The internal thermally coupled air separation column (ITCASC) is a frontier of air separation energy savings research. The first principles model of the ITCASC is proposed and is based on the material balance, energy balance, and the related thermal coupling relationship which can be used for further control and design studies. The related solution procedures are given. Detailed behavior analyses are carried out. The research results reveal that the ITCASC process has the perfect separation effect and exhibits different behaviors compared to the conventional air separation column (CASC). The optimization model and the related operation optimization are further explored to gain insight on the energy saving potential of the ITCASC process. Optimization research results show that the ITCASC has about 47 % energy saving potential compared to the CASC process.