Duty exemption for Liquid Natural Gas (GNL in Brasil) equipment

I understand there is a duty exemption for Liquid Natural Gas (GNL in Brasil) equipment. I cannot find and NCM that confirms this.

We manufacture systems to allow heavy-duty vehicles to operate on Liquid Natural Gas (GNL). we are trying to begin importing this system into Brasil and need to understand the import duties and taxes better. We have been told that systems like ours could be exempt.

Can you help?