Particulate Control Devices

Question 1

ESP General Info

Answer 1

• Electrostatic precip
• Dust particles are charged and collected on collection plates due to elect potential
• Poor collection for PM5-PM1
• 95% of coal stations use ESP ( bag filters are emerging now)
• High collection eff, but sub microns particles escape
• Cleaned by shaking or water

Question 2

Types of ESP

Answer 2

• Plate/wire
• Tubular
• Flat plate
• WEt
• 2 stage

Question 3

types of particles charging

Answer 3

• Diffusion charging: occurs when other gas molecules charge other molecules (small particles)
• Field Charging - Charging from field (larger particles)

Question 4

Filter bag material types

Answer 4

Woven: Dust cake acts a filter medium
Needlefelted- used for pulse jet cleaning
Operates at higher gas to cloth ratio

Question 5

Design parameters for bag filters

Answer 5

Cleaning:

• Mechanical shake
• Reverse Cycle
• Pulse jet

Gas to cloth ratio: pressure drop and material cost

Efficiency: With DP and time

Question 6

Bag cleaning Details

Answer 6

Mechanical Shaking: Woven material, sequential (some bags at a time), gas enters inside bags, shaken dirt falls into hopper (4hz 30 sec, 2 min settling). 50-75mm amplitude

Reverse Flow - Made from fiberglass
Dirty gas insdie bags, use of sonic horn to clean, anti collapse ring. Similar gas to cloth ratio

Pulse Jet cleaning - Dirty gas from outside bags, bursts of compressed air inside to clean (opposite direction of dirty air) for fraction ofsecond

Question 7

Depth Filters

Answer 7

Use multi layers to capture debris

Target eff f(Ns)- particles collected on target filter/particles travelling in the line of target filter

Ns -Separation number