Water Treatment in Cooling Systems (1).pdf

Water Treatments in Cooling Systems  Types Of Cooling Systems Contents.. Cooling Towers Definitions & Calculation Treatment principles Corrosion Scaling Bacteriological Fouling  Veolia’s Activ...

Water Treatments in Cooling Systems  Types Of Cooling Systems Contents.. Cooling Towers Definitions & Calculation Treatment principles Corrosion Scaling Bacteriological Fouling  Veolia’s Activities Veolia designs and implement solutions for water, waste and energy management, participating in the sustainable development of cities and industries. Liquid and solid ENERGY non-hazardous and hazardous waste management Our expertise covers the entire waste life cycle from collection WASTE WATER to recycling, leading Energy efficiency, Management of the to the final recovery of efficient global water cycle, waste as materials management from production and or energy. of heating and distribution of cooling networks, drinking water to the green energy collection, treatment production. and recycling of wastewater. 3 Veolia Introduction Hydrex Cooling Systems Training Hydrex Cooling Systems Cooling Towers 5  Cooling Water ▪ Cooling water is used directly or indirectly to cool chemical products, processes, steel products, furnaces, reformers and others. Cooling water systems are classified as below: Non-Oxidizing biocide Open recirculating CW Oxidizing biocide Types of Cooling Water Systems Indirect Cooling Water Closed recirculating CW Biodispersant Corrosion inhibitor Once-through CW Scale inhibitor Open recirculating CW Direct Cooling Water Antifoam Once-through CW Passivator Acid/Alkaline cleaners Cooling Systems Training Which one you have in your plant?  Types of Cooling Systems ▪ Cooling systems are classified based on “Exposure to atmosphere” to: Chilled Water Systems 01 Closed Cooling Systems Process CCW Mould & Jackets Cooling Cooling Towers (BW & SW) 02 Open Cooling Systems Direct Cooling (quenching) Semi-open Cooling Seawater Cooling water (HE) 03 Once-through Cooling Sys MED/MSF Cooling water Which type of cooling systems we have in “Data Centers”? Which type of cooling systems we have in “District Cooling”? Cooling Systems Training Once-Through Seawater Cooling: https://goo.gl/maps/ZCzkSJHnghvv5LCH8 7  Once-Through Cooling Water How to calculate ΔT for each side? What is the difference between ΔT and approach T? Do you know about “Thermal Pollution” of seawater? Cooling Systems Training 8  Closed Cooling Systems ▪ Closed recirculating cooling water is circulating water in a closed cycle and subjected to alternate cooling and heating without air contact. The absorbed heat by water is generally transferred by water-water heat exchangers to an open cooling system and then transferred to atmosphere. Advantages No water loss No salt concentration Little oxygen ingress High makeup quality Low corrosion potential Low scaling potential Which type of closed cooling you have in your plant? Cooling Systems Training 9  Chilled Water System (HVAC) ▪ Chilled Water System : is a system designed to control air conditioning temperature for a big building such as hotel or malls in order to control air temperature separately. ▪ Chilled water system consists of: ○ Condenser ○ Evaporator ○ Compressor ○ Pumps ○ Air handling units (AHUs) ○ Cooling tower (optional) ○ Air cooling ○ Pipings Closed Cooling Water Cooling Systems Training 10  Open Cooling System ▪ Open cooling system is a a system utilizes water in contact with air to cool down a process through heat exchanger and water is circulated within a cooling tower. It consists of: recirculating pump, cooling tower, heat exchanger. Features Evaporation water loss Salts concentration (COC) Oxygen is high High makeup water rate High blowdown rate Scaling & corrosion potential Hig biofouling potential Need a lot of experience: chemical & mechanical Cooling Systems Training 11  Data Center Cooling System ▪ Data center is a building or group of building used to house computer systems and associated components such as telecommunications, storage