Weeks 4-6 Flashcards
How to improve dispersion?
-tall stack heights
- intermitten control schemes
Just write out what a mass balance is
Accumulation = input - output + net generation
Major Air pollutants for coal-fired plants
-Mercury (HG)
- Sulfur dioxide
- nitrogen oxides
- PM
- Trace metals
- VOCs
Catalyst for Air Pollution control
-often pellets and honeycomb
Define:
Aerodynamic Diameter
-defined as the diameter of a sphere with unit density that has the same settling velocity as the particle of interest
When does Diffusion occur?
occurs when small particles happen to diffuse toward the object while passing near it
What is the equation for the average horizontal gas velocity in the chamber mixed or flow
V = Q/WH
When does Inertial Impaction occur?
occurs when the center of the mass of a particle that is diverging from the fluid streamlines strikes a object
What are gravity settlers
a large chamber where contaminated gas passes slowly which allows the particles to settle out via gravity
also refered to as precleaners
What are some advantages of Gravity Settlers
-low capital cost
- low energy cost & operating cost
- little maintenance requirements
- dry collection and disposal
What are some disadvantages of Gravity Settlers
-low PM collection efficiecy (20-60%)
- doesn’t work with sticky materials
- large physical size
- trays in mult-tray settling chamber may wrap
Collection Efficiency Equation
(Have to memorize this)
n= (LgD^2P(part))/ (HVavg(18u))
Collection Efficiency Equation for mixed flow
= 1-exp(-n(blockflow)
What are some advantages of Centrifugal Separators
-low capital cost
- ability to penetrate at high temps
- ability to collect dry solids as dry materials and liquids as liquids
Equation for Diffusivity
D= (kTC)/ (3 pi u* D)
K = boltzman constant
c= cunningham correction factor
