The study applies a new technique for evaluating the NOx concentration when burning syngas in the gas turbine combustion chamber. The technique allows correlating the complete detailed mechanism of the Grimech 3.0 array of parallel reactions with the computer hydrodynamics equations (motion, heat and mass transfer, turbulence, and molecular diffusion equations for an ideal gas flow). Selectivity diagrams of the NOx formation process including eleven key reactions are built based on the specific reaction rates for lean and rich fuel mixtures. Verification calculations have been performed based on a model gas turbine combustion chamber within a fuel-air equivalence ratio of 0.5-2. The new technique has been applied for determining the NOx emissions and the maximum temperature of the industrial combustion chamber fire tube wall. The GE gas composition showed the best NOx emission result. The most problematic is Polk Power and Texaco syngas (oxygen process). When burning LCV gases in the primary air suction area, a recirculation zone is observed; due to the high heat release in this area, the maximum wall temperature is about 500 °С.