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WATER TREATMENT FOR COOLING SYSTEM

The quality of water used for the cooling system directly affects the efficiency, operation costs and reliability of all industrial cooling systems. Selection of water treatment equipment or solutions depends on: (i) the type of cooling system, (ii) the features of the feed-water, and (iii) the water quality to be achieved after treatment.

Water treatment for cooling system

1. Overview of cooling system

A device or system including many devices is used to reduce the temperature of a water stream by extracting heat from water and releasing it to the atmosphere. Currently, the cooling tower is applied to many different industries such as:

  • Electro-Refrigeration industry: Produce air conditioners, ice making,...
  • Seafood processing industry
  • Plastic industry: support plastic injection molding or plastic packaging.
  • Pharmaceutical industry: preserving medicines at the right temperature.
  • Metallurgical industry: cooling products from steel, aluminum ...
  • Electrical cable industry
  • Some other industries: electrical cables, alcohol production, wastewater treatment ...

1.1 Some popular cooling systems:

  • One-through system: The water used for this type of cooling tower is usually from abundant and cheap sources such as rivers, streams and low input water temperatures. Input water is often treated to prevent scale and microorganisms
  • Open recirculating system: This is perhaps the most popular cooling system in the industry. In accordance with this method, circulating water is lost due to evaporation and compensated continuously with an equivalent volume, therefore water quality constantly changes. In addition, due to the air flow through the tower, oxygen in the water is easily absorbed and have dusts. 
  • Closed circulating system: In this system, there is only little or no loss of water (it means water volume in the pipe never fluctuates). Inlet water (if any, there will be only a very small volume) to maintain the system to be full all the time. In addition, in this system, water always has pressure, so scale air can be removed through automatic ventilator

1.2 Important parameters of cooling water:

Important parameters of cooling water are: conductivity, total dissolved solids (TDS), hardness, pH, alkaline and saturation index.

  • Total conductivity and total dissolved solids (TDS): Conductivity is a measure of the conductivity of water and is correlated with the amount of dissolved solids (TDS) in water. Pure distilled water has very low conductivity (low mineral) and sea water will have high conductivity (high mineral). The presence of solids dissolve in water makes it easy to form insoluble mineral precipitates on the surface of heat transfer, often referred to as “scale”. Scale tries to stick to the surface, starts to impact the pipe system and affects heat transfer and water pressure.
  • Main purpose of almost circulating water system is minimization of scale formation. Conductivity can be considered as controlling value when TDS/conductivity is determined.
  • PH is a measure of acidity / basic of water. Measurement range 0-14, with 7 being neutral. Controlling pH is very important for almost cooling water treatment programs. In general, when the pH indicates acid environment, corrosion will increase and when the pH indicates an alkaline environment, scale formation capacity increases.
  • Hardness: The amount of calcium and magnesium dissolved in water determines its "hardness". Total hardness is divided into two types: carbonate hardness or temporary hardness and non-carbonate hardness or permanent hardness. Hardness, especially temporary hardness is the most common and is responsible for the sedimentation of calcium carbonate scale in the pipes and equipments.
  • Saturation index: Water saturation index or Langlier Saturation index (LSI) is a measure of the stability of water involved in scale formation. When LSI is positive, water tends to form scale, and when LSI is negative, water tends to erode. LSI from 0 to 1.0 is considered stable.
  • Because condenser has high temperature (40-42 ° C), Ca ++ and Mg ++ ions in hard water easily form hardened carbonate on the surface of heat exchanger, reduce the heat transfer coefficient, increase resistance force on pipes, which leading to reduce cooling system efficiency. At the cooling tower, warm water creates an conducive environment for the development of seaweed, algae, and toxins that contaminate and reduce the capacity of the cooling system.

2. Purpose of water treatment for cooling tower

  • Remove coarse trash which can clog cooling system such as vegetation, trash…
  • Remove suspended solids in water to prevent the form of scale which can adversely affect heat transfer efficiency and can cause corrosion. In addition, accumulation of much scale can clog the cooling system.
  • To remove excess carbon dioxide, remove the metals presenting in water such as iron, manganese.
  • Inhibits the growth of microorganisms on the surface of the heat exchanger
  • Eliminate the corrosion ability of the cooling tower due to dissolved oxygen in water, dissolved salts, alkalis or microorganisms.

2.1 Current solution method applied for cooling system:

In order to treat input water for the cooling system, avoid the risk of clogging pipes and devices due to scale and algae, there are some treatment solutions as follows:

  • Treat input water by water softening, alkali removal, ions exchange to remove minerals causing scale in feed-water;
  • Reduce PH: Scale forming capacity shall reduce in acid environment, which means pH concentration low;
  • Use Chemical - put the inhibitor of scale into circulating water;
  • Control the concentration process – It means to limit the concentration of the mineral that causes scale. This is done by bottom discharge, periodically or continuously. It means deliberately rinsing out part of the water to prevent minerals from conglomerating;
  • Physical treatment method – filtration, rust removal.

2.2 Water treatment by NGO-filtration equipment

In each solution, NGO always makes an effort NOT TO USE chemicals to avoid secondary pollution as well as minimize the operation cost for customers. The solution provided by NGO is highly accurate, ranging from raw filtration to refining, water re-use for producing high-quality products, water softening, anti-rust, corrosion or micro-organism removal by electrolytic method. This solution also effectively applied for water treatment of central air conditioning system and boiler system.

Result of CaCO3 removal from water by electrolytic method
Result of CaCO3 removal from water by electrolytic method

 

Various filtered solutions for the cooling system with different water qualities after treatment, depending on the characteristics of each factory
Various filtered solutions for the cooling system with different after-treated water qualities, depending on the characteristics of each factory

 

If your business is interested in solution to inlet water treatment, or has a demand for ion exchange materials, please contact NGO via phone number (024) 3566 8225 or email office@8ngo.com for direct consultation. 

Source: NGO