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An experimental-scale electrostatic precipitator (ESP) was built to investigate the influence of temperature and gas media on collection efficiency and energy consumption. High temperature was harmful to the performance of the ESP and had a considerable influence on large particles. The maximum collection efficiency was lower and energy consumption was higher under coal pyrolysis gas media than under air. Two improvement methods, namely, gas media conditioning and positive polarity power supply, were studied in this work. Both methods can improve the performance of high-temperature ESP under coal pyrolysis gas media. The improvement in collection efficiency under the effect of gas conditioning decreased and that under the effect of a positive power supply increased with the increase in temperature. Gas conditioning and positive power supply increased the maximum collection efficiencies of the ESP at 600 °C under coal pyrolysis gas media by 3.0% and 11.8%, respectively. Unlabelled Image • High temperature was harmful to the performance of the ESP. • The performance of ESP in coal pyrolysis gas is inferior to that in air. • Gas conditioning and positive power supply can improve the performance of ESP. [ABSTRACT FROM AUTHOR]

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]

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]

Hydrogen production from rice husk was carried out via a two-stage system combining CLG (calcium looping gasification) using Ca(OH) 2 adsorbent in a bubbling fluidized bed and catalytic reforming with Ce–Ni/γAl 2 O 3 catalyst in a connected fixed bed. The results show that the maximum H 2 concentration (69.16 vol%) and H 2 yield (11.86 mmol g−1 rice husk) are achieved at Ca/C (Ca(OH) 2 to carbon molar ratio) = 1.5, H 2 O/C (H 2 O to carbon molar ratio) = 1.5, T g (gasification temperature) = 500 °C, T c (catalytic temperature) = 800 °C. The supplementation of fresh Ca(OH) 2 at Ca/C of 0.5 during calcination helps to activate the regenerated CaO by hydration, maintaining its carbonation activity and CO 2 adsorption. Ce–Ni/γAl 2 O 3 catalyst promotes water gas shift (WGS), steam methane reforming (SMR), and C 2 –C 3 hydrocarbons reforming, also exhibits excellent activity stability to maintain H 2 concentration and H 2 yield above 67.21 vol% and 11.67 mmol g−1 rice husk , respectively, during 5 lifetime tests. • Staged catalytic gasification of rice husk in a fluidized bed for H 2 -rich gas. • Ca(OH) 2 adsorbent promotes WGS and hydrocarbons reforming at a moderate temperature. • Fresh Ca(OH) 2 supplement during calcination activates regenerated CaO by hydration. • Ce–Ni/γAl 2 O 3 catalyst promotes WGS, SMR, and C 2 –C 3 hydrocarbons reforming reactions. • Ce–Ni/γAl 2 O 3 catalyst shows excellent activity stability with low carbon deposition. [Display omitted] [ABSTRACT FROM AUTHOR]

Performing online evolution analysis of tar in actual pyrolysis process is a major challenge. In this work, the effects of heating rate (HR) on evolution curves of in-situ tar for low-rank coals pyrolysis were investigated in a novel laboratory bench. The escape law of volatiles was obtained, the influence of HR on secondary reactions was analyzed, the association between products and molecular structures was constructed, and pyrolysis mechanism was deduced. Aliphatic hydrocarbons (except dienes), phenols, and oxygenated compounds have only one peak, while dienes and aromatics have multiple peaks throughout the pyrolysis process. The first peak is attributed to coal primary pyrolysis. At increased HRs, the second peak for 1∼2ring aromatics is from the cracking of primary volatiles, and that for 3∼4ring aromatics from coal continued cracking. The proportion of phenols and oxygenated compounds decreases, aromatics increases, and aliphatic hydrocarbons varies for different coals. Generally, HR increases the yield of primary volatiles by enhancing coal primary pyrolysis, elevates the proportion of light aromatics by promoting secondary cracking and aromatization of primary volatiles, reduces char yield by inhibiting condensation reactions throughout the pyrolysis process. The similar macromolecular structures of different coals make the evolution curve versus HRs follow a common law. [Display omitted] • Dienes and aromatics have more than one evolution peaks during pyrolysis process. • The first peak of tar components is attributed to the coal primary pyrolysis. • As heating rate rises, the second peak of 1∼2ring aromatics is from the cracking of primary volatiles. • As heating rate rises, the second peak of 3∼4ring aromatics is from the cracking of coal at high temperatures. • The mechanism of heating rate on different low-rank coals remains consistent. [ABSTRACT FROM AUTHOR]

