Application of Ozone in cooling water treatment of Power plants

[Dr.M.V.R.N.Acharyulu]

In India, In general, Chlorine is being used as Oxidant in cooling water plant. Now a day pollution control boards insisting to adopt clean technologies like Ozonitation for cooling water treatment. I would like educate myself  on advantages, disadvantages of use of ozone in cooling water treatment of power plants. kindly educate on this issue 

   

[Sanjay Shevkar]

Sir give the consultancy and get a report done for you to take a decision !!!! hows that!

 

- Sanjay Shevkar

[Pragnesh Mehta]

Dear Dr.M.V.R.N.Acharyulu.

 

This is very Interesting and Long Subject. Here I put some of data regarding Cooling tower.

Ozone applications Cooling tower water

Cooling tower water requires extensive treatment. During cooling tower water treatment, three main factors must be controlled

• Corrosion of pipes and heat exchanger units
• Scaling in pipes and (mainly) in heat exchangers
• Microbial growth (bacteria, algae)

These three aspects cannot be viewed separately. For example, lower pH values can prevent scaling, but they increase metal corrosion. By means of ozone treatment, all these aspects can be controlled collectively, without further addition of chemicals.

Conventional treatment techniques are mainly applications of chemical biocides, corrosion inhibitors and scale inhibitors. Ozone is a reliable alternative that controls the above-mentioned factors sufficiently.

Scaling

Scale forms as a result of calcium and magnesium ion deposits on the units of a cooling system. This causes the formation of a core, which forms an isolation layer in heat exchangers. This negatively influences heat transport. Consequentially to water loss by evaporation, salt concentrations in the water increase. This process is called thickening. At a certain point, the saturation rate for these salts is reached, causing them to precipitate. This limits the number of times the cooling water can be recicled.
The thickening factor N is a measure for the increase in salt and ion concentrations in cooling water. As such, it indicates the number of times the water requires refreshment, in order to prevent salt precipitation.

A bio film can also be formed in the cooling water system, consequentially to clogging of microorganisms, such as algae. A bio film takes up ions that normally form micro crystals, which increases scaling. In time, inorganic and organic matter will thicken this core.

Ozone treatment limits scaling. Ozone is a disinfectant that decomposes bio film, causing ions to no longer be able to attach to it. This causes a decrease in scale formation. Even water with a high dissolved solids content can now be recicled, causing cooling water discharges to be decreased.

The only condition under which this system works, is that small rest concentrations of ozone must remain in the cooling water, to prevent further microbial growth that enhances scaling.

Corrosion

Each material has a limited life-span. The length of the life-span depends on the nature of the material and on environmental conditions. The first method of corrosion prevention is the choice for the most persistent material and a solid construction of the cooling system. Once the cooling water system is in use, corrosion can be prevented by alteration of the water quality. In practise, this is achieved by pH adjustment and alteration of the dissolved solids concentration. When these measures do not provide the desired result, corrosion-inhibitors may be added to the cooling water. However, corrosion-inhibitors are quite expensive, because of the supervision that must be carried out to quarantee the affectivity of the measure.

Another method to prevent corrosion is ozone application. Corrosion is mainly caused by microorganisms, which enhance corrosion forming conditions. Ozone limits microbial growth. Ozone also causes a certain electric current to occur in the water. This current causes metals to form a passive, corrosion-preventing film on the materials from its own oxides. Such a passivating oxidative film is found on stainless steel and aluminum. This film can only be formed at a certain water flow and on certain types of materials.

Various experiments have shown that corrosion always decreases when ozone is applied, usually by more than 50%.

Little ozone is required to form a corrosion-preventing film on metals. High dosages of zone can corrode some metals. In practise, about 0,1 to 0.5 g/m³ of ozone( based on water quality, Temperature) is dosed to recirculating water. The ozone that does not react with organic matter, decomposes to oxygen. There will be no toxic residues.

Microbial growth

One cannot prevent microbial growth in a water system. This is because we always use water and air that contains bacteria. During processes, bacteria can enter the water, as well.
Ozone is a stronger disinfectant than any other chemical. Ozone is the most efficient disinfectant for the deactivation of Legionella bacteria. Usually, one cannot thicken the water in organic water treatment preparations more than three to five times. This means that of each 1000 litres of suppletion water, at least 200 litres is carried off (20%).

When ozone is used for water treatment, the water can be thickened more than 5 times. This means that for each 1000 litres of water, no more than 200 litres is carried off. In practise, the water can be thickened to about 20 times. This means that for each 1000 litres of water, no more than 50 litres is carried off to the sewer. Only evaporation and splatter losses are filled up with fresh water in this case.

