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Module 3

Module 3. Cyclones & Electrostatic Precipitators. What are we doing in class today?. Preliminaries VCD AVSEQ04.DAT cyclones AVSEQ03.DAT ESPs Cyclones, ESPs Examples. Review. Module 2 Educational Objectives. Size of particles that are most responsible for visibility reduction (p. 48)

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Module 3

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  1. Module 3 Cyclones&Electrostatic Precipitators

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

  3. 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. MCEN 4131/5131 LearningObjectivesfor 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)

  5. MCEN 4131/5131 LearningObjectives 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. MCEN 4131/5131 LearningObjectives 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 LearningObjectives 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 LearningObjectives 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. MCEN 4131/5131 LearningObjectives 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. MCEN 4131/5131 LearningObjectives 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 LearningObjectives 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)(1.4 + 2.5/2) = 6

  12. MCEN 4131/5131 LearningObjectives 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 3-4 - discuss articles, choose one to share with class.

  14. MCEN 4131/5131 LearningObjectives 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. MCEN 4131/5131 LearningObjectives 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. MCEN 4131/5131 Duct Air flow LearningObjectives 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

  17. MCEN 4131/5131 LearningObjectives 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 Duct Air flow Section 2 Section 1 LearningObjectives 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

  19. MCEN 4131/5131 LearningObjectives 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. MCEN 4131/5131 LearningObjectives 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

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