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Graphical abstract Highlights • Composite conditioners can reduce NH 3 and HCN generation at each stage. • The synergy on NO x precursors reduction in homogeneous stage accounted for 50.59–98.76% of final decrement. • Nitrile-N and pyrrole-N in char converted to indole-N in tar with iron-catalyzing in heterogeneous process. • Both char-N and tar-N can be decomposed to N 2 in the existence of CaO. Abstract Fenton's reagent (Fe2+ + H 2 O 2) and CaO are the conditioners during sludge dewatering, which also showed abilities in NO x precursors control during drying and pyrolysis process that we have found before. This study further refined the effects of conditioners on homogeneous and heterogeneous processes during sludge steam gasification using a self-designed decoupling reactor. The results show that compared with raw sludge, the NH 3 and HCN yields of conditioned sludge decreased by 13.71–17.67 mL/g and 17.77–23.45 mL/g at 873–1073 K respectively. 50.59–98.76% of decrement attributed to the synergistic effect of conditioners on volatiles homogeneous reforming, owing to the less NH 3 , HCN and tar-N yields in devolatilization product as well as the indirect enhancement of HCN hydrolysis. Fenton's reagent added alone exhibited a significant effect on volatiles heterogeneous reforming. During the interaction between volatiles and char, iron salts could catalyze the nitrile-N and pyrrole-N in char conversion to stable indoles in tar and inhibited the hydrolysis of amine-N to release NH 3. Calcium salts also showed a certain capability on the co-decomposition of quaternary-N in char and indoles/quinolones in tar to harmless N 2. Thus, the combination of Fenton's reagent and CaO can complementarily reduce the emission of NO x precursors at each stage of gasification. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new method of kaolin modification was developed to improve Na adsorption. • The Na adsorption efficiency increased from 3.54 to 4.62 mg g−1 during combustion. • The combined method contributed to the highest degree of disorder of structure. • During the modification of kaolinite, Al (VI) turned into Al (V)/Al (IV). • The amorphous and unstable Al (V)/Al (IV) provided active sites for Na fixation. Abstract The thermal utilization of low-rank coal with high sodium content easily leads to severe fouling and slagging in actual boilers. To alleviate this problem, a combined method of thermal pre-activation and intercalation-exfoliation was developed in order to modify the kaolinite and thus control the release of sodium vapor during the combustion of Zhundong coal. The results show that the sodium capture efficiency of kaolinite increased from 3.59 mg g−1 to 4.62 mg g−1 when employing the combined modification method. This modified kaolinite can be used more effectively, alleviating fouling and slagging in actual boilers that burn high sodium solid fuels. The experimental data regarding the crystal structure, functional groups, Si/Al-coordination and micromorphology of kaolinite indicate that two modification methods had different effects on the structure of kaolinite, which were closely associated with the sodium adsorption capacity of the modified kaolinite. By thermal pre-activation, metakaolinite formed after dehydroxylation, resulting in the hexa-coordinated Al (VI) being converted to unsaturated Al. During the process of intercalation-exfoliation, the lamellar structure of kaolinite was broken, leading to a decrease in its crystallinity. The combining method contributed to the highest degree of structural disorder and promoted the conversion of Al (V) to Al (IV), thus creating more active sites for sodium fixation. In this case, the chemical sodium adsorption efficiency of kaolinite increased significantly regardless of the purity of raw kaolinite and the temperatures of pre-calcination. Based on a multistage analysis of the modified kaolinite, a relationship between the structure and adsorption capacity was developed, providing a new method of adsorbent modification. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Modification improved Na adsorption capacity of kaolinite in the combustion of Zhundong coal. • The Na adsorption capacity of modified kaolinite increased by 39% at 800 °C. • The formation of crystal SiO 2 and mullite was totally and partially inhibited after modification. • Modification increased the application temperature window of kaolin by at least 150 °C. • Al (V) content is proved to connect the adsorption capacity and thermal conversion of kaolinite. Abstract Kaolin is often utilized as an additive to relieve fouling and slagging problems in boilers. In a previous work of the authors it was successfully employed the modification of intercalation-exfoliation method to improve the adsorption capacity of kaolinite at 1000 °C, and this work aimed to investigate the best adsorption performance and corresponding application temperature of modified kaolinite at different temperatures. The adsorption experiment with Zhundong coal was conducted from 650 °C to 1200 °C. The thermal behavior of modified kaolinite was characterized over a wide temperature range to reveal the mechanism from the perspective of structural change. Results showed that modified kaolinite exhibited the best adsorption performance at 800 °C, with the adsorption capacity increasing by 39% after modification. The effect of modification on kaolin was also reflected in the thermal behavior. About 43% of the hydroxyl groups were removed via modification, the amount of mullite above 1100 °C approximately decreased by 38%, and the expulsion of crystalline SiO 2 was totally inhibited by modification, suggesting that modification affected the reconstruction of Si/Al-related compounds at high temperature. In addition, the enhanced yield of unsaturated Al (V) at 800 °C after modification was totally consistent with the improved adsorption capacity of modified kaolinite at 800 °C. It is concluded that kaolinite can be used at higher temperature with improved adsorption capacity through a modification of intercalation-exfoliation method, which was presumably related to the greater content of 5-coordinated Al in modified kaolinite. Moreover, this discovery indicated that Al (V) content might be a useful index for the selection of various aluminasilicates as efficient adsorbents in furnace. [ABSTRACT FROM AUTHOR]

