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Refinery expansion projects often involve a complex balance of construction schedules, production demands, environmental compliance requirements, and operational reliability. While new equipment may ultimately provide long-term capacity improvements, facilities frequently need to maintain steam production well before those assets are installed and commissioned.
Nationwide Boiler - Horizontal Flow Urea Based CataStak SCR System
Horizontal Flow Urea Based CataStak SCR System
Such was the case when a major Gulf Coast refinery began an expansion project that included the addition of two 300,000 lb/hr superheated package watertube boilers. Although the new boilers would provide significant future capacity, the typical timeline from order placement to startup meant the units would not be available for approximately 18 months.
The refinery, however, required additional steam much sooner.
Supporting the expansion required approximately 400,000 lb/hr of temporary steam capacity, but capacity alone was not enough. The solution also needed to meet strict space, ultra-low NOx emissions, and tight project schedule requirements. Nationwide Boiler was selected to provide a temporary steam plant capable of meeting all three.
Meeting a large-scale temporary steam demand
To meet the demand, Nationwide Boiler deployed six (6) 75,000 lb/hr, 750 psig / 750°F superheated steam trailer-mounted package watertube rental boilers. However, providing 400,000 lb/hr of temporary steam required more than simply supplying boiler capacity.
Space limitations quickly became a critical consideration. With six boilers and SCR systems slated for the rental, minimizing the equipment footprint was essential. Nationwide Boiler's trailer-mounted rental boilers feature removable gooseneck and running gear assemblies that can be detached after installation, reducing the overall footprint once onsite. This unique design provided the flexibility needed to fit six boilers within the available space while maintaining the advantages of rapid transportation and deployment.
With the steam demand addressed, attention turned to what would become one of the project's most challenging requirements: emissions compliance.
Navigating complex emissions and site requirements
The refinery's emissions requirements demanded ultra-low NOx performance while maintaining the flexibility and rapid deployment expected of a temporary steam solution.
At the same time, the site presented physical limitations that complicated the use of standard emissions-control equipment. Conventional selective catalytic reduction (SCR) system rentals were commonly configured as vertical-flow units utilizing anhydrous ammonia as the NOx reducing reagent. These systems typically required elevated support structures that would exceed the refinery's allowable height restrictions. The customer also expressed a preference for an alternative to anhydrous ammonia for the temporary installation.
These factors eliminated the possibility of using Nationwide’s traditional SCR arrangement and required a different approach.
Developing a customized SCR solution
To meet both the refinery's site restrictions and emissions objectives, Nationwide Boiler engineered a ground-mounted, horizontal-flow SCR system utilizing diesel exhaust fluid (DEF), a 32.5% urea solution, as the reagent.
The horizontal configuration allowed the SCR systems to remain within the refinery's height limitations while eliminating the need for elevated support structures. The use of urea also provided an effective alternative to anhydrous ammonia while maintaining the emissions performance required for refinery operations.
Nationwide Boiler - Rental Boilers and Urea SCRs
Rental Boilers and Urea SCRs
Delivering six custom SCR systems within the project's aggressive schedule required multiple engineering, fabrication, and integration activities to occur simultaneously. In addition to the SCR equipment, six dedicated urea supply skids were designed and built specifically for the application. All systems underwent testing and quality assurance inspections prior to shipment.
From initial design through equipment delivery, the complete SCR systems were engineered, fabricated, and prepared for operation in approximately ten weeks, helping support the refinery's expansion schedule.
Achieving ultra-low emissions performance
Successfully fitting the equipment within the site constraints was only part of the challenge. The systems also had to demonstrate that they could consistently achieve the required emissions levels during operation.
The refinery specified emissions limits of 9 ppmvd NOx (corrected to 3% O₂) with ammonia slip limited to 10 ppm. Achieving this level of performance was made possible through careful engineering, detailed system modeling, and a design approach tailored to the refinery's specific operating conditions and emissions objectives.
Drawing upon decades of emissions-control experience, including projects in California where ultra-low NOx requirements have been standard for many years, Nationwide Boiler designed a system that not only met the refinery's emissions requirements but exceeded them.
Throughout the rental period, the temporary steam plant achieved average emissions performance of approximately:
- 6 ppmvd NOx at 3% O₂
- 7 ppm ammonia slip
- 25 ppmvd or less CO emissions
These results demonstrated that the newly developed SCR systems could successfully support a large-scale refinery application while consistently meeting demanding environmental requirements.
Maintaining reliable operations around the clock
Beyond equipment performance, ensuring reliable operation of a six-boiler temporary steam plant required ongoing operational support. The refinery did not have sufficient personnel available to operate the additional boilers, so Nationwide Boiler provided trained operators for 24/7 operation and maintenance of the temporary facility.
Dedicated onsite personnel monitored equipment performance, performed routine maintenance, supported startups, and responded immediately to operational issues. If a boiler experienced an unexpected shutdown, operators could quickly diagnose the cause, implement corrective actions, and restore steam production to the header.
To further improve reliability, the project team developed a fault analysis during the planning phase to identify potential operating conditions that could contribute to nuisance trips or operational disruptions. This proactive approach provided operators with valuable troubleshooting guidance throughout the project.
An unexpected role during the Texas freeze
Although originally intended as a temporary solution during the refinery expansion, the rental steam plant ultimately remained in operation for more than three years.
During that time, the equipment was called upon to support the facility through one of the most significant industrial disruptions in recent Gulf Coast history: the Texas freeze of 2021.
Extreme weather conditions caused widespread equipment and instrumentation failures throughout the region, resulting in shutdowns across numerous industrial facilities. The refinery was not immune to these challenges.
Working alongside the customer and local support teams, Nationwide Boiler helped restore the temporary steam plant following the initial weather-related shutdown. Within four days, the rental equipment was operating again and providing steam needed to support startup activities throughout the facility.
The temporary boilers played an important role in helping the refinery resume operations, contributing to the facility becoming one of the first refineries along the Houston Ship Channel to return to service following the freeze.
Delivering lasting value beyond the project
What began as a temporary steam solution evolved into a project that addressed a wide range of operational challenges, including capacity requirements, site restrictions, emissions compliance, aggressive schedules, and long-term reliability.
The successful implementation of the horizontal-flow, urea-based SCR systems not only met the refinery's immediate needs but also demonstrated a practical alternative for facilities where traditional SCR configurations may not be feasible. Following the project's success, Nationwide Boiler expanded the concept into a fleet of urea-based rental SCR systems that are now available for temporary steam applications across North America.
For facilities facing major turnarounds, plant expansions, equipment replacements, or emergency outages, the project illustrates the value of combining temporary steam capacity with innovative engineering solutions tailored to the specific requirements of the application. When complex projects demand more than a standard solution, experience, engineering expertise, and operational support can make all the difference.
Learn how Nationwide Boiler can support your steam generation and emissions requirements at www.nationwideboiler.com.
