New Electric Reactor Could Cut Industrial Emissions

Currently, industrial processes in the United States are responsible for about a third of the country’s carbon dioxide emissions, more than the annual emissions from passenger vehicles, trucks, and airplanes combined. Decarbonizing this sector is a difficult but essential step to mitigating impacts on our future climate.

Researchers at Stanford Engineering have designed and demonstrated a new type of thermochemical reactor that can generate the immense amounts of heat needed for many industrial processes using electricity instead of burning fossil fuels. The design, published in Jouleis also smaller, cheaper and more efficient than current fossil fuel technology.

“We have a scalable, electrified reactor infrastructure for thermochemical processes that has ideal heating and heat transfer properties,” said Jonathan Fan, associate professor of electrical engineering at Stanford and lead author of the study. “Essentially, we’re pushing the reactor’s performance to its physical limits, and we’re using green electricity to power it.”

Induction heating

Most standard thermochemical reactors work by burning fossil fuels to heat a fluid that is then circulated through the reactor’s pipes, much like a boiler sending hot water through cast iron radiators in an old house, but with better insulation and at much higher temperatures. This requires a fairly large infrastructure, and there are many opportunities for heat loss along the way.

The new electric reactor uses magnetic induction to generate heat, a process similar to that used in induction cookers. Instead of having to transport heat through pipes, induction heating creates heat inside the reactor, taking advantage of the interactions between electric currents and magnetic fields.

If you want to heat a steel rod using induction, for example, you can wrap a wire around it and run an alternating current through the coil. These currents create an oscillating magnetic field, which in turn induces a current in the steel. And since steel is not a perfect conductor of electricity, some of this current turns into heat. This method effectively heats the entire piece of steel at once, rather than creating heat from the outside in.

Adapting induction heating to the chemical industry is not just about increasing the temperature. Industrial reactors must create and distribute heat evenly across a three-dimensional space and be much more efficient than a typical stove. The researchers determined that they could maximize their efficiency by using particularly high-frequency currents, which alternate very rapidly, in conjunction with reactor materials that are particularly poor conductors of electricity.

The researchers used new, high-efficiency electronic devices developed by Juan Rivas-Davila, an associate professor of electrical engineering and a co-author of the study, to produce the currents they needed. They then used those currents to inductively heat a three-dimensional lattice made of a poorly conducting ceramic material at the core of their reactor.

The lattice structure is just as important as the material itself, Fan explained, because voids in the lattice artificially reduce electrical conductivity even further. And these voids can be filled with catalysts, which are materials that need to be heated to initiate chemical reactions. This allows for even more efficient heat transfer and means the electrified reactor can be much smaller than traditional fossil-fuel reactors.

“You heat a large surface area structure right next to the catalyst, so the heat generated reaches the catalyst very quickly to start the chemical reactions,” Fan said. “Plus, it simplifies everything. You’re not transferring heat from somewhere else and losing it along the way, you don’t have pipes going in and out of the reactor – you can completely isolate it. It’s ideal from an energy and cost management perspective.”

Electrified industry

The researchers used the reactor to power a chemical reaction, called a reverse water-gas shift reaction, using a new sustainable catalyst developed by Matthew Kanan, a Stanford chemistry professor and co-author of the study. The reaction, which requires high heat, can turn captured carbon dioxide into a valuable gas that can be used to create sustainable fuels.

During the feasibility demonstration, the reactor showed an efficiency of over 85%, indicating that it converted almost all of the electrical energy into usable heat. The reactor also demonstrated ideal conditions to facilitate the chemical reaction: carbon dioxide was converted into usable gas at the theoretically expected rate, which is often not the case with new reactors.

“The bigger we make these reactors or run them at even higher temperatures, the more efficient they become,” Fan said. “That’s the story of electrification: We’re not just looking to replace what we already have, we’re creating even better performance.”

Fan, Rivas-Davila, Kanan and their colleagues are already working to improve their new reactor technology and expand its potential applications. They are adapting the same ideas to design reactors for carbon capture and cement manufacturing, and they are working with industry partners in the oil and gas sector to understand what those companies would need to adopt the technology. They are also conducting economic analyses to understand what sustainable, system-wide solutions would look like and how they could be made more affordable.

“Electrification gives us the opportunity to reinvent infrastructure, overcome existing bottlenecks, and shrink and simplify these types of reactors, in addition to decarbonizing them,” Fan said. “Industrial decarbonization is going to require new systems-level approaches, and I think we’re just getting started.”