To realize the energy recovery of wheat straw, the pyrolysis behavior of wheat straw was studied at three heating rates (10, 20, and 30 K/min) based on thermogravimetric analysis (TG–DTG). Kinetics and thermodynamics were analyzed using Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) model-free methods, and the reaction mechanism was determined using the Coats–Redfern (CR) model-fitting method. The results show that there are three weightlessness stages in the pyrolysis process, of which the second stage was the main weightlessness stage and two distinct peaks of weightlessness were observed in this stage. With increasing heating rate, the main pyrolytic weightlessness peaks of the DTG curve shift to the high-temperature side. The pyrolysis activation energies calculated by the FWO and KAS methods are 165.17–440.02 kJ/mol and 163.72–452.07 kJ/mol, and the pre-exponential factors vary in the range of 2.58 × 10¹²–7.45 × 10³⁶ s⁻¹ and 1.91 × 10¹²–8.66 × 10³⁷ s⁻¹, respectively. The thermodynamic parameters indicate that wheat straw has favorable conditions for product formation and it is a promising feedstock. Its pyrolysis reaction was nonspontaneous and the energy output is stable. CR method analysis shows that the A_1/3 random nucleation model is the most suitable mechanism to characterize the pyrolysis process and random nucleation may be in charge of the main pyrolysis stage. This study can provide a theoretical basis for the thermochemical conversion and utilization of wheat straw.

As a typical forestry waste, bamboo has gained increasing attention for its potential applications. In order to optimize its valorization, understanding the kinetic and thermodynamic parameters of bamboo pyrolysis and combustion is crucial. In this study, thermogravimetric analysis (TGA) was employed to examine bamboo powder’s pyrolysis and combustion behaviors under different temperature ramps in nitrogen and air environments, and the kinetic and thermodynamic parameters were evaluated using the Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Starink (STR) model-free approaches. The main findings are as follows. (1) The thermogravimetry (TG) and derivative thermogravimetry (DTG) (DTG) curves reveal that bamboo pyrolysis occurs in three distinct stages: drying, devolatilization, and carbonization. Similarly, combustion also proceeds through three stages: drying, devolatilization, and char combustion. Notable differences in the temperature ranges of the key stages were observed between pyrolysis and combustion. (2) The activation energies during the oxidative devolatilization stage of combustion are notably lower compared to those during pyrolysis devolatilization. The disparity in activation energy is even more pronounced in the third stage. (3) Thermodynamic analysis shows that the pyrolysis and combustion of bamboo are endothermic and non-spontaneous. It can be stably converted into value-added energy through the pyrolysis or combustion process. This study provides essential data to aid in designing and scaling up the thermochemical conversion processes for bamboo and promote its efficient valorization of bioenergy.

To realize the utilization of peanut shell, this study investigates the combustion behavior, chemical kinetics and thermodynamic parameters of peanut shell using TGA under atmospheric air at the heating rates of 10, 20, and 30 K/min. Results indicate that increasing the heating rate leads to higher ignition, burnout, and peak temperatures, as observed in the TG/DTG curves shifting to the right. Analysis of combustion performance parameters suggest that higher heating rates can enhance combustion performances. Kinetic analysis using two model-free methods, KAS and FWO, shows that the activation energy (E_α) ranges from 93.30 to 109.65 kJ/mol for FWO and 89.72 to 103.88 kJ/mol for KAS. The data fit well with coefficient of determination values (R²) close to 1 and the mean squared error values (MSE) less than 0.006. Pre-exponential factors using FWO range from 2.19 × 10⁶ to 8.08 × 10⁷ s⁻¹, and for KAS range from 9.72 × 10⁵ to 2.25 × 10⁷ s⁻¹. Thermodynamic analysis indicates a low-energy barrier (≤±6 kJ/mol) between activation energy and enthalpy changes, suggesting easy reaction initiation. Furthermore, variations in enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS) upon conversion (α) suggest that peanut shell combustion is endothermic and non-spontaneous, with the generation of more homogeneous or well-ordered products as combustion progresses. These findings offer a theoretical basis and data support for the further utilization of agricultural biomass.

As a typical biomass resource, peanut shell has the potential to produce energy and value-added products, as it is generated abundantly worldwide. Pyrolysis is increasingly utilized for the disposal of biomass wastes through thermal conversion into chemical raw materials. Assessing the pyrolysis kinetics, reaction mechanism, thermodynamic parameters for individual components of peanut shells is crucial for its valorization. In this study, conditions for pyrolysis were optimized under pure N₂ flow across temperatures ranging from 303 K to 1173 K at the temperature ramp of 10 K/min, 20 K/min, and 30 K/min. The peak-differentiating analysis using Gaussian function was employed to segregate the pyrolysis of peanut shell into several independent one-step parallel reactions, corresponding to pseudo-lignin, pseudo-cellulose, and pseudo-hemicellulose decomposition. The Coats-Redfern, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, and Vyazovkin techniques were employed to estimate kinetic parameters and reaction mechanism for each pseudo-component of peanut shell. The performed analyses revealed that the average activation energy values generally followed an order of pseudo-lignin > pseudo-hemicellulose > pseudo-cellulose, with values of 174.31 kJ/mol, 133.89 kJ/mol, and 115.44 kJ/mol by Kissinger-Akahira-Sunose, 177.79 kJ/mol, 136.53 kJ/mol, and 120.33 kJ/mol by Flynn-Wall-Ozawa, and 174.96 kJ/mol, 134.29 kJ/mol, and 116.61 kJ/mol by Vyazoykin, respectively. The Coats-Redfern method indicated that the suitable mechanism of reaction for pseudo-hemicellulose and pseudo-cellulose were random nucleation-based, while diffusional-based mechanism was identified for pseudo-lignin. The thermodynamic analysis revealed that the decomposition of peanut shell was endothermic and non-spontaneous, and it can be converted into value-added sources of energy steadily through pyrolysis process. This study offers a reliable approximation of experimental data irrespective of pyrolysis behavior and guides the resourceful utilization of peanut shell.

In this paper, steel slag powder was used to replace part of the cement in road concrete, and group tests were carried out on coarse aggregates with different water–cement (W/C) ratios, different steel slag parameters, and different particle sizes. A sample of 100 mm × 100 mm × 100 mm was prepared and cured for 3 days, 7 days, and 28 days. In addition, the fluidity and compressive properties of the samples were also tested. The outcomes of this study revealed that, at a constant W/C ratio, increasing the proportion of steel slag improved the concrete’s fluidity but reduced its compressive strength; the 3-day (3 d) compressive strength of 40% steel slag was lower because the early activity of steel slag was lower than that of cement; steel slag also decreased the early-hydration rate of concrete. Comparisons across different W/C ratios demonstrated that steel slag made a more significant contribution to lower W/C ratios than higher ones. The water requirement for steel slag was relatively moderate, and the compressive strength of steel slag concrete with a high W/C ratio notably improved in the later stages. Based on the experimental conditions, the optimal content of steel slag was found to be 35%. Reusing steel slag as a replacement for sand in coarse aggregate can effectively lower costs and offer an innovative approach to steel slag treatment.