Ash Fusion Temperatures Research Articles

Low temperature combustion and ash deposition characteristics of palm oil and forest replanting waste

This study evaluation and analysis the low-temperature combustion characteristics and ash deposition of palm oil waste, including palm kernel shell (PKS) and empty fruit bunch (EFB), as well as forestry waste in the form of rubber wood (RBW) and replanting waste (RPW). The experiments were conducted using a drop tube furnace at 900 ᵒC, which is considered a low temperature compared to the operating temperature of pulverized coal. The thermogravimetric method (TGA) was applied to understand the combustion properties of the biomass, while the ash deposition tendency was assessed through empirical calculations, combustion experiments, and direct observation of the ash produced. The results showed that RBW had the best combustion performance compared to the other samples. Although RPW has the highest ash fusion temperature value among all samples, with a value above 1200 ᵒC, the low-melting-point mineral phase such as fairchildite, produced at low-temperature combustion at 24.74%, increases the risk of ash sticking to metal surfaces. PKS and EFB produce very high albite mineral content of more than 60%, which has a low melting point and could potentially cause ash deposition problems. On the other hand, RBW, with a dominant content of SiO2 (21.79%), Al2O3 (20.24%), and MgO (8.03%), produces minerals dominated by quartz at up to 78% and magnesioferrite at more than 5%, both of which have a high melting point that tends to produce harmless ash. These findings provide insight into the potential of utilizing biomass in low-temperature combustion processes, which is a way of reducing waste and lowering greenhouse gas emissions.

In-situ ash sintering process analysis during the co-combustion of the coal gasification fine slag and corn straw

The co-combustion of coal gasification fine slag (CGFS) and biomass is proposed to enhance the poor combustion characteristic of CGFS and alleviate the ash-related issues of biomass. In this study, the sintering mechanism of CGFS ash (FA) and corn straw ash (SA) was revealed by in-situ image analysis and thermodynamic modelling. The sintering process of FA includes initial sintering stage (S1), holding stage (S2), and primary melting stage (S3). The S1 is initiated by the flow of the low-viscosity slag, whereas the subsequent S2 and S3 stages are predominantly governed by the crystallization and then the melting of anorthite with increasing temperatures, respectively. The AAEMs in SA loosens the structure of FA, thereby facilitating the onset of S1 at a low temperature. Concurrently, the anorthite is gradually converted to diopside, which possesses a lower melting point, and subsequently into sanidine, which exhibits a higher melting point. This transformation extends the temperature range across S1 and S2, leading to an initial decrease followed by an increase of ash fusion temperatures with the SA addition. The dry bottom boiler suits for the co-combustion of CGFS and corn straw and the boiler exit temperature is suggested to be higher than 968 °C.

Ash characteristics investigation from co-firing of Calliandra calothyrsus and Gliricidia sepium with a high-sulfur and -iron coal in drop tube furnace

Calliandra calothyrsus and Gliricidia sepium ash characteristics as co-firing fuel to high-sulfur and -iron coal were investigated through theoretical prediction, FactSage modelling, and combustion experiment in drop tube furnace. The results show that the addition of Calliandra and Gliricidia were able to mitigate the slagging risk according to theoretical prediction and FactSage modelling. Slag formations were predicted to occur at higher combustion temperature compared to coal which was reflected in higher ash fusion temperature. The results of combustion experiment showed an agreement with less ash deposition and cleaner probe surface. The addition of Calliandra and Gliricidia increased the high-melting minerals and decreased Fe-based minerals. However, domination of Ca2SO4 in addition of 25 wt% Gliricidia can be detrimental with presence of strongly adhered ash and material degradation. This research provides an important insight of Calliandra and Gliricidia utilization as co-firing fuel that improve the ash characteristics of high-sulfur and -iron coal.

