Comparison of Ozone treatment vis-a-vis chemical treatment of cooling tower
|Parameter||Ideal||Ozone Treatment||Chemical Treatment|
|TDS||With Ozone- 2000 to 3000ppm with chemicals – upto 1500ppm only||No increase other than due to evaporation ;Operation under high TDS conditions possible with little risks||Besides evaporation, constant build up owing to addition of chemicals necessitation frequent bleeding and so, water loss|
|Chloride||Below 200 ppm||No increase other that due to evaporation||Besides evaporation, constant build up owing to addition of chemicals necessitating frequent bleeding and so, water loss|
|Scaling||Langlier: not above + 0.5 Rhiezner : not above 7.5||Easily maintainable, scaling is reduced as the organic matrix for seeding is destroyed by Ozone||Heavy scale buildup in spite of chemicals, leading to frequent overhaul and wire scrubbing of condenser tubes.|
|De - Scaling||7.5 - 9.5 LPM||Ozone destroys scale already formed by breaking the organic matrix||Questionable action .De scaling agents only add to the problem|
|Heat transfer efficiency||No loss in efficiency||No loss in efficiency with reduction in scaling upto 10 to 15% energy saving can be expected providing considerable savings in operation costs||Considerable loss owing to poor and erratic control. Scale build up reduces heat transfer efficiency|
|Corrosion||Langlier : not below -0.5 Rhiezner : not below 6.5 Industry standard - 5 mpy||Easily maintainable. Ozone acts similar to Chromates used in earlier corrosion inhibitor process - passivates the metal surfaces||Difficult to maintain. Heavy does of chemicals will be required, which upset other critical parameters drastically|
|Algae||Nil in water||Nil in water under controlled conditions||Highly Dependant on chemicals addition|
|Frothing||Nil||Nil. No Organic sediments to cause froth.||Copious due to quaternary compounds used as biocides as well as other organic|
|Bacterial count||Below 10000 cfu / ml||About 1000 cfu / ml counts is a possibility .||Erratic bacterial counts .Often builds up above 10000 cfu|
|Legionella||Nil||Nil||Very difficult to eradicate. Resistant to most chemicals and killed by chemicals too toxic to humans. Ironically chemicals commonly used in tower maintenance promote growth of Legionella|
|Sludge||Minimal. Water clear||Water clear. High-density sediments. Easily filterable.||Increased sludge. Low density sediments not easily filterable.|
|Blow down||To control TDS||No controlled blow down will be required Water savings||Controlled blow down requires large amounts of make up water increing cost of raw water treatment and effluent treatment costs|
|COC||As high as possible to save water costs||High COC , sometimes even above 25 cycles possible with good make up water quality||Low COC s .Costs on water, raw water treatment and Blowdown water treatment costs|
Cooling Tower Water Before and After Ozonation
COOLING TOWER GALLERY
Power plants are water guzzlers. In India more than 80% of the industries water consumption is by power plants. Loads of money is spent on chemical treatment of cooling towers. Millions of gallons of highly contaminated and polluted blow down water are discharged from these power plants. This is of great concern, especially when India is planning a massive growth in the power plant sector in the next 5-6 years. Each 250 Mega watt power plant blows down an average of 13 lakhs M3 of polluted water every year. With an approximate additional requirement of 2 Lakhs Mega Watt of power requirement in the next 5 years, we would be wasting atleast an additional 1000 Billion liters per year.
Adopting of a clean technology that can save water and allow the possibility of reusing the water will be the single and most important consideration for the designers of power plants.
Using Ozone as a primary biocide comes as a boon to power plants. The power plant operator will drastically reduce the consumption of chemicals required for the conventional treatment. Lots of water is saved as the use of ozone permits operation under higher cycles of concentration. Further more whenever blow down is made, the water will be less polluted as it does not contain the dangerous chemicals such as chromate, phosphates etc that are added in conventional treatment. Very often the operator is not aware of the composition other chemicals that are used during routine treatment.
OTSIL can offer the following consultancy services to Power plants
INITIAL FEASIBILITY REVIEW - PHASE I
Certain physical aspects of a prospective client's cooling system should be reviewed in advance of any proposal submittals to the client to ensure any potential future problems are minimized.
1. Review of Cooling Tower and Plumbing Turnover Times - Necessary to ensure adequate ozone residuals can be obtained throughout the cooling circuit.
2. Review of Heat Exchanger Process Temperatures and Flow Rates - Necessary to ensure that no low flow or high temperature conditions exist.
3. Review of Makeup Water Chemistry - Necessary to calculation maximum and minimum safe operating cycles of concentration
4. Review of Possible Contamination Sources - Necessary to identify possible prevention solutions.
SYSTEM DESIGN AND SPECIFICATION - PHASE II
1. Performance of Bubble-Froth Mixing Calculations and Preparation of First Draft Sketch of Side stream Mixing Loop and Basin Distribution Plumbing Flow Schematic Drawings
2. Performance of Injection Loop Pressure Drop Calculations and Preparation of First Draft Sketch of Injection Detail Drawings.
3. Assistance in Preparation of Equipment Layout and Plan View Drawing
4. Assistance in Preparation of List and Generic Description of Other Major System Components and Recommended Instrumentation
Phase III :Detailed Engineering, Equipment Supply , Erection, Commissioning
Phase IV : Training of operators, Maintenance of Ozone System, Trouble shooting, Cooling Tower Chemistry with respect to Ozone
Phase V: Optional: Operation and Maintenance
OTSIL IS ALSO IN A POSITION TO PROPOSE COOLING TOWER OZONATION SYSTEM UNDER BOOT BASIS