# Presentation: 039434

## Control Device Technology

- Barrett Parker, EPA, OAQPS

## 4 VOC control techniques plus capture discussion
5 PM control techniques
2 Acid gas control techniques
3 NOx control techniques

- 4 VOC control techniques plus capture discussion
- 5 PM control techniques
- 2 Acid gas control techniques
- 3 NOx control techniques

## General description
Gas molecules stick to the surface of a solid
Activated carbon often used as it 
Has a strong attraction for organics
Has a large capacity for adsorption (many pores)
Is cheap
Silica gel, activated alumina, and zeolites are also used 

- General description
- Gas molecules stick to the surface of a solid
- Activated carbon often used as it
- Has a strong attraction for organics
- Has a large capacity for adsorption (many pores)
- Is cheap
- Silica gel, activated alumina, and zeolites are also used

## General description (continued)
3 types – fixed bed (most common), moving bed, and fluidized bed
Typically appear in pairs – one adsorbing while other desorbs
Used for control as well as recovery
Regenerated via steam, hot gas, or vacuum
Work best if molecular weight of compound between 50 and 200

- General description (continued)
- 3 types – fixed bed (most common), moving bed, and fluidized bed
- Typically appear in pairs – one adsorbing while other desorbs
- Used for control as well as recovery
- Regenerated via steam, hot gas, or vacuum
- Work best if molecular weight of compound between 50 and 200

## VOC Control Techniques – Carbon Adsorber – Fixed Bed Schematic

## VOC Control Techniques – Carbon Adsorber – Fixed Bed Examples

## Factors affecting efficiency
Presence, polarity, and concentration of specific compounds
Flow rate
Temperature
Relative humidity

- Factors affecting efficiency
- Presence, polarity, and concentration of specific compounds
- Flow rate
- Temperature
- Relative humidity

## Performance indicators
Outlet VOC concentration
Regeneration cycle timing or bed replacement frequency
Total regeneration stream flow or vacuum profile during regeneration cycle
Carbon bed activity 
Bed operating and regeneration temperature

- Performance indicators
- Outlet VOC concentration
- Regeneration cycle timing or bed replacement frequency
- Total regeneration stream flow or vacuum profile during regeneration cycle
- Carbon bed activity
- Bed operating and regeneration temperature

## Performance indicators (continued)
Inlet gas temperature
Gas flow rate
Inlet VOC concentration
Pressure differential
Inlet gas moisture content
Leaks 

- Performance indicators (continued)
- Inlet gas temperature
- Gas flow rate
- Inlet VOC concentration
- Pressure differential
- Inlet gas moisture content
- Leaks

## VOC Control Techniques – Carbon Adsorber – Manufacturer’s Specs

## General description
Waste gas gets oxidized to water and carbon dioxide 
Catalyst causes reaction to occur faster and at lower temperatures
Saves auxiliary fuel

- General description
- Waste gas gets oxidized to water and carbon dioxide
- Catalyst causes reaction to occur faster and at lower temperatures
- Saves auxiliary fuel

## General description (continued)
Catalysts allow lower operation temperatures (~ 650 to 1000°F)
Catalyst bed generally lasts from 2 to 5 years
Thermal aging, poisoning, and masking are concerns
Excess air is added to assist combustion
Residence time and mixing are fixed during design
Only temperature and oxygen can be controlled after construction 

- General description (continued)
- Catalysts allow lower operation temperatures (~ 650 to 1000°F)
- Catalyst bed generally lasts from 2 to 5 years
- Thermal aging, poisoning, and masking are concerns
- Excess air is added to assist combustion
- Residence time and mixing are fixed during design
- Only temperature and oxygen can be controlled after construction

## VOC Control Techniques – Catalytic Oxidizer – Example Bricks

## VOC Control Techniques – Catalytic Oxidizer - Schematic

## Factors affecting efficiency
Pollutant concentration
Flow rate
Operating temperature
Excess air
Waste stream contaminants
Metals, sulfur, halogens, plastics

