Comparison of different air treatment methods with plasma - PlasTEP

COMPARISON OF DIFFERENT
AIR TREATMENT METHODS
WITH PLASMA TREATMENT
PlasTEP 3 rd Summer school and trainings
course 2012 Vilnius / Kaunas
Saulius Vasarevicius, VGTU
Part-financed by the European Union (European Regional Development Fund
ˇ

Two Types of Air Pollutants
Particulate (Visible)
Gaseous

Stationary Source Control
• Philosophy of pollution prevention (3P’s)
– Modify the process: use different raw materials
– Modify the process: increase efficiency
– Recover and reuse: less waste = less pollution
• Philosophy of end-of-pipe treatment
– Collection of waste streams
– Add-on equipment at emission points
• Control of stationary sources
– Particulates
– Gases
3

Three Types Of Control
Mechanical
Chemical
Biological

Particulate Control
(Mechanical)
• Electrostatic precipitator
• Bag house fabric filter
• Wet scrubber
• High efficiency cyclones

Particulate Control Technologies
• Remember this order:
– Settling chambers
– Cyclones
– ESPs (electrostatic
precipitators)
– Spray towers
– Venturi scrubbers
– Baghouses (fabric filtration)
• All physical processes

Settling Chambers
• “Knock-out pots”
• Simplest, cheapest, no moving parts
• Least efficient
– large particles only
• Creates solid-waste stream
– Can be reused
• Picture on next slide
8

Disadvantages
• Large space requirement
• Relatively low overall collection
efficiencies (typical 20 - 60 %)
Gravity settler

Flue Gas Cleaning – The state of the art
Selection criteria
Emission
mg/Nm 3
ESP Bag house Scrubber Cyclones
(normal)
Spraycone
Cyclones
100 30 200 250 < 100
Reliability ++ + ++ ++++ ++++
Cost ++++ ++++ +++ + +

Gas Cleaning – The state of the art
Evaluation of ESP for industrial boilers:
• High cost (investment, maintenance & operation)
• Complex large size plant with sub-systems
• Requires constant gas conditions (sulphur, temp, moisture)
Evaluation of bag filters for industrial boilers:
• High cost (investment, maintenance & filter bags)
• Difficult to handle sulphur and sparks
• Not robust (one faulty bag destroys efficiency
Evaluation of wet scrubbers for industrial boilers:
• High cost (large water treatment plant)
• Difficult to separate fine particulate
• Sulphur control costly & difficult

Flue Gas Cleaning – The state of the art
Evaluation of cyclone “grid arrestor” :
• Low collection efficiency due to:
• Wrong design (see velocity analysis)
• Air ingress
• Bad manufacturing quality
• Lack of maintenance (blockage of cyclone cells)
But cyclone system advantages are low cost and robust installation
Can a cyclone reach efficiencies of ESP / Bag filter / Wet scrubber?
This question triggered our cyclone development Program
in 1994 to improve cyclone efficiency and to invent the
“dry spray agglomeration principle”

• Most Common
• Cheapest
Cyclone
• Most Adaptable

Mechanical Collectors –
Cyclones
Advantages: Good for larger PM
Disadvantages: Poor efficiency for finer PM
Difficult removing sticky or wet PM

Cyclone Operating Principle
“Dirty” Air Enters The Side.
The Air Swirls Around The
Cylinder And Velocity Is
Reduced.
Particulate Falls Out Of The Air
To The Bottom Cone And Out.

