Simulation of Deposition the Corrosion Waste in a Water Distribution System

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/ C Owned by he au ho s, published by EDP Sciences, 2013 , epjcon 201/ 01133 (2013) 45 34501133 This is an Open Access a icle dis ibu ed unde he e ms o he C ea i e Commons A ibu ion License 2 0 , which .pe mi s un es ic ed use, dis ibu i and ep oduc ion in any medium, p o ided he o iginal wo k is p ope ly ci ed. on, A icle a ailable a h p://www.epj-con e ences.o g o h p://dx.doi.o g/10.1051/epjcon /20134501133 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-- - 01133-p.2 EFM 2012 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 01133-p.3 EPJ Web o Con e ences 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) 01133-p.4 EFM 2012 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) 01133-p.5 EPJ Web o Con e ences 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 ) 01133-p.6 EFM 2012 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 01133-p.7 EPJ Web o Con e ences 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. 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[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 pi nú odu nú i budo . Časť 2: Na ho anie 01133-p.8