Less Is More: Small 3D-Printed Parts Boost Marine Fuel Efficiency, Lower Emissions
The enormous ships that transport liquefied natural gas (LNG) around the world — called LNG carriers — can sometimes transport the equivalent of 100 Olympic-size swimming pools of the supercooled fuel in their hulls. These floating fuel warehouses burn hundreds of thousands of gallons of fuel oil and gas themselves during a typical 20-day voyage. Every year, engines in these giant vessels release millions of tons of nitrogen oxide (NOx).
The solution — developed by engineers at John Zink Hamworthy Combustion, a Koch Industries company focused on pollution prevention technology — can fit in the palm of your hand. Harnessing the unique properties of additive manufacturing (a technical term for 3D printing), they redesigned the engine’s fuel atomizer, a small metal component that is now radically boosting the efficiency of an LNG carrier’s propulsion system and slashing its NOx emissions. Paul Newman, the general manager at John Zink Hamworthy in Poole, a coastal town in the south U.K., explains that 3D printing has been a game-changing technology. “Without additive manufacturing, there's no way we'd be where we are now,” he says.
The vast vessels moving LNG around the world are normally dual-fuel operated. They burn gas, as well as diesel or heavy fuel oil. Equipment called marine burners inject that diesel or oil into furnaces that fire the ship’s boilers, producing the steam that spins the turbines to propel the vessel.
This is where the atomizer comes in — a key piece of equipment that helps reduce the potential risks of injecting highly combustible fuel as a flowing liquid. Deep inside the burners, the atomizer mixes high-pressure steam with the oil, pulverizing the fuel into thousands of small droplets. It works like a miniature shower head, creating a superheated, highly combustible mist for the burner to spray into the furnace. “The droplets then mix with the oxygen in the air and create a flame once you give it an ignition source,” explains Newman. The fuel atomizer may be small, about the size of a baseball, but it plays a big role in tanker propulsion.
An effective atomizer helps to boost the efficiency of a ship’s propulsion system. But a well-designed atomizer can be an essential tool for reducing emissions from these ships. Just as finely ground coffee imparts more flavor, well-atomized fuel burns more efficiently. That means ships can run a lean fuel mix — whereby the diesel or oil burns in a relatively high volume of air — with no significant impact on propulsion performance.
Ships that use conventional atomizers run around 20-25% fuel load, says Newman. “With the additive manufacturing design, we can get that down to 5%,” he adds. A lean fuel mix isn’t just good for using less of a ship’s diesel or oil stocks, it also reduces the temperature of the furnace’s flame, delivering lower NOx emissions and reducing ships' impacts on air quality.
The traditional manufacturing process for building an atomizer involves traditional casting and drilling processes, but that does not allow for intricate designs that can pulverize fuel more effectively, which is the key to delivering the essential lean-burn mix. Newman explains that conventionally milled steel components are essentially lumps of metal that require various subtractive modifications, like drilling holes in it, before use.
Additive manufacturing is different. Instead of chipping away at a block of metal, the component is built, layer by layer, from the ground up. This allows engineers to design complex 3D geometries that are physically impossible to replicate with traditional subtractive manufacturing techniques.
Additive manufacturing could deliver a micrometer-perfect design, but most 3D printing is done using plastic. Atomizers need to be made from specially hardened steel that can weather the rigors of steam and hot oil. John Zink Hamworthy engineers needed to also ensure that the finely sculpted component could withstand the searing heat and high pressure of the furnace. The additive materials would need those same qualities once melted into shape.
But how can steel be printed? Using technology from Desktop Metal — a 3D metal printing company Koch Disruptive Technologies has invested in. The 3D metal printer heats bound metal rods, which are metal powder held together by wax and polymer binder, and extrudes the metal layer by layer, shaping the part following the design.
“We created something that included all sorts of weird shapes, strange chambers, and things that you can't do conventionally,” says Newman. Following a few rounds of experimentation, they were ready to mint the real thing.
The John Zink Hamworthy team’s 3D-printed atomizer design is acorn-shaped adorned with airfoils in the pattern of a flower’s petals. Each airfoil sports a tiny crescent-shaped hole. They experimented with a range of shapes for the holes, trying circles, squares, oblongs and slots, before settling on the crescent shape, which skims oil into much finer droplets. This kind of breakthrough would have been impossible with conventional casting, where engineers could only vary the size of the circular hole they bore. “If we hadn't used additive manufacturing, we couldn't get the shapes that we were making,” says Newman.
But they couldn’t just hit “print.” John Zink Hamworthy engineers subjected the component to thousands of hours of rigorous testing. “This is fired into a purpose-built furnace, full size, with the right pressures, the right flow rates, in the right burner, and in the right environment,” Newman explains. “You need to know before you send it out onto a ship that it's going to work.”
The 3D-printed atomizer does more than work; it makes significant improvements in emissions reduction and energy efficiency. The conventional atomizer allowed the burner to achieve a flow rate of fuel of around 120 kilograms per hour. “With this one, we can get down to 30 kilograms an hour,” says Newman. In switching to this atomizer, an LNG carrier with three burners that is undertaking a three-week voyage from Qatar to Japan would save several metric tons of fuel oil or diesel. Over several voyages, that translates into hundreds of kilograms of NOx emissions saved from the air.
Additive manufacturing — 3D metal printing, in this case — has other transformative advantages over conventional techniques for the John Zink Hamworthy team, customers and the industry. Newman explains that additive manufacturing might, in the future, erode the notion of a physical supply chain for certain parts. “If the customer has the machine at the port, we can send them a file, which they can print,” he says.
It’s that continuous process of iterating, improving and destroying current business models and platforms, that drives the culture at Koch companies, as well as the investments of Koch Disruptive Technologies (KDT). KDT’s goal is to find opportunities to create mutual benefit by accelerating the value of disruptive companies and the transformation of Koch. But it’s not only monetary investment — KDT helps companies accelerate even beyond the capital infusion by leveraging Koch’s worldwide network of companies and partners, as they become customers, suppliers, and validators of new technology. It’s why Desktop Metal has been able to scale its innovations with John Zink Hamworthy, working together to reimagine a solution for reducing emissions and finding greater fuel efficiency.
Newman says that nobody should be fooled by the size of the component. “The actual value is not necessarily in the actual component itself, but in the [decades of] engineering that's gone into designing and building it,” he explains. Those years are now paying off — for customers and for the environment. Newman concluded, “It's not a future thing. It's a ‘now’ thing.”