Air Cleaning Devices II

Air Cleaning Devices Industrial Ventilation PDC

Spring Carolinas Section Meeting

Asheville, NC

Jonathan F. Hale, MPA Air Systems Corporation

Dust Characteristics

Size

Shape

Bulk

Density

Abrasiveness Agglomerativeness

Fibrous

Hygroscopicity

Chemical

Composition Type

Filter Challenge

Particle Size,

Particle Shape,

Air-to-Media Ratio/Velocity,

Particle Concentration Grains/DSCF,

Hygroscopicity,

Abrasiveness,

Ease of Release,

Aglomeritiveness

Particle Size Chart

Fume

Mist

Clay

Smog

Virus

Carbon Black

Tobacco Smoke

Colloidal Silica Milled Flour

Coal Dust

Pollen

Fertilizer

Bacteria

Cement Dust

Human Hair

Mold Spores

Clouds/Fog

Lint

Beach Sand

Silt Fine Sand

Spray

Dust

(Log Scale)

Relative Size of

Typical Airborne

Particulates

Microns (µ) 0.001 0.01 0.1 1.0 10 100 1000

Technical

Definitions

Atmospheric

Conditions

Scanning Electron

Microscope

Optical

Microscope

Visible to

Naked Eye

Mist/Drizzle/Rain

Dust Cake

Bag filter with scrim Dust cake on Cartridge

Dust Shape

Dust generating process

Spherical, fibrous, or flaky

Abrasiveness

Tendency to rub or wear away the media or the collector

Detergents, Rice hulls, or steel shot

Maintain velocity <2,000 fpm

Agglomerativeness

Tendency to gather into a ball, mass, or cluster

Paper, cellulose, cotton

Special cartridge or bag

Controlled airstream conditions

Hygroscopicity

Readily taking up and retaining moisture

Acids, starches, or cement

Relates to releasability of dust cake

Settling Chambers

Centrifugal Cyclones

High Efficiency Cyclones

Multicyclones

Is BACT on PC boiler <100mmBTU/hr.

Hopper evacuation can give high efficiencies,

Many small cyclones with inlets and outlets grouped.

Air Stream Characteristics

Temp

Humidity

Chemistry

Condensables

Gaseous Contaminants

Fabric Dust Collectors

Cartridge Style Dust Collector

Advantages:

– higher efficiency on very small particles,

– Very compact,

– Large surface area,

– Ease of changeout- especially on toxics,

– Lower pressure drop

Reverse-air Cleaning Round Dust Collector

Built-in cyclone,

Only one discharge point up to 70,000 cfm,

No compressed air required.

Filter Medias

Polyester

Polypropylene

Acrylics

Ryton

Nomex

Micro-Fibers

P 84

PTFE

Fiberglass

Hybrids

Anti-static

Cellulose

PTFE Membranes

Microstructure

Small Pore Size

High Porosity

Bi-axial Structure

Chemically Inert

Hydrophobic

Renewable Coatings

Precoats

Continuous coatings

Continuous Coating

Protect the filter components

– Oils

– Condensables

– Acids

– Fires

Extend the filter life

Reduce emissions

React with contaminants

– Acids

– NOx

Broken Bag Detectors

Triboelectric and Tribokinetic Devices for the Detection of Particulate Emissions

Triboelectric?? Tribokinetic??

What’s the Difference??

Triboelectric Effect

Tribokinetic Effect

Regulatory Outlook

•EPA has published a Fabric Filter Bag Leak Detection Guidance document

•Guidance document mentions tribokinetic (AC-coupled) devices, but states

that there was insufficient data to include them in the guidance.

•The MACT standard for the secondary lead smelting industry references

triboelectric bag leak detection as an alternative to opacity monitoring.

•“Trade Show Talk” is that EPA is considering triboelectric devices, when

calibrated against a Method 5 stack test, for emissions monitoring.

Electrostatic Precipitation

ESP-Side View

Utility Precipitators

Dry Precipitator Issues

Bypass of pollutants around collection cells

Pollutant resistivity,

Material buildup on components/sparks jumping from corona wire to ground,

Improper or to infrequent cleaning.

Wet Electrostatic Precipitator

Good on sticky and gooey blue-haze particles.

Requires intrinsic wastewater treatment system

Bar-B-Que Smoke, Liberty, NC

Particulate- wood smoke

Particulate- sticky grease aerosols

Wet Absorption

Mass transfer process occurs through a phase boundary absorbing the molecule in the medium, then,

Utilize absorbent chemistry to neutralize or bind the offending pollutant,

Can be done sometimes with a simple spray chamber effectively,

Generally requires less than 5” pressure drop,

Generally uses 5-10 gpm per 1000 scfm.

Gaseous Wet Scrubber Issues

Temperature limitations of media, box, and fan,

Corrosion limitations of media, box and fan,

Solubility of final products or particulate,

Generally accepted principle:

Efficiency varies directly with the Energy input- Water energy (gpm/pressure) or air differential pressure.

Scrubber diagram

Acid Vapors, mists

Oil Mists,

Some Organics

Odors

No Particles!

Components for Scrubber System

Mist Eliminator/Scrubber Combo

Wet Fan-

Fan with spray,

Cyclonic wet precleaner,

Cyclonic demister.

High Energy Contactor

Saturated plume,

Venturi section,

Cyclonic demister,

10-100” pressure drop,

Ammonia Injection Grid

(AIG)

NH3 Supply Unit

NH3

from others

Accumulator Vaporizer NH3 Storage Tank

Ammonia

Flow Control

Unit

Mixing

Dilution Fan

Chamber

NH3

Injection

Control

Reactor

(Catalyst)

NOXNON 700

Typical Flow of SCR System

350MW

250MW 175MW

VOC Abatement

Very application specific,

Six major types of abatement technologies with much differences and advantages and disadvantages,

Remember to factor in ongoing operational costs!

Straight Thermal Oxidizer

Typically on :

halogenated hydrocarbons,

Higher BTU streams

Sticky-gooies or other particulate-laden hydrocarbons

Direct Thermal Oxidation

Recuperative Oxidizer

Recuperative Thermal Oxidizer

Regenerative Thermal Oxidation

98+% thermal oscillating heat recovery,

Heat recovery media inexpensive,

Can be made low NOx,

With Catalyst bed-RCO

RTO

VOC Concentrator

Used on higher volumes at low concentrations

Acts like carbon adsorption only uses thermally inert hydrophobic zeolites

Hydrophobic Zeolite Wheel

Adsorbs 99+% of most VOCs,

Structured “clay” molecular sieve,

Won’t burn like activated charcoal,

Biofiltration

Blue Haze Polluter-Asphalt Batcher

Dense Fiber-Bed Filter

Blue Haze Filter-Cut through

Notes:

1st quarter inch

Particulate on surface,

Droplets on trailing side.

Reactant Bed Media/DLA Use media that:

Reacts,

Absorbs,

Adsorbs,

Oxidizes,

Neutralizes

Free Air Pollution Controls!

Most states allow rapid amortization of APC systems-5 years or less,

Check for property tax ad velorem exemption.

Always Use the Proper Design

Please come attend!

•Free Barbeque!

•Free Ventilation Manual!

•Free Connie!