SIMULATION OF DEPOSITION THE CORROSION WASTE
IN A WATER DISTRIBUTION SYSTEM
I ana JELENÍKOVÁ•, Ondřej ŠIKULA, Jana PERÁČKOVÁ
Abs ac : In wa e dis ibu ion sys ems can be ound pa icles o us and o he
mechanical con aminan s. The pa icles a e deposi ed in loca ions whe e he low
eloci y o wa e low. Whe e a can cause he pi ing co osion. Is a conce n in he
sys ems made o gal anized s eel pipes. The con ibu ion deals wi h CFD
(Compu a ional Fluid Dynamics) simula ions o wa e low and pa icles deposi ion
in wa e dis ibu ion sys em. CFD Simula ions we e compa ed wi h he
co osi e deposi s in eal pipeline. Co osion is a spon aneous p ocess o
des uc ion o me al ma e ial due o elec ochemical eac ions o me al wi h he
agg essi e su ounding. Elec ochemical co osion is caused by he
he modynamic ins abili y o me al and he e o e can no be comple ely supp ess, i
can only in luence he speed o co osion. The equi emen is o keep me al
p ope ies du ing he whole i s li e ime. Reques ed se ice li e ime he wa e pipe
acco ding o EN 806-2 is 50 yea s.
1. INTRODUCTION
Pa icles o us and o he mechanical con aminan s can be ound in wa e dis ibu ion
sys ems. The pa icles a e deposi ed in segmen s wi h low eloci y o he wa e low and
can cause a pi ing co osion. Mainly sys ems made o gal anized s eel pipes a e
conce ned. The con ibu ion deals wi h Compu a ional Fluid Dynamics (CFD) simula ions
o wa e low and pa icles deposi ion in a wa e dis ibu ion sys em.
Elec ochemical eac ions occu a phase in e ace elec ode - elec oly e. Two elec odes
a e equi ed o he elec ic cu en o pass be ween he elec oly e and he elec ode,
o ming an elec ochemical cell. The elec ode can be any solid o liquid phase, which is
elec on o ion conduc i e. Me als wi h di e en elec ic po en ials o m he
elec ochemical cell, which is a p e equisi e o he elec ochemical co osion. Me als wi h
di e en elec ochemical po en ials a e o en connec ed in he piping, which leads o
co osion o he me al wi h nega i e elec ical po en ial, o example connec ion o piping
made o gal anized s eel a e componen s con aining coppe esul s in co osion on he
gal anized piping. Elec ical po en ial di e ence in wa e piping sys em can also esul
om sedimen a ion o a ious co osion pa icles o o he pollu ing pa icles in he
piping, which can ac as elec ode, o ming an elec ochemical cell wi h he me al
su ace.
• I ana Jeleníko á, Jana Pe áčko á, Slo ak Uni e si y o Technology, Radlinského 11, 81368
B a isla a, Slo akia, [email p o ec ed], [email p o ec ed]
Ondřej Šikula, B no Uni e si y o Technology, Ve eří 331/95, Czech Republic, [email p o ec ed]
EPJ Web o Con e ences
DOI: 10.1051/
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epjcon 201/
01133 (2013)
45
34501133
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EPJ Web o Con e ences
The anspo o ions in he elec oly e is caused by:
1 - di usion (mo emen caused by concen a ion g adien o pa icula ion)
2 - mig a ion (mo emen caused by elec ical po en ial g adien in he elec oly e)
3 - con ec ion (mo emen caused by elec oly e low)
Figu e 1: The p inciple o co osion o i on [8].
Fig. 1 illus a es edox eac ion o i on in he elec oly e. The elec ical cha ge is no
equal h oughou he me al su ace, due o manu ac u e de ec s o p esence o
impu i ies. I can he e o e become he ca hode a one poin and he anode a ano he
poin and a low o elec ons can be es ablished be ween hese wo poin s.
Two elec ons (2e-) a e eleased om he i on su ace in an elec oly ic en i onmen .
These elec ons a e hen used by he educ ion o oxygen acco ding o he equa ion:
½ O2 + H2O + 2e- →2 OH- (1)
The esul ing hyd oxide anion eac s wi h he e ous ca ions and e ous hyd oxide is
o med:
2 OH- + Fe2+ → Fe(OH)2 (2)
Fe ous hyd oxide is an uns able whi e c ys alline subs ance, which oxidizes immedia ely:
Fe(OH)2 +O2 → Fe(OH)3 + H2O (3)
Fe ic oxide is he eby c ea ed, being a b own wa e -insoluble subs ance - us [8].
