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Refuse derived fuel (RDF) is produced in large amounts but its heterogeneous nature and low calorific value reduce the potential for energetic valorization of this material. In this work, the torrefaction and carbonization of RDF was studied in a temperature range of 200–400 °C and residence times from 15 to 60 min, yielding chars with increased density, high heating value (HHV), carbon content, ash content and fixed carbon. Leaching experiments showed that some inorganic components like calcium or chlorine could be removed from the RDF char, upgrading its fuel quality. For temperatures in the torrefaction range (200 °C and 250 °C), energy yields were higher than 96.3% and process energy efficiencies were higher than 85%, but the HHV of the RDF chars were lower than 19.4 MJ kg−1. In the carbonization range (300 °C to 400 °C) it was possible to obtain RDF chars with HHV in the range of 20.1–26.2 MJ kg−1, with energy yields from 84.5 to 91.7% and process energy efficiencies from 70.8 to 79.2%. The obtained results showed that thermochemical processing can be used to upgrade RDF thus promoting sustainable solutions for its management and valorization. • Torrefaction and carbonization of industrial RDF was studied at different conditions. • Carbonization yielded the RDF chars with higher carbon content and heating value. • Chlorine and ash contents of the RDF chars could be reduced by water leaching. • Carbonization presented energy efficiencies compatible with autothermal operation. [ABSTRACT FROM AUTHOR]

Abstract Co-hydrothermal carbonization (co-HTC) is recognized as a promising pretreatment for upgrading fuel quality of high moisture biomass prior to further thermal conversion. The properties of the hydrochar derived from co-HTC of sewage sludge (SS) and sawdust (SD), and CO 2 gasification characteristics of the hydrochar were investigated. The results showed that the hydrochar had enhanced aromatic degree and increased metals content compared to raw sludge. The hydrochar also exhibited an enhanced gasification reactivity, resulting in high carbon monoxide content in the syngas than that from SS under identical conditions. The temperature and SD/SS mass ratio had a significant influence on the syngas composition mainly by the Boudouard reaction and water gas reaction. The gasification reactivity was strongly associated with the inorganic elements, and the KAlSi 3 O 8 inhibited while the K 2 CO 3 promoted the gasification reaction of hydrochars. Under optimal conditions, a high gasification efficiency of 77.73% was obtained, and the lower heating value of the syngas reached 8.15 MJ/Nm3. This study indicated that co-HTC of SS and SD combined with subsequent gasification had promising potential towards syngas production with high quality. Highlights • The hydrochar from co-HTC of sewage sludge and sawdust was prepared. • Hydrochar had enhanced aromatic degree, metals content and gasification reactivity. • Temperature and sawdust content had a significant influence on syngas composition. • KAlSi 3 O 8 and K 2 CO 3 had competitive effect on CO 2 gasification of the hydrochar. [ABSTRACT FROM AUTHOR]

Abstract A novel two-stage gasifier, consisting of a fluidized bed gasifier and a swirl-melting furnace, was proposed and built to gasify biomass with low ash melting temperatures into clean fuel gas. Improvements of the two-stage gasification in gas upgrading, tar removal and ash separation were confirmed by characteristic analysis of gas, tar, ash and slag. Influence of equivalence ratio (ER), oxygen distribution and gasifying agent were assessed for process optimization. Refined gas with a LHV up to 11.1 MJ/Nm3 and a tar content lower than 1 g/Nm3 was produced. Ash was completely vitrified with a high conversion of fixed carbon and volatile, resulting in a cold gas energy fraction of approximately 80%. Increasing ER promoted gas production but limited energy conversion efficiency and gas LHV. Proper oxygen distribution among the two stages was beneficial to decrease energy loss and increase gas quality. Increasing oxygen percentage of gasifying agent enhanced combustible gas content and improved overall gasification efficiency. Highlights • A new two-stage gasification is presented to dispose low ash melting point biomass. • Tar could be effectively removed by high temperature secondary oxygen gasification. • High degree carbon conversion and ash vitrification could be obtained. • Improvements in biomass fuel gas quality and gasification efficiency could be confirmed. • The pilot test fully verified the feasibility of two-stage gasification. [ABSTRACT FROM AUTHOR]

