the upper and lower planes or 
curved surfaces is regarded as a part of the solid parts. 
The term "circumference ratio" used herein means the largest value obtained 
by dividing the length [l.sub.1 (cm)] of the circumference of the 
cross-section formed by cutting one of the passage spaces at any position 
by a plane perpendicular to the center line of the packed column 
(hereinafter referred to as "the cross-section of column") by the 
cross-sectional area [S.sub.1 (cm.sup.2)] of the said cross-section. That 
is to say, when the circumference ratio is taken as .rho., .rho.=[maximum 
of (l.sub.1 /S.sub.1)]. 
The range of the circumference ratio according to this invention is 10/D or 
more, preferably 0.2 to 10. 
The preferable range of the circumference ratio varies depending on the 
form of the packings. For example, when the packings are in the spherical, 
powdery, granular or ground form, the most preferable range of the 
circumference ratio is 1 to 10, and when the packings are a mixture of a 
filament or a fiber and a spherical, powdery, granular or ground material, 
the circumference ratio is 0.2 to 2. 
When the circumference ratio is small, the pressure-absorbing effect 
decreases, and when it is large, the mixing of the moving phase fluid 
occurs, so that the separating ability of the packed column tends to be 
reduced. 
The term "the length in the flow direction of a passage space" [l.sub.2 
(cm)] used herein means the average value of the lengthes in the flow 
direction of the walls surrounding a passage space. The term "the lengths 
in the flow direction of the walls" means the distances between the upper 
and lower sides of the wall of a solid part measured in such a direction 
that the minimum length is given when a segment of a line which is 
parallel to the center line of the packed column is projected on the wall 
of the solid part. Referring to FIG. 3-(v), a-a'-b, c-c'-d and the like 
correspond said lengths. The average value calculated by integrating these 
lengths throughout the whole circumference of the passage space and 
dividing the integrated value of lengths by the length of the 
circumference (l.sub.1) defining .rho. is called "the length in the flow 
direction of a passage space". In this invention, l.sub.2 is larger than 
the -1.5th power of the circumference ratio .rho.. Further, l.sub.2 is 
more preferably in a range of from 0.5 cm to 50 cm. 
When l.sub.2 is small, the strength of the pressure-absorbing mechanism 
becomes insufficient, and moreover its pressure-absorbing effect is 
decreased. When l.sub.2 exceeds 50 cm, the separating ability tends to be 
lowered. 
The term "upper and lower sides of a solid part" used herein means the end 
surfaces of the solid parts defining each passage space corresponding to 
the top and the bottom in respect to the flow direction of fluid in the 
packed column. When FIG. 3-(v) is referred to as an example, the surfaces 
a-a.sub.1, b-b.sub.1, c-c.sub.1 and d-d.sub.1 correspond to the end 
surfaces. Even in the extreme case where the areas of a-a.sub.1, 
b-b.sub.1, c-c.sub.1 and d-d.sub.1 are zero, they are called "end 
surfaces". For example, positions corresponding to e, g and h in FIG. 
3-(vi) and FIG. 3-(vii) are also called "end surfaces". 
In this invention, as to the distribution of the passage spaces, it is 
necessary that the passage spaces be present within 1 cm from any position 
on the upper and lower sides of the solid part. Owing to such distribution 
of the passage spaces, the influence of the solid parts on the moving 
phase fluid can be diminished. 
The term "shielding degree" used herein means the largest of the values 
obtained when the packed column with the pressure-absorbing mechanism is 
cut by a plane perpendiculary to the center line of the column, the sum 
total of the cross-sectional areas of the solid parts inside the column 
obtained is divided by the cross-sectional area of the inside of the 
column obtained, and the same procedure is repeated by shifting the 
cutting plane continuously. 
The shielding degree must be 0.01 to 0.8. When it is less than 0.01, the 
pressure-absorbing effect is insufficient, and when it exceeds 0.8, the 
influence on the moving phase fluid is increased, and the separating 
ability is reduced. 
