1 / 39

AIR STRIPPING

AIR STRIPPING. The removal of volatile contaminants from water and contaminated soils. Air Stripping Tower Use. Air Stripping Towers. Some column internals. Clockwise from top left: Packing, bubble caps, mist eliminator, sieve tray. Case Study: TCE Contaminated Site Remediation.

scraft
Télécharger la présentation

AIR STRIPPING

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. AIR STRIPPING The removal of volatile contaminants from water and contaminated soils

  2. Air Stripping Tower Use

  3. Air Stripping Towers

  4. Some column internals Clockwise from top left: Packing, bubble caps, mist eliminator, sieve tray

  5. Case Study: TCE Contaminated Site Remediation

  6. Henry’s Law Henry's Law states that the amount of a gas that dissolves into a liquid is proportional to the partial pressure that gas exerts on the surface of the liquid. In equation form, that is: • where, • CA = concentration of A, [mol/L] or [mg/L] • KH = equilibrium constant (Henry's Law constant), [mol/L-atm] or [mg/L-atm] • pA = partial pressure of A, [atm] See also http://en.wikipedia.org/wiki/Henry's_law

  7. Example: Solubility of O2 in Water Although the atmosphere we breathe is comprised of approximately 20.9 percent oxygen, oxygen is only slightly soluble in water. In addition, the solubility decreases as the temperature increases. Thus, oxygen availability to aquatic life decreases during the summer months when the biological processes which consume oxygen are most active. Summer water temperatures of 25 to 30°C are typical for many surface waters in the U.S. Henry's Law constant for oxygen in water is 61.2 mg/L-atm at 5°C and 40.2 mg/L-atm at 25°C. What is the solubility of oxygen at 5°C and at 25°C?

  8. Solution O2 Solubility Example At 50C the solubility is: At 250C the solubility is:

  9. Air Stripping Example An air stripping tower, similar to that shown, is to be used to remove dissolved carbon dioxide gas from a groundwater supply. If the tower lowers the level to twice the equilibrium concentration, what amount of dissolved gas will remain in the water after treatment? The partial pressure of carbon dioxide in the atmosphere is 10-3.7 atm. Example 4.2 from Ray

  10. Solution Air Stripping Example Henry's Law constant for carbon dioxide = 1.14L/L Divide by RT, i.e. 1.14/(0.083x288) = 0.048 =10-1.3 mol L-1atm-1 The equilibrium solubility is then: Answer = 0.9 mg/L CO2

  11. Two-film partitioning in gas-liquid ys* Bulk liquid Cs* Bulk liquid Bulk gas ys Cb Cs Cb yb yb ys Cs Bulk gas ys* Cs* Absorption Stripping

  12. Mass transfer calculations Henry’s law applies because of equilibrium at interface: ys = HCs Fick’s law applies: flux is proportional to the driving force JA = kL(Cb – Cs) – kg(ys – yb)

  13. Relationship of transfer coefficients Another approach is that all the resistance to transfer is in the liquid phase, so yb= HC*s Alternatively all the resistance to transfer could be in the gas phase, so ys* = HCb Mass flux based on water phase, substitutions, and applying Henry’s law to liquid concentrations leads to 1/KLa= 1/kLa + 1/Hkga Similarly1/KGa= H/kLa + 1/kga

More Related