Effect of Silica and Alumina on Petroleum Coke Ash Fusibility

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Effect of Silica and Alumina on Petroleum Coke Ash Fusibility Jiazhou Li, Xiaoyu Wang, Bing Wang, Jiantao Zhao, and Yitian Fang Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b02843 • Publication Date (Web): 27 Nov 2017 Downloaded from http://pubs.acs.org on November 27, 2017

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Energy & Fuels

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Effect of Silica and Alumina on Petroleum Coke Ash Fusibility

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Jiazhou Li,a, b Xiaoyu Wang, c Bing Wang,a, b Jiantao Zhao,*, a Yitian Fanga

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a

State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi 030001, China

4 5

b

University of Chinese Academy of Sciences, Beijing 100049, China

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c

College of Optoelectric Science and Engineering, National University of Defense

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Technology, Changsha, Hunan 410073, China

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ABSTRACT: Silica (Si) and alumina (Al) elements are always considered to be the

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important inducements for ash sintering and slagging in the boilers. The effects of

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SiO2/Al2O3 (S/A) and (SiO2+Al2O3) ratios on the synthetic petroleum coke (petcoke)

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ash fusibility are investigated in this work. Experimental methods including ash

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fusion temperatures (AFTs) tests, X-ray diffraction (XRD), and scanning electronic

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microscopy (SEM) are applied to investigate the AFTs, the mineral composition and

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surface morphologies of high-temperature ashes. Moreover, thermodynamic

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equilibrium calculations are also used to predict the ash fusion process. The results

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show that the AFTs of petcoke ash samples are closely related to the addition of S/A

17

and (SiO2+Al2O3). The dominant crystalline phases formed in high-temperature ashes

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with different S/A and (SiO2+Al2O3) are gehlenite (Ca2Al2SiO7), quartz (SiO2), nickel

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orthosilicate (Ni2SiO4), and mullite (Al6Si2O13). The AFTs drop sharply with

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increasing S/A until it reaches 1.5, which may be ascribed to the gradual decline of

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high-melting Al6Si2O13. Then, the AFTs follow a slight increase within the S/A range

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of 1.5-3.0. As (SiO2+Al2O3) increases from 20 to 60%, the AFTs show the continuous

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increase because of the formation of anorthite (CaAl2Si2O8) and Al6Si2O13 and the

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increased content of SiO2. The high-temperature ashes with the S/A and (SiO2+Al2O3) 1

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of 1.5 and 20% have the higher molten extent. Particles in these ashes are almost in

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complete agglomeration, and present the denser layer structure and more smooth

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surface.

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1. INTRODUCTION

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The production of petcoke is continuously increasing with the deep processing

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of heavy crudes in refineries [1-4]. Petcoke is generally considered as an attractive

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fuel that generates steam or power in boilers since it has some particular advantages,

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such as high fixed carbon, low ash content, and low price. In boilers, petcoke ash

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melts in whole or in part at high temperatures because of the eutectic melting of

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minerals [5-7]. The molten ash deposited on the inner wall of pipes of boilers may

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cause fireside sintering and fouling [8]. The deposited ash impedes heat transfer to

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some extent, and even blocks the flue gas channel in boilers [9,10]. Thus, choosing

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the petcoke with suitable ash fusibility is required to avoid ash sintering and fouling.

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The ash fusion behaviors are critical for the selection of petcoke and operation of

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boilers. There have been many experimental techniques focused on the evaluation of

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ash fusion behaviors [5,8,11-14], such as AFTs tests, high-temperature processing

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microscope (HTPM), and thermomechanical analysis (TMA). Among these

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techniques, AFTs tests are widely applied to guide the utilization of petcoke while

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concerning the ash fusibility. AFTs can provide not only an indication of the ash

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softening and melting behavior, but also an information of the progressive melting of

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ash to slag [15]. Four characteristic temperatures, i.e., initial deformational

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temperature (DT), softening temperature (ST), hemispherical temperature (HT), and

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flow temperature (FT), are defined by the shape variation of an ash cone at elevated

48

temperatures.