- Factors affecting efficiency
- Pollutant concentration
- Flow rate
- Operating temperature
- Excess air
- Waste stream contaminants
- Metals, sulfur, halogens, plastics

## Performance Indicators
Outlet VOC concentration
Catalyst bed inlet temperature
Catalyst activity
Outlet CO concentration
Temperature rise across catalyst bed
Exhaust gas flow rate

- Performance Indicators
- Outlet VOC concentration
- Catalyst bed inlet temperature
- Catalyst activity
- Outlet CO concentration
- Temperature rise across catalyst bed
- Exhaust gas flow rate

## Performance Indicators (continued)
Catalyst bed outlet temperature
Fan current
Outlet O2 or CO2 concentration
Pressure differential across catalyst bed

- Performance Indicators (continued)
- Catalyst bed outlet temperature
- Fan current
- Outlet O2 or CO2 concentration
- Pressure differential across catalyst bed

## General description 
Gas or vapor turns to liquid via
Lowering temperature or
Increasing pressure
Used as pretreatment to reduce volumes
Used to collect and reuse some solvents

- General description
- Gas or vapor turns to liquid via
- Lowering temperature or
- Increasing pressure
- Used as pretreatment to reduce volumes
- Used to collect and reuse some solvents

## General description (continued)
Two types – contact and surface condensers
No secondary pollutants from surface type
More coolant needed for contact type
Chilled water, brines, and CFCs used as coolants
Efficiencies range from 50 to 95 percent

- General description (continued)
- Two types – contact and surface condensers
- No secondary pollutants from surface type
- More coolant needed for contact type
- Chilled water, brines, and CFCs used as coolants
- Efficiencies range from 50 to 95 percent

## VOC Control Techniques – Condenser - Schematic

## Factors affecting efficiency
Pollutant dew point
Condenser operating pressure
Gas and coolant flow rates
Tube plugging or fouling

- Factors affecting efficiency
- Pollutant dew point
- Condenser operating pressure
- Gas and coolant flow rates
- Tube plugging or fouling

## Performance indicators
Outlet VOC concentration
Outlet gas temperature
Coolant inlet temperature
Coolant outlet temperature
Exhaust gas flow rate
Pressure differential across condenser

- Performance indicators
- Outlet VOC concentration
- Outlet gas temperature
- Coolant inlet temperature
- Coolant outlet temperature
- Exhaust gas flow rate
- Pressure differential across condenser

## Performance indicators (continued)
Coolant flow rate
Pressure differential across coolant refrigeration system
Condensate collection rate
Inspection for fouling or corrosion

- Performance indicators (continued)
- Coolant flow rate
- Pressure differential across coolant refrigeration system
- Condensate collection rate
- Inspection for fouling or corrosion

## General description
Waste gas turns to carbon dioxide and water
Operating temperatures between 800 and 2000°F
Good combustion requires 
Adequate temperature
Turbulent mixing of waste gas with oxygen
Sufficient time for reactions to occur
Enough oxygen to completely combust waste gas

- General description
- Waste gas turns to carbon dioxide and water
- Operating temperatures between 800 and 2000°F
- Good combustion requires
- Adequate temperature
- Turbulent mixing of waste gas with oxygen
- Sufficient time for reactions to occur
- Enough oxygen to completely combust waste gas

## General description (continued)
Only temperature and oxygen concentration can be controlled after construction
Waste gas has to be heated to autoignition temperature
Typically requires auxiliary fuel
Common design relies on 0.2 to 2 seconds residence time, 2 to 3 length to diameter ratio, and gas velocity of 10 to 50 feet per second

- General description (continued)
- Only temperature and oxygen concentration can be controlled after construction
- Waste gas has to be heated to autoignition temperature
- Typically requires auxiliary fuel
- Common design relies on 0.2 to 2 seconds residence time, 2 to 3 length to diameter ratio, and gas velocity of 10 to 50 feet per second

