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The combustion of a single boron particle contains three continuous macroscopic processes, including ignition delay, ignition and combustion. Studies show that among these processes, the intermediate ignition process has the most complicated kinetic mechanism. On the other hand, conventional models have serious shortcomings to simulate this process. The main challenges in this regard are indeterminate initial thickness of the surface oxide layer, incomplete diffusion mechanism in the surface oxide layer, and neglected effects of the pressure and particle size on the control mechanism. In order to overcome the drawbacks of existing ignition models, a comprehensive kinetic ignition model is developed in the present study. To this end, the dual-beam focused ion beam micro/nanofabrication system is applied to etch and cut the heat-treated boron particles into slices. Then, the scanning transmission electron microscope with collateral energy dispersive spectrometer is applied for analyzing the microstructure and elementary composition of the slice. It is found that the average thickness of the surface oxide layer is higher than earlier assumed values, and the bidirectional diffusion mechanism of boron and oxygen in the liquid boron oxide is confirmed. During the model development, seven heterogeneous global reactions and two vapor-phase reactions are used in total for analyzing the kinetic mechanisms. In the present study, different indicators, including the vaporization process, O2 reactions, and H2O reactions on the internal and external surfaces of the binary oxide layer are investigated. Moreover, the conservation laws of mass and energy are used for the establishment of governing equations. Then, the accuracy of the developed model is evaluated by comparing the obtained results for the ignition time with that of the experiment, which shows a reasonable consistency between them. Then, the proposed model is applied to investigate the ignition characteristics of boron particles. Effects of different parameters, including the environment temperature, O2 concentration, and H2O concentration are studied on the ignition time. It is concluded that the established model, which is named as the nuclear shell (N-S) model is a powerful scheme to better understand the ignition mechanisms and characteristics of boron particles and can be further applied in the field of computational fluid mechanics.

Aluminum hydride (AlH3) exhibits attractive properties, such as high hydrogen/energy storage, relatively good stability, and low dehydrogenation temperature. Thus, AlH3 has appreciable prospects as a component in solid propellant for promoting the specific impulse of rocket engines and for effectively reducing the erosion of engine nozzles. The TG-MS, SEM, XRD, XPS, and EDS results show that the thermal reaction of AlH3 is divided into three stages: (1) Dehydrogenation (below 210 °C, 2AlH3→2Al+3H2) starts from the inherent defects on the surface with an incomplete decomposition due to the passivation reaction in which an amorphous Al2O3 layer is formed to encapsulate the contained hydrogen. This is accompanied by nucleation and growth of Al nuclei from the outer particles to the inner particles and the formation of H2O via oxidation of the generated hydrogen. (2) The primary oxidation of Al (210–650 °C, 4Al+3O2→2γ-Al2O3) is attributed to a discontinuous layer of γ-Al2O3, which is transformed from amorphous Al2O3 that results in the reaction of naked residual Al and O2. (3) The secondary oxidation of residual Al (above 650 °C, 4Al+3O2→2α-Al2O3) occurs because of the crystal conversion from γ-Al2O3 to α-Al2O3, which leads to the shrinkage of the oxide shell and to the formation of cracks. Also, melting of residual Al breaks the shell, and this induces further oxidation. The results obtained for the microscopic kinetics mechanisms of dehydrogenation and oxidation of AlH3, show a clear direction for research regarding modifications of AlH3 as the theoretical foundation and are beneficial for the wide use of AlH3 in applications such as solid propellant as an energetic material and as a hydrogen source for fuel cells.

The ignition and combustion characteristics of a single 20 (% by weight) Al/n-Heptane nanoslurry fuel droplet with oleic acid as surfactant was studied under the laser ignition model. The i...

Nanofluid fuels are promising fuels in the fields of spaceflight and aviation. Their stability is a critical constraint for potential applications. Oleic acid can enhance the stability of nanofluid...

