Parametric study of catalytic co-gasification of cotton stalk and aqueous phase from wheat straw using hydrothermal carbonation

Abstract

Parametric study of catalytic co-gasification of cotton stalk (CS) and aqueous phase from wheat straw (WS-AP) using hydrothermal carbonation (HTC) was conducted to investigate the effects of catalysts, temperature, and flow rate of aqueous phase on the quality and volume of syngas. Olivine (OL), iddingsite (ID), and xiuyan jade (XY) and those calcined for 4 h at 900 °C, namely, C-OL, C-ID, and C-XY, were found to be rich in metal oxides, e.g., MgO (0.24–41.3 wt%), Fe2O3 (6.68–12.4 wt%), and SiO2 (47.8–84.7 wt%), and all of them exhibited a well-developed pore structure. Catalytic co-gasification experiments of ternary blends of CS, WS-AP, and the catalysts were conducted. The addition of six different catalysts improved syngas molar rate (H2/CO). The order by which the catalysts produced H2 yield was C-OL>C-ID>C-XY>ID>OL>XY. C-OL exhibited the highest catalytic behavior with H2 content of 53.6 vol%. The effects of temperature were investigated further. Syngas yield of 1429 mL/g with an H2/CO molar ratio of 2.8 was obtained in the presence of C-OL at 900 °C. Similar results were obtained by decreasing the flow rate of aqueous phase. The maximum syngas yield of 1595 mL was observed in the presence of C-OL at a flow rate of 0.3 mL/min and an H2/CO molar ratio of 2.36. The results confirmed the synergistic effects of CS, WS-AP, and the catalysts due to mineral catalytic effects during co-gasification. This work suggested that C-OL is a potential additive catalyst for handling waste aqueous phase at of co-gasification wastes and for improving syngas quality and yield.