The current environmental policies of the EU regarding waste management focus on a circular economy concept with an emphasis on the reduction of the waste that goes to landfills. In this context, the reuse of sewage sludges as an energy resource can be an attractive solution, mainly for the sector of paper and wastewater treatment plants. The plasma gasification of sewage sludges, even challenging, is pointed out as an option for waste valorization. However, several technical aspects must be investigated in order to make this solution attractive to the market. The conversion of the chemical energy contained in this raw material into the desired syngas depends on several factors such as the adequate configuration of the gasification system, its dimensioning, as well as the correct definition of the gasifier operating conditions. To provide a solution, this work focus on the design of a plasma gasifier for the valorization of sewage sludges. Data is provided regarding the sewage sludge composition and origin, using a DSC-TGA technique and the selection of the different elements that compose the gasification system in function of the expected operating conditions is provided. Also, a first approach related to a mass and energy balance estimation was performed. Moreover, a numerical simulation is conducted in order to characterize the flow dynamics inside the reactor and the evolution of the temperatures that have a critical impact on the raw material gasification.