The object of research is the stage of regeneration of the spent solution of purification of process gas from CO2 in the production of ammonia with a capacity of 1360–1500 t/day, in a two-section plate regenerator-recuperator. The calculations confirmed the possibility of replacing the monoethanolamine absorbent solution (MEA) with activated methyldiethanolamine solution (aMDEA) for a two-flow purification and regeneration scheme. One of the most problematic places is the lack of a mathematical model of two-flow regeneration of a new absorbent. During the study to determine the composition of the vapor-gas mixture used the method of material balance, which takes into account the temperature of the upper and lower parts of the regenerator and proposed numerical integration to calculate the number of plates of the regenerator.An algorithm and a program of multivariate calculations have been developed and implemented in Excel, which provide for variation of concentration parameters over a vapor-gas mixture. Thermal calculations take into account the endothermic reactions of CO2 desorption, water evaporation and determine the specific heat consumption for solution regeneration. The decrease of specific heat consumption for regeneration of activated aMDEA solution from 4.4 to 3.11 MJ/m3CO2 was determined in comparison with MEA solution. The approximations of the equilibrium pressure of CO2 over the MDEA solution on the degree of carbonization of solution and the desorption temperature are approximated. The kinetic calculation of the regenerator established the number of plates equal to 14 when the number of 31 plates in a standard regenerator-recuperator. The calculated number of plates determines the reliable regeneration of the solution in one apparatus to the required degree of carbonization of coarsely (0.35) and finely regenerated (0.1) solutions. The reduction in the number of plates when using aMDEA is due to taking into account the properties of this solution, in particular, the difference in the equilibrium pressure of CO2 over aMDEA compared to MEA. The real possibility of using 40 % aMDEA solution instead of 18 % MEA solution on existing two-stream absorbers and regenerators without changing the technological scheme is established.