In this study, the effects of coal blending ratio, pyrolysis temperature, pyrolysis atmosphere and coal particle size on the quality of pyrolyzed char were investigated via a combination of orthogonal experimental design and grey relational analysis. Coal-XG and Coal-LL were pyrolyzed under various conditions to produce chars which were characterized to ascertain their properties such as chemical structure and reactivity. The results indicated that the pyrolysis temperature has the most significant impact on the quality of the char, followed by the pyrolysis atmosphere, coal blending ratio and coal particle size. The increase in pyrolysis temperature not only diminished char yield but also accelerated the consumption of oxygen-containing functional groups and the polycondensation of small aromatic ring structures throughout the reaction process. This led to a reduction in the reactivity of pyrolyzed char and the establishment of a more ordered structure. Meanwhile, the involvement of CO 2 and H 2 O prevented the condensation of small aromatic rings and fostered the generation of additional oxygen-containing functional groups, which resulted in lower yield and higher reactivity of the char under these two atmospheres. Through systematic analysis, only the Raman characteristic parameter I (Gr+VL+Vr) /I D exhibited a strong positive linear correlation with char reactivity, making it a reliable indicator for characterizing the reactivity of char. • The orthogonal design was used to study four response factors. • GRA was used to find optimal conditions and impact ranking of different factors. • Linear regression was applied to relate Raman/FTIR parameters to reactivity. • Blend experiments were conducted with two coking coals. [ABSTRACT FROM AUTHOR]

An integrated model was developed to investigate the effect of temperature on the particle re-entrainment in a high-temperature electrostatic precipitator (ESP). The numerical model considered the electric field, flow field, particle migration, and particle re-suspension due to the rupture of static equilibrium. The electric and flow field distributions at different temperatures were investigated. The minimum critical shear velocity needed to detach high-temperature deposited particles from the plate surface was calculated and discussed. On these basis, five types of ESPs with collection plates of different configurations were compared. The results show that high temperatures will exacerbate particle re-entrainment caused by airflow scouring and electrostatic lifting by enhancing the ionic wind and reducing particle resistivity. The hole-type plate may be a better plate form to reduce re-entrainment in the high-temperature ESPs, as it creates a low velocity, low electric field region in the near-plate region. [Display omitted] • A modified high-temperature ESP model involving particle re-entrainment was developed • The effect of temperature on the electric and flow field was investigated numerically. • The effect of temperature on the particle re-entrainment was evaluated. • The effectiveness of different types of collection electrodes in reducing particle re-entrainment was evaluated. [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]

• A modified ESP model suitable for high temperature gas was established. • The effect of temperature on ESP performance was investigated numerically. • An optimized ESP with assistant electrodes was developed and compared with the conventional ESP. High-temperature electrostatic precipitators (ESPs) are a potentially effective technology for purifying high-temperature gases. In this study, a comprehensive numerical model was developed to investigate the electric field and particle migration characteristics of an ESP at temperatures ranging from 400 to 600 °C. Moreover, an optimized ESP with assistant electrodes for improved high-temperature particle capture was proposed. The electric field, flow field and particle capture characteristics of the two types of ESPs were compared to demonstrate the superiority of the optimized ESP. Results indicated that high temperatures had a negative impact on ESP performance. As the temperature increased, the operating voltage of the ESP decreased, leading to decreases in both the electric field strength and space charge density. The effective migration velocity of the particles also decreased with increasing temperature, and the inhibitory effect of high temperature on particle capture increased with increasing particle size. The optimized ESP with assistant electrodes exhibited more favorable electric field and flow field characteristics for particle capture compared to those of the conventional ESP. The optimized ESP exhibited higher electric field strength, which increased the electric field force on the particles and promoted particle capture. Meanwhile, the space charge density of the optimized ESP was lower, effectively inhibiting the occurrence of back corona. Moreover, the optimized ESP enhanced the ionic wind downstream of the discharge electrode, thereby promoting particle migration towards the collection electrode. Consequently, the ESP with assistant electrodes effectively improved the collection efficiency. [ABSTRACT FROM AUTHOR]

[Display omitted] • The transformation paths of sulfur during coal steam gasification with CaO addition was identified. • The release characteristics of H 2 S were monitored online. • Factors which might affect the sulfur transformation were analyzed in detail. To investigate the effects of temperature, Ca-based absorbent (CaO) and atmosphere on the sulfur transformation characteristics in coal steam gasification, experiments were conducted in a fixed-bed reactor. As temperature increased from 600 °C to 750 °C, H 2 S-S (sulfur in H 2 S) was elevated by 21.86% and absorbent-S decreased by 7.66%. More gaseous sulfur was captured by organic groups to form organic sulfur in char at higher temperature. CaO promoted the sulfur conversion, and played the role of gaseous sulfur absorbent at the same time, and showed an ability of organic sulfur removal. CaO slowed down the H 2 S release by reacting with it to form CaS, resulting in that the peak concentration of H 2 S without CaO reached 1026.7 ppm, which decreased to 426.3 ppm with CaO. The increase in Ca/C promoted the sulfur conversion slightly and reduced the sulfate content in char. Compared with inert atmosphere, H 2 S-S in the steam atmosphere increased by 35.07%, while absorbent-S decreased by 23.42%. The solid–solid reaction mechanism is more suitable for the sulfate transformation in inert atmosphere, while the gas–solid reaction mechanism is more suitable in steam atmosphere. The sulfur conversion in inert atmosphere was lower, but sulfate had a higher decomposition rate. [ABSTRACT FROM AUTHOR]

