This paper is a product of the master thesis "Development and use of power plant model for SSAB EMEA Oxelösund” which was conducted in the spring of 2014 at Swerea MEFOS. This study use process integration in development of a system model for a power plant.The power plant at SSAB EMEA Oxelösund does not have any guidelines how operation at the plant is carried out. Due to separate steam networks, steam turbine and several boilers, a large numbers of options regarding operation are available.The work has resulted in a power plant model which can be used as a planning tool for future operation or momentary operational support. Operations presented by the system model are to maximize revenue for the power plant. The system model is a manual model which demands operators at power plant to insert certain prerequisites in order to receive optimal operation for those conditions. These conditions are fuel availability, district heat and process steam demand together with prioritizing and usage of boilers. Guidelines for district heat production and turbine usage has been developed from the system model. Usage of the model will provide experience how production should be carried out for different conditions.Operational suggestions from the model imply that, compared to operational data, great profits can be gained by operating the plant optimally. This is achieved mainly by reduce usage of oil and secondly by better use of produced steam within the power plant.