The cooling tower is a major component of any process in any plant. Hence, it is expected that cooling towers should work effectively and efficiently in any given conditions or in all conditions.
A poorly operated cooling tower reduces chiller/boiler/heat exchanger efficiency and eventually leads to system failure. Thus, we need to understand the importance of the cooling tower in any industrial plant.
In spite of their impact on the plant facilities, cooling towers are among the most neglected equipment in many plants or factories. Hence, it is important to understand a cooling tower’s role and put efforts into keeping it operating at peak performance levels. We may know the steps to be taken to improve the performance of the cooling tower while extending its service life.
The role of the cooling tower is exactly like the role of the carburettor in the car. The role of carburettor is to mix just the right amount of gasoline with air so that the engine runs properly. If there is not enough fuel mixed with the air, the engine runs lean and either will not run or potentially damage the engine.
It is a genuine requirement of the car owner to service his car periodically and keep the carburetor of his car intact so that his car gives him the best result. Similarly, the plant in charge/works manager should know the importance of cooling towers and then he should take care of the cooling towers in the plant to get the best result.
So, there is a chemical-free, self-cleaning cooling recirculating water treatment system that will keep required water parameters under control and will ensure maximum energy efficiency in the process as well as saving quantity of water thus reducing operation costs as described below:
- Saves energy – boiler/heat exchanger energy as well as boiler fan
- 100% saving on chemicals
- Improvement in productivity and reduction in downtime
- Prevent corrosion, further scaling, micro-organism growth and spread of
airborne bacteria in the cooling tower water distribution loop
- Control of biological growth
This is the best replacement for conventional chemical dosing systems to treat cooling recirculating water to maintain the required parameters.
What does a chemical dosing system do in cooling recirculating water treatment
Chemical dosing system doses different chemicals in the recirculating water so that required water parameters are maintained to keep the cooling tower operating at its optimum parameters. Thus, the chemical dosing system protects the cooling tower and other equipment in the loop of the water distribution system from scaling, corrosion, micro-organisms, bacteria, and algae growth. There are some typical chemical doses like corrosion inhibitors, scale inhibitors, and the pH of recirculating water. Some chemicals are dosed to kill or control micro-organisms, bacteria, and algae growth.
Unfortunately, the chemical dosing system is not an environmentally friendly system. it solves problems like scaling, corrosion, bacteria, pH, etc. but at the same time, it is a cause of many problems
It has many recurring costs such as:
- Recurring chemical costs
- Recurring cost of inventory of chemicals
- Recurring cost of space to stack the chemicals
- Recurring cost of labour
On the other hand, a self-cleaning chemical-free cooling recirculating water treatment system maintains the water parameters so that there is no corrosion and no scaling in the recirculating water loop. It will maintain the pH of water as well as kill organic components like algae, bacteria, etc, It will happen without using any kind of chemicals.
Since it is a zero chemical system, there will be an increase in c.o.c., thus reducing the blow-down of water. The savings will be 50-70% of blow-down water.
A study says that there will be expenses of 25 lacs INR in 5 years down the line which is inclusive of the purchase cost of the chemical dosing system. On the other hand, there will be savings of 10 lacs INR after recovery of the purchase cost of the chemical-free self-cleaning cooling recirculating water treatment system. Overall savings will be 35 lacs INR on one cooling tower in the span of 5 years down the line. This is a case of 1 cooling tower of 250 tr. The system can be retrofitted to existing cooling towers too.
There are many installations of cooling towers at one location as well as different locations in India or around the globe. So, if one cooling tower saves 25 lacs in 5 years with the chemical-free water treatment system, just imagine the savings, if installations are 5, 10, 20, 50 and 100 numbers at different locations all over India. Then there will be savings of 125, 250, 500, 1250 or even 2500 lacs respectively in every 5 years. The savings will keep on increasing as years pass until the chemical-free system is in use. The value may vary based on the capacity.
What is a chemical-free self-cleaning c.t. recirculating water treatment system?
The system is specially designed and suitable for all types of cooling towers like natural draft, mechanical draft, closed loop, open loop etc. in all industrial sectors like chemical, pharmaceuticals, steel, power, automobile etc.
The system is:
- Self-cleaning mechanism
- That enables low maintenance
- It saves time and labour costs
- Eliminates scale
- Scaling happens in the reactor on the skid so no scaling in the water distribution loop, protecting c.t. from deposits.
- Control corrosion:
- A slightly high pH environment does not cause scaling and protects the cooling tower from corrosion.
- Generates free chlorine:
- It eliminates bio-films, algae and bacterial growth including legionella.
- Saving water:
- Works on high conductivity levels up to 8500 micro-siemens
- More than 50-70% of blow-down water can be saved.