## VOC Control Techniques – Thermal Oxidizer - Schematic

## Factors affecting efficiency
Waste gas flow rate
Waste gas composition and concentration
Waste gas temperature
Amount of excess air

- Factors affecting efficiency
- Waste gas flow rate
- Waste gas composition and concentration
- Waste gas temperature
- Amount of excess air

## Performance indicators
Outlet VOC concentration
Outlet combustion temperature
Outlet CO concentration
Exhaust gas flow rate
Fan current
Outlet O2 or CO2 concentration
Inspections

- Performance indicators
- Outlet VOC concentration
- Outlet combustion temperature
- Outlet CO concentration
- Exhaust gas flow rate
- Fan current
- Outlet O2 or CO2 concentration
- Inspections

## General description
Total efficiency is product of capture and control device efficiencies
Two types of systems
Enclosures and local exhausts (hoods)
Two types of enclosures
Permanent total (M204) – 100% capture efficiency
Nontotal or partial – must measure capture efficiency

- General description
- Total efficiency is product of capture and control device efficiencies
- Two types of systems
- Enclosures and local exhausts (hoods)
- Two types of enclosures
- Permanent total (M204) – 100% capture efficiency
- Nontotal or partial – must measure capture efficiency

## VOC Control Techniques – Capture System - Schematic

## Factors affecting efficiency
System integrity
System flow

- Factors affecting efficiency
- System integrity
- System flow

## Performance indicators
Enclosures
Face velocity
Differential pressure
Average face velocity and daily inspections
Exhaust Ventilation
Face velocity
Exhaust flow rate in duct near hood
Hood static pressure

- Performance indicators
- Enclosures
- Face velocity
- Differential pressure
- Average face velocity and daily inspections
- Exhaust Ventilation
- Face velocity
- Exhaust flow rate in duct near hood
- Hood static pressure

## General description
Particles hit wall sides and fall out
Often used as precleaners
Especially effective for particles larger than 20 microns
Inexpensive to build and operate
Can be combined in series or parallel

- General description
- Particles hit wall sides and fall out
- Often used as precleaners
- Especially effective for particles larger than 20 microns
- Inexpensive to build and operate
- Can be combined in series or parallel

## PM Control Techniques – Cyclone - Schematic

## Factors affecting efficiency
Component erosion
Inlet and outlet plugging
Acid gas corrosion
Air inleakage

- Factors affecting efficiency
- Component erosion
- Inlet and outlet plugging
- Acid gas corrosion
- Air inleakage

## Performance indicators
Opacity
Inlet velocity or inlet gas flow rate
Pressure differential
Inlet temperature

- Performance indicators
- Opacity
- Inlet velocity or inlet gas flow rate
- Pressure differential
- Inlet temperature

## General Description
Charged particles are attracted to plates and removed from exhaust gas
Two types
Dry type use mechanical action to clean plates
Wet type use water to prequench and to rinse plates
High voltages are required
Multiple sections (fields) may be used
Efficiencies up to 99% can be obtained

- General Description
- Charged particles are attracted to plates and removed from exhaust gas
- Two types
- Dry type use mechanical action to clean plates
- Wet type use water to prequench and to rinse plates
- High voltages are required
- Multiple sections (fields) may be used
- Efficiencies up to 99% can be obtained

## PM Control Techniques – Electrostatic Precipitator - Schematic

## PM Control Techniques – Electrostatic Precipitator - Schematic

## Factors affecting efficiency
Gas temperature, humidity, flow rate
Particle resistivity
Fly ash composition
Plate length
Surface area

- Factors affecting efficiency
- Gas temperature, humidity, flow rate
- Particle resistivity
- Fly ash composition
- Plate length
- Surface area

## Performance indicators
Outlet PM concentration
Opacity
Secondary corona power (current and voltage)
Spark rate
Primary power (current and voltage)

- Performance indicators
- Outlet PM concentration
- Opacity
- Secondary corona power (current and voltage)
- Spark rate
- Primary power (current and voltage)

