<p>Dehydrating tower (2) comprising a vertical vessel; screw conveyor (26) for discharging of gas hydrate from an upper part of the vessel; multiple apertures (52) provided on the side of the vessel; drain part (21) defining drain chamber (51) enveloping the multiple apertures (52); and drain pipeline (53) connected to a lower part of the drain chamber (51), wherein the drain pipeline (53) is fitted with flow rate control valve (23) and wherein the degree of opening of the flow rate control valve is controlled by a controller so that the water level of the drain chamber (51) is held at a set water level to thereby regulate the water surface of the drain chamber (51), namely, the water surface for immersion of particulate gas hydrate, attaining control of the concentration of gas hydrate discharged from the dehydrating tower (2).</p>
