Module 3

Document Sample
Module 3 Powered By Docstoc
					       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
                                  the past decade
                                • 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