## Performance indicators (continued)
Inlet gas temperature
Gas flow rate
Rapper operation
Fields in operation
Inlet water flow rate (wet type)
Flush water solids content (wet type)

- Performance indicators (continued)
- Inlet gas temperature
- Gas flow rate
- Rapper operation
- Fields in operation
- Inlet water flow rate (wet type)
- Flush water solids content (wet type)

## General description
Charged particles are deposited on pea gravel
Three parts
Ionizer system
Filter bed
Gravel cleaning and recirculation system

- General description
- Charged particles are deposited on pea gravel
- Three parts
- Ionizer system
- Filter bed
- Gravel cleaning and recirculation system

## PM Control Techniques – Electrified Filter Bed - Schematic

## Factors affecting efficiency
Glaze build up on ionizer or gravel
Temperature
Performance indicators
Ionizer voltage and current
Filter bed voltage, current, and temperature
Inlet gas temperature

- Factors affecting efficiency
- Glaze build up on ionizer or gravel
- Temperature
- Performance indicators
- Ionizer voltage and current
- Filter bed voltage, current, and temperature
- Inlet gas temperature

## Performance indicators (continued)
Pressure differential
Gas flow rate
Outlet PM concentration
Opacity

- Performance indicators (continued)
- Pressure differential
- Gas flow rate
- Outlet PM concentration
- Opacity

## General description
Particles trapped on filter media, then removed
Either interior or exterior filtration systems
Up to 99.9% efficiency
4 types of cleaning systems
Shaker (off-line)
Reverse air (low pressure, long time, off line)
Pulse jet (60 to 120 psi air, on line)
Sonic horn (150 to 550 Hz @ 120 to 140 dB, on line)

- General description
- Particles trapped on filter media, then removed
- Either interior or exterior filtration systems
- Up to 99.9% efficiency
- 4 types of cleaning systems
- Shaker (off-line)
- Reverse air (low pressure, long time, off line)
- Pulse jet (60 to 120 psi air, on line)
- Sonic horn (150 to 550 Hz @ 120 to 140 dB, on line)

## PM Control Techniques – Fabric Filter - Schematic

## Factors affecting efficiency
Filter media
Abrasion
High temperature
Chemical attack
Gas flow
Broken or worn bags
Blinding

- Factors affecting efficiency
- Filter media
- Abrasion
- High temperature
- Chemical attack
- Gas flow
- Broken or worn bags
- Blinding

## Factors affecting efficiency (continued)
Cleaning system failure
Leaks
Re-entrainment
Damper or discharge equipment malfunction
Corrosion

- Factors affecting efficiency (continued)
- Cleaning system failure
- Leaks
- Re-entrainment
- Damper or discharge equipment malfunction
- Corrosion

## Performance indicators
Outlet PM concentration
Bag leak detectors
Outlet opacity
Pressure differential
Inlet temperature
Temperature differential

- Performance indicators
- Outlet PM concentration
- Bag leak detectors
- Outlet opacity
- Pressure differential
- Inlet temperature
- Temperature differential

## Performance indicators (continued)
Exhaust gas flow rate
Cleaning mechanism operation
Fan current
Inspections and maintenance

- Performance indicators (continued)
- Exhaust gas flow rate
- Cleaning mechanism operation
- Fan current
- Inspections and maintenance

## General description
Particles (and gases) get trapped in liquids
Inertial impaction and diffusion
Liquids must contact pollutants and dirty liquids must be removed from exhaust gas
Four types 
Spray; venturi or orifice; spray rotors; and moving bed or packed towers

- General description
- Particles (and gases) get trapped in liquids
- Inertial impaction and diffusion
- Liquids must contact pollutants and dirty liquids must be removed from exhaust gas
- Four types
- Spray; venturi or orifice; spray rotors; and moving bed or packed towers

## PM Control Techniques – Wet Scrubber - Schematic

## Factors affecting efficiency
Gas and liquid flow rate
Condensation of aerosols
Poor liquid distribution
High dissolved solids content in liquid
Nozzle erosion or pluggage
Re-entrainment
Scaling