[Display omitted] • Corrosion resistance of coating was tested for 2700 h in a 400 t/d MSW incinerator. • HVOF-NiCr coating can reduce the corrosion rate of superheater by 60–80%. • There is coupling effect between deposits and acidic gases on high-temperature corrosion. • The coupling corrosion process is dominated by deposits based on kinetic analysis. • Formation of spherical Ni oxides was the key to relieve corrosion by HVOF-NiCr coating. Municipal solid waste (MSW) incineration technology have developed rapidly for the achievement of waste disposal and energy conversion. However, the contents of alkali salts especially chlorides are much higher than traditional solid fuels such as coal and biomass, resulting in severe high-temperature corrosion. High-velocity oxy-fuel spray (HVOF) coating is a promising method, while the complex corrosion process involving flue gas and deposits was still unclear. In this study, the in-service performance and coupling corrosion mechanism was investigated. After the 2700 h of in-situ experiments in a 400 t/d MSW incinerator, thickness loss of bare high temperature superheater was 1.9 times that of bare low temperature superheater. For coated superheater by HVOF-NiCr coating, the layered Cr, Mo and Ni oxides was successively formed during the corrosion process, contributing to an 80 % reduction in the thinning rate. In order to further investigate the corrosion mechanism induced by deposits and flue gas, the decoupling analysis of corrosion kinetics and in-stage characterization was conducted based on the lab-scale experiments. Results showed that a two-stage linear fitting was appropriate, theoretically confirming that the coupling corrosion reaction is dominated by deposits. HCl and SO 2 can significantly accelerate the deposits-induced corrosion by about 10 times, through promoting the inward penetration of chlorine and oxidation. The resistance of HVOF-NiCr coating against corrosion can be divided into two stages. In the first 10 h, the growth of spherical nickel oxide with continuous oxygen intake resulted in a quick mass gain rate of 1.18 mg·cm−2·h−1. Subsequently, the corrosion rate significantly decreased to 0.086 mg·cm−2·h−1 due to the formed oxide layer. This study provided a new insight into the coupling corrosion caused by flue gas and deposits through kinetic analysis, and the resistance of HVOF-NiCr coating was clarified through the staged characterization. [ABSTRACT FROM AUTHOR]

Biomass pretreatment is still a major challenge for improving bioethanol production. The performance of two alkaline-mechanical pretreatments, alkaline twin-screw extrusion (ATSE) pretreatment where both alkaline treatment and refining occur simultaneously and alkaline pretreatment followed by PFI refining (APR), was compared in pretreating corn stover for fermentable sugar production at the same pretreatment conditions: 99 °C for 1 h with alkali to biomass ratio of 0.06 g NaOH/g oven-dry corn stover and a 1:2 biomass-to-liquid ratio. The enzymatic hydrolysis efficiency of glucan and total sugar yield of ATSE-treated samples was 87.47% and 78.75% compared to 64.80% and 54.83% of APR-treated samples (alkaline pretreatment with the supplement of 10000 revolutions refining) with a cellulase loading of 20 FPU/g for 48 h. X-ray diffractometer (XRD), and scanning electron microscopy (SEM) explained why ATSE pretreatment obtained the satisfied total sugar yield with low temperature and high biomass/liquid ratio and also demonstrated ATSE pretreatment was an effective method for improving enzymatic hydrolysis rate of corn stover. [ABSTRACT FROM AUTHOR]

CaO is a traditional desulfurizer used in coal combustion, and it is also a widely applied chemical conditioner in sewage sludge dewatering. In this study, the feasibility of co-combustion of CaO-conditioned sludge (Sc-CaO) and coal was discussed, including combustion characteristics and gas pollutants emission. The results show that adding 30% Sc-CaO into co-combustion strengthened the procedure of devolatilization and volatiles combustion (220–380 °C). But the main combustion performance (430–600 °C) was still similar to that of coal. Conditioner CaO could capture almost all the SO 2 during sludge mono-combustion and 15.8–48.4% of SO 2 during co-combustion. Meanwhile, conditioner CaO also contributed to N 2 O catalytic reduction and mitigated the NO increase caused by the co-effect of raw sludge and coal at 900 °C. Compared with physical additive CaO, conditioner CaO distributed evenly in sludge matrix and partially bonded to carbon, which was benefit to SO 2 adsorption and N 2 O reduction. At the same time, the increase of NO was more mild than that caused by physical additive CaO. This study shows that co-combustion of Sc-CaO and coal is a suitable and promising technology for clean disposal of sewage sludge. [ABSTRACT FROM AUTHOR]

The gas (mainly NO and SO 2 ) emission and ash characteristics from combustion of high ash content antibiotic mycelial residue (AMR) rich in N and S were investigated using a laboratory scale fluidized bed combustor, and the effects of addition of water vapor studied at the same time. The tested combustion temperature, excess air ratio (α) and mass ratios of water vapor-to-fuel (WV/F) varied in 750–950 °C, 1.3–1.9 and 0.4–1.4, respectively. Without additional water vapor present, both the concentrations of NO and SO 2 in flue gas increased with elevating combustion temperature and excess air ratio, corresponding to the increases in conversion ratio of fuel-N to NO and emission ratio of S. The addition of water vapor facilitated excavating organic matters in the ash to result in its lower C and N contents. Additional water vapor formed partial reducing atmospheres, which were characterized by high CO and H 2 concentrations in combustion atmosphere and low valence S in the ash, to thus visibly reduce NO. The SO 2 concentration became slightly lower at the presence of additional water vapor and further decreased with more water vapor addition. Additional water vapor strengthened capture of SO 2 by the ash. Higher WV/F ratios led to more porous structures in ash, accountable for NO reduction by catalytic effect as well as SO 2 absorption. Nevertheless, it seems less possible to reduce NO and SO 2 concentrations to meet their respective emission criteria, and other measures will thus have to be taken to control their emissions when directly combusting AMR for energy recovery. [ABSTRACT FROM AUTHOR]

