incrustaciones y depositos

8/13/2019 Incrustaciones y Depositos

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SCAILING AND DEPOSIT IN

MINING PROCESS

Ing. Hyder Mamani

Jefe de Metalurgia


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AQA QUIMICA S.A. ES UNA EMPRESA CON CAPITAL100% NACIONAL DEDICADA DESDE HACE 15 AOS A LASSOLUCIONES INTEGRALES EN TRATAMIENTO DE AGUAS ,CUENTA CON RESPALDO INTERNACIONAL ATRAVEZ DE SUS

REPRESENTADAS, CON 151 CLIENTES EN TODO ELTERRITORIO NACIONAL Y OFICINAS EN NORTE (PIURA) YSUR (AREQUIPA).

TIENE COMO VISION COVERTIRSE EN LIDER EN SU RUBROBASADO EN LA CALIDAD DE SUS PRODUCTOS Y LA

EXCELECIA EN SUS SERVICIOS SOPORTADAS EN SUSISTEMA DE GESTIO DE CALIDAD ISO 9001:2008

Quienes somos?


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INVESTIGACIN Y DESARROLLO SERVICIO TCNICO Y LIMPIEZAS

DEPARTAMENTO DE INGENIERIAASESORIA TCNICA

Nuestros Servic ios


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SCAILING AND DEPOSITS


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Scaling and Deposits

Deposits: Corrosion by-products Fe2O3

Most deposits heterogeneous Contain Ca, P, Fe, Si, Al, Mg, and MnScaling : Calcium Carbonate

Magnesium Hydroxide Calcium sulfate, barium sulfate, -others


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How Scale Forms ?

Concentration (by evaporation)

Supersaturation

Nucleation

Crystal Formation


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Concentration by

evaporation and

supersaturationNucleation

Crystal GrowthScale

How Scale Forms ?


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Influencing Factors

Concentration

Competing ion pairs (i.e. sulfates)

Temperature (Most HVAC condensers are NOThot enough to promote spontaneous nucleation)

pH

Velocity

Surface characteristics


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How deposits form?

Biofilm can accumulate calcium and provide nucleation sitesCorrosion sites may provide nucleation site.

Nucleation and growth at surface irregularity, existing deposit,

or high heat flux surface.

Ca++

Ca++

Ca++

Ca++Ca++

Ca++Ca++

CO3--

CO3--

NaCO3-

CO3--

HEAT

NaCO3-

NaCO3-

NaCO3-

SS

SSSS

SS

SS

SS

SS


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How Scaling is the Water?

Water treaters use solubility indices todetermine scaling potential.

Other software such asAdvisor 2,Watercyclecan be used to determinesolubility of salts.


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Controlling Scale

Control pH

Soften the water

Remove the alkalinity Increase blowdown

Add chemical inhibitors(blend of polymers)


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Scaling and Deposit Inhibitors

Main mechanisms: Threshold inhibition

Crystal modification

Dispersion Dispersion of suspended solids

Dispersion of biofilm


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Threshold Inhibition

Keeping a large amount of scale formingspecies in solution by adding selectchemicals at very low dose.

Dose is usually < 5 ppm.

Certain chemicals interact with formingcrystal nuclei preventing their developmentkeeping them in solution.


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Concentration by

evaporation and

supersaturation

Nucleation

Crystal GrowthScale


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Crystal Modification

Crystal modification is the process by which agentsadsorb onto forming crystals past the nucleationstage and modify them in such a way to limitdirectional development .

C O

O-


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Concentration by

evaporation andsupersaturation

Nucleation

Crystal Growth

Scale


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Calcium carbonate crystals


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Modified calcium carbonate crystals


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Dispersion

A process by which charged particles areprevented from agglomerating.

Most cooling water particulates have a netnegative charge. Addition of dispersantincreases the charge inhibitingagglomeration.

Essentially the opposite of coagulation.


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Dispersion


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Commonly Used Crystal Modifiers andThreshold Inhibitors

Phosphonates

HEDP PBTC Others

Polymers AA AA/AMPS MA PCA

Polymers and phosphonates


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Phosphonates

Organic molecules with phosphonic acidgroups attached

Very strong threshold inhibitors and crystalmodifiers

Performance characteristics vary

Typically maintained at 3-7 ppm active insystem

HEDP and PBTC most commonly used.


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HEDP

Good performance

Provides good chlorine stability

Less stable in bromine

Overfeed can precipitate Ca complexes Fair corrosion inhibitor

Typically maintained at 3-7 ppm active in system


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HEDP

MW = 206 %PO4= 92.2


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PBTC

Good performance especially under high

stress conditions Excellent chlorine and bromine stability

Typically maintained at 3-7ppm active in

system Higher cost


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PBTC

MW = 270

%PO4 = 35%


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Dispersants/Stabilizers

Polymers based on acrylic acid disperse suspendedcolloidal solids.

Acrylate (AA) polymers are also threshold inhibitors. Polymaleates very good crystal modifiers but do not

always prevent precipitation. Certain sulfonated (i.e. AA/AMPS) polymers stabilize

precipitants such as Ca3(PO4)2, Fe, and Zn salts. Typically maintained at 5-10 ppm active in system


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Dispersants/Stabilizers

Polyacrylates

AMPS/Acrylate

AMPS/Acrylate terpolymers Sulfonated styrene

Maleic Acid Homopolymer

Maleic acid co and terpolymers Phosphinocarboxylates


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ANCOTREAT 5690I

Phosphonate (Cristal Modifiers)

AA/AMPS/Terpolymer (Metals

stabilization and threshold efect) Polymers based on acrylic acid disperse

suspended colloidal solids.(Dispersants)

Acrylate (AA) polymers (thresholdinhibitors)


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Scale Control Hints

Uses the correct blend polymer/phosphonate. Test total phosphate in make up water. Check equipment skin temperatures. Running Ca vs cycles indicates gross

precipitation only! Do not overfeed inhibitors. Maintain feed and control equipment. Always check recirculation quality water

Side stream filtration. Others?

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