The work presents the results of numerical modeling of a horizontal cyclone reactor of low-temperature thermal-chemical conversion of brown coals. It carries out the verification of an in-built aerodynamic model ANSYS CFX according to the data obtained in an experimental installation, performs the modernization of initial installation and the comparative analysis of operation parameters and compositions of gases obtained in two designs. The study also carries out the optimization of the location of the branch pipe for secondary air supply in a modernized installation.