• Precondition of catastrophic micro-explosion is water coalescence in emulsion droplet. • Water coalescence is induced by the fast rise of oil–water interfacial tension. • Surfactant concentration in emulsion fuel can retard the water coalescence in emulsion droplet. Emulsion fuel technology has been widely accepted as a potential alternative fuel to improve engine fuel efficiency and meanwhile reduce pollutant emissions without additional modification of the engine. Micro-explosion happened in fuel spray has been considered as the most important reason to improve fuel combustion efficiency and reduce harmful emissions. However, a few studies focused on the detailed micro-dynamic processes inside the emulsion droplet before micro-explosion as the emulsion droplet is heated. Understanding these micro-dynamic processes is significantly vital for the explanation of micro-explosion. Therefore, in this study, an experiment was conducted to investigate these micro-dynamic processes inside water-in-oil (W/O) emulsion droplet under high temperature environment using droplet suspension method. During the experiment, a thermocouple was applied to suspend the droplet and meanwhile measure droplet temperature, two high-speed cameras were applied to acquire the micro-dynamic processes inside emulsion droplet and micro-explosion respectively. Based on the collected data including droplet image and droplet temperature, the effect of micro-dynamic processes inside W/O emulsion droplet on droplet evaporation and micro-explosion is analyzed. It is found that the dispersed water particles in emulsion droplet can gradually coalesce into large water particles during the heating process in some cases, and these processes have a great effect on droplet evaporation and micro-explosion: As water coalescence happens in emulsion droplet, the evaporation of water is restrained. As the droplet temperature reaches to the superheating limit, flash boiling of coalesced water can instantly release tremendous energy to induce catastrophic micro-explosion. Without coalescence of dispersed water particles in emulsion droplet, just weak puffing intermittently occurs during the heating process. This result indicates that the precondition of catastrophic micro-explosion for emulsion droplet is water coalescence before droplet temperature reaches the superheating limit. In addition, the mechanism of water coalescence is also investigated in this study from the view of oil–water interfacial tension. It is found that the water coalescence in emulsion droplet is induced by the fast rise of oil–water interfacial tension as droplet temperature exceeds critical temperature of emulsion stability, but increasing the surfactant concentration in emulsion fuel can retard the water coalescence in emulsion droplet. [ABSTRACT FROM AUTHOR]

In order to control the emissions of NO x precursors during sewage sludge pyrolysis, we proposed a novel integrated pretreatment method based on Fenton peroxidation and CaO conditioning. Nitrogen transformation was investigated using a self-designed drop-tube/fixed-bed furnace, and the mechanism of influence of residual conditioners was further clarified by employing model compounds. According to the results, the conversion of sludge- N to gas- N at 873–1273 K was strengthened by composite conditioning during the pyrolysis process. The remaining iron salts prevented some nitrogenous organic matter from deamination, whereas calcium compounds promoted the decomposition of proteins and amine to release NH 3 . Active iron atoms derived from an Fe-bearing conditioner reacted with NH 3 through the formation of Fe α N. Furthermore, combined conditioning hampered the conversion of amine- N /pyridine- N , pyrrole- N and nitrile- N to HCN, therefore enhancing their yields in char. The residual Ca compounds, which presented as Ca(OH) 2 , facilitated the hydrolysis of HCN and hampered HCN generation from amine- N , nitrile- N and heterocyclic- N in tar. Both residual iron and calcium conditioners were capable of reacting with protein- N in sludge and char to form Fe α N and CaC x N y , respectively. The formation of complex Ca 2 Fe 2 O 5 facilitated the decomposition of these intermediates, thus facilitating the conversion of sludge- N and NOx precursors (tar- N , NH 3 , HCN) to N 2 , achieving a highest non-polluting gas yield of 80.5%. [ABSTRACT FROM AUTHOR]

Kaolin is one of the most widely used additives to alleviate fouling and slagging problems, which often occurred on the boilers burning coal with high sodium content. In order to improve the adsorption capacity in this condition, the intercalation-exfoliation method in material field was applied to modify kaolin. Six representative intercalation agents were selected to prepare samples, including hydrazine, urea, potassium acetate, formamide, methylformamide and dimethyl sulfoxide. Experimental results showed that both of pore volume and pore diameter were expanded through modification, which is beneficial to adsorption in physical aspect. On the other hand, the reduction of mass loss rate (from 10.6% to 6.8%), i.e. the loss of hydroxyl groups during modification process was verified, which contributed to sodium-capturing through providing more available adsorption sites. There was little difference between raw kaolin and modified kaolin with regard to XRD patterns, suggesting that the main crystal structure of kaolin remained after modification. Sodium reacted with modified kaolinite to form nepheline during adsorption process, realizing its chemical fixation. It is concluded that intercalation-exfoliation method is capable of improving the sodium-capturing capacity of kaolin at high temperature. Kaolin intercalated with potassium acetate has the most significant sodium-capturing capacity, which increased from 77 mg/g to 100 mg/g, with the adsorption efficiency reaching 100%. [ABSTRACT FROM AUTHOR]

• Comprehensive competitiveness of coke-oven gas utilization schemes is conducted. • Effects of allocation principle and price on scheme's performances are investigated. • Power generation is the most competitive scheme as performs better in all aspects. • Natural gas production competitiveness is slightly higher than hydrogen production. • Methanol production only slightly outperforms natural gas in capital investment. Coke-oven gas (COG) is the by-product of coking process and can be used as feedstock in energy and chemical processes. However, the relative advantages and comprehensive competitiveness of various mature and widely-used utilization schemes still need to be investigated, which will be helpful in exploring better ways to use COG. From the perspective of energy supply, this paper investigated the energy consumption, carbon emissions, capital investment and product cost of COG-to-hydrogen (COGtH), COG-to-natural gas (COGtNG), COG-to-methanol (COGtM) and COG-to-power (COGtP) through LCA method, and compared the comprehensive competitiveness using entropy weight method. The results show that COGtP performs better in all aspects, only consumes 2.669 MJ of energy and generates 0.14 kg CO 2 -eq of carbon emissions when outputting 1 MJ of energy, and product cost is only 1.11E-02 RMB/MJ, making it the most competitive utilization scheme. COGtM consumes the highest 8.525 MJ of energy and generates 0.708 kg CO 2 -eq of carbon emissions when outputting 1 MJ of energy, and it is superior to COGtNG only in terms of capital investment, making it the least competitive utilization scheme. The comprehensive competitiveness of COGtNG is slightly higher than COGtH, with comprehensive score of 0.49 and 0.46 respectively, and it can be further improved by reducing the equipment investment of methanation, while the performance of COGtH in economic aspect needs to be improved, especially to reduce product cost. Further analysis shows the extent to which the energy consumption and carbon emissions is affected by allocation principle is determined by the proportion of energy consumption and carbon emissions in the coking and upstream coal mining, washing and transportation stages, and under value allocation, the energy consumption and carbon emissions is almost directly linearly proportional to COG price, but non-linearly inversely proportional to coke price. In addition, the value allocation is favorable than mass and energy allocation in view of its reduced energy consumption and carbon emissions of utilization schemes if COG price decreases to 0.38 RMB/Nm3 and 0.47 RMB/Nm3 respectively, or coke price increases to 1122 RMB/t and 899 RMB/t respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synergistic capture of Na/As by kaolin along the path was verified in actual boiler. • NaCl facilitated the adsorption of As 2 O 3 by metakaolin (E adsorption = −909.7 kJ/mol). • More Na was released at 1683 K/1473 K, captured by kaolin to form aluminosilicates. • The increase of Fe/Al-bound As led to the enhanced As capture efficiency by kaolin. During the combustion of high-Na coal, kaolin was a commonly used additive to alleviate the fouling and slagging problems. It was also proved to be effective in capturing As 2 O 3 in our previous lab-scale experiment. In this study, the effect of kaolin on the fate of Na/As-related ashing behavior was investigated by determining the concentration and binding forms of Na/As in the ash along the flue gas path on a 3 MW th pilot-scale furnace. The mechanism involved was also explored through DFT calculation, the spatial distribution of Na/Si/Al in single-particle, and the ash size classification. The results showed that in the coal-fired furnace, metakaolin derived from kaolin dehydroxylation promptly captured Na/As-containing substances, and enhanced As adsorption capacity of metakaolin-NaCl was observed. Part of the adsorption products went downstream with the flue gas, leading to a decrease of 45% and 27% Na content in ash at the burner (BR, 1683 K) and bottom ash hopper (BT, 1473 K). Meanwhile, another part of the products was left at the two positions, contributing to an increment to 1.7/2.1 μg/g As in BT/BR ash. With the flue gas temperature decreasing to 923 K, ash containing kaolin with Na/As adsorbed was deposited at the low-temperature reheater. Aluminosilicate-bound Na and poorly crystalline Al-bound As increased by 5.68% and 22%, respectively. When the temperature dropped to 473 K, more fine particles with kaolin (aerodynamic diameter < 10 μm) were deposited at the air preheater, which resulted in 102% of increase in total As content and 40.7% in poorly crystalline Al-bound As content. In general, it is a promising way to use kaolin for co-capturing Na- and As-substances during coal combustion since Na could promote the adsorption of As by kaolin instead of competing at high temperatures. [ABSTRACT FROM AUTHOR]

