Stock inlet for a papermaking machine etc has one or more fluid injectors at the turbulence tubes to inject controlled fluid doses with min effect on the total suspension vol flow

摘要

The stock inlet, for a papermaking machine and the like, has a fluid dosing system (4.1-4.3) to inject a fluid into the zone with the turbulence tubes (1.1,1.2,2.1,2.2,3.1,3.2). The suspension flow speed is <= 9 m/sec. and pref. <= 5 m/sec. directly in front of the fluid injection point and pref. also after the injection point in the flow direction. At least one turbulence tube has at least one reduction in its flow cross section at the fluid injection point, in the flow direction, followed by an expansion in its flow cross section. At least one flow cross section reduction and/or expansion has a step structure. Inserts (8) in the turbulence tubes give the flow cross section change. The fluid injection point is selected so that, after it, at least 50% of the total pressure loss originates in the tube, and pref. at least 75%. At the fluid injection point (4.1-4.3), the turbulence tube (1.1,1.2,2.1,2.2,3.1,3.2) has a contour change to give space for the fluid injection units between neighboring tubes. At least one fluid injector (4.1-4.3) is a dosing tube, with at least one side opening and at least at one opening into the turbulence tube. An O-ring is in a groove (7) between the dosing tube and the turbulence tube, which seals the passage for the fluid injection between them. The dosing tube (4.1-4.3) has a round outer cross section over at least part of its length, and can rotate around its longitudinal axis in at least a part of its length., to adjust the alignment between the opening (5) in the dosing tube and the opening (6) into the turbulence tube and vary the vol. of injected fluid into the turbulence tube. At least one turbulence tube has a number of fluid injection points, with at least two injection points in succession in the suspension flow direction, or facing each other at the tube. At least one turbulence tube has an inserted bush (16), to reduce the flow cross section, upstream of a fluid injection point, to give a step flow reduction. The fluid injection system is in a number of overlaid rows with the turbulence tubes, and the injectors are operated by motors to set the dosed vol. of injected fluid. The fluid injection system has a recirculation for the fluid which has not been consumed; The turbulence tubes have a soft and malleable structure where the fluid injectors (4.1-4.3) are fitted, and have a different fluid flow cross section before and/or after the fluid injection point. An Independent claim is included for the injection of fluid into the turbulence tubes of a stock inlet, where the dosed injection can be adjusted individually at each tube. Preferred Features: The flow cross sections are altered at the fluid injection points to accelerate and decelerate the suspension flows by adjusting the flow resistance. The fluid injection dosage is varied according to measurements from the paper web at the papermaking machine. Different fluids can be injected into the turbulence tubes at different points.