2


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The ash fusibility at high temperatures is essentially associated with the ash

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chemical composition, as well as their interactions [16]. Numerous researches have

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been performed to investigate the relationships between AFTs and ash chemical

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composition. Liu et al. [17] found that the AFTs decreased with the addition of Fe2O3

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while changing little as the K2O content increased. For the addition of CaO, the AFTs

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initially declined and then followed an increase. Wang et al. [18] pointed out that

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Na2O could decrease the AFTs markedly. van Dyk [19] studied the effects of acidic

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constituents (Si, Al, and Ti) on the ash fusibility. It was found that all acidic

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constituents had positive influences on ash flow temperature. The effect of S/A ratio

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on the AFTs was investigated by Liu et al [17]. The results indicated that AFTs had a

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decline before S/A reached 1.5, and then remained constant or increased slightly as

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S/A further increased. The formation of different melting points (MP) minerals during

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ash melting processes is generally used to interpret the variation of AFTs [20]. AFTs

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are also correlated with thermodynamic equilibrium calculations. Rizvi et al [21] used

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simultaneous thermal analysis (STA) to predict the ash fusion behavior. It was found

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that STA could assess the physicochemical changes occurred in the process of ash

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fusion, as well as the possible chemical reactions. Jak [22] put forward a new AFTs

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prediction method using equilibrium phase diagram. It was demonstrated that AFTs

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could be predicted effectively via the developed F*A*C*T* thermodynamic database.

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Although there are many researches focused on the effect of ash composition on the

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coal ash fusibility, little has been reported about the relationships between petcoke ash

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composition and the ash fusion characteristics.

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In general, the major ash composition of coal are Si, Al, Ca, Fe, K, and Na,

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whereas the petcoke ash is mainly composed of V, Ni, Si, Al, Fe, and Ca. Moreover,

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the mass percentage of V and Ni in petcoke ash is usually higher than 20 and 10%, 3


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respectively [23]. The ash compositional differences between petcoke and coal may

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cause different mineral transformation behaviors because of the presence of V and Ni

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in petcoke. We have investigated the effect of petcoke ash composition (V2O5, NiO,

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CaO, and Fe2O3) on ash fusion behaviors in previous researches [24,25]. The acidic

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ash constituents SiO2, Al2O3, and TiO2 are generally considered to act as receptors

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(network formers) and the basic oxides CaO, Fe2O3, Na2O, K2O, and MgO as oxygen

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donators

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(CaO+Fe2O3+Na2O+K2O+MgO)/(SiO2+Al2O3+TiO2), which is same as the effect of

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(SiO2+Al2O3) ratio, has been used to rank the propensity of melting, fouling, and

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slagging [27-30]. Moreover, the S/A ratio is also an important factor for the initial

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evaluations of ash fusibility [31,32]. In this work, both S/A and (SiO2+Al2O3) ratios

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are considered to characterize the influences of SiO2 and Al2O3 on petcoke ash fusion

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behaviors, which is expected to provide a guide for the efficient utilization of petcoke.

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To eliminate the impacts of impurities and complex phases in petcoke ash and

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simplify the ash system, the synthetic ash rather than real ash is selected to study the

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ash fusion process according to the literatures [17,18,33-36]. Moreover, the chemical

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composition of synthetic ash system can be controlled accurately. Thus, experimental

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samples were prepared by V2O5, NiO, SiO2, Al2O3, Fe2O3, and CaO via blending pure

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oxides. AFTs tests are carried out to identify the four characteristic temperatures of

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ash samples. XRD and SEM are combined to examine the mineral composition and

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surface morphologies of high-temperature ash samples. The ash fusion process is also

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calculated by thermodynamic equilibrium calculations via the multiple components

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system of V2O5-NiO-SiO2-Al2O3-Fe2O3-CaO.

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2. EXPERIMENTAL SECTION

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2.1. Synthetic Ash Samples.

(network

modifiers)

[26].

The

base-acid

4


ratio

R

defined

as

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The chemical composition of five petcoke ashes (Shanxi local oil refinery,

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Wuhan Petrochemical Co., Zhenhai Petrochemical Co., Zibo Qilu Petrochemical Co.,

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Ltd., and Daqing Oilfield) prepared at 973 K for 24 h [37] is shown in Table 1. Based

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on these ash composition, synthetic ash samples were prepared by V2O5, NiO, SiO2,

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Al2O3, Fe2O3, and CaO since these six constituents account for more than 93 wt% of

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petcoke ash. Table 2 lists the chemical composition of synthetic ash samples, and they

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were divided into two groups. In Group 1, (SiO2+Al2O3) and other basic oxides were

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constant while S/A varied from 0.5 to 3. In Group 2, S/A kept constant, but the total

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amounts of (SiO2+Al2O3) changed within the range of 20-60 wt%. The six analytical

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reagents were blended well by ball milling for 1 h.

