![[logo] US EPA](http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}
Characteristics of Particles - Collection Mechanisms - Answers
-
#1
- Based on Equation 2, what is the relationship between the rate of Brownian diffusion and particle size?
-
- Answer: Equation 2 indicates that the rate of this collection mechanism is inversely proportional to the particle size. Very small particles diffuse rapidly. Large particles have negligible Brownian diffusion rates.
-
#2
-
A small and a larger particle pass through a strong electrical
field. Which particle is more strongly affected by electrostatic
attraction and migrates faster toward a collection plate?
-
- Answer: Large particles have greater surface areas than small particles, allowing them to hold more charged gas ions and have a higher electrical charge than small particles. Accordingly, larger particles are influenced more strongly by the electrical field and migrate more quickly to particle collection surfaces.
-
#3
-
Can you think of any ways to improve the collection efficiency
of particles in the difficult-to-collect range of 0.1 to 0.5
micrometers?
-
- Answer: Stationary sources that generate large fractions of their total particulate matter in the 0.1 to 0.5 micrometer range may need to modify the process to alter the particle size distribution or to use a pretreatment system to "grow" the particles to a more easily collected size range.