In this study, a numerical model of an electrostatic precipitator (ESP) suitable for high-temperature flue gas was established using COMSOL Multiphysics, and the effects of temperature and H 2 O concentration on the high-temperature ESP performance were studied. The results showed that, at the same voltage, increasing the temperature increased the negative ion density, thereby improving the particle charge and collection efficiency. However, increasing the temperature led to a decrease in the maximum operating voltage of the ESP, which reduced the negative ion density and electric field intensity at the maximum operating voltage and weakened the diffusion and field charges of the particles, leading to a further decrease in the maximum collection efficiency. Increasing the H 2 O concentration in the flue gas increased the negative ion density and, thus, enhanced the diffusion charge of the particles, which helped improve the collection efficiency. [Display omitted] • A modified ESP model suitable for high temperature gas was established. • The plasma model was used to simulate corona discharges in the ESP. • The effect of temperature on ESP performance was studied numerically. • The effect of H 2 O concentration in flue gas on ESP performance was studied. [ABSTRACT FROM AUTHOR]

In this study, the effect of pressure on the pyrolysis characteristics of Naomaohu coal and the physicochemical properties of char during slow pyrolysis is evaluated, and the mechanism of pressure is explored. The results show that the influences of pressure on char yield and physical properties are reflected in both promoting and inhibiting effect, and the latter is more obvious with the increasing temperature. As the pressure increases, the char yield first reduces and then improves, and at 600 °C and 800 °C the minimum yields are in 1.0 MPa and 0.1 MPa, which are 57.48% and 54.04%, respectively. The S BET of char increases first and then decreases. At 800 °C, the S BET of char increases from 7.86 m2/g at 0.1 MPa to 19.81 m2/g at 0.5 MPa and then decreases. The effect of pressure on the chemical properties of char is relatively simple. As the pressure rises, the content of functional groups in char reduces and the degree of graphitization enhances. The TG-DTG curve, XPS, BET, SEM test, experiments on the pressurized micro-fluidized bed reaction analyzer and pressurized pyrolysis-gas chromatography/mass spectrometry show that the pressure mainly affects the pyrolysis process by affecting the secondary reaction of the primary volatiles in the particle and is related to temperature. • The effect of pressure on pyrolysis process has two kinds of promotion and inhibition. • The inflection pressure point from promotion to inhibition is regulated by temperature. • As the pressure increases, the char yield and S BET both rise first and then decrease. • The graphitization degree of char is deepened with pressure. • Pressure mainly affects the pyrolysis process by affecting the secondary reaction of tar. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two-stage steam gasification and catalytic reforming of rice husk for H 2 -rich gas. • Ce 0.7 Ni 1 Ca 5 catalyst achieves 85.81 vol% H 2 with H 2 yield of 35.82 mmol g-1 biomass. • Ce 0.7 Ni 1 Ca 5 exhibits excellent cyclic stability and inhibition of carbon deposition. • High oxygen transport capacity of CeO 2 helps to promote WGS and SMR reactions. • CeO 2 prevents the sintering of NiO and CaO particles, stabilizing CO 2 sorption. Hydrogen-rich gas production from rice husk via steam gasification and catalytic reforming using CeO 2 -modified Ni-CaO sorption bifunctional catalysts synthesized by sol–gel method in a two-stage system was investigated. The results show that the Ce 0.7 Ni 1 Ca 5 catalyst achieves maximum H 2 concentration (85.81(±0.39) vol.%) and H 2 yield (35.82(±0.28) mmol g-1 biomass) under a condition of 500 °C, S/C (steam/carbon in biomass) molar ratio of 5, catalyst/biomass mass ratio of 2.5, producing the lowest content of CO 2 (3.62(±0.16) vol.%), CO (4.27(±0.11) vol.%), CH 4 (4.49(±0.18) vol.%), and C 2 -C 3 (1.81(±0.09) vol.%), correspondingly. Ce 0.7 Ni 1 Ca 5 also exhibits excellent cyclic stability in H 2 production, CO 2 sorption, and inhibition of carbon deposition. The H 2 concentration and H 2 yield remain above 81.88 vol% and 32.11 mmol g-1 biomass , respectively, and CO 2 emission keeps below 4.85 vol% during 10 cyclic tests. The carbon deposition of Ce 0.7 Ni 1 Ca 5 is only about 30% of that of Ni 1 Ca 5 after 10 cycles and hardly increased after 5 cycles. It is found that well-dispersed CeO 2 can effectively prevent the sintering of NiO and delay agglomeration of CaO species, stabilizing CaO carbonation and CO 2 sorption, and the strong Ni-O-Ce interaction induces the creation of oxygen vacancies that facilitate the fracture of O–H bonds of water for the formation of H 2. Furthermore, the high oxygen transport capacity of CeO 2 not only forms abundant mesopores structure to promote WGS and SMR reactions for enhancing H 2 production, but also contributes to reforming the carbon deposited on the catalyst surface by lowering the oxidation temperature of amorphous carbon containing low-molecular aromatic or aliphatic compounds with lower degree of graphitization. [ABSTRACT FROM AUTHOR]

