Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
V~'7~;
The present invention relates to a process for the
regeneration of anion and cation exchange resins which are used
in a mixed condition,
It is known to employ a mixed bed deionizing process
using a mixture of an anion exchange resin and a cation
exchange resin for producing a deionized water. The mixed
bed deionizing process comprises a back-washing separation
step for separating the anion exchange resin from the cation
exchange resin using a water flow from the bottom of the resin
column; a regeneration step for regenerating respectively the
separated anion exchange resin and the cation exchange resin
with an acid and a base; a washing step for washing out the
regenerant with wash water and a mixing step for mixing the
~, regenerated resins.
In the back-washing separation step, the resins are ~ --
separated based upon the difference of specific gravities of
the resins and the difference of the particle diameters of the
resins. However, at the boundary of the separated resins,
small amounts of both of the resins are mixed and the complete
separation can not be easily attained. The incomplete separ-
ation of both of the resins causes a decrease in the regener-
ative efficiency of the regenerant in the next regeneration
step, a decrease of the exchange capacity of the ion exchange
resins and a decrease of the quality of the deionized water
after the regeneration. ~ -
Recently, the condensed water in a high pressure
' boiler of a fossile fuel power station or an atomic power
station has been purified by deionizing with a mixed bed
comprising a hydroxyl type (OH type) strong basic anion
exchange resin and an ammonium type (NH4 type) strong acidic
cation exchange resin. However, in the regenerations of the
ion exchange resins, complete separation of the ion exchange
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V3'~6~
resins could not be attained and for example, the ion exchange
resins are separated with mixing a small amount of the cation
exchange resin in the layer of the anion exchange resin near
the lower boundary. When the anion exchange resin containing
the small amount of the cation exchange resin is regenerated
with sodium hydroxide by the conventional process, a small
amount of sodium type cation exchange resin is included in the
I OH type anion exchange resin.
In the ammonium type mixed bed process, ammonia is
added to adjust the pH of the condensed water which is recycled,
whereby sodium ions adsorbed on the contaminated cation ex-
change resin are eluted by ammonium ions. For example, when
1% of the sodium type cation exchange resin is incorporated,
about several tens ppb (parts per billion) of sodium ions are
eluted. The presence of sodium ions in the condensed water
causes corrosion of the boiler because of the alkaline
corrosion. Accordingly, it is preferable to prevent the
; contamination of sodium ions as far as possible.
The present invention provides a process for a
regeneration of mixed anion and cation exchange resins by a
simple operation without a decrease of the regenerative
efficiency of the regenerant, a decrease of the exchange
capacity of the ion exchange resins and a decrease of the
~- quality of the deionized water.
According to the present invention there is provided
a process for regenerations of an anion exchange resin and a
cation exchange resin used for deionizing water in the form
of a mixed resins, the improvement which comprises separating
the anion exchange resin and the cation exchange resin as the
upper and lower layers by back-washing the mixed resins with
water and discharging a middle layer containing non-separated
i resins at the boundary between the upper and lower layers, and
,
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~080376
charging the discharged middle layer in a step before the back-
washing step in a subsequent regeneration process.
Thus in accordance with the present invention
regeneration has been effected by back-washing the mixed anion
and cation exchange resins to separte them as an upper layer,
a middle layer and a lower layer and regenerating respectively
the upper layer and the lower layer and mixing the separated
middle layer of the mixed resins in a step before the back-
washing step in a subsequent regeneration process.
When the mixed anion and cation exchange resins are
separated by the back-washing separation, the anion exchange
resin and the cation exchange resin are respectively in the
pure condition depending upon the distance from the boundary
between both of the resins whereby the mixed anion and cation
exchange resins are separated into three layers of the pure
anion exchange resin layer, the mixed resin layer and the pure
cation exchange resin ~ayer. When the three layers are treat~d
by the specific process, the deionization and the regeneration
can be smoothly attained.