The preferable range of the shielding degree is varied depending upon the 
average height of the pressure-absorbing mechanism. When the average 
height is 0.1 to 1 cm, the shielding degree is preferably 0.7 to 0.3; when 
it is 1 to 5 cm, the shielding degree is preferably 0.5 to 0.1; and when 
it is 5 to 50 cm, the shielding degree is preferably 0.3 to 0.03. The term 
"the average height of the pressure-absorbing mechanism" used above means 
a value obtained by calculating the average value of the lengths of the 
solid parts of the pressure-absorbing mechanism inside the column in the 
longitudinal direction of the column. 
The pressure-absorbing mechanism of this invention can be used as it is 
when it has a sufficient strength for supporting the pressure, for 
example, when the pressure applied to the pressure-absorbing mechanism is 
low or when the inside diameter of the packed column is small. However, 
when the pressure-absorbing mechanism has no sufficient strength, it is 
necessary to provide pillars, beams or the like as shown in FIG. 4 in 
order to support the pressure-absorbing mechanism of this invention. These 
pillars, beams and the like preferably have a structure which causes only 
slight stagnation or mixing of the fluid. Particularly in the case of 
pillars, the widthes of the upper and lower sides thereof in the flow 
direction are preferably adjusted to 5 cm or less. When such pillars are 
provided, they are preferably arranged, for example, in parallel crosses 
on different levels as shown in FIG. 4. 
As to the form of the pressure-absorbing mechanism according to this 
invention, various forms may be used such as lattice form, porous-plate 
form, cylindrical form and the like as shown in FIGS. 5 and 6 in addition 
to the drainboard form shown in FIG. 2. 
Details of preferable examples of the solid part and the passage space are 
shown in FIG. 7-(i) to FIG. 7-(xiii) as a section along the III--III line 
in FIG. 2. 
As exemplified in FIGS. 7-(ii), 7-(iii), 7-(v), 7-(vi), 7-(vii), 7-(viii), 
7-(ix), 7-(x), 7-(xii) and 7-(xiii), a structure having a positive slope 
in relation to the flow direction is more preferable. The term "a positive 
slope in relation to the flow direction" used above means a plane provided 
in such direction that the plane interrupts the flow of the fluid in the 
packed column. 
The passage space in this invention is preferably in the following form in 
order to reduce the disorder of flow of the fluid: That is to say, when 
the passage space is cut by a plane parallel to the longitudinal direction 
of the packed column, the width of the resulting section is constant, 
monotonously decreases, shows a combination thereof, in the direction from 
one of the upper and lower sides to the other; or the width decreases and 
then immediately increases; or decreases and thereafter becomes constant 
and then increases, in the same direction as above. Several concrete 
examples of such preferable forms of the section of the passage space are 
as shown in FIGS. 7-(i) to 7-(xiii). 
Although the pressure-absorbing mechanism of this invention is most 
preferably provided throughout the column cross-section, a sufficient 
effect is obtained if the cross-sectional area of the passage spaces 
having the characteristics of this invention is 50% or more of the total 
cross-sectional area of the passage spaces in the column cross-section 
referred to in definition of the shielding degree. 
Further, a sufficient effect is obtained when in the upper or lower side of 
the solid part, the zone in which no passage space exists within 1 cm is 
less than 10% of the total area of the upper or lower sides. 
The packed column according to this invention is effective particularly 
when the inside diameter of the column is large. That is to say, the 
packed column of this invention has a significant effect when it has an 
inside diameter of 10 cm or more, though the inside diameter is preferably 
at least 30 cm, more preferably at least 60 cm. 
The packed column of this invention is improved in performance 
characteristics by installing, as described above, a distributor-collector 
on the input side and/or the output side of the packed column. 
The distributor-collector is a means which is placed at the inlet or the 
outlet and serves to distribute a fluid uniformly and rapidly in the 
direction of the radius of the packed column while suppressing the 
disorder of the fluid flow as much as possible before the charged fluid is 
brought into contact with the packings, and to rapidly collect the fluid 
that the contact with the packings has been completed, while suppressing 
the disorder of the fluid flow as much as possible. 