High hydrothermal temperature and solid-N enrichment were the key issues during co-hydrothermal carbonization (co-HTC) of sludge and lignocellulose biomass. The technology of acid-alcohol assisted co-HTC was proposed and the relevant reaction mechanisms were investigated in this study. The results showed that acetic acid and ethanol promoted the Maillard and Mannich reaction respectively at 453 K through catalytic degradation of different organics. Above 483 K, acetic acid contributed to deamination and reduced solid-N by 9.18%, but there was no decrease in yield because acetic acid participated in hydrochar formation by repolymerization. Ethanol preferred to increase production by 5.82% without extra solid-N enrichment, promoting NH 4 +-N transformation into quaternary-N with more organic groups substitution. Solvent mixture had best performance on dehydration, carbonization and denitrification reaction to upgrade hydrochar fuel quality. The hydrochar obtained was more approach to lignite with high fixed carbon and heating value as well as low nitrogen content. Thus the fuel property and substance composition could be selected by adjusting the combination of hydrothermal temperature and organic solvent. [Display omitted] • Co-HTC with organic solvent contributed to low nitrogen hydrochar preparation. • Both acetic acid and ethanol decreased the temperature of interactions. • Acetic acid can remove solid-N while ethanol preferred to boost hydrochar yield. • Ethanol converted NH 4 +-N into quaternary-N via intensifying the Mannich reaction. • Mixed solvent had better dehydration, carbonization and denitrification performance. [ABSTRACT FROM AUTHOR]

Abstract In this paper we conduct an empirical analysis of the environmental and economic performance of coal-fired power plants in the United States. Using nonparametric methods for efficiency analysis we propose a theoretical framework that builds upon the restrictions of mass balances for production possibilities and explicitly takes into account heterogeneous fuel quality and prices of the fuel input. This heterogeneity influences both the cost of the production and the emission of environmentally harmful pollutants. Moreover, we analyze how the incorporation of transportation costs influences the cost efficiency of the electricity generating units and quantify the trade-off between environmentally efficient and cost-minimizing production of electricity. Highlights • A nonparametric model to estimate cost and environmental efficiency is proposed. • The model accounts for heterogeneous input quality and transportation costs. • Cost and environmental efficiency of U.S. power plants is evaluated. • Transportation costs significantly influence the results. • A trade-off between environmental and cost efficiency exists. [ABSTRACT FROM AUTHOR]

Gas-pressurized torrefaction is efficient for upgrading biomass to substitute metallurgical coke. Herein, the effects of pressure and temperature on corncob torrefied products as well as the synergistic mechanism were investigated. The results indicated pressure facilitated secondary reactions that converted volatiles to fixed carbon. As the temperature increased to 280 °C from 180 °C under 3 MPa, the volatile content decreased from 82.72% to 48.71%, and the HHV improved from 16.14 MJ/kg to 28.60 MJ/kg, which were close to the quality of bituminous coal. Lignin was mixed with corncob to further improve the property of torrefied products. The fixed carbon of mixture semi-char increased by 11.28% compared to the theoretical value, the O/C and H/C ratios decreased to 0.18 and 0.74 respectively, reaching the quality of coking coal. The blending of lignin promoted the formation of water under subcritical conditions, accelerating biomass decomposition. Cross-interaction reactions among volatiles intensified the deoxygenation and more acetic acid was produced that promoted carbonization reactions, causing the removal of oxygen in the form of gas and a higher fixed carbon in the semi-char. The finding promoted biomass application in low-carbon iron production significantly by obtaining bio-coking coal. • The reaction mechanism of corncob under different conditions was studied. • A lignin-corncob mixture pressurized torrefaction method was proposed. • Higher fixed carbon and lower oxygen content was obtained due to a synergism. • This synergy facilitated decomposition, deoxygenation and aromatization reactions. • A substitute with similar fuel quality to coking coal feedstock was prepared. [ABSTRACT FROM AUTHOR]