In the present invention, when the anion exchange
resin and the cation exchange resin used for the deionization
in the form of the mixed resins, are regenerated, the anion
and cat~on exchange resins are separated by the back-washing
and the middle layer of the mixed resins adjacent the boundary
between both of the resins is discharged out of the system,
and it is added to a step before the back-wa~hing step in a
subsequent regeneration process.
Thus when the mixed anion and cation exchange resins
used in the deiDnization are separated by the back-washing
separation, the anion exchange resin is separateddas the upper -~
layer and the cation exchange resin is separated as the lower
layer and the mixed resins remain as the middle ~ayer. When
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~0~3376
the resins are treated by feeding the back-washing water at
constant flow velocity, the resin layers are separated in the
form of the suspension with stable layers of the resins under
back-washing to discharge them with the upward flow.
In the process of the present invention, after the
resins are separated under said conditions, the anion exchange
resin layer is discharged through an upper layer resin trans-
ferring pipe disposed at the upper position in the column with
upward flow water or downward flow water after settling the
resins. Then, the middle layer of the mixed resins is dis-
charged through a mixed resin transferring pipe disposed
adjacent the boundary between both of the resin layers with
water. The lower layer of the cation exchange resin is
regenerated in the column or discharged from the bottom the
column to separate the three layers.
The three layers in the condition of the suspension
due to ~he back-washin~ sepLaration can be also separated by
~.
sequentially discha~ging the lower layer of the cation exchange
resin layer, the middle layer of the mixed resins and the
upper layer of the anion exchange resin through a resin
transferring pipe disposed at the bottom of the column.
It is also possible to treat them as follows.
The resins separated into three layers by the back-washing are
sedimented in three separated condition after finishing the
back-washing. The upper layer of the anion exchange resin is
`~ discharged together with the downward flow from the upper part
of the column, through a resin transferring pipe disposed at
suitable position in the upper part of the column. The middle
layer of the mixed resin is discharged together with the
downward flow fed from the upper part of the column~ through
a mixed resin transferring pipe. The lower layer of the
cation exchange resin can remain in the column or be discharged
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i3'76
from the bottom thereof,
The amount of the middle layer of the mixed resins
discharged depends upon the condition of the resin particles
and the back-washing method, and it is usually in a range of
3 to 50 wt. % preferably 5 to 20 wt. % to total resins. The
middle layer of the mixed resins discharged before the first
regeneration is added to the mixed resins before the back-
; washing separation in the next or following regeneration
process.
The pure anion exchange resin and the pure cation
exchange resin which are respectively separated from the
middle layer of the mixed resins, are respectively regenerated
with a base or an acid, and then, the regenerants (base or -
acid) are respectively removed by washing with water and the -
resins are mixed and used for the deionization of water. In
such a case, the amount of the resins is decreased for the
amount of the discharged middle layer of the mixed resins.
: Accordingly, new resins corresponding to the discharged middle
layer of the mixed resins are added.
The mixed resins obtained by the deionization are
separated by the back-washing separation with water before the
second regeneration process. The back-washing separation is
carried out after adding the separated middle layer of the
mixed resins discharged before the first regeneration process.
As the same manner, in the third or following re-
generation processes, the middle layer of the mixed resins
separated by the back-washing separation in the previous
regeneration process is added in a step before the back-washing
separation in the following regeneration process.
The ion exchange resins are slightly broken by
repeating the regeneration process whereby the pulverized
particles are accumulated in the middle layers. Accordingly,
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the pulverized particles can be removed by a classification
of the particles such as a sieving operation for the middle
layer of the mixed resins.
In accordance with the process of the present
invention~ the anion exchange resin and the cation exchange
resin can be regenerated after the complete separation in the
back-washing separation after the deionization whereby the
regenerants can be effectively used and the ion exchange
capacity of the ion exchange resins is not deteriorated and
the quality of the deionized water is not deteriorated to
obtain the deionized water having high purity. When they are
used for the deionization of the condensed water in the high
pressure boiler for a power station, the deionized water having
high purity can be obtained because of no contamination of the
sodium type anion exchange resin. :
, When hydrazine or the other compound is used instead
~. ~
of ammonia for adjusting pH of the condensed water, the -~
desired result as that of the use of ammonia can be attained.
