The study looked at how different forms of carbon in coal interact with gases during a process called gasification. By using special reactors, the researchers found that these interactions can greatly affect how nitrogen in coal is converted into harmful gases like HCN and NH3. When oxygen is present, the carbon structures in coal break down easily to form these gases. But without oxygen, the nitrogen in coal forms different, less harmful compounds. This shows that the way coal and gases interact during gasification can change the types of pollutants produced.