Mining industries worldwide have inevitably resorted to exploiting resources from the deep underground. However, traditional mining methods can cause various problems, e.g., considerable mining difficulty, environmental degradations, and frequent disastrous accidents. To exploit deep resources in the future, the concept of mining must be reconsidered and innovative new theories, methods, and technologies must be applied. To effectively acquire coal resources deeper than 2000 m, new theoretical and technological concepts about deep in situ fluidized mining are required. The limits of mining depth need to be broken to acquire deep-coal resources in an environmentally friendly, safe, and efficient manner. This is characterized by ‘There are no coal on the ground and no men in the coal mine’. First, this paper systematically explains deep in situ fluidized coal mining. Then, it presents a new theoretical concept, including the theories of mining-induced rock mechanics, three-field visualization, multi-physics coupling for in situ transformation, and in situ mining, transformation and transport. It also presents key technological concepts, including those of intelligent, unmanned, and fluidized mining. Finally, this paper presents a strategic roadmap for deep in situ fluidized coal mining. In summary, this paper develops new theoretical and technological systems for accomplishing groundbreaking innovations in mining technologies of coal resources in the deep underground.

Organic wastewater can be used to prepare coal water slurry (CWS) for the resource utilization of organic wastewater. The components in organic wastewater are highly complex, and some of their subs...

The hydrogen generation performance of the mixture of aluminum powder and sodium borohydride was investigated experimentally in steam atmosphere to reveal the promotion effects and mechanis...

Aluminum (Al) nanoparticles were coated with ammonium perchlorate (AP) to obtain AP-coated Al nanoparticles with different coating amounts. The coating layers were characterized by TEM and TG. Resu...

Boron suspension fuel is considered a good candidate to meet the energy requirements of hypersonic aircraft. As a solid-liquid mixed fuel, its combustion is a complex multi-stage process coupling of solid boron and liquid JP-10 combustion affected by various factors. In this study, A CO2 laser ignition test system was used to obtain the combustion characteristics of boron suspension fuel with solid loading of 10 wt.% in O2/Ar atmosphere. Focus is placed on the key factor of oxygen supply on the evolution of its solid-liquid coupling combustion characteristics. Theoretical analysis of the underlying mechanism of oxygen transportation and consumption caused by boron and JP-10 and their coupling characteristics was carried out for different stages. The results indicate that the combustion process could be divided into ignition, evaporation combustion, agglomerate combustion and extinguishment under full oxygen supply. In ignition stage, boron particles first ignite and promote the rapid ignition of JP-10. Oxygen supply can transfer boron combustion from heterogeneous reaction into homogeneous combustion. In evaporation combustion stage, a clear competition for oxygen between JP-10 and boron is observed. JP-10 is the main oxygen consumer whose flame forms an oxygen-lean zone around the droplet and suppresses boron combustion within the area. Micro-explosion could help carry boron particles into the outer oxygen-rich zone and achieve single-particle combustion. Increasing oxygen content to 60% can effectively compress the oxygen-lean zone area and realize simultaneous combustion of boron and JP-10. Agglomerate combustion stages could only occur when oxygen content is higher than 80%, which is the main energy releasing stage of boron. In extinguishment stage, black smoke is observed due to incomplete combustion of JP-10 when oxygen content is less than 60% while white smoke is observed due to boron oxide cooling deposition. This study provides a reference for the full energy exploitation of boron suspension fuel.

As one of the alternative clean fuels, aluminum is suitable for generating hydrogen and power via metal hydrolysis. The reaction process characteristics were studied in a cylindrical reacto...

Internal combustion steam cycle (ICSC) is a novel steam power cycle using hydrogen as an energy carrier to produce superheated steam. High humidity hydrogen produced during fast hydrogen production...

An ionic liquid (IL) [P66614][Triz] with a low regeneration temperature was loaded on a graphene nanoplatelet (GNP) and reduced graphene oxide (RGO) to accelerate the CO2 absorption rate. High-resolution transmission electron microscopy (HRTEM) patterns showed that GNP was composed of a regular “honeycomb” lattice, but a regular lattice structure was not observed for RGO as a result of the functional group on it. The CO2 absorption capacity (63.6 mg of CO2/g of IL) and absorption peak rate (22.4 mg of CO2 g–1 of IL min–1) of IL loaded on GNP were increased by 8.2 and 72.3%, respectively, compared to those of neat IL. The supported IL performed better because [P66614][Triz] was oriented in a favorable dispersion as a result of the negative ζ potential of the GNP surface. In contrast, the CO2 absorption rate of RGO–20% IL (mass ratio of RGO/IL = 4:1) was lower than that of IL, which could be attributed to the hydrogen bond between surface oxygen functional groups and IL. 13C nuclear magnetic resonance and M...

