CETESB - ENVIRONMENT AGENCY OF SAO PAULO STATE
REGIONAL CENTER OF STOCKHOLM CONVENTION ON PERSISTENT ORGANIC POLLUTANTS (POPs)
FOR THE LATIN AMERICAN AND CARIBBEAN REGION
V INTERNATIONAL PROGRAM FOR INTENSIVE TRAINING IN ENVIRONMENTAL MANAGEMENT OF CHEMICALS AND THEIR WASTE, ESPECIALLY PERSISTENT
ORGANIC POLLUTANTS (POPs) AND MERCURY (Hg)
Dioxin, Furan and Mercury Control TechnologiesPhD Ing.Ligia Cristina Gonçalves de Siqueira
January 2016
São Paulo - SP - Brazil
CHARACTERISTICS OF PCDD/Fs
PCDD/F :• Particulate matter and gases• Semi-volatile• Lipophilic • Hydrophobic • Not very soluble in water• Soluble in nonpolar solvents• High boiling point• Limited biodegradation
COLLECTION, CONTROL AND VENTILATION SYSTEMS
• Measures that will reduce human exposure toparticulate matter:– Total– < 10 μm (PM10)– < 2.5 μm (PM2.5).
• Also reduce associated contaminants, such as:– Metals and metallic compounds (e.g. lead)– Gaseous contaminants (such as volatile organic
compounds).
COLLECTION, CONTROL AND VENTILATION SYSTEMS
MANAGEMENT OF COMBUSTION GASES
MANAGEMENT OF FLUE GASES AND OTHER RESIDUES
COLLECTION OF PCDD/F IN PARTICULATE MATTER FORM
• PCDD/F: released with flue gases in the gas phaseas well as particle bound
• Fine particle fraction: can be collected by controlequipment:
– Cyclones– Electrostatic precipitators– Fabric filters– Scrubbers
• To reduce emissions of particulate matter andassociated pollutants.
CYCLONE
•Remove the particulatematter from the gas flowby centrifugal force.
•Less effective than otherdevices, such aselectrostatic precipitatorsor fabric filters.
•For the control of coarseparticulate matteremissions.
•Not used alone inadvanced applications ofcombustion gas cleaning.
MULTICYCLONES(consisting of several small cyclones)
ELECTROSTATIC PRECIPITATORS• Called electrostatic filters• Use: for collecting and controlling emissions of fine
particulate matter in combustion gases.• Collection efficiency: resistivity of the particles• Efficient elimination of particulate matter, including
PCDD/F adsorbed in the particles.
ELECTROSTATIC PRECIPITATORSMechanism:- Application of an electric field to the gas flow tocharge the particles electrically.- Collection plates with opposite electrical chargeattract and collect the particles.
ELECTROSTATIC PRECIPITATORS
• Disadvantage:• PCDD/F can be formed: temperatures between 200°C
and 450°C.• Inlet temperature of precipitator: increases from 200°C
to 300°C with increase in PCDD/F concentrations.• Above 300°C: concentrations reduce.• Preferable operation temperatures: 160 to 260°C.• Avoid: operation > 250°C to reduce risk of PCDD/F
formation.
WET PRECIPITATORS •Wet electrostatic precipitators:•Use liquids (such as water) on collection plates towash pollutants off.•Operate best for cooler or moist gases.
WET PRECIPITATORS
Klauss Essen (online)
•Condensation electrostatic precipitators:•Plastic tubes arranged in bundles•Water-cooled externally by facilitating condensationwith water quench.•Collect finel iquids and solids.
FABRIC FILTERS
•Also known as bag filters orbag houses.
•Efficient control systems forfine particulate matter.
•Elimination of PCDD/Fassociated to particles andany vapors that may beadsorbed in particles of thegas stream.
ARTCOM - Industrial Exhaustion
FABRIC FILTERS• Bags: 16 to 20 cm diameter and 10 m long• Shape: envelopes, cartridges or bags• Arrangement: normally in series
FABRIC FILTERS
• Subject to damage with water (moisture) orcorrosion (gas stream).
• Gases: above dew point (130 °C - 140 °C) to preventthese effects.
FABRIC FILTERS• Materials:
– E.g. fiberglass or polytetrafluoroethylene (PTFE)– Some are more resistant to damage– Others are sensitive to acids– Can be used in combination with spray drying
adsorption systems for upstream removal of acid gases .• Temperature:
– Fabric is sensitive to temperature– Cyclones and spray dryers: used to cool inlet gases.– No cooling: damage to bags and PCDD/F can be formed,
as in electrostatic precipitators due operationtemperature.