Co-melting mechanisms for municipal solid waste incineration fly ash with fine slag from coal gasification and coal gangue

Vitrification is a promising treatment for municipal solid waste incineration fly ash (MSWI-FA); however, high energy consumption due to the high MSWI-FA fusion temperature limits the development and application of this technique. In this study, fine slag ash (FSA) derived from coal gasification and coal gangue ash (CGA) were mixed with MSWI-FA to reduce the ash fusion temperature. The transformation of minerals in ash during thermal treatment was examined via X-ray diffraction and thermodynamic equilibrium calculations. The ash flow behaviour was observed using a thermal platform microscope, and the silicate structure was quantified using Raman spectra. The co-melting mechanisms for the mixed ash were systematically investigated. Results indicate that the flow temperature (FT) of the mixed ash exhibited an initial decrease and subsequent increase as a function of the addition ratio of FSA or CGA. Lowest ash FT of 1215 °C and 1223 °C were recorded for addition of 50% FSA and 50% CGA, respectively; further, these temperatures were lowered by > 285 °C and >277 °C respectively, relative to FT of the MSWI-FA. The transformation of minerals and silicate structure during mixed ash heating was responsible for the variation in the ash fusion temperature. CaO in MSWI-FA tended to react with mullite, quartz and haematite in FSA and CGA, forming minerals such as anorthite, gehlenite, and andradite with relatively low melting points. The addition of FSA or CGA caused changes in the silicate network structure of the mixed ash. In particular, 50% FSA incorporation caused the transformation of Q4 and Q3 to Q2, whereas 50% CGA introduction resulted in the conversion of Q4 and Q2 into Q3 and Q1 + Q0, respectively. The silicate network depolymerised, causing reduction in the ash fusion temperature and increasing the melting rate.

Effect of High Calcium and High Iron Coal on Ash Fusion Characteristics of Petroleum Coke during Cogasification.

Entrained flow gasification provides a more efficient utilization method for high-sulfur petroleum coke. The operation temperature of the entrained flow gasifier must be above the ash fusion temperature (AFT) of petroleum coke due to the liquid slag discharge. In this work, petroleum coke was blended with high-calcium coal and high-iron coal, respectively, under a reducing atmosphere, and the variations in AFTs were recorded by an ash fusion temperature analyzer. The influence of mineral transformations on the ash fusion characteristics of blended ash was analyzed by X-ray diffraction and FactSage. The results showed that both high calcium coal and high iron coal could efficiently reduce the AFTs of petroleum coke. When the ratio of high calcium coal and high iron coal reached 60 wt %, the corresponding flow temperature (FT) of mixed ash decreased to 1225 and 1312 °C, respectively. With the content of high calcium coal increasing, coulsonite (FeV2O4), vanadium trioxide (V2O3) and nickel (Ni) with high-melting points tended to decrease, causing the decrease of AFT for mixed ash. As high iron coal was added, Ni and V2O3 continuously kept decreasing. In particular, the percentage of FeV2O4 first increased and thereafter decreased with high iron coal above 40 wt %.

Co-combustion of municipal sewage sludge and food wastes-derived anerobic digestates: Combustion characteristics, HCl/NO/SO2 emission and ash behaviors

Co-combustion of sewage sludge (SS) and food wastes-derived anerobic digestate (AD) is a promising way of waste-to-energy. Therefore, it is crucial to examine their combustion performance, ash behaviors, and gaseous pollutants emissions during the combustion of AD-SS blends using a thermogravimetric analyzer and a tube furnace combustion system. Results show that obvious interactions between AD and SS are observed in their co-combustion process. In terms of comprehensive combustion index, co-combustion can improve their combustion performance with the decrement of burnout temperature and enhanced combustion reactivity. Higher blending ratio of AD favors the increment of their ash fusion temperature, i.e., from 1109 to 1403 °C for deformation temperature due to the formation of high melting point minerals (i.e., Ca9Fe(PO4)7, 2CaO·Al2O3·SiO2). Significant in-situ reduction of NO and HCl as well as self-desulfurization is observed during the combustion of AD-SS blends. Compared to the theoretical values, the emission amount of HCl, NO, and SO2 is reduced by 0.13, 1.39, and 0.35 mg·g−1, respectively at 850 °C and blending ratio of AD to SS = 0.75:0.25. These phenomena are associated with the reducing environment and reducing substances by their high volatiles as well as the abundant minerals such as CaCO3 and Fe2O3 in AD and SS. However, high combustion temperature is unfavorable for chlorine fixation. This work provides a better understanding of their thermal behaviors, ash characteristics, and gaseous pollutants emission characteristics to realize their stable and clean incineration.