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2.2. Measurements of AFTs.

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The AFTs of synthetic ash samples were measured by a AFTs tester from KY

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company, China. The tests were carried out following the Chinese standard procedure

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GB/T 219-2008 at oxidizing (air) atmosphere [38], which provided a valuable guide

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for the slagging of combustion. An ash cone with a specific geometry was heated at

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15 K/min to 1173 K, and then changed at 5 K/min to the flow temperature. In the

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procedure, the four characteristic temperatures, i.e., DT, ST, HT, and FT, were

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identified and recorded automatically with the accuracy of 1 K according to the

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variation of the certain shape of ash cone. Repeated AFTs measurements were

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performed.

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2.3. Quenching Experiments.

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Quenching experiments were performed to obtain the high-temperature ash slag

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in a tube furnace. The experimental temperature varies from 1273 to 1573 K, with the

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interval of 100 K. Figure 1 shows the schematic diagram of the tube furnace. The

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synthetic ash (1.0 g) that filled into a corundum crucible was heated according to the 5


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thermal profile of the AFTs tests. After reaching the set temperature and residence

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time (15 min) [24,39], the sample was taken out immediately, quenched in ice water,

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and then collected for testing.

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2.4. Instrumental Analysis.

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The chemical composition of five petcoke ashes was identified by X-ray

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fluorescence (XRF) spectrometry from Shimadzu, Japan with a Rh target X-ray tube

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(50 kV, 40 mA). Before testing the quenched high-temperature ash slag was ground to

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below 74 µm. The surface morphologies of the quenched slag samples were observed

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by a scanning electron microscope (JSM-7001F). Furthermore, an X-ray power

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diffractometer (RIGAKU D/max-rB) with Cu Ka radiation (40 kW, 100 mA,

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Ka1=0.15408 mm) was applied to examine the mineral composition of the quenched

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slag samples. The samples were scanned from 10 to 80° at 4° 2θ/min scanning speed

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with 0.01° step size.

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2.5. Thermodynamic Equilibrium Calculations.

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The thermodynamic software package FactSage was used to establish a multiple

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components system of V2O5-NiO-SiO2-Al2O3 -Fe2O3-CaO, which was to analyze the

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potential multiphase equilibria, proportions of liquid and solid phases in specified

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atmospheres and temperatures. In equilibrium calculations, FToxid and FactPS

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databases were selected for phase formation data. The solution species that formed

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possibly were chosen from FToxid database. However, FactSage did not have the

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database to deal with the interactions between VOx and slag [40-42]. Thermodynamic

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equilibrium calculations were performed at oxidizing (air) atmosphere under 0.1 MPa.

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FactSage was based on the Gibbs free energy minimization, indicating that the lower

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the Gibbs free energy, the higher the priority of the reaction [43]. Note that, phases

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that formed at concentrations lower than 0.01 wt% were ignored in calculations. 6


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Although FactSage is a powerful tool to calculate solid phase components and

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liquid phase change at high temperatures, there do exist some shortcomings when it is

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applied to ash fusion. It does not take into account the chemical kinetics in

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calculations. Furthermore, temperature and composition gradients during ash fusion

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are not also considered. Nonetheless, thermodynamic calculation is still a valuable

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method that provides insight into the ash fusion [44].

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3. RESULTS AND DISCUSSION

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3.1. Effect of S/A on AFTs.

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The AFTs of synthetic ash samples in Group 1 as a function of S/A is present in

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Figure 2. AFTs drop sharply with increasing S/A until it reaches 1.5 where FT drops

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to 1527 K. The reasonable explanation may be as follows: low S/A (lower than 1.0)

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results in the formation of high-melting point minerals, such as mullite. However,

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there exist no high-melting minerals when S/A reaches 1.5, which decreases the AFTs

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markedly. At higher S/A, AFTs increase gradually.