CHARACTERISTICS OF FABRIC FILTERS
Material Maximum temperature
(°C)
Resistance
Acid Alkalis Physical flexibility
Cotton 80 Poor Good Very good
Polypropylene 95 Excellent Excellent Very good
Wool 100 Normal Poor Very good
Polyester 135 Good Good Very good
Nylon 205 Poorto average
Excellent Excellent
PTFE 235 Excellent Excellent Normal
Polyamide 260 Good Good Very good
Fiberglass 260 Average to Good
Average to Good
Average
European Commission (2005)
COMPARISON BETWEEN PARTICULATE MATTER ELIMINATION SYSTEMS
SYSTEM Concentrations of particulate
matterAdvantages Disadvantages
CYCLONE AND MULTICYCLONE
Cyclones: 200-300 mg/Nm3
Multicyclones: 100-150 mg/Nm3
- Powerful, sensitive, reliable- Used in incineration (pre-collector)
- Pre-collector- High energy consumption
ELECTROSTATIC PRECIPITATOR (DRY)
< 5 - 25 mg/Nm3- Little power- Temperature of gases: 150-350°C
-Formation of PCDD/F at 200-450°C
ELECTROSTATIC PRECIPITATOR (WET)
< 5 - 20 mg/Nm3- Reaches low concentrations
- With pre-collector- Liquid effluents- Plume visibility
BAG FILTER < 5 mg/Nm3 - Particulate layer acts as additional filter and adsorption reactor
- High energy consumption- Condensation and corrosion
European Commission (2005)
SCRUBBERS
• For reduction ofparticulate matteremissions with liquid(water)• Can also removegaseous pollutants (acidgases and mercury).• Must be supplied withdemister.•Help to reduce formationof PCDD/F.
SCRUBBERS
• Equipped with pneumatic jets(water and compressed air).
• Collect PCDD/F-covered fineparticles with spraying of theabsorption solution and thehigh speed of the waterdroplets.
• Gas cooling: condensation andimprovement of adsorption ofVOCs on the particles.
• Efficiency: 90%• Emission: 0.2 - 0.4 ng TEQ/Nm3
COLLECTION OF GAS EMISSIONS
– Post-combustion chambers– Quench (rapid cooling systems)– Scrubbing processes (dry and wet)– Adsorption processes– Catalytic processes
POST-COMBUSTION CHAMBERS•Independent devices or integrated into main combustion chamber•Disposal of unburned or partially burned carbon compounds•A catalyst, additional combustion air or a burner with auxiliary fuel(such as natural gas) may be required•Legislation: can specify the minimum disposal temperatures for aspecific process.•Practice: values should be defined in burning tests.
Type of waste Post‐combustion temperature (°C)
Residence time (secs)
Legislation
Industrial and agrotoxic ≥1200 ≥2
NBR 11075/90CONAMA 316/02
Crematoriums, municipal and health‐care
≥800 ≥1 CONAMA 316/02
QUENCH (RAPID COOLING SYSTEMS)
• Use of water.• Rapid reduction in temperature of combustion
gases to prevent reformation of PCDD/F (<100°Cin 5 secs).
• Practice:• This system can not worked, because it is very
difficult to reach the temperature range.• It can been replaced by other alternatives, such as
adsorption in coal + fabric filter for reduction ofparticulate matter and PCDD/F emissions.
SPRAY DRY SCRUBBING/ADSORPTION
•Also known as spray drying or semi-wet scrubbing.•Application:elimination of acid gases and particulatematter from post-combustion gases.
•Injection of atomized lime solution (lime slurry) intothe reactor at a controlled velocity.
•Water in lime: is mixed with combustion gases,neutralizing acid gases, and evaporates.
•Temperature of gases: decrease and helps to reduceformation of PCDD/F.
•Particulate matter: collected in fabric filters orelectrostatic precipitators
DRY WASHING FOR SPRAYING
European Commission (2005)
DRY WASHING FOR SPRAYING
• Efficiency:• Acid gases: ~ 90% (e.g. HCl and SO2).• Waste incineration plants: 93% SO2 and 98% HCl.• Practice:• It has replaced the rapid cooling system (quench) after the
gas post-combustion chamber.• Helps to prevent the formation of PCDD/F due to reduction
in temperature and collection of particulate matter.• Waste generated: should be sorted and disposal in
landfills.
