I ran a simulation but in the results I only get de CO2 production. I wonder if it is necessary to activate any additional boxes or I am missing something.
As Reald Tashi
mentioned, you have to include the reactions and components to have some estimate for these components.I don't think Aspen Plus is good choice to calculate these contaminants depending on your problem. Try to find some experimental correlations / data if you can.
If you are burning something simple you might be able to use some standard kinetic mechanisms, such as GRI30, and calculate it precisely using Cantera (https://cantera.org/) or other dedicated software.
You don't need Aspen to solve complex chemical reactions such as the one shown below for combustion of landfill gas. CREST is free and easy to use. This ebook is free on Monday (4/12) http://www.amazon.com/dp/B07SW9LWTS
I think you can use rgibbs to produces the thermal and prompt nox, but for the fuel nox, it needs experimental data. You can refer to this paper
https://www.sciencedirect.com/science/article/abs/pii/S0959652618319899?via%3Dihub