Investigation on Blended Ash Fusibility Characteristics of Biomass and

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An Investigation on Blended Ash Fusibility Characteristics of Biomass and Coal with High Silica-Alumina Xiuwei Ma, Fenghai Li, Mingjie Ma, and Yitian Fang Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b01070 • Publication Date (Web): 18 Jul 2017 Downloaded from http://pubs.acs.org on July 18, 2017

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An Investigation on Blended Ash Fusibility Characteristics of

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Biomass and Coal with High Silica-Alumina

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Xiuwei Ma,†,‡ Fenghai Li,*,†,‡,§ Mingjie Ma,† and Yitian Fang§

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†

School of Chemistry and Chemical Engineering, Henan Polytechnic University, Jiaozuo, Henan 454003, People,s

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Republic of China ‡

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Department of Chemistry and Chemical Engineering, Heze University, Heze, Shandong 274015, People,s Republic of China

§

State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan,

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Shanxi 030001, People,s Republic of China

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ABSTRACT: The blended ash fusibility characteristics and its variation mechanism of biomass

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(peanut hull (PH), bean straw (BS), and corn cob (CC)) and Changzhi coal (CZ) with high

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silica-alumina were investigated using ash fusion temperature (AFT) detector, thermo-gravimetric

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differential scanning calorimetry (TG–DSC), X-ray diffraction (XRD), and FactSage software.

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The results showed that the AFT of CZ mixed ash decreased with the addition of PH ash, and the

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AFT of CZ mixed ash decreased rapidly (0–30%) and then changed slowly (30–50%) with the

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increasing BS ash mass ratio, however, the AFT of CZ mixed ash decreased firstly (0–20%) and

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then increased (20–50%) with the increasing CC ash mass ratio. The different AFT variations

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mainly depend on the ash chemical compositions and their existing form. Biomass ash with high

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contents of fluxing oxides promotes the transformations of high melting point (MP) mullite and

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quartz into low-MP minerals and their eutectics, resulting in a decrease in the AFT. At high

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temperature, with increasing biomass ash mass ratio, K+ replaces Ca2+ in anorthite to form the

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low-MP leucite, which decreases the AFT further. Some potassium element existed in the form of

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kaliophilite, leading to an increase in AFT. The combination of TG–DSC, XRD, and

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thermodynamic calculation provides a good method to explore the ash fusion mechanism from the

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mineral evolution.

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1. INTRODUCTION

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Biomass, a carbon-neutral and renewable energy resource, has been paid wide attentions

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because of worldwide energy crisis and environmental pollution.1–3 However, the large-scale use

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of biomass has limitations for its low calorific value and density, high moisture content, high

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transportation cost, and seasonal supply.4 Fortunately, the co-utilizations of biomass with coal (e.g.,

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co-gasification and co-combustion) provide a good way to use biomass on a large-scale. Moreover,

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the co-utilizations can mitigate high dependence on fossil fuels and decrease the emission of

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greenhouse gases.5,6 Recently, the co-gasification of coal and biomass has been developed rapidly

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in many countries. It has more advantages than their individual gasification, such as improvement

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in gas yield, alleviation of some ash-related problems,7,8 and enhancement in coal gasification

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reactivity (alkali and alkaline earth metal in biomass ash act as catalysts).9,10 Compared with the

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gasification technologies of fixed-bed and fluidized-bed, entrained-flow bed (EF) gasification is

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considered as a promising technology for its feedstock flexibility, high carbon conversion

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efficiency, and high quality synthetic gas with low tar content.11–13

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During the process of EF gasification, most of the organic matters convert into syngas, and

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inorganic matters transfer into molten slag and fly ash. The fly ash is entrained with the syngas,

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and molten slags flow along the gasifier wall, and finally discharge from the slag outlet. Therefore,

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the operation temperature of gasifier must be high enough to keep the ash/slag in liquid state.14 In

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industrial practice, ash fusion temperature (AFT) is an important parameter to design the gasifier,


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and to determine whether coals are suit for EF gasification directly (e.g., GE, Texaco, Shell, and

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GSP),15 because it partially reflects ash agglomeration and sintering, which strongly affects ash

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deposition and slag formation.16 And the AFT test is widely used to evaluate the ash slagging

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tendency during coal conversion, despite its shortcomings.17,18 Generally speaking, when a coal is

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ed in EF gasifier, its fluid temperature (FT) is required 1380 oC) coal, it is important to reduce its AFT for EF gasification, because this can reduce

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the consumption of oxygen and energy, and increase the lifetime of gasifiers.19,20 High AFT coal is

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abundant, which accounts for 57% coal reserves in China, and most of them have high

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silica-alumina contents (the total mass fraction of SiO2 and Al2O3 >80% in ash).21 It is important

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to modify the AFT of these coals for their clean and high efficiency conversion through EF

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gasification.

