Green fertilizer: local production for self-sufficiency

Nithesh Mohun, business development manager for thyssenkrupp’s green hydrogen-based solutions, talks about Africa’s need for more local fertilizer plants to enable local farmers to meet the demands of their fast-growing populations.

thyssenkrupp Uhde can offer the whole green fertilizer process chain from ammonia to urea,ammonium nitrate or UAN, using experience from many such projects successfully executed.

“From engagements with clients across Africa, we are finding an increasing need for fertilizer plants,” begins Nithesh Mohun of thyssenkrupp Uhde in South Africa.

“African farmers are currently importing their fertilizer and producers in South Africa are exporting into many surrounding countries. However, geo-political influences are disrupting global supply chains and driving the prices of fertilizer to prohibitive levels. This presents opportunities for African economies to become self-reliant, particularly with respect to food security. To this end, countries such as Kenya, Nigeria, Ethiopia, and Rwanda, amongst others, have announced projects establish their own fertilizer production industries,” he explains.

While there is a broad range of different fertilizers, he says that the African market tends to focus more on the nitrogen-based products, such as ammonium nitrate (AN) fertilizers, and urea ammonium nitrate over phosphorous based fertilizers. This is primarily due to the lower cost and greater availability of nitrogen fertilizers.

The common ingredient for the production of nitrogen-based fertilizers is ammonia (NH₃), which is produced from the reaction between hydrogen (H₂) and nitrogen (N₂). This is known as the Haber-Bosch process. If the hydrogen is produced by the steam reforming of natural gas (CH₄), then the resultant ammonia is called grey ammonia. However, if the hydrogen is produced from renewable resources such as solar, wind or hydroelectric, then the resultant ammonia is called green ammonia.

thyssenkrupp Uhde Ammonium Nitrate Fertilizer Solutions

Once the ammonia has been produced, the next step is the manufacture of nitric acid (HNO₃). Nitric acid is produced by oxidizing ammonia through the Ostwald Process. The ammonia and nitric acid are then reacted to produce ammonium nitrate solution (NH₄NO₃). The ammonium nitrate solution can be further processed into solid forms such as prills, granules or crystals.

thyssenkrupp Uhde offers a portfolio of state-of-the-art solutions for the production of all types of ammonium nitrate-based fertilizers. “With plant capacities of up to 2,000 mtpd, we are one of the world-leading licensors of these processes,” says Nithesh Mohun.

Of particular note is uhde® ammonium nitrate vacuum neutralization process (Figure 1), a proprietary process that offers exceptional reliability and safety during plant operation. “This process features a system for mixing ammonia and nitric acid and a forced circulation system for cooling the AN solution produced. The process ensures stable operating conditions with high efficiency and low emissions,” he says.

The uhde® ammonium nitrate vacuum neutralization process is characterized by high product quality in accordance with international standards; high reliability and long operating times; highest safety in operation due to sophisticated process and control concepts; and low operating temperatures, which avoid the decomposition of AN and the formation of potentially harmful aerosols.

“The plants also offer easy start-up and shut-down and they offer high energy efficiency. Low maintenance and better corrosion resistance – due to low operating temperatures – are also features, which all makes these plants very cost effective.

“We have many references for proven worldwide plants sized between 200 and 2,000 mtpd of AN, which are ideally suited for local production of fertilizers across the African continent,” Mohun adds.

null — Figure 1: The Uhde vacuum neutralization and evaporation process.

Urea and UAN

UAN (urea ammonium nitrate) is a mixture of ammonium nitrate, urea, and water. Typical nitrogen concentrations of UAN are 28%, 30% or 32%. Depending on the customer's requirements, UAN can be enriched with soluble plant nutrients (sulfur, boron, and calcium compounds).

Uhde offers two processes for the production of UAN i.e. a) ammonium nitrate mixing with urea and, b) Neutralization of urea off-gas, in capacity ranges from 540 to 4,300 mtpd in a single train.

Ammonium Nitrate Mixing with Urea Solution:

Ammonium nitrate (AN) is produced in the Uhde ammonium nitrate neutralization process as described above. The AN solution is then mixed with the urea solution and water in a special UAN mixing unit to obtain the required nitrogen content and adjusted to an alkaline pH (see Figure 2). After cooling and addition of corrosion inhibitor, the final UAN solution can be easily stored and handled. The contaminant level in the process condensate is normally below 15 ppm.

Neutralization of Urea off-gas:

When implementing a once-through urea synthesis, the ammonia-rich off-gas can be used to drive the ammonium nitrate neutralization reaction (see Figure 3). Due to the high CO₂ content of the off-gas, the neutralization reaction is performed in a natural gas circulation loop, followed by the UAN preparation steps described above. A sophisticated scrubbing system is installed to reduce ammonia losses in the vent gas.

“The thyssenkrupp Uhde name is synonymous with first-class technologies, which are subject to constant refinement, excellent management, modern international procurement from the global market and decades of experience in all corners of the globe.

We can offer the whole process chain from ammonia to urea, ammonium nitrate or UAN out of one hand using experience from lots of such projects successfully executed.

We believe, therefore, that we are in an excellent position to help countries all over Africa to meet their local fertilizer needs – from local resources such as air, water, captured CO₂ and renewable energy. Not only can this help to meet growing food production demands, but it could also help the continent to become more environmentally friendly and sustainable,” concludes Nithesh Mohun.