Applications and measures

Ozone application in cooling water treatment is a good option for water quality control in a cooling water system. Ozone leads to savings of:

• Anti-scaling and anti-corrosion agents
• Acid dosages
• Water use
• Storage and transport costs of chemical biocides
• Pump capacity (more efficient heat transfer; lower energy use; higher yield heat exchanger)

Ozone application can only be done adequately when certain factors are taken into account:

• Water quality; suppletion water for cooling towers that is hard or has a high COD is less suitable for ozone treatment
• The time that ozone remains in the system. The half-life of ozone is usually less than 10 minutes in a cooling tower. To gain a significant residual concentration of ozone, the primary ozone concentration must be sufficient.
• Cooling water temperature. Ozone solubility and the half-life of ozone decrease at higher cooling water temperatures. This limits cooling water temperature for adequate application of ozonation. The limit is usually a cooling water temperature of 45 ^oC.
• Material choice. The material that a cooling tower consists of must be ozone-resistant.

As a Manufacturere of Ozone Generator, I'm trying to give overview but it has more data, case study and calculation which available any time on request. 

Hope above data is useful to you.

Regards,

Pragnesh Mehta

QMAX GREENTECH

[e-mail]

 

 

 

[Rajesh Kumar Garg]

I thought you were giving your feed bck.....lol it was just a copy/paste trick.....:):)

Its better to view the link below -

http://www.lenntech.com/library/ozone/cooling/ozone-applications-co...

Rgds,

garg rk.

Pragnesh Mehta said:

Dear Dr.M.V.R.N.Acharyulu.

 

This is very Interesting and Long Subject. Here I put some of data regarding Cooling tower.

Ozone applications Cooling tower water

Cooling tower water requires extensive treatment. During cooling tower water treatment, three main factors must be controlled

• Corrosion of pipes and heat exchanger units
• Scaling in pipes and (mainly) in heat exchangers
• Microbial growth (bacteria, algae)

These three aspects cannot be viewed separately. For example, lower pH values can prevent scaling, but they increase metal corrosion. By means of ozone treatment, all these aspects can be controlled collectively, without further addition of chemicals.

Conventional treatment techniques are mainly applications of chemical biocides, corrosion inhibitors and scale inhibitors. Ozone is a reliable alternative that controls the above-mentioned factors sufficiently.

Scaling

Scale forms as a result of calcium and magnesium ion deposits on the units of a cooling system. This causes the formation of a core, which forms an isolation layer in heat exchangers. This negatively influences heat transport. Consequentially to water loss by evaporation, salt concentrations in the water increase. This process is called thickening. At a certain point, the saturation rate for these salts is reached, causing them to precipitate. This limits the number of times the cooling water can be recicled.
The thickening factor N is a measure for the increase in salt and ion concentrations in cooling water. As such, it indicates the number of times the water requires refreshment, in order to prevent salt precipitation.

A bio film can also be formed in the cooling water system, consequentially to clogging of microorganisms, such as algae. A bio film takes up ions that normally form micro crystals, which increases scaling. In time, inorganic and organic matter will thicken this core.

Ozone treatment limits scaling. Ozone is a disinfectant that decomposes bio film, causing ions to no longer be able to attach to it. This causes a decrease in scale formation. Even water with a high dissolved solids content can now be recicled, causing cooling water discharges to be decreased.

The only condition under which this system works, is that small rest concentrations of ozone must remain in the cooling water, to prevent further microbial growth that enhances scaling.

Corrosion

Each material has a limited life-span. The length of the life-span depends on the nature of the material and on environmental conditions. The first method of corrosion prevention is the choice for the most persistent material and a solid construction of the cooling system. Once the cooling water system is in use, corrosion can be prevented by alteration of the water quality. In practise, this is achieved by pH adjustment and alteration of the dissolved solids concentration. When these measures do not provide the desired result, corrosion-inhibitors may be added to the cooling water. However, corrosion-inhibitors are quite expensive, because of the supervision that must be carried out to quarantee the affectivity of the measure.

Another method to prevent corrosion is ozone application. Corrosion is mainly caused by microorganisms, which enhance corrosion forming conditions. Ozone limits microbial growth. Ozone also causes a certain electric current to occur in the water. This current causes metals to form a passive, corrosion-preventing film on the materials from its own oxides. Such a passivating oxidative film is found on stainless steel and aluminum. This film can only be formed at a certain water flow and on certain types of materials.

Various experiments have shown that corrosion always decreases when ozone is applied, usually by more than 50%.

Little ozone is required to form a corrosion-preventing film on metals. High dosages of zone can corrode some metals. In practise, about 0,1 to 0.5 g/m³ of ozone( based on water quality, Temperature) is dosed to recirculating water. The ozone that does not react with organic matter, decomposes to oxygen. There will be no toxic residues.

Microbial growth

One cannot prevent microbial growth in a water system. This is because we always use water and air that contains bacteria. During processes, bacteria can enter the water, as well.
Ozone is a stronger disinfectant than any other chemical. Ozone is the most efficient disinfectant for the deactivation of Legionella bacteria. Usually, one cannot thicken the water in organic water treatment preparations more than three to five times. This means that of each 1000 litres of suppletion water, at least 200 litres is carried off (20%).