Flue Gas Cleaning – The state of the art
Commercial applications of high efficiency cyclones:
BurnerMax
Fluidized bed furnace
High efficiency cyclones
operating at 400 C

Multiple Cyclones
(Multi clone)
Smaller Particles Need Lower
Air Flow Rate To Separate.
Multiple Cyclones Allow
Lower Air Flow Rate, Capture
Particles to 2 microns

Air Filtration

Filtration Mechanisms
• Diffusion
Q: How does efficiency change with
respect to d p?
a. Efficiency goes up as d p decreases
b. Efficiency goes down as d p decreases

Filtration Mechanisms
• Impaction
Q: How does efficiency change
with respect to d p?
a. Efficiency goes up as d p decreases
b. Efficiency goes down as d p decreases

Fat Man’s Misery,
Mammoth Cave NP
Filtration Mechanisms
• Interception

Efficiency
Filter efficiency for individual mechanism
and combined mechanisms
1.0
0.8
0.6
0.4
0.2
Interception
Impaction
Diffusion
Gravitation
Total
0.0
0.01 0.1 1 10
dp (�m)

Fiber filter
FILTRATION
Q: Do filters function just as a strainer,
collecting particles larger than the strainer
spacing?
a: yes
b: no

Filter Drag Model
�� P �
�P
� �Pf
� �Pp
� s
� V K �LVt�V K1 � 2
Areal Dust Density W � LVt
Filter drag
P
S
V
�
� � S � K1
� K2s
W
e
K e & K s to be determined empirically
�P f: fabric pressure drop
�P f: particle layer pressure drop
�P s: structure pressure drop
Q: What is the pressure drop after 100 minutes of
operation? L = 5 g/m 3 and V = 0.9 m/min.
K e
K s
Time
(min)
�P, Pa
0 150
5 380
10 505
20 610
30 690
60 990

Case A: Pore blocking
Case B: Pore plugging
Case C1: Pore narrowing
Case C2: Pore narrowing w/lost pore
Case D: Pore bridging

• Impaction
• Diffusion
Air Filtration
• Straining (Interception)
• Electrostatics

Fabric Filter
(Baghouse)
• Same Principle As Home
Vacuum Cleaner
• Air Can Be Blown Through Or
Pulled Through
• Bag Material Varies According
To Exhaust Character

Cleaned gas
Dirty gas
Bags
Dust discharge
Baghouse Filter – only one to remove hazardous fine particles

Advantages/Disadvantages
• Very high collection efficiencies
• Pressure drop reasonably low (at beginning of operation,
must be cleaned periodically to reduce)
• Can’t handle high T flows or moist environments

Pulse-Air-Jet Type
Baghouse
35

Baghouse

About Baghouses
Efficiency Up To 97+%
(Cyclone Efficiency 70-90%)
Can Capture Smaller Particles
Than A Cyclone
More Complex, Cost More To
Maintain Than Cyclones

Types of Baghouses
• The three common types of baghouses
based on cleaning methods
a. Reverse-air
b. Shaker
c. Pulse-jet

Electrostatic Precipitators
Types include:
• Dry, negatively charged
• Wet-walled, negatively charged
• Two-stage, positively charged

• ELECTROSTATIC PRECIPITATOR
• Advantages of Electrostatic Precipitators
� Electrostatic precipitators are capable very high efficiency, generally of
the order of 99.5-99.9%.
� Since the electrostatic precipitators act on the particles and not on the air,
they can handle higher loads with lower pressure drops.
� They can operate at higher temperatures.
� The operating costs are generally low.
• Disadvantages of Electrostatic Precipitators
� The initial capital costs are high.
� Although they can be designed for a variety of operating conditions, they
are not very flexible to changes in the operating conditions, once
installed.
� Particulate with high resistivity may go uncollected.

http://www.ppcbio.com/ppcdespwhatis.htm

Electrostatic Precipitator Drawing

How An ESP Operates

ESPs
• Electrostatic precipitator
• More expensive to install,
• Electricity is major operating cost
• Higher particulate efficiency than
cyclones
• Can be dry or wet
• Plates cleaned by rapping
• Creates solid-waste stream
• Picture on next slide
44

Electrostatic Precipitator Concept
45

Electrostatic Precipitator
46

Cleaned gas
Dust discharge
Electrodes
Dirty gas
Electrostatic Precipitator – static plates collect particles

Wet Type
• Venturi
• Static packed
• Moving bed
• Tray tower
• Spray towers

Scrubbers
• Gas Contacts A Liquid Stream
• Particles Are Entrained In
The Liquid
• May Also Be A Chemical
Reaction
–Example: Limestone Slurry
With Coal Power Plant Flue Gas

