Container tank as well as method for emptying the same

The tank (1) comprises an outer rigid wall which defines a volume (15A,16A) divided into two by an interior flexible wall (12A). The flexible wall is formed from an elastic membrane. The upper volume stores a bulk dry product and the lower volume is filled with a working gas for a programmed raising of the product during emptying of the tank. An Independent claim is included for the tank emptying process.