Physical and mechanical characteristics of composite briquette from coal and pretreated wood fines

Abstract

Melina wood torrefied at 260 °C for 60 min was agglomerated with lean grade coal fines into composite briquettes using pitch as binder. Torrefied biomass (3%–20%) and coal fines (80%–97%) were blended together to produce the composite briquettes under a hydraulic press (28 MPa). The briquettes were cured at 300 °C. Density, water resistance, drop to fracture, impact resistance, and cold crushing strength were evaluated for the composite briquettes. The proximate, ultimate, and calorific value analyses were carried out according to different ASTM standards. Microstructural studies were carried out using scanning electron microscope and electron probe microanalyzer equipped with energy dispersive x-ray. Fourier Transform Infrared Spectrophotometer (FTIR) was used to obtain the functional groups in the raw materials and briquettes. The density of the composite briquettes ranged from 0.92 to 1.31 g/cm3 after curing. Briquettes with < 10% torrefied biomass has good water resistance index (> 95%). The highest cold crushing strength of 4 MPa was obtained for briquettes produced from 97% coal fines and 3% torrefied biomass. The highest drop to fracture (54 times/2 m) and impact resistance index (1350) were obtained for the sample produced from 97% coal and 3% torrefied biomass. The fixed and elemental carbons of the briquettes showed a mild improvement compared to the raw coal. The peaks from FTIR spectra for the briquettes shows the presence of aromatic C=C bonds and phenolic OH group. The composite briquettes with up to 20% torrefied biomass can all be useful as fuel for various applications.

Briquetting of subbituminous coal and torrefied biomass using bentonite as inorganic binder

“…This is expected as unbounded moisture loss, light volatiles evolution and reactive drying takes placed at 300 24 . The density of the briquettes produced in this study is a little higher than our previous studies 1 , 2 . This is because of the addition of bentonite, which is denser than the binders (molasses and pitch) used in those studies.…”

“…Further drying was done in an oven at 105 for 30 min to eliminate unbounded moisture as previously described by Adeleke et al 1 . The proximate, ultimate and calorific value (HHV) as reported by Adeleke et al 2 are shown in Table 1 . The details of torrefaction of melina has also been reported by Odusote et al 7 .…”

“…The reactivity of the briquette samples was carried out in accordance with ASTM D5341M-14 standard 20 . The details of this method have been reported in our previous study 2 . The RI was obtained in duplicates for each sample.…”

“…Wastes from coal mining, handling and transportation are always in million tonnes 1 . Coal fines (< 3 mm) are often referred to as wastes and are inevitably produced when lump coals are processed or handled 2 , 3 . Wastes from the wood processing industries have also been reported to be in million tonnes especially in developing countries 4 , 5 .…”

“…The best briquette produced was reported to have a compressive strength of 13.06 MPa with a drop to fracture of 56.6 time/2 m. The briquettes were primarily produced for COREX iron making processes. Adeleke et al 2 produced and characterized composite briquettes from coal and wood fines using pitch binder. The wood fines were initially torrefied for an improved calorific value and enactment of its bonding properties.…”