The high efficiency of a combined cycle and the availability of systems for deep purification of syngas before combustion allow for the study of combined-cycle gas turbines as a promising solution to increase the efficiency and environmental friendliness of coal power engineering. The key element of the device is a gasifier. A Mitsubishi Heavy Industries gasifier is selected as an initial design for modernization, which consists in heating the blast air up to 900°C and supplying vapor with a temperature of 900°C. The impact of modernizing the gasifier characteristics is determined by using zero-, one-, and three-dimensional models. The modernization of the gasifier allows increasing the thermal power by the syngas and cold gas efficiency from 77.2 to 84.9% and increasing the ratio H2/CO from 0.34 to 0.6.