Gas combustion unit (GCU)

A gas combustion unit is a thermal oxidizer that safely burns excess boil-off gas on an LNG carrier when the engines and any reliquefaction plant cannot consume all of it, holding cargo-tank pressure within limits without venting methane to atmosphere. It is essentially a controlled-air burner with a stack, sized for the worst-case BOG rate. It is the pressure-relief sink of last resort short of the safety relief valves, and it avoids the strong global-warming effect of vented methane.