Energy Efficient Process Designs for Acrylonitrile Production by Propylene Ammoxidation

Acrylonitrile is a critical commodity chemical used to produce a variety of industrial polymers, such as carbon fibers, plastics, etc. Currently 90% of the global acrylonitrile production is based on propylene ammoxidation. However, there is no literature reporting the whole process holistically in detail, and which also looks into the energy utilization of the whole process including the reaction heat as well as the energy demands of the downstream separation. This original study provides a rigorous process design of the full process from a holistic viewpoint, covering 7 sections of acrylonitrile production (reaction, acid quenching, absorption-desorption, hydrogen cyanide recovery, acrolein recovery, acrylonitrile-acetonitrile-water separation, acetonitrile recovery sections). In order to further improve the energy efficiency, three energy integration strategies are proposed (1) Energy integrated downstream processing; (2) Systematic heat integration utilizing the heat of reaction; (3) Power generation by process surplus heat. Design 1 employs a direct heat exchanger network, recovering 30.1 MW heat through multiple heat exchanges, saving 86.91% fuel gas, 17.38% low pressure steam and 43.96% cooling utilities. Design 2 and 3 recovers 58.39 MW heat, and 12.20 MW low pressure steam is output as waste heat recovery in design 2, whereas 11.06 MW low pressure steam and 7.8 MW electricity are generated in design 3. The pro/con each options are also discussed for further guidance. As the first comprehensive description of the design of the entire acrylonitrile production process, this work highlights the potential for improved energy efficiency in the acrylonitrile production.