WET SCRUBBERS
• Technologies: jet, rotation, Venturi, spray, dry towerand packed tower scrubbers
• Effective for elimination of soluble acid gases.• Reduce formation and emission of PCDD/F (vapor
and particles).• Efficiency: depends on the solubility of the
contaminant with the liquid (pH, solubility, etc.)• Solid particles in scrubber water: when in contact
with the PCDD/PCDF of the gas flow reducesefficiency.
WET SCRUBBERS• Two Stages Scrubber:• Stage 1: elimination of HCl by adding water• Stage 2: elimination of SO2 by adding lime solution.
In this process, gypsum may be generated, whichreduces the amount of waste for landfills.
WET SCRUBBERS
•Packed tower: polypropylenewith addition of carbon can beused to eliminate PCDD/F.•Memory effect: accumulation ofvarious PCDD/PCDF congenersin plastic materials used (severalhours or long-term).•Best practice: eliminate PCDD/Fbefore wet scrubbing to reduceresidual effect.
Tower with packing
ADSORPTION WITH ACTIVATED CARBON•Reduction of following emissions:–Mercury–Volatile organic compounds–Sulfur dioxide (SO2)–Hydrochloric acid (HCl)–Hydrofluoric acid (HF)–PCDD/F
http://www.naturaltec.com.br/Carvao-Ativado.html
ADSORPTION PROCESSES• Temperature : 110°C to 150°C• Gases: pass through an adsorbent material bed
(activated carbon).• Activated carbon bed: remove particulate matter,
aerosols and residual gases• Flow: crosscurrent and countercurrent (prevent
blockage of the bed with residual dust).• Inorganic pollutants: collected in particles and
removed previously.• Efficiency: 99.9%.• Emission: 0.1 ng TEQ/Nm3
ADSORPTION PROCESSES
FLOW INJECTION PROCESSES• Injection of adsorbents for capturing PCDD/F from gas flow• Particulate collected in fabric filter.• Adsorbents: activated carbon or coke with lime hydrate.• Operating temperatures: 135°C to 200°C.• Filtering efficiency: 99%.• Depends upon:
– Quality of adsorbent injection– Mixture of combustion gases and adsorbent– Type of particle filter– Operation system– Mass flow of the adsorbent
• Maximum efficiency: use of bag filter.• Emission: 0.1 ng TEQ/Nm3
FLOW INJECTION PROCESSES
ENTRAINED FLOW REACTOR
• Adsorbent injection process• Adsorbents: mixture with hydrated lime or other
inert materials (limestone or sodium bicarbonate).• Gases: previously removal of the fly ash (bulk
material) and acid gases.• Particulate collected in bag filters.• Operating temperature: 110°C to 150°C.• Emission: 0.1 ng TEQ/Nm3
ENTRAINED FLOW REACTOR
DRY ADSORPTION (RESINS)
•Known as Adiox TM System.•Combines adsorption and absorption of PCDD/Fs in plasticstructures that contain dispersed activated carbon particles.
•PCDD/F: it is absorbed into the polymer matrix and diffuses acrossthe surface of carbon particles, where they are irreversibly absorbed.
•Adiox TM: most common application in absorption towers•Application: incinerators (gas flows 5.000 - 100.000Nm3/h)•Reduction of PCDD/F•Reduce the memory effect of packing towers•Dry adsorbers: higher efficiency•Efficiency: depends on the quantity of material installed.
DRY ADSORPTION (RESINS)
CATALYTIC PROCESSES• Used for reducing NOx emissions: catalytic
reduction can also help to reduce PCDD/F.• Elimination of PCDD/F + NOx: injection of a
air-ammonia mix of in the gas flow that passesthrough a catalyst.
• Before catalytic reduction: remove theparticulate matter (< 5 mg/m3) because:– Reduce the use of the catalyst– Prevent deactivation of the catalyst (poisons)
HIGH TEMPERATURE SELECTIVE CATALYTIC REDUCTION REACTOR FOR NOx AND PCDD/F
Hartenstein (2003)
CATALYTIC OXIDATION OF PCDD/PCDF
• To eliminate PCDD/PCDF only (DeDioxprocess):– no ammonia injection– operating temperatures: 130°C to 350°C.