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Blending coal and fluxing agent are generally used to change coal AFT.22 The essence of the

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two methods is to change the ash chemical compositions. Thus, biomass with high concentrations

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of alkaline and alkaline earth elements can serve as fluxing agent to decrease the AFT of coal with

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high silica-alumina.23,24 The blended ash fusibility characteristics of coal and biomass differ

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greatly from that of feedstock. Li et al.25 explored the mixed ash fusion behavior of Chinese lignite

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and three biomasses (peanut hull, corn straw, and pine sawdust), the addition of peanut hull caused

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AFT fluctuation of the lignite mixed ashes due to the formation of high melting point (MP) (1600

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o

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variation. Haykiri-Acma et al.26 studied the AFT of chestnut shell and Turkish lignite mixed ash,

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the high levels of deviations between experimental AFTs and theoretical AFTs were caused by the

C was selected as the reference to define the low-MP or high-MP) mullite and its content


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increasing acidic oxides (SiO2 + Al2O3 + TiO2) contents, especially for aluminum content. Chen et

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al.15 investigated the influences of cotton stalk and sargassum natans on Jincheng coal AFT, the

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biomass could decrease the AFT of Jincheng coal to satisfy the requirement of EF gasification.

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Several explorations have been performed on the influence factors on synthesis gas,27–29

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synergetic effects and kinetics in co-gasification of coal and biomass.9,30,31 And among the

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investigations on ash fusibility characteristics of coal and biomass, most of them have focused on

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the low-rank coals (usually have a low silica-alumina content and low AFT) and biomass.26,32,33

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Studies on the blended ash fusibility characteristics of biomass and high silica-alumina coal under

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reducing atmosphere are relatively less. The mixed ash fusibility behavior is not additive, because

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the chemical and mineral compositions are different markedly, and some complex interactions

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exist between different minerals.15,25 The aims of this paper were to investigate the blended ash

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fusibility characteristics of biomass and coal with high silica-alumina, and to explore its variation

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mechanism from mineralogy by thermo-gravimetric differential scanning calorimetry (TG-DSC),

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X-ray diffraction (XRD), and FactSage software. Results of this study might provide basic data

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and theoretical references for the research and development of co-gasification technologies for

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high silica-alumina coal and biomass.

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2. EXPERIMENTAL SECTION

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2.1. Properties of Experimental Materials.

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Agricultural residue is a promising biomass gasification feedstock for its abundant and low

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cost. Three biomasses (peanut hull (PH), bean straw (BS), and corn cob (CC)) and a high AFT

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Changzhi coal with high silica-alumina (CZ, from Shanxi province, China) were selected. The


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four samples were ground and sieved to a particle size of 70%. The acid oxides (SiO2 and Al2O3) with high ionic potential (Si4+

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and Al3+ are 95.24 nm–1 and 60.00 nm–1, respectively) are prone to combine with oxygen and form

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strong SiO2 network, which lead to an increase in AFT. While the basic oxides (CaO, K2O, and

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MgO), as the SiO2 network modifiers, can change the stable network from tecto-silicates,

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ino-silicates, cyclo-silicates, soro-silicates to neso-silicates, leading to a decrease in AFT. This

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may explain the differences that AFT of CZ is higher than that of PH and CC. Although the basic

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oxides contents are high in BS ash especially for CaO (43.40%), the alumino-silicates are in

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minority for its low amounts of SiO2 and Al2O3 (the total mass fraction of SiO2 and Al2O3 is only

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10.84%). And some alkali metals volatilize in ash fusion process, CaO and MgO change into the

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main compositions in the remainder ash. Thus, minor amounts of alkali/alkali-earth

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alumino-silicates melt at fairly high temperatures, which results in its high DT (1486 oC).

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Compared with Ca2+, K+ has a stronger effect on depolymerization alumino-silicate network for its

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high ionic radius and weaker aggregation effect for its low charge, which may explain the AFT of

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PH is higher than that of CC.38

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Tables 2–3 should be placed here.

