Sains Malaysiana 50(12)(2021): 3705-3717

http://doi.org/10.17576/jsm-2021-5012-20

Carbonization of Coconut Shell Biomass in a Downdraft Reactor: Effect of Temperature on the Charcoal Properties

(Pengkarbonan Biojisim Tempurung Kelapa dalam Reaktor Alir Turun: Kesan Suhu terhadap Sifat Arang)

RABI KABIR AHMAD^1,2* & SHAHARIN ANWAR SULAIMAN¹

¹Department of Mechanical Engineering, Universiti Teknologi PETRONAS, 32610 Bandar Seri Iskandar, Perak Darul Ridzuan, Malaysia

²Department of Agricultural and Environmental Engineering, Bayero University Kano, 3011 Kano, Nigeria

Received: 14 January 2021/Accepted: 18 March 2021

ABSTRACT

Considering the value of coconut shell biomass as renewable fuels in homes and commercial industries, its effectiveness as a biomass resource has been overlooked by our rural citizens and researchers. Carbonization experiments of coconut shell biomass were conducted in a downdraft carbonization reactor (750 mm height and 67 mm diameter) to determine the effect of temperature (250 to 600 °C, in 50 °C intervals) on the charcoal properties. This was to address the problems of traditional charcoal production methods that include; low yield, environmental pollution, unregulated temperature, and poor quality properties. Yet the scarcity of this information hampers efforts for efficient commercial production. The coconut shell biomass was obtained from a local shop in Malaysia. It was heated in the reactor at a fixed residence time of 60 min and a particle size of 5 mm with nitrogen as a carrier gas. The relationship between temperature and the properties of coconut shell charcoal has been ascertained by the findings of this analysis. The relatively high the temperature, the better the charcoal quality, but the lowest the charcoal yields, since the secondary pyrolysis reaction expends charcoal. It was noted that, up to a final temperature of 500 °C, the yield reduction was rapid; after that, it was slower at 550 °C and almost stable at 600 °C. According to the charcoal’s proximate analysis, the calorific value, fixed carbon content, carbon content and ash content increased with temperature. Whereas, the charcoal density, volatile matter, moisture content, and conversion efficiencies decrease with temperature. The presence of nitrogen gas appears to have reduced combustion reactions that promote the formation of carbon dioxide (CO₂). The methods produce the least amount of air pollutants (96 g carbon monoxide (CO), 167 g CO₂, and 64 g methane (CH₄) per 1 kg of charcoal production). The type of biomass and carbonization kiln has an impact on the production of CO, CO₂, and CH₄. Thus, the carbonization reactor used in this study has the potentials to produce an eco-friendly charcoal with superior quality properties that can assist in reducing environmental pollution, by proper selections of carbonization temperature.

Keywords: Charcoal; coconut shell biomass; downdraft reactor; renewable energy; slow pyrolysis; temperature

ABSTRAK

Nilai biojisim tempurung kelapa sebagai bahan bakar yang boleh diperbaharui di rumah dan industri komersial boleh dipertimbangkan, keberkesanan bahan bakar sebagai sumber biojisim ini telah diabaikan oleh masyarakat dan para penyelidik. Kajian tentang proses terhadap biojisim tempurung kelapa dilakukan dalam reaktor alir turun pengkarbonan (ketinggian 750 mm dan diameter 67 mm) untuk menentukan kesan suhu (250 hingga 600 °C, dengan selang 50 °C) pada sifat arang. Kajian ini adalah untuk mengatasi masalah penggunaan kaedah penghasilan arang secara tradisi yang meliputi: hasil rendah, pencemaran alam sekitar, suhu tidak terkawal dan sifat arang yang berkualiti rendah. Namun kekurangan maklumat ini menghalang usaha pengeluaran komersial yang cekap. Biojisim tempurung kelapa diperoleh dari sebuah kedai tempatan di Malaysia. Ia dipanaskan di reaktor pada masa mastautin selama 60 min dan ukuran zarah 5 mm dengan nitrogen sebagai gas pembawa. Hubungan antara suhu dan sifat arang tempurung kelapa telah ditentukan daripada penemuan analisis kajian ini. Secara relatif, semakin tinggi suhu semakin baik kualiti arang, tetapi arang yang dihasilkan adalah sedikit, ini kerana reaksi pirolisis sekunder mengembangkan arang. Telah diperhatikan bahawa, hingga suhu akhir 500 °C, jmlah penurunan arang adalah cepat; selepas itu, ia menjadi perlahan apabila suhu pada 550 °C dan hampir stabil pada 600 °C. Menurut analisis proksimat arang, nilai kalori, kandungan karbon tetap, kandungan karbon dan kandungan abu meningkat dengan suhu. Manakala kepadatan arang, bahan mudah meruap, kandungan kelembapan dan kecekapan penukaran menurun dengan suhu. Kehadiran gas nitrogen menunjukkan pengurangan tindak balas pembakaran yang mendorong pembentukan karbon dioksida (CO₂). Kaedah yang menghasilkan jumlah pencemaran udara paling sedikit (96 g karbon monoksida (CO), 167 g CO₂ dan 64 g metana (CH₄) setiap 1 kg penghasilan arang). Jenis biojisim dan tanur pengkarbonan memberi kesan terhadap pengeluaran CO, CO₂ dan CH₄. Oleh itu, reaktor pengkarbonan yang digunakan dalam kajian ini berpotensi untuk menghasilkan arang mesra alam dengan sifat kualiti yang lebih tinggi serta dapat membantu mengurangkan pencemaran alam sekitar dengan pemilihan suhu pengkarbonan yang tepat.

Kata kunci: Arang; biojisim tempurung kelapa; pirolisis perlahan; reaktor alir turun; suhu; tenaga yang boleh diperbaharui

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*Corresponding author; email: rkahmad.age@buk.edu.ng