Podcast
Questions and Answers
Exhaust stacks reduce emissions from a stationary source.
Exhaust stacks reduce emissions from a stationary source.
False (B)
Fugitive emission points are those that are confined in a stack or duct.
Fugitive emission points are those that are confined in a stack or duct.
False (B)
Pollution control can include changes in production processes.
Pollution control can include changes in production processes.
True (A)
Tall smokestacks are ineffective in dispersing pollutants.
Tall smokestacks are ineffective in dispersing pollutants.
Signup and view all the answers
Relocation of the source is the first step in the control strategy for environmental impact.
Relocation of the source is the first step in the control strategy for environmental impact.
Signup and view all the answers
Compliance with emission standards relies solely on technology.
Compliance with emission standards relies solely on technology.
Signup and view all the answers
Utility and smelter operations typically use stacks that measure between 200m to 400m high.
Utility and smelter operations typically use stacks that measure between 200m to 400m high.
Signup and view all the answers
The use of effective control devices is one of the PM control procedures for stationary sources.
The use of effective control devices is one of the PM control procedures for stationary sources.
Signup and view all the answers
Centrifugal separators are commonly referred to as gravity settlers.
Centrifugal separators are commonly referred to as gravity settlers.
Signup and view all the answers
Fabric filters can have efficiency rates greater than 99.5% for particles larger than 5 micrometers.
Fabric filters can have efficiency rates greater than 99.5% for particles larger than 5 micrometers.
Signup and view all the answers
Fabric filters cannot be used for gases above 260°C.
Fabric filters cannot be used for gases above 260°C.
Signup and view all the answers
In a suction type baghouse, the dirty gases are forced through the outside of the bag.
In a suction type baghouse, the dirty gases are forced through the outside of the bag.
Signup and view all the answers
Natural fiber fabrics used in filters can withstand temperatures up to 90°C.
Natural fiber fabrics used in filters can withstand temperatures up to 90°C.
Signup and view all the answers
Hybrid systems are solely based on fabric filtration without any combinations of other control mechanisms.
Hybrid systems are solely based on fabric filtration without any combinations of other control mechanisms.
Signup and view all the answers
Gravity settlers can result in low pressure losses as an advantage.
Gravity settlers can result in low pressure losses as an advantage.
Signup and view all the answers
Mechanical collectors like cyclones are not effective in removing solid particles from gas streams.
Mechanical collectors like cyclones are not effective in removing solid particles from gas streams.
Signup and view all the answers
Wet electrostatic precipitators are one of the major hybrid systems found in practice today.
Wet electrostatic precipitators are one of the major hybrid systems found in practice today.
Signup and view all the answers
Cyclones can effectively collect particle sizes down to 50 μm.
Cyclones can effectively collect particle sizes down to 50 μm.
Signup and view all the answers
The cut diameter at 50% removal is referred to as d0.5.
The cut diameter at 50% removal is referred to as d0.5.
Signup and view all the answers
Dry scrubbers are not considered a major hybrid system in current air pollution control.
Dry scrubbers are not considered a major hybrid system in current air pollution control.
Signup and view all the answers
The cut diameter formula for cyclones includes factors such as particle density and gas flow rate.
The cut diameter formula for cyclones includes factors such as particle density and gas flow rate.
Signup and view all the answers
The effective number of turns ($\theta$) in a cyclone is calculated as $\theta = \frac{0.25}{(2L1 + L2)}$.
The effective number of turns ($\theta$) in a cyclone is calculated as $\theta = \frac{0.25}{(2L1 + L2)}$.
Signup and view all the answers
The particle density for the example given is 800 kg/m3.
The particle density for the example given is 800 kg/m3.
Signup and view all the answers
In the context of cyclones, an average particle diameter of 10 μm will have a high removal efficiency.
In the context of cyclones, an average particle diameter of 10 μm will have a high removal efficiency.
Signup and view all the answers
Catalytic incinerators operate similarly to thermal incinerators but require higher temperatures for oxidation reactions.
Catalytic incinerators operate similarly to thermal incinerators but require higher temperatures for oxidation reactions.
Signup and view all the answers
The primary materials used in catalysts for VOC incineration are typically platinum and palladium.
