Production of bio oil from jatropha seed by pyrolysis in fixed-bed reactor

BAKHEET, Taiseer Hassan Mohammed, Dr. Ir. Bardi Murachman, SU., DEA

2008 | Tesis | S2 Teknik Kimia

Peningkatan penggunaan bahan baker fosil menyebabkan efek buruk pada iklim global. Disamping itu sumber bahan bakar fosil terbatas jumlahnya. Sehingga riset untuk mencari energi alternatif semakin mendapatkan perhatian, khususnya energi yang dihasilkan dari bio massa seperti jerami, serbuk gergai kayu jati dan sekam padi. Salah satu proses yang bisa digunakan adalah pirolisibahan bakar fosil, potensi economi lain dari bio-oil hasil pirolisis adalah kandungan senyawa didalamnya yang dapat dijadikan sebagai bahan kimia.Bahan baku yang akan diprolisis (fast pyrolysis) adalah serbuk biji jarak (Jatropha curcas). Variabel yang dipelajari adalah diameters serbuk, kecepatan aliran N2 dan suhu. Reaksi dijalankan di dalam reaktor fixed-bed, tanpa hadiranya oksigen pada tekana atomosferik.Hasil penelitian menunjukkan bahwa kenaikan ukuran diameter serbuk biji jarak akan menaikkan yield bio oil dan sebaliknya menurunkan nilai konstnta kecapatan reaksi kimia, sedangkan kenaikan kecapatan alir N2 akan menurunkan baik yield bio oil maupun nilai konstnta kecapatan reaksi kimia.Kenaikan suhu akan menurunkan bio oil dan harga konstnta kecapatan reaksi overall akan naik. Variabe berpengaruh terhadap yeilds adalah kecapatan N2 dan suhu pada 450?C. Perubahan kecapatan alir N2 lebih memberikan pengaruh yang signifikan dari pada perubahan diameter serbuk. Yield bio oil tertinggi yang diperoleh dalam penelitian ini mencapai 46.98% suhu reaktor 450? C, untuk diameter serbuk biji jarak +0.156 –0.344 mm, kecapatan pemanasan rata-rata sebesar 16.5? C/menit dan kecapatan alir N2 45 ml/detik. Nilai kalor bio oil yang diperpleh sebesar 18.954 But/1b. Berdasarkan nilai kalornya, maka dapat disimpulkan bahwa bio oil ini dapat digunakan sebagai pengganti bahan bakar minyak fosil. Model kinetika-2 terdiri dari 3 tahap, yaitu Biomassa menjadi char, bio-oil and gas. Harga konstanta kecapatan reaksi overall rata rata antara suhu 350? C - 450? C kecapatan alir N2 90 ml/detik, ukuran diameter serbuk 0.344 –1.44 mm dan kecapatan pemanasan 16.5? C/detik nilai k1 = 1.876 E0.06 menit-1, k2 = 0.0619 menit-1, k3 = pada kecapatan pemanasan rata rata sebesar 16.5? C/menit. Model kinetika-1 adalah model reaksi tunggal termodifikasi, yaitu Biomassa menjadi Bio-oil, gas and char, merupakan model paling tepat digunakan untuk memprediksi jumlah Bio-oil besarnya harga konstant kecapatan reaksi pada suhu 450? C, kecapatan alir N2 90 ml/detik, diameter serbuk 0.156 – 0.344 mm dan kecapatan pemanasan rata rata 16.5? C/menit k = 0.128 menit-1.

The increasing use of fossil fuel energy creates global climatic effects. Besides, fossil fuel resources are limited. As a result, research in alternative energy is now getting more attention, especially energy that is produced from biomass such as husk, sawdust from teak wood, rapeseed and rice straw. One of the common processes used is pyrolysis. One of pyrolysis product called bio oil that can be used substitution for fossil fuel. Another potential use of bio oil as a product of pyrolysis is its chemical contents which can be used as raw materials for various useful chemicals. Jatropha seeds powder (Jatropha curcas) was used as a raw material. The studied were size of powder, nitrogen flow rate and temperature. Pyrolysis was conducted in fixed bed reactor, under atmospheric pressure with absence of oxygen. The result showed that the increasing of powder diameter would increase bio oil yield and in contrary, it would decrease the value of overall kinetic constant. The increasing of nitrogen flow rate would decrease both bio oil yield and value of overall kinetic constant. The increasing of temperature would decrease bio oil and increasing the value of overall kinetic constant. The effect of changing of nitrogen flow rate was more significant than that of changing of temperature and powder diameter. The maximum bio oil yield of 46.98% was obtained at pyrolysis temperature 450? C, particle size range + 0.156 – 0.344 mm, average heating rate 16.5? C/ minute and nitrogen 45 ml/sec. Gross heating value of bio oil obtained was 18.954 Btu/1b, and net heating value 168.72 Btu/1b. Based on heating value of bio oil, it is concluded that bio oil produced can be used as a replacement of fossil fuel oil. Reaction kinetics-2 model describes three step mechanisms to produce charcoal, bio oil and gases. The average overall rate of reaction constant at temperature between 350 to 450 ? C, nitrogen flow rate 90 ml/sec and particle size 0.344 to 1.44 mm. Heating rate 16.5 ? C/ minute , were found to be k1 =1. 876 E-06 minute-1 , k2 = 0.0619 minute-1, k3 = 2.586 E-07 minute-1. Reaction kinetics-1 model which describes modification of single reaction model to produce bio oil, charcoal and gases was the most appropriate reaction model to predict yield of bio oil product. The value of overall kinetic constant at temperature 450 ? C, nitrogen flow rate 90 ml/sec, particle size range + 0.156 –0.344 mm and heating rate 16.5 ? C/minute was found 0.128 minute-1.

Kata Kunci : Bio oil,Bahan bakar fosil,Pirolisis,Kecepatan alir N2,Pyrolysis, bio oil, kinetics ,fixed-bed ,biomass