Investigation of Slagging-Fouling and Mineral Contents in Low-Rank Coals for Improved Combustion Performance

ABSTRACT Despite the problems associated with low-rank coal, this type of coal is still widely used in various applications including the power generation sector. In this study, three low-rank coals (LRC) with high mineral content of SiO2, Al2O3, and MgO were selected and comprehensively investigated. Investigations include ash fusion temperature (AFT), theoretical calculation, combustion experiment with drop tube furnace (DTF), and ash analysis using scanning electron microscope (SEM) and x-ray diffraction (XRD). The investigation revealed that T-Coal with high SiO2 and P-Coal with high Al2O3 mineral produce ash deposition which did not adhere on the probe surface of either slagging or fouling area. T-Coal ash consists of fine and solid particles, but the presence of the dominant albite mineral, 29.09% in slagging probe and 28.71% in fouling probe, may have a negative impact on ash deposition. P-Coal ash is dominated by fine particles with a predominance of quartz and other high-melting minerals. A-Coal with high MgO mineral has good results in slagging aspects. However, the high Fe2O3 on A-Coal results in low ash fusion and produces more hematite mineral (17.70%) in the fouling probe. This study shows that several types of LRC have good evaluation on ash-related problems which potentially can be used as coal blending for further utilization in power generation.

Investigation on ash fusion characteristics and mineral transformation mechanism of sorghum straw by paper-making sludge addition

The co-combustion of sorghum straw and paper-making sludge (PMS) is beneficial to alleviate the ash-related problem in sorghum straw combustion process. In this paper, the mineral migration and transformation behavior in sorghum straw ashes with the addition of PMS ashes under an oxidizing atmosphere were investigated using an X-ray diffractometer, thermogravimetric-derivative thermogravimetric, scanning electron microscopy-energy dispersive X-ray detector, and FactSage software. The results demonstrated that the increase in the PMS ash mass ratio led to an increase in ash fusion temperature (AFT) of sorghum straw mixtures. The generations of high melting-point (MP) calcium feldspar (e.g., Ca2MgSi2O7, Ca2Al2SiO7, Ca3MgSi2O8, and Ca7Mg (SiO4)4) and phosphates (e.g., Ca3P2O8, Ca5P2SiO12, and Ca7P2Si2O16) caused the increases in the AFT. The maximum weight loss of sorghum straw ashes decreased with the increasing PMS ash mass ratio, and the surface of the ashes underwent the transition from smooth to a whole loose and rough, which alleviated the ash-related problems of sorghum straw. The addition of PMS ashes decreasing the liquid-phase content calculated by FactSage at the same temperature also explained the sorghum straw AFT increase. The changes of AFT and its corresponding mechanisms in the sorghum straw with PMS ash addition under an oxidizing atmosphere provided the support for large-scale combustion of biomass.

Ash melting behaviors of high-sodium coal and its co-combustion with coal gangue to inhibit slagging

Fouling and slagging are major challenges that impede the clean and efficient use of high-sodium coals (HC) for power generation. To address these persistent issues, this study examined the impact of sodium (Na) on ash-melting behaviors and assessed the feasibility of mitigating fouling and slagging through the co-combustion of HC with coal gangue (CG). The mineral transformation mechanisms were analyzed through experimental and thermodynamic calculations using the FactSage software. The potential for inhibiting slagging through the co-firing of HC with CG rich in silica (SiO2) and alumina (Al2O3) was also investigated. The presence of Na-containing species led to the formation of more flexible minerals and lowered the ash fusion temperatures (AFTs). Na not only decreased the initial temperature required for the formation of the liquid phase but also increased the proportion of the liquid phase during high-temperature ash-melting processes. Co-firing with CG rich in silica and alumina significantly improved the AFTs of HC. Furthermore, this approach effectively reduced the propensity for fouling and slagging. In practice, it is recommended to control the co-firing ratios of CG within 10–30% to inhibit slagging and fouling issues while maintaining a smooth boiler operation.

