Chlorine Dioxide as a Successful Antifoulant Treatment in a Large ...

CHLORINE DIOXIDE CHARACTERISTICSCHARACTERISTICSSUITABLE FOR:b io cid a l a ct iv ity %10090807060504030201 0045678p Hchlorinedioxide9chlorine1011The biocidal activityis constant over thepH 6 - 9u sea water once-throughcooling system (pH 8.5)u recirculating coolingwater system (pH > 8)HHNHHONo reaction withammonia and ureau fertiliser & ammonia plantcooling systemu waste waterOClOrganicONo reaction withorganic matterand oilu refinery and petrochemicalcooling systemu seawater desalination plantOCl

CHLORINE DIOXIDE CHARACTERISTICSCHARACTERISTICSSUITABLE FOR:OTTHMspecursorsClONo formation ofhalogenatedcompounds(TTHMs-dangerousfor human health)u potable waterworksu food and beverage industryu waste water treat. plantssulfatereducingbacteriaOClOStrong biocidalactivity againstanaerobic bacteriau minimize corrosionOClOFeSOxidation ofsulfide to sulfate(sulfide scavenger)u minimize corrosionu minimize bad smell

CHLORINE DIOXIDEClO 2+ e - ---> ClO 2-(E o= 0,95 V)ClO 2+ 4 H + + 5 e - ---> Cl - + 2 H 2O (E o= 1,51 V)Chlorine Dioxide is very active against:- bacteria- viruses- algae- fungi-macroorganism

CHLORINE SPECIES FORMATION IN WATERACCORDING TO pH10090chlorine species in solution %80706050403020Cl2HOClOCl -1000 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5 5,5 6 6,5 7 7,5 8 8,5 9 9,5 10pH

Bacteria wallBacteria colonyx- -- --Cl -STILL ALIVENEWGROWINGSTILL ALIVESTILL ALIVE-----ClO 2-ClO 2-ClO 2-NOgrowing

CHEMICAL FEATURES OF CHLORINEDIOXIDE (ClO 2 )u it is a gas and must be generated on siteu it is soluble in wateru it does not undergo hydrolysis at pH ofcooling wateru it is a strong oxidising agent

MICROFOULINGThe Biofouling problem• Bacteria, Algae, Fungi,• Microbial corrosion• Loss of the heat exchange (loss inthe efficiency of the thermal cycle)MACROFOULING• Mussels, Barnacles, Serpulidworms, Hidroys• Encrusting, loss of water flow, tubesplugging corrosion under deposit.

Chlorine dioxide and chlorine comparisonagainst bacteria100ClO2 and Cl2 effectiveness in seawater at pH 8,2- Cl2 demand = 1,7 mg/l- ClO2 demand = 0,9 mg/l9080Cl2 1,0 mg/lOrganism survival %70605040Cl2 3,0 mg/l3020ClO2 0,3 mg/l100ClO2 1 mg/l0 30 60 90 120 150 180 210 240 270 300Contact time second

CHLORINE DIOXIDE AND CHLORINECOMPARISON ON MACROFOULING GROWTHKg/m2*y807060504030ClO2Cl2blank20Dosage mg/l100Summer- Cl2 2.0- ClO2 0.4apr-99 mag-99giu-99lug-99 ago-99set-99ott-99nov-99dic-99gen-00feb-00mar-00Winter- Cl2 1.3- ClO2 0.2

CHLORINE DIOXIDE AND CHLORINE COMPARISONON THM FORMATION IN SEAWATER HAVINGA TOC OF 5 MG/L800total THM ppbCHLORINE35°C25°C15°CCHLORINEDIOXIDE35°C25°C15°C7006005004003002001000contact time 60 minutecontact time 20 minutedosage rate mg/l20 contact time 10 minute2 1 0,5From “ environmental impact of biocidal antifouling alternative treatments of seawater once through cooling systems ”R. Ambrogi ENEL

CHLORINE DIOXIDE ADVANTAGESu very performant in short time contact systemu reduced corrosion (compared with chlorine)u very performant at high pH (sea water, all organic andZn/phosphonate treat.)u very performant in ammonia contaminated system(fertilizer and ammonia plant)u It can be applied by a simply chlorine plant modification orpossibility no chlorine treatmentu environment friendly disinfection treatment