The distributor-collector installed in the packed column of this invention 
has a cavity in its inside, and the average distance [l.sub.3 (cm)] 
between the following two surfaces A and B forming the cavity is defined 
as l.sub.3 =kD.sup.2/3 in which 0.004.ltoreq.k.ltoreq.0.04: 
Surface A: an end surface of a segregating material or a porous plate for 
supporting the segregating material, through which the fluid can pass but 
the packings cannot, said surface being nearer to the outlet or inlet than 
the other end surface. 
Surface B: a surface of the part to which the outlet or inlet is connected, 
said surface facing the A surface. 
In the above equation, l.sub.3 is a value obtained by dividing the volume 
of the cavity formed between the surfaces A and B by the cavity area. 
The cavity area means the maximum of the areas of the cavity projected on a 
plane parallel to the column cross-section. When the maximum exceeds the 
cross-sectional area of the inside of the column, the cross-sectional area 
of the inside of the column is taken as the cavity area. 
The volume of the cavity does not include the volume of the inside of the 
outlet-inlet, and the outlet-inlet is partitioned from the cavity by the 
plane defined by connecting the points at which the inclination of the B 
surface 6 in FIG. 8 to the column cross-section exceeds 30.degree.. 
In the present distributor-collector, when k is in the range of 
0.004.ltoreq.k.ltoreq.0.04, the disorder of the flow of fluid caused when 
the fluid passes through the distributor-collector can be reduced. When 
the k value is more than 0.04, the volume of the cavity of the 
distributor-collector increases, the disorder of the flow of fluid caused 
when the fluid passes through the cavity becomes serious, and the time lag 
in the flow of fluid in relation to the position of the column 
cross-section tends to become great. Therefore, such k values are not 
desirable. When the k value is less than 0.004, the flow of the fluid in 
the distributor-collector becomes ununiform, or the flow condition of the 
fluid flowing through the cavity is greatly altered by a slight 
deformation of the A and B surfaces forming the cavity, so that stable 
performance is not realized. Therefore, such k values are neither 
desirable. 
Particularly in a packed column aiming at separating substances by 
chromatogrpahy, the disorder of the flow of fluid influences the 
separation efficiency greatly, and therefore, the k value is preferably 
adjusted to a range of 0.005.ltoreq.k.ltoreq.0.03. 
The cavity may be formed so as to be a substantially complete space by 
reinforcing the segregating material constituting the A surface by 
inserting partially spacers or the like between it and the B surface, for 
the purpose of forming a rigid structure, or may be formed by inserting 
spacers having many voids between the A and B surfaces throughout the 
whole surface. 
As the spacer having many voids, there may be used a sheet formed by 
regularly or irregularly aligning filaments made of a polymer such as 
plastics or the like or an inorganic material such as a metal, ceramics or 
the like, said filaments having a mean cross-sectional area of 0.01 
mm.sup.2 or more when cutting the filaments perpendicularly to the 
longitudinal direction, a sheet formed by weaving said filaments, said 
sheet having a void percentage of at least 60%, preferably at least 70%. 
Said filaments may be either finely cut or infinitely continuous. The void 
percentage is calculated as [1-v/(S.sub.2 xt)].times.100 (%) in which t is 
the thickness (cm) measured under a load of 100 g/cm.sup.2 applied to 
between two plates in between which said sheet is sandwiched, S.sub.2 is 
the area of said sheet (cm.sup.2) and v is the excluded volume (cm.sup.3) 
of said sheet. The term "excluded volume" means the volume of water 
increased when said sheet is immersed in water. 
Although the cavity is formed by inserting the spacer having many voids 
between the A and B surfaces, the spacer and the A surface may be unified. 
That is to say, for example, the spacer and the A surface may be unified 
with an adhesive; the surface of the spacer may be densely woven by a 
spacial weaving method such as twilling or the like to allow the surface 
to serve as the A surface (a segregating material), and the surface of a 
sheet of a thermoplastic material may be made dense by means of a hot 
calender or the like to allow the surface to serve as the A surface (a 
segregating material). 
