Recovering hydrogen from ammonia at large scale

Making ammonia from nitrogen and hydrogen via the Haber-Bosch process has been critical to fertilizing the world’s crops for more than a century, but there’s been little need to run the reaction in the opposite direction.

That’s about to change.

Interest in using low-carbon ammonia as a fuel is taking off, and companies, often encouraged by government incentives, plan to spend billions of dollars building ammonia plants for this market. Some plants will make it from blue hydrogen, whose production involves reforming natural gas and capturing and storing by-product carbon dioxide. Other plants will make it from green hydrogen, which is created by electrolyzing water with renewable electricity.

Unlike hydrogen, ammonia can be easily shipped around the world. Upon delivery to the customer, it will be burned directly in ship engines or in power plants designed for coal. Or it will be cracked to get the hydrogen back for running fuel cells or power plants designed for natural gas.

The engineering firm KBR is one of a handful of companies developing technology for cracking ammonia. To say KBR has experience with the molecule is an understatement. About half the world’s ammonia plants today license KBR’s production technology.

“Until recently, ammonia has been a nitrogen carrier for the fertilizer market, which is feeding the world,” says Elena Stylianou, global head of KBR’s ammonia-cracking technology business. “That has been an amazing market, and it has been really good to KBR. But what we’ve been seeing in the last 2 or 3 years is this huge interest in ammonia as a hydrogen carrier.”

KBR worked out the initial process in 2017 but left it on the shelf because there wasn’t a call for it yet, Stylianou says. The company “started seriously developing” the technology in 2022 when it was certain of a market.

KBR calls its process H2ACT, which stands for “hydrogen from ammonia-cracking technology.” It begins with liquid ammonia, which is heated and then sent to a “precracker” that partially dissociates it. In the next step, a large cracking furnace completes the conversion of ammonia into hydrogen and nitrogen.

After cracking, a water wash dissolves excess ammonia. At this stage, the gas mixture is 75% hydrogen and 25% nitrogen by volume, fine for firing some power plants. To get to higher purities, for example the 99.9% hydrogen purity needed for applications like fuel cells, a pressure-swing adsorption system removes the nitrogen.

About 80% of the hydrogen used to make ammonia comes out of the process as a product. Because hydrogen-containing tail gases are recycled for heat, the overall energy efficiency of KBR’s process is about 88–90%, KBR says.

KBR kept the process simple to get it to market quickly. “What we’ve done as KBR is try to select the most proven, most reliable well-known technology elements that we can to put together this new technology,” Stylianou says. These elements include the purification sections, compressors, heat exchangers, and ammonia pumps, all familiar to the company from its ammonia process.

In addition, the reactors use commercially available nickel-based catalysts. “They’re cost effective and have very good activity for dissociating ammonia,” Stylianou says.

Other elements are new, she says. For instance, KBR made metallurgical upgrades to defend against nitrogen ions that can migrate into metals and cause corrosion.

KBR has already granted a pair of licenses, both to companies in South Korea, for its cracking process. The first, announced last September, went to the energy firm Hanwha Impact, which intends to build a unit in Daesan with 200 metric tons (t) per day, or about 70,000 t per year, of hydrogen capacity. The second was for a unit with a capacity of 10 t per day that ISU Chemical wants to build in Ulsan.

East Asian countries— Japan and South Korea in particular—will be the earliest adopters of ammonia cracking, Stylianou says. These countries have few energy resources of their own and rely on imports of liquefied natural gas and coal to run their power plants. They aim to reduce CO₂ emissions by importing blue ammonia from natural gas–rich regions like North America and green ammonia from sunny countries like Australia.

The ammonia market is in the early stages of a boom. S&P Global Commodity Insights forecasts that demand for low-​carbon ammonia will hit 420 million t per year by 2050. The market for conventional ammonia today is roughly 200 million t.

KBR is ready to build for its clients enormous ammonia-cracking plants that consume more than 8,600 t of ammonia per day to produce 1,200 t of hydrogen per day. “At the moment, there is no single ammonia plant that can produce this much,” Stylianou says.

But as they pursue a fuel market that is potentially far larger than the fertilizer market, firms are planning ammonia plants of unprecedented size. KBR recently introduced designs for ammonia plants that produce 10,000 t per day. The rate-limiting step, Stylianou says, isn’t the technology but the willingness of licensees to build the plants.