Regulation Mechanism of Ash Fusion of Iron‐Rich Coal in Xinjiang with Different Additives

AbstractTo realize the high‐efficiency utilization of iron‐rich coal (ZC), it is necessary to conduct in‐depth research on its ash fusion characteristics and regulation mechanism. In this paper, the fusion temperature test of ZC coal ash was first carried out in a weak reducing atmosphere, and diatomite (GZT) and Naomaohu high‐calcium coal (NMH) were selected as additives. The results show that the four characteristic temperatures of ZC coal ash are all low under weak reducing conditions. The addition of NMH ash lowered the fusion temperature of ZC coal ash, while the GZT ash increased the fusion temperature to varying degrees. When the addition ratio of NMH ash is less than 40 %, the effect of increasing the difference between the deformation temperature and flow temperature of ZC coal ash is still positive. The addition of NMH ash made the slag system generate a high content of calcium‐magnesium feldspar and calcium‐iron feldspar, decreasing the fusion temperature of the blended coal ash. The addition of GZT ash increased the content of SiO2 in the slag system and promoted the increase of the iron‐pyroxene content, and the formation of the iron‐aluminum pyroxene and cordierite mineral phases, thereby increasing the coal ash fusion temperature.

Investigation of ash fusion characteristics on co-combustion of coal and biomass (straw, sludge, and herb residue) based on experimental and machine learning method.

Co-combustion of coal and biomass has the potential to reduce the cost of power generation in plants. However, because of the high content of the alkali metal of biomass ash, co-combustion of these two fuels leads to unpredictable ash fusion temperature (AFT). This study conducted experiments to measure the AFT of straw, sludge, and herb residue when they were blended with coal at different ratios. Additionally, a machine learning algorithm called tuna swarm optimization (TSO) was employed to optimize the support vector regression (SVR) model to predict the softening temperature (ST) of samples. The results indicate that straw and sludge were found to be suitable for blending in small proportions, while herb residue was suitable for blending in larger proportions. In comparison to the traditional grid search optimization model, the TSO algorithm significantly enhances the prediction accuracy of both training and test sets, and improves the generalization ability of SVR.

A machine learning framework for intelligent prediction of ash fusion temperature characteristics

The characteristics and analysis of coal ash fusion have always been a challenge in coal research. In this study, a hybrid data-based machine learning framework was developed and used to classify coals based on ash fusion temperature. Three main machine learning classification models, namely the Gaussian Naive Bayes (GaussianNB), Random Forest (RF) and Extreme Gradient Boosting (XGBoost), were used in this study, while three commonly used classification metrics were applied to optimize the model. In addition, the SHapley Additive exPlanations (SHAP) method was employed to interpret the selected machine learning models. The results showed that the RF and XGBoost models provided better simulation and prediction results, with all classification metrics exceeding 0.9. Among the models, for the smaller dataset, the RF model provided better simulation results with weighted accuracy (WA), unweighted average recall (UAR) and F1 score (F1) of 0.93, 0.93, and 0.95, respectively. Based on the SHAP analysis, Al2O3, SiO2 and CaO showed the most significant influence on classifications by low ash fusion temperature (LAFT) and medium ash fusion temperature (MAFT) coals. In particular, Al2O3 and SiO2 showed a negative correlation in LAFT classification, while CaO presented a positive correlation. These features had an opposite effect on the classification prediction of MAFT. However, Fe2O3 had a significant negative correlation effect on the classification of high ash fusion temperature (HAFT), second only to Al2O3. In summary, the hybrid data-driven machine learning framework is able to build a classification model of coal ash fusion characteristics with high accuracy based on features such as ash composition and ash fusion temperature. It can also perform in-depth analysis of the model based on the interpretation tool, which ultimately helps to facilitate the analysis of coals.

TWO-STAGE PALM KERNEL SHELL WASHING WITH WATER AND ACETIC ACID AS PREPARATION OF CO-FIRING SYSTEM WITH COAL

Palm kernel shells (PKS) were washed with water and glacial acetic acid (CH3COOH) gradually to prepare them for co-firing with coal. They were then torrefied at 450ºC for one hour. Washing was done to reduce the concentration of ash and alkaline oxides, which would reduce the chance of slagging and fouling. The research was conducted considering that information about washing the PKS with acetic acid and then having them torrefied is very limited and unclear. The results showed that washed and torrefied PKS had better characteristics than those of raw PKS or PKS washed with water. PKS that is washed with acid, torrefied and then blended with coal has low slagging and medium fouling tendencies. However, based on ash fusion temperature, the inclination towards slagging and fouling is high under reducing conditions and medium under oxidation conditions.

