The 4000 dwt tanker Clipper Sund suffered a chemical explosion while moored at a quay at Antwerp, Belgium.    The explosion was caused by three chemicals leaked out.   They came into contact  which caused a chain reaction and resulting explosion and fire.   One crewman suffered severe injuries and later died in hospital.   The explosion occurred on the deck of the tanker limiting the damage to the vessel.   A hazardous materials team is assisting in cleanup.