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3.2. Effect of S/A on Mineral Transformation Behavior at High Temperatures.

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The minerals interact and melt into liquid during ash fusion, causing the

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variation in minerals composition and their content. Thus, the crystal phase

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components in ash at a certain temperature can be analyzed to investigate the ash

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fusion characteristics [45]. The mineral composition of synthetic ashes with different

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S/A ratios (S/A is 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0, respectively) at 1473 K was

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investigated by XRD, as shown in Figure 3. When S/A is lower than 1.0, the

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crystalline phases are mainly Ca2Al2SiO7, SiO2, Ni2SiO4, and Al6Si2O13, of which

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SiO2, Ni2SiO4, and Al6Si2O13 have high-melting point, resulting in the high AFTs. It

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is also found that there are no diffraction peaks of V-bearing and Fe-bearing species

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in XRD patterns. V may be present as V2O5(l) because it melts at 963 K under 7


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oxidizing atmosphere, and Fe may be in the form of Fe-bearing amorphous matters.

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As S/A reaches 1.5, the diffraction peaks of mullite disappear, which may decrease

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the AFTs sharply. When S/A further increases (above 1.5), the main mineral phases

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Ca2Al2SiO7, SiO2, and Ni2SiO4 keep stable. Regarding the slight increase in AFTs, it

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may be ascribed to the increased content of high-melting SiO2.

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To further study the mineral transformation and its influence on AFTs, the

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theoretical mineral composition of synthetic ashes with different S/A ratios was

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calculated at 1473 K by thermodynamic FactSage modeling. Figure 4 shows the

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variations in theoretical mineral composition and their content of synthetic ashes.

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When S/A is 0.5, the formation of Ni2SiO4 and Al6Si2O13 does not occur through

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FactSage simulation. FactSage thermodynamic calculations just identify the possible

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chemical reactions from the perspective of thermodynamics. The reactions with small

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∆G occur more easily. Table 3 indicates that ∆G for the formation of Al6Si2O13 is

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higher than that of Ca2Al2SiO7, Ca3Fe2Si3O12, CaAl12O19, and NiCaSi2O6, which

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implies that the formation of Al6Si2O13 is unfavorable. Si exists in the form of

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Ca2Al2SiO7, and Al forms CaAl12O19 and Al2Fe2O6. Also, V2O5(l), NiO(g), and

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Fe(VO3)2 are generated according to calculation results. When S/A reaches 1.5,

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mineral phases predicted are mainly Ca2Al2SiO7, Fe(VO3)2, SiO2, and Ni2SiO4, which

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is basically consistent with the XRD results. Diffraction peaks of Fe(VO3)2 do not

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appear, this may be because Fe(VO3)2 is thermodynamically unstable. With S/A

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further increasing, the relative proportions of SiO2 and Ni2SiO4 increase gradually,

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whereas there is a rapid decline for Ca2Al2SiO7 from 49.1% (S/A is 1.5) to 30.9%

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(S/A is 3.0).

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In the process of ash fusion, mineral transformation with increasing temperature

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will influence the ash fusibility. The mineral evolution of the synthetic ash with the 8


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S/A of 1.5 from 1273 to 1573 K was determined by XRD, as shown in Figure 5. The

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ash slag between 1273 and 1373 K is composed of SiO2, Ni2SiO4, Al6Si2O13, and

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Ca2Al2SiO7. It should be mentioned that the variations of mineral diffraction peaks in

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XRD patterns are positively proportional to the change trend of mineral content

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[16,46,47]. With increasing temperature, the content of SiO2 decreases gradually since

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the diffraction peak height of SiO2 declines markedly, and its diffraction peaks

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disappear completely at 1573 K. Also, the diffraction peaks of Al6Si2O13 disappear

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when the temperature reaches to 1473 K. The reason may be that Al6Si2O13 reacts

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with other minerals, such as Fe-bearing species, to form amorphous matters.

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Ca2Al2SiO7 and Ni2SiO4 are the stable crystal phases above 1473 K.

