Hong Kong-listed Panva Gas, through a subsidiary company, has bought a 51% stake in Anshan City Gas in the city of Anshan, Liaoning province for RMB70.5 million. (US$1=RMB8.3).             In a statement, Panva Gas said that wholly-owned Panriver Investments signed the agreement with Anshan City Bureau and Shanghai Investment effecting the purchase. Shanghai Investment will…