The strict fuel quality limitations are amongst the main barriers preventing the success of small-scale downdraft gasification. In a first step towards alternative fuels, the application of wood chips with bark content must be investigated. Therefore, this paper presents the results of thermogravimetric analyses (TGA) and the gasification of wood chips with a significant larch bark content (up to 50%) in a stratified downdraft gasifier. The TGA revealed, that bark generated twice as much char as wood during pyrolysis. The gasification zones in the downdraft reactor did not shift when the fuel was switched, which allows its utilization in the same setup as pure wood chips. The concentrations of CO, H 2 and CO 2 were also almost unaffected at approximately 21.5 vol%, 14.6 vol% and 9.1 vol%, respectively. The highest gasification efficiency was achieved with 20% fuel bark content. The most significant effect was the reduction of the non-methane hydrocarbon content by up to 80% when bark was in the fuel, due to reduced tar generation and enhanced cracking. Therefore, the addition of bark up to a certain level even improved the gas quality and performance. These novel results predict a bright future for forestry residues in downdraft gasification. • Enabling the utilization of fuel with bark and enhancing gasification in parallel. • Systematic evaluation of the influence of bark in the fuel on gasification. • TGA revealed that bark produces twice as much char as wood during pyrolysis. • A high carbon conversion efficiency of over 95% was achieved in the gasifier. • 50% bark in the fuel decreased the non-methane hydrocarbons in the gas by 80%. [ABSTRACT FROM AUTHOR]

A decomposition analysis of energy related CO 2 emissions is carried out for 33 world countries. The data pertain to the period 1995–2007. The methodology used is the Index Decomposition Analysis that allows to investigate the contribution of the following factors: (i) changes in abatement technologies, fuel quality and fuel switching; (ii) changes in the structure and efficiency of the energy system; (iii) relative ranking of a country in terms of the total GDP (Gross Domestic Product) generation and (iv) changes of the country specific total economic activity. The WIOD (World Input Output Database) has been used together with Organization for the Economic Co-operation and Development (OECD) data on GDP. Results show that economic growth has been the main driving factor of energy related CO 2 emissions increase. However, in fast developing countries like India and China, an important contribution has also been the increasing role that these economies are playing in the global economic panorama. Improvements on energy efficiency have been the main element contributing to reduce the overall CO 2 emission increase in all the countries considered in this study. [ABSTRACT FROM AUTHOR]

This work investigated on the effect of co-hydrothermal carbonization (co-HTC) of polyvinyl chloride (PVC) and alkali coal on combustion and slagging characteristics of the generated fuels (hydrochar). Fuel properties were assessed in terms of ultimate and proximate analysis, functional groups evolution, and ash melting characteristics. The loss of C–O functional groups in coal would be accompanied by the liberation of some elements such as Na and Ca, which were often associated with such groups. The hydrochars presented higher ignition temperature and average combustion rates compared with raw coal. The hydrochar generated from co-HTC at 250 °C showed the best combustion performance due to the enhancement of air contacting and transformation, which was attributed to its porous structure, smaller uniform particle, and relative higher surface area. The activation energy of hydrochars was increased at the ignition stage while was decreased at the combustion stage according to the kinetic analysis. The fusion temperature was increased resulting from the removal of alkali and alkaline earth metals (AAEMs) during the co-HTC process. From the perspective of waste-to-energy, the co-HTC of high-alkali coal and PVC seems to be a feasible solution to improve combustion and slagging characteristics. • Co-hydrothermal carbonization of PVC/alkali coal produced high quality fuel. • Lower H/C and O/C atomic ratio were achieved with raising the HTC temperature. • Co-HTC postponed the ignition but improved the combustion rate of hydrochars. • Abundant pores and surface area promoted combustion of hydrochars. • Co-HTC improved the ash fusing temperature thus preventing slagging. [ABSTRACT FROM AUTHOR]

