Nitric acid is required in large quantities in fertilizer production. Messer has developed a process to make production more efficient and reduce nitrogen oxide emissions at the same time.
Around 60 million tons of nitric acid (HNO₃) are needed worldwide every year, 80 percent of which is used as a precursor in the fertilizer industry. Its production requires (atmospheric) oxygen, ammonia and water. These raw materials are converted through complex reaction chain. The basic process was developed back in 1902 by the chemist Wilhelm Ostwald. Among other things, nitrogen oxides are formed, the emission of which is subject to strict environmental regulations. It is therefore essential to minimize the formation of these compounds as much as possible.
Simple vs. Complex
The nitric acid production process has been improved in detail over the years. The main focus has been on energy efficiency and reducing emissions by technically optimizing the plants. However, this approach is complex and cost-intensive. Messer has developed a process that enables a considerable increase in efficiency and reduces nitrogen oxide emissions - without any major technical effort.
"We achieve these goals by introducing pure oxygen," explains Hicham Azzouzi, expert for chemical applications at Messer. "Certain reaction steps, such as the oxidation of nitrous acid and dinitrogen tetraoxide, are much more intensive and achieve significantly better results." The key is to inject the gas at very specific points in the process using a method developed and patented by Messer.
Low investment, great benefits
The investment required is very manageable, especially in relation to the yield. This is shown by the example of a nitric acid plant in Romania that was built back in the 1960s. The efficiency of production was lower than required by today's standards, resulting in the release of excess nitrogen oxides. In order to keep these emissions within the limit values, the plant regularly had to be operated at reduced capacity or shut down completely for long periods during the warm summer months.
With the oxygen injection process installed by Messer, nitrogen oxide emissions fell from 220 ppm to 20 ppm (ppm = parts per million, millionths) in the test. The standard emission limit value in the EU is 90 ppm. The absorption of nitrogen oxides before the DeNOx plant was significantly improved - some of these gases are converted into harmless nitrogen. The supply of ammonia in the DeNOx plant, fell by 50 kilograms per hour at this point. At the same time the production volume increased by 260 kilograms per hour. This gain was further increased by longer operating times: as the plant now also complies with the strict EU regulations for nitrogen oxide emissions in warm weather, it can also operate at full capacity during the summer months without forced breaks.
For more than 125 years, Messer, the today’s world's largest privately owned company for industrial gases, medical gases, specialty gases, and gases for electronics, committed to its guiding principles of safety, focus on customers and employees, responsibility for our society, sustainability, trust, and respect. Messer's Gases for Life and patented gas applications are essential for environmental protection, climate protection, decarbonization, and innovation.