Wet Particle Scrubbers
• Particulate control by impaction,
interception with water droplets
• Can clean both gas and particle
phases
• High operating costs, high
corrosion potential

• WET SCRUBBERS (CONTD.)
• Advantages of Wet Scrubbers
• Wet Scrubbers can handle incoming streams at high temperature, thus
removing the need for temperature control equipment.
� Wet scrubbers can handle high particle loading.
� Loading fluctuations do not affect the removal efficiency.
� They can handle explosive gases with little risk.
� Gas adsorption and dust collection are handled in one unit.
� Corrosive gases and dusts are neutralized.
• Disadvantages of Wet Scrubbers
� High potential for corrosive problems
� Effluent scrubbing liquid poses a water pollution problem.

Venturi Scrubber
Detail illustrates cloud atomization from highvelocity
gas stream shearing liquid at
throat
52

Vertical Venturi Scrubber

Packed Bed Scrubber

Dry Scrubber System
http://www.fkinc.com/dirctspraydry.htm#top

Tower Scrubber

Spray Towers
• Water or other liquid “washes out” PM
• Less expensive than ESP but more than
cyclone, still low pressure drop
• Variety of configurations
• Higher efficiency than cyclones
• Creates water pollution stream
• Can also absorb some gaseous
pollutants (SO 2)
58

Spray Tower
59

Gaseous Pollutant Control
•Absorption
•Adsorption
•Combustion

Control of Air Pollutants
Gaseous pollutants - Combustion
• 3 types of combustion systems commonly
utilised for pollution control
– direct flame,
– thermal, and
– catalytic incineration systems

Control of Air Pollutants
Gaseous pollutants - Adsorption
• physical adsorption to solid surfaces
• Reversible - adsorbate removed from the
adsorbent by increasing temp. or lowering
pressure
• widely used for solvent recovery in dry
cleaning, metal degreasing operations,
surface coating, and rayon, plastic, and
rubber processing

Control of Air Pollutants
Gaseous pollutants - Adsorption
• limited use in solving ambient air pollution
problems – with its main use involved in the
reduction of odour
• Adsorbents with large surface area to
volume ratio (activated carbon) preferred
agents for gaseous pollutant control
• Efficiencies to 99%

Carbon Adsorption
• Will do demonstration shortly
• Good for organics (VOCs)
• Both VOCs and carbon can be
recovered when carbon is
regenerated (steam stripping)
• Physical capture
– Adsorption
– Absorption
64

Adsorb
Absorb
66

Control of Air Pollutants
Gaseous pollutants - Absorption
• Scrubbers remove gases by chemical
absorption in a medium that may be a liquid
or a liquid-solid slurry
• water is the most commonly used scrubbing
medium
• Additives commonly employed to increase
chemical reactivity and absorption capacity

Pollutants Of Interest
• Volatile Organic Compounds
(VOC)
• Nitrogen Oxides (NOx)
• Sulfur Oxides (SOx)

Controlling Gaseous Pollutants: SO 2 &
NO x
• Modify Process (recall 3P’s)
– Switch to low-sulfur coals
– Desulfurize coal (washing, gasification)
• Increase efficiency
– Low-NO x burners
• Recover and Reuse (heat)
– staged combustion
– flue-gas recirculation
69

Scrubbers / Absorbers
• SO 2 removal: “FGD” (flue gas desulfurization)
– Lime/soda ash/citrate absorbing solutions
– Can create useable by-product OR solid waste
stream
• NO x removal—catalytic and non-catalytic
– Catalyst = facilitates chemical reaction
– Ammonia-absorbing solutions
– Process controls favored over this technology
• CO & CO 2 removal
• Some VOC removal
71

Flue Gas SOx Control
SOx Forms Sulfuric Acid With
Moisture In Air Producing
Acid Rain.
Remove From Flue Gas By
Chemical Reaction With
Limestone