servers & power control. This generates massive heat which make servers slow down or malfunction. Thus it requires a special efficient water-based cooling system. Cooling Systems Training 12  District Cooling Systems ▪ District Cooling Plant (DCP) means the centralized production and distribution of cooling energy. Chilled water is delivered via an underground insulated pipeline to office, industrial and residential buildings to cool the indoor air of the buildings within a district. DCP is more efficient in thermal energy and OPEX. Cooling Systems Training 13 Open Cooling Systems Cooling Towers 14  What is cooling tower? ▪ Cooling Tower is a heat rejection device that rejects waste heat to the atmosphere through the cooling of a water stream to a lower temperature. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb air temperature or, in the case of closed circuit dry cooling towers, rely solely on air to cool the working fluid to near the dry-bulb air temperature. Cooling Systems Training 15  Cooling Towers Classification ▪ Classification by Use: ○ HVAC Cooling Towers: HVAC cooling tower is used to dispose of "reject" unwanted heat from a chiller. Water-cooled chillers are normally more energy efficient than air-cooled chillers due to heat rejection to tower water at or near wet-bulb temperatures. While, Air-cooled chillers must reject heat at the higher dry-bulb temperature ○ Industrial Cooling Tower: Can be used to remove the heat from various sources such as machinery or heated processes. It is used in power plants, petroleum refineries ,petrochemical plants and etc. What do you think the difference? Cooling Systems Training 16  Cooling Towers Classification ▪ Classification by Heat Transfer Method: ○ Dry Cooling Towers: HVAC operate by heat transfer indirectly between the working fluid and ambient air, such as in heat exchanger, utilizing convective heat transfer. No evaporation. ○ Wet Cooling Tower (open circuit): Can be used to operate on the principle of evaporative cooling. The working fluid and the evaporated fluid (usually water) are the same. ○ Closed Circuit Cooling Tower: pass the working fluid through a tube bundle, where clean water is sprayed and a fan-induced draft applied. The heat transfer performance is close to that of a wet CT. ○ Hybrid Cooling Tower: is closed circuit cooling towers that can switch between wet and dry operation. This helps balance water and energy savings across a variety of weather conditions. Cooling Systems Training 17 Closed Circuit Cooling Tower ▪ Closed Circuit Cooling Tower = Evaporative Condenser Cooling Systems Training What do you think the major problems in Evaporative condensers? 18  Cooling Tower ▪ Classification by Air Flow Generation Method: 1. Natural Draft Cooling Tower: Utilizes buoyancy via a tall chimney. 2. Mechanical Draft Cooling Tower: Uses power-driven fan motors to force or draw air through the tower. 1. Induced Draft: A mechanical draft tower with a fan at the discharge (at the top) pulls air up through the tower. 2. Forced Draft: A mechanical draft tower with a blower type fan at the intake. The fan forces air into the tower, creating high entering and low exiting air velocities. 3. Fan-Assisted Natural Draft Cooling Tower: A hybrid type that appears like a natural draft setup, though airflow is assisted by a fan. Cooling Systems Training 19  Natural Draft Cooling Towers ▪ Natural Draft Cooling Tower ○ It is a concrete based (Hyperboloid) with tall chimney where air flow occurs naturally following “Stack Effect”. ○ Stack Effect: It is the movement of air into and out of buildings, chimneys and flue gas stacks is driven by buoyancy. Buoyancy occurs due to a difference in indoor-to-outdoor air density resulting from temperature and moisture differences. Warm moist air is less dense than drier air at the same pressure. This moist air buoyancy produces an upwards current of air through the tower. Warm moist air naturally rises due to the density differential to the dry, cooler outside air. This produces upward