ANALYSIS OF COMBUSTION CHARACTERISTICS AND SLAGGING MECHANISM OF Caragana korshinskii AND Sophora japonica BIOCHAR

Bai Yujia; Li Xinnan; Niu Wenjing; Wang Dongbiao; Zhang Jing; Yang Yuanqing

doi:10.19912/j.0254-0096.tynxb.2025-1119

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Acta Energiae Solaris Sinica ›› 2026, Vol. 47 ›› Issue (12) : 452-460. DOI: 10.19912/j.0254-0096.tynxb.2025-1119

ANALYSIS OF COMBUSTION CHARACTERISTICS AND SLAGGING MECHANISM OF Caragana korshinskii AND Sophora japonica BIOCHAR

Bai Yujia^1,2, Li Xinnan^1,2, Niu Wenjing^1,2, Wang Dongbiao^1,2, Zhang Jing^1,2, Yang Yuanqing^1,2

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Abstract

Biochars were prepared from Caragana korshinskii and Sophora japonica at pyrolysis temperatures of 240~480 ℃. Their combustion characteristics were evaluated by proximate analysis, ultimate analysis, calorific value determination, and thermogravimetric analysis, while ash composition and slagging rate were analyzed to assess slagging tendency. Scanning electron microscopy and X-ray diffraction were further employed to characterize the microstructure and mineral phase evolution of the ash. The results showed that the higher heating values of the two feedstocks increased overall after pyrolysis, reaching 27690 kJ/kg for Caragana korshinskii and 23907 kJ/kg for Sophora japonica. Caragana korshinski biochar produced at 400 ℃ exhibited the highest comprehensive combustion characteristic index of 1.864 × 10^-8 mg²/（K³·min²）, with a maximum combustion rate of 1.70 mg/min, corresponding to 3.02 and 1.98 times that of the raw Caragana, respectively. Its stable combustion index and volatile releasing index were 5.69×10^-6 mg/（K²·min） and 2.22×10^-4 mg/（K²·min）, respectively, both the highest among the tested samples. After high-temperature pyrolysis, the ignition temperature of Sophora japonica biochar increased to 327.9 ℃, 35.9% higher than that of the raw material, while its maximum combustion rate ranged from 1.01 to 1.70 mg/min, with SJ-480 reaching 1.70 mg/min. At air-blowing intensities of 0.1, 0.2, and 0.3 m/s, the slagging rates of both biochars were below the 9% reference value. The slagging rates of CK~400 were 0.65%~2.21%, while those of SJ-480 were 0.64%~2.41%. After ashing at 550 ℃, the ash of Caragana korshinski biochar pyrolyzed at 400-480 ℃ exhibited SiO₂ and MgSiO₃ phases together with a relatively dense sintered structure, which may affect the migration and aggregation of low-melting-point potassium-bearing species. In contrast, Sophora japonica biochar ash showed different mineral phase compositions and structural evolution characteristics, corresponding to its different slagging response.

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agricultural waste / biochar / pyrolysis temperature / ash / slagging / combustion

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Bai Yujia, Li Xinnan, Niu Wenjing, Wang Dongbiao, Zhang Jing, Yang Yuanqing. ANALYSIS OF COMBUSTION CHARACTERISTICS AND SLAGGING MECHANISM OF Caragana korshinskii AND Sophora japonica BIOCHAR[J]. Acta Energiae Solaris Sinica. 2026, 47(12): 452-460 https://doi.org/10.19912/j.0254-0096.tynxb.2025-1119

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