Control Technologies for Nitrogen
• Preventive
– minimizing operating
temperature
– fuel switching
– low excess air
– flue gas recirculation
– lean combustion
– staged combustion
– low Nox burners
– secondary combustion
– water/steam injection
Oxides
• Post combustion
– selective catalytic reduction
– selective non-catalytic
reduction
– non-selective catalytic
reduction

Thermal Oxidizers
For VOC Control
Also Called Afterburners

Thermal Oxidation
• Chemical change = burn
– CO 2 and H 2O ideal end products of all processes
• Flares (for emergency purposes)
• Incinerators
– Direct
– Catalytic = improve reaction efficiency
– Recuperative: heat transfer between inlet /exit gas
– Regenerative: switching ceramic beds that hold
heat, release in air stream later to re-use heat
75

• Catalytic
Two Types Of Oxidizer
• Non-Catalytic

Thermal Oxidizer
(Non-Catalytic)

Catalytic Thermal Oxidizer

Biological Method
• Uses Naturally Occurring
Bacteria (Bugs) To Break
Down VOC
• “Bugs” Grow On Moist Media
And Dirty Gas Is Passed
Through. Bugs Digest The
VOC.
• Result Is CO2 And H2O

A Bio Filter For VOC Removal

Other Technologies
• High-temp ceramic filter
• Operates at T > 500 F (limit for
baghouses)

E-beam flue gas treatment process
(Prof. A.Chmielewski)

Pollutants removed by EB method
The method has been designed for simultaneous removal of:
• SO2
• NOx
• Cl, HF etc.
• Volatile Organic Hydrocarbons (VOC)
• Dioxins
• Mercury
• Others…

Electron beam effect on gas, primary radiolysis products:
• 4.43N2 -› 0.29N2* + 0.885N(2D) + 0.295N(2P) + 1.87N(4S) + 2.27N2+ +
0.69N+ + 2.96e-
• 5.377O2 -› 0.077O2* + 2.25O(1D) + 2.8O(3P) + 0.18O* + 2.07O2+ +
1.23O+ + 3.3e-
• 7.33H2O -› 0.51H2 + 0.46O(3P) + 4.25OH + 4.15H +1.99 H2O+ + 0.01H2+
+ 0.57OH+ + 0.67H+ + 0.06O+ + 3.3e-
• 7.54CO2 -› 4.72CO + 5.16O(3P) + 2.24CO2+ + 0.51CO+ + 0.07C+ +
0.21O+ + 3.03 e-

Electron beam effect on gas, secondary reactions:
• O(1D) + H2O͢͢͢͢ ͢͢͢͢͢͢͢͢͢͢͢͢
-› 2OH*
• N2+ + 2H2O -› H3O+ + OH*+ N2
• O(3P) + O2+ M -› O3+ M
• e-+ O2 + M -› O2-+ M
• H3O+ + O2- -› HO2*+ H2O
As a result of these primary and secondary reactions OH*,
HO2 *, O*radicals, O3and other oxidizing species are
formed, that can oxidize NO, SO2 and Hg.

Radiothermal:
SO2 removal pathways
• SO2 + OH* + M -› HSO3 + M
• HSO3 + O2 -› SO3 + HO2*
• SO3 + H2O -› H2SO4
• H2SO4 + 2NH3 -› (NH4)2SO4
Thermal:
• SO2 + 2NH3 -› (NH3)2SO2
• (NH3)2SO2 -› (NH4)2SO4

NO oxidation
NOx removal pathways
• NO + O(3P) + M -› NO2+ M
• O(3P) + O2+ M -› O3+ M
• NO + O3+ M -› NO2+ O2+ M
• NO + HO2* + M -› NO2+ OH* +M
• NO + OH* + M -› HNO2+M
• HNO2+ OH* -› NO2+ H2O
NO2removal
• NO2+ OH* + M -›HNO3+ M
• HNO3+ NH3-›NH4NO3

Reaction mechanisms and sequenceof E-beam process
H. Namba: Materials of UNDP(IAEA)RCA Regional Training Course on
Radiation Technology for Environmental Conservation TRCE-JAERI,
Takasaki,

VOC-decomposition and deodorization methods
Thermal Processes: 1-TO, Thermal Oxidation; 2-RTO, Regenerative Thermal Oxidation; 3-
Catalytic Oxidation with Recuperation. Filtering/Adsorption: 4-Biofilters; 5-Scrubber; 7-
Adsorption Container; 8-Concentrator Unit with TO; 9-Filtering. Non-thermal Oxidation: 6a-
Electrical Non-thermal oxidation; 6b-UVS Non-thermal Oxidation.

