Compressive mechanical cracking of pili (Canarium ovatum Engl.) nuts: Concept and mechanism design

A mechanical pili nut cracker that used gradual compression for cracking was proposed and developed. This was a deviation from the traditional practice of applying impact for cracking pili nuts. The cracking unit of the machine accomplishes gradual compression by a rotating assembly of discs and compression bars travelling along an arrangement of cam rails. The cracker’s performance was established using pili nuts at different moisture levels.  The tests followed a single-factor three-level experiment where the response variables included cracking capacity, cracking efficiency, cracking recovery, whole kernel recovery, kernel damage, kernel losses and purity of output. The machine performed satisfactorily using nuts dried for three days after depulping (moisture content wet basis = 11.6%). At this moisture level, the machine showed consistent and satisfactory performance in terms of cracking capacity (25 kernels min-1), cracking efficiency (74.0%), cracking recovery (62.6%) and whole kernel recovery (84.3%). Modifications were recommended to further reduce kernel damage (30.6%) and kernel losses (37.4%) and to improve the purity of output (46.8%). It was successfully demonstrated that gradual compression can be used for cracking pili nuts. It is recommended that the operating characteristics of the machine should be optimized to improve its performance.  Furthermore, a dedicated feeding assembly and a more suitable separation method should be explored to further enhance the performance of the cracker

Biorefining of pigeon pea:Residue conversion by pyrolysis

Pyrolysis is an important technology to convert lignocellulosic biomass to a renewable liquid energy carrier known as pyrolysis oil or bio-oil. Herein we report the pyrolysis of pigeon pea wood, a widely available biomass in the Philippines, in a semi-continuous reactor at gram scale. The effects of process conditions such as temperature (400-600 ◦C), nitrogen flow rate (7-15 mL min−1) and particle size of the biomass feed (0.5-1.3 mm) on the product yields were determined. A Box-Behnken three-level, three-factor fractional factorial design was carried out to establish process-product yield relations. Of particular interest is the liquid product (bio-oil), of which the yield was shown to depend on all independent variables in a complex manner. The optimal conditions for highest bio-oil yield (54 wt.% on dry feed intake) were a temperature of 466 ◦C, a nitrogen flow rate of 14 mL min−1 and a particle size of 1.3 mm. Validation of the optimized conditions proved that the average (n = 3) experimental bio-oil yield (52 wt.%) is in good agreement with the predicted value from the model. The properties of product oils were determined using various analytical techniques including gas chromatography-mass spectrometry (GC-MS), gel-permeation chromatography (GPC), nuclear magnetic resonance spectroscopy (13C- and HSQC-NMR) and elemental and proximate analyses. The bio-oils were shown to have low ash content (0.2%), high heating value (29 MJ kg−1) and contain high value-added phenolics compounds (41%, GC peak area) as well as low molecular weight aldehydes and carboxylic acids. GPC analysis indicated the presence of a considerable amount of higher molecular weight compounds. NMR measurements showed that a large proportion of bio-oil contains aliphatic carbons (~60%), likely formed from the decomposition of (hemi)cellulose components, which are abundantly present in the starting pigeon pea wood. Subsequent preliminary scale-up pyrolysis experiments in a fluidized bed reactor (~100 gfeed h−1, 475 ◦C and N2 flow rate of 1.5 L min−1) gave a non-optimized bio-oil yield of 44 wt.%. Further fractionation and/or processing are required to upgrade these bio-oils to biofuels and biobased chemicals