Abstract:
Remediation of crude petroleum polluted water for agricultural activities is a challenge.
Kenaf has been found to have potentials for remediation and pelletising it will improve
handling and recovery. Literature is sparse on the appropriate operating parameters for
kenaf pelleting machine. This study was designed to investigate the effects of Screw Pitch
(SP), Speed of Rotation (SR), and Die Diameter (DD), on kenaf pellets properties suitable
for crude oil spill remediation.
A pelleting machine was designed for kenaf using standard procedures. The machine was
evaluated using response surface methodology. The variables were SP (40, 50, 60, 70 and
80 mm), SR (40, 50, 60, 70 and 80 rpm) and DD (27.5, 30.0, 32.5, 35.0 and 37.5 mm).
Thirty experimental combinations were generated from the variables to get responses on
machine efficiency (Pelleting Efficiency (PE) and Percentage Recovery (PR)), pellets’
mechanical properties (Force, Deflection, Energy, Young modulus and Durability Index,
(DI)) and remediation potentials (oil recovered and changes in pH). At different
combinations, the machine was used to pelletise samples of kenaf, starch and water (1:1-
2:3) mixture. Machine efficiency and mechanical properties were determined using ASABE
and Universal Testing Machine. The oil recovered was determined by comparing oil
contents before and after remediation using a spectrophotometer according to AOAC
standards, while changes in pH were determined by comparing pH values before and after
remediation. The process was simulated and optimised using artificial neural network and
its accuracy determined using mean square error (MSE) and coefficient of determination
(R2). Data were analysed using ANOVA at α0.05.
The PE and PR ranged 82.3-95.8% and 68.4-88.3%, respectively. The PE and PR increased
with increase in DD and SR. Forces at peak, yield and break ranged 84-280, 108-342 and
142-504 N, respectively. Deflection at peak and break were 2.01-5.48 and 3.89-10.24 mm,
respectively. Minimal Energy to peak, yield and break were 4.93, 6.75 and 9.42 Nmm/s,
respectively. The Young’s modulus and DI were 0.03 N/mm2 and 98.9 %, respectively. The
SP, DD and SR significantly affected the mechanical properties. Oil recovery ranged
between 97.6 % and 99.8 %, while changes in pH ranged 0.01-0.22, signifying the
occurrence of remediation. Increase in SP and DD yielded an increment in oil removal and
increased changes in pH, while a rise in SR led to a reduction in quantity of oil removed
and an increase in the changes in pH. The MSE and R2 of the models varied between 0.0003
and 125545469.3; 0.2589 and 0.9978, respectively. The optimal operating conditions for
the production of kenaf pellets for remediation were 54 mm SP, 68 rpm SR and 34 mm DD.
Kenaf pellets were good absorbents for remediation of crude oil polluted water bodies.
Optimal conditions for the production of durable kenaf pellets for the effective remediation
of crude petroleum polluted water bodies were established. An efficient pelleting machine
for the production of kenaf pellets was developed.