As the segregating material, there may be used materials through which 
fluid can pass but packings cannot, such as nets, cloth, porous sheets, 
porous plates, nonwoven fabrics, filter paper, fine lattices and the like. 
It is more preferable that the B surface or the distance between the A and 
B surfaces has the following characteristics. [1] The A and B surfaces 
form the structure that the distance between them is constant in most 
directions from the outlet-inlet to the circumference within a distance of 
20% or more and 80% or less of the distance between the outlet-inlet and 
the circumference, and in the other part closer to the circumference than 
the said part where the distance between the surfaces is constant, the 
distance between the surfaces becomes small as the part approaches to the 
circumference. 
The term "most directions" means such an extent that the 
distributor-collector of this invention can sufficiently exhibit its 
effect, and it is sufficient that the sum total of the angles of parts 
where the distributor-collector has the form of this invention is 
300.degree. or more around the outlet-inlet as a center. [2] The B surface 
has grooves arranged radially from the opening of the outlet-inlet. 
The cross-sectional view of one example of the distributor-collector of [1] 
is shown in FIG. 8. Reference numeral 4 shows an outlet-inlet, 5 the A 
surface, 6 the B surface, 7 a cavity, and 8 the packed column body. 
Since the distance between the A and B surfaces decreases in the vicinity 
of the circumference in the cavity where the amount of the flowing fluid 
is smaller than in the vicinity of the outlet-inlet, the flow rate of the 
fluid is not decreased, so that it becomes possible to reduce the time lag 
in the flow of the fluid in the vicinity of the circumference. 
When the distance between the A and B surfaces in the vicinity of the 
center is constant, the distributor-collector of this invention enables 
the narrowing of the parts that the distance between the A and B surfaces 
is extremely small in the vicinity of the circumference, as compared with 
the case where as shown in FIG. 9, the B surface has only one slope and 
there is such a taper that the distance between the A and B surfaces 
increases with a decrease of the distance from the center, so that the 
part that the fluid flows with difficulty can be narrowed and a smooth 
flowing can be realized. 
Further, it is desirable that in said distributor-collector, the distance 
between the A and B surfaces in the circumference is the minimum in said 
cavity and is 0.5 mm or more. When such a structure is employed, there is 
no part where the distance of the cavity is zero in the circumference, and 
therefore the flow of the fluid in the circumference becomes smoother, so 
that it becomes possible to reduce the disorder of the flow of fluid. 
FIG. 10 shows a cross-sectional view of the distributor-collector of [2], 
and FIG. 11 shows a cross-sectional view along the XI--XI line in FIG. 10. 
In FIGS. 10 and 11, reference numeral 4 shows an outlet-inlet, 5 the A 
surface, 6 the B surface, 7 the cavity (in this case, a spacer having 
voids is used to form the cavity), 8 the packed column body, and 9 
grooves. 
In this invention, a fluid charged through the inlet 4 flows rapidly 
through the grooves 9 to the circumference, overspreads from the grooves 
through the cavity 7, and flows into a packing layer. The fluid having 
passes through the packing layer flows, via the A surface 5, through the 
cavity 7 into the grooves 9, and is rapidly discharged from the column 
through the grooves. Since the fluid is thus rapidly and wholly 
distributed or collected, the residence time of the fluid in the 
distributor-collector is short, and moreover, the fluid flows rapidly from 
the opening of the outlet to any point on the segregating surface. 
The grooves in said distributor-collector are formed radially around the 
outlet-inlet in the B surface as a center. That is to say, the grooves are 
formed so that they gradually go away from the outlet-inlet. The grooves 
are not always linear and there may be branch grooves branched from the 
main grooves formed radially. When the cross-sectional area of the groove 
in the direction perpendicular to the longitudinal direction of the groove 
is taken as S.sub.3 (mm.sup.2) and the average distance of the cavity is 
taken as l.sub.3, S.sub.3 is preferably in the range of 100 l.sub.3.sup.2 
&lt;S.sub.3.sup.2 &lt;100(10l.sub.3 +1).sup.2. When S.sub.3 is in the range 
shown by the above formula, the residence time is particularly short, the 
inner pressure loss in the grooves decreases, the effects of the grooves 
are marked, and the separating ability of the whole packed column is 
greatly improved. 