3.2. AFT Variations of CZ with Biomass Ash Addition.


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Figure 1 shows the CZ mixed AFT variations with the increasing mass ratio of biomass (PH,

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BS, and CC) ash, respectively. The AFT variations are not the linear variation with the addition of

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three biomass ashes. For PH, the AFT of the blended ash decreased with increasing PH ash mass

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ratio. The FT of mixed ash was 20% (raw material ratio

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was 37.07% based on air dry basis (AD)). For BS, the AFT of the mixed ash was lower than that

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of either single CZ or BS ash. The AFT decreased markedly (0–30%), however, the AFT changed

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lowly when the BS ash mass ratio was >30%. As the BS ash mass ratio was >10% (raw material

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ratio was 18.44% based on AD), the FT was 20% (Figure 3(d)). From Figure 3(e) TG curve, four major

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weight loss stages occurred in CZ mixed ash. The endothermic peak in DSC curves (Figure 3(f))

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in range of 600–710 oC were stronger than that of PH mixed ash and BS mixed ash, this might

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result from not only the decomposition of carbonate minerals, but also the formation of low-MP

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(600–700 oC) Na-silicates (Na2O·2SiO2) and K-silicates (K2O·4SiO2), which melted and

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absorbed energy.42 The exothermic peak of CZ mixed ash disappeared when CC mass increased

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to 40% (Figure 3(f)). Different from the CC ash, the obvious endothermic peak was not occurred


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in range of 800–1000 oC for CZ mixed ash, this might result from the formation of silicate or

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aluminosilicate through the reaction of SiO2, Al2O3, and K2O, leading the CZ mixed ash in

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endothermic state.

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Figure 3 should be placed here.

3.3.2. Mineral Behaviors During Ash Fusion.

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The variation in ash fusibility characteristics can be predicted by the change of mineral

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components and their contents.25 Figure 4(a) illustrates the XRD patterns of the four pure ash

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samples at 575 oC under reducing atmosphere. The CZ ash was mainly composed of quartz (SiO2),

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metakaolin (Al2Si2O7), anhydrite (CaSO4), calcite (CaCO3), and hematite (Fe2O3). The

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decompositions of anhydrite and calcite might used to explain the two small weight loss stages in

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TG curve (Figure 2). However, mineral crystals of PH ash were mainly in the form of quartz,

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fairchildite (K2Ca(CO3)2), arcanite (K2SO4), and calcite. The fairchildite, arcanite, and calcite

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decomposed into fluxing oxides (CaO and K2O) in ash fusion process. These oxides reacted with

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SiO2 and Al2O3 to form low-MP alumino-silicate minerals, which led to a low AFT. In addition to

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the fairchildite and calcite, periclase (MgO), lime (CaO), and whitlockite (Ca3(PO4)2) were also

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detected in BS ash. In ash fusion process, calcite decomposed into CaO further, leading to a high

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CaO content in BS ash. The large amounts of CaO and MgO led to minor amounts of molten

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alkali/alkali-earth alumino-silicates in BS ash at high temperature, resulting in a high AFT. Only

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two major K-bearing minerals of sylvite and potassium carbonate hydrate (K2CO3·1.5H2O) were

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determined in CC ash, the K2CO3·1.5H2O was formed through the original mineral K2CO3

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hydration in ambient air. This might prove the fact that the main weight loss stage in range of


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833–1003 oC (TG curve) was mainly caused by the evaporation of sylvite.

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Figure 4(b) shows the XRD patterns of CZ ash at different temperatures under reducing

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atmosphere. The content variation for the same mineral can be reflected by the variation in

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diffraction intensity.43 The diffraction intensity of quartz reduced when the temperature reached

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1000 oC, because it transferred into cristobalite (SiO2) and reacted with other minerals. Metakaolin

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was not detected, meanwhile, new phases mullite, anorthite (CaAl2Si2O8), and gehlenite

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(Ca2Al2SiO7) were formed. The generation of mullite was consistent with the exothermic peak in

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DSC curve. With temperature continue increasing, the diffraction peak of quartz disappeared,

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mullite and cristobalite became the major minerals, and only minor amount of anorthite existed in

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CZ ash. High-MP mullite and cristobalite played an important role in increase AFT. 44 This was the

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main reason for CZ ash with high AFT.

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The mineral compositions of blended ashes with different biomass ash ratios at 1100 oC

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under reducing atmosphere are used to investigate the CZ mixed AFT modification mechanism.