current of air through the tower Cooling Systems Training 20  Natural Draft Cooling Towers ▪ Natural Draft Cooling Tower - Videos ○ Inside the cooling tower: https://www.youtube.com/watch?v=2htplQVEU7g ○ How it works: https://www.youtube.com/watch?v=Gouq8epjX5Y Cooling Systems Training 21  Mechanical Draft Cooling Tower ▪ Mechanical Draft Cooling Tower ○ Uses power-driven fan motors to force or draw air through the tower. ○ Has three types: Forced Draft Induced Draft – Cross Flow Induced Draft – Counter Flow Cooling Systems Training 22  Mechanical Draft - Forced ▪ Mechanical Forced Draft Cooling Tower ○ A mechanical draft tower with a blower type fan at the intake. The fan forces air into the tower, creating high entering air flow. ○ Air blown through tower by centrifugal fan at air inlet. ○ Cooling Systems Training 23  Mechanical Draft - Induced ▪ Mechanical Induced Draft Cooling Tower - Cross Flow ○ It is designed in which the air flow is directed perpendicular to the water flow. ○ Air blown through tower by induction through a fan. Cooling Systems Training 24  Mechanical Draft - Induced ▪ Mechanical Induced Draft Cooling Tower - Counter Flow ○ It is designed in which the air flow is directly opposite to the water flow. ○ Air blown through tower by induction through a fan. Cooling Systems Training 25 Mechanical Draft - Induced Which type you have in your plant? What are the advantages of each type? Cooling Systems Training 26 Heat Exchangers Types ○ A heat exchanger is a system used to transfer heat between two or more fluids. ○ Heat exchangers are used in both cooling and heating processes. ○ There are many types (based on structure): Shell & Tube heat exchangers Plate heat exchangers Cooling Systems Training 27 Thermal Energy Cooling Systems Training 28  British Thermal Units (BTU) ▪ British Thermal Units (BTU) ○ Non SI unit ○ It is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. ○ Used in: Power, Steam Generation, Cooling & heating Industries +1 +1 1 ton of refrigeration (TR) = 12,000 Btu/h (3.52 kW). deg C deg F It is the rate of heat transfer needed to freeze 1 short ton (907 kg) of water into ice in 24 hours. Water Water 1 kg 1 lb 1 Cal 1 BTU Cooling Systems Training 29  Cooling Tower Components ▪ Cooling Tower Components ○ Cold Water Basin ○ Cooling Tower Structure ○ Fills ○ Drift eliminators ○ Cooling Tower Fans ○ Water Distribution Piping’s ○ Fan Deck & Fan cylinder ○ Louvers ○ Gear box ○ Drive shafts & Mechanical Equipment Support ○ Valves ○ Nozzles and Electrical & Instrumentation systems. Cooling Systems Training What is the importance of each component 30 Cooling Tower Components Cooling Systems Training 31  Packing Materials (Fills) ▪ Filling or Packing Materials ○ Are the materials added to increase the contact area & contact time between water and air to provide better heat transfer. Has two types: 1. Splash Type Fills: breaks up falling stream of water and interrupts its vertical progress 2. Film Type Fills: causes water to spread into a thin film Film Type Splash Type Cooling Systems Training 32  Drift Eliminators ▪ Drift Eliminators ○ Are employed to remove the water droplets from the warm exhaust air and conserve water and chemicals for corrosion control and algae control. ○ In this type of eliminators, the two-phase exhaust flow is forced to change direction abruptly. This causes the dense drift droplets to hit the eliminator walls and become trapped inside the cooling tower. Can we utilize evaporation? Cooling Systems Training 33  Spray Nozzles ▪ Spray Nozzles ○ Designed to economically provide desired thermal performance at low spray heights typical to cooling towers. ○ Plastics are widely used for nozzles. Many nozzles are made of PVC, ABS, polypropylene. ○ It increases the water surface and uniform distribution of hot water by forming water droplets instead of water bulk streams. Cooling Systems Training 34  Louvers ▪ Louvers ○ Louvers are made up of asbestos sheets. It serves two purposes. 