STUDY ON ALTERNATIVE FUELS FOR LIME KILN IN A KRAFT PULP MILL VIA DIRECT COMBUSTION AND GASIFICATION
Authors: , Syamsudin , Susanto Herri 
Published: August 2017

Most common lime reburning kiln fuels are natural gas. Limiting gas and increasing its prices encourage pulp mills to find other types of energy resources such as coal and biomass. The use of those solid energy resources may be implemented through a direct solid combustion or via gasification process. Sludge about 95 kg/ton CaO available in the pulp mill. The sludge has a heating value of 14 MJ/kg (dry basis). The palm nut shell has a heating value of 21 MJ/kg. Coal, although it is belong to the category of non-renewable recources, has a heating value of 25 MJ/kg. In production rate of CaO about 380 ton/day, direct combustion of natural gas with sludge cake reduce the natural gas consumption by 20% and higher for coal and palm nut shell. The portion natural gas substitution is limited by the availability of sludge and the attainable combustion temperature. Portion of coal and palm nut shell may be more flexible in term of availability and energy. Depending on gasifying agents and reactor configuration, the gaseous product of gasification may have a heating value of 11 MJ/Nm3 (sludge cake), 18 MJ/Nm3 (palm nut shell), and 19 MJ/Nm3 (coal). In contrast to direct combustion of solid fuel, the gaseous product of gasification may be used with a less modification of the burner and has cleaner combustion. Co-combustion of gaseous fuel from sludge may reduce the natural gas consumption by 18% and higher for gaseous fuel from coal and palm nut shell.Keywords: sludge cake, palm nut shell, coal, co-combustion, gasification, lime kiln ABSTRAKBahan bakar lime kiln umumnya berupa gas alam. Keterbatasan cadangan dan peningkatan harga gas alam mendorong pabrik pulp memanfaatkan sumber energi alternatif seperti batubara dan biomassa. Bahan bakar ini dapat diimplementasikan melalui pembakaran langsung atau melalui proses gasifikasi. Lumpur sebanyak 95 kg/ton CaO merupakan biomassa yang tersedia di pabrik pulp. Lumpur ini memiliki nilai kalor 14 MJ/kg (basis kering). Cangkang sawit merupakan biomassa alternatif dengan nilai kalor 21 MJ/kg. Batubara, meskipun termasuk sumber tidak-terbarukan, memiliki nilai kalor 25 MJ/kg. Pada produksi CaO sebesar 380 ton/hari, pembakaran langsung lumpur mengurangi konsumsi gas alam 20% dan lebih tinggi untuk batubara dan cangkang sawit. Penggantian gas alam ini dibatasi ketersediaan lumpur dan suhu pembakaran yang dicapai. Penggantian gas alam dengan batubara dan cangkang sawit lebih fleksibel dalam ketersediaan dan energi yang diperoleh. Tergantung medium gasifikasi dan konfigurasi reaktor, gas hasil gasifikasi dapat mencapai nilai kalor 11 MJ/Nm3 (lumpur kering), 18 MJ/Nm3 (cangkang sawit), dan 19 MJ/Nm3 (batubara). Berbeda dengan pembakaran langsung bahan bakar padat, gas hasil gasifikasi dapat digunakan dengan sedikit modifikasi burner dan hasil pembakaran yang lebih bersih. Pembakaran gas hasil gasifikasi lumpur dapat mengurangi konsumsi gas alam 18% dan lebih tinggi lagi untuk gas hasil gasifikasi batubara dan cangkang sawit.Kata kunci: lumpur, cangkang sawit, batubara, pembakaran, gasifikasi, lime kiln