Effects of Water Washing and Torrefaction Pretreatments on Corn Stalk Pyrolysis: Combined Study Using TG-FTIR and a Fixed Bed Reactor

Abstract

The washing pretreatment and torrefaction pretreatment of corn stalk were performed in this study. The effects of both separate and combined pretreatments on the pyrolysis were studied using TG-FTIR and a fixed bed reactor. Washing pretreatment had little impact on the physicochemical properties of corn stalk, contributing mainly to the removal of some ash and metallic species. Torrefaction pretreatment, on the contrary, decreased the oxygen content but increased the ash content. TG-FTIR analysis showed that TG/DTG curves of corn stalk (CS), washed corn stalk (W-CS), torrefied corn stalk (T-CS), and torrefied-washed corn stalk (TW-CS), in turn, showed a right shift trend, and the initial decomposition temperatures increased obviously. Among the samples, W-CS had the lowest values of 27.58 and 29.76 wt % for the final residue mass in the TG curve and the biochar yield, respectively, and the highest bio-oil yield of 48.32 wt %, indicating that the removal of metallic species facilitated the pyrolysis of corn stalk and reduced the secondary cracking of pyrolysis volatiles. Moreover, torrefaction pretreatment greatly promoted the generation of combustible gases and phenols of bio-oil, whereas it remarkably reduced the acids of bio-oil. The combination of water washing and torrefaction preserved the advantages of each method on its own, illustrating this combination was a promising pretreatment for improving pyrolysis products.

On the significance of potassium and chlorine content of lignocellulose during torrefaction

“…The standard deviation values for the compositional analysis are also presented in Table 2 Furthermore, it can be concluded that the thermal stability of cellulose in the washed wood sample is raised by about 30 °C, while it is raised by about 50 °C in the hot water washed straw samples compared to the original samples ( Figure 6 d, e, and f). These observations are in accordance with other TG studies where increased thermal stability was observed as a result of washing [34,[36][37].…”

“…The aim of this further work is to clarify the influence of the inorganic ion contents on the thermal degradation process during torrefaction. In the recent years, the effects of combined water washing and torrefaction pretreatments were investigated [34][35][36][37][38]. They found that the water washing prior to torrefaction could effectively remove a large portion of the ash content of the biomass materials and improve the biomass characteristics to a certain extent, which related to the removal of catalytic metals (particularly potassium) by the washing method.…”

Production of Hydrocarbon Fuel Using Two-Step Torrefaction and Fast Pyrolysis of Pine. Part 2: Life-Cycle Carbon Footprint

“…Like other studies, the data used in our simulation shows that the fast pyrolysis of torrefied biomass favors production of biochar. 5,38 A carbon conversion efficiency analysis of the biofuel conversion pathway shows an increase in the carbon conversion from biomass to biochar with increasing torrefaction temperature as shown in Table S9d in section D of the SI. About 63% reduction in GWP was observed for scenario 1 of a two-step production pathway with torrefaction taking place at 330 compared to scenario 1 of a one-step production pathway.…”

Comparison study on pyrolysis characteristics and kinetics of corn stover and its digestate by TG-FTIR

“…As shown in Table 1, the carbon content was increased slightly. The oxygen was decreased noticeably, which is favorable for feedstock that is transformed into high-quality bio-oil with pyrolysis (Cen et al 2016). The crystalline regions of cellulose and the presence of lignin were the main obstacles for the biodegradation of lignocellulose.…”