Industrial cooling water A Study by Manan Upadhyay Shani Pandya Proff. Himanshu Choksi School of Technology (PDPU) Dr.S.K.Shukla Hydro-Chem. (Technical director)

Industrial Cooling Water- A Study Abstract Water is used as a coolant in various recirculation cooling systems due to its availability, low cost and effective heat transfer properties. But at prevailing temperature in cooling system the main problem associated with cooling water are corrosion, scaling, fouling and microbiological growth ,which, if left untreated can lead to reduce operating efficiency, increased maintenance cost, loss in heat transfer efficiency and energy and ultimate shutdown. In this paper we are first going to discuss why water is so important in industry, which type of problem we face in industrial cooling water system, then we are going to discuss evaluation and control of that problems & how vital role water chemistry play for prediction of corrosion and scale. Also we are going to discuss product evaluation of CORONIL – 202 and how it is helpful to resolve associated problem. 22/12/2012 Industrial Cooling Water- A Study

The choice for water as coolants is because of….. Readily available in plenty Inexpensive Easily handled Carry large amount of heat per unit volume Does not expand or compress significantly within normally encountered temperature ranges Does not decompose 22/12/2012 Industrial Cooling Water- A Study

Problems encountered, if Recirculating Water is not treated….. Corrosion of metals in contact with cooling water Deposition on cooling surfaces Microbiological growth in the cooling tower and deterioration of cooling tower timber. Fouling of heat transfer surface Pollution of environment 22/12/2012 Industrial Cooling Water- A Study

Untreated Recirculating Water can cause .. Reduced operating efficiency Increased maintenance cost Loss in heat transfer efficiency and energy Choking of water passage, increase pressure drop Hot-spot causing equipment failure Reduced output Increased pumping cost Necessity of frequent cleaning Frequent shutdown, loss in manpower and production 22/12/2012 Industrial Cooling Water- A Study

Problems associated with Cooling Water 1.corrosion Types of corrosion. Pitting or localized attack Uniform Stress corrosion cracking Tuberculation Factors affecting corrosion Chemical Factors pH Dissolved solids Dissolved gases Suspended solids Microbial growth Physical Factors Relative areas Temperature Velocity Heat transfer Metallurgical impacts 22/12/2012 Industrial Cooling Water- A Study

Industrial Cooling Water- A Study Continue.. 2. Scaling Scaling can cause the following problems : Reduced or uneven heat transfer Hot – spot, causing equipment failure Poor corrosion inhibition Reduced output Increased pumping cost Necessity of frequent cleaning Some of the common scales are : Calcium Carbonate Calcium Sulphate Silicates Calcium Orthophosphate Magnesium Salts Iron Salts Factors that influence scaling : Temperature pH or Alkalinity Solubility 22/12/2012 Industrial Cooling Water- A Study

Industrial Cooling Water- A Study Continue.. 3. Fouling Fouling is the deposition of suspended matter other than scales. These are water insoluble and can be water borne or air borne. Some of the common foulants are: Dirt and Silt Sand Corrosion products Natural organics Microbial matter Extent of fouling depends on: Water characteristics Temperature Velocity Microbial growth Corrosion product Oil 22/12/2012 Industrial Cooling Water- A Study

Industrial Cooling Water- A Study Continue.. 4. Microbiological growth Excessive growth of microscopic organism which can cause following problems : Reduce heat transfer or restrict circulation in heat exchangers. Plug tubes in heat exchangers, causing emergency shutdown and loss of production. Deteriorate metal via under deposit corrosion. Destroy cooling tower timber. 22/12/2012 Industrial Cooling Water- A Study

Industrial Cooling Water- A Study Continue.. Basic Microorganism Algae Green algae (Chlorophyta) Blue green algae (Cyanophyta) Fungi Filamentous mold Yeast like growth Bacteria Aerobic capsulated Aerobic spore forming Temperature Phosphorous compound Dirt Process leaks such as Ammonia, Alcohols, Ethanolamine, Urea, Petroleum etc. Oil and fatty contaminants Factors affecting Microbiological growth 22/12/2012 Industrial Cooling Water- A Study

