Post-treatment system using pure ammonia gas and method thereof

The present invention discloses a post-treatment system and method using pure ammonia gas, the system using ammonia gas as fuel, comprising: an AOC catalyst disposed upstream of the post-treatment system and in fluid communication with exhaust gas; a cDPF filter, the cDPF filter being in fluid communication with the AOC catalyst, the cDPF filter being located downstream of the AOC catalyst; an SCR catalyst in fluid communication with the cDPF filter, the SCR catalyst being located downstream of the cDPF filter; an ASC catalyst in fluid communication with the SCR catalyst, the ASC catalyst being located downstream of the SCR catalyst; and the ammonia gas supply system is provided with a first injection branch and a second injection branch, the first injection branch is used for supplying ammonia gas on the upstream of the AOC catalyst, and the second injection branch is used for supplying ammonia gas between the cDPF filter and the SCR catalyst. According to the system, the ammonia gas is directly adopted to e