To meet client needs, PCL uses its proprietary software to design new concepts, repurpose existing Once Through Steam Generators (OTSGs) and solve lingering operational problems with these complex boilers quickly.
OTSGs are one of the most expensive and important pieces of equipment in heavy oil. They are a counter-flow heat exchanger that uses combustible gases as the heating medium and water as the heated medium. Water is fed through a preheater called the Convection Box and primed to be flashed into steam. Once the hot water exits the Convection Box, it enters the Radiant Section where radiant heat is absorbed to the point where most of the water is turned into steam. The steam then exits the Radiant Section and is pumped into the ground to heat up the viscous heavy oil to be extracted. The OTSG is the only piece of equipment capable of doing this for heavy oil extraction.
During downturns, clients are unlikely to spend capital on new units; however, repurposed units provide a cost-effective solution that helps clients run their businesses more productively.
“Producers can increase production by adding new, larger and more efficient OTSG units,” says Mark Pittser, director, business development and fabrication services, PCL Industrial. “New units have a large footprint and require a significant amount of in demand real estate. As a work around, we’ve found a way to alter existing operational OTSGs.”
By combining our software and engineering experience, we can take an existing single-pass steam generator with a vertical convection box that was built in the 80s or 90s and repurpose it, updating it with a new split-flow horizontal high-efficiency convection box, radiant, electrical and boiler external piping. These alterations will increase its thermal efficiency and throughput of steam.
The alterations we perform to a steam generator save the owner money by increasing the efficiency, reducing operational costs and allowing the owner to produce more steam, while minimizing capital costs to upgrade the site. All of our repurposed steam generators fit in the existing footprint with little to no modification to the site. Another benefit for the producer is the reduction of the steam generator’s total emissions. This saves them operating costs associated with emission penalties and improves the air quality.
“For one client, we increased the thermal efficiency of the units from 77% to 90%. The efficiency gain equates to an annual fuel savings of approximately $280,000 for the operator,” says quality engineer Zach Smith.
Repurposing also allows clients to reuse permits on existing equipment. Producers may have existing permits to operate and air board permits on units they have taken out of service/decommissioned. Taking certain components of the existing out of service/decommissioned steam generators and designing around them allows a permit to be reused.
“New permits are very costly and take time to obtain. First, the producer must perform an environmental impact report, which takes time and money. Additionally, producers must purchase emission reductions credits on the open market. Those credits cost about $300,000 per steam generator,” says Smith. “Reusing existing permits makes sense and provides multiple benefits.”
There are many different variables that need to be considered when optimizing the size and shape of a steam generator. Some variables are constant while others are always changing. If the designer changes one value, many of the others change with it. The key in optimizing a design is knowing what the goal is.
Because our clients who use OTSGs are oil producers, typically, their goal is to produce the maximum amount of oil per day. To achieve this, the OTSG needs to produce the maximum amount of steam it can. Modifying the geometry of an OTSG is a way to help achieve this.
“When we design an OTSG, the first thing we need is the customer’s design conditions. We cannot begin the design process without knowing how much steam our customer needs. We must also know the operating pressure of the unit and what steam quality is required,” says Zach.
“Once we receive this information, we review the customer’s fuel supply and water quality constituents. We take the customer’s data, enter it into our program, and run multiple iterations of calculations to determine the best design. We measure these iterations very closely to see slight differences in gains or losses. We know that over time, these minor adjustments are huge cost-savings, or losses.”
Our designs remain consistent from client to client. In the oil business, many clients are connected to one another, so as we work with one client on a new design, soon thereafter, another client hears about our designs, or witnesses a new design being installed on the lease next to theirs by their competitor. We have been able to solidify client relationships by giving each client the same message and knowing our limitations as it relates to knowledge of how the equipment will operate or the assumptions our program makes in its calculations.
OTSG issues are hard to predict and shutting down a unit and losing production is costly to a client. Our expertise and services we provide allow us to act quickly to resolve a client’s issue when they call. By doing this, we build trust with our clients, deliver results and alleviate their stress by helping them find a solution quickly.