Asphalt terminal emissions remain an important consideration for asphalt terminal design and production, installation, and market stakeholders. The primary source of emissions in asphalt terminal facilities is the escaping vapors from atmospheric breather vents in tank roofs and open loading domes of truck trailers and railcars. These vapors contain varying concentrations of Hydrogen Sulfide (H2S), mercaptans, and Volatile Organic Compounds (VOCs) which are odorous and reduce the air quality in the terminal facility and surrounding community.
ECF, Inc. has extensive experience regarding the equipment and technologies in use to control the emissions and odors from asphalt processing and loading/unloading facilities. These technologies can not only preserve the air quality for nearby workers, but increase productivity in the facility itself. These are especially important considerations given the asphalt industry’s commitment to reaching net-zero carbon emissions by 2050.
Below is a summation of the currently available technologies and equipment in use to control asphalt terminal emissions and odor as well as the pros and cons of each.
Emissions and Odor Control Equipment
Regenerative Thermal Oxidizer (RTO)
Pros:
- Currently considered the “best available technology” for asphalt vapors and odor treatment.
- Completely decomposes VOCs, hazardous air pollutants (HAPs), and other airborne solvents
- Eliminates opacity & treats H2S
- Has lower operating costs compared to a direct fire thermal oxidizer (DFTO) due to the recovery of the post‐combustion hot gas which is passed down through and pre‐heats the incoming vapor stream
- Recovers 95% of the heat from the combustion process;
Cons:
- SOx emissions
- High initial capital investment
Enhanced Iron Hydroxide Media Bed
Pros:
- Eliminates opacity & treats H2S
Cons:
- Requires periodic replacement of iron hydroxide media and disposal of accumulated oils
- Does not treat the mercaptan odors which require an additional carbon filter
- High initial capital investment
Activated Carbon Filter Bed
Pros:
- Eliminates opacity & treats H2S
Cons:
- High operational costs due to periodic replacement of activated carbon material and disposal costs
- Potential for carbon material to combust
Coalescing Filter
Pros:
- Eliminates opacity
- Lowest initial investment
Cons:
- Does not treat H2S
- Requires regular replacement and maintenance of the filters
- Not a good standalone system for true odor control
- Used directly upstream of the equipment above as a knockout for airborne aerosol/fine mist
Liquid Additives/Masking Agents
Cons:
- Only masks the odor with a stronger odor;
- Dissipates off H2S molecules which creates odor again;
- High resupply costs
- Not truly effective
Direct Fired Thermal Oxidizer
Pros:
- Completely decomposes volatile organic compounds (VOCs), hazardous air pollutants (HAPs), and other airborne solvents;
- Eliminates opacity & treats H2S
Cons:
- SOx emission
- High initial capital cost
- High operational costs
H2S Caustic Scrubber
Cons:
- Little to no use currently in asphalt terminal facilities
- Maintenance intensive
- High initial capital, resupply, and disposal costs
Our Recommendation for Emission Control & Key Considerations
A Regenerative Thermal Oxidizer (RTO) with a properly designed vapor collection system is currently our recommended solution for control of asphalt terminal emissions and odor. Although an RTO has a higher initial capital investment compared to other solutions, its performance and lower long‐term operational costs make it the best choice.
No matter your choice, every system above requires proper ongoing maintenance to operate properly. Frequently, terminal facilities install one of the above systems, fail to follow ongoing maintenance procedures, and end up shutting off the system under the misapprehension that it did not work properly. Then, they will install a second solution to similar results.
Consideration of the vapor gathering system to capture all the asphalt vapors while bringing back as little as possible suspended aerosol/fine mist is very important to any of the above systems. This requires proper design of the collection mechanism on top of each tank to allow heavier condensed oils to drain back into them. The vapor collection header system also requires included knockouts in the main headers and mist eliminators in front of the treatment equipment.
Asphalt Storage and Liquid Terminal Design & Construction Services
ECF, Inc. can design, procure, and install a complete emissions and odor control system tailored to your specific facility operations. Please contact us if you have any questions or if we can be of further assistance in your facility.