• Advantage: Easy of operation• Disadvantage: Waste (spent catalyst)
CATALYTIC OXIDATION OF PCDD/PCDF
•Catalytic oxidation: only eliminates PCDD/F in gas phase.•Emission reduction: 95% to 99%.•Depends upon:–Volume of catalyst–Reaction temperature–Speed of combustion gases through catalyst.•PCDD/F Emission: < 0.01 ngTEQ/Nm3 (dry base, 11% O2).•Selective catalytic reaction: can also oxidize mercury, whichis soluble and can be eliminated by gas desulfurizing systems
CATALYTIC BAG FILTERS• Bags with PTFE membrane impregnated with
catalyst.• Can be used in the incineration of waste,
crematoriums, metallurgic plants and cement plants.
CATALYTIC BAG FILTERS• Filter bags: impregnated with catalyst or powdered
catalyst mixed into the fibre structure (PTFE).• PCDD/F can be destroyed on the catalyst rather than be
adsorbed by the activated carbon, and discharged assolid waste.
• Bag filters: operate at temperatures between 180°C and250°C.
• Application:• Concentrations of particulate matter: 1 – 2 mg/Nm3.• Crematoriums in Germany and Japan: < 0.1 ng
TEQ/Nm3
CATALYTIC BAG FILTERS
CATALYTIC CERAMIC BAG FILTERS• Material: catalytic silicate ceramic fiber • Prevent risks of explosion and burning of bags• Temperature: up to 1.000ºC. • Resistant to temperature steps (from 850 °C to 100 °C in less than 5 seconds)• Resistant to acid gases (SOx, NOx).• Chemical stability• Resists hydrolysis and chemical oxidation (exception: HF, H3PO4 and concentrated
alkalies)• Effective for PCDD/F.
http://www.meiofiltrante.com.br/materias_ver.asp?action=detalhe&id=626&revista=n46
Before use Catalytic silicate ceramic fiber 38,000 hours of use
CATALYTIC CERAMIC BAG FILTERS
http://www.meiofiltrante.com.br/materias_ver.asp?action=detalhe&id=626&revista=n46
COMPARISON OF PCDD/PCDF CONTROL SYSTEMS
Control equipment Elimination efficiency
Co - Benefits
Cyclone Low - Coarse dust removalElectrostatic precipitator Low -Designed for dust removalBag filter Medium - Designed for dust removalWet scrubber Medium - Designed for dust and/or acid
gases removalQuenching andsubsequent high-efficiency wet scrubber
Mediumto high
- Simultaneous reduction ofdust, aerosols, HCI, HF, heavymetals and SO2
Afterburner High - No residues- Quenching of flue gas required
COMPARISON OF PCDD/PCDF CONTROL SYSTEMSControl equipment Elimination
efficiency Co - Benefits
Catalytic oxidation (selectivecatalitic reation)
High(destruction ofPCDD/F + other
organics)
- No residues-Simultaneous reduction of NOx
Catalytic bag filter High - Simultaneous dust removal
Dry absorption in resins (carbonparticles dispersed in polymermatrix)
Depends on theamount of
installed material
- Selective for PCDD/F- Material can be incinerated afteruse
Entrained flow reactor withadded activated carbon orcoke/lime or limestone solutionsand subsequent fabric filter
Medium to high
- Simultaneous reduction ofvarious pollutants, such asPCDD/F and Mercury- Material can be incinerated afteruse (a)
Fixed bed or circulatingfluidized bed reactor, adsorptionwith activated carbon or open-hearth coke
High
- Simultaneous reduction ofvarious pollutants, such asPCDD/F and Mercury- Material can be incinerated afteruse (a)
(a) Mercury: need to eliminate mercury if the coal is incinerated for disposal.
REDUCTION OF COSTS IN PCDD/PCDF CONTROL SYSTEMS
- Use of existing facilities for PCDD/F control- Reduction of other contaminants (metals, aerosols,organic materials)
Devices Changes /Advantages Additional costs
Fabric filter or electrostatic precipitator
- Injection of activated carbon- Reactor for
- Storage, transport, handling and disposalof activated carbon- Waste generation
Catalytic oxidation of NOx
- Extension of catalyst surface with one or two layers- Reduction of PCDD/F (<0.1 ngTEQ/Nm3)
- Additional layers
REFERENCES • CETESB. Technologias de controle da poluição do ar para material
particulado, gases, vapores e odores and verificação de sistemas.2015.
• UNEP. Guidelines on best available techniques and provisionalguidance on better environmental practices under article 5 andannex C of the Stockholm Convention on Persistent OrganicContaminants (POC). 2008.
• UNEP. Stockholm Convention on Persistent Organic Contaminants(POC). 2001.
• Images: Internet