Separation of fibers

Abstract

There is provided a method for separation of fibers in for instance recycled textile, starting with a mixture comprising cellulose fibers and non-cellulose fibers and then reducing the cellulose chain length of the cellulose fibers so that the limiting viscosity number determined according to ISO 5351 is in the interval 200-900 ml/g, mechanically breaking agglomerates of fibers into smaller pieces, adjusting the concentration of fibers to 0.1-4 wt %, and subjecting the mixture to flotation to remove the non-cellulose fibers. Non-cellulosic fibers such as synthetic fibers can be removed very specifically without or essentially without removing cellulose fibers in the mixture. This gives a very high degree of removal and simultaneously the yield is kept high because no or only few cellulose fibers are removed.

1 . A method of processing recycled textile fibers, in which method a recycled textile fiber suspension comprising synthetic fibers and non-synthetic fibers is processed, and in which method the recycled textile fiber suspension is treated in a flotation stage configured to be executed in at least one flotation cell for removing the synthetic fibers from the recycled textile fiber suspension characterized in that the recycled textile fiber suspension has a fiber feed concentration in an interval of 0.1 to 1.5 wt %. 
     
     
         2 . The method according to  claim 1 , characterized in that in the method the recycled textile fiber suspension is fed to a process system comprising a refiner, in which method the recycled textile fiber suspension is refined in the refiner in a refining stage 
     
     
         3 . The method according to  claim 1 , characterized in that the recycled textile fiber suspension is fed flotation chemicals. 
     
     
         4 . The method according to  claim 3 , wherein the flotation chemicals comprise a surfactant. 
     
     
         5 . The method according to  claim 3 , wherein the flotation chemicals comprise a defoamer. 
     
     
         6 . The method according to  claim 3 , wherein the flotation chemicals comprise a foam stabilizer. 
     
     
         7 . The method according to  claim 3 , wherein the flotation chemicals comprise a substance for increasing or decreasing water hardness. 
     
     
         8 . The method according to  claim 1 , characterized in that in the method the recycled textile fiber suspension is treated in the at least one flotation cell for a flotation time of 6-12 min. 
     
     
         9 . The method according to  claim 1 , characterized in that an amount of removed synthetic fibers in a final reject out from the at least one flotation cell depends on the synthetic fibers amount in a feed of the recycled textile fiber suspension and an amount of synthetic fibers in the reject is in the interval 16.2-60.7 wt %. 
     
     
         10 . The method according to  claim 1 , wherein the non-synthetic fibers comprise cotton fibers. 
     
     
         11 . A process system for processing recycled textile fibers comprising synthetic fibers and non-synthetic fibers in a recycled textile fiber suspension, characterized in that the process system comprises at least one flotation cell for removing synthetic fibers from the recycled textile fiber suspension having a fiber feed consistency of non-synthetic fibers 0.1-1.5%. 
     
     
         12 . The process system according to  claim 11 , characterized in that the process system further comprises a refiner for refining the recycled textile fiber suspension in a refining stage. 
     
     
         13 . The process system according to  claim 11 , characterized in that the at least one flotation cell comprises at least one flotation stage. 
     
     
         14 . The process system according to  claim 11 , characterized in that the at least one flotation cell comprises at least one recovery stage. 
     
     
         15 . The process system according to  claim 11 , characterized in that in the process system the at least one flotation cell is located after a filter for a filtering stage. 
     
     
         16 . The process system according to  claim 11 , wherein the non-synthetic fibers comprise cotton fibers.