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Because the elements existing forms are various, and crystal minerals contents are moderate at

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1100 oC, which could better reflect the AFT variation.22,25 Figure 5 presents XRD patterns of

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blended ashes at 1100 oC, and Table 5 shows their component contents calculated by RIR. As

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shown in Figure 5(a), when the PH ash ratio increased to 10%, the diffraction intensity of mullite

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reduced obviously and the cristobalite disappeared, and the silicon transformed into quartz. In

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contrast, the diffraction intensity of anorthite increased and new phase albite was formed. Because

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the Ca2+ and Na+ as electron acceptors were easy to enter into the crystal lattice of mullite, forming


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anorthite and albite (NaAlSi3O8).21 In addition, the following reactions might occur:

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2SiO2 + Al2O3 + CaO → CaAl2Si2O8, ∆G = –133.60 kJ·mol–1

(1)

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6SiO2 + Al2O3 + Na2O → 2NaAlSi3O8, ∆G = –397.51 kJ·mol–1

(2)

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2SiO2 + 3Al2O3 → Al6Si2O13, ∆G = –18.06 kJ·mol–1

(3)

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The Gibbs free energy (∆G) of (3) was significantly higher than that of (1) or (2) at 1100 oC. Thus,

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the remaining SiO2 and Al2O3 were also transferred into anorthite or albite firstly under high

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concentrations of Na2O and CaO. As shown in Table 5, the contents of low-MP minerals (anorthite

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and albite) were higher than that of original CZ ash, leading to a decrease in AFT. As the PH ash

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ratio increased to 20%, anorthite and albite became the major fluxing minerals. Meanwhile, the

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mullite content decreased further, it couldn’t provide a strong supporting effect to go against the

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deformation of ash cone, resulting in AFT decrease. With the PH ash mass ratio continue

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increasing (>20%), the mullite diffraction peak disappeared and leucite (KAlSi2O6) with low-MP

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(1100 oC) formed. It can be seen from Table 5, the contents of leucite and the amorphous matter

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increased, this might be the main reason for AFT decrease further. At the relative low PH ash ratio

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(30%, the anorthite content decreased, whereas the leucite content

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increased. This may be resulted from the substitution of calcium in anorthite by potassium and to

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form leucite through the reaction:

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CaAl2Si2O8 + 2SiO2 + K2O → 2KAlSi2O6 + CaO, ∆G = –354.20 kJ·mol–1 (4)


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When the BS ash mass ratio was 10%, the main minerals determined in the mixed ash

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were anorthite, albite, leucite, magnesium iron aluminium oxide (MgFe0.2Al1.8O4), and minor

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amounts of quartz and mullite (Table 5). The contents of quartz and mullite decreased markedly

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in comparison to that of CZ ash, which resulted in a low AFT (800 oC. The volatile sylvite was not involved in

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the reactions of other minerals. With increasing temperature, large amounts of liquid slag was

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formed, leading to a decrease in AFT. The liquidus temperature of PH mixed ash was about 1400

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o

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were formed in 1100 oC by calculation, while they were not detected in mixed ash by XRD, the

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two mineral might exist in amorphous state. Mg and Fe mainly existed in form of spinel ((Mg,

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Fe)Al2O4), which had a similar chemical composition with MgFe0.2Al1.8O4 detected by XRD. With

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increasing temperature, the major minerals feldspar (anorthite, sanidine, and albite), leucite,

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nepheline and clinopyroxene were melted and transformed into liquid slag, and its liquidus

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temperature (about 1350 oC) was lower than that of mixed ash (80% CZ ash + 20% PH ash). For

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the mixed ash (80% CZ ash +20% CC ash)( Figure 6(e)), the theoretical mineral compositions

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were basically the same as the BS mixed ash for their relative high amounts of K2O and CaO. The

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liquidus temperature was similar to the mixed ash (80% CZ ash +20% PH ash), which was

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consistent with their similar FTs.

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C. For the mixed ash (80% CZ ash + 20% BS ash)( Figure 6(d)), clinopyroxene and nepheline



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4. CONCLUSION

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Three biomasses (PH, BS, and CC) can effectively modify the AFT of high

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silicon-aluminum coal (CZ). The AFT variations are not the linear variation with the addition of

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three biomass ashes. The formations of low-MP minerals and their eutectics were the main reason

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for CZ blended AFT decrease. Biomass ash rich in calcium and potassium is a good fluxing agent.

