TWISTED TUBE® Heat Exchanger Technology chosen to mitigate fouling and reduce fired heater load in crude preheat trains
A major refiner faced two problems in their crude preheat trains. One set of exchangers was hitting thermal and hydraulic limits, and fouling faster than the plant could keep up. Another set couldn’t transfer enough heat to the crude before the fired heater, so the heater was carrying the load.
After evaluating the available technologies in the market, Metalforms was chosen to solve both challenges. TWISTED TUBE® Heat Exchanger Technology delivered optimized fluid dynamics conditions and greater heat recovery than the alternatives.
One project is a retrofit of existing bundles. The other is a combination of replacement bundles and new TWISTED TUBE® Heat Exchangers. Each tackles a different constraint.
Project one: Longer runs from the same shells
The retrofit began as a bundle redesign to mitigate shell side fouling by adopting helical baffles. After discussions with the refiner’s process engineers it was discovered that a problem existed on the tube side as well.
This discovery drastically changed the solution required. TWISTED TUBE® Heat Exchanger Technology addresses both sides. With no baffles, shell-side flow remains uniform, leaving fewer places for deposits to settle. Inside the tubes, higher shear stress at the wall reduces the rate of fouling.
Increased heat duty with longer projected run times made TWISTED TUBE® Bundles the best solution. The TWISTED TUBE® Bundles put significantly more heat transfer surface area into the same shell. That margin results in longer runs between cleanings and fewer maintenance interventions.
Metalforms went past the bundles and incorporated two features that are built to support the run-time and reliability goals.
First, a specialized Rare Earth Oxide (REO) surface treatment from Curran International was added for further fouling protection. The treatment significantly lowers the surface energy and polarity of the ID and OD of the tubes, which reduces fouling. Unlike traditional coatings, it has no measurable thickness, ensuring no added thermal resistance while providing superior protection against fouling and high-temperature oxidation.
As part of the proposal to the Customer, Metalforms also partnered with Sentro Technologies based on their APR (Acoustic Pulse Reflectometry) tube ID inspection method. Sentro will provide baseline inspection for the bundles, which will confirm the integrity of the tubes. The Customer will then have the ability to model defects (i.e., wall loss) throughout the life cycle of the equipment.
Project two: More heat, fewer exchangers
The project involves the exchangers that preheat crude ahead of the fired heater. The refiner set one measure of success: a target outlet temperature.
The original spec called for 16 total exchangers arranged in four units of four. The TWISTED TUBE® Heat Exchanger design does the job with 12 exchangers, at higher heat recovery. Four fewer exchangers mean less to install and less to maintain.
The payoff shows up at the heater. Hotter crude leaving the exchangers means the fired heater has less work to do, so it burns less natural gas. That cuts fuel costs and CO2 emissions. In cases where the heater limits throughput, it can also free up capacity.
What this means for other refiners
Fouling, thermal and hydraulic bottlenecks, and fired heater limits are common across refining and petrochemical operations. These two projects demonstrate that TWISTED TUBE® Heat Exchanger Technology can be applied to new exchangers or retrofitted into existing shells to increase heat recovery. This benefits operating companies that are under pressure to cut fuel costs and emissions. The total number of heat exchangers is also minimized.
Metalforms aims to share measured performance once both units are installed and running.
About Metalforms and TWISTED TUBE® Heat Exchanger Technology
In 2024, Metalforms acquired the TWISTED TUBE® Heat Exchanger Technology and heat transfer business from Koch Heat Transfer. The engineering team behind the technology continues that work at Metalforms, supporting refiners, petrochemical producers, and process operators worldwide.