Integrated gasification combined cycle (IGCC) process gas waste heat boiler

The invention discloses an integrated gasification combined cycle (IGCC) process gas waste heat boiler. The waste heat boiler can reduce temperature of gasification process gas with temperature as about 1000 DEG C to 250 DEG C, thereby recycling heat of high temperature process gas. Produced overheated steam is used for generating power, and the purification work of the gasification process gas can be easily achieved. The waste heat boiler mainly structurally comprises a two-stage shell-type evaporator, a two-stage shell-type overheater, a one-stage shell-type economizer and an independent steam pocket. Heated faces of each stage of the boiler are connected vertically in series, and the steam pocket is transversely arranged at the top of the boiler. The boiler adopts the mode that the process gas moves in a pipe and work media move outside the pipe, and changes the traditional boiler structure that smoke walks outside the pipe and the work media walk in the pipe. Compared with the IGCC waste heat boilers in o