# Module 3

Document Sample

```					       Module 3

Cyclones
&
Electrostatic Precipitators
MCEN 4131/5131

What are we doing in class
today?
• Preliminaries
• VCD
– AVSEQ04.DAT cyclones
– AVSEQ03.DAT ESPs
• Cyclones, ESPs
• Examples

2
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)

3
MCEN 4131/5131
Learning
Objectives
for Today         Module 3a Educational
Objectives
• Estimating cyclone collection efficiency
(equation 4.7, 4.8 p. 129-130)
• 50% cut diameter dpc (equation 4.6 p. 129)
• Designing a cyclone from start to finish
(Example 4.5 p. 138-139)
• 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.
160-161)

4
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
50% cut diameter
Cyclone design
Cyclones
ESP collection ef f iciency
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
• High pressure drop
5
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
50% cut diameter
Cyclone design
Clicker Question (group)
ESP collection ef f iciency
Plate size & number
Duct & section number
ESP design
•   If the gas airflow rate is increased in
a cyclone, what will happen to the
efficiency?
a. Increase
b. Decrease
c. Stay the same

6
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
50% cut diameter
Cyclone design
Cyclones
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

7
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
50% cut diameter
Cyclone design
Clicker Question
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
•   The 50% cut diameter is linearly
related to the inlet velocity
a. True
b. False

8
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
50% cut diameter
Cyclone design
Design Procedure
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
1. Choose body diameter
2. Calculate dpc
3. Calculate efficiency (eq. 4.7, 4.8)
4. If efficiency too low, choose smaller
diameter and go back to step 2
5. If efficiency is OK, check pressure
drop (eq. 4.12)
6. If pressure drop too high, choose
different cyclone type or split flow
into 2 parallel cyclones (this lowers
flow and thus pressure drop)            9
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
Clicker Question (extra
50% cut diameter
Cyclone design
ESP collection efficiency
Plate size & number
credit)
Duct & section number
ESP design
1. For cyclones in series, the 2nd
cyclone has a _____ efficiency
compared to the 1st one.
a. Lower
b. higher

10
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
50% cut diameter
Cyclone design
Sample Problem 1
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)(1.4 + 2.5/2) = 6

11
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
50% cut diameter
Cyclone design
Sample Problem 2
ESP collection efficiency

• The Swift cyclone from previous
Plate size & number
Duct & section number
ESP design

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
12
do?
Time for NEWSPAPER
Articles!
Groups of 3-4 - discuss articles,
choose one to share with class.
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
50% cut diameter
Cyclone design
Electrostatic Precipitators
ESP collection efficiency
Plate size & number
Duct & section number

• Particulate control by electrical
ESP design

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

14
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
50% cut diameter
Cyclone design
Collection Efficiency
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
a. Volumetric flow rate, electrostatic force
b. plate area, particle charge
c. Drift velocity, plate area

15
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP Plates
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
Duct

Air flow

16
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
50% cut diameter
Cyclone design
Clicker Question (group)
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.
a.   181 plates
b.   183.1 plates
c.   184 plates
d.   362 plates

17
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
50% cut diameter
Cyclone design
Ducts and Sections
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
Duct

Air flow

Section   Section
18
1         2
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
50% cut diameter
Cyclone design
ESP 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!

19
MCEN 4131/5131
Learning
Objectives
Cyclone collection efficiency
50% cut diameter
Cyclone design
Clicker Question (Group)
ESP collection efficiency
Plate size & number
Duct & section number
ESP design
•   What industry uses 80% of all
ESPs?
a. Oil refineries
b. Coal-fired power plants
c. Automotive industry

20

```
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
 views: 5 posted: 12/13/2011 language: Latin pages: 20