[Display omitted] • The reaction mechanism of multi-component kitchen waste was elucidated. • A kinetic model of hydrothermal carbonization based on components was proposed. • The rate of the amidation reaction was faster than that of the Maillard reaction. • The carbonization of carbohydrates generated almost all the gas. Hydrothermal carbonization (HTC) is a suitable method to pretreat kitchen waste with high moisture content and complex composition. Developing a precise kinetic model can accurately predict the yields of products to obtain better economic benefits in subsequent utilization, such as fuel. This study aimed to propose an HTC kinetic model of kitchen waste by studying the multi-component reaction mechanism. The HTC reactions of multi-component kitchen waste could be summarized as three key reactions: carbonization of carbohydrates, the Maillard reaction, and the amidation reaction. These reactions were reflected in the kinetic model. Moreover, the calculated results indicated the fitting degree reached 0.9995, which accurately simulated the hydrothermal process of kitchen waste. This model illustrated the rate and extent of the reaction between the components. The kinetic results showed that the rate constant of carbonization of carbohydrates was 0.0012, and that of the Maillard reaction and the amidation reaction were 0.0998 and 0.1409, respectively. The amidation reaction competed with the Maillard reaction and dominated the reaction of the constant-temperature stage. This model provided preliminary guidance for regulating and utilizing HTC products from kitchen waste in different institutions and regions. [ABSTRACT FROM AUTHOR]

Iron- and calcium-based compounds play an important role in the devolatilization stage of solid fuels thermal disposal. This study aims to investigate the synergistic effects of Fenton’s reagent (Fe 2+ /H 2 O 2 ) and conditioner CaO on product distribution and sulfur transformation in this process. Four samples were pyrolyzed by using a special drop-tube/fixed-bed furnace at 873–1273 K with a high heating rate. Specific compositions of solid residue, tar and gas were also identified to further clarify the related mechanisms. According to the results, after Fenton peroxidation, both side chain and main chain of organic compounds were prone to crack, forming more gas and less tar with similar composition. When the oxidized sludge was further treated by CaO, altered carbon species evolution left additional C OH, C O, C (O, N), O C O in char. Moreover, synergy between the two conditioners was likely to provide Fe 2 O 3 , CaO and H 2 O, further increasing the H 2 -rich gas yields. Besides, the observation also demonstrates that Fenton treatment favored the char-S production not only through catalyzing the cyclization reactions but also from producing relatively stable sulfonic acid-S/sulfone-S. When temperature increased, the peroxidation hindered H 2 S, CS 2 and CH 3 SH releasing, while the decomposition of FeSO 4 and Fe 2 (SO 4 ) 3 aggravated SO 2 polluting. However, it is exciting that sulfur fixation rate eventually reached over 97.0%, since the residual Fe- and Ca-containing compounds cooperatively captured liberated sulfur. Thus reusing conditioners, which originally targeted for improving sludge dewaterability, is a promising strategy for achieving efficient thermal conversion of sewage sludge with low sulfur pollution. [ABSTRACT FROM AUTHOR]

Binary NiMo, CoMo, NiW, and CoW transition-metal oxide catalyst precursors, were synthesized through a hydrothermal reaction, and highly-loaded hydrodesulfurization (HDS) catalysts were prepared by mixing the precursors with an alumina gel, calcination and sulfidation. The transition-metal oxide catalyst precursors and highly-loaded sulfide catalysts were characterized by XRD, N 2 adsorption–desorption, XRF, and HRTEM. Dibenzothiophene and fluid catalytic cracking (FCC) diesel were employed to evaluate the HDS performance. The crystalline phases of ammonium nickel (or cobalt) molybdate were detected in the NiMo (or CoMo) oxide catalyst precursors, while quasi-amorphous phases were observed for the CoW and NiW oxide precursors. In the sulfided HDS catalysts, typical MoS 2 or WS 2 phases were observed by TEM, while XRD demonstrated that Ni and Co sulfides were present, in accordance with HRTEM results. The catalytic results showed that the binary transition-metal CoMo sulfide catalyst exhibited high direct desulfurization activity and that the NiMo sulfide catalyst had higher HDS and hydrodenitrogenation activities toward the FCC diesel than the other catalysts, with conversions of higher than 99.1% and 99.7%, respectively. [ABSTRACT FROM AUTHOR]

