Integrated Gasification Combined Cycle (IGCC) is one of the most promising technologies for power generation; the environmental benefits and the higher energy conversion efficiency distinguish it from traditional coal generation technologies. IGCC performance is affected by different technological and operational aspects, e.g. gasification technologies, gasifier agent, coal rank, environmental conditions, and power demand. This group of conditions hinders the assessment process and conduces necessarily to the use of thermodynamic simulation tools. In this work thermodynamics analysis simulations were conduced in Hysys and GateCycle. Simulations in Hysys were carried out for different gasification technologies, kinetic reactions, gasifying agents and coal types. Syngas composition and lower heat values were calculated for the all different conditions and had been loaded into GateCycle in which Combined Cycle efficiency were studied for different environmental conditions. Results show behavior for IGCC technologies at different places according to its environmental and operational conditions, and coal rank.