Low-emission power technologies with gas turbines are intensely developed and implemented as the most promising energy technologies based on fossil fuels. One promising solution under strong development is a technology using gaseous fuel combustion in pure oxygen when the exhaust gas mixture is composed of H2O and CO2. The paper presents results of computational analyses providing to the Spray-Ejector Condenser (SEC) development, which is one of the crucial components of the being under development negative CO2 gas power plant (nCO2pp) cycle. The Spray-Ejector Condenser is developed to ensure high effectiveness of processes such as the condensation of vapor and compression of CO2 with preparation for separation. Firstly, the main operating conditions in the characteristic points were investigated to evaluate the impact of the operating conditions on the SEC performances. The amount of motive water needed for the cooling purpose is susceptible to the inlet water pressure and temperature and strongly affects the generated pressure of the suction stream. Inside the SEC, the steam and CO2 generated in the Wet Combustion Chamber (WCC) of nCO2pp are in direct contact with cold water. The heat transfer coefficient can reach high values during the direct contact condensation inside the Spray-Ejector Condenser. Still, inert CO2 in the gas stream can significantly reduce the rate of condensation. The development of SEC in thus operating conditions needs to use advanced computational methods and approaches to develop basic design, which is one of the main project goals. The paper presents adopted numerical and analytical approaches leading to the development of the characteristic dimensions of developed SEC and the opportunity to investigate the turbulent flow of water/steam/CO2 mixture together with the condensation process occurring at this same time. The paper also presents the preliminary results of a basic design and geometrical dimensions of the Spray-Ejector Condenser to be applied in the negative CO2 power plant cycle at two different variants. The further direction of the presented computational research activities and results is to test various designs of Spray-Ejector Condensers that will enable the evaluation of the direct contact condensation process and develop the final geometrical design.