The delignification process in this study produced the stdanart of Kappa number pulp (lignin content) of about 19-22 %. The production data of pulp refinery used in this research were taken on September 2, 2019 at the maximum capacity of 4220.6 ADT / D, with tank volume of 5140 m³ dan a height of 68,295 m2. The optimization was conducted by a software application of CFD Ansys Fluent 19.2 with …