Mineralogy, chemical composition and leachability of ash from biomass combustion and biomass–coal co-combustion

Abstract

Ash samples from biomass combustion or co-combustion with coal were analysed. The aim of this study of ash was to determine its mineral and chemical composition, and the chemical composition of solutions obtained during one-step water extraction. Besides the chemical analysis, X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectrometry (SEM-EDS) were applied. The mineral and chemical composition of ash samples differ strongly. The content of heavy metals in the ash is generally low, but in some samples the limits of the content of some elements determined for fertilizers or soil amendments are exceeded. The relatively poor correlation between the concentration in leachate and bulk content in ash indicates that numerous elements are present in different forms in the studied samples. The results indicate that the potential use of biomass ash, or ash from biomass–coal co-combustion, requires complex studies that explore ash and leachates.

Repurposing Fly Ash Derived from Biomass Combustion in Fluidized Bed Boilers in Large Energy Power Plants as a Mineral Soil Amendment

“…Comparing our results with the findings of Wilczyńska-Michalik et al [12], it can be safely concluded that the macronutrient content is mostly convergent, especially with regard to P 2 O 5 and K 2 O. However, the concentration of CaO as well as S in the CFB fly ash differed more significantly compared to both findings.…”

“…However, the concentration of CaO as well as S in the CFB fly ash differed more significantly compared to both findings. For the fly ash samples CFB1 and CFB2, the concentration of CaO ranged from 12.86 to 14.07 wt%, which was found to be lower than the CaO concentration reported by Wilczyńska-Michalik et al [12] (18.56 wt% CaO). On the other hand, the fly ash examined during our study was richer in sulfur content (1.58-1.83 wt%) than the fly ash examined by Wilczyńska-Michalik et al [12] (1.12 wt%).…”

“…For the fly ash samples CFB1 and CFB2, the concentration of CaO ranged from 12.86 to 14.07 wt%, which was found to be lower than the CaO concentration reported by Wilczyńska-Michalik et al [12] (18.56 wt% CaO). On the other hand, the fly ash examined during our study was richer in sulfur content (1.58-1.83 wt%) than the fly ash examined by Wilczyńska-Michalik et al [12] (1.12 wt%). The differences in the macronutrient content between both studies can probably be attributed to a different biomass feedstock mixture being incinerated in the same power plant.…”

“…Dahl et al [28] reports that the pH of biomass ash delivered from a 246 MW fluidized bed boiler was found to be in the 11.9 to 12.6 range; Uliasz-Bocheńczyk et al [58] reported biomass ash to have a pH even more alkaline (pH 12.92).Żelazny and Jarosiński [13], in their research on evaluating the biomass ash from Połaniec (205 MW) energy plant as a possible fertilizer, also confirm that the pH of biomass ash was highly alkaline, at pH > 11, and they concluded that such conditions may promote a significant loss of ammonia and phosphorus from NPK biomass fertilizer, as a result of the decomposition of ammonia from the nitrate ammonia compound and the formation of phosphorus compounds insoluble in water. In regard to the conductivity, Wilczyńska-Michalik et al [12], in their research on biomass fly ash from the same 205 MW energy plant as ours, reveal a comparable conductivity which is equal to 11.38 mS/cm.…”

Influence of Biomass Incineration Temperature on the Content of Selected Heavy Metals in the Ash Used for Fertilizing Purposes

“…The content of heavy metals in biomass ash presented in [32] was generally below the limits for fertilizers or soils. However, the significant variability in mineral and chemical composition of ash indicates that a comprehensive examination of ash samples is necessary to determine the possible scope of its application.…”