Scale and corrosion indices Langelier’s Saturation Index (LSI) Ryznar’s Stability Index (RSI) Puckorius Practical Scale Index (PSI) All these three indices are based on pH of saturation (pHs). The value of pHs can be calculated from the from the following formula. pHs = (9.3 + A + B) – (C+ D) A = Total dissolved solids (mg /I) B = Temperature of bulk water (0C.) C = Calcium hardness as CaCO3 (mg / I) D = Total alkalinity as CaCO3 (mg / I) 22/12/2012 Industrial Cooling Water- A Study

Scaling severity of keyed indices LSI* PSI* / RSI* Condition ________________________________________________________ 3.0 3.0 Extremely Severe 2.0 4.0 Very Severe 1.0 5.0 Severe 0.5 5.5 Moderate 0.2 5.8 Slight 0.0 6.0 Stable Water** -0.2 6.5 No scaling, very slight tendency to dissolve scale -0.5 7.0 No scaling, slight tendency to dissolve scale -1.0 8.0 No scaling, moderate -2.0 9.0 No scaling, strong tendency -3.0 10.0 No scaling, very strong LSI = Langelier Saturation Index RSI = Ryznar Stability Index PSI = Puckorious Practical Scale Index No scaling, no tendency to dissolve scale 22/12/2012 Industrial Cooling Water- A Study

Role of Water Chemistry in prediction of Corrosion and Scale Langelier and Ryznar indices give satisfactory results but there are some disputes. Water with positive L.I. can be corrosive and negative L.I. can be noncorrosive. To make system free from corrosion ratio of hardness and chloride of 2, and alkalinity and chloride + Sulphate ratio of 5 is desirable. L.I. require modification by incorporating chloride, sulphate, dissolved oxygen and exposure hr. etc. 22/12/2012 Industrial Cooling Water- A Study

Evaluation of Problems 1.Corrosion Non heat transfer loop (weight loss by coupons) Electrical resistance method Test heat exchanger 22/12/2012 Industrial Cooling Water- A Study

Industrial Cooling Water- A Study 2.Scaling Perforated coupons Visual observations of heat exchangers Test heat exchanger Scalometer 22/12/2012 Industrial Cooling Water- A Study

Evaluation of Problems 3. Microbiological growth Visual observation Total bacteria count Biofouling test unit Evaluation of Problems 22/12/2012 Industrial Cooling Water- A Study

Corrosion Control The general concepts for corrosion control are: a. Blow down b. Chemical treatment Estimated performance of Various blends No. Treatment %Corrosion inhibition 1. Chromate-Zinc-Polyphosphate 95 2. Chromate-Zinc-Polyacrylate 95 3. Chromate-Zinc-Polyacrylate 90-95 4. Azole-Zinc-Polyphosphate 80-90 5. Azole-Zinc-Diphosphonate 80-90 6. Azole-Zinc-Phosphonate-Polycrylate 85-90 7. Polyphosphate-Phosphonate-Polyacrylate 75-80 8. Polyphosphate-Phoaphonate-Polyacrylate 70-80 9. Ferrocyanide-Zinc-Polyphosphate 60-70 10. Lignin-Zinc-Polyphosphate 22/12/2012 Industrial Cooling Water- A Study

Scaling and Fouling control Controlling the cycle of concentration thereby limiting the concentration of the scale forming salts. Removing or reducing the minerals before they enter the system by using softer. Acid feeding Mechanical means like increasing the water velocity and designing exchangers with large surface areas. Most important of all is to treat with chemicals to prevent scale (practical and cost effective) Chemical treatment Organophosphonate + Low molecular weight anionic polymer Properties Hydrolytic stability Sequestration Threshold inhibition Crystal distortion Dispersion 22/12/2012 Industrial Cooling Water- A Study

Industrial Cooling Water- A Study Antiscalents Aminotris (Methylene Phosphonic Acid) 1,Hydroxyethylidene 1, 1, Diphosponic Acid Ethylenediamine Tetra (Methylene Phosphonic Acid) Hexa Methylence Diaminetetra (Methylene Phosphonic Acid) Diethylenetriamine Penta (Methylene Phosphonic Acid) 2 – Phosphono Butane – 1,2,4 Tricarboxylic Acid Polymino Polyether Methylene Phosphonic Acid Phosphino Carboxylic Acid Dispersants Polyacrylic acid Polymaleic acid Polyacrylamide Acrylic acid : Sulphonic acid : Sulphonated styrene ter-polymer Polyaspartate 22/12/2012 Industrial Cooling Water- A Study