Highlights: [•] A series of nickel–copper–molybdenum catalyst precursors was synthesized by chemical precipitation. [•] The particle sizes of the MoS2 nanoclusters and sulfided nickel-containing compounds varied with the introduction of copper. [•] A Ni9.5Cu0.5Mo10 catalyst exhibited high hydrodesulfurization activity. [Copyright &y& Elsevier]

Abstract: This paper describes the effect of fuel sulfur levels on vehicle emissions. The project was undertaken to provide a basis for lowering sulfur levels in fuel in order to establish necessary vehicle emission standards. A matrix was developed to describe the relationship between fuel sulfur levels and vehicle emissions based on vehicle testing data in China and the literature research. The matrix was then integrated into a vehicle behavior forecasting spreadsheet to analyze the vehicle emission reduction potentials under several fuel desulfurization scenarios. The results of comparing the total emissions in typical years for several scenarios show that the best emission control effect can be achieved by completely matching the fuel sulfur requirements with the emission standards. This assessment of vehicle emission standards and refinery costs to produce low sulfur fuel provides a critical insight into the importance of reducing fuel sulfur as emission requirements become more stringent. [Copyright &y& Elsevier]

• Modified tonstein (CuBr 2 -TCS) effectively removed Hg0 from simulated flue gas. • O 2 significantly facilitated Hg0 removal by the spent adsorbent after the cycle. • The adding order of NO and SO 2 had a large effect on the performance of CuBr 2 -TCS. • Both Cu2+ and Br played key roles in the process of Hg0 removal. Tonstein in coal seam (TCS) is a kind of mining solid waste, which was developed to a novel adsorbent (CuBr 2 -TCS) by using copper bromide modification. In this paper, CuBr 2 -TCS was subjected to elemental mercury (Hg0) removal experiment in simulated coal-fired flue gas (SFG). Several characterization methods were used to determine the mineralogical characteristics of TCS and reaction mechanisms. In-depth, the Hg0 removal performances of CuBr 2 -TCS under different flue gas components were explored. The results revealed that CuBr 2 -TCS exhibited 92.1% and 78.3% Hg0 removal efficiency in dry and wet SFG, respectively. HCl and O 2 facilitated Hg0 removal performance of CuBr 2 -TCS by supplementing oxygen atoms and halogens, respectively, accompanying some intermediate transition products such as Cu 2 OBr 2. SO 2 played a serious suppressive role. SO 2 acting alone or NO and SO 2 acting simultaneously caused irreversible changes in the surface functional groups that formed active sites with NO. However, the thermal stability of the adsorbed mercury on the adsorbent which was spent in N 2 + SO 2 + O 2 atmosphere became better. In addition, the spent adsorbent that first went through the Hg0 removal process in N 2 + NO atmosphere, exhibited higher Hg0 removal efficiency in N 2 + SO 2 + NO atmosphere than that first reacted in N 2 + SO 2 atmosphere. CuBr 2 -TCS is a cost-effective adsorbent for the Hg0 abatement from the coal-fired flue gas (CFG). [ABSTRACT FROM AUTHOR]

• A longer lifetime and better recycling stability of Org-CaO than that of conventional CaO. • Org-CaO promoted amorphous coke formation mainly existed as O-containing aliphatic species. • Organic calcium precursor inhibited coke deposition and pore plugging of CaO. • Org-CaO with better anti-sintering ability to slower irreversible deactivation. • Weaker loss of strength and density of basic sites on Org-CaO than that on conventional CaO. The conversion of biomass wastes into upgraded bio-oil has been successfully implemented by catalytic fast pyrolysis (CFP) with CaO catalyst. The bottleneck of CFP technology is catalyst deactivation. Ex-situ catalytic pyrolysis of biomass wastes with multiple recycling of CaO from different calcium precursors were performed in a continuous fixed-bed at 500 °C. The objectives were to intensify the anti-deactivation and regenerative stability of CaO using organometallic precursor, and comprehensively distinguish the effects of calcium precursors on deactivation mechanism in terms of coke yield, coke species, structural and chemical changes et al. The results demonstrated that organic calcium precursor strengthened the recyclability of CaO catalyst during upgrading of bio-oil by showing longer lifetime and better recycling stability. Compared with conventional CaO from Ca(OH) 2 (CH-CaO), the stronger deoxygenation and superior porosity of CaO from organic calcium precursors (Org-CaO) facilitated the removal of coke precursors and suppressed pore plugging. The average coke yields of CH-CaO and Org-CaO were respectively 5.1 and 2.2 g/m2. Moreover, CH-CaO promoted the aromatization of coke precursors, leading to coke existing in form of hard diamond-like structure. But coke deposited on Org-CaO exhibited softer layered graphite structure and contained more aliphatic matters. After 10 reaction/regeneration cycles, Org-CaO still kept 50% deoxygenation activity whereas CH-CaO showed almost complete deactivation. Organic calcium precursors delayed irreversible deactivation of CaO, since these precursors physically prevented the sintering and agglomeration of CaO, and chemically alleviated the loss of both the strength and density of basic sites on CaO. [ABSTRACT FROM AUTHOR]

• An ingenious alkali vapor generator was designed to provide gas-solid reaction condition. • Four classical adsorption models were applied to fit the time-resolved adsorption of K vapors. • The Q e and initial adsorption rate of kaolinite increased by 100% after I-E modification. • More K vapors were captured by kaolinite than Na due to the higher alkalinity. • The maximum loading capacity occurred at the Na/K atomic ratio of approximately 1:1. Frequent corrosion of heat transfer tubes in boilers, which was closely related to the massive corrosion sources, such as KCl and NaCl vapors in flue gas, restricted the safe and economic development of MSW incineration technology. This study attempted to alleviate corrosion by using the method of modified kaolinite adsorbing alkali vapors in furnace. Firstly, an ingenious alkali vapor adsorption platform with the advantage of simple operation and precise control was established. Based on this, the time-resolved adsorption of K vapors and the competitive adsorption of K/Na vapors by kaolinite and modified kaolinite were investigated. Four classical adsorption models were applied to mathematically describe the adsorption process. The pseudo-first order model was suitable for kaolinite and pseudo-second order model can be used to fit modified kaolinite. The corresponding rate-controlling steps were external mass transfer and chemisorption step. Accordingly, the equilibrium adsorption capacity of kaolinite and modified kaolinite was estimated as 17.41 and 32.30 mg/g, respectively. During the competitive adsorption of K/Na vapors, it was obvious that more K was captured by kaolinite than Na. It might be caused by the higher alkalinity of potassium, which had a higher tendency to react with acidic kaolinite. Maximum K-loading capacity of kaolinite occurred at the K/Na atomic ratio of approximately 1:1. After the structural calculation of alkali feldspar based on DFT, the most stable state of alkali feldspar occurred at the K/Na atomic ratio of 1:1, which might explain the maximum loading capacity at the K/Na ratio of 1:1. [ABSTRACT FROM AUTHOR]

