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

josmar@sc.usp.br

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

josmar@sc.usp.br

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