For the development of a gas power plant with negative CO₂ emissions using an oxy-fuel combustion system, dedicated units for effective CO₂ separation are essential. Water-driven ejector condenser installation was developed to condense water vapor from the exhaust gas mixture. A prototype experimental rig, supported by a validated CFD model, enables detailed investigation of thermal and flow phenomena, as well as the operation of the ejector under various geometrical and operational conditions. The performance of the ejector was assessed by analysing the condensation efficiency and the pressure increase of the mixture. Experimental activities and CFD simulations contributed to the final design of the spray-ejector condenser, which was optimized for the boundary conditions of a negative CO₂ emission gas power demonstration plant. Design enables the construction and integration of the full spray-ejector condenser system, including all auxiliary components, and its experimental verification.