Filtration and separation developer Porvair has won a contract with a Chinese state oil company, thought to be worth over $10m.The group's Microfiltration business has reached an agreement with an unspecified oil firm to supply char filtration equipment to a coal-to-substitute natural gas plan, set to be built at an oil refinery in Guandong."Gasification filtration is an important market for Porvair and this is another significant contract win," said group chief executive Ben Stocks."The project uses similar technology to that supplied to POSCO, Reliance and SG Solutions and is similar in scale to the POSCO installation."After-market opportunities exist for all four projects, and a set of spares for POSCO will be shipped in 2015."The group added that it expected deliveries to start in 2016, with commissioning of the plant expected in 2017 and 2018.Porvair shares were up 5.42% to 287.81p at 11:02 on Thursday.