Effects of phosphorus on the fusion characteristics of synthetic ashes with different Al2O3/CaO ratios

In this paper, five series of synthetic ashes with different Al2O3/CaO ratio mass ratios were prepared, and the ash fusion temperatures (AFTs) of the samples with different percentages (5–20 wt%) of phosphorus pentoxide (P2O5) added were measured under a mild reducing atmosphere to study the effect of phosphorus on the fusion characteristics of the ashes in different compositions. X-ray diffraction (XRD), thermodynamic equilibrium calculations, and high-temperature heating stage microscopy (HHSM) were used to investigate the mechanism of phosphorus in changing the fusion characteristics of the ash. The results showed that the addition of P2O5 produced the least effect on AFTs of samples with an Al2O3/CaO ratio of 6:4. For lower Al2O3/CaO ratios (classified as peralkaline), the addition of P2O5 caused a decrease-increase-decrease trend in AFTs, while for higher Al2O3/CaO ratios (classified as peraluminous), the AFTs of samples were decreased by phosphorus. The stronger affinity of P2O5 for CaO and Al2O3, compared to that of SiO2, was noticed and led to a shift of main minerals in the slag from silicates to phosphates and to the isolation of SiO2. In addition, the phosphorus-bearing samples followed the same “melt-dissolution mechanism” as the phosphorus-free samples.

Effecting mechanisms of iron-rich sludge on ash fusion characteristics of coal with high ash fusion temperature under reducing atmosphere

Co-gasification is crucial for large-scale clean conversion of coal and sludge. In this study, the effects of municipal sewage sludge (MSS, Fe2O3:48.11 %) and pharmaceutical sewage sludge (PSS, Fe2O3: 67.80 %) on ash fusion temperature (AFT) of high AFT Xiangyuan coal (XY) were explored using an AFT analysis, X-ray fluorescence spectrometry, X-ray diffraction, scanning electronic microscopy, and thermodynamics FactSage calculation. The results showed that when MSS or PSS ash mass ratios reached 20 % or 16 % (for XY mixtures, the mass ratio of MSS or PSS should be >5.81 wt% or 5.07 wt%), respectively, the AFT met the requirement of liquid-slag discharge for entrained-flow bed gasification. Under a reducing atmosphere (6:4, CO/CO2, volume ratio), Fe2+ destroyed the bridging-oxygen bonds in the network structure and generated low melting-point (MP) hercynite (FeAl2O4). This resulted in the AFT decreases in the XY mixtures with the additions of PSS or MSS. Meanwhile, the high calcium content (CaO: 13.40 %) easily reacted with Al2O3 and SiO2 and formed anorthite (CaAl2SiO8), which inhibited high-MP mullite formation and decreased the mixed XY AFT. With the increasing SS mass ratio, the surface of the ash sample and thermodynamic FactSage calculation were in good agreement with the experimental results.

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

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

PM10 emissions from co-combustion of water washed sea rice waste with coal

Sea rice is a variety of salt-tolerant rice that absorbs significant quantities of Na, K and Cl. This work investigated effects of water washing pretreatment on sea rice waste properties, such as combustion characteristics, particulate matters (PM) emission and PM10 reduction, during its co-combustion with coal. Fuel characterizations, thermogravimetric analyses, ash fusion temperature (AFT) measurements and PM10 collection experiments were performed. A drop tube furnace was used to burn biomass and blended fuel samples at 1500 °C for PM10 collection. The results show that water washing effectively removed undesirable elements, including K, Na, and Cl. The washing pretreatment increased the AFTs of sea rice straw and ordinary rice straw, but had no effect on the husk. The washing delayed the devolatilization of sea rice waste, as did the char combustion. The yield of PM1 from the washed biomass was significantly reduced owing to the extraction of alkali metals and Cl. During co-combustion with coal, the ash particles of biomass could capture the alkali sulfides from coal, which inhibited the formation of PM1. Ca-containing particles in coal could melt and adhere to the large ash particles from the biomass to grow into larger particles, reducing the yield of PM1–10.

