Abstract: A process arrangement in the short circulation of a paper machine comprises devices (10-13) for dilution of thick stock, centrifugal cleaners (14), and a headbox fan pump (16), as well as a pipe system connecting these. There is a direct flow connection from the centrifugal cleaners (14) along a pipeline (30) to the headbox fan pump (16), through which pipeline (30) a centrifugally cleaned stock flow (F6) is passed direct to the headbox fan pump (16) without any deaeration or dilution stages in between. A secondary line (32) is connected to the pipeline (30) for passing through it part of the centrifugally cleaned stock flow as a return flow (F7) back to the thick stock dilution devices (10-13). By this arrangement it can be ensured that the pressure on the suction side of the fan pump (16) remains substantially constant.

Abstract: The invention relates to an apparatus for passing stock to a headbox (100) of a paper machine or equivalent. The apparatus comprises a deaeration tank (11) which is provided with vacuum by means of a vacuum pump (Po) or another device. The deaeration tank (11) comprises an inlet duct (10) through which it is supplied with wire water. The deaeration tank (1) comprises a discharge duct (12) and, at the discharge end thereof, an overflow (14) for the wire water in the discharge duct (12). Said overflow (14) of the discharge duct (12) is located below the deaeration tank (11) and opens to a free air space, and that the discharge duct (12) includes a branch duct (15a1) for a flow which is passed to the headbox (100).

Abstract: The invention relates to a method and a mixer for mixing flows of a papermaking process. In the invention, a first flow is conveyed through a tube, and turbulence is generated in it by means of form parts located on the inner periphery of the tube. The mixing zone of the mixer comprises feed openings on the inner periphery of the tube for feeding a second flow from a feed channel outside the tube into the first flow, whereby the flows are mixed as a result of the turbulence generated by the form parts. According to a preferred embodiment of the invention, at least one form part comprises a feed opening.