Sulfur trioxide (SO3) and sulfuric acid not only contribute to elevated opacity and a visual plume, but also heavily influence the performance of a power plant and its air quality control systems. By understanding how much SO3 is present and how to reduce it, many benefits to plant operation and environmental regulatory compliance can result.

For sulfur trioxide (SO3) control and management, AECOM Process Technologies offers the proprietary SBS Injection™ technology in partnership with Codan Development, LLC. We also have years of experience in the field measurement of flue gas constituents, including SO3, to characterize the source and contributors to visible stack opacity emissions, and determine the performance of emission control processes, such as selective catalytic reduction (SCR) systems. Based on our knowledge of emission control technologies, AECOM Process Technologies can also provide engineering studies to evaluate and select the best control technology to meet our client’s plant-specific requirements.

SO3 Removal Technologies and Services

  • SBS Injection™ Technology
  • Performance Testing and Field Measurements
  • Opacity Evaluation Studies
  • Engineering Studies


SBS Injection™

The SBS Injection™ technology is a proprietary process, patented by Codan Development LLC and offered exclusively by AECOM Process Technologies, for the selective removal of SO3 and sulfuric acid (H2SO4) from coal-fired power plant combustion gases. More information on this technology can be found on the technology page.


Performance Testing and Field Measurements

AECOM maintains an extensive Source Emissions Measurements (SEM) capability that includes equipment and personnel for performing a full range of wet chemical and instrument test methods.  This capability is employed across multiple industries for services including process emission characterization, compliance testing, emission control system performance evaluations and continuous emissions monitoring.

The measurement of SO3/H2SO4 in coal-fired boiler flue gas has been an important component of our SEM capabilities for nearly 40 years.  Our work has included the development and validation of the Controlled Condensation System (CCS) sampling methodology for both EPRI and ASTM, and the application of the technology to measure SO3/H2SO4 in difficult conditions such as wet stacks and in the presence of reactive particulate.

Since the late 1990s, the application of SO3 controls on coal-fired utility boilers has become more widespread. AECOM has used its SEM capabilities on literally hundreds of test programs to support our electric utility clients in the development of their SO3 control strategies.  Initially, testing can be performed to quantify the production and/or removal of SO3 along the entire flue gas path.  For example, a unique application of our capabilities is to measure the stack gas concentrations and size distributions of species such as sulfuric acid, soot, fly ash and other particulate, and then determine the contribution of each component to visible emissions and opacity.  When SO3 controls are installed our SEM capabilities can be employed to accurately quantify the performance of the process and to optimize or troubleshoot the process as necessary.  This capability allows our clients to maximize the value of their investment and to minimize on-going operating costs.


Opacity Evaluation Studies

With increased environmental awareness, regulatory agencies have become more aware of “aesthetic” issues. Therefore, plume opacity from stationary combustion sources has become a prominent issue.

To properly and effectively mitigate plume opacity, the root cause of the optical plume must be determined. AECOM has conducted numerous plume opacity root-cause analysis programs at oil and coal burning utilities. These studies incorporate several flue gas sampling techniques, including size fractionation and analysis of particulate matter using cascade impactors and determination of flue gas sulfuric acid content using controlled condensation system method, as well as EPA Methods 5 and 17 to determine total particulate mass loading. The results of these tests are used with a light scattering model to predict plume opacity and to identify its root cause. Past studies have identified sulfuric acid, sub-micron soot (aromatic compounds in the fuel that are not burned), and fly ash/scrubber carryover as the predominant contributors. Once the root-cause of opacity is properly identified, appropriate mitigation technologies can be identified, evaluated, and applied to cost-effectively resolve the issue.


Engineering Studies

Over the last 30 years, AECOM has gained extensive experience testing and evaluating traditional and emerging emission control technologies for EPRI, DOE, EPA and leading electric utilities.  With this knowledge, we can perform comprehensive engineering studies to evaluate a variety of approaches for addressing both opacity and SO3 emissions, including consideration of developmental status, control effectiveness, balance of plant impacts, both operating and capital costs, and implementation schedule.

Related Services & Products
SBS InjectionTM