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With the increasing K2O content in blended ash, K+ replaces Ca2+ in anorthite to form leucite,

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resulting in a decrease in AFT further. However, the K-bearing mineral kaliophilite can increase

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the AFT. The combination of experiments (TG–DSC and XRD) and software simulation provide a

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good method to investigate the ash fusion mechanism from the mineral evolution.

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AUTHOR INFORMATION

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Corresponding Author

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*Telephone: +86-0530-5668162. E-mail: [email protected]

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Notes

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The authors declare no competing financial interest.

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Acknowledgments

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This work was financially supported by the Natural Science Foundation of Shandong

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Province, China (ZR2014BM014), the Strategic Priority Research Program of the Chinese

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Academy of Sciences (XDA07050103), and Youth Natural Science Foundation of Shanxi


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Province, China (Y5SJ1A1121).

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of different types of sewage sludge. Fuel Process. Technol. 2015, 131, 348–355.

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composition on ash fusibility. Energy Fuels 2016, 30, 1437–1444.

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entrained-flow gasifier. Energ. Convers. Manage. 2014, 86, 683–688.

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melting behavior and mineral reaction mechanism at molecular level of blended coal ash under gasification

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condition. Fuel Process. Technol. 2010, 91, 1591–1600.


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transformation chemistry during combustion of biomass. Energy Fuels 2012, 26, 85–93.

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biomass – chemometric study. Energy 2014, 78, 814–825.

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from Shanxi typical anthracite. J. Fuel Chem. Technol. 2013, 41, 805–813 (Chinese).

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Page 24 of 37

Page 25 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Table Captions Table 1. Proximate and Ultimate Analyses of Raw Samples. Table 2. Ash Fusion Temperatures of Raw Samples (oC). Table 3. Ash Chemical Composition of Raw Samples (wt%). Table 4. Characteristic Parameters Obtained from TG Curves of Ash Samples. Table 5. Mineral Composition of Mixed CZ Ashes with Different Biomass Ash Mass Ratios at 1100 °C by RIR.


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 37

Table 1. Proximate and Ultimate Analyses of Raw Samples Proximate Analysis on an Air-Dry Basis(wt/%) sample

moisture

ash

CZ

0.46

18.03

PH

4.08

BS CC

volatile

Ultimate Analysis on a Dry and Ash-Free Basis (wt/% )

fixed carbon

C

H

Oa

Sb

N

12.72

68.79

86.20

3.08

2.62

3.96

4.14

7.65

62.98

25.29

70.86

6.95

20.99

1.07

0.13

3.21

8.86

66.03

21.90

60.46

7.22

32.15

0.10

0.07

1.06

5.62

70.11

23.21

50.12

4.15

44.01

0.57

1.15

a

Calculated by difference.

b

Total sulfur.

matter


Page 27 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Table 2. Ash Fusion Temperatures of Raw Samples (oC) sample

DTa

STb

HT c

FT d

CZ

1500

>1500

>1500

>1500

PH

1098

1124

1162

1173

BS

1486

>1500

>1500

>1500

CC

957

981

1002

1015

a

deformation temperature.

b

softening temperature.

c

hemispherical temperature.

d

fluid temperature.


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 37

Table 3. Ash Chemical Composition of Raw Samples (wt%) sample

SiO2

Al2O3

Fe2O3

CaO

MgO

SO3

K 2O

Na2O

TiO2

P2O5

Cl

CZ

50.19

32.16

3.03

4.95

1.93

1.76

1.46

1.21

0.92

1.93

0.46

PH

28.86

9.93

3.16

16.88

5.26

6.97

15.80

4.21

1.32

5.41

2.20

BS

7.58

3.26

4.92

43.40

10.20

5.43

16.56

4.18

0.40

2.06

2.01

CC

11.56

3.70

2.62

7.86

2.81

4.62

51.76

3.89

1.17

3.98

6.03


Page 29 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Table 4. Characteristic Parameters Obtained from TG Curves of Ash Samples first weight loss stage sample

second weight loss stage

third weight loss stage

fourth weight loss stage

Ta

Tpb

αc

T

Tp

α

T

Tp

α

T

Tp

α

(oC)

(oC)

(%)

(oC)

(oC)

(%)

(oC)

(oC)

(%)

(oC)

(oC)

(%)

