Analisis Pengaruh Variasi Rasio Co-Firing Torrefied Sawdust terhadap Karakteristik Pembakaran dan Spesies Gas pada Furnace PLTU 315 MW

Fhadila, Yeyen Nur (2026) Analisis Pengaruh Variasi Rasio Co-Firing Torrefied Sawdust terhadap Karakteristik Pembakaran dan Spesies Gas pada Furnace PLTU 315 MW. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Pembangkit Listrik Tenaga Uap (PLTU) masih mendominasi bauran energi listrik nasional sebesar 61%. Sebagai upaya transisi energi dan penurunan emisi karbon, co-firing biomassa hasil torefaksi (torrefied sawdust) diimplementasikan pada PLTU, namun penentuan rasio pencampuran optimalnya memerlukan kajian mendalam. Penelitian ini bertujuan untuk menganalisis pengaruh variasi rasio co-firing torrefied sawdust sebesar 12%, 16%, dan 20% terhadap karakteristik pembakaran, yang meliputi distribusi temperatur (fireball dan Furnace Exit Gas Temperature/FEGT), serta distribusi spesies gas hasil pembakaran (O₂, CO₂, H₂O, SO₂, CO) pada furnace PLTU 315 MW. Metode yang digunakan adalah simulasi numerik 3D Computational Fluid Dynamics (CFD) menggunakan perangkat lunak ANSYS Fluent pada kondisi steady state dengan mempertahankan excess air ratio konstan. Hasil simulasi menunjukkan bahwa tingginya kadar volatile matter pada torrefied sawdust memicu fenomena flash combustion di elevasi bawah furnace. Hal ini menyebabkan penyusutan volume fireball dan penurunan signifikan nilai FEGT dari 1121,9°C (100% batu bara) menjadi 1072,2°C (12%), 998°C (16%), hingga 931°C (20%). Pada aspek spesies gas, co-firing terbukti efektif menurunkan fraksi mol CO₂ dari 11,34% menjadi 9,75% (pada rasio 20%) akibat lebih rendahnya pasokan unsur karbon total dari biomassa. Adapun fraksi mol H₂O menurun dari 9,62% menjadi 6,80% seiring dengan sangat rendahnya kadar moisture biomassa hasil torefaksi. Kemudian emisi SO₂ menurun drastis dari 34,67% menjadi 3,09% pada rasio 20%. Akan tetapi, penyalaan instan biomassa tersebut menyedot suplai oksigen lokal secara cepat, sehingga sisa O₂ di area FEGT melonjak menjadi 5,74% karena suplai Over Fire Air (OFA) tidak bereaksi sempurna akibat melemahnya momentum aliran fireball ke elevasi atas. Selain itu, kondisi ini memicu zona kekurangan oksigen yang menyebabkan pembakaran tidak sempurna, ditandai dengan naiknya kembali fraksi mol CO menjadi 24,40% pada rasio 20%. Secara keseluruhan, penerapan co-firing torrefied sawdust terbukti sukses mereduksi emisi lingkungan. Meskipun demikian, penggunaan rasio di atas 12% memicu penurunan suhu FEGT yang ekstrem, sehingga menuntut adanya penyesuaian operasional lebih lanjut.
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Coal-fired power plants (CFPPs) currently still dominate the national electricity energy mix at 61%. As an effort towards energy transition and carbon emission reduction, the co-firing of torrefied biomass (torrefied sawdust) is being implemented in CFPPs; however, determining its optimal mixing ratio requires an in-depth investigation. This study aims to analyze the effect of varying torrefied sawdust co-firing ratios of 12%, 16%, and 20% on combustion characteristics, which include temperature distribution (fireball and Furnace Exit Gas Temperature/FEGT), as well as the spatial distribution of combustion gas species (O₂, CO₂, H₂O, SO₂, CO) in a 315 MW CFPP furnace. The method utilized is a 3D Computational Fluid Dynamics (CFD) numerical simulation using ANSYS Fluent software under steady-state conditions while maintaining a constant excess air ratio. The simulation results indicate that the high volatile matter content in the torrefied sawdust triggers a flash combustion phenomenon at the lower elevations of the furnace. This causes a shrinkage in the fireball volume and a significant decrease in the FEGT value from 1121.9°C (100% coal baseline) to 1072.2°C (12%), 998°C (16%), and down to 931°C (20%). Regarding gas species, co-firing is proven effective in reducing the CO₂ mole fraction from 11.34% to 9.75% (at a 20% ratio) due to the lower total carbon input from the biomass. Furthermore, the H₂O mole fraction decreases from 9.62% to 6.80% in line with the extremely low moisture content of the torrefied biomass. Subsequently, SO₂ emissions drop drastically from 34.67% to 3.09% at a 20% ratio. However, the instant ignition of the biomass rapidly depletes the local oxygen supply, causing the residual O₂ at the FEGT area to surge to 5.74% because the Over Fire Air (OFA) supply fails to react completely due to the weakened upward momentum of the fireball flow to the upper elevations. In addition, this condition creates oxygen-deficient zones leading to incomplete combustion, indicated by a rebound in the CO mole fraction to 24.40% at the 20% ratio. Overall, the implementation of torrefied sawdust co-firing is proven successful in reducing environmental emissions. Nevertheless, utilizing a ratio above 12% triggers an extreme drop in FEGT, thus requiring further operational adjustments.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Rasio Co-Firing, Batu Bara, Torrefied Sawdust, Karakteristik Pembakaran, Co-Firing Ratio, Coal, Combustion Characteristics, CFD
Subjects:	T Technology > TJ Mechanical engineering and machinery > TJ254.7 Combustion chambers T Technology > TJ Mechanical engineering and machinery > TJ263.5 Boilers (general)
Divisions:	Faculty of Vocational > Mechanical Industrial Engineering (D4)
Depositing User:	Yeyen Nur Fhadila
Date Deposited:	28 Jul 2026 02:42
Last Modified:	28 Jul 2026 02:42
URI:	http://repository.its.ac.id/id/eprint/138470

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