Pi ing co osion occu s in wa e dis ibu ions sys ems unde a deposi ion o wa e calc
and wa e -insoluble subs ances o unde a deposi ion o mic obial o igin, mos ly in he
wa e ci cula ion piping, whe e he wa e eloci y is low.
Causes o pi ing co osion a e:
- o ma ion o deposi ion on me allic ma e ials o o ganic o ino ganic o igin (missing o
aul y wa e ea men )
- inapp op ia e choice o ma e ial
- ailu e o ollow he equi ed echnological pa ame e s o he sys em (low wa e
low a e - deposi s o ma ion)
- a combina ion o hese ac o s and wa e empe a u e (dis ibu ion o domes ic
ho wa e and ci cula ion o domes ic ho wa e ).
A e o ma ion o he deposi s i is di icul o p e en he co osion unde he deposi s,
because i is impossible o apply co osion inhibi o on he me al su ace [4].
Fe(OH)3
WATER+ O2
(ELECROLYT)
ANODE CATHODE
O2
OH-
Fe Fe +2e
Fe2+
2+ 12 O + H O+2e 2OH
2--
-
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2. CFD SIMULATION AND EXPERIMENTS OF DEPOSITION OF THE CORROSION
WASTE
In Ansys Fluen was simula ed wa e low in he dis ibu ion sys em and deposi ion o he
co osion was e. The dis ibu ion sys em was designed so as aking in o accoun
p oblema ic sec ions in he exis ing wa e dis ibu ion sys ems (Fig. 2) Fo a speci ic low
a e 3 l/s, 4 l / s and 5l/s. Simula ing he wa e low eloci y, o chosen low a es, we e
selec ed loca ion wi h he lowes wa e low a e. In hese a eas e e ences pa icles
deposi ion we e simula ed.In wa e dis ibu ion sys em which chemical eac ions occu
co osi e pa icles ha se les and cause u he co osion. Was simula ed wa e low
a e and pa icles deposi ion a e o ma ion he co osion pa icles, and assume o by
he pa icles chemically do no eac .
In nex s ep will simula ion he chemical eac ion in wa e dis ibu ion sys em.
Figu e 2: Scheme o selec ed sec ions o he aqueduc whe e he lowes a e o
wa e low, mos likely o pa icle deposi ion.
The wa e low in he dis ibu ion sys em and deposi ion he co osion pa icles was
simula ed wi h disc e e phase model. T ajec o y o e e ences pa icles and hei
concen a ion in he pipe su ace we e simula ed. The ajec o y o a disc e e phase
pa icle is w i en in a Lag angian e e ence ame. The pa icles mo ion is desc ibed by
equa ions (change o low a e he e e ence pa icles in ime):
( )
( )
p x p
D p x
p
du g
F u u F
d
ρ ρ
ρ
−
= − + +
(4)
whe e Fx an addi ional accele a ion e m
FD (u - up ) he d ag o ce pe uni pa icle mass and
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2
Re
18
24
D
D
p p
C
Fd
µ
ρ
=
(5)
whe e u luid phase eloci y,
up pa icle eloci y
µ hem molecula iscosi y o he luid
ρ luid densi y
d pa icle diame e
Re Reynolds numbe which is de ined as
( )
Re
p p
d u u
ρ
µ
−
=
(6)
The wa e low in he dis ibu ion piping was simula ed o speci ic low a es o 3 l/s,
4 l/s and 5 l/s. The simula ion was done o selec ed segmen s o he dis ibu ion sys em
wi h he lowes wa e low eloci y and hus wi h he highes isk o co osion (Fig.2). In
hese segmen s deposi ion o e e ence pa icles was simula ed, he e e ence pa icles
being sphe es wi h e y small diame e s. The piping was ep esen ed by he su ace o
a geome ic scheme. The oughness o he simula ed piping was ze o. Bac e ial mic o ilm
is c ea ed on he inne su ace o he piping and his mic o ilm is basically non- emo able
[3]. Wi h ega d o his ac , in ini e e e ence pa icle adhesion was assumed in he
simula ion.
Se ing he disc e e phase model
Co osion was es we e de ined by e e ence pa icles. Disc e e phase model o Numbe o
Con inuous Phase I e a ions pe DPM I e a ion was se a 10. Be se phase o i e
disc e e ac ions Injec ions, eleased om he su ace o he wa e inle . Ma e ial
disc e e phase was selec ed om da abase FLUENT, Calcium ca bona e CaCO3, wi h
a densi y and weigh o de aul . Diame e o ac ion a e 1 µm, 5 mic on, 20 mic on, 80
mic on, 100 mic on ineness co esponding wha used il e s. To al low a e he
e e ence pa icle was calcula ed om he s anda d se a maximum amoun o suspended
solids in wa e 15 mg/l. To al low a e he e e ence pa icle was calcula ed om he
s anda d se s amoun o subs ances in wa e 15 mg/l.
