A novel process of three-column(pre-distillation,low-pressure,and high-pressure)distillation was proposed for the purification of synthetic methanol.In the new process with double-effect distillation,the reboiler duties of both pre-column and low-pressure column were provided by the vapor distillate of the high-pressure column,which achieved complete heat-integration of heating steam to reduce the total heat consumption of the whole distillation process.At the same time,the soft water from the bottom of the low-pressure column and part of the salt water from the bottom of the high-pressure column were recycled to the pre-column as the extracting water,which achieved complete integration of soft water in the process and eliminated the consumption of fresh soft water and reduced the amount of waste water.A comparative case study by steady-state simulation was carried out for the present Lurgi process,the W-C process in literature and this Z-W process.The result showed that the Z-W process reduced the heat consumption by 21.4 % of the Lurgi process or by 11.7 % of the W-C process,reduced the waster water by 81.4 % of the Lurgi process or by 68.5 % of the W-C process and eliminated the soft-water consumption by 100 % of both Lurgi process and W-C process.
