Analysis of a slag heat recovery plant by modeling a fixed bed countercurrent heat exchangerSteel is a basic input for the industrial sector of any country. Steel production faces many challenges today, two of which are CO2 emissions and waste generation. In 2017 alone, the absolute emission of CO2 was 65,397 tons. In the same year, the amount of solid waste generated reached the average index of 607 kg per ton of steel, of which 70% were slag (Blast Furnace and Meltshop). The waste of these wastes translates into an economic and environmental problem. The reuse of these wastes faces some challenges, one of them being the slag cooling. Today, slag cooling is done outdoors in most plants, takes up a lot of space and depends on factors such as ambient temperature besides wasting energy to the environment in the form of heat. Projects around the world have been created to address these issues, such as CORSE 50 in Japan and RESLAG in Europe have sought to utilize the sensible heat recovered from slag in CO2 separation, thereby helping to reduce CO2 emissions. It also deals with the problems involving the slag that were mentioned. The objective of this work is to model a fixed bed countercurrent heat exchanger, like the one used in the CORSE 50 project using a one-dimensional (1D) steady state approach, using the Runge-Kutta method, to analyze the amount of energy recovered, the temperature profiles and to compare the modeling results with the experimental data of the project. For this, a routine was developed in MatLab with two possibilities: constant slag and air thermophysical properties, and slag and air thermophysical properties varying with temperature. The equation used to describe temperature was very sensitive to boundary conditions, which resulted in non-convergence of the MatLab model.