The special design of these tanks ensures the rapid discharging of the complete tank without remaining inside the tank. The tank bottom is of double bottom design where the bottom is equipped with special aeration cloth design. This aeration cloth separates the air supply from the product itself and thus making possible to fluidise the product by means of air from underneath the product. The product will than act as water and will flow automatically to the centre of the bottom of the tank. Because the pressure during discharge in the tank is higher than outside the tank the fluidised material will automatically flow tank into the discharge line. The design of the discharge line in combination with the extra air supply at the discharge line and via the aeration cloth makes sure that optimum mix of air and product is achieved.