1. Cyclones & Electrostatic Precipitators
Module 3
Cyclones & Electrostatic Precipitators

2. What are we doing in class today?
MCEN 4131/5131
What are we doing in class today?
Preliminaries
VCD
AVSEQ04.DAT cyclones
AVSEQ03.DAT ESPs
Cyclones, ESPs
Examples

3. Module 2 Educational Objectives
MCEN 4131/5131
Review
Module 2 Educational Objectives
Size of particles that are most responsible for visibility reduction (p. 48)
Aerodynamic diameter (p. 102, 114)
Particle size distributions (p. 105)
Device removal efficiencies are a function of particle size (p. 106)
Terminal settling velocity (p. 3.20)
Difference between impaction, interception, diffusion (p. 116)
Particle penetration of a device (p. 118)

4. Module 3a Educational Objectives
MCEN 4131/5131
Learning Objectives for Today
Module 3a Educational Objectives
Estimating cyclone collection efficiency (equation 4.7, 4.8 p )
50% cut diameter dpc (equation 4.6 p. 129)
Designing a cyclone from start to finish (Example 4.5 p )
Estimating ESP collection efficiency using Deutsch equation (equation 5.7 p. 152)
Plate size and number, duct number, section number
Designing an ESP from start to finish (p )

5. Cyclones Particulate control by centrifugal separation
MCEN 4131/5131
Learning Objectives
Cyclones
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
Particulate control by centrifugal separation
Inexpensive, no moving parts, operates at high T
Ideal as pre-cleaners for more expensive devices
Usually low efficiency collectors, high efficiency cyclone developed within the past decade
High pressure drop

6. Clicker Question (group)
MCEN 4131/5131
Learning Objectives
Clicker Question (group)
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
If the gas airflow rate is increased in a cyclone, what will happen to the efficiency?
Increase
Decrease
Stay the same

7. MCEN 4131/5131
Learning Objectives
Cyclones
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
Efficiency as a function of particle size depends on 50% cut diameter (dpc)
50% cut diameter depends on:
Number of revolutions
Gas inlet velocity
Particle density
Width of inlet

8. MCEN 4131/5131
Learning Objectives
Clicker Question
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
The 50% cut diameter is linearly related to the inlet velocity
True
False

9. Design Procedure Choose body diameter Calculate dpc
MCEN 4131/5131
Learning Objectives
Design Procedure
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
Choose body diameter
Calculate dpc
Calculate efficiency (eq. 4.7, 4.8)
If efficiency too low, choose smaller diameter and go back to step 2
If efficiency is OK, check pressure drop (eq. 4.12)
If pressure drop too high, choose different cyclone type or split flow into 2 parallel cyclones (this lowers flow and thus pressure drop)

10. Clicker Question (extra credit)
MCEN 4131/5131
Learning Objectives
Clicker Question (extra credit)
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
For cyclones in series, the 2nd cyclone has a _____ efficiency compared to the 1st one.
Lower
higher

11. MCEN 4131/5131
Learning Objectives
Sample Problem 1
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
Estimate the number of revolutions in a Swift high efficiency cyclone
Use column (2)of Table 4.1
D/D = 1, H/D = 0.44, Lb/D = 1.4, Lc/d = 2.5
Ne = (1/0.44)( /2) = 6

12. MCEN 4131/5131
Learning Objectives
Sample Problem 2
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
The Swift cyclone from previous problem will be used to collect particles with s.g. of 2. Estimate cut diameter for previous Swift cyclone with inlet width = 0.5 ft, inlet velocity = 60 ft/sec
Given an aerosol with 2% of mass at 0.5 mm, 10% of mass at 5 mm, and 88% of mass at 10 mm, estimate % mass collected by this cyclone
What is the pressure drop? Is it acceptable? If not, what would you do?

13. Time for NEWSPAPER Articles!
Groups of discuss articles, choose one to share with class.

14. Electrostatic Precipitators
MCEN 4131/5131
Learning Objectives
Electrostatic Precipitators
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
Particulate control by electrical attraction
Ionization of contaminated air flowing between electrodes, particles charge, migrate and collect
High collection efficiency
Dry or wet collection, range of T
low pressure drop
High capital costs

15. Collection Efficiency
MCEN 4131/5131
Learning Objectives
Collection Efficiency
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
Use Deutsch Equation to estimate
Clicker Question: According to the Deutsch equation, the ESP collection efficiency depends on
Volumetric flow rate, electrostatic force
plate area, particle charge
Drift velocity, plate area

16. ESP Plates Plates are usually taller than they are long
MCEN 4131/5131
Learning Objectives
ESP Plates
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
Plates are usually taller than they are long
Placed in parallel
Tall
Gas flows through space between plates
Called ducts
Interior plates collect particles on both sides, end plates only collect particles on one side
Air flow
Duct

17. Clicker Question (group)
MCEN 4131/5131
Learning Objectives
Clicker Question (group)
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
Given a total plate area of 6520 m2, calculate the number of plates required assuming the plates are 6 m high and 3 m long and that there are 2 sections in the direction of flow.
181 plates
183.1 plates
184 plates
362 plates

18. MCEN 4131/5131
Learning Objectives
Ducts and Sections
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
Number of ducts = number of plates through which air flows minus 1
Sections refers to the number of plates that are all on one electrical circuit and is between 2 and 8
Air flow
Duct
Section 1
Section 2

19. ESP Design Mostly an ART Use Table 5.1 as guideline
MCEN 4131/5131
Learning Objectives
ESP Design
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
Mostly an ART
Use Table 5.1 as guideline
Select plate spacing, gas velocity, aspect ratio, plate height
Calculate # of ducts in direction of flow
Calculate # of plates in a section
Calculate # of electrical sections
Estimate total collection area
Estimate collection efficiency using Deutsch equation
Iterate!

20. Clicker Question (Group)
MCEN 4131/5131
Learning Objectives
Clicker Question (Group)
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
What industry uses 80% of all ESPs?
Oil refineries
Coal-fired power plants
Automotive industry