CZ

722-881

758

3.91

1077-1167

1122

2.08

–

–

–

–

–

–

PH

105-177

134

1.6

624-739

687

9.04

–

–

–

–

–

–

BS

95-165

125

1.05

658-759

720

13.06

1045-1177

1117

8.91

–

–

–

CC

53-121

82

2.34

604-674

638

6.56

833-1003

943

23.67

–

–

–

PH1CZ9d

544-802

748

3.16

908-970

936

0.67

1103-1211

1168

2.96

–

–

–

PH2CZ8

563-781

625

3.02

909-964

936

1.04

1042-1203

1156

2.89

–

–

–

PH3CZ7

585-727

645

3.00

913-966

935

0.39

1064-1207

1160

2.94

–

–

–

PH4CZ6

563-724

638

3.66

1086-1205

1155

2.96

–

–

–

–

–

–

PH5CZ5

579-723

649

3.65

923-1077

1012

2.62

1106-1176

1142

1.58

–

–

–

BS1CZ9

572-802

677

4.02

1045-1206

1158

3.09

–

–

–

–

–

–

BS2CZ8

95-159

126

0.35

593-748

684

5.02

1063-1201

1146

2.97

–

–

–

BS3CZ7

56-175

126

0.76

619-745

696

5.73

1012-1198

1148

3.52

–

–

–

BS4CZ6

77-171

126

0.86

627-754

701

6.91

1049-1218

1158

4.17

–

–

–

BS5CZ5

60-185

130

1.3

616-760

709

9.31

–

–

–

–

–

–

CC1CZ9

51-169

122

0.59

623-707

668

2.31

–

–

–

–

–

–

CC2CZ8

50-118

73

0.75

596-726

669

3.73

772-900

858

3.12

914-1002

948

1.82

CC3CZ7

49-130

83

1.83

612-725

677

3.93

788-944

816

4.67

963-1062

992

1.65

CC4CZ6

49-116

79

1.92

601-717

663

4.85

786-928

876

6.41

1044-1187

1117

2.34

CC5CZ5

50-111

78

1.76

608-717

660

5.42

780-933

873

7.69

1124-1219

1180

2.08

a

temperature range of weight loss.

b temperature c weight d

of the maximum weight loss rate.

loss.

PH ash mass ratio is 10% in CZ mixed ash.


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 37

Table 5 Mineral Composition of Mixed CZ Ashes with Different Biomass Ash Mass Ratios at 1100 °C by RIR. Ash

Mineral content ( wt%) 1

2

3

4

5

6

7

8

9

10

11

12

CZ

34.78

8.32

19.12

9.24

–

–

–

–

–

–

–

28.54

+10%PH

28.15

–

–

20.59

9.85

11.29

–

–

–

–

–

30.12

+20%PH

24.78

–

–

26.78

14.72

–

–

–

–

–

–

33.72

+30%PH

–

–

–

38.12

16.85

–

9.79

–

–

–

–

35.24

+40%PH

–

–

–

26.71

10.34

–

26.17

–

–

–

–

36.78

+50%PH

–

–

–

19.34

6.49

–

35.92

–

–

–

–

38.25

+10%BS

7.16

–

–

25.83

9.71

5.63

7.34

10.52

–

–

–

33.81

+20%BS

–

12.86

–

24.19

–

5.10

8.76

13.07

–

–

–

36.02

+30%BS

–

7.62

–

15.47

–

–

14.32

20.12

–

–

–

42.47

+40%BS

–

–

–

–

–

–

–

13.47

30.12

16.15

–

40.26

+50%BS

–

–

–

–

–

–

–

10.08

32.02

11.26

6.28

40.36

+10%CC

26.38

–

–

15.96

6.52

18.37

–

–

–

–

–

32.77

+20%CC

–

–

–

19.37

16.05

–

23.46

–

–

–

–

41.12

+30%CC

–

–

–

–

–

–

38.75

–

23.03

–

–

38.22

+40%CC

–

–

–

–

–

–

37.68

–

28.15

–

–

34.17

+50%CC

–

–

–

–

–

–

39.69

–

32.15

–

–

28.16

1-mullite (Al6Si2O13); 2-gehlenite (Ca2Al2SiO7); 3-cristobalite (SiO2); 4-anorthite (CaAl2Si2O8); 5-albite (NaAlSi3O8); 6-quartz (SiO2); 7-leucite (KAlSi2O6); 8-magnesium iron aluminium oxide (MgFe0.2Al1.8O4); 9-kaliophilite (KAlSiO4); 10-akermanite-gehlenite (Ca2(Mg0.5Al0.5)(Si1.5Al0.5O7)); 11-monticellite (MgCaSiO4). 12-amorphous matter: Includes both the amorphous phase and any carbon (char) components.


