The use of oxygen in industrial burners reduces emissions in processes that require high temperatures.
Oxy-fuel burners can reach temperatures of up to 3,000 degrees Celsius. This technology is employed, for instance, in furnaces at metal smelters where recycled copper is melted.
In oxy-fuel combustion, the combustion air is partially or entirely replaced with oxygen. When less nitrogen-rich air is involved in the combustion process, fewer nitrogen oxides (NOx) are produced.
If pure oxygen is utilised, NOx emissions, which are detrimental to the environment and health are completely eliminated, according to Oilon’s chief business director, Olli Tevä.
He said laws are increasingly restricting NOx emissions which is why interest in oxy-fuel combustion is growing.
“Oxy-fuel combustion is used, for instance, in the production of metals and glass, where exceptionally high temperatures are required,” he said.
With oxygen, the temperature of the burner flame can reach up to 3,000 degrees Celsius, while the maximum in regular air combustion is approximately 2,000 degrees Celsius.
Due to the clean and hot combustion, the flame is also up to 300 times brighter.
“Oxy-fuel combustion enhances the energy efficiency of processes in numerous ways. For instance, elevated temperatures improve heat transfer,” he said.
When flue gas temperatures are high, heat recovery systems function more effectively, resulting in less heat loss.
“Oxygen enrichment can enhance the energy efficiency of the combustion process by up to tens of per cent. Simultaneously, carbon dioxide emissions decrease as less fuel is consumed,” Tevä said.
A hot flame poses a challenge for burner materials, which must endure extreme temperatures. The flame's physical location and the dynamics of the combustion process are designed using computational fluid dynamics (CFD) modelling.
“In practice, one of the most important aspects is to keep the flame at a sufficient distance from the burner nozzle to ensure that the nozzle can withstand the heat stress. This is more difficult in oxy-fuel combustion than in standard air combustion, as the combustion speed is 10 times greater,” Tevä said.
Oilon has been developing oxy-fuel combustion technology since the 1990s. Burners that utilise oxygen are custom-made deliveries tailored specifically for each customer.
Tevä said the supply and mixing of oxygen and fuel are modelled separately for each project.
“One project was delivered to a large copper smelter in Germany. Oilon supplied two custom-made 5 MW burners for anode furnaces used to melt recycled copper,” he said.
In addition to the burners, Oilon provided valve actuators and control systems to regulate the flow of oxygen and natural gas. The furnaces were commissioned in spring 2024.
Transitioning from traditional combustion to oxy-fuel combustion requires a significant investment, and it is generally not profitable for small furnaces.
“In contrast, for large, continuously operating furnaces, adopting this technology is beneficial because the improved energy efficiency offsets the investment costs,” Tevä said.
“However, the widespread adoption of oxy-combustion is hampered by the high costs associated with the production and transportation of oxygen.”
This may change as hydrogen becomes more prevalent in energy production and transport. When hydrogen is produced through electrolysis, oxygen is released as a by-product.
“The oxygen produced during hydrogen production can be used directly in industrial combustion processes. In the future, it is possible that industries utilising oxy-fuel combustion will emerge specifically near hydrogen plants,” Tevä said.