Insight into the thermal conversion of corn stalk gasification in supercritical water based on reactive molecular dynamics simulations

Abstract

Supercritical water gasification (SCWG) technology could be used for the clean and efficient utilization of waste biomass. This work first constructed a three-dimensional macromolecular model based on the characteristics of real corn stalks (CS). The reactive force field molecular dynamics (ReaxFF MD) method was then employed to study the gasification process in supercritical water. The depolymerization process of CS in SCW was observed by tracing the evolution of the carbon-containing products during the reaction. Temperature and water concentration effects on the SCWG of CS were analyzed. The results indicated that higher temperature caused more water to decompose into hydrogen and hydroxyl radicals. Meanwhile, the large number of reactive radicals favored the production of gases such as HCHO, CH4, CO, and H2. In addition, HCHO, CH4, and CO2 would continue to hydrolyze or decompose at high temperature to produce small molecule gases such as CO and H2. Furthermore, water-gas conversion and steam-reforming reactions would occur more frequently when the water concentration was higher. As a result, higher gasification rates and higher hydrogen yields were achieved.