The calculated distance (air line) between Mörfelden-Walldorf and Duisburg is approximately 127 miles respectively 205 kilometers.
By car or train, the actual journey to Duisburg is certainly longer, as only the direct route (as the crow flies) between Mörfelden-Walldorf and Duisburg has been calculated here.
Air line (approximately)
205 kilometers
111 nautical miles