Dow Inc. · NYSE:DOW
Dow — Technical Presentation (August 2015)
40 slides from Dow's technical presentation, August 2015
Slide 1: Controlling Mineral Scaling in Cooling Towers
Controlling Mineral Scaling in Cooling Towers Somil Mehta DOW RESTICTED
Slide 2: Outline
Outline 1. Water Chemistry 2. Scaling 3. Basics of Antiscalants for Water Treatment 4. Industrial Cooling Circuits 5. Key Competitive Technologies 6. Antiscalant tracing 7. Limitations of Antiscalants 8. Trends & Macro Drivers 2
Slide 3: 1. Water Chemistry
1. Water Chemistry • Water conditioning of any industrial equipment involves the knowledge of the composition of the water. Particularly important is to know the following physico- chemical parameters: • Anions concentrations • Cations concentrations • pH • Temperature • Total dissolved solids • The
Slide 4: Water Chemistry – pH Levels
Water Chemistry – pH Levels • If real water pH is : • < pHs, this means that CO2 dissolved in water is > equilibrating CO2, the water is called aggressive. It will tend to dissolve Calcium Carbonate (CaCO3). • > pHs, this means that CO2 dissolved in water is < equilibrium CO2, the water is called sc
Slide 5: Water Chemistry - Salts
Water Chemistry - Salts • CaCO3 is the most common precipitating salt found in water, though there are others. The following salts also have low solubility in water and so can cause precipitation: • Carbonate (Ba, Sr, Fe) • Sulfate (Ca, Ba, Sr) • Phosphate (Ca, Fe) • Silicate (Mg) • Oxide (Fe) • Hyd
Slide 6: Water Chemistry – Parameters to Consider
Water Chemistry – Parameters to Consider The following parameters must be taken into account when evaluating water scaling tendency: 1. Water Hardness • Calcium hardness 3. Strong Acids Salts (SAS) • Magnesium hardness • Chlorides, sulfates, nitrates, fluorides, etc • Total hardness 4. Total Dissolv
Slide 7: 2. Scaling
2. Scaling Scaling is the precipitation of sparingly soluble salts • It can create the following problems in industrial equipment: • Loss of heat transfer coefficient • Pressure loss in circuits • Pump blocking • Tube plugging • Membrane plugging (Reverse Osmosis) • Tube perforating (Boilers) • All
Slide 8: Avoiding Scaling
Avoiding Scaling To avoid scaling: 1) Move Calcocarbonic equilibrium towards hydrogen carbonate solubilization. This can be realized by dropping water pH to be lower than calculated pHs (acid feed). However, this can lead to another problem: Corrosion. 2) Use scale inhibitors: • Sequestering agents
Slide 9: 3. Anti-Scaling Mechanisms
3. Anti-Scaling Mechanisms • There are three modes of antiscaling: • Threshold effect – to retard the growth of seeds • Crystal distortion – to maintain small, non-adhesive crystals • Dispersion – to suspend particles such as iron oxides and clays and to avoid fouling No Additive With Antiscalant 10
Slide 10: Anti-Scaling Mechanisms
Anti-Scaling Mechanisms 1) Threshold effect (Crystal Growth Inhibition) : Salt seed Polymer chain Polymer adsorbed on seed Polymer chain Disintegrated seed
Slide 11: Anti-Scaling Mechanisms
Anti-Scaling Mechanisms 2) Crystal distortion (Steric repulsions) : Crystal Polymer chain Distorted crystal Broken crystals Polymer chain 3) Dispersion (Electrostatic repulsions) : - - - - - - - -
Slide 12: Classes of Polymeric Antiscalants
Classes of Polymeric Antiscalants Homopolymers Terpolymers 1 2 Copolymers 13
Slide 13: Phosphonates
Phosphonates • Organophosphorous compounds • Very good CaCO3 inhibitors • Limitations: • Poor dispersants • Relatively less tolerant to high temperatures 14
Slide 14: Visual Demonstration of Scale Formation
Visual Demonstration of Scale Formation Blank Inhi A Inhi B Inhi C 15
Slide 15: Visual of Dispersion
Visual of Dispersion 1000 ppm Fe2O3 settling test DOW RESTRICTED 1
Slide 16: 4. Industrial Cooling Circuits
4. Industrial Cooling Circuits 17
Slide 17: Water Concentration in Cooling Circuits
Water Concentration in Cooling Circuits Silica, CaCO3 particulate, scaling biofouling hot side cold side Blow down 18 http://www.quora.com/What-is-the-complete-working-system-of-a-cooling-tower
Slide 18: Once-Through Cooling Towers
Once-Through Cooling Towers Cold Fluid Exchanger Hot Fluid Reservoir DOW RESTRICTED
Slide 19: Open Circuit Cooling Towers
Open Circuit Cooling Towers • Characteristics: • Water used only once and directly ejected to the natural environment • No water concentration • Very high amount of water used • No longer allowed in many countries • Problems: • Scaling due to water quality and temperature increase • Corrosion if wat
Slide 20: Closed Circuit Cooling Towers
Closed Circuit Cooling Towers Expansion tank Hot Fluid Hot Water Occasional Addition Air/Water Exchanger Exchanger Cold Water Circulating Cold Fluid Pump DOW RESTRICTED
Slide 21: Closed Circuit Cooling Towers
Closed Circuit Cooling Towers • Characteristics: • Good quality water used (deionized or soft water) • Small amount of water used (only occasional water addition) • Problems: • Corrosion due to oxygen and high temperature • Biofouling • Treatment: • High concentration used since low water consumptio