The grooves are preferably distributed throughout the B surface as densely 
and uniformly as possible. 
The number of the grooves is not critical, but when the grooves are 
arranged so that any of them is certainly situated within a distance of 
316.sqroot.l.sub.3 (mm) from any point on the B surface, the grooves are 
wholly and uniformly distributed; therefore it is preferably. From the 
viewpoint of the residence time of the liquid in the grooves and back 
mixing, it is preferred that the total area of the grooves on the B 
surface does not exceed 40% of the area of the B surface. Although the 
form of the groove is also not critical, the cross-section at right angles 
to the longitudinal direction of the groove may be, for example, 
triangular, square or circular as shown in FIGS. 12 to 14. In particular, 
it is preferred that there is a relationship of .sqroot.S.sub.3 
.gtoreq.0.2l.sub.4 between the cross-sectional area S.sub.3 of the groove 
shown by hatching in FIGS. 12 to 14 and the circumference l.sub.4 (mm) of 
the section of the groove, because in this case, only a small loss due to 
pressure is caused and good performance characteristics can be obtianed. 
In this case, l.sub.4 is the sum of the circumference of the groove and 
the width of the groove shown by m in FIGS. 12 to 14. That is, in FIG. 12, 
l.sub.4 =m+n+o+p; in FIG. 13, l.sub.4 =m+n, and in FIG. 14, l.sub.4 
=m+n+o. 
The volume of the space in the groove is excluded from that of the cavity 
of the distributor-collector and is not counted in the calculation of the 
average distance. 
Although the packed column of this invention can also be used as a packed 
column in which a reaction is conducted with a catalyst supported on 
packings, or as a packed column for increasing the reaction surface area 
by providing packings, the characteristics of the present packed column 
can further be exhibited when used as a packed column for separating two 
or more substances by chromatography. In particular, excellent effects can 
be obtained by using the present packed column for separating, by 
chromatography, substances which have a small separation coefficient, for 
example, rare earth elements, isotopes and the like. 
The packings used in the packed column of this invention may be in various 
forms such as spherical form, powdery form, glanular form, ground form, 
fibrous form and the like. Examples of the packings include various 
materials in the gel state such as silica gel, activated alumina, metal 
hydroxides, polystyrene gels and the like; various fibrous materials such 
as cellulosic ion-exchange fibers; active carbon; zeolite; molecular 
sieves; ion-exchange resins; and materials obtained by supporting on the 
above-mentioned materials various catalysts such as metals, metal oxides 
and the like or various organic solutions; and packings obtained by mixing 
the above-mentioned materials with various short fibers. 
The packed column of this invention parmits chromatography at a high flow 
rate with almost no increase in the disorder of flow of the moving phase 
fluid, and hence has a very high industrial value. 
EXAMPLE 1 
A pressure-absorbing mechanism made of SUS shown in any of FIGS. 15 to 21 
was installed at the middle, namely a height of 0.9 m from the bottom, of 
a jacketed column having an inside diameter of 30 cm and a height of 1.8 
m, as shown in FIG. 1. Further, distributor-collectors as shown in FIG. 8 
were installed on the input and output sides of the packed column. In 
these distributor-collectors, the radius of the cavity was 15 cm, the 
radius of a part where the A and B surfaces were parallel to each other 
was 7.5 cm, the distance between the A and B surfaces in said part was 2.5 
mm, the distance in the circumference of the cavity was 0.5 mm, and 
k=0.016. As the A surface, a Teflon nonwoven fabric reinforced with a 
porous plate was used. Into the packed column was charged from the upper 
part a cation exchange resin composed of sulfonation product of 
styrene-divinylbenzene copolymer which has been classified using 100 to 
200 mesh. The crosslinking degree of the cation-exchange resin was 20. 