Non-thermal plasmas:
VOC-decomposition
• Decomposition of contaminants without heating
• Wide range of pollutants (Gases ... Particulate Matter PM)
• Decomposition of organic PM
• High efficiency for low contamination (e.g. deodorization), ([VOCs] < 1 g
Corg/m3)
Negative aspects:
• High energy cost/molecule_ high energy for high concentrations
• Uncompleted conversion and by-products _ low selectivity (CO2)
• Deposition of polymer films in reactors _ unstable plasma source
Possibilities - indirect treatment, hybrid methods = combination of plasma with:
catalysts, scrubbing, adsorbents…

VOC decomposition by O2 plasma

Aromatic VOC decomposition mechanism. Positive ions’
charget transfer reactions
• M++ RH = M + RH+
• Radical –neutral particles reactions
• OH radical reactions
• ˙OH + C6H5CH3= R1˙(OH radical addition)
• C6H5CH3+ ˙OH = R2˙ + H2O ( H atom abstraction)
• C6H6+ ˙OH = C6H5OH + H (H atom elimination)
• Organic radicals’ reactions
• R˙ + O2= RO2˙
• 2 RO2˙ = 2RO˙ + O2
• RO2˙ + NO = RO˙ + NO2
• RO˙ + O2= HO2˙ + products ( aromatic-CHO, -OH)
• RO˙ -› aliphatic products
R. Atkinson: Chem. Rev. 85(1985) 69

Non thermal plasma

PDC for deodorization (commercial)

CML 2001, Experts IKP (Central Europe)
1200
1000
800
600
400
200
0
By-products
Material resources
Electricity
74.4
1099.7
EBFGT WFGD + SCR
Total weighed environmental impact of plasma and non-plasma end-of-pipe
pollutant treatment technologies: the comparison of technologies for SOx/NOx
removal. 1) Electron Beam Flue Gas Treatment (EBFGT) versus 2) Wet Flue Gas
Desulphurization with Selective Catalytic Reduction (WFGD+SCR

CML 2001, Experts IKP (Central Europe)
50
40
30
20
10
0
By-products
Material resources
Electricity
4.2
Total weighed environmental impact of plasma and non-plasma end-of-pipe
pollutant treatment technologies: the comparison of technologies for VOCs
removal. 1) Dielectric barrier discharge (DBD) versus 2) adsorption by zeolite (for
LCA) and molecular sieves (for CBA), 3) biofiltration,
41.1
DBD plasma Adsorption
(zeolite rotor)
26.1
Biofilttration

Flue gas treatment method >300
MW unit
Investment costs
€/kW
Annual operation costs
€/MW
EBFGT 32-45 1290-1577
Wet deSO2 + SCR 176-247 4786-5350
Wet deSO2 + SNCR 144-190 3870-4223
Emission control method 120 MW
unit
Investment costs
€/kW
Annual operation costs
€/MW
EBFGT 113 5167
WFGT+SCR 162 5343
Investment and operation costs of EBFGT and combination of conventional deSO 2 and deNOx
Full “Report on Eco-Efficiency of Plasma-Based technologies for Environmental Protection” and
“Report on cost-benefit analysis of plasma-based technologies“ are available at the PlasTEP
project website (http://www.plastep.eu/fileadmin/dateien/Outputs/OP3-2.1_Ecoefficiency_report.pdf,
http://www.plastep.eu/fileadmin/datein/Outputs/120208_CBA.pdf).

Thank You for Your attention!