Effect of Mineral Additives on Fusion Behavior of Agricultural Residue Ashes during Combustion or Co-combustion with Lignite

Abstract

In this work, the ash fusibility behaviour of selected agricultural residues and their blends with lignite was studied, by carrying out chemical, mineralogical, fusibility and thermogravimetric analyses and calculating slagging/fouling indicators for predicting deposition tendencies in boilers. Two additives, bauxite, and clinochlore, were used at varying amounts to reduce ash melting, followed by examining their anti-fusion mechanisms. Initial deformation and softening temperatures of biomass materials were low for combustion processes operating above 900 °C due to their high concentration in K, Na, and P compounds. When the additives were mixed with raw fuels or lignite/biomass blends, the initial deformation of ashes started at temperatures up to 340 °C higher, whereas the fluid temperature in most cases exceeded 1500 °C. Bauxite was more effective than clinochlore. The positive impact of additives was attributed to the mineralogical transformations during ashing to phases with a high melting point through reactions with K, Na-bearing minerals, or CaO of fuel ashes.

Advances in Efficient Utilization of Low-Rank Fuels in Coal and Biomass-Fired Systems: A Comprehensive Review

“…As corrosion inhibitors, the surface of straw ash was substantially sintered and melted at 650 °C, resulting in SiO 2 , KCl, K 2 Si 4 O 9 , and K 2 CrO 4 corrosion-inducing composition. As melting point-elevating agents, bauxite and clinochlore were combusted additively with coal, biomass, and biomass blends . Bauxite was discovered more effective than clinochlore more effective in elevating ash melting point (AMP) as the melting temperature rose linearly with an increase in the content of MgO, from 1314 °C for the MgO content of 4.62% to 1398 °C for 12.58% MgO .…”

“…As melting point-elevating agents, bauxite and clinochlore were combusted additively with coal, biomass, and biomass blends. 157 Bauxite was discovered more effective than clinochlore more effective in elevating ash melting point (AMP) as the melting temperature rose linearly with an increase in the content of MgO, from 1314 °C for the MgO content of 4.62% to 1398 °C for 12.58% MgO. 158 The effectiveness of the additives was attributed to their role in inducing mineralogical transformations during ashing.…”

Study of Dendromass Ashes Fusibility with the Addition of Magnesite, Limestone and Alumina

“…An ash inclination to agglomeration in the combustion bed, slagging, fouling, etc., is evaluated in industrial practice by indices derived from the chemical composition of ash/slag from coal combustion, which are substantiated by long-term experience. Although the research focused on the verification of these indices to bio-ash is not satisfactory [3,5,6,[10][11][12][13][14][15][16][17][18][19][20][21][22][23], an effort to use some of them for the assessment of bio-ashes remains.…”