Energy And Economic Analysis Of Coal-to-Synthesis Natural Gas System Based On Integrated Strategies Of Fixed-bed Gasification And Entrained-bed Coal-water Slurry Gasification

To deal with lots of wastewater generated from fixed-bed gasification of coal-to-synthetic natural gas (SNG) process, an integrated gasification process which combines fixed-bed gasification and entrained-bed coal-water slurry (CWS) gasification is proposed in this study. Two strategies of the process are analyzed from the view of energy and economy:(a) direct usage of wastewater for CWS preparation;(b) usage of wastewater with tars and oils separated before.Integrated gasification can improve the cold gas efficiency compared with single entrained-bed gasification. Increasing the proportion of coal handling capacity of fixed-bed gasification can improve the integrated gasification efficiency. Integrated gasification type (b) has advantages of cold gas efficiency and total thermal efficiency over integrated gasification type (a).The economic analysis of coal-to-SNG projects based on fixed-bed, entrained-bed CWS gasification, integrated gasification1((a); fixed-bed/entrained-bed coal ratio is2)and4((b); fixed-bed/entrained-bed coal ratio is2) are made. The fixed asset and total investment of coal-to-SNG project based on integrated gasification are between those of fix-bed and entrained-bed CWS gasification strategy. The strategy which has tars, oils, and naphtha as by-products has lower production cost of coal-to-SNG. Economic benefit analysis of these four projects are made. Financial internal rate of returns of coal-to-SNG projects based on fixed-bed gasification, entrained-bed gasification, integrated gasification1and4are17.43%,7.43%,12.59%and15.29%respectively. Uncertain analysis of coal-to-SNG projects based on two integrated gasification1and4are made. Coal-to-SNG project based on the integrated gasification4has better ability to resist risk and obtains satisfying economic benefit.