The updraft gasifier is a simple type of reactor for the gasification of biomass that is easy to operate and has high conversion efficiency, although it produces high levels of tar. This study attempts to observe the performance of a modified updraft gasifier. A modified updraft gasifier that recirculates the pyrolysis gases from drying zone back to the combustion zone and gas outlet at reduction zone was used. In this study, the level of pyrolysis gases that returned to the combustion zone was varied, and as well as measurements of gas composition, lower heating value and tar content. The results showed that an increase in the amount of pyrolysis gases that returned to the combustion zone resulted in a decrease in the amount of tar produced. An increase in the amount of recirculated gases tended to increase the concentrations of H2and CH4and reduce the concentration of CO with the primary (gasification) air flow held constant. Increasing the primary air flow tended to increase the amount of CO and decrease the amount of H2. The maximum of lower heating value was 4.9 MJ/m3.

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Utilization of MSW as solid fuel has been developed through the process of gasification and pyrolysis. To improve energy efficiency during combustion, it needs uniformity of form and compaction, therefore MSW is formed in the form of pellets. The purpose of this research was to determine the physical characteristics of MSW pellets with the addition of binder and pellet drying process. Pellets consist of organic material, plastic, paper and leaves which are dried and crushed to reduce size. The material is mixed with the tapioca flour binder content of 0%, 3% and 6% and then compacted in the form of pellets. After the milling process, the pellets are dried with a treatment of 0, 6 and 12 hours to measure physical characteristics, moisture content and caloric value. Physical measurements consist of tests of density, durability and hardness. The developed pellet had a size length of 23.6 – 24 mm and diameter of 7.8-8.2 mm and 1.16-1.36 grams of weight the individual pellet. From the results of measurements and observations, pellets with 0% binder adding and 12-hours of drying can produce better quality, in the absence of fungal contamination and have a higher caloric value. MSW pellets from that process have achieved European pellet standards for physical properties, moisture content and caloric value.

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ABSTRAKDengan menipisnya cadangan minyak dunia dan masalah lingkungan yang diakibatkan oleh pembakaran bahan bakar fossil, maka diperlukan energi alternatif dalam mengatasi hal tersebut. Bahan bakar gas dari proses gasifikasi biomassa (producer gas) adalah salah satu energi alternatif yang dapat menggantikan bahan bakar fosil. Pemanfaatan producer gas untuk aplikasi pengeringan dan pemanasan boiler memerlukan suatu sistem gas burner yang dapat menghasilkan panas tinggi dan polusi rendah. Pada penelitian ini sebuah model gas burner berbahan bakar producer gas dilakukan pemodelan simulasi secara 3D menggunakan CFD. Simulasi dilakukan dengan menggunakan swirl gas burner dengan menggunakan conical flame stabilizer dan tanpa menggunakan conical flame stabilizer pada variasi kecepatan udara masuk tangensial 3 m/s, 6 m/s dan 9 m/s. Hasil simulasi menunjukkan penambahan conical flame stabilizer menghasilkan api yang lebih pendek dan stabil. Penambahan kecepatan udara memendekkan panjang api dan menurunkan temperatur api. Validasi eksperimental dilakukan pada gas swirl burner yang menggunakan conical flame stabilizer. Simulasi dan eksperiment menunjukkan hasil yang tidak jauh berbeda.Kata kunci: CFD, producer gas, gas burner, conical flame stabilizer. ABSTRACTThe depletion of worlwide energy reservation and environmental issue caused by fossil fuel pollution urge mankind to find a suitable alternative energy to overcome this problem. Producer gas from biomass gasification is an example of an alternative energy that could substitute fossil fuel in a certain combustion operation. Using producer gas to generate heat needs gas burner system that can produce an effective gas flame with low emission gas. This study is using modeling and simulation of gas flame using 3D-CFD method. The gas burner model has two condition, namely, using conical flame stabilizer and without conical flame stabilizer, and the velocity tangential air supply is varied into three speed of 3 m/s, 6 m/s and 9 m/s, respectively. The result of this simulation shows the additional of conical flame stabilizer produces a shorter flame, increases flames stability and reduces CO emission. The experimental result shows a similar pattern compared with that of the simulation result.