. ~ .
The present invention will be further illustrated
~ 20 by way of the following Examples.
I Example 1
In a column having a diameter of 8 cm and a height
of 150 cm, 2 liters of strong acidic cation exchange resin -
(supplied under the Trademark Diaion SKlBL by Mitsubishi Chem.
- Industries Ltd.) (hereinafter referred to as SKlBL) and 1
liter of strong basic anion exchange resin (supplied under
the Trademark Diaion SA 10 AL by Mitsubishi Chemical Industries
Ltd,) (hereinafter referred to as SAlOAL) were charged and
thoroughly mixed.
The particle size distributiolls of these resins
~' are shown in Table 1.
~ ..
~ 6
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.- . . .
,' 1
:
10~ 76
Table 1
Particle diameter SKlBL SAlOAL
more than 840,c~ 27. 9 % 4 . 7 %
840 to 590~ 57.1 % 55.4 %
590 to 420,~ ' 14. 8 % 39. 7 %
les s than 42 0~ O . 2 % O . 2 %
: -
Three resin transfer pipes having a diameter of 8 mm
were disposed at the positions of 48 cm, 53 cm and 58 cm from
the bottom of the column.
Deionized water was fed to flow in an upward current
at a linear velocity (L~ of 10 m/hr. at 20 + 1C from the
bottom of the column for 45 minutes to back-wash the resin.
The resin SA 10 AL separated as the upper layer was discharged
through a resin transfer pipe disposed at the position of
58 cm from the bottom during the back-wash. Then, the mixed
resin as the middle layer was discharged throush a resin
transfer pipe disposed at the position of 4 8 cm from the
bottom. The amounts and components in the upper layer, the
middle layer and the lower layer of the separated resins in
the column were as shown in Table 2.
Table 2 . -
.'' ' , .. ' .
_ Volume of Components of resins
resin (Volume %)
(llter) SK lBL I SA loAL
upper layer O. 88 less than ~ more than 99. 9
___ .
middle layer O . 31 61. 3 3 8. 7
.... _ ,
lower layer ~11
~ 7
.
.
Reference l
In accordance with the process of Example l, the mixed
resins having the same components were washed by the back-wash
and the separated upper layer was discharged through the resin
transfer pipe disposed at the position of 53 cm from the bottom
of the column as the conventional process. The results are
shown in Table 3.
Table 3
. j -
Volume of resin Components of resin
. (liter) (Volume %)
! SK 1 l~L S~ 1 Ol~L
_
upper layer O . 97 1. 3 98. 7
lower layer 2 . 03 97. 9 1 2.1 . ~-
Ex~mple 2
In accordance with the process of Example l using the
same resins and the same column, deionized water was fed to
flow in an upward current at a linear velocity of 7 m/hr. at
20 + 1C from the bottom of the column for 30 minutes to back-
wash the resin. The resin SAlOAL separated as the upper layer
was discharged through the resin transfer pipe disposed at the
position of 53 cm from the bottom under the back-wash. Then,
the back-wash was continued at the linear velocity of 13-m/hr.
for lO minutes and the resin of the middle layer was discharged
through the resin transfer pipe disposed at the position of
53 cm from the bottom.
The amounts and components in the upper layer~ the
middle layer and the lower layer of the separated resins in
the column were as shown in Table 4.
.- 8 -
Table4
._ _ _ .
