Can root Zelkowa acuminata requirements production trough pan liquid gas distributor the overflow tray and sieve tray liquid distributor and the anti clogging ability greatly improved, to avoid the danger of liquid entrainment, riser is rectangular, as far as possible provided through the supply of free space (open hole rate in more than 30%, the operation elasticity up to 1:10), the pressure is reduced to 500pa, trough pan liquid gas distributor production is not limited by the size and material.