This paper presents the development of a platform for studying, designing and optimizing complex integrated energy systems. Technology models representing the physical behavior are separated from thermo-economic analysis and multi-objective optimization including energy integration, economic evaluation and environmental impact assessment. Through a Matlab based platform, structured data is transfered between different models. The advantage of dissociating the technology models from the analysis models is that process unit models developed with different software can be assembled in a superstructure for subsequent large processes design and optimization. The approach is illustrated by the thermo-economic modeling and optimization of a power plant with CO2 capture.