Cyclones & Electrostatic Precipitators Module 3 Cyclones & Electrostatic Precipitators

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

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)

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. 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)

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

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

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

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

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)

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

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)(1.4 + 2.5/2) = 6

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?

Time for NEWSPAPER Articles! Groups of 3-4 - discuss articles, choose one to share with class.

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

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

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

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

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

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!

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