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To investigate sulfur transformation during coal pyrolysis with char heat carrier (CHC), the effects of temperature, CHC/coal, and CHC production temperature were explored in a fluidized bed. The yield rates of sulfur in H2S (YH2S) and YCOS elevated with temperature. YCH3SH and Ychar‐S decreased, and temperature showed no significant effect on Ytar‐S. CHC inhibited sulfur transformation to the gas phase. More H2S and COS were fixed in mixed‐char in form of CaS by CHC, resulting in the increase of Ychar‐S. CHC was favorable for CH3SH decomposition. The inhibitory effect was enhanced with increasing CHC/coal. Higher production temperature inhibited the sulfur fixation capacity of CHC. CHC enhanced the decomposition of pyrite, organic sulfur, sulfate, and the yield of sulfide in mixed‐char. [ABSTRACT FROM AUTHOR]

A large number of aromatic substances can be found in so-called coal tar (containing >10,000 individual compounds), which is a mixture of heavy liquid fractions (dense viscous black liquor, tended to solidification) obtained after the pyrolysis of coal (solid product—coke, gas products, and light liquid products are also produced during the process). Volatile monocyclic aromatic hydrocarbons, which are naturally occurring in coal tar, can be exploited as premium raw materials for the production of graphene by chemical vapor deposition (CVD). Moreover, aromatic chemicals (compounds with benzene rings) can produce graphene at lower temperatures than other small-molecule gas feedstocks (for graphene growth via methane gas, the temperature must be at least 900 °C). The intermediate reaction mechanism involved in the creation of graphene from various temperature ranges of monocyclic aromatic hydrocarbons in benzene ring structures has long been a fascinating enigma. Accordingly, in this paper, we analyze the graphene growth pattern of benzene at different temperatures from 300 to 900 °C. For graphene synthesis in the lower temperature range (300~600 °C), analytical experiments show that benzene rings (almost) do not crack during the gas phase process. Thus, the structure of the benzene ring is directly coupled into graphene in the above temperature range. When benzene is more thoroughly transformed into tiny molecules that are deposited on the surface of copper foil at higher temperatures (700~900 °C), graphene is formed by a complex mixture of carbon sources, including gaseous small molecules (methane and ethane) and benzene. Based on the process above, we provide an alternative solution for the large-scale industrial preparation of graphene, with low energy consumption, via low-temperature synthesis of graphene by the CVD method using the coal tar carbon source at 500 °C, which is the optimal growth temperature of the benzene ring. [ABSTRACT FROM AUTHOR]

• Pressurized oxy-fuel combustion performance of a typical bituminous coal is investigated. • The thermodynamics parameters and the most probabilistic kinetic model for the pressurized oxy-fuel combustion process are analyzed. • Elevating pressure can significantly improve the combustion performance of coal but the promotion effect gradually alleviates. • The ignition mechanism transforms from heterogeneous to homogeneous when the oxygen concentration reaches 50% at 0.5 MPa. Pressurized oxy-fuel combustion is one of the emerging clean technologies that can efficiently separate and recover CO 2 , and this combustion mechanism differs significantly from atmospheric air combustion. In this paper, the effects of reaction conditions such as total pressure, oxygen concentration and atmosphere gas composition on the combustion characteristics of Xinjiang Bostan coal were investigated using thermogravimetric methods. Furthermore, the thermodynamics parameters and the most probabilistic kinetic model for the pressurized oxy-fuel combustion process were explored. The results showed that the system pressure rising from 0.1 to 1 MPa could enhance the combustion process of coal; however, when the system pressure exceeds 0.5 MPa, the promoting effect is clearly weakened. The ignition mechanism transforms from heterogeneous to homogeneous when the oxygen concentration reaches 50% at 0.5 MPa. The mechanism functions of pressurized oxy-fuel combustion reaction varied as the reaction progressed. In addition, the rise of pressure and oxygen concentration correspond to the higher chemical reaction order of pulverized coal combustion and the pressure has less influence on the reaction mechanism than oxygen concentration. The results obtained may assist with the optimization of pressurized oxy-fuel combustion and guide its industrial applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Combined cycle, biomass calcium looping gasification is proposed for a hydrogen and electricity production (CLGCC–H) system. The process simulation Aspen Plus is used to conduct techno-economic analysis of the CLGCC–H system. The appropriate detailed models are set up for the proposed system. Furthermore, a dual fluidized bed is optimized for hydrogen production at 700 °C and 12 bar. For comparison, calcium looping gasification with the combined cycle for electricity (CLGCC) is selected with the same parameters. The system exergy and energy efficiency of CLGCC–H reached as high as 60.79% and 64.75%, while the CLGCC system had 51.22% and 54.19%. The IRR and payback period of the CLGCC–H system, based on economic data, are calculated as 17.43% and 7.35 years, respectively. However, the CLGCC system has an IRR of 11.45% and a payback period of 9.99 years, respectively. The results show that the calcium looping gasification-based hydrogen and electricity coproduction system has a promising market prospect in the near future. [ABSTRACT FROM AUTHOR]