Microbiological growth control using suitable Biocides. Common Biocides Chlorine Chlorine Dioxide Para Toluene Sodium Sulfonchloramide 1,3 – Dichloro – 5,5-DimethyI Hydantoin N-Chloro Succinimide Cyanuric Trichloride Methylene Bisthiocyanate Chloroethylene Bisthiocyanate Acrolein Copper Citrate Copper Chelate of Glycine Bis (tri-n-butyltin) Oxide Dodecyl Guanidine Hydrochloride Tri and Pentachloro Phenols Sodium Penta Chloro Phenate N-dodecyl Benzy – N,N,N-triethyl Ammonium Chloride. Zinc Dimethyl Dithiocarbamate 2,2 – Dibromo-3-Cyanoacetamide 2,3 – Dichloro naphthoquinone Isothiazolinone 22/12/2012 Industrial Cooling Water- A Study

Industrial Cooling Water- A Study Product Evaluation Product : CORONIL – 202 Corrosion Data Metal Used : Mild Steel Density : 7.8 g/cc Area of specimen : 5.00in2 Exposure hours : 72 Stirring : 600 RPM Temperature : 450C + 10C 22/12/2012 Industrial Cooling Water- A Study

Industrial Cooling Water- A Study Results Process Soft Synthetic Water water cooling water Blank Weight loss (mg) 198.80 313.00 233.60 Corrosion rate (mpy) 36.34 59.31 42.35 Formulation ( CORONIL – 202 ) Weight loss (mg) 3.0 5.1 17.1 Corrosion rate (mpy) 0.5977 0.972 3.1 % corrosion Inhibition 98.35 98.36 92.60 22/12/2012 Industrial Cooling Water- A Study

Product Evaluation (Contd.) Product : CORONIL – 202 Water analysis Process Soft Synthetic cooling Water water water pH 7.84 6.80 8.5 Conductivity (micro mho) 430 31 1100 TDS, ppm 262 24 640 Ca-hardness, ppm 74 6 196 Mg-Hardness, ppm 70 Nil 100 Total hardness, ppm 144 6 296 P.Alkalinity, ppm Nil Nil 9.6 M.Alkalinity, ppm 124 6 132.4 T.Alkalinity,ppm 124 6 142 Chloride as CI 28.4 8.52 217.9 Sulphate as so4 6 10 20.1 Calcium carbonate Inhibition Conditions Calcium carbonate : 400PPM Time : 20 Hours Temperature : 60 + 20C pH : 10 + 0.2 % Inhibition : 97.36 (Minimum) 22/12/2012 Industrial Cooling Water- A Study

Product Evaluation (Contd.) Product : CORONIL – 202 (Contd.) Calcium Sulphate Inhibition Conditions Calcium Sulphate : 13000 ppm Temperature : 60 + 20C Time : 20 Hours pH : 8 + 0.2 % Inhibition : 98.2 (Minimum) Dispersive Power Kaolin Clay : 4000 ppm Calcium Carbonate : 2000 ppm Standing time given : 48 hours % Dispersion : 92 (Minimum) 22/12/2012 Industrial Cooling Water- A Study

Industrial Cooling Water- A Study Advantages of Product CORONIL-202 Calcium Carbonate Crystals grown (static CaCO3 threshold inhibition test conditions) in the absence of CORONIL Distorted Calcium Carbonate Crystals grown (static CaC03 threshold inhibition test conditions) in the presence of CORONIL 22/12/2012 Industrial Cooling Water- A Study

Industrial Cooling Water- A Study Calcium Sulphate Crystals grown (static CaSO4 threshold test condition) in the absence of CORONIL Distorted Calcium Sulphate Crystals grown (static CaSO4 threshold test condition) in the presence of CORONIL 22/12/2012 Industrial Cooling Water- A Study