The present study examines the influence of water vapor in combustion atmosphere on NOx emission from oxygen-enriched combustion of air-dried distilled spirit lees and its char in a laboratory fluidized bed of 760 mm high and 68 mm in inner diameter. Steam was added into the fluidizing gas to vary the vapor content in the combustion atmosphere. At a combustion temperature of 950 °C and a steam-to-fuel mass ratio (S/F) of 0.5, the presence of water vapor reduced the NOx concentration in the flue gas for low O 2 contents (⩽30 vol.%) in the combustion agent but increased the NOx emission for high O 2 contents (⩾40 vol.%). The possible causes were clarified for this shift from suppression to promotion of fuel-N conversion into NOx with raising O 2 concentration in the combustion agent. Varying temperature from 850 °C to 1150 °C resulted in a peak conversion of fuel-N to NOx in the temperature range of 950–1050 °C for all the tested O 2 concentrations. Increasing the O 2 concentration tended to lower the critical temperature corresponding to such a peak fuel-N conversion. Testing results also suggested that the presence of excessive water vapor in the combustion atmosphere would inhibit the release of fuel-N in the devolatilization stage and promote the formation of some reducing gases. In addition to the anticipated diluting effect, the steam addition also shortened the reaction time for homogeneous and heterogeneous NOx reduction by the reducing gases and char. It is postulated that the formation of OH radicals at high O 2 content and high temperature could cause the observed increase in the NOx emission. [ABSTRACT FROM AUTHOR]

In order to address the adverse effects of high sulfur content on the subsequent use of pyrolysis char, the removal of sulfur from high sulfur solid waste during molten salts pyrolysis was studied in this work. The results show that sulfur content of molten salts pyrolysis char was significantly lower than that of general pyrolysis char because molten salts catalyzed the decomposition of organic sulfur. Moreover, the removal efficiency of sulfur in molten salts pyrolysis char was obviously enhanced with the increase of temperature and time. Especially under the condition of 850 °C and 2 h, more than 33 wt% of the sulfur in molten salts pyrolysis char was successfully removed compared with ordinary pyrolysis char. Molten salts, which provided a larger contact area between char and volatiles, promoted a large amount of easily decomposed organic sulfur-containing compounds production by the cyclization reactions between char and hydrogen sulfide at higher temperatures. Due to the adsorption of H 2 S by molten salt, the SH radical was released more into the molten salt in the form of H 2 S rather than reacting with zinc oxide to form thermal stable zinc sulfide. Both of these reasons contributed to the removal of sulfur in the molten salt pyrolysis char. [ABSTRACT FROM AUTHOR]

Molten salt gasification is a promising way for collaborative use of solar energy and Zhundong coal, with in situ capture of Cl/S-pollutants as well as alkali metals. The present study provides a deep insight into carbon conversion during molten salt gasification of a typical Zhundong coal in ternary carbonate eutectics (Li 2 CO 3 -Na 2 CO 3 -K 2 CO 3 ). The results demonstrated that the molten salt gasification of Zhundong coal underwent a rapid devolatilization of raw coal and then the gasification of char. The interactions between CO 2 and volatiles promoted the cracking of macromolecular compounds, increasing the carbon conversion efficiency during the devolatilization process. The gasification of char was mainly determined by the direct reaction with molten salt, which was slightly affected by the CO 2 concentration in the carrier gas. The results of char characterization evidenced that the condensation/graphitization of char was stimulated in the molten eutectics. Meanwhile, a large amount of O-containing groups, especially carbonyl groups, were formed in the molten salt treated char with carbonates as oxygen supplier. Under the influence of molten salts, some carbonyl groups would be formed inside the char. However, the decomposition of those carbonyl groups was suppressed by the mass transfer resistance of the released CO and/or CO 2 . Applying proper feeding mode, such as feeding coal in pulverized form, could enhance the contact of coal, molten salt and CO 2 , which remarkably promoted the interactions between molten salts and char containing functional groups. [ABSTRACT FROM AUTHOR]

Molten salt gasification provides a promising way for the combined usage of solar energy and coal, during which molten salts act as a heat storage and transfer medium. However, the interactions between coal ash components and molten salts might have undesired effects on the molten salt gasification. The present study investigated the distribution of mineral matters in typical Zhundong coals and the fate of coal ashes in the high-temperature Li 2 CO 3 -Na 2 CO 3 -K 2 CO 3 eutectic system. The results showed that alkali and alkaline earth metals (AAEMs) were widely distributed in Zhundong coals in the forms of NaCl, CaCO 3 , CaSO 4 and organic matter, which were predominantly dissolved in the molten salts. After the dissolution of these AAEMs, the melting temperature and enthalpy of the molten salts were changed, while the viscosity of the mixtures was hardly affected in melting phase. On the other hand, Si/Al-compounds were also of high content in some Zhundong coals, existing as quartz, kaolin and amorphous species. Some of these compounds tended to react with molten salts, by forming Li-silicate or Li/K-aluminosilicates, which were precipitated out of the system. Meanwhile, the suspension of the unreacted Si/Al-compounds increased the viscosity of molten salts. Additionally, interactions between coal ashes and molten salts brought about the decrease in thermal diffusivity and thermal conductivity of the eutectic system as well as the increase in specific heat capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ML-LRM method was reliable for the acquisition of kinetic parameters. • Massive amount of accurate yields were obtained by ML algorithm. • Comprehensive five-stage reaction mechanism of TDCE process was constructed. The homogenizing pyrolytic method denoted as the "Thermal-dissolution based carbon enrichment (TDCE)" was effective in converting different biomasses into value-added carbon products. However, the product yields from the TDCE process varied greatly despite the biomasses undergoing similar reactions. Consequently, a generalized kinetic study is essential in determining the different kinetic parameters of each biomass. In this study, the lumped reaction model was coupled with machine learning algorithm (ML-LRM) for the general acquisition of these kinetic parameters. 304 yield data of cellulose under different conditions were accurately predicted by the machine learning algorithm and were further utilized for subsequent kinetic modeling. In addition, the derived conversion pathways were quite reliable, as the one from predicted data was similar to that calculated from experimental data (R2 = 0.95) under experimental conditions, but with higher accuracy (R2 > 0.99). Moreover, a novel five-stage reaction mechanism was proposed to quantitatively and qualitatively describe the TDCE process based on the kinetic studies and the pre-proposed reaction mechanism. Consequently, the ML-LRM method was proven to be effective in elucidating the main reactions at any temperature throughout the TDCE treatment and can therefore provide guidance towards directed regulation and practical application of said products. [ABSTRACT FROM AUTHOR]

