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Coal-based mercury pollution from power plants has received increasing attention. In a previous study, high iron and calcium coal ash (HICCA) was found as a promising oxygen carrier (OC) for chemical looping combustion (CLC). The purpose of this study was to investigate the catalytic effect of HICCA on Hg0 removal as well as the impacts of several gas impurities, such as HCl, SO2, and NO. Experiments on Hg0 removal efficiencies for different atmospheres were performed in the fixed-bed reactor at 850 °C. Based upon the characterization of BET, SEM, XRD, XPS, and EDS of reaction products, the reaction mechanisms of different gases with the HICCA samples were established. The mechanisms were further explained using the thermodynamic equilibrium calculations. The experimental results showed that the Hg0 removal efficiency using HICCA was 11.60%, while the corresponding value in the presence of 50 ppm HCl was 90.46%. Hg0 removal by HICCA involving HCl is mainly attributed to homogeneous reaction between Hg0 and HCl as well as the formation of reactive species (Cl, Cl2, Cl2O, O, S, and SCl2) through the reactions of HCl with Fe2O3 and CaSO4 in HICCA. The formation of C–Cl bond is not the main pathway for the promotional effect of HCl on Hg0 removal. SO2 played a negative role in Hg0 removal by HICCA. The inhibition of SO2 may be attributed to its effect on the reduction of Fe2O3 and its bonding with C–O, COOH, and C(O)–O–C. NO enhanced Hg0 removal by HICCA primarily through the homogeneous reactions of Hg0 with N2O and O. In addition, NO also interacted with HICCA and promoted the heterogeneous oxidation of Hg0 by producing more C–O, C=O, and COOH/C(O)−O−C on HICCA surface. This study proved the effectiveness of HICCA on Hg0 removal in iG-CLC and revealed the mechanisms of the interaction between HCl/SO2/NO and MxOy/CaSO4 as well as carbon-oxygen groups. [ABSTRACT FROM AUTHOR]

To solve the ash deposition problem caused by burning high‐calcium Zhundong coal (ZDC), the addition of vermiculite is a promising solution. However, complete mechanisms of vermiculite addition reducing ash deposition are still unknown. In this paper, the effect of vermiculite on sodium emission, ash fusion characteristics, and mineral transformation is investigated. The results show that although vermiculite, with limited Na capture capacity, lowers the ash fusion temperatures (AFTs), it can greatly reduce ash deposition. In the combustion of ZDC, calcium‐bearing minerals will react with clay minerals and then convert to molten glassy phase. Those molten minerals will take high melting point minerals, Ca2Al2SiO7 and CaMgSi2O6, as bone, showing slagging phenomenon with high AFTs. When vermiculite is introduced, the main reaction products are Ca2MgSi2O7 and Mg2SiO4 and that reduces the extent of molten minerals formation. The main ash product transforming from Ca2Al2SiO7 to Ca2MgSi2O7 leads to the decrease of AFTs. The initial ash deposition with Ca2Al2SiO7 still happens; however, vermiculite addition makes it hard for ash to grow on the existing ash deposit. The results of FactSage software agree with the experimental ones, and the proportion of slag decreases by 36% with vermiculite at 1250°C. [ABSTRACT FROM AUTHOR]

