Gaofeng Chen

Torrefaction used for the pretreatment of biomass can enhance grindability along with a significant reduction of energy consumption required for pulverization to aid in large-scale utilization of biomass energy. In this study, torrefaction experiments of wheat straw were conducted at different temperatures using an experimental furnace facility. The influence of torrefaction temperature on the grindability of resulting wheat straw was explored using a hardgrove grindability index tester and thermogravimetric-Fourier transform infrared (TG-FTIR) spectroscopy. The results indicated that an increase in torrefaction temperature significantly increased the carbon content of wheat straw and decreased the oxygen content to result in a decrease in the O/C ratio from 0.66 to 0.39. The calorific value increased by 24% from 15.42 MJ/kg to 19.17 MJ/kg. An increase in torrefaction temperature from 220 °C to 269 °C increased the grindability index from 29 to 115. The grindability of wheat straw can be controlled to values similar to that of coal by tuning the torrefaction temperature. The main gas components released during torrefaction were H2O, CH4, CO2, and CO. Thermogravimetric data showed 29% solid residues from the raw wheat straw. An increase in torrefaction temperature increased solid residue to 41%. The pyrolysis of wheat straw at different torrefaction temperatures can be grouped into three stages such as dehydration, rapid pyrolysis, and carbonization. This study reveals effective large-scale utilization of wheat straw biomass as a high heating value solid fuel using torrefaction pretreatment.

Continued social and mobility development has caused a sharp increase in the number of waste tires, increased environmental pollution, and waste of limited resources. Agricultural residues as a bioresource, which has drawn increased attention in recent years. The thermochemical conversion of waste tires and agricultural residues and their mixtures offers important prospects for scientific development, which can provide energy security and a much reduced environmental footprint. In this paper, pyrolysis of waste tires and its co-pyrolysis with maize stalk, wheat straw, cotton stalk, rape straw, or peanut shell agricultural residues, in mass ratios of 1:1 were investigated at different heating rate using thermogravimetric analysis. The kinetic parameters were calculated using Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) kinetic models at heating rates of 20, 30, and 50 °C/min. The synergistic effect between waste tires and agricultural residues was explored by calculating the deviation between the experimental and calculated values. The results showed the presence of a synergistic effect between the co-pyrolysis of waste tires and the residual agricultural residues. In the kinetic analysis, activation energies of waste tires, agricultural residues, and their mixtures were calculated using the two models. The reaction followed a multistage reaction mechanism. The differential thermogravimetry behavior of the mixture was similar to the weighted aggregate results of the waste tire and agricultural waste samples, pyrolyzed separately. These results provide some insights into the combined treatment of waste tires and agricultural waste residues.

The co-thermal chemical conversion of biomass and waste tires is an important direction for the utilization of waste resources to produce renewable energy. In this study, the product distribution and synergistic effects during the co-pyrolysis of agricultural residues and waste tire were analyzed by a pyrolyzer coupled with a gas chromatograph/mass spectrometer (Py-GC/MS). Pyrolysis and co-pyrolysis products were analyzed at 550 °C and 650 °C for maize stalk (MS), wheat straw (WS), waste tire (WT) feedstocks, as well as mixtures of wheat straw-waste tire (WS:WT mass ratio of 1:1), and maize stalk-waste tire (MS:WT mass ratio of 1:1). The results showed that the co-pyrolysis of agricultural residues and waste tire promoted the release of phenols, aldehydes, and ketone derivatives, and reduced the formation of H2 and H2O. In addition, a relatively high content of aromatic hydrocarbons was obtained at 650 °C temperature, while 550 °C was optimal when considering the formation of ketones. The results showed a synergistic effect in the co-pyrolysis of biomass and waste tire.