Abstract: This paper reviews the information available on the impurities encountered in stationary fuel cell systems, their effects on the fuel cells, and the maximum allowable concentrations of select impurities suggested by manufacturers and researchers. A generic model of a molten carbonate fuel cell-based power plant operating on digester and landfill gas has been developed; it includes a gas processing unit, followed by a fuel cell system. The model includes the key impurity removal steps to enable predictions of impurity breakthrough, component sizing, and utility needs. These data, along with process efficiency results from the model, were subsequently used to calculate the cost of electricity. Sensitivity analyses were conducted to correlate the concentrations of key impurities in the fuel gas feedstock to the cost of electricity. [Copyright &y& Elsevier]

The European Commission is planning to lower the particle cut off size down to 10 nm to consider the contribution of the sub-23 nm particles. Within the European project Sureal-23, a comprehensive study on the sub-23 nm particles was performed and novel technologies for their sampling and measurement were developed. One new proposed instrument, the Half Mini Differential Mobility Analyser (HM-DMA), was used in the present study. The investigation was carried out on a small direct/port fuel injection, spark ignition engine fueled with gasoline, ethanol and a 30 %v/v ethanol blend. Results highlighted a general reduction of the number and the size of the particles emitted by pure ethanol. The effect of the ethanol blend on sub-23 nm particle emissions was affected by the operating condition and the injection strategy. The extent of the VOF depends on the fuels as well as on the engine configuration and operating condition. Some differences were noted between the results from EEPS and HM-DMA ascribable to the different measurement principle and to the processes occurring in the dilution system. • Measure of the particles in the size range 10–23 nm. • A novel instrument for sub-23 nm particle emissions was employed. • Effect of sampling condition temperature on sub-23 nm particles was analyzed. • Volatile organic fraction of sub-23 nm particles emitted by both PFI and GDI SI engines was evaluated. • Particles emitted by gasoline, ethanol and a 30 %v/v of ethanol blend were compared. [ABSTRACT FROM AUTHOR]

The prospects of chars derived from the co-pyrolysis of waste polystyrene (WPS) and eucalyptus biomass at variable temperatures (300–550 °C), residence times (90–150 min) and proportions of WPS (w/w) (33% and 25%) for their potential use as a solid fuel were assessed. The production of char suggested an improved fuel quality compared to the raw feedstock because of reduced volatile and oxygen contents, along with an increase in the carbon and fixed carbon contents. While the properties of the char such as energy density (1.12–1.30), high heat value (28.03–32.5 MJ/kg) had their maximum values observed with 33% WPS content at 300 °C, fixed carbon (4.5–34.19%), fuel ratio (0.05–0.64) were maximum with 25% WPS content at 550 °C. Moreover, the energy yield of the char was higher than the mass yield. The chars produced at 300, 350 °C were observed to have O/C and H/C ratios similar to that of sub-bituminous and bituminous coal. Principal component analysis presented the variable effects of WPS on the properties of the char through physical inhibition and synergistic interactions below and above the complete volatilization temperature of WPS. [Display omitted] • The properties of char produced at different process parameters were compared. • Co-pyrolysis of Waste Polystyrene with Eucalyptus biomass enhanced the HHV, ED and EY of char. • The fuel value indices of the chars were >500 GJ/m3 with maximum high heat value of 32.5 MJ/kg. • Energy yield of the char was 11–23% higher than the mass yield. • The thermal properties of char indicated its strong potential as alternate solid fuel. [ABSTRACT FROM AUTHOR]