Ash fusion behavior modification mechanisms of high-calcium coal by coal blending and its ash viscosity predication

In this paper, the ash fusion temperature (AFT) modification of high calcium Huolinhe lignite (HLH) with the addition of high aluminum Datong coal (DTC) and their corresponding mechanisms were investigated by an AFT tester, X-ray diffractometer, Raman spectrometer, and FactSage software. The AFTs of HLH mixtures increased gradually with the increasing DTC mass ratio due to their corresponding decrease in the total basic oxide content of CaO, MgO, Fe2O3, Na2O, and K2O. The formations and content increases of high melting-point minerals (anorthite, cordierite, and mullite), the gradual decrease in the ratios of no bridging-oxide bond/bridging-oxide bond (NBO/BO), and an increase in the R (R = (Q3 + Q2)/(Q1 + Q0)) value resulted in the increases in the AFT and ash viscosity. Considering the variations in the characteristics of AFT and ash viscosity, the 40.0–50.0 % DTC mass ratio might be suitable for HLH entrained-flow bed (EFB) gasification. The combination of AFT measurement and ash viscosity predication using FactSage provided a simple method to determine whether ash characteristics of coal were suitable for EFB gasification.

Correlation between Flow Temperature and Average Molar Ionic Potential of Ash during Gasification of Coal and Phosphorus-Rich Biomass

The co-gasification of biomass and coal is helpful for achieving the clean and efficient utilization of phosphorus-rich biomass. A large number of alkali and alkaline earth metals (AAEMs) present in the ash system of coal (or biomass) cause varying degrees of ash, slagging, and corrosion problems in the entrained flow gasifier. Meanwhile, phosphorus is present in the slag in the form of PO43−, which has a strong affinity for AAEMs (especially for Ca2+) to produce minerals dominated by calcium phosphates or alkaline Ca-phosphate, effectively mitigating the aforementioned problems. To investigate the changing behavior of the slag flow temperature (FT) under different CaO/P2O5 ratios, 72 synthetic ashes with varying CaO/P2O5 ratios at different Si/Al contents and compositions were prepared, and their ash fusion temperatures were tested. The effects of different CaO/P2O5 ratios on the FT were analyzed using FactSage thermodynamic simulation. A model for predicting slag FT at different CaO/P2O5 ratios was constructed on the basis of the average molar ionic potential (Ia) method and used to predict data reported from 19 mixed ashes in the literature. The results showed that Ia and FT gradually increased with a decreasing CaO/P2O5 ratio, and the main mineral types shifted from anorthite → mullite → berlinite, which reasonably explained the decrease in ash fusion temperatures in the mixed ash. The established model showed good adaptability to the prediction of 19 actual coal ash FTs in the literature; the deviation of the prediction was in the range of 40 °C. The model proposed between FT and Ia based on the different CaO/P2O5 ratios can be used to predict the low-rank coal and phosphorus-rich biomass and their mixed ashes.

Understanding impacts of introducing CO2 in N2 and operation conditions on physicochemical property and fusion behaviour of solid products during thermal decomposition of corn stalks

The total annual production of corn stalk (CS), a byproduct of corn processing, in China was as high as 3.1 × 108 tons, the utilization of which had great potential. The objective of this study was to investigate the characterization of the resulting solids during thermal conversion of CS under different atmospheres and to deepen the understanding of the effects of introducing CO2 in N2. The impacts of temperature, atmosphere, and particle residence time on the solid yield, ash characteristics were elucidated. It was found that the solid yields decreased with increasing temperature. For a given temperature below 600 °C, the solid yields in 20% CO2/80% N2 were higher than those in N2. But when the temperature was above 600 °C, the opposite trend was observed. Increasing residence time substantially improved carbon conversion. Compared with the solids formed below 600 °C, the 800 °C solids contained more agglomerates, which were composed of K-bearing and Ca-bearing minerals. The ash fusion temperature (AFT) increased with rising pyrolysis/gasification temperature. After substituting N2 with CO2 in the pyrolysis agent, the AFT became higher. Under the current conditions, ash deposition could occur even if the operating temperature was lower than the softening temperature (ST) due to the formation of low melting eutectics.