Possibilities of developing high-efficiency and high-output second harmonic generators for mini TEA CO2 laser are studied. The system of shortened equations for interacting waves along with the two-dimensional heat conduction equation is solved. These equations describe second harmonic generation (SHG) taking into account the effect of thermal blooming. The efficiency of SHG with ZnGeP2, CdGeAs2, AgGaSe2, HgGaS4, Tl3AsSe3, and GaSe nonlinear crystals was estimated depending on the crystal length and optical quality. The following CO2 pump laser parameters were used: wavelength of 9.55 mkm, pulse energy of 50 mJ, pulse duration from 1 to 100 ns, pulse repetition rate up to 1 kHz. The additional angular tuning of the crystals that maximizes SHG efficiency as well as the optimal crystal lengths providing for its maximum at a fixed pump pulse repetition rate were determined as well. The possibility of developing second harmonic generators with high (up to tens of watts) mean power has been proposed.