DowLiquid Separations

DOWEX HCR-SIon Exchange Resin

ENGINEERING INFORMATION

Lenntechinfo@lenntech.com Tel. +31-152-610-900www.lenntech.com Fax. +31-152-616-289

DOWEX HCR-S Strong Acid Cation Exchange Resin

General InformationDOWEX* HCR-S strong acid cationexchange resin is produced by thesulfonation of a styrene divinyl-benzene copolymer of controlledsize distribution.

The resin features a highcapacity with a porosity to assurean exemplary kinetic behavior. Itexhibits good physical, chemicaland thermal stability. These charac-teristics make it the resin of choicefor most water treatment applica-tions. DOWEX HCR-S resin is usedin softening as well as single ormixed bed demineralization.

* Trademark of The Dow Chemical Company

In addition to the standardgrade, DOWEX HCR-S MB (H) andDOWEX HCR-S PS are speciallygraded resins for use in mixed bedand counter-current regenerationapplications respectively. DOWEXHCR-S D (H) is a dark colored resindesigned to give good opticalseparation when used in a mixedbed.

This brochure relates to waterdemineralization, using HCl orH2SO4 as regenerants in co-currentor counter-current operations. Thepresented data allows the calcula-tion of operational capacities and

sodium leakages for different waterqualities at different temperaturesand levels of regeneration. Sepa-rate information is available on itsuse in softening applications.DOWEX HCR-S resin is delivered ineither the sodium form or thehydrogen form.

In cases where physical stabilityis of major concern, premiumquality DOWEX HGR resin isavailable. This resin exhibits superi-or stability under stringent chemicalor physical conditions of operation.

Typical Physical and Chemical PropertiesIonic form as delivered Na+ H+

Total exchange capacity, min. eq/l 2.0 1.8kgr/ft3 as CaCO3 43.7 39.3

Water content % 44 - 48 50 - 56Bead size distribution

range mm 0.3 - 1.2 0.3 - 1.2>1.2 mm, max. % 5 5

HydraulicCharacteristicsBackwash ExpansionUnder the upflow conditions ofback-washing, the resin will expandits volume (see Figure 1). Suchexpansion allows the regrading ofthe resin, fines removal and avoidschanneling during the subsequentservice cycle. At the same time,accumulated particulate contamina-tion is removed. An efficient back-wash will require an expansion ofover 50% of the original resinvolume and up to 80-100% expan-sion is common.

In co-current operation, the resinis backwashed for a few minutesbefore every regeneration. Occa-sionally, a longer backwash may beneeded to fully remove contami-nants.

In counter-current operation thestrainers are cleaned by the regen-erant flow. To retain the advantagesof counter-current operation it isessential not to disturb the resin.Backwashing is only desirable ifaccumulated debris causes anexcessive increase in pressure dropor to decompact the bed. Usually, abackwash is performed every 15 to30 cycles in conventional counter-current regeneration systems.

Pressure Drop DataThe pressure drop through a resinbed primarily depends on the beddepth and the flow velocity of thewater. It is further influenced by theparticle size distribution of the resinand by the viscosity, and thustemperature, of the water. The datain Figure 2 shows the pressure dropper unit bed depth at various flowrates flow velocity for the standardgraded resin (0.3-1.2 mm). Anequation is also supplied which canbe used for temperature compensa-tion. These figures must be consid-ered representative only. The totalhead loss of a unit in operation will

Figure 1. Backwash expansion data

also depend on its design and issubstantially affected by the contri-

bution of the strainers surrounded byresin.

0

20

40

60

80

100

120

0 5 10 15 20 25 30m/h

Linear Flow Rate

0 2 4 6 8 10 12

H+ FormNa+ FormCa++ Form

gpm/ft2

Perc

ent E

xpan

sion

m/hLinear Flow Rate

Form H+Form Na+Form Ca++

For other temperatures use:FT = F25C [1+0.008 (1.8TC - 45)], where F = m/hFT = F77F [1+0.008 (TF - 77)], where F = gpm/ft2

Temperature = 25C (77F)

Figure 2. Pressure drop data

For other temperatures use:PT = P20C / (0.026TC+0.48), where P = bar/mPT = P68F / (0.014TF+0.05), where P = psi/ft

gpm/ft2

Temperature = 25C (77F)

Perc

ent E

xpan

sion

m/hLinear Flow Rate

psi/f

t

OperatingCharacteristicsThe engineering design of an ionexchange unit will depend on anumber of factors such as feedwater composition, desired capacityand water quality, and operationalconditions. The following informa-tion considers these factors andallows a design to be made.