In this study, co-hydrothermal carbonization (co-HTC) of sewage sludge (SS) and lignocellulosic biomass was conducted at 220 °C for 1 h, and transformation behaviour of heavy metals during co-HTC, along with fuel properties, were investigated. The results showed that the majority of Cr, Ni, Cu and Zn was still accumulated in hydrochar during individual HTC of SS. The addition of lignocellulosic biomass could effectively reduce (F1+F2) fractions of Ni and Cr. Owing to the positive effect on the reduction of (F1+F2) fractions of Cu, the addition of lignin exhibited the lowest potential ecological risk index. Furthermore, compared with the hydrochar derived from SS, it was found that fuel ratio of hydrochar derived from co-HTC increased to 0.08─0.39 and high HHV (6.86─12.90 MJ/kg) was also achieved. The TGA results displayed that the combustion behaviors of hydrochars derived from co-HTC were expected to be safer and stable than that of hydrochar derived from SS. These findings offered an effective approach to convert SS into clean solid fuel with the targeted regulation of heavy metals. • Sewage sludge was treated with co-hydrothermal carbonization. • Chemical forms and ecological risk of HMs in hydrochar were evaluated. • Degree of risk of Ni and Cr decreased with the addition of CE, LIG and XY. • Degree of ecological risk of Cu reduced with the addition of LIG. • The hydrochar from co-HTC was an alternative solid fuel with upgraded quality. [ABSTRACT FROM AUTHOR]

Cotton textiles waste (CTW) was employed by hydrothermal carbonization (HTC) process catalyzed with FeCl 3 to prepare hydrochars. FeCl 3 could preliminarily lower the initial hydrothermal temperature, catalyze dehydration and decarboxylation to facilitate the formation of furfural derivatives. Subsequently, the synergistic effect of FeCl 3 and HTC regulated the side reaction pathway to convert more furfural derivatives into pseudo lignin structure, which further updating the thermal characteristics and combustion properties of hydrochars. The results demonstrated that the fuel ratio increased from 0.07 to 0.87 and the higher heating values (HHVs) of hydrochars became 1.05–1.67 times of CTW (18.63 MJ/kg). Moreover, FeCl 3 also enhanced the efficient conversion from volatile matters to fixed carbon and elevated the ignition temperature of hydrochars from 292.7 to 431 °C as compared to the CTW. Furthermore, the potential formation mechanism and development trend of the pseudo lignin in the process of HTC with FeCl 3 were also proposed. The study proposed a way to promote the formation of high value-added by-products in the HTC process, and also provided a novel approach to obtain a better combustion performance of clean solid fuel. Image 1 • Clean solid fuel prepared by hydrothermal carbonization with FeCl 3 was proposed. • FeCl 3 promoted the side reaction of hydrothermal transformation to pseudo lignin. • The pseudo lignin deposited on the hydrochars surface as a film structure. • Pseudo lignin-attached hydrochars emerged better fuel characteristics. [ABSTRACT FROM AUTHOR]

A numerical framework was carefully developed to simulate the combustion of heavy-fuel-oil (HFO) in a large-scale boiler. The present numerical solutions were compared with the measured data of a laboratory benchmark test and on-site operational data of the chosen HFO-fired boiler. Next, the developed framework was used to perform sensitivity analyses aiming to reduce the NO emission from the HFO-fired boiler without any adverse effect on its combustion performance. Practically, this study focused on re-adjustments of 24 working burners, which could control combustion in the HFO-fired boiler. The early outcome showed that the boiler NO emission and its combustion performance could be controlled via proper adjustments of air distributions within the three burners' stages and the swirl intensity. Although bigger mean droplet sizes and higher injection velocities reduced the NO emission considerably, it adversely led to much lower boiler's combustion efficiency. The present study eventually arrived at an optimal adjustment for the burners by reconsideration of the air distributions within the three burners' stages, the flame swirl intensity magnitude, and the fuel injection quality. The achieved optimal adjustment reduced the amount of NO emission by 30%, while the combustion efficiency would remain unaffected. • A numerical approach is given to study the combustion of heavy-fuel-oil in boilers. • The model is validated against a benchmark test and the on-site operational data. • Effect of burners' adjustments on NO emission and combustion efficiency is studied. • Air distribution in burners' stages and swirl intensity greatly affect NO emission. • The study arrives at 30% reduction in NO emission by suitable burners' adjustments. [ABSTRACT FROM AUTHOR]

