Prevent freezing (Anti-Icing)
Anti-Icing operations are carried out with the aim of preventing water from freezing on roads and passages. In this method, before the onset of frost, with the help of meteorological information and by predicting the possibility of frost, antifreezing materials are spray on road surface.
Prevent ice from forming means lowering the freezing point before snow or rain by spraying materials on the road surface. In leading countries, the first priority in snow removal operations is preventing ice from forming. In this plan, based on the environmental conditions of each region and the use of appropriate chemical compounds, the freezing point temperature of the passages is lowered.
Thus, with early preventing ice forming, the opportunity to take the necessary precautionary and executive measures is provided.
In this method, in order to control financial costs, anti-Icing operations are carried out on the routes that play an important role in the flow of vehicles, such as the main highways or important bridges in the city, at a certain time before the rain and snow.
- Prevent the reduction of service level on the passages.
- Prevent blockage of drains.
- Reduction of antifreeze materials used.
- Reduction of accidents caused by frost.
- Reduction of environmental impact.
In this method, substances such as Calcium Chloride, Magnesium Chloride, Sodium Chloride, Urea and Potassium Chloride are used.
It is should be noted that urea is less used in cities and residential areas due to its environmental damage to humans; However, due to its non-corrosive properties, this material is used to prevent ice forming and reduce slippage in the runways of airports and metal structures. Other materials are used according to their advantages and disadvantages and in accordance with the environmental conditions of the region.
Deicing
Melting ice and deicing is the operation required to remove snow and ice layers created on the road surface. When the snow condenses to 25 mm or more and sticks to the road surface, defrosting begins. Usually both defrosting and antifreeze activities are done together and in combination.
Deicing methods:
- Chemicals and salt spraying
- Salt and sand
- snow removal by mechanical machines
In the calculation of defrosting costs, the costs of chemicals used, defrosting operations, collection and cleaning of materials from the road surface, compensation of environmental damages and damages on the road surface should be calculated.
Calcium Chloride
The effective composition of dissolved Calcium Chloride for ice melt is approximately 30% Calcium Chloride and 70% water by weight. Calcium Chloride as an industrial deicer is effective up to -32°C (-25°F). Calcium Chloride melts ice by releasing heat and acts faster than other common Chlorides. It removes moisture from the air even after the ice has melted, keeping the road surface moist.
Advantages of Calcium Chloride for Ice Melt (Deicing)
One of the advantages of Calcium Chloride for ice melt over other Chlorides such as Potassium Chloride, Urea, Rock Salt, Magnesium Chloride, is better performance at lower temperatures.
Calcium Chloride is effective at temperatures as low as -32 ° C. Magnesium Chloride is effective only at -18 degrees Celsius and other materials such as Rock Salt and Potassium Chloride are effective up to -7 and -3 degrees Celsius. The 14 degree difference indicates that Calcium Chloride can perform better at very low temperatures than other materials.
Due to lower freezing point than salt solutions, Cacl2 is less likely to freeze in storage tank, therefore it is more desirable to use it in very cold places.
Ice melting by releasing the temperature
While chemicals such as Potassium Chloride and Rock Salt, need to absorb ambient heat for deicing, Calcium Chloride and Magnesium Chloride release heat during ice melting.
The amount of heat released by CaCl2 is about 10 times more than Magnesium Chloride, which makes it perform better at very low temperatures.
The desire to combine and absorb moisture
Calcium chloride dissolves faster in water than other substances due to its tendency to combine and absorb ambient moisture. When the calcium chloride solution is formed faster, the ice melting process begins quickly. The speed of melting ice on sensitive and busy routes is very important. If the deicing operation is carried out quickly, the possibility of accidents, road closures and other damages will be reduced.
Disadvantages of Calcium Chloride for ice melt (deicing)
High cost: CaCl2 is ten times more expensive than sodium chloride.
Adding More Chloride: Each molecule of Magnesium Chloride and Calcium Chloride, adds twice more chloride to the environment than Sodium Chloride. In addition, Calcium Chloride is used (30%) more than Magnesium Chloride due to its higher concentration. As a result, more chloride enters the environment.
Corrosion: Calcium Chloride has more corrosive properties than other salts, so in order to overcome the corrosive properties, inhibitors must be added.
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2 Responses
Despite all the advantages of cacl2 for ice melt, why using rock salt is more common?
The main reasons are availability and lower price of rock salt . Other disadvantages as mentioned includes adding More Chloride and being corrosive