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Phase assemblage of the synthetic ash with the S/A of 1.5 at different

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temperatures calculated by FactSage is present in Figure 6. At 1273 K, the main

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mineral phases predicted are Ca2Al2SiO7, Fe(VO3)2, V2O5(l), Ni2SiO4, and SiO2, of

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which the diffraction peaks of Ca2Al2SiO7, Ni2SiO4, and SiO2 are found in XRD

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patterns. In contrast, Fe(VO3)2 is not formed according to experimental results. With

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the temperature further increasing, Ni2SiO4 decomposes and transforms into NiO(g)

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gradually. There is a slight increase for SiO2 due to the decomposition of Ni2SiO4,

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which is contrary to the results of XRD patterns. In actual ash fusion process, SiO2

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may form some amorphous matters, leading to the decrease of SiO2. Ca2Al2SiO7

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keeps thermodynamically stable (49.1%) within the entire temperature range.

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3.3. Effect of (SiO2+Al2O3) on AFTs.

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The AFTs of synthetic ash samples in Group 2 against the addition of

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(SiO2+Al2O3) is given in Figure 7. It can be seen that the variations of AFTs are

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strongly dependent on the addition of (SiO2+Al2O3). When the addition is 20%, the

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ash sample has a relatively low AFT (FT is below 1473 K). As the addition reaches to 9


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30%, AFT shows a sharp increase, of which DT rises from 1343 to 1487 K. With the

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addition further increasing, AFTs follow a slight increase.

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3.4. Effect of (SiO2+Al2O3) on Mineral Transformation Behavior at High

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Temperatures.

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XRD patterns of synthetic ashes with different (SiO2+Al2O3) ratios heated at

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1473 K are given in Figure 8. It can be seen that crystalline phases closely resemble

230

those formed in synthetic ashes with different S/A (Figure 3), i.e., Ca2Al2SiO7,

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Ni2SiO4, SiO2, and Al6Si2O13 are the main minerals. When (SiO2+Al2O3) is 20%, the

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mineral phases consist of Ca2Al2SiO7, Ni2SiO4, and SiO2. Then, as the addition

233

reaches to 30%, the diffraction peaks of CaAl2Si2O8 appear in comparison to the

234

synthetic ashes with different S/A following the reaction:

235

Ca2Al2SiO7 +3SiO2 +Al2O3 =2CaAl2Si2O8 .

(1)

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With the (SiO2+Al2O3) further increasing to 50%, Ca2Al2SiO7, Ni2SiO4, SiO2, and

237

CaAl2Si2O8 keep thermodynamically stable, and the formation of Al6Si2O13 occurs

238

because of the increased content of SiO2 and Al2O3. With regard to the variations in

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AFTs of synthetic ashes in Group 2, the formation of CaAl2Si2O8 and Al6Si2O13 and

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the increased content of SiO2 may cause the continuous increase of AFTs.

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The theoretical mineral phases of synthetic ashes with different (SiO2+Al2O3)

242

calculated by FactSage are present in Figure 9. In comparison to the XRD results, two

243

minerals CaAl2Si2O8 and Al6Si2O13 are not predicted within the entire (SiO2+Al2O3)

244

range. But NiCaSi2O6, Fe(VO3)2, V2O5(l), and Al2SiO5 are formed through

245

calculations. There is a linear rise for Ca2Al2SiO7 from 18.2% ((SiO2+Al2O3) is 20%)

246

to 44.7% ((SiO2+Al2O3) is 50%), with a sharp decline to 34.7% ((SiO2+Al2O3) is

247

60%). The decreased content is ascribed to the formation of Al2SiO5. The SiO2 10


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content increases monotonically within the (SiO2+Al2O3) range of 20-60%. In

249

addition, Fe(VO3)2 and V2O5(l) are predicted to form, whereas no diffraction peaks of

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V-bearing and Fe-bearing species appear in XRD patterns, indicating that V and Fe

251

may be present as amorphous matters.

252

The mineral composition of the synthetic ash with the addition of 40%

253

(SiO2+Al2O3) heated from 1273 to 1573 K is given in Figure 10. The mineral

254

transformation is not influenced markedly by temperature since the mineral phases

255

SiO2, Ni2SiO4, Ca2Al2SiO7, and CaAl2Si2O8 formed in the process of ash fusion

256

remain unchanged within the temperature range of 1273-1473 K. When the

257

temperature rises to 1573 K, the diffraction peaks of CaAl2Si2O8 disappear while the

258

others keep stable. It is also found that the content of SiO2 and Ca2Al2SiO7 decreases

259

to some extent at 1573 K according to the variations of diffraction peaks of these two

260

species. The reason may be that partial SiO2 and Ca2Al2SiO7 form eutectics with other

261

minerals at high temperatures.

