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Hydrofluorocarbon (HFC) working fluid with high global warming potential are step out of the stage of history due to the intensifying global greenhouse effect. Supercritical water gasification (SCWG), an effective and clean waste disposal method, may have better potential for the conversion of waste HFCs working fluid. ReaxFF reactive molecular dynamic and density functional theory method are used in this work to investigate the SCWG mechanism of HFC-245fa. The results indicate that the main products of HFC-245fa SCWG are high value-added chemicals and fuels such as CO, CO 2 , H 2 , and HF. During the gasification process, almost 100 % of the F atoms in HFC-245fa have the potential to become HF, which means that the SCWG method has a strong defluorination effect. The generation of H 2 molecules is promoted and the formation of CO molecule is inhibited in the presence of H 2 O molecules. More importantly, hydrogen bonds are formed between HFC-245fa and H 2 O molecules, which results in the dissociation of HFC-245fa is improved by the SCWG environment. This work provides an available and environmentally friendly route for the efficient conversion of waste HFCs to fuels. [Display omitted] • Supercritical water gasification method has a better defluorination effect. • Almost 100 % of the F atoms in HFC-245fa have the potential to become HF. • Hydrogen bonds promote the decomposition of HFC-245fa and H 2 O molecules. • HF, H 2 and CO rich products could be selectively produced. [ABSTRACT FROM AUTHOR]

Organic Rankine cycle (ORC) and supercritical CO 2 (sCO 2) Brayton cycle are two key and competition technology routes as the power cycle of Lead–Bismuth micro-reactor (LBMR). However, few studies focus on the comparison of thermodynamic and economic performance between ORCs and sCO 2 cycles in nuclear micro-reactor. The objectives in this study are to perform parameters analysis and techno-economic comparison in ORCs and sCO 2 cycles with various configurations as the power cycle of LBMR, so as to provide the technical support for the selection of power cycle and its operating conditions in different scenarios. Several high/low-temperature working fluids are screened for ORCs in view to achieve high net efficiency (η th) and low electricity production cost (EPC). Multi-objective optimization is performed to solve the trade-off between η th and EPC , and then to compare the comprehensive performance of various cycles from thermodynamic, compact and economic aspects. Results show that, the η th and EPC of ORCs are comparable or superior to that in sCO 2 cycles when the two cycles have similar structures (simple/regenerative). Among the ORCs, the cascade ORC with two-side regeneration using N -Dodecane/Pentane as working fluid pair has the best performance. In all cycles, recompression sCO 2 cycle performs best, but only when the heat source temperature is higher than 460 °C, the performance of the recompression sCO 2 cycle are overall better than the cascade ORC. • Techno-economic comparison of various power cycles for LBR are conducted. • Several high/low-temperature fluids are screened in different configurations of ORC. • N -Dodecane/Pentane is the best working fluid pair for the cascade ORC2. • The η net and EPC of ORCs are slight superior to sCO 2 cycles with similar structures. • The η net and EPC of recompression sCO 2 cycle are both better than ORC when t s > 460 °C. [ABSTRACT FROM AUTHOR]

Pyrolysis is one of the potential way for the degradation of hydrofluorocarbons, but it is difficult to make effective use of the complex pyrolysis products. The addition of plastics can provide sufficient hydrogen source for the degradation of hydrofluorocarbons to generate the high value-added chemicals and fuels. Density functional theory calculation and reactive molecular dynamic simulation are employed to investigate the co-pyrolysis mechanism of 1,1,1,2-tetrafluoroethane and low-density polyethylene in this work. The results show that the H atoms provided by low-density polyethylene promote the defluorination reactions of 1,1,1,2-tetrafluoroethane to generate HF and short chain hydrocarbons, and the number of F atoms in HF molecules accounted for nearly 80 % of the whole reaction system, achieving a better defluorination effect. The defluorination rate of 1,1,1,2-tetrafluoroethane and plastics co-pyrolysis is more than 5 times that of pure 1,1,1,2-tetrafluoroethane pyrolysis. The main co-pyrolysis products of 1,1,1,2-tetrafluoroethane and low-density polyethylene are H 2 , HF and short chain hydrocarbons, the purpose of hydrofluorocarbons degradation into high value-added chemicals and fuels is realized in this study. This work provides a green, effective way for the conversion waste hydrofluorocarbons and waste plastics into high value-added chemicals and fuels, and achieves the conversion of waste hydrofluorocarbon refrigerants to more economical products. • Co-pyrolysis mechanism of hydrofluorocarbons and plastic is first time studied. • Co-pyrolysis process of 1,1,1,2-tetrafluoroethane and low-density polyethylene is described. • Plastic as a hydrogen donor promotes the defluorination of 1,1,1,2-tetrafluoroethane. • HF, H 2 and short chain hydrocarbons rich products could be selectively obtained. • Pyrolysis products of waste hydrofluorocarbons can be enhanced by adding plastics. [ABSTRACT FROM AUTHOR]