Our world today is progressing at a breakneck speed compared to a decade ago.
As such, we are faced with two possible futures, a clean and green future or one of climatic catastrophe. Scientists and environmentalists have warned us that we are headed in the wrong direction.
Facilities Management (FM) personnel, therefore, must do their part in changing the course towards a clean and energy efficient future.
Scale deposition is a challenge commonly encountered when processing aqueous solutions containing ions of sparingly soluble salts. Scale deposits can readily form on flow surfaces when a solution is concentrated beyond the solubility limit of a dissolved, sparingly soluble salt or when a solution containing an inverse solubility salt is in contact with a hot surface.
Many brackish water sources contain alkaline forming ions which tend to precipitate CaCO3 and Mg(OH)2. Controlling the scaling potential of water circulating in cooling towers using precipitation by electrolytic methods has long been recognised. But now, it can be enhanced with a modern control system and chemical-free approach.
Modern HVAC systems today, consume more than 60% of total power requirements in a building.
For large HVAC systems with capacity greater than 400 RT, cooling by water, which is more energy efficient, is recommended or mandated.
Enormous power consumption is also seen in industrial applications; e.g., food (fruits, vegetables, meat & seafood) processing and preservation in a chilled environment, data centers, chemical processes, etc.
An FM’s goal is to help reduce carbon emissions/carbon footprint through efficient Cooling Water Management in energy, water, and maintenance and chemical savings.
Water-Cooling Tower System
To ensure one’s water-cooling tower system is being properly maintained, we first have to understand how a water-cooling tower operates.
At Heat Exchanger
Cooled water in the basin is pumped through the heat exchanger. The water picks up heat and its temperature increases.
At Spray Nozzles
Warm water is distributed to spray nozzles at the top of the tower, raining warm water droplets over the fill media below.
At Fill Media
Fan on top of the tower draws in air through the fill media from below, accelerating the vaporisation and hence cooling of warm water. The cooled water drips down from the fill media back to the basin.
The cycle repeats, where cooled water is pumped through the heat exchanger and so on.
Blow-Down of Tower Water
Evaporated water leaves behind dissolved impurities from the makeup water, which will concentrate and cause scaling and corrosion.
Concentrated impurities in the water-cooling tower are removed through blowing down of tower water to the drain. The basin water level drops due to evaporation and blow-down losses. More makeup water is added to maintain the water level.
Potential Problems with Water-Cooling Tower System
Every newly commissioned water-cooling tower system is capable of operating within the system specifications. Over time, however, the system performance may deteriorate if not properly maintained.
In a worst-case scenario, the water used for cooling in the water-cooling tower system becomes an incubator for Legionella bacteria. In recent years, there have been cases of fatal Legionnaires’ disease outbreak in several major cities around the world.
The Eco-Sustainable Approach to Cooling Water Management
As mentioned above, cooling by evaporation equipment such as cooling towers will increase the solid concentration and result in scaling and corrosion.
Conventional Cooling Water Management methods use a non-eco friendly, 100% chemical approach to deal with these issues. However, scale deposits still build up over time in heat exchanger tubes, pipes and cooling towers and will require periodic chemical cleaning that commonly uses hazardous substances. These together with the blow-down, which will also contain chemicals, can pollute waterways when discharged.
On the flip side, a pseudo-scientific Non-Chemical Devices (NCD) approach will not yield satisfactory results.
The undesirable effects of this practice can now be circumvented using an environmentally-friendly system such as DeCaIon (DCI).
How DCI Works?
DeCaIon, as the name suggests, is a device that removes calcium (Ca) ions which would otherwise cause scale deposition. In addition, it also removes Mg ions and SiO2. DCI uses electrochemical energy to dissolve existing scale from pipes, cooling tower packing and heat exchanger/condenser unit, and continuously prevents further scale from forming during operation.
The scale removal principle of the electrochemical technique is based on the creation of a high pH environment around the cathode by water and oxygen reactions which release hydroxyl ions. The alkaline environment induces precipitation of the calcium hardness in the form of CaCO3 and of the magnesium hardness, in the form of Mg(OH)2.
It also removes Dissolved Oxygen in water. The Oxidation Reduction Potential (ORP) is therefore reduced. It ensures an alkaline cooling water of pH~8.5 and thus protects the tubes/pipes from oxidation and corrosion. One other notable feature of DCI System is its CataGreenTM component, which disinfects water, preventing bio fouling, algae, heterotrophic and Legionella bacteria growth. All these are achieved within a compact unit without any external chemical addition. In short, it is chemical free!
Amongst other reactions, the following takes place at the Anode and Cathode:
|Anodic Reactions||Cathodic Reactions|
|4HCO3– – 4e = O2 + 4CO2 + 2H2O||4Ca2+ + 4HCO3– + 4e = 4CaCO3 + 2H2|
|Resultant Products||Resultant Products|
|Oxygen and Carbon Dioxide are evolved. Some biocides are also produced.||Solid Calcium Carbonates (CaCO3) deposited on Cathode surface.|
Magnesium (Mg2+) hardness and Silica (SiO2) are also removed in the process.
DCI is a stand-alone piece of equipment. That is to say the connection does not disrupt any operation of the Water Cooling System. The pump is piped from the cooling tower and the outlet pipe is connected to the tower basin independently, as indicated in the flow schematic below:
Water from the cooling tower system is pumped into the DCI electrolyser chamber where the electrochemical reactions occur.
During this process, the drain valve is in ‘Closed’ position. The processed water from the electrolyser chamber is channelled back to the cooling tower basin. Over time, the entire cooling water volume is electrolysed. Periodically, the content in the chamber together with the scale precipitated is discharged and the electrodes regenerated. All these are done automatically.
Prior to commercialization, intensive R&D and tests were carried out in-house and by independent professional institutions. Upon successful testing, the device is now presented to the marketplace. The following are some findings of DCI’s performance.
A Semi-Conductor Company (The Philippines)
- Hardened scales are softened and dislodged from the cooling tower and chiller tubes
- Power Savings : 11.2%
- Water Savings : 50%
SIMTech A*STAR (Singapore)
Av Power before DCI = 52.6 kW Percent Saving = 17.4%
Av Power aft DCI @ eqm = 43.4 kW
The facilities management group, being a cost center, is compelled to look into all possible avenues to reduce both CAPEX and OPEX. Here are some benefits that DCI can provide:
✓ > 50% Water Savings
✓ 100% Chemical Savings
✓ ~7-20% Power Savings
✓ Stand-alone Installation
✓ Minimal maintenance
✓ Good Return of Investment
✓ Higher product yield resulted from efficient cooling
✓ Consistent high product quality due to efficient cooling
✓ Chemical free: Blow-down does not pollute waterways
✓ Compressor maintenance/replacement reduced
An electrochemical system coupled with a product such as CataGreen, provides a means for rapid, clean capture of water hardness, as well as disinfection, which is simple, easy to maintain and requires no chemical introduction or handling. This technology proves to be a valuable new tool, effectively allowing cooling water to be treated under a new strategy that not only improves chiller/condenser performance, but also significantly saves water, power and eliminates need for chemicals.
Innovative Polymers Pte Ltd is a Singapore-based company. Besides providing engineering plastic/polymer solutions, it also provides sustainable water treatment technology for cooling water management by DCI, which is a patented device by the company. This device has since gained recognition by Singapore Green Building Council (SGBC).
Innovative Polymers Pte Ltd
5, Yishun Industrial Street 1,
Unit 07-02, North Spring BIZHUB
Tel : +65 68440805