We develop a finite element dynamic earthquake simulator, EQsimu, to model multicycle dynamics of 3-D geometrically complex faults. The fault is governed by rate- and state-dependent friction (RSF). EQsimu integrates an existing finite element code EQdyna for the coseismic dynamic rupture phase and a newly developed finite element code EQquasi for the quasi-static phases of an earthquake cycle, including nucleation, post-seismic and interseismic processes. Both finite element codes are parallelized through Message Passing Interface to improve computational efficiency and capability. EQdyna and EQquasi are coupled through on-fault physical quantities of shear and normal stresses, slip-rates and state variables in RSF. The two-code scheme shows advantages in reconciling the computational challenges from different phases of an earthquake cycle, which include (1) handling time-steps ranging from hundredths of a second to a fraction of a year based on a variable time-stepping scheme, (2) using element size small enough to resolve the cohesive zone at rupture fronts of dynamic ruptures and (3) solving the system of equations built up by millions of hexahedral elements. EQsimu is used to model multicycle dynamics of a 3-D strike-slip fault with a bend. Complex earthquake event patterns spontaneously emerge in the simulation, and the fault demonstrates two phases in its evolution. In the first phase, there are three types of dynamic ruptures: ruptures breaking the whole fault from left to right, ruptures being halted by the bend, and ruptures breaking the whole fault from right to left. As the fault bend experiences more ruptures, the zone of stress heterogeneity near the bend widens and the earthquake sequence enters the second phase showing only repeated ruptures that break the whole fault from left to right. The two-phase behaviours of this bent fault system suggest that a 10° bend may conditionally stop dynamic ruptures at the early stage of a fault system evolution and will eventually not be able to stop ruptures as the fault system evolves. The nucleation patches are close to the velocity strengthening region. Their sizes on the two fault segments are different due to different levels of the normal stress. [ABSTRACT FROM AUTHOR]

Mud volcanoes are significant indicators of neotectonic activity and have important research significance. Mud volcanoes can not only be used as an important index for the long‐term evaluation of oil and gas fields but are also an important symbol for locating gas hydrates in the seabed. Additionally, the eruption of mud volcanoes will affect drilling, pipe laying, and other projects, and the eruption of large amounts of methane gas can also cause greenhouse effects and climate change. The trigger mechanisms of mud volcanoes have always been a focus of debate among geologists. In recent years, many scholars have argued that mud volcanoes are triggered by earthquake activity. However, the stress and strain caused by earthquakes and their control mechanisms on the eruption of mud volcanoes still require further study. This paper is based on the calculated results of static stresses caused by the M5.5 Wusu earthquake of May 2, 1995, the M5.4 Shawan earthquake of January 9, 1996, the M5.3 Shihezi earthquake of February 14, 2003, and the M6.3 Xinyuan–Hejing earthquake of June 30, 2012, on the Horgos, Dushanzi, Aiqigou, and Baiyanggou mud volcanoes distributed in the southern margin of the Junggar Basin, NW China. The calculated static stresses, the earthquake response characteristics of these four groups of mud volcanoes, and the continuous observational data of the Horgos mud volcanoes showed that static stresses from these earthquakes did not reach the triggering threshold, though the mud volcanoes exhibited a good relationship with earthquakes. We speculate that static stress may not be the main triggering mechanism for the mud volcanoes and that the mechanisms of earthquake triggering may be divided into two types: (a) For a mud volcano in a critical state before an earthquake, dynamic stress changes may trigger eruption of the mud volcano by increasing permeability and mobilizing magma; (b) for mud volcanoes that have not yet reached the critical eruption state before an earthquake, both static and dynamic stresses play roles in their activities. [ABSTRACT FROM AUTHOR]

The removal of ibuprofen (IBP) from wastewater is a hot topic in both academic and industrial fields. Herein, we reported a novel eco-friendly absorbent C3N4/soot composite via a simple one-step pyrolysis process, which had high adsorptive activity for the removal of IBP from wastewater. Adsorption kinetic and isotherm data of the adsorption process were investigated. The adsorption capacity at room temperature for low equilibrium concentration (10 mg/L) was as high as 104 mg/g, which was very similar to the maximum adsorption capacity (148.81 mg/g). The pseudo-first-order, pseudo-second-order, and the intraparticle diffusion models could best describe adsorption kinetics of IBP on 7 wt% C3N4/soot, and adsorption isotherm is well fitted to Langmuir model. Thermodynamic parameters (ΔH, ΔG, and ΔS) indicated that IBP adsorption on C3N4/soot composite was spontaneous and endothermic. Moreover, the potential adsorption mechanism of C3N4/soot composite for the adsorption of IBP was proposed. The 7 wt% C3N4/soot composite exhibited much higher adsorptive activity and still showed a relatively high adsorption stability even after five cycles, which were potentially suitable for high efficiency and low-cost water purification. [ABSTRACT FROM AUTHOR]