The performance of the cationexchange resin will be evaluated onthe basis of the regenerationefficiency and the sodium leakage.Figure 3 indicates the contributionto conductivity due to sodiumleakage. This leakage is expressedas NaOH as it appears in theeffluent of a strong base anionresin. When a weak base resinfollows the cation exchange unit,sodium will leak as NaCl and contri-bute to the conductivity accordingly.In this case, conductivity will alsobe due in part to CO2, which shouldalso be taken into account.

Sodium leakage will affect theconductivity of the final effluent andalso influence the silica leakagefrom a strong base anion resin.

Data related to this influence ispresented in the engineering leaf-lets of the corresponding anion ex-change resins. Silica leakage andconductivity are the important featu-res of the final demineralized water.The correct design of the cationexchange unit will therefore have acritical impact on the overall per-formance and the ion exchangeplant.

When H2SO4 is used as regener-ant, the permitted concentration ofH2SO4 is determined by the percent-age of calcium in the feed water(see Figure 4). If the regenerant con-centration is too high or the regen-eration is performed too slowly, cal-cium sulfate will be deposited in theresin bed.

Step-wise regeneration may beused to improve the regenerationefficiency. As this applies especially

Figure 3. Na leakage expressed as conductivity at 25C (77F) after anion exchange

Figure 4. Permitted H2SO4 concentration

Figure 7. Average Na leakage from DOWEX HCR-S resin in co-current operation with H2SO4 as regenerant

to high regeneration levels, it may bemore attractive to use counter-current techniques in such cases.Concentrations of sulfuric acidrecommended for step-wise regen-eration are given in Figure 5. It iscommon to operate the first step atlow acid concentration and highflow rates. Operation in this fashionreduces the risk of calcium precipi-tation in the bed. It also makes itpractical to use a single speed acidpump. (The acid concentration iscontrolled by changing the volumeof dilution water used). At a presen-tation rate of 3 g H2SO4/min per literof resin at a concentration of 1%H2SO4, this will amount to a regen-erant flow rate of 18 m3/h per m3 ofresin (2.2 gpm/ft3).

Hydrochloric acid may be usedat concentrations of 4 to 8% irre-spective of the calcium content inthe feed water. High concentrationsof HCl and long regeneration timeswill be preferred when calcium andmagnesium predominate. Whensodium is the main constituent, HClat 4 to 5% will give the best efficien-cy.

Co-Current OperationFigures 6 and 7 show averagesodium leakage from DOWEX HCR-Sresin at different regeneration levelsusing HCl or H2SO4 as regenerants.These leakag es are expressed aspercentages of equivalent mineralacidity (EMA). Leakage levels will behigher at the beginning and towardsthe end of the service cycle. Whenvery high regeneration levels arerequired to obtain the desiredleakage, it is advisable to considercounter-current operation. Data ontypical operational capacities forDOWEX HCR-S using HCl or H2SO4are given in Figures 8 and 9.

Figure 5. Permitted H2SO4 concentration (step-wise)

Regeneration Level, lbs H2SO4/ft3 resin2.5 5 7.5

Calcium % in feed water H2SO4 % permitted

Ca% < 15 H2SO4 3%15 < Ca% < 50 H2SO4 1.5% for 30%

3% for 70%50 < Ca% < 70 H2SO4 1.5% for 50%

3% for 50%Ca% > 70 H2SO4 1% or use HCl

Aver

age

Na L

eaka

ge (a

s % of

EMA

)

Regeneration Level, kg H2SO4/m3 resin

20

16

12

8

4

0

Figure 6. Average Na leakage from DOWEX HCR-S resin in co-current operation with HCl as regenerant

2.5 5 7.5Regeneration Level, lbs HCI/ft3 resin

Aver

age

Na L

eaka

ge (a

s % of

EMA

)

Regeneration Level, kg HCI/m3 resin

Figu

re 8

. Co

-cur

rent

ope

ratio

nal c

apac

ity d

ata

Co-c

urre

nt o

pera

tiona

lca

paci

ty d

ata

(Step

-wise

conc

entra

tion i

n H2S

O 4re

gene

ratio

n)In

stru

ctio

ns:

1.Lo

cate

a p

oint

on

the

ordi

nate

of

grap

h A

from

per

cent

sod

ium

and

perc

ent a

lkalin

ity.

