Torrefaction of Agricultural Residues: Effect of Temperature and Residence Time on the Process Products Properties

Abstract

To date, few studies on the potential utilization of agricultural residue torrefaction products have been performed. Thus, torrefaction product characterization aimed at its potential utilization was performed. Wheat-barley straw pellets and wheat-rye chaff were used in the study. The impact of the torrefaction temperature (280-320°C) on polycyclic aromatic hydrocarbons (PAHs) content in the biochar and noncondensable gas (noncondensables) composition was investigated. The impact of the torrefaction time (30-75 min) on the composition of the condensable volatiles (condensables) and their toxicity were also studied. The torrefaction process was performed in a batch-scale reactor. The PAH contents were measured using high-performance liquid chromatography (HPLC), and the noncondensables composition was measured online using a gas analyzer and then gas chromatograph with flame ionization detector (GC-FID). The condensables composition and main compound quantification were determined and quantified using gas chromatography-mass spectrometry (GC/MS). Three toxicity tests, for saltwater bacteria (Microtox ® bioassay), freshwater crustaceans (Daphtoxkit F magna ® ), and vascular plants (Lemna sp. growth inhibition test), were performed for the condensables. The PAHs content in the biochar, regardless of the torrefaction temperature, allows them to be used in agriculture. The produced torgas shall be co-combusted with full-caloric fuel because of its low calorific value. Toxic compounds (furans and phenols) were identified in the condensable samples, and regardless of the processing time, the condensables were classified as highly toxic. Therefore, they can be used either as pesticides or as an anaerobic digestion substrate after their detoxification.

Torrefaction as a Pretreatment Technology for Chlorine Elimination from Biomass: A Case Study Using Eucalyptus globulus Labill

“…The temperature attained and its duration influence the degree of thermal degradation. Regarding residence time, previous studies commented the importance of replacing this term with reaction time since the former mainly influences the degradation of hemicellulose, while the latter affects the cellulose mass loss [65,66]. As mentioned, the torrefaction process has several heating stages, even before torrefaction starts.…”

Synergetic Co-Production of Beer Colouring Agent and Solid Fuel from Brewers’ Spent Grain in the Circular Economy Perspective

“…The performance of the torrefaction process is typically determined directly using mass yield (Y m ) and energy yield (Y e ) [83][84][85][86]. The indirect method was proposed by Weber et al for simple assessment of performance of thermal biomass valorisation processes, such as production of biochar [87].…”

Torrefaction: Process Parameters and Reactor Design

“…Torrefaction of agricultural residues (wheat-barley straw pellets and wheat-rye chaff) was examined in the study of Jagodzińska et al [16], with the emphasis on temperature and retention time effects on the properties of final products. With temperature increase from 210 to 260 °C, the content of biochar and condensable compounds expanded.…”