Subsequently, 900 liters of a surfuric acid solution having a concentration 
of 0.5 mol/liter was supplied from the upper part of the packed column to 
convert the cation-exchange resin into its hydrogen ion form. The packed 
column was mainteined at 95.degree. C., and a solution containing 7.5 
mmols/liter of neodymium, 7.5 mmols/liter of praseodymium and 15 m 
mols/liter of EDTA which had been adjusted to pH 3 was supplied from the 
upper part of the packed column while heating the same at 95.degree. C. 
This supply was continued until the width of adsorption band of the rare 
earth element ions reached 120 cm. 
Thereafter, an EDTA solution having a concentration of 15 mmols/liter was 
supplied to develope and shift the adsorption band of the rare earth 
element ions. The supply speed of the solution during this procedure was 
as shown in Table 1 so that the pressure loss was near the pressure 
resistance of the packed column of 15 kg/cm.sup.2. A part of the solution 
effluent from the lower part of the packed column was continuously 
collected, and divided into fractions of 15 ml, and the amounts of 
neodymium and praseodymium in the fractions were determined by fluorescent 
X-ray analysis. 
The amount of praseodymium obtained per unit time (Pr yield) was calculated 
by dividing the yield of praseodimium having a purity of 99.9% or higher 
by the time required for the development. The results were shown in Table 
1. 
TABLE 1 
______________________________________ 
Speed of 
Form of constituent 
developing 
Run of pressure-absorb- 
solution Pr yield 
No. ing mechanism (liter/min) 
(mol/hr) 
______________________________________ 
1 FIG. 15 10.9 1.18 
2 FIG. 16 9.5 1.07 
3 FIG. 17 10.0 1.01 
4 FIG. 18 8.8 0.96 
5 FIG. 19 14.5 1.43 
6 FIG. 20 10.2 1.04 
7 FIG. 21 9.8 1.13 
______________________________________ 
COMATIVE EXAMPLE 1 
The same cation-exchange resin as in Example 1 was packed into the same 
column as in Example 1, except that the pressure-absorbing mechanism was 
not installed therein, and praseodymium was separated by the same 
procedure as in Example 1. The speed of a developing solution was 5.8 
liters/min and the Pr yield was 0.74 mol/hr. 
EXAMPLE 2 
A pressure-absorbing mechanism having a section shown in any of FIGS. 22 to 
26 was installed in the form of a drainboard as shown in FIGS. 1 and 2 at 
the middle of a column having an inside diameter of 700 mm.0. and a height 
of 2 m, or a pressure-absorbing mechanism having a section as shown in 
FIG. 27 or FIG. 28 was installed at said middle in the form of a lattice 
as shown in FIG. 5. Further, distributor-collectors having grooves as 
shown in FIG. 10 or FIG. 11 were installed on the input and output sides 
of the packed column. The grooves had a linear form and were arranged 
radially at a pitch of 7.5.degree., and the number of the grooves was 48. 
The grooves had a width of 6 mm and a depth of 4 mm within a distance of 
26 cm from the outlet-inlet and had a width of 4 mm and a depth of 4 mm at 
a distance therefrom of 26 cm to 34 cm. As the A surface, a Teflon cloth 
was used, and a wire gauze of 20 mesh was inserted in order to form 
spaces. In this case, the radius of the cavity was 35 cm, the distance in 
the cavity was 1 mm, and k=0.006. The following investigation was made for 
the packed column in each of the cases described above. 
