Answer
Yes. Some lean-burn Otto-cycle dual-fuel engines can meet IMO Tier III NOx limits in gas mode without SCR or other exhaust-gas after-treatment.
- A very good example is the WinGD X-DF low-pressure dual-fuel engine. WinGD states that X-DF engines operate on the Otto cycle with lean premixed combustion in gas mode, and the lower peak combustion temperature keeps NOx below the IMO Tier III limit without EGR or SCR after-treatment.
- ME-GA can also meet IMO Tier III NOx limits in gas mode without SCR or other exhaust-gas after-treatment. MAN states that because ME-GA uses low-pressure, premixed Otto-cycle combustion, NOx formation is inherently low enough for Tier III compliance in gas mode.