Page 31 of 37

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Figure captions Figure 1. CZ mixed AFT variation with the biomass ash mass ratio increase. Figure 2. TG-DSC curves for raw ash samples. Figure 3. TG-DSC curves for blended ashes. Figure 4. XRD patterns of pure ash samples. Figure 5. XRD patterns of blended ashes at 1100 oC. Figure 6. Phase assemblage-temperature curves for ash samples.


Energy & Fuels

(a) 1500

DT ST HT FT

1450

o

T em perature/ C

1400

1350

1300

1250

1200 0

10

20

30

40

50

P H ash m ass ratio/%

(b)

1550

DT ST HT FT

1500 1450

o

T em perature/ C

1400 1350 1300 1250 1200 1150 1100 0

10

20

30

40

50

B S ash m ass ratio/%

DT ST HT FT

(c) 1500 1450 o

T em perature/ C

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 37

1400

1350

1300

0

10

20

30

40

50

C C ash m ass ratio/%

Figure 1. CZ mixed AFT variation with the biomass ash mass ratio increase: (a) PH ash; (b) BS ash; (c) CC ash.

: Above 1500 oC.


Page 33 of 37

(a)100

T G (% )

90

C ZA PH A BSA CCA

80

70

60 0

200

400

600

800 o

1000

1200

T em perature ( C )

(b) 4

C ZA PH A BSA CCA

3

exo

2

D S C (m W /m g)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

1 0 -1 -2 -3 -4 0

200

400

600

800

1000

o

T em perature ( C )

Figure 2. TG-DSC curves for raw ash samples.


1200

Energy & Fuels

(a)100

(b)

T G (% )

94 92

D S C (m W /m g)

+0% P H A +10% P H A +20% P H A +30% P H A +40% P H A +50% P H A

96

exo

+0% P H A +10% P H A +20% P H A +30% P H A +40% P H A +50% P H A

2

98

0

-2

-4

90 88 0

200

400

600 800 o T em perature ( C )

1000

1200

100

(c)

0

(d)

+0% B S A +10% B S A +20% B S A +30% B S A +40% B S A +50% B S A

90

D S C (m W /m g)

T G (% )

200

400


1000

4

0

1200

exo

+0% B S A +10% B S A +20% B S A +30% B S A +40% B S A +50% B S A

2

95

-2

85 -4 80 -6 0

200

400

600

800

o

1000

1200

0

200

400


T em perature ( C ) 100

(e)

(f) 2

D S C (m W /m g)

+0% C C A +10% C C A +20% C C A +30% C C A +40% C C A +50% C C A

90

85

1000

1200

exo +0% C C A +10% C C A +20% C C A +30% C C A +40% C C A +50% C C A

1

95

T G (% )

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 37

0 -1 -2 -3

80

-4 0

200

400

600

800

1000

1200

0

200

400

o

T em perature ( C )

Figure 3. TG–DSC curves for blended ashes.


600

800 o

T em perature ( C )

1000

1200

(a)

3000

1

2000

1 5 2 4 1 3 2 11

1000

3 1

4

1

0

7 6 71

7 4 4

4 7 10 7

94

10 12 12

12

C ZA

1

8

11

4 11

PH A

8

9

BSA

11

11

CCA 10

20

30

40

2-T heta/o

50

60

70

(b)

4000 3000

1

2000

5 2 4 3 1 1 2 3 1

13 13 13

13

13 13

575

13

1

ra tu re o / C

13 13 16

0

1

13 13 13

1000

1100

13

pe

15

15 16 14 13 1 14 4 13 113 16 13 14 13

1000

m

15

Intensity/cps

5000

Te

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Intensity/cps

Page 35 of 37

1200 10

20

30

40

o

2-T heta/

50

60

70

Figure 4. XRD patterns of pure ash samples: (a) four ash samples at 575 oC; (b) CZ ash at different temperature. 1-quartz (SiO2); 2-anhydrite (CaSO4); 3-hematite (Fe2O3); 4-calcite (CaCO3); 5-metakaolin (Al2Si2O7); 6-arcanite (K2SO4); 7-fairchildite (K2Ca(CO3)2); 8-periclase (MgO); 9-lime (CaO); 10-whitlockite (Ca3(PO4)2); 11-sylvite (KCl); 12-potassium carbonate hydrate (K2CO3·1.5H2O); 13-mullite (Al6Si2O13); 14-gehlenite (Ca2Al2SiO7); 15-cristobalite (SiO2); 16-anorthite (CaAl2Si2O8).


