The calculated distance (air line) between Sint-Gillis-bij-Dendermonde and Seraing is approximately 68 miles respectively 109 kilometers.
By car or train, the actual journey to Seraing is certainly longer, as only the direct route (as the crow flies) between Sint-Gillis-bij-Dendermonde and Seraing has been calculated here.
Air line (approximately)
109 kilometers
59 nautical miles