Co-liquefaction Of Coal And Plastics In Supercritical Water

Supercritical fluid technology is internationally recognized as green technology, which attracts more and more attentions as the reaction medium. Coliquefaction of coal and plastics is a way to use coal resourse cleanly and effectively. It can reuse the waste plastics to reduce the environmental pollution. So the significance of coliquefaction in supercritical water (SCW) is undoubtful.Co-liquefaction of yanzhou coal and plastic (polystyrene or polypropylene ) in SCW was studied in an autoclave. The experiments were carried out to investigate the effects of reaction conditions on the conversion and products yield of co-liquefaction. In order to explore the behavior in the co-liquefaction of coal and plastic, campared the results with that of coal liquefaction. The research can provide foundation datas for the co-liquefaction of coal and plastic in SCW.In SCW, the coal liquefaction was studied. The results indicated that with the increase of water to reactant ratio, the coal conversion increased at 20%-30%. When the ratio of water to reactant was more than 20, the total coal conversion remained constantly, while the yield of oil and gas kept increasing. The conversion of coal and the yield of oil and gas increased dramatically with the temperature increasing (T>420℃). It was found that the conversion reached the highest point as 31.2% at 430℃, meanwhile the yields of oil, gas and asphaltenes were 12.6% and 18.6% , respectively. As the reaction time prolonging, the total coal conversion increased and the maximum of 26.14% appeared at 60min. The conversion of coal and the yield of oil and gas increased with the pressure increasing. The conversion reached the highest point as 28.66% at 36.1MPa, at the same time the yield of oil and gas was 13.02%.The co-liquefaction of coal and plastics was also investigated in SCW. Experimental results showed that in the water phase of coal / polystyrene co-liquefaction the main components were hydroxyphenol, phenol, paracresol and orthocresol, etc. And in the gas phase there were CO2, CH4 and C2H6. The conversion reached the highest point at 60 min, and the maximal conversion at 380℃, 420℃were 60% and 62.3%, respectively. With the increasing of temperature, the yield of oil and gas increased linearly at first and then remained constantly. It was found that the yield of oil and gas reached the highest point as 43.6% at 430℃. The yields of oil and gas for co-liquefaction of coal and plastic were higher, typically by 0.6, 2.7% at 10%, 20% PS, respectively, than the weighted average oil and gas yields for the coal and plastic alone, which implied the synergistic effects on coal conversion.In order to observe the phase change of co-liquefaction in SCW, we studied in fused silica capillary reactor. It was found that in supercritical water PP and PS melt at 127.8℃and 119.7℃, respectively. But the shape of coal changed little.