The primary materials used in catalysts for VOC incineration are typically platinum and palladium.
Signup and view all the answers
Combustion, adsorption, absorption, and condensation are methods used to capture or destroy gases.
Combustion, adsorption, absorption, and condensation are methods used to capture or destroy gases.
Signup and view all the answers
The temperature range needed to preheat the waste stream for oxidation reactions is between 200 to 800oF.
The temperature range needed to preheat the waste stream for oxidation reactions is between 200 to 800oF.
Signup and view all the answers
Control devices such as thermal incinerators and catalytical incinerators are ineffective in managing air pollution.
Control devices such as thermal incinerators and catalytical incinerators are ineffective in managing air pollution.
Signup and view all the answers
Flaring is an effective method for complete destruction of VOCs, achieving destruction rates of greater than 90%.
Flaring is an effective method for complete destruction of VOCs, achieving destruction rates of greater than 90%.
Signup and view all the answers
The particle size distribution of emissions is one of the crucial parameters for selecting air pollution control equipment.
The particle size distribution of emissions is one of the crucial parameters for selecting air pollution control equipment.
Signup and view all the answers
Non-assisted flares are effective for streams with low carbon/hydrogen ratios that require less air for combustion.
Non-assisted flares are effective for streams with low carbon/hydrogen ratios that require less air for combustion.
Signup and view all the answers
Catalysts in catalytic incinerators also allow for larger incinerator sizes.
Catalysts in catalytic incinerators also allow for larger incinerator sizes.
Signup and view all the answers
The moisture content of exhaust gas does not impact the selection of pollution control techniques.
The moisture content of exhaust gas does not impact the selection of pollution control techniques.
Signup and view all the answers
Electrostatic precipitators (ESPs) are a type of control device used to manage particulate emissions.
Electrostatic precipitators (ESPs) are a type of control device used to manage particulate emissions.
Signup and view all the answers
Flare designs differ mainly by how well they mix air with combustibles.
Flare designs differ mainly by how well they mix air with combustibles.
Signup and view all the answers
Combustibility of exhaust gas is not considered significant in pollution control equipment selection.
Combustibility of exhaust gas is not considered significant in pollution control equipment selection.
Signup and view all the answers
Auxiliary fuel is not necessary for flaring processes to promote mixing of VOCs.
Auxiliary fuel is not necessary for flaring processes to promote mixing of VOCs.
Signup and view all the answers
Gravity settlers, also known as settling chambers, are utilized for controlling particulate emissions.
Gravity settlers, also known as settling chambers, are utilized for controlling particulate emissions.
Signup and view all the answers
Anticipated changes in raw materials are irrelevant for the selection of air pollution control equipment.
Anticipated changes in raw materials are irrelevant for the selection of air pollution control equipment.
Signup and view all the answers
Thermal incinerators are used to destroy gaseous pollutants primarily composed of volatile organic compounds (VOCs).
Thermal incinerators are used to destroy gaseous pollutants primarily composed of volatile organic compounds (VOCs).
Signup and view all the answers
The destruction efficiency of VOCs in thermal incinerators can exceed 99.9%.
The destruction efficiency of VOCs in thermal incinerators can exceed 99.9%.
Signup and view all the answers
Thermal incinerators operate at temperatures below 650°C (1200°F).
Thermal incinerators operate at temperatures below 650°C (1200°F).
Signup and view all the answers
The residence time for waste gas in thermal incinerators is usually designed to be more than 1 second.
The residence time for waste gas in thermal incinerators is usually designed to be more than 1 second.
Signup and view all the answers
Studies suggest that running commercial incinerators at 870°C (1600°F) with a residence time of 0.75 seconds leads to 98% destruction of non-halogenated organics.
Studies suggest that running commercial incinerators at 870°C (1600°F) with a residence time of 0.75 seconds leads to 98% destruction of non-halogenated organics.
Signup and view all the answers
Soot is a substance that can be partially destroyed by thermal incinerators.
Soot is a substance that can be partially destroyed by thermal incinerators.
Signup and view all the answers
Carbon adsorbers are primarily used for controlling particulate matter emissions.
Carbon adsorbers are primarily used for controlling particulate matter emissions.