Highlights: [•] Experiments in a well-stirred reactor show three pH regions of SO2 absorption. [•] The operational pH of sodium quench units is recommended to be in region 2. [•] Operating in region 2 achieves a high absorption rate and low sodium loss. [•] The operational window narrows with the increase of sodium solution concentrations. [•] The operational window narrows at low partial pressure of SO2. [Copyright &y& Elsevier]

Abstract: Oxy-fuel combustion is an emerging technology to mitigate CO2 emissions from power plants. Compared with other CO2 capture technologies, gas impurities in oxy-fuel flue gas are highly concentrated, among which SO2 is of concern. Dynamic transient experiments have been conducted in a semi-batch well stirred reactor (WSR) relevant to the conditions of the flue gas scrubbers operating at atmospheric pressure prior to CO2 compression in oxyfuel technology for CCS. SO2 in N2 as well as in CO2 were considered. The initial pH of the solutions considered was those of NaOH (with concentrations of 0.01M and 1M), Na2CO3 (0.005M) and NaHCO3 (0.01M). Analysis of the liquid solutions showed that the concentration of bicarbonate increases with pH at a pH larger than 5.5 indicating a loss of effectiveness of the sodium reagent. A practical discharge pH of the liquid discharge from the scrubber is also greater than 4 as at a lower pH the absorption rate of SO2 reduced. This operating range is consistent with the reported operating range of the scrubber used in the Vattenfall oxyfuel pilot plant. [Copyright &y& Elsevier]

Liquid‐phase mass transfer coefficient is important for characterization of gas–liquid reactors and relevant to the modelling of gas absorption rate. Both direct and indirect methods have been used to obtain this coefficient. However, these methods have not been compared on the same basis. Liquid‐phase mass transfer coefficients were measured in three ways—(a) CO2 absorption into water, (b) SO2 absorption into 1 kmol m−3 of HCl, and (c) O2 absorption into Na2SO3—and then normalized to the coefficient for SO2. Based on transient experiments, the normalized values for liquid‐phase mass transfer coefficient obtained from three methods are in turn of kL,O2>kL,SO2>kL,CO2. The fluxes of SO2 predicted from three methods were further compared with the experimental values measured in SO2‐NaOH system. The fluxes predicted from kL,SO2 agreed well with the experimental values, whereas those from kL,CO2 and kL,O2 were significantly lower or higher. Therefore, the liquid‐phase mass transfer coefficient is preferably obtained from the targeted gas. Modelling on the flux of SO2 demonstrates the transition of controlling regions against pH. At pH above 4, the gas side resistance is larger than the liquid side, whereas at pH below 4, the gas side resistance is smaller than the liquid side. [ABSTRACT FROM AUTHOR]

A bubbling reactor is an important type of gas scrubber to reduce SO 2 emissions in maritime shipping. Both experiments and simulations were conducted to study the relationship between the periodic gas bubbling process and SO 2 concentration at the outlet of the reactor, and the entrainment of liquid droplets on SO 2 absorption. The accuracy of the model was verified by comparing the bubble size, the depth of bubbles injected into the water, and the SO 2 concentration obtained in both experiments and simulations. The gas bubbling process is accompanied by bubble formation, rise, and collapse. The gas bubbling period is affected by the disturbance of the liquid level. The period of the SO 2 concentration at the outlet of the gas bubbling reactor is smaller than that at the gas jar outlet which acts as the gas buffering region. The amounts of water carried out of the bubbling reactor by the gas bubbling process increase with the gas flow rates. The droplets and liquid film in the gas jar and the connecting tube play an important role in the absorption of SO 2 . This study encourages more research to reduce the fluctuation of SO 2 concentration and consider droplet entrainment in the design of bubbling reactors.