Coal gasification to syngas is a common technique for coal utilization and consumes large amount of energy. The design and operation of gasifier, washing column and heat exchangers affect the energy consumption and carbon emission of the whole system. In this work, a coal to syngas process is simulated by Aspen Plus software. Based on the simulation results, the integration among the coal gasification, shift process and rectisol process are analysed; the heat exchanger network (HEN) is optimised to minimize the energy consumption and the carbon dioxide emission. The utility consumption is reduced by 17.4 %, and the emission of CO2 is reduced by 5.1 %.