1. To retain circulating water within the tower 2. To equally distribute the air flow into the fill Cooling Systems Training 35  Definitions & Calculations Cooling Water 36  Mass Balance - Water & Salts Quantitatively, the material balance around a wet, evaporative cooling tower system is governed by the operational variables of make-up flow rate, evaporation and windage losses, draw-off rate, and the concentration cycles. 1. Make-up water (M) 2. Circulation rate (COC) 3. Temperature Differential (ΔT) 4. Evaporation Rate (E) 5. Blow Down Rate (BD) 6. Windage loss Rate (W) 7. Cycle Of Concentration (COC) 8. Cooling tower efficiency What is windage? Cooling Systems Training 37 Mass Balance - Water & Salts Evaporation Process HE Hot water T2 windage Blow down Make-up Cold water T1 Circulation pump Make-up = Evaporation + Blowdown + Windage Cooling Systems Training 38  Circulation Rate (CR) ▪ Circulation Rate (CR) ○ It is the Flow of cooling water being pumped through the entire plant cooling loop. ○ Pumps in series: each pump handles same flow rate, but the total head produced by the combination of pumps will be additive. ○ Pumps in parallel: the flow rates are additive with a common head. Cooling Systems Training Calculator: https://checalc.com/solved/pumpOp.html 39  Evaporation Rate (ER) ▪ Evaporation Rate (ER) ○ It is the amount of water evaporated for cooling purposes. Three factors affecting on the evaporation rate: 1. Surface Area 2. Ambient Temperature 3. Air velocity Rc = circulation rate (m³/h) EC = evaporation constant, 0.85% - 1.0% of Rc for each 10 F (5.6 °C) Cp = specific heat of water = 4.184 kJ/kg.°C Hv = latent heat of vaporization of water = 2260 kJ/kg Cooling Systems Training 40 Evaporation Rate (ER) Does the air temperature play a role in evaporation rate? Or.. Do you think that evaporation rate in winter will be similar to that in Summer? Evaporation rate is affected by air temperature (dry bulb temperature Td) Summer Spring Autumn Winter Actual evaporation rate compared to 90 – 100% 70 – 80% 70 – 80% 50 – 60% calculated rate Cooling Systems Training 41  Windage (W) ▪ Windage or Drift (W) ○ It is the amount of water evaporated for are water droplets that are carried out of the cooling tower with the exhaust air. ○ Drift droplets have the same concentration of impurities as the water entering the tower. ○ It is may be assumed to be: W = 0.3 to 1.0 % of CR for a natural draft cooling tower without drift eliminators W = 0.1 to 0.3 % of CR for an induced draft cooling tower without drift eliminators W = 0.005 % of CR (or less) if the cooling tower has drift eliminators W = 0.0005 % of CR (or less) if the cooling tower has drift eliminators and uses sea water as make-up. Cooling Systems Training 42  Temperatures in Cooling Tower ▪ Types of temperatures in Cooling Tower ○ Four terms are related to Cooling tower temperature: 1. Range (ΔT) 2. Dry-bulb temperature (DBT) 3. Wet-bulb temperature (WBT) 4. Approach temperature ○ Performance Parameters (additional to the above) A. Cooling Efficiency B. Cooling Effectiveness C. Cycle of Concentration (COC) D. Blowdown Loss ΔT ≠ Approach T ≠ DBT ≠ WBT Cooling Systems Training 43  Wet Bulb Temperature (WBT) ▪ Wet Bulb Temperature (WBT) ○ It is the temperature a portion of air would have it if were cooled to saturation (100% relative humidity) by the evaporation of water into it. ○ WBT is the lowest temperature that can be reached under current ambient conditions by the evaporation of water only; it is the temperature felt when the skin is wet and exposed to moving air. ○ WBT is always lower than the DBT but will be identical with 100% relative humidity in air. ○ Performance of cooling tower is dependent on the WBT. Lower wet bulb temperatures means more evaporation. Sling Digital Psychrometer Psychrometer Cooling Systems Training 44 Psychrometric Charts Cooling Systems Training 45 Psychrometric Charts Hydrex Cooling Systems Training 46  Range - Differential Temperature (ΔT) ▪ Range = Differential Temperature Hot Water Temp to CT (in) 45 0C ○ It is the difference between cooling water inlet and outlet temperatures. Range (oC) = Cooling water inlet T - Cooling Water outlet T Range High Range = Good Performance Cold Water Temp From CT (out) 35 0C Approach Wet Bulb Temp (Ambient) 30 0C Cooling Systems Training 47  Blow Down ▪ Blow Down ○ The portion of the concentrated cooling tower water intentionally discharged from the cooling tower to maintain an acceptable water quality in the cooling tower. COC e Che Requ ess irem Wat try Proc mis nt er Blow Down s (S Cos te R/ t Ra m w 3) Flo Cooling Systems Training 48  Cycles of Concentration (COC) ▪ Cycles of Concentration (COC) ○ Also called “Concentration Ratio” (CR) is the number of cycles indicates the ratio of dissolved solids concentration in circulating water compared with those in make-up water. ○ COC can be calculated based on TDS, conductivity, Chloride, Silica or other trace dissolved solids. ○ Under steady-state condition, COC can be calculated based on flow rates Cooling Systems Training 49 Cycles of Concentration (COC) 200 ml 100 ml TDS = 100 TDS = 200 50 ml 25 ml TDS = 400 TDS = 800 COC = 1 COC = 2 COC = 4 COC = ?? Cooling Systems Training 50  Cycles of Concentration (COC) ▪ Why we need to increase and control COC? More water savings We have to 01 Lower Make-up Rate Chemical saving Sustainable solution study it and identify COC More water savings 02 Lower Blowdown Rate Chemical saving Sustainable solution Less chemicals & Water 03 Lower OPEX Better cooling efficiency Cooling Systems Training 51  Liquid Gas (L/G) Ratio ▪ Liquid Gas Ratio ○ Ratio between water and air mass flow rates. ○ Heat removed from the water must be equal to the heat absorbed by the surrounding air L(T1 – T2) = G(h2 – h1) L/G = (h2 – h1) / (T1 – T2) T1 = hot water temp (oC) T2 = cold water temp (oC) h = Enthalpy of air water vapor mixture at inlet wet bulb temp (h1) and outlet wet bulb temp (h2) Cooling Systems Training 52  Hydrex Calculations “Break” Cooling Water  Parameters for Calculations To calculate water consumption and mass balance for a cooling tower you require the below minimum information: Make-up Rate (M) Operational Blow down Rate (B) Recirculation Rate (CR) COC Differential Temperature (ΔT) Evaporation Rate (ER) System Design Windage or Drift Rate (W) Cooling Systems Training 54 Holding Time Index (HTI) ○ Holding time index (HTI) or half life of chemicals: is the time required for the concentration of any ion to dilute to 50% of its original concentration in a cooling tower. ○ Holding time index = half life of chemicals Cooling Systems Training 55  Langelier Saturation Index (LSI) ○ LSI is an equilibrium model derived from the theoretical concept of saturation and provides an indicator of the degree of saturation of water with respect to calcium carbonate - Corrosion 0 Scaling + Tends to dissolve solid Tends to precipitate a scale CaCO3 layer of CaCO3 LSI = pH – pHs pH is the measured water pH pHs = (9.3 + A + B) - (C + D) Cooling Systems Training 56  Langelier Saturation Index (LSI) Calcium Hardness pH 05 Minizmies corrosion but Major rule in LSI calculations increases scaling tendency when increeasing 01 04 TDS Temperature Affects ionic strength of water and its effect is more It increases scaling and in scaling corrosion tendency depending on LSI value 02 03 Water Alkalinity Increases scaling but minimizing corrosion LSI Calculator: D:\USER PROFILES\Documents\Softwares Cooling Systems Training 57 Which Water We Should Use? Brackish Water Potable Water (RO) TSE Sea Water Available Available Not always Not always Stable Quality Expensive available available High Scaling Stable Quality Variable Quality Stable quality Corrosive Low corrosivity High COC Highly corrosive Limited COC High COC Special Highly brackish treatments CAPEX Total Cost OPEX Cooling Systems Training 58 Cooling Water Treatments Water Treatment is the most important factor affecting the life and energy efficient operation of cooling towers equipment Water Treatment Targets ○ There are HTREE major concerns should be addressed in cooling systems: MIC n n io tio at ra rm rio es fo te al lm de sc ofi al