Doctoral Theses

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Browsing Doctoral Theses by Author "Kazawadi, D."

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    Co-production of adsorbent biochar andbio-oil fuel from cashew nut shells: a modeling and optimization study of intermediate pyrolysis process
    (The University of Dodoma, 2023) Kazawadi, D.
    Intermediate pyrolysis (IP) is an effective method in handling bio-wastes and in co-production ofadsorbent biochar (AB) and bio-oil fuel (BO). Cashew nut shells (CNS) are regarded as a bio-waste in Tanzania, but has faced inadequate and poor handling. This study focused on modeling and optimizing the IP process for co-production of AB and BO from CNS. The study modeled and optimized IP process using four parameters namely; particle size (1-10 mm), heating rate (1-10 °C/min), residence time (20-60 min), and temperature (400-600 °C). Furthermore, co-produced ABand BO were upgraded using chemical activation and atmospheric distillation, respectively. This study reported the model equations and optimum parameters of IP process for CNS and the comparison between co-products and their respective commercial products. Optimal IP parameters were 1-1.7 mm, 2.03 °C/min, 22 minutes, and 470 °C, for particle size, heating rate, residence time, and temperature, respectively. Gold adsorption capacity of biochar, which was regarded as AB,was found to 1.9 mg/g while bio-oil organic phase (BOP) which was regarded as bio-oil fuel (BO) had 27 MJ/kg heating value and 2.7% water content. Optimal distillation occurred at 293°C, producing an oil phase with 36 MJ/kg, 10 mm2/s viscosity, and 0.984 g/cc density. Chemical activation of AB increased gold adsorption from 1.9 mg/g to 3.1 mg/g. The investigation found that the co-products produced had physio-chemical properties unlike those of commercial products. Further research is recommended to expand the scope of IP studies by exploring additional parameters and investigating different bio-wastes. In addition, the upgrading of BO should be tested on alternative techniques like vacuum distillation. Furthermore, conducting an economic analysis is crucial to assess the commercial viability of the process.