Suspension-firing enjoys the great popularity in biomass-fired heat and power generation. Since it has the strictest requirement on fuel quality and particle size, cares must be taken in biomass handling. This paper reviews, combined with concrete cases, the development in biomass preparation methods for suspension-firing: the processes and their impacts on critical issues in biomass suspension-firing. The first-generation preparation method, based on raw biomass, was successfully used for biomass suspension co-firing at low shares and nowadays is mainly used for other combustion technologies, due to the large particles it produces. The second-generation method, based on biopellets, is commonly used in existing suspension-firing plants. It can reduce biomass particle size to 85% < 1 mm (maximum 3 mm), ensuring good ignition and particle burnout. 100% biomass suspension-firing is mainly for high-quality biomass and often uses additives to mitigate corrosion. To improve fuel rangeability, the third-generation method will be prevailing. It includes extra thermal pre-treatment for increasing the energy density and grindability of the feedstock. Suspension-firing trials of torrefied biopellets are performed at several power plants. It is too costly in the present energy market and can be promoted by a future regulatory condition change in favor of alternative solid fuel sources. • Development in biomass preparation methods for suspension-firing reviewed. • The application examples and pros and cons of the preparation methods presented. • Guidelines for biomass particle size reduction for pulverized fuel boilers given. • Measures to mitigate deposition/corrosion in biomass suspension-firing discussed. [ABSTRACT FROM AUTHOR]

The spray tip penetration is an important parameter to evaluate the fuel injection quality. This study presents an experimental investigation on the high-pressure diesel injection process of a common-rail injector under condition of varying pressures, particularly on the effect of the dynamic injection behavior on the fuel spray penetration. The injector delivery process is tested on a common-rail test rig, with an optical test rig to examine the diesel spray based on a constant-volume bomb (CVB) system. This process includes two stages: i.e., the opening stage and the keeping stage, while the two-stage injection momentum causes crucial influence on the fuel spray. Correspondingly, the fuel spray penetration also has two stages. In Stage I (the dynamic stage), the spray penetration sharply increases. In Stage II (stable stage), the spray penetration stably increases. When the injection pressure rises, the spray tip penetration increases, and the two-stage turning-point time is shorter. Considering this two-stage characteristic, an equation is proposed to predicate the spray tip penetration: it is based on the dynamic injection pressure for the dynamic period but the constant pressure differential for the stable period. The predicated spray tip penetration has good agreement with the test data. • An optical test rig is designed to observe the high-pressure diesel fuel injection in a CVB. • The spray tip penetration experiences two stages: the dynamic stage and the stable stage. • The two-stage spray tip penetration is affected by the two-stage injection process of the injector. • An equation of the spray tip penetration is proposed based on the two-stage feature. • As the injection pressure increases, the spray tip penetration increases but the turning-point time decreases. [ABSTRACT FROM AUTHOR]

The optimization of microwave-assisted hydrothermal carbonization for corn stalk was conducted to study the effects of reaction temperature (122.7–257.3 °C), residence time (4.8–55.2 min), and biomass loading (0.98–6.02 g/50 mL H 2 O) using the response surface methodology. The hydrochars produced from hydrothermal carbonization of cork stalk under different reaction conditions were characterized to understand their physical, chemical, and structural properties. Statistical analysis shows that the carbonization temperature is the dominant parameter determining the product yield as well as heating value and quality of hydrochar. Due to the interactive effects amongst the process parameters, hydrochar mass yield and heating value cannot be maximized simultaneously. The highest energy yield under the predicted optimum conditions of 181.9 °C, 39.7 min and 3.8 g/50 mL H 2 O reached 80.55%. The higher heating value of 22.82 MJ/kg was observed at 230 °C, 45 min and 2 g/50 mL H 2 O, which is 41% higher than that of the raw corn stalk. The characterization results reveal that the microwave-assisted hydrothermal carbonization is a viable process for producing hydrochar, which can be used as a direct solid fuel or auxiliary fuel. • Response surface optimization of microwave hydrothermal carbonization process was studied. • A comprehensive characterization and evaluation of corn stalk hydrochars are reported. • The maximium energy yield of the hydrochar reached 80.55%. • The optimized process can produce hydrochar as a high quality solid fuel. [ABSTRACT FROM AUTHOR]