What is mean by economiser recirculation line?

Since sufficient feedwater is not supplied into the economizer though the heat is absorbed from flue gas at the boiler start-up and low load operation, steaming may occur in the economizer. Therefore the economizer recirculation line is provided between the furnace downcomer and the economizer inlet feedwater piping. This line provides the recirculation flow between the drum, the downcomer and the economizer so as to prevent steaming in the economizer. Economizer recirculation valve is only opened at initial stage of the boiler start-up.