To upgrade Indonesian lignite by significantly reducing volatile matter content, char adsorbent was employed to accelerate lignite pyrolysis through microwave irradiation. Physicochemical properties of pyrolyzed lignite were determined with the assistance of char adsorbent on Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray spectroscopy, N 2 adsorption porosimetry, and contact angle analysis. Under the same microwave power of 800 W and irradiation time of 12.5 min, the lignite temperature remarkably increased from 150 °C to 656 °C with the aid of 10 g char adsorbent. Its apparent aromaticity increased from 0.50 to 0.97. The relative content of superficial carbon functional groups attributed to π–π ∗ transitions increased from 1.18% to 6.71%. The volatile matter content (dried basis) markedly decreased from 48.94% to 6.47% due to the release of volatile compounds in the lignite.

Mesoporous molecular sieves SBA-15 with four pore structures were loaded with an ionic liquid [P66614][Triz] to adsorb CO2 from raw biohythane. The hybrid sorbents of SBA-15 loaded with [P66614][Triz] were characterized by using N2 adsorption analyzer, thermogravimetric analyzer, scanning electron microscopy, and high-resolution transmission electron microscopy. The molecular sieve SBA-15 (with the most probable pore size of 4.3 nm) loaded with 50% ionic liquid (IL), which was called SBA-15 (4.3) − 50% IL, exhibited the fastest CO2 absorption rate and the shortest equilibrium time, which was approximately one-third of the equilibrium times of the other three hybrid sorbents. An intraparticle diffusion model was used to clarify that SBA-15 (4.3) − 50% IL (with the shortest pore length of 120 nm) executed a two-stage CO2 absorption process, which reduced the CO2 absorption time. The rate constant kI in the first stage of the CO2 absorption of SBA-15 (4.3) − 50% IL was approximately four times as much as those of the other three hybrid sorbents because the cross-section area of its total pores was approximately three times higher than those of the other three hybrid sorbents. Results showed that pore length had significant effect on CO2 absorption performance.

The co-slurrying technology of coal and organic wastewater, which achieves the simultaneous disposal and utilization of wastewater, has attracted extensive attention in recent years. The emission of coal gasification wastewater causes serious environmental hazards, because of its large amount, high organic content, and high toxicity. In the present study, two types of wastewater, namely, gasifier wastewater (GW) and wastewater from a secondary sedimentation tank (SW), were used to prepare coal water slurry (CWS), which was labeled as coal–GW–slurry (CGS) and coal–SW–slurry (CSS), respectively, with coal–deionized water–slurry (CDS) as a reference. The surface property of coal and the dispersing mechanism were characterized using zeta potential and contact angle analyses. Results showed that the fixed viscosity loading decreased with the addition of the two types of wastewater, and the decrease was more considerable with GW. All the slurries exhibited pseudo-plastic behavior and thixotropy, with the follow...

In order to reduce energy consumption of absorbent regeneration, an amine absorbent piperazine (PZ) was dissolved in an organic solvent N, N-dimethylformamide (DMF) to prepare a phase-changing PZ/DMF solution for CO2 absorption with solid precipitate of PZ-carbamate. The CO2 absorption capacity and peak rate of PZ/DMF solution were 22.9% and 29% higher than those of PZ/water solution, respectively. Based on differential scanning calorimetry/thermogravimetry experiments, biscarbamate PZ(CO2)22− and protonation PZ(H)22+ compositions (34.5 wt%) in the PZ-carbamate precipitate mainly decomposed at peak temperature of 91.9 °C due to their instability, and then PZ(CO2) composition (65.5 wt%) in the PZ-carbamate precipitate decomposed at peak temperature of 125.7 °C. The electrochemical corrosion tests and scanning electron microscopy revealed that PZ/DMF solution had much lower corrosivity than PZ/water solution.

© 2017 The Combustion Institute A multi-point Laser-Induced Breakdown Spectroscopy (LIBS) method for quantitative measurement of sodium concentrations in the gas phase, the surface temperature and the particle diameter during the combustion of a Zhundong coal particle is presented. To obtain multi-point LIBS data, the laser focusing and signal collection optics are mounted on a translational platform which is able to traverse cyclically. With this setup multi-point LIBS measurements above a burning particle can be performed and the time-resolved sodium release process can be obtained. The results show that 42.2% of the total sodium mass is released during the burning of the Zhundong coal sample. For a 4 mm particle, in the char burnout stage sodium is released most strongly, i.e., 87% of the total released sodium mass, while in the de-volatilization and ash reaction stages the percentages are 5% and 8%, respectively. The atomic sodium and NaOH are the most favored species at chemical equilibrium in the plume according to CHEMKIN. The sodium release is found to be closely related to the particle burning stages by analyzing the sodium release, particle surface temperature and its diameter. A linear relationship is found between the residual sodium mass in the particle and the volume of the particle. The volatile sodium release rate obeys a two-step Arrhenius expression. Predictions by the developed two-step kinetics model agree well with the measured sodium release profiles in all the three coal-burning stages.