- Factors affecting efficiency
- Gas and liquid flow rate
- Condensation of aerosols
- Poor liquid distribution
- High dissolved solids content in liquid
- Nozzle erosion or pluggage
- Re-entrainment
- Scaling

## Performance indicators
Pressure differential
Liquid flow rate
Gas flow rate
Scrubber outlet gas temperature
Makeup / blowdown rates
Scrubber liquid solids content (PM)

- Performance indicators
- Pressure differential
- Liquid flow rate
- Gas flow rate
- Scrubber outlet gas temperature
- Makeup / blowdown rates
- Scrubber liquid solids content (PM)

## Performance indicators (continued)
Scrubber inlet gas and process exhaust gas temperature (PM)
Scrubber liquid outlet concentration (Acid gas)
Scrubber liquid pH (Acid gas)
Neutralizing chemical feed rate (Acid gas)
Scrubber liquid specific gravity (Acid gas)

- Performance indicators (continued)
- Scrubber inlet gas and process exhaust gas temperature (PM)
- Scrubber liquid outlet concentration (Acid gas)
- Scrubber liquid pH (Acid gas)
- Neutralizing chemical feed rate (Acid gas)
- Scrubber liquid specific gravity (Acid gas)

## General description
Sorbent reacts with gas to form salts that are removed in a PM control device (fabric filter)
Hydrated lime and sodium bicarbonate often used as sorbents

- General description
- Sorbent reacts with gas to form salts that are removed in a PM control device (fabric filter)
- Hydrated lime and sodium bicarbonate often used as sorbents

## Acid Gas Control Techniques – Dry Injection - Schematic

## Factors affecting efficiency
Dry sorbent injection rate
Emission stream gas temperature
Residence or reaction time
Degree of turbulence
Other PM control device used factors

- Factors affecting efficiency
- Dry sorbent injection rate
- Emission stream gas temperature
- Residence or reaction time
- Degree of turbulence
- Other PM control device used factors

## Performance indicators
Outlet acid gas concentration
Sorbent feed rate
Fabric filter inlet temperature
Sorbent carrier gas flow rate
Sorbent / carrier gas nozzle pressure differential
Sorbent specifications

- Performance indicators
- Outlet acid gas concentration
- Sorbent feed rate
- Fabric filter inlet temperature
- Sorbent carrier gas flow rate
- Sorbent / carrier gas nozzle pressure differential
- Sorbent specifications

## Performance indicators (continued)
Inlet gas / process exhaust temperatures
Exhaust gas flow rate
Other PM control device used indicators

- Performance indicators (continued)
- Inlet gas / process exhaust temperatures
- Exhaust gas flow rate
- Other PM control device used indicators

## General description
Alkali sorbent slurry turns acid gas into PM that is collected by a control device
Slurry is usually lime and water

- General description
- Alkali sorbent slurry turns acid gas into PM that is collected by a control device
- Slurry is usually lime and water

## Acid Gas Control Techniques – Spray Dryer - Schematic

## Factors affecting efficiency
Slurry feed rate
Residence or reaction time
Emission stream gas temperature
Slurry reactor outlet temperature
Slurry droplet size
Other PM control device used factors

- Factors affecting efficiency
- Slurry feed rate
- Residence or reaction time
- Emission stream gas temperature
- Slurry reactor outlet temperature
- Slurry droplet size
- Other PM control device used factors

## Performance indicators
Outlet acid gas concentration
Alkali feed rate to slurry mix tank
Water feed rate to slurry mix tank
Slurry feed rate and droplet size
Spray dryer inlet gas / process exhaust temperature
Other PM control device indicators

- Performance indicators
- Outlet acid gas concentration
- Alkali feed rate to slurry mix tank
- Water feed rate to slurry mix tank
- Slurry feed rate and droplet size
- Spray dryer inlet gas / process exhaust temperature
- Other PM control device indicators