Slide 22: Open-Recirculating Cooling Towers
Open-Recirculating Cooling Towers Drift & Evaporation Hot Fluid Cooling Make-Up Water Tower Exchanger Cold Fluid Exchanger Blowdown Re-Circulating Pump DOW RESTRICTED
Slide 23: Open-Recirculating Cooling Towers
Open-Recirculating Cooling Towers • Characteristics: • Water cooling is ensured by evaporating a part of it (1-2%) • Water is concentrated due to evaporation • Water consumption is significant (between open circuit and close circuit) • Problems: • Scaling due to water concentration, temperature and
Slide 24: Comparison of All Cooling Towers
Comparison of All Cooling Towers Where are antiscalants used? • Open circuits: • Antiscalant consumption very low » Low concentration treatment » Cooling system less and less used • Close circuits : • Antiscalant consumption not that big: » Good quality water used » Treatment applied in one time (ev
Slide 25: Industrial Cooling Circuits
Industrial Cooling Circuits • Stabilized phosphate treatment • Phosphates are used as corrosion inhibitors • Polymer is used to disperse particles, inhibit CaCO3 and stabilize calcium phosphates • Choice of the polymer is critical to the success of the treatment Parameters to take into account are:
Slide 26: Industrial Cooling Circuits
Industrial Cooling Circuits Stabilized phosphates treatment • Deionized water 40.7 % • Phosphoric acid (75%) 11.0 % • Potassium hydroxide 20.3 % • Potassium pyrophosphate (anh.) 6.5 % • HEDP 4.0 % • Polymer 15.5 % • Tolyltriazole 2.0 % • Dosage : 80-140 ppm in the circuit water 27
Slide 27: Stabilized Phosphate Program
Stabilized Phosphate Program 28
Slide 28: Industrial Cooling Circuits
Industrial Cooling Circuits • Phosphates - Zinc treatment • Phosphates and zinc are used as corrosion inhibitors and form a protective film of iron and calcium phosphate and zinc hydroxide on metal surfaces • Due to very low solubility of these salts, a polymer must be added to control and allow pre
Slide 29: Industrial Cooling Circuits
Industrial Cooling Circuits Phosphate - Zinc treatment • Deionized water 59.9 % • Hydrochloric acid (20 °Be) 10.0 % • Phosphoric acid (75 %) 8.5 % • Zinc chloride (anhydrous) 4.0 % • PBTC 5.0 % • Polymer 11.6 % • Benzotriazole 1.0 % • Dosage : 80-140 ppm in the circuit water 30
Slide 30: Industrial Cooling Circuits
Industrial Cooling Circuits • All organic treatment • Relies on high pH (8-9) and high alkalinity (< 200 ppm) to help passivating metal surfaces • Phosphonate is used to inhibit CaCO3 precipitation and form a corrosion inhibiting film of calcium phosphonate • Polymer is used to disperse particles, i
Slide 31: Industrial Cooling Circuits
Industrial Cooling Circuits • All organic treatment • Deionized water 67.8 % • HEDP 11.2 % • Polymer 16.3 % • Benzotriazole 1.0 % • Sodium hydroxide 1.9 % • Dosage : 80 to 140 ppm in the circuit water 32
Slide 32: Phosphonate Stabilization in an All-Organic Cooling Water Program
Phosphonate Stabilization in an All-Organic Cooling Water Program 33
Slide 33: 5. Current Commercially Available Technologies
5. Current Commercially Available Technologies Acrylic polymers Maleic polymers Phosphonates Attributes Attributes Attributes • Good inhibitor & dispersant • Good inhibitor & dispersant • Excellent CaCO3 inhibitor • Arguably slightly better than • Have slight edge over PAA for • Selected phosphonate
Slide 34: Mechanisms of Action
Mechanisms of Action Polymer – Work by all 3 mechanisms Phosphonates – Only Crystal Growth Inhibition • Not as good CaCO3 inhibitor as phosphonate • Excellent CaCO3 inhibitor • Very good scale inhibitor for CaSO4, silica & • Some expensive phosphonates good for CaSO4, others not very good for silica
Slide 35: 6. Antiscalant Tracing
6. Antiscalant Tracing Commercially available tracing methods • Immunoassay • Titration – Quaternary surfactant • HACH • Elemental analysis – P measurement • Fluorescence • Colorimetric 36
Slide 36: 7. Limitations
7. Limitations • Compatibility • Iron (boilers and cooling tower) • Calcium / hardness and other multivalent ions • Other reagents in a formulation – e.g. corrosion inhibitors • Formulation incompatibility • Temperature stability • Microbial contaminations • Impurities from raw materials • Shelf lif
Slide 37: 8. Trends & Macro Drivers
8. Trends & Macro Drivers • Increased Water Scarcity – Due to Increased population, population shifts to more arid areas, increased industrial process use of water – Which results in – Water re-use, increased cycles of concentration, less discharge, increased use of brackish water & desalination – W
Slide 38: Questions & Discussion
Questions & Discussion DOW RESTICTED
Slide 39: Upcoming Webinar
Upcoming Webinar DOW RESTICTED
Slide 40: Thank You
Thank You NOTICE: Although the information and recommendations in this presentation (hereinafter "Information") is presented in good faith and believed to be correct, Dow makes no representations or warranties as to the completeness or accuracy of Information. Information is supplied upon the condit