Experimental and numerical techniques to evaluate coal/biomass fly ash blend characteristics and potentials

Usman Khalid; Asif Hussain Khoja; Syed Sheraz Daood; Waqar Ul Habib Khan; Israf Ud Din; Abdulaziz Al-Anazi; Antonella Petrillo

doi:10.1016/j.scitotenv.2023.169218

Experimental and numerical techniques to evaluate coal/biomass fly ash blend characteristics and potentials

Sci Total Environ. 2024 Feb 20:912:169218. doi: 10.1016/j.scitotenv.2023.169218. Epub 2023 Dec 12.

Authors

Usman Khalid¹, Asif Hussain Khoja², Syed Sheraz Daood³, Waqar Ul Habib Khan¹, Israf Ud Din⁴, Abdulaziz Al-Anazi⁵, Antonella Petrillo⁶

Affiliations

¹ Fossil Fuels Laboratory, Department of Thermal Energy Engineering, U.S.-Pakistan Centre for Advanced Studies in Energy (USPCAS-E), National University of Sciences & Technology (NUST), Sector H-12, Islamabad 44000, Pakistan.
² Fossil Fuels Laboratory, Department of Thermal Energy Engineering, U.S.-Pakistan Centre for Advanced Studies in Energy (USPCAS-E), National University of Sciences & Technology (NUST), Sector H-12, Islamabad 44000, Pakistan. Electronic address: asif@uspcase.nust.edu.pk.
³ Institute of Energy and Environmental Engineering, Faculty of Electrical, Energy & Environmental Engineering, University of the Punjab, Quaid-e-Azam Campus, Lahore, Pakistan; Energy Engineering Research and Development Centre, Faculty of Electrical, Energy & Environmental Engineering, University of the Punjab, Quaid-e-Azam Campus, Lahore, Pakistan. Electronic address: sdaood.icet@pu.edu.pk.
⁴ Faculty of Science and Arts, Department of Chemistry, King Khalid University, Muhayil, Asir, Saudi Arabia.
⁵ Department of Chemical Engineering, College of Engineering, King Saud University, P. O. Box 800, Riyadh 11421, Saudi Arabia. Electronic address: aalanazi15@ksu.edu.sa.
⁶ Department of Engineering, University of Naples "Parthenope", Isola C4, Centro Direzionale Napoli, Napoli, NA 80143, Italy. Electronic address: antonella.petrillo@uniparthenope.it.

PMID: 38092215
DOI: 10.1016/j.scitotenv.2023.169218

Abstract

Fossil and renewable fuels are used by industrial units that produce energy-intensive products. Competitive fuel pricing encourages these fuel sources' usage globally, particularly in developing nations, which leads to large volumes of byproducts like fly ash among thermal power plant operators. The elements and compounds found in coal fly ash (CFA) and biomass fly ash (BFA) can be utilized through several engineering applications. This study aims to assess typical CFA and BFA samples quantitatively and qualitatively via techniques such as ultimate analysis (CH-S), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray fluorescence (XRF) elemental analysis, and ash fusion temperature (AFT), to anticipate the ideal ratios of coal to biomass blends for combustion applications while adhering to environmental regulations. The optimal blend, consisting of 75 % CFA and 25 % BFA, exhibited improved carbon (C%) and hydrogen (H%) percentages, increasing from 2.5 % to 4.67 % and from 0 % to 0.12 %, respectively. These improvements were further confirmed by the observed functional groups in FTIR, indicating a rising trend in both carbon and hydroxyl groups from BFA to CFA. XRF and XRD also confirmed it and TGA also showed optimum mass loss (ML%) behavior of 14.55 % for 75CFA + 25BFA. According to slagging and fouling indices, the values of R_B/A, R_s, and F_u indicate a reduction in slagging and fouling issues through the blending of CFA with BFA. Simultaneously, the fusion temperature increased from 1181 °C to 1207 °C. CFA was found to increase the AFT of the BFA from 1197 °C to 1247 °C, mitigating their propensity. This suggests that a blend of 75CFA + 25BFA results in lower to medium range of slagging and fouling. However, AFI and BAI indicate a slightly higher range. AFT analysis further validates the conclusions drawn from the indices. The ternary phase diagram shows that the ash's melting point increases in the optimum blend. This is attributed to a reduced content of K₂O (<15 %) and increased proportions of >50 % CaO and SiO₂, effectively inhibiting slagging, agglomeration, and deposition. Meanwhile, the blend maintains a medium level of acidity and susceptively to corrosion, as observed in the case of 75CFA + 25BFA. The identification of optimal blend ratios can be anticipated to offer essential solutions for future research, aiming to ensure smooth industrial operations and regulatory compliance in power plants.

Keywords: Ash fusion analysis; Biomass fly ash; Coal fly ash; Industrial units; Slagging and fouling indices; Thermal power plant operators.