Pyrolysis polygeneration technology is a good way to realize clean and efficient utilization of low-rank coal and heat carrier is a key factor. Aspen Plus is used to establish low-rank coal pyrolysis staged conversion polygeneration technology with semi-coke heat carrier based on dual-fluidized bed (CPSCPC-DFB), which couples with ultra-supercritical semi-coke powder furnace for power generation. Three processes are simulated to co-produce methanol (CPSCPC-DFB-M), synthetic natural gas (CPSCPC-DFB-S) and hydrogen (CPSCPC-DFB-H). Mass and carbon balance are established, techno-economic, environmental and sensitivity analysis are carried out, and the comparison with ultra-supercritical coal-fired power plant (SCFP) is made. The results show that the comprehensive performances of CPSCPC-DFB-M, CPSCPC-DFB-S and CPSCPC-DFB-H are significantly better than those of SCFP in energy loss (49.37%, 47.33%, 45% and 55.6%), CO 2 emissions (2.07, 2.12, 2.22 and 2.52 kg/kg coal), internal rate of return (23.24%, 21.83%, 29.52% and 17.56%). Although the total investment of CPSCPC-DFB is much higher than SCFP, the net present value is better than SCFP. Comparing the three polygeneration systems, the total investment and CO 2 emissions of CPSCPC-DFB-H are slightly higher than those of other two systems, but CPSCPC-DFB-H has absolute advantages in economy. Sensitivity analysis shows that the anti-risk ability of the polygeneration systems are significantly improved. [Display omitted] • A dual-fluidized bed pyrolysis polygeneration system with semi-coke heat (CPSCPC-DFB) carrier is established. • The CPSCPC-DFB can co-produce electricity, oil and chemical products. • The CPSCPC-DFB produced H 2 has high efficiency (53.99%) than traditional plants (42.8%). • The IRR of CPSCPC-DFB produced H 2 (29.52%) is better than traditional plants (17.56%). • The anti-risk ability of the polygeneration systems are significantly improved. [ABSTRACT FROM AUTHOR]

In order to investigate the pressurized isothermal pyrolysis characteristics of coal, the effect of pressure on gas release characteristics and the kinetics of pressurized isothermal pyrolysis are explored for the first time in a pressurized micro-fluidized bed reaction analyzer (P-MFBRA). This work finds that the yields of CO 2 , CO, CH 4 , and H 2 increases with temperature and pressure. The difference in the order of gas-releasing reduces as temperature and pressure rises, but that of gas-ending first decreases and then increases with pressure. The most probable mechanism functions of CO 2 , CO and CH 4 change from shrinking core model to homogeneous model at 1 MPa, 0.8 MPa and 0.5 MPa, respectively, showing that reaction is controlled by chemistry under low pressure but affected by diffusion effect with elevating pressure. The rate constant and activation energy (Ea) of each gas appear an increasing-decreasing tendency and the difference between Ea of each gas reduces with pressure. Compared with non-isothermal experiments, the Ea (20.8–475 kJ mol−1) and pre-exponential factor in P-MFBRA are less than those (70–150 kJ mol−1) in the pressurized thermogravimetric analyzer (P-TGA), indicating P-MFBRA can effectively reduce the diffusion inhibition, and the kinetics obtained is close to the reaction in industrial fluidized bed reactor. [Display omitted] • The effect of pressure on gas formation is inconsistent at different temperatures. • It is affected by chemistry but diffusion at low and high pressure respectively. • The activation energy appears an increasing-decreasing trend with pressure. • Pressurized micro-fluidized bed can reduce the diffusion inhibition of reaction. • Pressurized isothermal pyrolysis is first done in pressurized micro-fluidized bed. [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]

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]