In order to deal with lots of waste water containing tar

oil and phenols generated by fixed-bed gasification process of coal to synthetic natural gas (SNG)

two integrated systems are proposed

which combine two gasification processes in fixed-bed and coal-water slurry (CWS) entrained-bed.One is that the waste water generated by fixed-bed gasification process of coal is directly used for CWS preparation and another only using waste water containing phenols without tar or oil.In coal to SNG project

they are investigated and evaluated from the view of energy

and the system of highest cold gas efficiency is analyzed from economic point of view.The results show that compared with single entrained-bed gasification process

the fixed-bed/entrained-bed integrated strategies can improve cold gas efficiency. When the ratio of handling capacity of fixed-bed/entrained-bed is 2

coal consumptions are 563 kg·km-3 (CO+H2+3.12×CH4) for the first integrated gasification system and 599 kg·km-3 (CO+H2+3.12×CH4) for the second one

oxygen consumptions 212 m3 O2·km-3 (CO+H2+3.12×CH4) and 206 m3O2·km-3 (CO+H2+3.12×CH4)

cold gas efficiencies 84.44% and 86.74%

and total thermal efficiencies are 72.53% and 74.87% respectively.Compared with fixed-bed gasification process

the production cost of coal to SNG doesn't increase remarkably for the first integrated system

the strategy is economically available.