When ozone is used for water treatment, the water can be thickened more than 5 times. This means that for each 1000 litres of water, no more than 200 litres is carried off. In practise, the water can be thickened to about 20 times. This means that for each 1000 litres of water, no more than 50 litres is carried off to the sewer. Only evaporation and splatter losses are filled up with fresh water in this case.

Applications and measures

Ozone application in cooling water treatment is a good option for water quality control in a cooling water system. Ozone leads to savings of:

• Anti-scaling and anti-corrosion agents
• Acid dosages
• Water use
• Storage and transport costs of chemical biocides
• Pump capacity (more efficient heat transfer; lower energy use; higher yield heat exchanger)

Ozone application can only be done adequately when certain factors are taken into account:

• Water quality; suppletion water for cooling towers that is hard or has a high COD is less suitable for ozone treatment
• The time that ozone remains in the system. The half-life of ozone is usually less than 10 minutes in a cooling tower. To gain a significant residual concentration of ozone, the primary ozone concentration must be sufficient.
• Cooling water temperature. Ozone solubility and the half-life of ozone decrease at higher cooling water temperatures. This limits cooling water temperature for adequate application of ozonation. The limit is usually a cooling water temperature of 45 ^oC.
• Material choice. The material that a cooling tower consists of must be ozone-resistant.

As a Manufacturere of Ozone Generator, I'm trying to give overview but it has more data, case study and calculation which available any time on request. 

Hope above data is useful to you.

Regards,

Pragnesh Mehta

QMAX GREENTECH

[e-mail]

 

 

 

[Pragnesh Mehta]

Dear Mr. Rajesh,

Question is
" Application of Ozone in cooling water treatment of Power plants "

I found very comprehensive reply for that otherwise I have enough data which simply difficult to copy here and in my answer I never told that this data is my own.

I understand this platform is for sharing views, idea, experience and knowledge to understand problem or application Much more better way and find better solution for the same.

I am more then happy if someone has answer which different from my reply and that sure improve all of our knowledge.

We are at last enough mature to get benefit of such wonderful platform instead of criticise others.

[KRISHNAKUMAR IYER]

We are manufacturing Chlorine Di Oxide & Nascent Oxygen Molecules... which in Technical is liquid form of Ozone. We are catering to similar industry.

Please call Krishnakumar Iyer-Hyderabad-

09849026065

[KRISHNAKUMAR IYER]

Cooling Towers & Closed Systems - Chlorine Dioxide

 

Cooling Towers - The use of chlorine dioxide (ClO2) in cooling towers, closed loops and cooling water systems can greatly assist in the control of Legionella bacteria (the causative organism for Legionnaires' disease), algae, planktonic and sessile bacteria, biofilm and scale. This highly effective disinfectant can help maintain legislative compliance and system safety; and the efficiency of heat exchanger surfaces, reservoir intakes and ancillary equipment. All cooling water treatment programmes, if they are to be completely effective must consider the following three components: Microbiological control. Scale and deposit control. Corrosion control. Traditional oxidising agents such as chlorine and bromine suffer from pH constraints and corrosion problems which reduces their effectiveness. Chlorine dioxide however, is significantly more stable across a wider range of pH conditions than other oxidising biocides; and it is compatible with most water treatment chemistry. BIOKCIDE chlorine dioxide products help to control Legionella bacteria, algae, planktonic and sessile bacteria; and biofilm in cooling towers, closed loops and cooling water systems. In the UK, the Building Services Research and Information Association (BSRIA) has recommended chlorine dioxide as the best available technology for the control of Legionella bacteria in hot and cold water systems. Why is it important to control biofilm in such systems? Biofilm creates an environnment that helps to protect unwanted and harmful colonies of bacteria (including Legionella bacteria) making biological control significantly harder. Biofilm also acts as an insulator causing deterioration in general heat transfer properties. It creates fouling and corrosion problems by accumulating scale in pipework and equipment. Biofilm also creates an environment that promotes the growth of anaerobic microorganisms which in turn increases microbiologically induced corrosion (MIC) problems. BIOKCIDE chlorine dioxide products offer a number of operational and cost saving benefits including: Highly effective against Legionella bacteria and stubborn biofilm. Excellent biological control. Savings on water and wastewater costs from reduced water consumption. Minimal salt build up; reducing potential corrosion problems. Reduced maintenance costs with longer operating cycles between "blow downs". Improved system performance with reduced accumulated scale on heat transfer surface components.  Technical support and advice BIOKCIDE work closely with a diverse range of organisations; intelligently combining advanced treatment technologies with practical solutions to resolve complex issues. If you have a cooling tower or cooling system related project you would like to discuss with us, or require technical support and assistance; or if you simply have a question about one of our chlorine dioxide technologies please contact one of our specialist advisors using our Technical Support page or call us on 09849026065.