262

Figure 11 presents the phase assemblage of the synthetic ash with the

263

(SiO2+Al2O3) of 40% calculated from 1273 to 1573 K. It is found that the mineral

264

phases predicted are basically consistent with those from the synthetic ash with the

265

S/A of 1.5 (Figure 6). The existing discrepancy is that the formation of NiCaSi2O6

266

occurs between 1373 and 1473 K, and CaSiO3 is formed at 1573 K. On the basis of

267

simulation results, Ca2Al2SiO7 keeps unchanged (36.4%) within the temperature

268

range. CaAl2Si2O8 that detected in XRD patterns is not predicted to form. The content

269

of Ni2SiO4 decreases monotonically due to the formation of NiCaSi2O6 and NiO(g).

270

For SiO2, it shows a continuously saltatory change.

271

3.5. Surface Morphologies of Quenched Ash Samples.

11


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In addition to mineral transformation, ash fusion characteristics can be also

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reflected by the variations in surface morphologies of high-temperature ash slag

274

[48,49]. It is well known that the quenched ash can prevent crystal segregation and

275

phase transformation, and keep the high-temperature ash morphologies well [50].

276

Moreover, the high melted particles have the smooth surface and dense layer structure

277

[17]. Figure 12 shows the variations in surface morphologies of synthetic ashes with

278

different S/A and (SiO2+Al2O3) quenched at 1473 K. When the addition of S/A and

279

(SiO2+Al2O3) is 0.5 and 60%, respectively, the ashes consist of many fine and

280

irregular particles, which presents the rough surface and loose structure. As the S/A

281

and (SiO2+Al2O3) are 3.0 and 40%, respectively, fine particles have been

282

agglomerated into some large particles, and these particles show a dense layer

283

structure. When the addition of S/A and (SiO2+Al2O3) changes to 1.5 and 20%,

284

respectively, particles are almost in complete agglomeration, and the surface turns to

285

be more smooth. It is also observed that some protuberances are generated in the

286

molten surface of ash. On the basis of the preceding analyses, it is concluded that the

287

molten extent of ashes varies in the following orders: S/A=1.5 > S/A=3.0 > S/A=0.5,

288

(SiO2+Al2O3)=20% > (SiO2+Al2O3)=40% > (SiO2+Al2O3)=60%. These are same as

289

the variations of AFTs in Figures 2 and 7.

290

4. CONCLUSIONS

291

The effects of S/A and (SiO2+Al2O3) on synthetic petcoke ash fusibility were

292

investigated in this study. A series of analytical technologies including AFT tests,

293

XRD, SEM, and FactSage were applied to determine the AFTs, mineral

294

transformation, and surface morphologies of the high-temperature ashes. The main

295

conclusions are as follows:

12


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(1) The AFTs of synthetic ash samples are closely related to the addition of S/A

297

and (SiO2+Al2O3). AFTs drop sharply with increasing S/A until it reaches 1.5, and

298

then follow a slight increase. With the (SiO2+Al2O3) increasing from 20 to 60%,

299

AFTs show a continuous increase.

300

(2) The mineral transformation during ash fusion leads to the variations in AFTs.

301

The dominant crystalline phases formed in high-temperature ashes with different S/A

302

and (SiO2+Al2O3) are Ca2Al2SiO7, SiO2, Ni2SiO4, and Al6Si2O13. The decline of

303

high-melting Al6Si2O13 may cause the sharp decrease in AFTs of synthetic ashes with

304

different S/A. The formation of CaAl2Si2O8 and Al6Si2O13 and the increased content

305

of SiO2 may contribute to the continuous increase in AFTs of synthetic ashes with

306

different (SiO2+Al2O3).

307

(3) When the addition of S/A and (SiO2+Al2O3) is 1.5 and 20%, respectively,

308

synthetic ashes have the higher molten extent. Particles in these ashes are almost

309

agglomerated completely, and present the denser layer structure and more smooth

310

surface.

