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Deicing of roadways and airplanes
Transcript of Deicing of roadways and airplanes
1942- New Hampshire was the first state to start using salt to clear roads
1970- Most of U.S. was using salt instead of sand
In recent years, the use of sodium chloride is accompanied by the use of other salts as well as organic compounds.
Aircraft deicing gained considerable momentum after various airplane crashes due to improper deicing methods.
1982- Air Florida flight out of Washington-National Airport ends in crash
2004- crash of Chinese Eastern Airlines plane traveling from Baotou, China to Shanghai. By: Hannah Bonitz and Alicia Remilard Deicing of Roads and Airplanes What is Deicing? Deicing is the removal of snow, ice, or frost from a surface. This can be accomplished by: Using dry or liquid chemicals that are designed to lower the freezing point of water Common Deicers! Sodium Chloride (NaCl)
Magnesium Chloride (MgCl ) 2 Calcium Chloride (CaCl ) 2 Potassium Chloride (KCl) Inorganic Salts Organic Compounds Calcium Magnesium Acetate
Urea And.... Alcohols, Diols, and Polyols Methanol
Glycerol Sodium Chloride Deicing of Roads!
Deicing of roads is traditionally done with sodium chloride (NaCl)
15 million tons of sodium chloride are dropped on U.S. roads each winter.
Sodium Chloride is typically used because it is inexpensive and readily available.
It is often combined with sand in order to provide traction for vehicles.
Recently, snow plows are beginning to spread other salts, such as calcium chloride and magnesium chloride. Aircraft Deicing
Aircraft deicing involves using deicing and anti-icing fluids composed mostly of ethylene and propylene glycol.
This is applied using booms or trucks with an operator bucket mounted to the boom.
Weather conditions dictate the necessary concentration of glycol in ADF.
Most operators use fluid with 50 percent glycol concentration by volume. Deicing and Anti-icing fluids
also contain additives... corrosion inhibitors
thickeners that protect aircraft surfaces There are 4 types of deicing/anti-icing fluids used for airplanes.........
Deicing: removal of snow, ice or frost from a surface.
Anti-icing: the application of chemicals that de-ice, but also remain on a surface and delay the reformation of ice for a certain period of time.
contain glycol and less than 1% additives
used most commonly for deicing and have short holdover times Type 2 Fluids... Type 3 Fluids Type 4 Fluids Type 1 Fluids... Used for anti-icing
have higher concentrations of additives (less than 2%) in addition to glycol Used for anti-icing
have higher concentrations of additives (less than 2%) in addition to glycol Higher concentrations of additives (less than 2%) in addition to glycol
Used for deicing and anti-icing Social Impact
The use of road salt and airplane deicing methods reduces the number of car accidents and plane crashes each year.
The 15 million tons of salt dumped on U.S. roads each year eventually washes away...
These runoff chemicals can negatively affect the environment in a given area. Effects on Wild Animals Effects on Plants Effects on Humans Effects on Pets Salt runoff that ends up in water bodies raises the salinity of local water and reduces dissolved oxygen levels. This makes the environment toxic for various species. Deicing salts such as calcium chloride leach into the soil and their ions accumulate, becoming toxic. The daily recommended sodium intake is 1,500 mg, but the average American gets 3,400 mg daily.
City water supplies can be contaminated by road salt. Pets can easily get rock salt stuck in their paws on walks. When untreated, these cuts can lead to infection. Effects of Deicing Methods on the Human Body Ethylene glycol can lead to:
neurological, cardiovascular, and gastrointestinal problems
Salt has a strong tendency to cause corrosion, which can lead to the rusting of steel in vehicles and the rebar in concrete bridges.
Corrosion is an oxidation reaction with atmospheric oxygen in the presence of water on the surface of a metal. It is accelerated by the presence of a salt.
Water conducts small amounts of current that travel through metal. Salt adds more ions to water, making it a better conductor, allowing more current to pass through, producing more oxygen and thus more rust. Organic Compounds Organic compounds such as potassium acetate and calcium magnesium acetate are being produced to reduce the environmental issues. What is the science behind deicing? Freezing Point Depression
When a solute is dissolved in a solvent, the freezing point of the solution is lower than that of the pure solvent.
This is because the vapor pressures of ice and liquid water are the same at 0 degrees Celsius, but when a solute is dissolved in the water, the water in the solution will have a vapor pressure lower than that of pure ice.
So, no ice will form, but the vapor pressure of the ice will decrease faster than that of the liquid water as the temperature decreases.
As the solution is cooled, the vapor pressures of the ice and liquid water will become equal over time, and this is the new lower freezing temperature of solution. The Equation:
If the solution is ideal (depends on solute concentration not nature of solute) :
TF = KF · b · i
TF, the freezing point depression, is defined as TF= (pure solvent) - TF (solution).
KF is the constant characteristic of a particular solvent (called molal freezing-point depression constant). For water, KF = 1.853 K·kg/mol.
B is the molality of solution (mol solute per kg of solvent).
i is the van 't Hoff factor (number of ion particles per individual molecule of solute, e.g. i = 2 for NaCl, 3 for BaCl2).
Freezing-point depression relies on the concentration of solute particles = colligative property Compounds like Sodium Chloride, Calcium Chloride, and Ethylene Glycol are thus used because they lower the freezing temperature of water, which prevents ice from forming in freezing weather.
Sodium Chloride reduces the freezing temperature of water to -18 Degrees Celsius.
Calcium Chloride and Magnesium Chloride lower the freezing temperature to a much lower temperature than does Sodium Chloride and produce an exothermic reaction = more effective Works Cited http://en.wikipedia.org/wiki/De-ice http://www.mnn.com/earth-matters/translating-uncle-sam/stories/de-icing-dilemma-do-streets-need-salt http://www.epa.gov/safewater/sourcewater/pubs/fs_swpp_deicingair.pdf http://onlinepubs.trb.org/onlinepubs/sr/sr235/017-030.pdf http://chemistry.about.com/cs/howthingswork/a/aa120703a.htm http://ardent.mit.edu/airports/ASP_exercises/2009%20reports/Aircraft%20Deicing%20Vasilyeva.pdf http://www.saltinstitute.org/Issues-in-focus/Road-salt/Road-salt-our-environment/Corrosion http://www.tutorvista.com/content/science/science-ii/metals-non-metals/corrosion-metals.php http://en.wikipedia.org/wiki/Freezing-point_depression