## General description
Ammonia or urea is injected into exhaust streams with plenty of oxygen to reduce nitrogen oxide to nitrogen and oxygen
Efficiency ranges from 70 to 90 percent
Catalysts made from base and precious metals and zeolites
Operating temperatures range from 600 to 1100°F

- General description
- Ammonia or urea is injected into exhaust streams with plenty of oxygen to reduce nitrogen oxide to nitrogen and oxygen
- Efficiency ranges from 70 to 90 percent
- Catalysts made from base and precious metals and zeolites
- Operating temperatures range from 600 to 1100°F

## NOx Control Techniques – Selective Catalytic Reduction - Schematic

## Factors affecting efficiency
Catalyst activity
Masking or poisoning
Space velocity (gas flow rate divided by bed volume)
Excess ammonia or urea slip

- Factors affecting efficiency
- Catalyst activity
- Masking or poisoning
- Space velocity (gas flow rate divided by bed volume)
- Excess ammonia or urea slip

## Performance indicators
Outlet nitrogen oxide concentration
Ammonia / urea injection rate
Catalyst bed inlet temperature
Catalyst activity
Outlet ammonia / urea concentration
Catalyst bed outlet temperature

- Performance indicators
- Outlet nitrogen oxide concentration
- Ammonia / urea injection rate
- Catalyst bed inlet temperature
- Catalyst activity
- Outlet ammonia / urea concentration
- Catalyst bed outlet temperature

## Performance indicators (continued)
Inlet gas flow rate
Fuel sulfur content
Pressure differential across catalyst bed

- Performance indicators (continued)
- Inlet gas flow rate
- Fuel sulfur content
- Pressure differential across catalyst bed

## General description
Low oxygen exhaust gas transforms via catalytic reaction to water, carbon dioxide, and nitrogen
Catalysts made from noble metals
Efficiency ranges from 80 to 90 percent
Operating temperatures range from 700 to 1500°F

- General description
- Low oxygen exhaust gas transforms via catalytic reaction to water, carbon dioxide, and nitrogen
- Catalysts made from noble metals
- Efficiency ranges from 80 to 90 percent
- Operating temperatures range from 700 to 1500°F

## Factors affecting efficiency
Catalyst activity
Masking or poisoning
Space velocity (gas flow rate divided by bed volume)
Catalyst material

- Factors affecting efficiency
- Catalyst activity
- Masking or poisoning
- Space velocity (gas flow rate divided by bed volume)
- Catalyst material

## Performance indicators
Outlet nitrogen oxide concentration
Catalyst bed inlet temperature
Catalyst activity
Catalyst bed outlet temperature
Inlet gas flow rate
Pressure differential across catalyst bed
Outlet oxygen concentration

- Performance indicators
- Outlet nitrogen oxide concentration
- Catalyst bed inlet temperature
- Catalyst activity
- Catalyst bed outlet temperature
- Inlet gas flow rate
- Pressure differential across catalyst bed
- Outlet oxygen concentration

## General description
Water or steam injected in combustion zone reduces temperature and nitrogen oxide formation
Only thermal nitrogen oxides reduced
Reductions range from 60 to 80 percent
Water must be atomized

- General description
- Water or steam injected in combustion zone reduces temperature and nitrogen oxide formation
- Only thermal nitrogen oxides reduced
- Reductions range from 60 to 80 percent
- Water must be atomized

## NOx Control Techniques – Water or Steam Injection - Schematic

## Factors affecting efficiency
Water quality
Quantity of water injected
Combustor design
Combustor materials
Turbine load cycle

- Factors affecting efficiency
- Water quality
- Quantity of water injected
- Combustor design
- Combustor materials
- Turbine load cycle

## Performance indicators
Outlet nitrogen oxide concentration
Water to fuel ratio
Fuel bound nitrogen concentration

- Performance indicators
- Outlet nitrogen oxide concentration
- Water to fuel ratio
- Fuel bound nitrogen concentration