Signup and view all the answers
Thermal incinerators are considered one of the least effective methods for destroying VOCs.
Thermal incinerators are considered one of the least effective methods for destroying VOCs.
Signup and view all the answers
Study Notes
Air Pollution: Control of Stationary Sources
- Stationary sources of air pollution primarily stem from incomplete fuel combustion or industrial processing.
- The specific pollutants emitted depend greatly on the industrial process.
- Examples of pollutants include ash, sulfur dioxide, nitrogen oxides, mercury, and various metal dusts (like iron oxides). Other sources may emit fluorides, chlorides, and organic waste gases.
- Stationary industrial pollution sources can be grouped into categories based on their specific process operations:
- Process Operations: These involve incomplete chemical reactions, e.g., combustion with unconverted reactants, or reactions yielding less product than expected.
- Atmospheric Releases: These are the secondary components or impurities from raw materials released into the atmosphere.
- Auxiliary Losses: This pertains to the loss of compounds (e.g., volatile organic solvents, carbon disulfide, hydrogen sulfide, fluorine compounds) during various industrial processes.
- Waste Emissions: Exhausts from oxidation, heating, or drying processes can contain malodorous or oxidation compounds.
- Emission points originate from various locations and may not be collected centrally before entering the atmosphere. These include stack, duct, vent, fugitive and area release points.
- Whether an emission source is classified as "point" or "fugitive" is determined by whether the release is confined in a duct or stack prior to release into the atmosphere.
- Table of industrial process operation air emission points and categories:
- Process Operations: Examples include reactors vents, distillation systems, vacuum systems, combustion stacks, blow molding, spray drying and booths, and extrusion machines.
-
Categories (Fugitive Sources) Examples: Valves, pump seals, flanges/connectors, compressors, open ended lines, pressure relief devices, equipment cleaning, handling storage loading, storage tank breathing losses, loading/unloading, line venting, packaging and container loading.
- Surface Area Sources: Examples: Pond evaporation, cooling tower evaporation, wastewater treatment, and land disposal.
Pollution Control
- Effective pollution control involves common-sense solutions:
- Installation of effective control technology.
- Modifications to production processes.
- Implementation of pollution prevention techniques.
- Compliance with emission standards hinges on implementing appropriate stationary source control measures.
PM Control Procedures
- General control procedures for stationary pollution sources:
- Using tall smokestacks.
- Modifying plant operations.
- Installing effective control devices.
- The control strategy for industrial environmental impacts involves four steps:
- Eliminating the source causing the problem
- Modifying the operations of the source.
- Relocating the source.
- Selecting and applying the appropriate control technology.
Exhaust Stacks
- Exhaust stacks elevate pollutant emissions, reducing local impact by dispersing them over a larger area.
- In the past, tall stacks were a common, inexpensive solution but posed regional concerns, and transboundary issues like acid rain.
- Tall stacks transferred issues to different locations rather than solving them.
Plant Operations
- Meeting emission standards sometimes necessitates control technology implementation.
- Pre-treating raw materials, changing manufacturing processes, or changing fuels can all reduce emissions. Coal washing is one example of pre-treating.
- Substituting cleaner fuels (such as natural gas or low-sulfur fuels) is another viable emission control method.
Plant Maintenance
- Reducing emissions also involves increased attention to plant maintenance.
- Improperly maintained equipment, often combustion equipment, is a common cause of significant pollutant releases.
- Regular maintenance of equipment (vats, valves, and transmission lines) helps reduce fugitive emissions and the risk of spills.
Control Technology
- Advanced, add-on control technology plays a key role in pollution control.
- Control devices can either destroy or recover pollutants. Techniques include combustion, adsorption, absorption, and condensation.
- Various devices implemented for these processes are thermal incinerators, catalytic incinerators, flares, boilers, process heaters, carbon absorbers, spray towers, and surface condensers.
- Exhaust gas characteristics (flow rate, temperature, efficiency requirements), and site characteristics (space, power availability, water, regulations) are crucial for selecting air pollution control equipment.
Exhaust Gas Characteristics
- Total exhaust gas flow rate.
- Exhaust gas temperature.
- Required emission control efficiency.
- Particle size distribution.
