Gas Emission Study of the Polyacrylonitrile-Based Continuous Pilot-Scale Carbon Fiber Manufacturing Process

Environmental impacts of carbon fiber production and decarbonization performance in wind turbine blades

The application of carbon fiber in the wind power industry is of great interest in declining CO2 emissions but the carbon fiber manufacturing process is still a long way heading cleaner production. Since little to no information clarifies the dual effects from carbon fiber production to application, this study carried out a life cycle assessment (LCA) to recognize the environmental performances of polyacrylonitrile (PAN)-based carbon fiber production and explore the decarbonization effects of carbon fiber application in wind turbine blades. Based on on-site data from a leading carbon fiber production chain in China, potential environmental impacts of carbon fiber production predominantly originated from the precursor spinning stage (accounted for 13-91%). Fossil depletion (20.24 kg oil eq.), climate change (67.79 kg CO2 eq.), terrestrial ecotoxicity (165.63 kg 1,4-DCB eq.) and photochemical ozone formation (0.14 kg NOx eq.) were the four noteworthy areas to improve the sustainable development. Different scenarios in energy and advanced technology were set to explore the potential improvement of the environmental performance of carbon fiber products. Energy structure (wind power) can improve an average of 22.58% environmental benefit compared with the background scenarios. Regarding the decarbonization effects, the energy payback time and the carbon payback time were estimated to be 0.73 and 0.37 months respectively. Therefore, carbon fiber is a trustworthy material in the strategy to achieve sustainable development from a life cycle perspective.

Insights into the carbonization mechanism of PAN-derived carbon precursor fibers and establishment of a kinetics-driven accelerated reaction template for atomistic simulation

To better understand the chemistry behind the carbonization process of the polyacrylonitrile (PAN)-based precursor fibers and provide a more authentic virtual counterpart of the process-inherited model for process optimization and rational performance design, we develop arrow-pushing reaction routes for primary exhaust gas product (H₂O/H₂/HCN/N₂/tar vapor) formation and a pragmatic kinetics-driven accelerated reaction template for atomistic simulation of the carbonization process overcoming traditional challenges in time scale discrepancy of the reaction-diffusion system. The results of enthalpy barriers from hybrid first principles calculations validate the rationality and sequence of conjectured reactions during the two-stage carbonization process. Conversion rates of the rate-determining steps under 300 s carbonization are also estimated based on Eyring's transition state theory realizing kinetics equivalency of the reaction extent. Process-control measurements are further demonstrated corresponding to the proposed mechanism. The iterative densified crosslinking scheme specially designed for the surface layer is implanted into the topological reaction molecular dynamics template and a series of highly devisable structural models during the whole evolutionary process from the pre-oxidized fiber to the pristine carbon fiber surface are successfully predicted. The ultimate structure of the model presents excellent similarity in carbon yield and elemental composition with the type II high strength carbon fiber surface.

A high-flux antibacterial poly(amidoxime)-polyacrylonitrile blend membrane for highly efficient uranium extraction from seawater

Uranium is an important fuel for nuclear power, with 4.5 billion tons of it stored in the oceans, 1,000 times more than on land. Polymer membrane materials are widely used in the marine resources fields, due to their convenient collection, good separation and can work continuously. Herein, a poly(amidoxime)-polyacrylonitrile blend membrane (PCP) with high flux, excellent antibacterial properties and uranium adsorption performance has been prepared by using the phase inversion method, and the prepared membrane was used for highly efficient uranium extraction from seawater. In static adsorption experiments, the PCP membrane reached adsorption equilibrium after 48 h, and the adsorption capacity was 303.89 mg/g (C₀ =50 mg/L). In dynamic adsorption experiments, it was found that the lower flow rate and higher number of membrane layers were favorable for dynamic adsorption. In addition, the water flux of the PCP membrane was 7.4 times higher than that of the PAN membrane. The adsorption mechanism can be attributed to the chelation between amino and hydroxyl groups in CS, amidoxime group in poly(amidoxime) and uranyl ions. The simple preparation process coupled with the excellent adsorption performance indicated that the PCP membrane would be a promising material for the uranium extraction from seawater.