The invention discloses a biochemical-method ECF (
Extracellular Fluid) bleaching process for KP (Kraft Pulp) of fast growing poplars. The process is characterized by comprising the following steps of: (1) cooking: putting fast growing poplar wood chips into a cooking pot for cooking so as to obtain primary pulp, then, washing and screening so as to obtain paper pulp; (2) carrying out pretreatment by using
xylanase; and (3) bleaching ECF: the bleaching of the paper pulp subjected to
enzyme treatment comprises the steps of: firstly, carrying out
oxygen delignification or intensified
oxygen delignification on the paper pulp subjected to
enzyme treatment; washing the paper pulp after the
oxygen delignification is ended, and then, carrying out D-section
chlorine dioxide bleaching; washing the paper pulp after the D-section
chlorine dioxide bleaching is ended, and then, carrying out E-section treatment; and washing the paper pulp after the E-section treatment is ended, and then, carrying out second D-section treatment. According to the process, an ODED bleaching sequence is adopted to carry out bleaching, the paper pulp with higher whiteness and
viscosity is obtained, and the whiteness of the bleached pulp reaches 88.1% ISO to the maximum and reaches 87.6% ISO to the minimum in the case that the total consumption of ClO2 is 1%; and the whiteness of the ODED-bleached pulp is 85.1% ISO.