- Particle resistivity.
- Composition of exhaust gases over operating range.
- Moisture content of the exhaust gases.
- Stack pressure.
- Exhaust gas combustibility and flammability properties.
Process or Site Characteristics
- Reuse/recycling of collected emissions.
- Availability of space.
- Availability of additional electrical power.
- Availability of water.
- Wastewater treatment facilities.
- Frequency of startup and shutdowns.
- Environmental conditions.
- Anticipated changes in control regulations.
- Anticipated changes in raw materials.
- Plant type (stationary or mobile).
Control Devices for Particulate Emissions
- Technologies for controlling particulate matter aim at removing particles from the gas stream.
- Various factors affect the optimal design (particle size, chemical characteristics).
- Common particulate control devices include gravity settlers (settling chambers), mechanical collectors (cyclones), electrostatic precipitators (ESPs), scrubbers, fabric filters, and hybrid systems.
- A combination of techniques is sometimes the most effective solution, e.g., a settling chamber could be used to remove large particles before smaller particles are managed by an ESP.
Equipment
- Gravity Settlers (Settling Chambers): Used to remove solids and liquids from gas streams. Characteristics include simple construction, low initial cost, low maintenance, low pressure losses, and easy waste disposal.
- Mechanical Collectors (Cyclones): Wide industrial use; centrifugal separators.
Fabric Filters (Bag Houses)
- Fabric filters (bag houses) perform filtration.
- Material types (natural fibers, synthetics, fiberglass) influence maximum operating temperatures.
- Cleaning mechanisms like shakers, reverse air, and pulse jet techniques are implemented.
Baghouse Filter
- Similar in efficiency to domestic vacuum cleaners.
- High efficiency for fine particle, removal (>99%).
Hybrid Systems
- Hybrid systems combine multiple control mechanisms (e.g., fabric filters with electrostatic precipitation).
- Wet electrostatic precipitators.
- Ionizing wet scrubbers.
- Dry scrubbers.
- Electrostatically augmented fabric filtration are examples.
Cyclones
- Used for particles between 10 and 100 microns.
- Simple, no moving parts, reliant on inertial forces.
Electrostatic Precipitators (ESPs)
- High efficiency, dry collectors of particulate matter. Use high voltage direct current (30–75 kV).
- Two major types: tubular and plate. Plate type is more common.
Wet Scrubbers
- Used in wet conditions, corrosive environments, or high temperatures where baghouses aren't suitable.
- High efficiency frequently achieved using a venturi scrubber in combination with a cyclone.
Scrubbers (Venturi Scrubbers)
- Wet scrubbing involves bringing the contaminated gas streams into close contact with a liquid (usually water).
- Wet scrubbers are part of a broader category of gas absorption equipment.
Comparison of Air Pollution Control Devices
- Graph illustrates the comparative removal efficiency of various air pollution control devices across different particle sizes.
Effectiveness of Air Pollution Control Devices
- Chart shows effectiveness of various air pollution control devices across different particle sizes and pollutant diameters.
Gaseous Emissions
- Control of gaseous pollutants usually involves add-on control devices for either destruction or recovery of the pollutant.
- Control Equipment: Includes thermal incinerators, catalytic incinerators, flares, boilers and process heaters, carbon adsorbers, absorbers, and condensers.
Thermal Incinerator
- Used for destroying volatile organic compounds (VOCs).
- Controlled burn at high temperatures.
- High efficiency (up to 99.9%).
Applicable Pollutants
- Primarily VOCs.
- Some particulate matter (PM).
Catalytic Incinerators
- Similar to thermal incinerators but uses catalysts to increase oxidation reaction rates and lower temperatures.
- Catalysts commonly used include platinum and palladium.
Flares
- Primarily used as a last resort for gases of limited recyclability or those not easily combustible.
- Burning gas in an open flame.
Boilers and Process Heaters
- Usually used for generating heat and power.
- Can recycle pollutants to be used as fuel, if suitable to the burner.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz covers various methods and technologies used in air pollution control, including exhaust stacks, filtration systems, and emission standards. It explores the effectiveness of different strategies for reducing emissions from stationary sources. Test your knowledge on how pollution control devices work and their efficiencies.