CHLORINE DIOXIDE GENERATIONClO 2 can be generated on site by using water solutions of:Sodium Chlorite,Hypochlorite and acidaccording to the following reaction:Or by usingSodium Chlorite and Chlorine2NaClO2 + NaClO + 2HCl 2ClO2 + 3NaCl + H2Oaccording to the following reaction:Or by usingSodium Chlorite and Hydrochloric Acidaccording to the following reaction:2 NaClO 2+ Cl 2--> 2 ClO 2+ 2 NaCl5 NaClO 2+ 4 HCl --> 4 ClO 2+ 5 NaCl + 2 H 2O

pHChlorine dioxideto dosage pointpHNaClO fromelectrochlorinatorHCl 33%Sodium chlorite

Chlorine dioxideto dosage pointChlorinated waterSodium chlorite

ClO2 “hypochlorite” generating systemConversion of hypochlorite from electrochlorinator into Chlorine Dioxide

ClO2 “under water” generating systemReaction chamber located into the dilution water lineWater to bedisinfectedWater to bedisinfectedNaClO 2H 2OHClH 2OClO 2DilutionH 2OClO2Water solution

ClO 2ISIA SISTEMI

Chlorine dioxide reagents storage tanks

Chlorine dioxide reagents pumpingstation and control monitoring system

Chlorine dioxide “underwater reactionchambers”

water basin after 18 month operation.Reaction chamberslocated inside theracket pipe

Description of the Facility and Cooling Water(PLANT 1)PLANT:FEEDING:SYSTEM:FLOWRATE:LARGE PETROCHEMICALSEAWATER FROM THE INTAKEBASIN, SCREEN FILTERS, PUMPING STATION BASINS,COOLING TOWERS BASIN,HEAT EXCHANGERS, RETURN TO THE TOWERS,BLOW DOWN TO THE SEA.RR. 175,000 m3/h (full capacity)CHLORINE DIOXIDE DOSAGE:from March to October 2 shot/day at 0.5 ppm as long as 1.5 hour eachshot (TOTAL 3 H/DAY).Winter 2 shot/day at 0.5 ppm as long as 1 hour each shot(TOTAL 2 H/DAY).DOSAGE START UP: February 2009.

Description of the Facility and Cooling Water(PLANT 2)PLANT:FEEDING:LARGE PETROCHEMICALSEAWATER FROM THE INTAKESYSTEM: SCREEN FILTERS, PUMPING STATION, PUMPING STATION,HEAT EXCHANGERS, RETURN TO THE TO THE SEA.FLOWRATE:32,000 m3/h (full capacity)CHLORINE DIOXIDE DOSAGE:2 shot/day at 0.3 ppm as long as 1 hour each shot (TOTAL 2 H/DAY).DOSAGE START UP: February 2009.

Why chlorine dioxide?Chlorine dioxide was selected, to treat the 2 plantsinstead of chlorination for safety, environmental andperformance reasons.In fact, chlorine and sodium hypochlorite areresponsible of bromate and bromoform formation inseawater which are considered very toxic for aquaticlife of the Arabian Gulf.Chlorine dioxide demonstrated to be very efficient atvery low dosage rate, minimizing its residual and theformation of brominated compounds at the dischargepoint.

EasyaReadox SYSTEMelectrochemical biofilm sensor.

As chlorine dioxide shots increase, the baseline come backto its original value showing no biofilm activity

Constant baseline value indicates that no biofilm activitytakes place and the whole system is clean.

ConclusionsWe underline the following advantages:•Chlorine dioxide has allowed to minimize the growing ofboth micro and macro-fouling inside cooling systems ofpetrochemical plants at very low dosage rate,•Monitoring system has demonstrated to be the “Brain” ofthe treatment programme. It has permitted to injectchlorine dioxide in a proper quantity and in the rightmoment, saving material and protecting the environment.

أشكركم على حسن ضیافتكم واھتمامكمThank you very much for your hospitality and yourkind attentionOOClFor further information:ISIA INTERNATIONAL FZCODubai Airport Free Zone AuthorityOffice 238- 6WBP.O.Box 293896-DUBAI-UAETel. +971.(0)47017959Fax. +971(0)47017962e.mail: gpetrucci@isiainternational.com