Method for an Arrangement at a Paper Machine

Abstract

The present invention relates to a method for reducing the spreading of additional agent(s) which is/are introduced into the process at a papermaking machine. A flowable paper pulp including fibres and a process liquid and having a consistency of not more than 10% is conducted towards the paper machine's headbox ( 5 ). Prior to the introduction ( 14 ) of said additional agent the consistency of the pulp is increased to a value higher than 10% by removing ( 8 ) process liquid and conducting ( 11 ) it in the upstream direction, while compensating process liquid is introduced ( 13 ) downstream. The present invention also relates to an arrangement at a paper machine, where separating means ( 8 ) are arranged in the process direction before means ( 14 ) for introducing additional agent (s). The arrangement further includes means ( 11 ) for conveying process liquid separated from the process in an upstream direction in the process, as well as means ( 13 ) for a downstream introduction of process liquid from a short circulation in order to compensate for the separated process liquid.

1 . A method for reducing the spreading of additive agent(s) introduced into a a continuous process in pulp preparation for a paper machine, wherein a flowable paper pulp including fibres and process liquid and having a consistency of not more than 10% is conveyed towards a headbox of a paper machine, additive agent the consistency of the pulp is increased to a value of more than 10% by removing process liquid and conveying this liquid upstream, while compensating process liquid is added downstream. 
     
     
         2 . A method as defined in  claim 1 , wherein the consistency of the pulp is increased so that the pulp corresponds to a dry matter content of 20 to 50%, suitably about 25 to 40%, favorably at least 30%, by separating process liquid from the pulp, suitably by means of pressing, which process liquid is conveyed back upstream into the process. 
     
     
         3 . A method as defined in  claim 1  wherein, prior to conveying the pulp forwards towards the headbox, a compensating liquid is added in the form of additive agent(s) containing process liquid from the short circulation of the paper machine. 
     
     
         4 . A method as defined in  claim 1 , characterized in that the additive agent(s) is introduced in connection with a dispersing ( 12 ) of the pulp which has a increased consistency. 
     
     
         5  A method as defined in  claim 1 , characterized in that said additive agent(s) include(s) pigment or other color agents. 
     
     
         6 . An arrangement at a pulp preparation for a paper machine, for restricting a spreading of additive agent(s) upstream in the further process, where the process includes an inlet for a flowable mass having a consistency of not more than 10% and including a fibre material as well as process liquid, a closed circulation system including a headbox for a wire for the paper machine as well as means for introducing said additive agent(s), wherein separating means are arranged in the direction of the process ahead of the means for introducing the additive agent(s) but behind said inlet, which separating means are arranged to separate process liquid from the flowable mass so that the consistency of the mass increases to more than 10%, means for conveying the process liquid which has been separated from the mass upstream into the process, as well as means for introducing process liquid from said closed system downstream in order to compensate the separated process liquid. 
     
     
         7 . An arrangement as defined in  claim 6 , wherein said separating means are capable of increasing, suitably by means of a pressing, the consistency of the fibre containing mass from an initial value of 2 to 10%, typically in the order of about 4 to 6%, to a final value of 20 to 50%, suitably 25 to 40%, favorably at least 30%. 
     
     
         8 . An arrangement as defined in  claim 6 , characterized in that means are arranged to add, in connection with or after said inlet for additive agent(s), compensating liquid from the short circulation system of the paper machine. 
     
     
         9 . An arrangement as defined in  claim 6 , wherein dispersing means are arranged to re-disperse, suitably under addition of said compensating process liquid, the mass from which excess liquidhas been separated, whereby the means for introducing said additive agent(s) favorably are arranged in context with said dispersing means, suitably so that said dispersing means are arranged, in the direction of the process, essentially immediately behind said separating means. 
     
     
         10 . An arrangement as defined in  claim 6 , wherein a separate suction box with a slight vacuum is arranged at such a portion of the wire where a fiber web already has been formed, and that means are arranged for conveying water from such a separate suction box a high up in the system towards a separate overflow. 
     
     
         11 . A method as defined in  claim 3 , wherein said compensating process liquid is introduced in connection with a dispersing of the pulp which has a increased consistency.