- It is the electrolysis principle with the electrochemical reactor, electrolyzers of anodes and cathodes
- The process causes the dissociation of the salts in the water, into ions, which precipitates all scale-forming ions not just calcium and magnesium but also silica, ferrous, manganese etc. because of the high pH environment in the reactor
- Cations are attracted towards the cathode and anion towards the anode with titanium with proprietary platinum group precious metal bonding on the surface. Calcium is the main scale builder ion in the water combined with the carbonate present in the water and forms a soft scale that is actually attracted by the cathode
- A high pH environment is created at the cathode during the electro-chemistry
- Chlorides, naturally present in the water, are transformed into free chlorine or hypochlorite. Radical oxygen, ozone and hydrogen peroxide are also being produced in the electrolysis process. Chlorides combine with ozone and oxygen to control microbes, algae and bacteria
- Recirculating water pH never changes
- The scraper brush and drain valve in the system reactor remove the precipitated scale and other sediments and pollutants from water in the tank which controls the bleeding ground for the development or proliferation of micro-organisms. removal of scale deposits is automatic and can take place several times a day according to the feed water quality.
The performance measuring criteria of the speciality of the chemical-free system are:
- Excess mineralization causing scale /fouling will consistently be removed, significantly reducing shutdown due to fouling. The scale will be deposited in the reactor instead of the water distribution circuit of the cooling tower. The scale deposited is accumulated dirt
- It will continuously remove accumulated dirt. A high-performance sand filter cleans water and captures dust from the system
- The historic scale within the water circuit will be removed over a period of six or more months. Both fouling and scale removal will provide measurable improvement in energy efficiency
- Significantly reduce corrosion levels down close to zero ppm iron from water and likely eliminate mechanical and/or chemical cleanings and corrosion repair
- Bio-contamination will be controlled by biocide created naturally during the electrolysis process in tower water. There will be no need for chemical additives. Colony-forming units will be reduced to a fraction of the acceptance level
- Increase coc to up to conductivity 8500 micro-siemens. One can achieve 10- 12 cycle times
By applying electrical power between the anode and cathode, a chemical reaction is activated and an electrolysis process takes place. Water from the cooling tower pond is circulated through the electrolysis scale remover reactor. Due to the electrolysis process, the floating calcium molecules get deposited on the cathode and the water returns to the process, reducing calcium.
The main ingredients of scale in water systems (MgCO3, CaCO3, Mg (OH)2, SiO2) are almost completely removed from the water in this process.
Chlorine in water forms hypo-chlorous acid (HOCl) and hydrochloric acid (HCl). When this solution of HOCl and HCl reacts for a sufficient time with an excess of limestone (calcium carbonate) the reaction is:
Typical mineral scales in hot and cold domestic water distribution systems and also in evaporative cooling systems are largely calcium carbonate. Therefore, injecting a solution, even a dilute one, of HOCl and HCl, should produce the same reaction.
In the presence of an excess of calcium carbonate (nearly always the case in scaled water distribution and recirculation systems) and an excess of calcium bicarbonate indigenous to the water supply, the HCl would react as follows:
2HCl + Ca(HCO3)2 = CaCl2 + 2H2O + 2CO2
Calcium chloride and carbon dioxide solubility are rather high, so these reactions of HOCl and HCl tend to decompose the calcium carbonate scale to form rather soluble calcium chloride.The reaction of HCl with bicarbonate alkalinity should result in a reduction of alkalinity of about a 1 ppm HOCl to 1 ppm HCO3 ratio. This would have a rather insignificant effect on pH, but any pH reduction could aid the calcium carbonate resolution rate.
Installation at the site:
ROI of the system
|Based on data provided by one of the customers|
|Calculation for cooling tower 250 tr||Chemical free system||Chemical dosing system||Remark|
|Flow Rate||100 m3/hr||Automatic|
|Amount in Rupees|
|Chemical purchase||at 0.11 m3/hr||-96000||96360||96360||You may check the actual chemical|
|Saving on the water||at 90/m3||-49500||49500||49500||Your claim of blowdown|
|Saving on labour||at 15000pm||-180000||180000||180000||Considered minimum labour cost|
|Electricity saving||at 7/kw||-183960||-183960||-183960||It is considered for both the|
|Expenses 1 year||Total savings on chemicals, labour, blow-down water, and energy every year||590540||541900||141900||Though investment is Rs 9L|
|Expenses 2 year||-325500||325500||325500||The expenses on chemicals, water and labour with the chemical dosing system, are savings on chemical, water and labour with chemical|
|Expenses 3 year||-325500||325500||325500|
|Expenses 4 year||-325500||325500||325500|
|Expenses 5 year||-325500||325500||325500|
|Expenses after completion of 5th||-711660||1843900||1443900|
|You will save Rs 7 lacs approximately in 5 years with our system whereas with existing chemical dosing system, you will spend 25 lacs in 5 years. Absolute savings will be Rs 20 lacs approx. in 5 years|
|If you have 5 cooling towers of the same capacity or more, you will save approx. 1 cr. in 5 years. If our system is retrofitted to your existing cooling tower|
The above content is written based on no. of years of experience with the system.
Vikas S. Thakur