Abstract
Corn stover is an abundant and underused source of lignocellulose waste biomass that can be transformed into a high-quality energy resource using hydrothermal carbonization (HTC). This investigation has focused on the effect of processing parameters on the products of HTC—namely solid fuel or hydrochar and liquid and gas fractions. HTC was conducted in a temperature-controlled small batch reactor with corn stover and deionized water under oxygen-free conditions obtained by pressurizing the reactor headspace with nitrogen gas. The properties of the hydrochar and liquid and gas fractions were evaluated as a function of the process temperature (250–350 °C), residence time (30–60 min) and biomass/water ratio (0.09–0.14). Central composite design modules in a response surface methodology were used to optimize processing parameters. The maximum mass yield, energy yield and high heating value (HHV) of the hydrochar produced were 29.91% dry weight (dw), 42.38% dw and 26.03 MJ/kg, respectively. Concentrations of acetic acid and hydrogen gas were 6.93 g/L and 0.25 v/v%, respectively. Experimental results after process optimization were in satisfactory agreement with the predicted HHV. The optimal HTC process parameters were determined to be 305 °C with a 60 min residence time and a biomass/water ratio of 0.114, yielding hydrochar with a HHV of 25.42 MJ/kg. The results confirm the feasibility of an alternative corn stover management system.
Highlights
Biomass is the waste and residual biological material of plants and animals [1]
The ash content of the corn stover hydrochar increases from 18 wt.% of 250 ◦C, 45 min, to 18.95 wt.% of 300 ◦C, 77 min, to 25.87 wt.% of 350 ◦C, 60 min at constant biomass/water ratios of 0.115.The increase in ash content may be caused by reprecipitation of some inorganic material on the solid fuel after a long residence time at high temperatures, as suggested by Kamonwat et al [35]
It was obvious that the hydrochar produced at 384.91 ◦C shows a higher degree of coalification compared to the hydrochars produced at 215.9 ◦C with a similar residence time and biomass/water ratio, which indicated that demethanation, decarboxylation and dehydration reaction occur during the hydrothermal carbonization (HTC) process, though the rate of reaction of decarboxylation was lower than that of the dehydration
Summary
Biomass is the waste and residual biological material of plants and animals [1]. The application of lignocellulose biomass as a sustainable resource has gained traction to achieve a reduction in greenhouse gas emissions [2]. The use of corn stover as a solid fuel feedstock is limited by its low energy density, structural heterogeneity, low heating values and high moisture content. The aims of this investigation are (1) to optimize conditions and determine the effect of process parameters (the biomass/water ratio, residence time and temperature) on the properties of the hydrochar, (2) to gain insight into the underlying mechanism during HTC, as well as the thermal and structural properties of the hydrochar, and (3) to determine the yield and composition of the liquid and gas fractions, and to assess the feasibility of utilizing them in anaerobic digestion in future work
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
