Syngas based co-feed and co-production (COCO) system is one of the important parts of sustainable development for energy and chemical industries.Co-feed and co-production factors are two key elements to affect the performance of COCO system.The coal/natural gas co-feed and electricity/methanol co-production system is proposed as the case study.Co-feed factor is defined as the separate ratio of unreacted syngas from methanol reactor unit to gas-steam combined cycle power generator; co-production factor is defined as the exergy ratio between natural gas and coal.The effect of the proposed factors on the methanol yield

exergy loss rate

and product cost was investigated systematically.The effect of the prices of coal and natural gas on product cost was also investigated.The corresponding effect relations were discussed.