Boiler merupakan salah satu komponen kunci dalam Pembangkit Listrik Tenaga Uap (PLTU) yang mengubah air menjadi uap bertekanan tinggi untuk menggerakkan turbin uap dan menghasilkan listrik. Boiler pada PLTU pada umumnya menggunakan batu bara sebagai bahan bakar utama, sehingga desain efisiensi disesuaikan pada indikator bahan
bakar batubara. Skripsi ini mengevaluasi efisiensi boiler ketika mencampur batu bara dengan biomassa (co-firing). Co-firing dilakukan pada Juli 2023 (97% batu bara, 3%
biomassa) pada beban 19,5 MW, Oktober 2023 (96% batu bara, 4% biomassa) pada beban 21,59 MW, dan Januari 2024 (96% batu bara, 4% biomassa) pada beban 22,04 MW. Hasil perhitungan menunjukkan besar efisiensi boiler sebelum cofiring dengan heat loss method 84,676%-85,933% dan setelah penerapan co-firing 81,116%-83,854%, terjadi penurunan efisiensi sebesar 0,5%-4,375%. Penyebab heat loss yang signifikan
diantaranya heat loss dry flue gas, penguapan hydrogen dalam bahan bakar, dan moisture dalam bahan bakar. Ini disebabkan oleh perpindahan panas yang kurang efektif di dalam
boiler dan kandungan tinggi hydrogen serta moisture dalam bahan bakar. Setelah penerapan co-firing heat loss terbesar disebabkan oleh penguapan hydrogen dalam bahan
bakar.

Boilers are one of the key components in a coal fired power plant that converts water into high-pressure steam to drive steam turbines and generate electricity. Boilers in coal fired power plant generally use coal as the main fuel, so the efficiency design is adjusted to the coal fuel indicator. This thesis evaluates the boiler efficiency when mixing coal with biomass (co-firing). Co-firing was conducted in July 2023 (97% coal, 3% biomass) at
19.5 MW load, October 2023 (96% coal, 4% biomass) at 21.59 MW load, and January 2024 (96% coal, 4% biomass) at 22.04 MW load. The calculation results show that the
boiler efficiency before co-firing with heat loss method is 84.676%-85.933% and after the application of co-firing 81.116%-83.854%, there is a decrease in efficiency of 0.5%
4.375%. The causes of significant heat loss include dry flue gas heat loss, evaporation of hydrogen in the fuel, and moisture in the fuel. This is due to less effective heat transfer in the boiler and high content of hydrogen and moisture in the fuel. After the application of co-firing¬ the largest heat loss is caused by the evaporation of hydrogen in the fuel.