• Pressurized pyrolysis of dense coal cores. • Compared with 0.1 MPa, the CH 4 yield of 3 MPa of increased from 32.60 to 77.31 L/kg. • With the increase of pyrolysis pressure, the oxy-quaternary carbon chain decreased. • Pyrolysis pressure can promote the conversion of aliphatic groups to CH 4. Deep underground coal gasification (UCG) is characterized by high reaction pressure (dependent on hydrostatic pressure of coal seam) and high CH 4 content. The formation mechanism of CH 4 in product gases has always been an interesting topic. In this paper, pressurized pyrolysis characteristics of coal core were studied through a pressurized pyrolysis device. The formation mechanism of CH 4 and structural evolution of semi-coke during the pressurized pyrolysis process were identified by X-ray diffractometer (XRD), pressurized thermogravimetric analyzer coupled with Fourier transform infrared spectrometer (TG-FTIR) and carbon-13 nuclear magnetic resonance (13C NMR). The results indicate that the yield of pyrolysis gas and carbon emission rate rise with an increase of pyrolysis pressure, while the yield of tar decreases. Compared with atmospheric pressure, the pyrolysis gas yield increases from 148.6 L/kg to 172.6 L/kg at 3.0 MPa, the CH 4 yield increases from 32.6 L/kg to 77.3 L/kg. The CH 4 begins to be released at around 400 °C at different pyrolysis pressures, and the generation rate reaches its maximum at around 500 °C. The analysis of 13C NMR shows that the relative content of the oxy-quaternary carbon in the aliphatic group decreases significantly from 9.2% to 1.8% with an increasing pyrolysis pressure. Therefore, pressure promotes the reaction of aliphatic carbon with hydrogen radicals to form CH 4 , which is one of the main reactions for the generation of CH 4 by pressurized pyrolysis. [ABSTRACT FROM AUTHOR]

Oxidic unsupported Ni–Mo–W catalysts were prepared from a precipitate by high-temperature hydrothermal synthesis. The catalysts were sulfided in-situ by CS 2 and H 2 under different sulfiding conditions. The catalytic activity and selectivity were studied in the model reactions of naphthalene hydrogenation (HYD), quinoline hydrodenitrogenation (HDN), and dibenzothiophene (DBT) hydrodesulfurization (HDS). The sulfided catalysts were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and energy dispersive spectrum (EDS) mapping. Sulfided unsupported Ni–Mo–W catalysts showed visible diffraction peaks of Ni 3 S 2 and MoS 2 /WS 2 . As the sulfiding temperature or time increased, the Ni 3 S 2 and MoS 2 /WS 2 nanoparticles agglomerated, with MoS 2 /WS 2 lamella curved to some extent. Specifically, the stacking of the MoS 2 /WS 2 slabs increased with increasing sulfidation time. Meanwhile, the catalysts showed higher HDS, HDN, and HDAr activities when the sulfiding temperature was 320 °C. However, the hydrogenation activity decreased above 340 °C. [ABSTRACT FROM AUTHOR]

• Secondary reactions were significantly promoted by partial pressure of volatiles. • The partial pressure was the root cause of the deep deoxygenation. • Structure rearrangement reactions occurred significantly during GP torrefaction. • Self-promoted deoxygenation of biomass under pressure was confirmed. Gas-pressurized (GP) torrefaction of biomass, proposed in our previous work, has a much higher oxygen removal efficiency compared to conventional torrefaction, but how the pressure promoted the deoxygenation remains unclear. In this work, the GP torrefactions under different partial pressures of volatiles (P vol) and total pressures (P tot) were conducted. The results revealed that the P vol was the root cause rather than the P tot of the acceleration of biomass decomposition and deoxygenation for the first time. This process can be regarded as a self-promoted deoxygenation process, and consisted of three stages. Stage 1 was the volatiles formation stage, where hemicellulose decomposed, volatiles formed and the P vol increased. Stage 2 was self-promoted dehydration stage, where the hydroxyl in biomass was dramatically removed. Stage 3 was structure rearrangement stage, where the aromatic structure formed. The stage 2 and stage 3 were highly correlated with the P vol , and resulted in the deep deoxygenation of biomass. This study should be not only suitable for the GP torrefaction, but can also be extended to pressurized pyrolysis and gasification of biomass. [ABSTRACT FROM AUTHOR]

Abstract: Porous ammonium nickel molybdate, a potential precursor for deep hydrodesulfurization catalyst with the formula of (NH4)HNi2(OH)2(MoO4)2, was synthesized by a high-temperature hydrothermal synthesis method. The unsupported NiMoS catalysts with various Ni/Mo ratios were prepared from the precursors. The precursors and catalysts were characterized by nitrogen physisorption, powder XRD, TG–DSC–MS, HRTEM, SEM and evaluated in the continuous HDS of FCC gas oil. The results indicated that the activities of thus-achieved catalysts were much higher than that of commercial NiMo/Al2O3. The catalysts derived from the crystalline ammonium nickel molybdate showed much higher catalytic activity than that obtained from amorphous precursor, which means they could be attractive material system for futural applications. [Copyright &y& Elsevier]