The above-mentioned column was packed with packings prepared by mixing a 
short fiber obtained by cutting carbon fibers having a diameter of 7 .mu.m 
into 1.0 mm in a proportion of 30% by weight with an anion-exchange resin 
of vinylpyridine-divinylbenzene copolymer having a crosslinking degree of 
15% and a particle diameter of 100 to 200 mesh. Subsequently, a 1 N 
hydrochloric acid solution was passed through the packed column to 
condition the packings, after which 100 ml of a sodium chloride solution 
having a concentration of 2 mols/liter was nomentarily poured into the 
column through a liquid-supplying inlet installed just before the column 
inlet while continuing the passing of a 1 N hydrochloric acid solution at 
a rate of 38.2 liters/min. The solution effluent from the column outlet 
was collected, and divided into fractions of 1 liter, and the sodium 
concentration in each of the fractions was measured by means of an atomic 
absorption analyzer. 
On the basis of the values thus measured, the amount of the effluent 
solution was plotted on the abscissa and the sodium concentration was 
plotted on the ordinate whereby a pulse wave was obtained. The pulse width 
at a height of a half of the peak height (half-width) of the pulse was 
measured, and used as an index of the disorder of flow of the moving phase 
passing through the packing layer. The maximum flow rate was measured at a 
pressure loss of 20 kg/cm.sup.2 in the case where each pressure-absorbing 
mechanism was installed. 
The results are shown in Table 2. 
TABLE 2 
______________________________________ 
Form of constituent 
Half- Maximum 
Run of pressure-absorb- 
width flow rate 
No. ing mechanism (liter) (liter/min) 
______________________________________ 
1 FIG. 22 35.8 265 
2 FIG. 23 36.1 308 
3 FIG. 24 35.2 242 
4 FIG. 25 35.2 223 
5 FIG. 26 35.4 219 
6 FIG. 27 35.3 285 
7 FIG. 28 35.1 300 
______________________________________ 
COMATIVE EXAMPLE 2 
The same ion-exchange resin and the same short fiber as in Example 2 were 
packed into the same column as in Example 2 except that the 
pressure-absorbing mechanism was not installed therein. Evaluation was 
carried out by the same method as in Example 2 to find that the half-width 
of the pulse was 35.2 l and that the maximum flow rate was 184 
(liters/min). 
EXAMPLE 3 
The same procedure as in Example 2 was repeated, except that the dimensions 
for a pressure-absorving mechanism having a section as shown in FIG. 19 
were widely varied as shown in Table 3. 
TABLE 3 
______________________________________ 
Circum- Length Maximum 
ference in flow Half- flow 
Run ratio direction 
Shielding 
width rate 
No. (cm.sup.-1) 
(cm) degree (liter) 
(liter/min) 
______________________________________ 
1 0.12-0.13 25 0.05 37.0 196 
2 0.4-0.5 2.5 0.3 36.2 224 
3 0.4-0.5 10 0.3 35.4 301 
4 0.8-1.2 5 0.3 34.9 285 
5 2-3 3 0.5 35.8 265 
6 8-12 1 0.7 36.2 241 
7 8-12 1 0.85 37.3 206 
______________________________________ 
In the case of Run Nos. 1, 2 and 7, the circumference ratio, the length in 
the flow direction and the shielding degree were outside the respective 
ranges of this invention, and the half-width increased, while the maximum 
rate decreased. 
EXAMPLE 4 
The performance characteristics of the same packed column as in Example 1 
was evaluated, except that a pressure-absorbing mechanism as shown in FIG. 
29 or FIG. 30 was installed therein, to obtain the results shown in Table 
4. 
TABLE 4 
______________________________________ 
Speed of develop- 
Run Form of pressure- 
ing solution Pr yield 
No. absorbing mechanism 
(liter/min) (mol/hr) 
______________________________________ 
1 FIG. 29 11.0 0.94 
2 FIG. 30 13.3 0.84 
______________________________________ 
In the case of Run No. 2, there was used a pressure-absorbing mechanism in 
which no passage space exists within 1 cm from any position on the upper 
and lower sides of the solid part, and the Pr yield decreased. 
EXAMPLE 5 
Zeolite (60 to 100 mesh) was packed into the same column as in Example 2, 
except that a pressure-absorbing mechanism as shown in FIG. 27 was 
employed therein. 