311

AUTHOR INFORMATION

312

Corresponding Author

313

E-mail address: [email protected]

314

ACKNOWLEDGEMENTS

315

The authors gratefully acknowledge the financial support of the National Natural

316

Science Foundation of China (No. 21576276).

317

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S.

Phase

equilibria

in

synthetic

18


coal-petcoke

slags

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fusion temperatures. Energy Fuels 2013, 27(12), 7303-7313.

Table 1. Ash Composition of Five Real Petcoke (wt %) Petcoke

V2O5

Shanxi

33.89 7.55

NiO

SiO2

Al2O3

Fe2O3 CaO

MgO

TiO2

SO3

K2O Na2O

P2O5

20.20 10.54 7.40

13.92 1.18

0.83

0.75

0.76

1.74

0.54

Wuhan

28.58 10.52 21.35 11.36 4.36

17.33 1.85

0.74

0.89

0.81

1.15

0.60

Zhenhai

29.82 12.37 25.44 7.60

10.12 8.79

1.21

0.35

1.35

0.96

0.98

0.32

Zibo

31.04 6.87

18.35 6.11

11.79 19.41 0.99

0.55

1.64

0.84

0.74

0.78

Daqing

32.35 9.75

17.74 7.04

5.35

0.64

0.97

1.35

1.05

0.61

21.35 0.74

19


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 20 of 34

Table 2. Chemical Composition of Synthetic Ash Samples composition (wt %) SiO2

Al2O3

V2 O5

NiO

Fe2O3

CaO

S/A SiO2+ Al2O3

1.1

15.33

30.67

30.00

8.00

6.00

10.00

0.5

46.00

1.2

23.00

23.00

30.00

8.00

6.00

10.00

1.0

46.00

1.3

27.60

18.40

30.00

8.00

6.00

10.00

1.5

46.00

1.4

30.67

15.33

30.00

8.00

6.00

10.00

2.0

46.00

1.5

32.86

13.14

30.00

8.00

6.00

10.00

2.5

46.00

1.6

34.50

11.50

30.00

8.00

6.00

10.00

3.0

46.00

2.1

13.33

6.67

40.00

15.00

10.00

15.00

2.0

20.00

2.2

20.00

10.00

36.00

13.00

8.00

13.00

2.0

30.00

2.3

26.67

13.34

31.00

11.00

7.00

11.00

2.0

40.00

2.4

33.33

16.67

27.00

9.00

5.00

9.00

2.0

50.00

2.5

40.00

20.00

23.00

7.00

3.00

7.00

2.0

60.00

groups

no.

Group 1

Group 2

20


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Energy & Fuels

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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

Figure 1. The schematic representation of the furnace apparatus

22


Page 22 of 34

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Energy & Fuels

Figure 2. Effect of S/A on the AFTs.

23


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

Figure 3. XRD patterns of the synthetic ashes with different S/A at 1473 K.

24


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Energy & Fuels

Figure 4. Effect of S/A on mineral transformation calculated by FactSage at 1473 K.

25


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

Figure 5. XRD patterns of synthetic ash with the S/A of 1.5 from 1273 to 1573 K.

26


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Energy & Fuels

Figure 6. Effect of temperature on mineral transformation of synthetic ash with the S/A of 1.5 calculated by FactSage.

27


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

Figure 7. Effect of (SiO2+Al2O3) on the AFTs.

28


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Energy & Fuels

Figure 8. XRD patterns of the synthetic ashes with different (SiO2+Al2O3) at 1473 K.

29


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

Figure 9. Effect of (SiO2+Al2O3) on mineral transformation calculated by FactSage at 1473 K.

30


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Energy & Fuels

Figure 10. XRD patterns of synthetic ash with the (SiO2+Al2O3) of 40% from 1273 to 1573 K.

31


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

Figure 11. Effect of temperature on mineral transformation of synthetic ash with the (SiO2+Al2O3) of 40% calculated by FactSage

32


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Energy & Fuels

S/A=0.5

Si+Al=60%

S/A=3.0

Si+Al=40%

S/A=1.5

Si+Al=20%

(a)

(b)

33


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

Figure 12. SEM photomicrographs of synthetic ashes with different S/A (a) and (SiO2+Al2O3) (b) at 1473 K.

34


Page 34 of 34

Effect of Silica and Alumina on Petroleum Coke Ash Fusibility

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