Why the heck wouldn't they just add a fine spray of water and air to the exhaust stream, collect the resulting water, distill off the fresh water for re-use, and be left with valuable nitric acid, and its salts? Let the ammonia and urea go to the farmers as fertilizer, as well as the producers of nitric acid, instead of using it to destroy both of those things? Any resulting "Heavy metal salts" will be left in the solids/slury after the nitric (and probably sulfuric) acid(s) are distilled off, and can be classified by their properties, re-dissolved in water, and removed by simply replacing the heavy metals with safer "light metals", such as calcium (calcium carbonate lime) to make calcium nitrate (valuable to farmers) and solid metals of anything heavier than calcium. Granted, something that would produce less waste would be scrap iron (to make a valuable iron-based fertilizer and soil life improver (it will discourage some pest bugs like slugs, and mosses (plants and insects without vascular systems)).
Denitrification catalyst is something that all manufacturers and companies need to understand in this era.
Why the heck wouldn't they just add a fine spray of water and air to the exhaust stream, collect the resulting water, distill off the fresh water for re-use, and be left with valuable nitric acid, and its salts? Let the ammonia and urea go to the farmers as fertilizer, as well as the producers of nitric acid, instead of using it to destroy both of those things? Any resulting "Heavy metal salts" will be left in the solids/slury after the nitric (and probably sulfuric) acid(s) are distilled off, and can be classified by their properties, re-dissolved in water, and removed by simply replacing the heavy metals with safer "light metals", such as calcium (calcium carbonate lime) to make calcium nitrate (valuable to farmers) and solid metals of anything heavier than calcium. Granted, something that would produce less waste would be scrap iron (to make a valuable iron-based fertilizer and soil life improver (it will discourage some pest bugs like slugs, and mosses (plants and insects without vascular systems)).