2.Tr

ansf

er th

e or

dina

te p

oint

from

grap

h A

horiz

onta

lly to

gra

ph B

and

follo

w th

e gu

idelin

e to

loca

te a

new

poin

t on

the

ordi

nate

acc

ordi

ng to

the

perc

ent m

agne

sium

.3.

Tran

sfer

the

ordi

nate

poi

nt fr

omgr

aph

B ho

rizon

tally

to g

raph

C a

ndre

peat

the

proc

edur

e un

der p

oint

2ac

cord

ing

to ch

osen

rege

nera

tion

1.5

1.4

1.0

0.6

1.2

0.8

leve

l. Re

ad o

ff th

e op

erat

iona

l ca-

pacit

y on

the

right

han

d sid

e of

the

diag

ram

corre

spon

ding

to th

is ne

wor

dina

te.

160

140

120

100

8060

50kg

H2S

O 4/m

3 re

sin

108.

757.

56.

255

3.75

3.1

lbs

H 2SO

4/ft3

resin

Rege

nera

tion

Leve

l

Figu

re 9

. Co

-cur

rent

ope

ratio

nal c

apac

ity d

ata

Co-c

urre

nt o

pera

tiona

lca

paci

ty d

ata

(HCI

rege

nerat

ion)

Inst

ruct

ions

:1.

Loca

te a

poi

nt o

n th

e or

dina

te o

f

grap

h A

from

per

cent

sod

ium

and

perc

ent a

lkalin

ity.

2.Tr

ansf

er th

e or

dina

te p

oint

from

grap

h A

horiz

onta

lly to

gra

ph B

and

follo

w th

e gu

idelin

e to

the

chos

en

rege

nera

tion

level

thus

esta

blish

inga

new

ord

inat

e.3.

Read

off

oper

atio

nal c

apac

ity o

nth

e rig

ht h

and

side

of th

e dia

gram

corr

espo

ndin

g to

this

new

ordin

ate.

1.9

1.3

1.7

1.5

1.1

0.9

0.7

30%

0%

120

100

8060

40kg

HCl

/m3

resin

7.5

6.25

53.

752.

5lb

s HC

l/ft3

resin

Rege

nera

tion

Leve

l

Counter-Current OperationThe advantages of counter-currentoperation over co-current operationare well-known to be improvedchemical efficiency (better capacityusage and decreased regenerationwaste) and lower sodium leakage.Initial capital costs can be higher fora counter-current operation andmore care has to be taken in thedesign of a unit as it has to be ableto give the highest quality of treatedwater. Also, demineralized ordecationized water must be usedfor diluting the regeneration chemi-cals and for the displacement rinse.The design must ensure that thechemicals contact the resin at thecorrect concentration by avoidingany excessive dilution. In conven-tional counter-current regeneration,a presentation rate of 2 gramregenerant per minute and per literresin has shown the best results foroptimum regeneration efficiency.This results in a regenerant flowrate 3 m3/h per m 3 (0.4 gpm/ft3) ofresin when a 4% regenerant con-centration is used.

Data on typical operationalcapacities for DOWEX HCR-S resinusing HCl or H2SO4 are given inFigures 12 and 13. Levels of averagesodium leakage can be calculatedfrom data presented in Figures 10and 11. The desired leakage level isdivided by the alkalinity correctionfactor, which takes into account thealkalinity percentage of the influent.This corrected leakage valuetogether with the percentage Na inthe influent is now used to establishthe required regeneration level.

Conversely, the sodium leakagefor a given regeneration level canbe established by reading off avalue taking into account again thepercentage Na in the influent, andby multiplying this value with thealkalinity correction factor.

Figure 10. Average Na leakage for DOWEX HCR-S resin incounter-current operation and H2SO4 as regenerant(step-wise concentrations)

Figure 11. Average Na leakage for DOWEX HCR-S resin incounter-current operation and HCl as regenerant

Figu

re 1

2. C

ount

er-c

urre

nt o

pera

tiona

l cap

acity

dat

a

Coun

ter-c

urre

nt o

pera

tiona

lca

paci

ty d

ata

(H2S

O 4 re

gene

ratio

n)In

stru

ctio

ns:

1.Lo

cate

a p

oint

on

the

ordi

nate

of

grap

h A

from

per

cent

sod

ium

and

perc

ent a

lkalin

ity.