Volume ofresin Components ofresins
(liter) (Volum~ %) _._
__ _ SKlBL SA1OAL
upperlayer ~.89 lessthan morethan
. middlelayer 0.24 54.2 45.8
lowerlayer 1.87 1 morethan O 1 ~:
Example 3 -.-- -
In an acrylic resin column having a diameter of 8 cm
and a length of 150 cm equipped with three resin transfer pipes,
2.0 liters of strong acidic cation exchange resin (Diaion
SKlBL) and 1.0 liter of strong basic anion exchange resin
(Diaion SAlOAL~ were charged and mixed and used in the follow-
: ing first to seventh steps. ~ -
. ~irst step: Deionized water was fed to flow in an -
upward current at a linear velocity of 10 m/hr. at 20 - l~C
from the bottom of the column for 20 minutes to back-wash and
the separated upper layer of the resin SAlOAL was discharged
. 20 through the upper resin transfer pipe at the position of 58 cm
from the bottom and transferred to an anion regeneration.column. .
Second step: The mixed resins as the middle layer
was discharged through the lower resin transfer pipe at the
position of 48 cm from the bottom,
Third step: The mixed resins as the middle layer
discharged in the second step were sieved in the wet condition
with a sieve at 297 ~ (3apanese Industrial Standard).
~ourth step: The resin transferred to the anion
regeneration column and the residual resin the column were
respectively regenerated with 4 liters of 4% aqueous solution
of sodium hydroxide and 8 liters of 4% aqueous solution of
sulfuric acid during 1 hour. Then, a deionized water was
~ 9 ,.
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108~)376
passed at a rate of 30 liter/hr. and 60 liter/hr, for 1 hour
to wash the resins,
Fifth step: The resin in the anion regeneration
column obtained by regenerating and washing with water was fed
into the main column and a compressed air was fed from the
bottom of the column for 10 minutes to mix the regenerated
anion and cation exchange resins.
Sixthstep: Water was filled to cover the resin and
an aqueous solution containing 7.1 ppm of NaCQ (as CaCO3) and
1.52 ppm of ammonia (as CaCO3) at pH of 9.2 was passed at a
rate of 300 liters/hr. for 4 hours. -
Seventh step: The resins in the middle layer from
which fine particles of the resins were removed in the third
step were mixed with the resins in the column treated in the
-, sixth step.
The first to seventh steps were repeated for five
times. The total amount of the resins removed in the third
step was 9.7 mQ.
Example 4
The anion and cation exchange resins of Example 3 were
, used and water (pH of 9.2) prepared by adding 1.52 ppm (as
CaCO3) of ammonia to a deionized water containing 0.02 ppm of
sodium ions and an electric conductivity of less than 0.1 ~/cm,
was fed at a rate of 300 liters/hr. After 150 hours, the
deionized water treated had an electric conductivity of 0.14
~v/cm and a concentraton of sodium ions of 2.3 ppb.
Reference 2
The first to seventh steps of Example 3 were modified
as follows, In accordance with the conventional process, the
anion exchange resin as the upper layer was discharged through
the resin transfer pipe at the position of 53 cm from the
bottom and the anion and cation exchange resins were regenerated
-- 10 --
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-, ..
10~(~376
and mixed. Then, as the process of Example 3, the water
containing ammonia was passed. After 150 hours, the deionized
water treated had an electric conductivity of 0.21 ~v/cm and
a concentration of sodium ions of 12 ppb.
First step: A deionized water was fed to flow in
an upward current at a linear velocity of 10 m/hr. at 20 - 1C
for 20 minutes to back-wash and then, the resin in the upper
layer was discharged through the resin transfer pipe at the
~; position of 53 cm from the bottom and transferred to the anion
regeneration column.
Second and third steps: None.
Fourth, fifth and sixth steps: The treatments being
the same with those of Example 3.
Seventh step: None.
, The deionized water obtained by the process of Example
4 had an electric conductivity of 0.14 ~/cm and a concentration
of sodium ions of 2.3 ppb whereas in Reference 2 as the
. conventional process, a deionized water had an electric
conductivity of 0.21 ~/cm and a concentration of sodium ions
of 12 ppb. In accordance with the present invention, the
deionized water having a content of sodium ions 1/5,2 to that
r of the conventional process could be obtained,
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