Steam boilers are used for refining, bleaching, deacidification, deodorization, fractionation and other processes in the palm oil production. PT.Mikie Oleo Nabati is an Indonesian company established in 2001. The company’s main activity is to process CPO into various products like PFAD, RBD Palm Oil, RBD Stearine, RBD Olein (Cooking Oil) & Margarine. Steam boilers play an important role in their production. The original biomass-fired boilers used by them easily have the problems of scaling, abrasion, burning front arch and feeding hopper, which affect their production lines seriously. The biomass-fired boilers made by ZOZEN can perfectly resolve the problems mentioned above. Therefore, PT.Mikie Oleo Nabati has planned to order several sets of ZOZEN’s quality biomass-fired boilers. Taking the fact that palm shell is used as the fuel by this refinery into consideration, ZOZEN’s professional engineer has made an optimization design for length and width of feeding hopper, rotary speed of gearbox, 1st and 2nd air ratio, etc., to guarantee the sufficient combustion and improve the thermal efficiency. The thermal efficiency of ZOZEN’s biomass-fired boilers can reach above 88%.