In order to understand the reaction mechanism of lignin pyrolysis, the pyrolysis process of guaiacol (o-methoxyphenol) as a lignin model compound was studied by free radical detection technology (electron paramagnetic resonance, EPR) in this paper. It was proven that the pyrolysis reaction of guaiacol is a free radical reaction, and the free radicals which can be detected mainly by EPR are methyl radicals. This paper proposes a process in which four free radicals (radicals 1- C6H4(OH)O*, radicals 5- C6H4(OCH3)O*, methyl radicals, and hydrogen radicals) are continuously rearranged during the pyrolysis of guaiacol. [ABSTRACT FROM AUTHOR]

Abstract To study the characteristics of positive and negative DC discharge under coal pyrolysis gas media at 20 °C–600 °C, the I V characteristics and the current composition are analyzed under different conditions. Due to the difference of ionization mechanism, the corona onset voltage of negative corona is lower than that of positive corona under air gas medium. Under non-electronegative gas media, no corona occurs during negative discharge. However, during positive discharge, with the increase of output voltage, three types of discharge are successively observed, namely corona, glow and arc. Under N 2 gas media and at 400 °C, the maximum collection efficiency of positive electrostatic precipitator is 98%, while that of negative electrostatic precipitator is 82%. When the collection efficiency is 70%, the energy consumption index of negative electrostatic precipitator is about 200 times higher than that of positive electrostatic precipitator. A linear relationship between I/V and V is observed and the ionic mobility can be calculated through the slope. At 350 °C, the ionic mobility under H 2 gas medium is 5.25 cm2/(V*s) while the ionic mobility under N 2 gas medium is 0.1 cm2/(V*s). The ionic mobility is proportional to the absolute temperature according to the discharge experimental data at 350 °C–600 °C. The factor β i , which is only related to gas media, is 0.0001653 cm2/(V*s*T) for N 2 and 0.0087308 cm2/(V*s*T) for H 2. These results assist in understanding the property of ESP at high temperatures. Graphical abstract Unlabelled Image Highlights • Under coal pyrolysis gas medium, corona only occurs in positive discharge. • Under N 2 gas medium, the positive ESP is better than negative ESP. • The ionic mobility under H 2 is about 52 times higher than that of N 2. [ABSTRACT FROM AUTHOR]

A two-stage system involving alkaline thermal gasification of cellulose with Ca(OH) 2 sorbent and catalytic reforming with Ni/Fe dual-functional CaO based catalysts is proposed and applied to enhance H 2 production and in-situ CO 2 capture. The results show that the H 2 concentration is maximized at a considerably lower temperature (500 °C) than commercialized biomass gasification processes, reducing energy consumption. Sol-gel method is deemed better than impregnation method for its lower cost and higher-concentration H 2 production. Among the prepared catalysts, sol-NiCa catalyst exhibits the best performance in CO 2 absorption, resistance to carbon deposition, and cyclic stability, creating maximum H 2 concentration (79.22 vol%), H 2 yield (27.36 mmol g−1 cellulose), and H 2 conversion (57.61%). Introduction of Ni rather than Fe on the CaO based catalyst promotes steam methane reforming at moderate temperature range of 400–600 °C, generating low contents of CH 4 (5.38 vol%), CO 2 (4.82 vol%), and CO (10.58 vol%). [Display omitted] • A two-stage system involving alkaline thermal gasification and catalytic reforming. • Sol-gel shows higher-concentration H 2 production and lower cost than impregnation. • Introduction of Ni rather than Fe on CaO catalysts promotes SMR at 400–600 °C. • Sol-NiCa catalyst exhibits good carbon deposition resistance and cyclic stability. • Maximum H 2 concentration (79.22 vol%) is achieved at moderate temperature of 500 °C. [ABSTRACT FROM AUTHOR]

Currently, there is no easy-to-use method for determination of catalytic active phase volume (APV). Therefore, the current study designed a calculation method by defining APV (α → β nm) as the difference in pore volume (α → β nm) between the catalyst support and the catalyst (without taking fine structure of the catalyst into account for simplicity). This new method was successfully validated through regression analysis of 15 catalysts (R2 > 0.97). Moreover, the couplings of pore structures and metal loadings on catalytic hydrogenation of reactants were quantitatively assessed based on the calculation of APV. The promotion or inhibition effect of one compound on hydrogenation of other compounds may also vary with the couplings of metal loading and pore structure, but it wasn't taken into account in this study. The key segmented APVs (SAPVs) in various pore sections for hydroconversion of reactants were determined using a stepwise linear regression model at the 95% confidence level. The findings showed that the SAPVs in the pores with a pore size of 5–10 nm and 10–20 nm were responsible for hydroconversion of quinoline and most of the aromatic compounds, respectively. The predicted key SAPVs were consistent with the experimental observations, which demonstrated availability of the proposed APV. [Display omitted] • The QM-based calculation methods for kinetic diameters of molecules were provided. • Coupling effects of metal loading and pore structure were quantitatively assessed. • The catalytic active phase volume (APV) was firstly proposed and validated. • The stepwise linear regression model was used to find the key segmented APVs. • The found segmented APVs accorded well with the experimental observations. [ABSTRACT FROM AUTHOR]