The column packed with the zeolite was maintained at a temperature of 
100.degree. C. Toluene was first supplied to the column to condition the 
zeolite, after which as a material to be separated, a mixture of C.sub.6 
-compounds consisting of 50% by weight of benzene, 32.5% by weight of 
cyclohexene and 17.5% by weight of cyclohexane was supplied by means of a 
measuring pump to form an adsorption band of the mixture of C.sub.6 
-compounds. Thereafter, toluene was again supplied to the column at a 
constant flow rate of 45 liters/min to develop the adsorption band of the 
mixture of C.sub.6 -compounds. The eluate from the bottom of the column 
was collected, and divided into fractions of 1 to 10 liters. Quantitative 
analysis was carried out for the percentages by weight of benzene, 
cyclohexene, cyclohexane and toluene in the sample solutions thus 
collected, by gas chromatography. 
A solution rich in cyclohexene and cyclohexane was recovered in the 
vicinity of the front-end interface of the adsorption band of C.sub.6 
-compounds in relation to the flowing direction of the eluate, and a 
solution rich in benzene was recovered in the vicinity of the rear-end 
interface. The weight of benzene contained in the fraction in which the 
purity of the benzene in relation to the mixture of C.sub.6 -compounds, 
which is a measure of separation efficiency, was 99% or higher was 57.1 
kg. 
EXAMPLE 6 
The same separation procedure as in Example 5 was repeated, except that the 
distance between the A and B surfaces was 0.5 mm. In this case, the weight 
of benzene contained in the fraction in which the purity of the benzene 
was 99% or higher was 52.1 kg. The distributor-collector of the packed 
column used in this case had a k value of 0.003 (the performance of the 
distributor-collector was inferior). 
COMATIVE EXAMPLE 3 
The same separation procedure as in Example 5 was repeated, except that the 
pressure-absorbing mechanism was omitted. In this case, the yield of 
benzene was 39.4 kg. 
EXAMPLE 7 
Zeolite (60 to 100 mesh) was packed into the same column as in Example 1, 
except that a pressure-absorbing mechanism as shown in FIG. 19 was used. 
The column packed with the zeolite was maintained at a temperature of 
100.degree. C. Toluene was first supplied to the column to condition the 
zeolite, after which as a material to be separated, 42.1 liters of a 
mixture of C.sub.6 -compounds consisting of 50% by weight of benzene, 
32.5% by weight of cyclohexene and 17.5% by weight of cyclohexane was 
supplied by means of a measuring pump to form an adsorption band of the 
mixture of C.sub.6 -compounds. Thereafter, toluene was again supplied to 
the column at a constant flow rate of 8.4 liters/min to develop the 
adsorption band of the mixture of C.sub.6 -compounds. The eluate from the 
bottom of the column was collected, divided into fractions of 0.25 to 2.5 
liters. The weight percentages of benzene, cyclohexene, cyclohexane and 
toluene in the sample solutions thus obtained was quantitatively analyzed 
by gas chromatography. 
A solution rich in cyclohexene and cyclohexane was recovered in the 
vicinity of the front-end interface of the adsorption band of C.sub.6 
-compounds in relation to the flowing direction of the eluate, and a 
solution rich in benzene was recovered in the vicinity of the rear-end 
interface. The weight of benzene contained in the fraction in which the 
purity of the benzene in relation to the mixture of C.sub.6 -compounds was 
99% or higher was 8.31 kg. 
EXAMPLE 8 
The same separation procedure as in Example 7 was repeated, except that the 
distances between the A and B surfaces were 6.5 mm in the part where the 
surfaces were parallel to each other and 0.6 mm in the circumference. In 
this case, the yield of benzene was 7.84 kg. 
The distributor-collector of the packed column used in this case had a k 
value of 0.041 (the performance of the distributor-collector was 
inferior). 
COMATIVE EXAMPLE 4 
The same separation procedure as in Example 7 was repeated, except that the 
pressure-absorbing mechanism was omitted. In this case, the yield of 
benzene was 6.57 kg.