d g bi an n er lin io g d in s an al in m os ou et th of al rr m of w n Sc Co ro of Bi tio lg n ita tio ia 1 2 3 ip er da ec ct i Ox Pr Ba Under-deposit corrosion Cooling Systems Training 61 Water Treatment Targets ○ The frequency of problems associated with water are classified as below: Type of cooling water system Once through Closed cooling Open cooling Corrosion ✔ ✔✔ ✔✔✔ Scale ✔ ✔ ✔✔✔ Bio-slime ✔✔ ✔ ✔✔✔ Cooling Systems Training 62 Water Treatment Targets ○ Below are common troubles in cooling systems.. Trouble Cause Shortened operation life of heat exchangers, piping, etc. General Corrosion Under-deposit corrosion Reduction of heat exchanger thermal efficiency Adhesion of scale and corrosion products, sludge Increase of pressure drop & reduction of circulation rate Adhesion of scale and corrosion products, (higher power consumption) sludge, clogging with foreign matter Leakage of products to the cooling system water Penetration due to corrosion or under-deposit corrosion Adsorption and waste of water treatment chemicals Corrosion products, slime, scale, sludge & suspended solids in cooling water Have you seen any in your plant? Cooling Systems Training 63  Corrosion in Cooling Systems Cooling Water Corrosion ○ Corrosion is a natural process that converts a refined metal into a more chemically-stable form such as oxide, hydroxide, or sulfide. ○ It is the gradual destruction of materials (usually a metal) by chemical and/or electrochemical reaction with their environment. ○ This type of damage typically produces oxide(s) or salt(s) of the original metal and results in a distinctive orange colouration. Cooling Systems Training 65 Corrosion ○ Does corrosion affects you? Your Your Your Your Environm Your Job Company Safety Pocket ent Globally = 3.0 $ trillion / 2022 (3.4% of GDP) Direct Losses > 300 $ Billion / Year in U.S. 300$ Billion = 300,000,000,000 $ 3% of Gross National product of U.S. Cooling Systems Training 66 Corrosion Cooling Systems Training 67 Corrosion Anode = Oxidation = Corrosion Galvanic Cell – Spontaneous Item Function Anode (Metal) Oxidation: Fe to Fe+2 Cathode (Metal) Reduction: O2 to OH- Water Droplet Electrolyte Cooling Systems Training 68 Corrosion Hydrex Cooling Systems Training 69 Where is the anode? B A A B B Cooling Systems Training A 70 Factors Affecting Corrosion ○ There are many factors affecting corrosion, but these are the ones related to water.. Water pH 1 Is a vital factor Temperature 2 Increases corrosion. Water Chemistry 3 Has variable effects Water Velocity It has complexed 4 mechanism & standard Metallurgy 5 It is a key base factor Cooling Systems Training Let us discuss briefly each factor.. 71 Corrosion Vs. pH ○ Corrosion is highly affected by pH. ○ Each metal (metallurgy) has its own behaviour with pH in specific water chemistry Cooling Systems Training 72  Corrosion Vs. pH Pourbaix Diagrams (potential/pH diagram) ○ Are maps showing the effects of pH on the form in which an element in a given oxidation state exists in natural water. Cooling Systems Training 73  Corrosion Vs. Temperature ○ Corrosion rates in cooling systems increases as water temperature increases, which requires more control. Temperature In general, for every 18°F in water temperature, chemical reaction rates double. Corrosion Rate Cooling Systems Training 74 Corrosion Control ○ Corrosion control in cooling system could utilize one of the below techniques: Monitoring Systems Cooling Systems Training 75 Corrosion Inhibitors ○ Corrosion inhibitors are chemicals dosed to cooling waters to protect system metallurgies from corrosion. ○ Two types of corrosion Inhibitors: PO4-3 ▪ Anodic Inhibitors ○ Protect bulk of metal surface by forming an oxide film MoO4-2 ○ Not require pH control SiO3-2 ○ Don’t promote bacterial growth ▪ Cathodic Inhibitors Zn ○ Stop cathodic reactions ○ Prevent corrosion from proceeding ahead Phsophonates Veolia recommends dual corrosion inhibitors for better protection Cooling Systems Training 76 Corrosion Monitoring - Coupons ○ Online corrosion monitoring systems are