Non-equilibrium heat exchange and multi-coupled nature of mass transfer in solvent removal of propellant grains

Abstract

In-depth knowledge of the heat and mass transfer mechanisms in removing the solvent of the propellant grains is crucial for optimizing process conditions as well as obtaining quality products. In this regard, this work developed an industrial-scale fixed bed test system used to study the solvent removal nature of the propellant grains. A transient model for predicting the non-equilibrium heat exchange and the solvent vaporization coupled with the adsorption of the water vapor was proposed as well. Results showed that the developed model could predict the hot air convection of the propellant grains, and the maximum relative deviation of the simulated results and the test data was 9.1%. In addition, the local profiles of the solvents mass fraction in the fixed bed had a non-uniformity in the early stage of the solvent removal, but it tended to be uniform as time went on. The propellant grains in the bottom region of the fixed bed have higher water content than that in other regions at the end of the solvent removal. The temperature of the propellant grains gradually increased due to the convective heat exchange, which led to the thermal non-equilibrium between the hot air and the propellant grains degraded.