• High temperature can increase the Si-bearing compounds vaporization and fine particle emission. • Si-bearing compounds vaporization is much higher in the reducing atmosphere than the oxidizing atmosphere. • There is a peak content of SiO 2 in PM 10 , which is in the range of 60–80%. • PM 0.1 formation is influenced by the vaporization-coagulation of SiO 2 and secondary Si-bearing compounds. Pure silica, typical high-silicon coals (Xuanwei area, China) and their low temperature ashes (LTA) were selected to carry out a vaporization experiment in different atmospheres to reveal the release mechanism of silicon. Further, high-silicon coal combustion experiments were conducted using a drop tube furnace (DTF) to investigate the formation behaviors of fine particulate matter (PM) and the distribution of silicon in the different-sized particles. Field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDX) and X-ray fluorescence spectrometry (XRF) were used to study the morphology and chemical compositions, respectively. The results show that the high temperature would promote Si-bearing compounds vaporization and fine particle emission. The SiO 2 vaporization rate in the reducing atmosphere (steam and CO 2) is much higher than that in the oxidizing atmosphere (air and CO 2 /O 2). Higher O 2 concentrations in CO 2 /O 2 atmospheres will handicap Si-bearing compounds vaporization; the SiO 2 vaporization rate of Yantang coal decreased from 4.7% to 3.9% as the O 2 concentration increased from 10% to 30% at 1400 °C. A maximum value of the PM 1.0 concentration can be observed at 0.1 μm, and there is a peak content of SiO 2 in PM 10 , which is in the range of 60–80% for different temperatures. The mechanism of PM 0.1 formation is related to the vaporization-coagulation of the refractory SiO 2 and secondary Si-bearing compounds, and the more Si that vaporizes at high temperatures, the more PM 0.1 that is generated during coal combustion. [ABSTRACT FROM AUTHOR]

• Bio-waste underwent apparent decomposition in molten-salt pyrolysis at 300 °C. • Molten cations acted as catalysts and anions participated in products formation. • Cellulose pyrolysis was similar to hemicellulose, but totally differed from lignin. • Lignin was more likely pyrolyzed than (hemi)cellulose by forming more CO and H 2. • (Hemi)cellulose reacted with anions to generate N-containing heterocycles, amines. This study, for the first time, investigated the volatiles emission and thermochemical conversion mechanism of bio-waste during pyrolysis in molten salts (NaNO 3 -KNO 3 -NaNO 2) at 300 °C. Cations of molten salts acted as catalysts while anions participated in the pyrolysis reaction. Compared with salt-free pyrolysis, more bio-waste was decomposed in molten salts, to produce more than 14 times the mass of gaseous products and twice the mass of liquid products. Furthermore, the thermochemical conversion behavior of typical biomass constituents, i.e. cellulose, hemicellulose and lignin, was also distinguished. The results suggested that lignin was most easily pyrolyzed to form numerous liquid acids, some nitrated aromatic compounds and more CO, H 2. In contrast, the decomposition of cellulose was certainly restricted while more significant effects of anions were found in hemicellulose cracking by generating nitrogen-containing heterocyclic rings and amines. Besides, interactions among different biomass constituents were confirmed to affect the generation of bio-waste pyrolysis products. [ABSTRACT FROM AUTHOR]

• Pyrolysis kinetics of rice straw (RS) torrefied at varied gas pressure was studied. • GP torrefied RS showed higher activation energy (E a) with increased pressure. • GP torrefied RS displayed the widest E a distribution during pyrolysis. • Activation energy (E a) of the GP torrefied biomass ranged from 195 to 198 kJ mol−1. • The effect of pressure on the kinetics variation was investigated in detail. A novel gas-pressurized (GP) torrefaction of biomass waste was proposed in our recent work to deeply upgrade the biomass under the pressure of 5 MPa prior to their subsequent use in thermo-conversion technologies such as pyrolysis, combustion and gasification. However, the effect of varying pressure on the GP torrefaction process and the thermochemical behaviour of the torrefied biomass were not clear. In this work, the effect of varying torrefaction pressure on the pyrolysis kinetics and mechanism of GP torrefied biomass was studied in detail. It was revealed that the activation energy (E a) of the GP torrefied biomass ranged from 195 to 198 kJ mol−1 increasing with torrefaction pressure, and their activation energy distributions were invariably wider compared to raw and torrefied biomass produced by atmospheric pressure torrefaction. The carbon and fixed carbon content, aromaticity, and crystallinity of the GP torrefied biomass were promoted by increasing the torrefaction pressure. On the other hand, the porosity of the GP torrefied biomass was reduced by elevated pressure. These are the reasons for the E a increase of the GP torrefied biomass under elevated pressure. The presented kinetics and mechanism study provide a deep understanding of the novel GP torrefaction method. [ABSTRACT FROM AUTHOR]

• A novel two-stage method was proposed to prepare nano-scale carbon fiber. • An extract was obtained by degradative solvent extraction from biomass wastes. • The nano-scale carbon fiber was prepared by this extract. • The diameter of the extract-based carbon fiber was about 169 nm ~ 200 nm. • The specific surface area and specific volume of carbon fiber reached to 714.24 m2/g and 164.10 cm3/g. One of the most essential topics in carbon fiber research is seeking a suitable precursor for the carbon fiber preparation. In this work, an extract was obtained from biomass wastes by a degradative solvent extraction method under moderate conditions. This extract had the properties required for carbon fiber preparation, such as high carbon content, low ash content, thermoplastic property etc. The carbon fiber, prepared using the extract by electro-spinning, had a coarser surface with the specific surface area and specific volume respectively reaching to 714.24 m2/g and 164.10 cm3/g, higher than those of PAN-based carbon fiber. The diameter of the extract-based carbon fiber was about 169 nm ~ 200 nm. The R (I D /I G) value was as low as 1.46. The stabilization and carbonization of extract-based and PAN-based fibers were also conducted via a TGA-DSC for a detailed investigation and comparison. It showed that the thermochemical behaviors of both carbon fibers were different. Thus, it proved that the degradative solvent extraction of biomass waste is a promising method for precursor production to prepare nano-scale carbon fiber with specific properties. [ABSTRACT FROM AUTHOR]