an automatic & fast corrosion rate measurement tools using electrochemical probes. Cooling Systems Training 77 Corrosion ○ Corrosion coupons provide an inexpensive means of on-line monitoring that will allow you to effectively measure the corrosivity and corrosion rate within your system. ○ It is ASTM D2688 approved method Cooling Systems Training 78  Scaling in Cooling Systems Scaling ○ Cooling water contains many different minerals & normally these minerals are dissolved in the water (TDS) ○ Under certain conditions minerals can come out of solution and form into hard, dense crystals called SCALE. Cooling Systems Training 80 Scaling ○ Why scaling is important to be controlled in cooling systems? Scaling Blockage of Under-deposit Insulating Films tubes & pipes Corrosion Reduces heat transfer Reduces flow rate Sever corrosion & pitting Cooling Systems Training 81 Scaling ▪ Can You give us examples of Scales or Deposits you have found before ?! ▪ Did your Heat Exchangers get shocked due to scaling? Cooling Systems Training 82 Common Scales In cooling systems (direct & indirect) there are common scales could be found which includes: Calcium Carbonate Calcium Sulfate CaCO3 Calcium Phosphate CaSO4 CaCO3 Magnesium Silicate Ferric Phosphate MgSiO3 FePO4 Zinc Carbonate ZnCO3 Cooling Systems Training 83 Scaling ○ Where commonly we found scales? Cooling Systems Training 84 Scaling Factors There are many factors affect the scaling tendency and amount includes: Water pH Total Dissolved Solids Temperature Water Alkalinity (HCO3, CO3, OH) How these factors affect scaling? How we can control scale? Cooling Systems Training 85  Scale Inhibitors Scale Inhibitors are chemicals dosed to cooling waters to keep the system free from scaling and deposition. There are three mechanisms of scale Inhibitors: Threshold Inhibition Mechanism Chemicals which , when used is sub-stoichiometric amount is capable of preventing the precipitation of salts from a supersaturated solution. Crystal Distortion Mechanism Chemical interference to normal crystal growth produces irregular crystal structure with poor scale forming ability Dispersion of Crystal Mechanism Chemical which can adsorb onto scale surface causing the particles to remain in suspension Cooling Systems Training 86 Scale Inhibitor Mechanism + - +- + + + + + - + - +- + - - + - - + - - + - + - +- - Growth - - - + - + - + - + -++- + -- + -+ - -+ + - - - - + - + -+ +- +- -+ + -+ - +- -+ + + + + + - + + - - - + - - - ++- +- - ++ +- - - -+ - ++ -+ + - A + + B - +- Supersaturation Nucleation Proto-nucleation C Crystals formation Cooling Systems Training 87 Scaling Studies - Laboratory Tests ▪ Veolia R&D team can support in the following lab tests: Scale Analysis Performance Chemical (XRD - XRF) Tests Optimization Identify scale type in Using PMAC (Block Optimize antiscalant MSF units (CaCO3, tubing) dosage when CaSO4, Mg(OH)2 Using Static mixing required method for scale Help in selecting inhibition % suitable cleaners (acid & alkaline) CaCO3 Mg(OH)2 CaSO4 Clay Temperat Inhibition Inhibition Inhibition Dispersio Price ure % % % n% Cooling Systems Training 88  Biofouling in Cooling Systems Biofouling Hydrex Cooling Systems Training 90 Biofouling Cooling Systems Training 91  Biofouling Biofouling problems are caused by the adhesion and accumulation of soft and muddy fouling composed of microorganisms such as: bacteria, algae and fungi, and inorganic matters like mud, sand & dirt. Biofouling problems are classified as: Type of fouling Definition Fouling including higher amount of microorganisms than inorganic matters: Slim adheres on heat exchanger tube surface, etc., with the adhesive force Slime of the sticky organic substances produced by microorganisms even under water flow condition. Fouling including higher amount of inorganic matters than microorganisms: Sludge Sludge is usually accumulated at the places of low water flow rate or water stagnancy. Cooling Systems Training 92 Biofouling Slime Cooling Systems Training 93 Biofouling Slime Cooling Systems Training 94 Thank You