the end of valve assembly 41 inside housing 42 includes a plate 51 which covers the end of tube 44 and has an orifice 52 therethrough aligned with tube 44 the effective size of orifice 52 can be adjusted by a shutter plate 53 which is fixed on one end of a shaft 54 journalled in the flanges 43 and 46 adjusting movement of shutter plate 53 is effected by a worm 55 which meshes with gear 56 on shaft 54 and is itself mounted on flange 45 and provided with an operating handle 57 a vaned rotor 58 inside discharge 40 is driven by a motor 59 as described in the kehoe and surino patents to wipe the inlet end of orifice 52 periodically and thereby to keep it free of obstructing solids when the system shown in fig1 is being operated continuously in the practice of the invention a mixture of cooked paper materials and steam will be blown at high speed through the orifice 52 and wear sleeve 45 when this high speed jet strikes the liquid in the tank 50 its rate of travel will be so abruptly reduced that the bits pieces and clumps of paper materials will be explosively disintegrated and distributed in the liquid in the tank 50 to form a suspension of essentially individual fibers it is important that the pipe 47 be as short as possible e g 12 inches in order to minimize the distance that the jet travels before impacting liquid and thereby to minimize the size of the gas bubble which forms before the steam component of the jet is absorbed in the liquid in tank 50 the disintegrating action on.