Wwt Cooling Water

8/12/2019 Wwt Cooling Water

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Cooling Water

Watertreatment and

chemical conditioning ofopen and closed

cooling systems

Dr. K. Nachstedt, Weidner Wassertechnik, Herten


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Recirculation of process water

volume of utilization is increasing

volume of delivery is nearly constant


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Rate of cooling water at direct

wastewater disposal


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Cooling Systems

!low"through system

must #e close to waters

no recirculation of water

$ery large $olume of water consumption

marginal e%penses for water treatment

ecological pro#lem& temperature rise of waters

rare used at the present state of technology


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Cooling Systems '

closed(semi"closed circulation system

typical useage& hydraulics, engine, in)ection moulds

neglecti#al loss of water

$ery strong corrosion inhi#ition possi#le

connected to heat e%changers of secondary coolingsystems *refrigerating machine ( cooling tower


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Cooling Systems +

pen e$aporating cooling systems

mainly used system& cooling tower

target& high rate of recirculation *cycles of conc.-

consumption of water& e$aporaton #lowdown

watertreatment is always necessary


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Cooling Systems /

Cooling towers

more than 012 of cooling capacity& e$aporation

$ery high cooling capacity& use of latent heat of

e$aporation

consumption of water depends directly on water

treatment


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3ro#lems to sol$e

Closed circuitshigh temperatures may cause scaling and corrosion

large copper surfaces in heat e%changers

differences in electrical potentials *e.g. target cooling-

pen circuits *cooling towers-

high concentration of minerals in circulation water

deposits of calcium car#onate *scale formation-

#iological growth *organic contamination, fa$ora#le

en$iroment for microorganism-


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3riority tasks in cooling water treatment

a$oidance of inorganic deposits *scale inhi#ition-

pre$ention ( inhi#ition of corrosion

control of #iological growth *fouling control-


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Steps to take

Cooling e4uipment&

Careful selection of materials and "com#inations

!low $elocity within the range ,5 6 ' m(s

low temperature of water and materials 7 /5 8C *large

surfaces of heat e%changers-

Water&

uter water treatment *9nits and e4uipment-

filtration, softening, desalination

:nternal water treatment *chemical products-

:nhi#itors for corrosion and scaling, antimicro#ials


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Closed ( semi"closed systems *-

9sually easy to treat&

small system$olume& typically 7 '11 m;

no sunlight& suppression of #iol. growth

only small entry of pollution

need only small amounts of makeup water*small costs of treatment products-

/5 8C


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Closed ( semi"closed systems *'-

Chemical treatment

in the past& chromates, nitrites, ?inc, polyphosphate

today& com#inationproducts

dispergators *polycar#onic acids-

corrosion inhi#itors *moly#dates, phosphonates, organic N"heterocyclic compounds-

scaling inhi#itors *phosphonates, polycar#onic acids-

=ypical products @ e4uipment necessary&

dosing system& metering pump water meter with impulse output

treatment product& ca. +"/ kg(m; water

controling& testkits ( online"analysis ( corrosion tests

#iological contamination *well"water- & Aiocides( 9B"#urner


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Closed ( semi"closed systems *+-


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Closed ( semi"closed systems */-

Destructed surface of cast iron&

+ weeks after setting in operation with dangerous inhi#itorconcentration


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pen e$aporation cooling systems *-

Water treatment can #e $ery complicated

System$olume range 511 6 '111 m;


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pen e$aporation cooling systems *'-

!irst priority& 3re$ention of deposits

Fconomical target& ma%imum of concentration cycles as

possi#le G *sa$ing of makeup water-&

F%ceeding the limit of solu#ility of inorganic compounds&

calciumcar#onate deposits *lime scale-

concentration of chloride content in the circulation water&promoting of corrosion *pitting at passi$e metals-

concentration of dirt in the circulation water&

sludge"deposits can cause #iological pro#lems


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pen e$aporation cooling systems *+-

=arget& cycle no. CN > ',5

Bolume makeup *B


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pen e$aporation cooling systems */-

3ractical imits of concentration cycels&

car#onate"hardnessE 7 '18 dH *tot. alkal. 7 I mmol(l-

*#etter, if a$aila#le& S: 7 ',0-

Chlorid concentration 7 '11 mg(l *danger of pitting-

:s it possi#le to operate an open cooling system withouthardness"sta#ili?erJ

15 mg(l = ca)0*7 +d,


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Deposits *-

Fffects of deposits

Corrosion and micro#iol. growth at and #elow deposits

oss of energy *flow resistance in pipes-

!aulty flow *ca$itation, erosion, promotion of corrosion-

3oor heat transfer in heat e%changers *increas. tranf. coeff.-


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#lagerungen *'-

3late of heat e%changer 3ipe of cooling

system


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3roducts and methods of treatment *-