In ig. 3 a e simula ion esul s o eloci y o he moni o a eas T- shape and knee in he
axis he pipe.
Figu e 3: The wa e low eloci y (m/s)
a) T-Shape, b) knee.
a)
b)
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In ig. 4 a e simula ion esul s o deposi ion o he e e ence pa icles and a compa ison
wi h eal deposi s in wa e pipes. S eady-s a e pa icle concen a ions on he pipe wall
and in selec ed c i ical segmen s - T-piece - we e simula ed.
Figu e 4: The concen a ion he co osion was e in ou doo su ace o he
pipeline (mg/l)
In igu e 5 is he compa a ion he simula ion and eal co osion in T-shape, in his igu e
we can see he co osion in a ea who simula ion shows he mos concen a ion o
e e ence pa icles.
Figu e 5: The gal anized s eel piping he deposi ion he co osion was e.
a)
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In igu e 6 is esul o simula ion he concen a ion o e e ence pa icles in knee.
a)
Figu e 6: The concen a ion he e e ences pa icles (mg/l)
a) in he indoo su ace he piping, b) in he ou doo su ace.
b
)
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Figu e 7: The gal anized s eel piping he deposi ion he co osion was e.
In igu e 7 is he compa a ion he simula ion and eal co osion in knee, in his igu e we
can see he co osion in a ea who simula ion shows he mos concen a ion o e e ence
pa icles.
3. CONCLUSIONS
The simula ion e i ied he deposi ion o e e ence pa icles in he selec ed segmen s o
he wa e piping. The isk o occu ence o he poin co osion is he g ea e , he g ea e
he concen a ion o he deposi ed subs ances in he piping o ming an elec ochemical
cell wi h he su ace o he piping. The occu ence o poin co osion can be diminished
by p ope selec ion o he piping ma e ial, p ope design o wa e eloci y especially in
he ci cula ion domes ic ho wa e piping, and p ope ealiza ion o he sys em wi h
ins alla ion o a ine pa icle il e . Ins alla ion o he il e is p esc ibed by BS EN 806-2,
o p e en in il a ion o di om public wa e line. In a eas whe e pipeline is bypassing
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o he s uc u es i is necessa y o ins all an ou le al e, which p e en s deposi ion o he
di in he piping.
4. ACKNOWLEDGMENT
This con ibu ion was p epa ed wi hin he p ojec VEGA 1/0511/11. This pape o igina es
also wi h a suppo o he Speci ic esea ch a uni e si ies in he Czech Republic No.
FAST-S-11-1.
5. REFERENCES
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ene ge ike 2006, Košice. 2006. s . 1.
[2] Richa dson, J.R. and Zaki, W. N.: Sedimen a ion and Fluidiza ion, pa 1, Tans.
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[3] Baldyga, J.: Tu bulen mixe mode lwi h applica ion o homogenous
ins an aneous chemical eac ions. Chem.Eng.Sci.,44:11751182,1989. J.
[4] Lukáč, J., Vano čan, J. Madej ,J.: Ko ózia pod nánosmi; Mechanizmy, P íčiny,
P e encia, In: Ko ózia ene ge ike 2008, Košice. 2008. s . 44
[5] Valášek, J.: Zd a o no echnické za iadenia budo . B a isla a: Jaga. 2005
[6] V anayo á, Z.: Ko ózia a ink us ácia oceľo ého po ubia, In: Zbo ník SANHYGA,
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[7] Ila ský, J., Ba loko á, D., Biskupič, F.: Chémia ody a hyd obiológia, STU,
B a isla a, 2008
[8] Kocich, J., Tuleja, S.: Ko ózia a och ana ko o , ALFA, B a isla a, 1988
[9] Košičano á, D.: Och ana po ubí p ed ko óziou a ink us áciou. In: Zbo ník
SANHYGA, Piešťany 1996. s .157.
[10] STN EN 10240 Vnú o né a/alebo onkajšie och anné po laky na oceľo ých
ú ach. Požiada ky na po laky nanášané žia o ým zinko aním pono om
au oma izo aných p e ádzkach.
[11] STN EN 806-2 Technické podmienky na zho o o anie odo odných po ubí na
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