Energy & Fuels

(a)

4000

3

3000

1

2000

4

1

21

1

1

1000

1 1 1

6

7

1

0

1 4

ra tio /%

10 20

h

7 47 5 7 4 7 4+5 4 57 4

0

4

30

PH

7

4+5 4+5 4 4 5 4 1 4+5 7 7 44 5 4

1

as

7

4+5 5 1

41

1

Intensity/cps

5000

40 50

10

20

30

40

2-T heta/o

50

60

70

(b)

3

4000 3000

1

2000

1

1 21

1

1000

1 1

1 6 4+5 44 7 4 4 8 1 8 74 2 4 46 2 48 2 8 7 7 7 2 8 4 8 7 8 10 9 10 9 8 8 10 9 9 11 8 11 8 1110

0 0

8 10

2

ra tio /%

4

Intensity/cps

5000

as

h

20

BS

30 40 50

10

20

30

40

o

50

60

70

2-T heta/

(c)

4000

3

3000

1

2000

7

2

1

1000

1

7 6 4+5 7 7 1 4+5 2 1 1 1 7 7 7 7 7 5 7 7 9 7 7 7 79 9 7 9 7 7 7 9 7 9 77 9 9 7 9

1

1

0 0

1 10

h

20

ra tio /%

1

11

as

4

Intensity/cps

5000

30

CC

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 36 of 37

40 50

10

20

30

40

o

2-T heta/

50

60

70

Figure 5. XRD patterns of blended ashes at 1100 oC: (a) PH; (b) BS; (c) CC. 1-mullite (Al6Si2O13); 2-gehlenite (Ca2Al2SiO7); 3-cristobalite (SiO2); 4-anorthite (CaAl2Si2O8); 5-albite (NaAlSi3O8); 6-quartz (SiO2); 7-leucite (KAlSi2O6); 8-magnesium iron aluminium oxide (MgFe0.2Al1.8O4); 9-kaliophilite (KAlSiO4); 10-akermanite-gehlenite (Ca2(Mg0.5Al0.5)(Si1.5Al0.5O7)); 11-monticellite (MgCaSiO4).


Page 37 of 37

100

(a)100

(b) M agnetite

70

R elative m ass/ %

90

Q uartz

80

C ristobalite

C ordierite

F errous sulfide

O livine

70

S lag

60 50 40

F airchildite

80

R elative m ass/ %

90

A northite

30

S odium carbonate 60

C om beite

M ullite

10

S lag

50

Leucite

40 30

P otassium silicate P otassium carbonate

20

20

10

S ylvite(g)

S ylvite(s)

0

0 400

600

800

1000

1200

400

1400

600

800

(c)100

100

S apphirine

(d)

M ullite

S apphirine N epheline

80

A lbite

C linopyroxene

R elative m ass/ %

70

S lag

60 50

A northite

40

1400

90

C ordierite

80 70

1200

T em perature/ C

F errous sulfide

90

1000 o

o

T em perature/ C

30

Leucite

60

S lag

F errous sulfide

50

S pinel

A northite

40 30

S anidine 20

20

S anidine

10

S ylvite(s)

10

S ylvite(g)

0

A lbite

S ylvite(s)

S ylvite(g)

0 400

600

800

1000

1200

1400

400

600

800

F errous sulfide

N epheline

80

1400

C linopyroxene

O livine

90

1200

T em perature/ C

100

(e)

1000 o

o

T em perature/ C

70

R elative m ass/ %

R elative m ass/ %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

A northite

S lag

S pinel

60 50

S anidine

40

A lbite

Leucite

30 20 10

S ylvite(s)

S ylvite(g)

0 400

600

800

1000

1200

1400

o

T em perature/ C

Figure 6. Phase assemblage-temperature curves for ash samples: (a) CZ ash; (b) CC ash; (c) 80% CZ ash+20%PH ash; (d) 80% CZ ash+20%BS ash; (e) 80% CZ ash+20% CC ash.


Investigation on Blended Ash Fusibility Characteristics of Biomass and

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