Aasics of treatment products *state of the art-

phosphonic acids and phosphonates

scale inhi#ition

corrosion protection

3olycar#onic acids ( polycar#onatesdispersing agent ( mo#ilisation of sludge

scale inhi#ition

organic N"heterocyclic compounds *=ria?oles-

corrosion inhi#ition of yellow metals

additi$es for sta#ilisation of the formulation


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3roducts and methods of treatment *'-

3hosphonic acids& most effekti$e scale inhi#itors

=hreshold"in#itors *nonstoichiometric application-

F%ample& stoichiometric usage of known chelates


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3roducts and methods of treatment *+-

3hosphonic acids ( 3hosphonates

=hreshold"inhi#ition *far #elow stoichiometric ratios-

principle of operation& #locking of crystal growth

under"stoichoimetric ratio &7111

underdosing& no hard deposits *easy to purge away-

synergistic effect in com#ination with polycar#onic

acids

usual concentration 5 " 1 g(m; makeup water

:nhi#ition ( pre$ention of corrosion

amplification effect for other inhi#itorsforming of protecti$e mem#ranes& anodic and cathodic

corrosion inhi#ition


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3roducts and methods of treatment */-

3hosphonic acids ( phosphonates

:mportant difference& no polyphosphates G *!rom the pastG-

#asy -ydrolysis '.egradation to ort-o&-os&-ate '

/-os&-onic acid are stale to -ydrolysis in cooling $ater


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3roducts and methods of treatment *5-


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3roducts and methods of treatment *L-

Dipersing of sludges& anionic polymeres

geringe


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R @ D of formulations

=u#e"Alocking"=est ( Scale inhi#ition test *NCF-


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3ractical application

Scale inhi#itors ( corrosion inhi#itors

Dosing proportional to addition of makeup water

typical dosing& L"'1 g(m; makeup water

control of product concentration& total phosphate or

special polymertest *if polymers are detecta#le-

limit of scale sta#ilisation& '1 8dKH ( Immol(l =

a#o$e limit of sta#ilisation&

dosing of mineral"acid *internal decar#onisation-

:on"e%change ( re$erse osmosis&

decar#onisation ( softening ( desalination


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Aiological Control

ntimicro#ials ( #iocides

Not o%idi?ing #iocides

:sothia?olinones *C:=(


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pplikation of antimicro#ials

Nono%idi?ing antimicro#ials

always shockdosing *a$oiding of resistenceG-

inter$al time after dosing& I " / days

necessary concentration 1, kg ( m; circuit $olume

use with surfactant to com#at #iofilms

e%pensi$e for large circuit $olumes

%idi?ing antimico#ials

continuous dosing possi#le

may promote corrosionchlordio%ide e%cellent for #iofilms

Control of treatment success&

micro#iological e%amination in regular inter$als


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=reatment of open circuits


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utomatic system for open

cooling circuits

.osing of scale in-iitors

Control of concentration cycles via conductivity

/,Control and &,regulation

reatment $it- microialsnonoidizing dosing at selectale times

oidizing dosing de&ends on continuously

measurement sensor* online analysis4

Meeting ,6 n-ang 31 luminicence test4

8loc9ing of lo$ do$n ( &relo$do$n


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utomatic management system for

cooling water

sensor for halogen

T

fluorescence

carboxylate

ortho - PO4

total- PO4

pH

total alkalinity

conductivity

Cooling tower

water circuit

Analytical Parameter Information

concentration cycles

concentration cycles

acid dosing / decarb.

Oxid. bioide content

cooling capicity

conc. treat!ent prod.

phosphonate x " #

conc. treat!ent prod.


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KW


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KW


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Keywords& F%ternal Water =reatment

:f no economical internal treatment is possi#le&

Softening of waterworks continuously

large consumption of regeneration salt

*often more than 51.111 Kg(year in medium circuits-

Decar#onisation *partial desalination-internal decar#onisation *decreasing pH, acid dosing-

e%ternal decar#onisation *weak acid ion e%changer-

Desalination

!ull desalination *:on"e%changer, anionic cathionic-

Re$erse smosis *Costs of energyG I52 yield -


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Summary

Aasic schematics of open and closed circuits ha$e #een

introduced.

=argets of cooling water treatment in open and closedcircuits were pointed out.

:nternal *chemical- and e%ternal *e4uipment #ased-

treatment possi#ilities and limitations ha$e #eendiscussed.

3ro#lems of cooling systems and possi#le solutions ofsuita#le water treatment ha$e #een shown.


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!urther 4uestions informations

.r) :) Nac-stedtel) 017;("0110"29)nac-stedt

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Wwt Cooling Water