2.Tr

ansf

er th

e or

dina

te p

oint

from

grap

h A

horiz

onta

lly to

gra

ph B

and

follo

w th

e gu

idelin

e to

the

chos

enre

gene

ratio

n lev

el th

us e

stabli

shing

a ne

w o

rdin

ate.

3.Re

ad o

ff op

erat

iona

l cap

acity

on

the

right

han

d sid

e of

the

diagr

amco

rres

pond

ing

to th

is ne

w or

dinat

e.

Impo

rtant

See

corre

ctio

n gr

aph

for r

esin

bed

dep

th o

f les

sth

an 2

met

ers.

Stan

dard

con

ditio

ns:

BV/H

x Sa

linity

(meq

/l) = 2

00 T

emp.

15

C

100

9080

7060

5040

kg

H 2SO

4/m3

resin

6.25

5.6

54.

43.

753.

12.

5lb

s H 2

SO4/f

t3 re

sinRe

gene

ratio

n Le

vel

Influ

ent W

ater

Com

posi

tion

Figu

re 1

3. C

ount

er-c

urre

nt o

pera

tiona

l cap

acity

dat

a

Coun

ter-c

urre

nt o

pera

tiona

lca

paci

ty d

ata

(HCI

rege

nerat

ion)

Inst

ruct

ions

:1.

Loca

te a

poi

nt o

n th

e or

dina

te o

fgr

aph

A fro

m p

erce

nt s

odiu

m a

ndpe

rcen

t alka

linity

.

2.Tr

ansf

er th

e or

dina

te p

oint

from

grap

h A

horiz

onta

lly to

gra

ph B

and

follo

w th

e gu

idelin

e to

the

chos

enre

gene

ratio

n lev

el th

us e

stabli

shing

a ne

w o

rdin

ate.

3.Re

ad o

ff op

erat

iona

l cap

acity

on

the

right

han

d sid

e of

the

diagr

amco

rres

pond

ing

to th

is ne

w or

dinat

e.

8070

6050

4030

kg H

Cl/m

3 re

sin

54.

43.

753.

12.

51.

9lb

s HC

l/ft3

resin

Rege

nera

tion

Leve

l

The Bed Depth EffectThe geometry of an ion exchangeplant affects the capacity and thequality of the produced water. A beddepth of about 1 m (3.3 ft) is ideal forco-current operation but little differ-ence exists going from 0.75 m to 2 mbed depth (30 to 6.5 ft). A flow velo-city of 20-30 m/h (8-12 gpm/ft2) maygive slightly better performancethan operating at 50-60 m/h (20-24gpm/ft2).

On the other hand, there is greatadvantage to gain from using a deepbed in counter-current operationwith sulfuric acid as regenerant.

The effect of bed depth is shownin Figure 14.

Warning: Oxidizing agents such as nitric acid attack organic ion exchange resins under certain conditions. This could lead toanything from slight resin degradation to a violent exothermic reaction (explosion). Before using strong oxidizing agents, consultsources knowledgeable in handling such materials.

Notice: No freedom from any patent owned by Seller or others is to be inferred. Because use conditions and applicable lawsmay differ from one location to another and may change with time, Customer is responsible for determining whether productsand the information in this document are appropriate for Customers use and for ensuring that Customers workplace anddisposal practices are in compliance with applicable laws and other governmental enactments. Seller assumes no obligation orliability for the information in this document. NO WARRANTIES ARE GIVEN; ALL IMPLIED WARRANTIES OFMERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED.

Figu

re 1

4. E

ffect

of b

ed d

epth

34

67

5(ft)

Effe

ct o

f bed

dep

th o

nco

un

ter-

curr

ent c

apac

ityIn

stru

ctio

ns:

1.Lo

cate

a p

oint

on

the

ordi

nate

of

grap

h A

from

am

ount

of E

MA

and

chos

en re

gene

ratio

n lev

el.

2.Tr

ansf

er th

e or

dina

te p

oint

from

grap

h A

horiz

onta

lly to

gra

ph B

and

follo

w th

e gu

idelin

e to

loca

te a

new

poin

t acc

ordi

ng to

the

perc

ent

sodi

um o

f EM

A.

3.Tr

ansf

er th

e or

dina

te p

oint

from

grap

h B

horiz

onta

lly to

gra

ph C

and

repe

at th

e pr

oced

ure

unde

r poi

nt 2

acco

rdin

g to

the

desir

ed b

ed d

epth

and

read

off

the

redu

ctio

n in

cap

acity

.

g H 2

SO4/l

iter

% Capacity

EMA

% S

odiu

m o

f EM

A