Coal-assisted water electrolysis can reduce the electricity consumption of traditional water electrolysis by 40–60%, but the rate of hydrogen production in this process is very slow. Some coal gasification wastewater can promote the electrical oxidation of coal, the addition of which can achieve resource utilization of wastewater while producing hydrogen at low cost. In this study, the electrolysis characteristics and oxidation mechanism of gas washing water are studied using anode reaction kinetics, and its role in the process of coal electrolysis is studied. The results show that the main anodic reactions of gas washing water are, in order of increasing voltage, the oxidation of organic matter, bromide ions, and the water decomposition reaction, and that there is no obvious interaction between these three oxidation stages and Fe3+/Fe2+. On the one hand, gas washing water can promote the catalysis of iron ions and increase the effective iron concentration in the solution. On the other hand, it plays an important role in changing the surface state of coal particles and improving the electrochemical activity of coal, thereby increasing the reaction rate of coal electrolysis.

ABSTRCT: Variations in the grindability of semi-cokes produced by two low-rank coals at different pyrolysis temperatures were studied. The grindability of semi-cokes prepared by XiMeng lignite (XL) had minimal changes at varying pyrolysis temperature and was nearly similar to that of a dehydrated sample. The pore structure of XL was fully developed after dehydration and had no significant change during pyrolysis, as indicated by the observations obtained through scanning electron microscopy and results of the mercury intrusion porosimetry experiment. Thus, its grindability showed little change during pyrolysis. Meanwhile, the grindability of ShenHua sub-bituminous coal (SC) decreased considerably when pyrolysis temperature reached 550 °C. As shown by the results of thermal gravimetric (TG) experiments, X-ray diffraction (XRD) and fractal analysis of pore structure, the coal matrix of SC had a plastic stage. Meanwhile, its volatile matter rapidly releases in this stage. After the plastic stage, considerabl...

The energy release efficiency of boron (B)-containing fuel-rich solid propellants depends largely on the combustion behavior of the B particles contained therein. Here, the combustion process of B particles was first studied using a laser ignition testing system. Then, the combustion and agglomeration characteristics of B particles in a fuel-rich propellant were further investigated. To this end, a microtube burner was specially manufactured to mimic the secondary combustion of boron-containing propellant. Results show that the primary combustion intensity of the boron-containing propellant was relatively weak, and the combustion temperature was 1720±32 K. B particles would participate in the primary combustion reaction of the propellant, resulting in short time detection of the characteristic green flame and BO2 spectrum. Severe self-conglomeration of B particles occurred on the propellant burning surface, forming irregular coral-like B particle conglomerates. The development of the quasi-secondary (the word “quasi” is added to highlight the difference between the experimental conditions and the actual conditions in engines) combustion flame showed that hot B particles were an important ignition source for the gaseous fuel and that the existence of excess gaseous fuel in the primary plume was an important prerequisite for self-sustaining combustion of B particles in air. The emission spectra of propellant quasi-secondary combustion were very similar to those of primary combustion, but the intensity was significantly increased. Microstructures of the combustion residues showed that the oxide layer on the surface of B particles played an important role during the formation of B conglomerates. Irregular B conglomerates detached from the propellant burning surface might further develop into spherical B agglomerates in the high-temperature secondary combustion flame zone.

As the most abundant metal on the earth, aluminum is one of alternative clean fuels. This work presents experimental studies on the reaction process characteristics in a specially designed reactor ...

A phase-change solvent for CO2 absorption was prepared by mixing N-methyl-1,3-diaminopropane (MAPA) and N,N-dimethylformamide (DMF). In this MAPA/DMF solvent, MAPA-carbamate precipitate was formed after CO2 absorption to facilitate reducing energy consumption of amine regeneration. The CO2 uptake of MAPA/DMF solvent (14.8 mg/g solvent) was increased by 22% compared with that of MAPA/water solvent (12.1 mg/g solvent). For MAPA/DMF solvent, time was reduced by 22% to reach the CO2 absorption equilibrium. The maximum CO2 uptake rate of MAPA/DMF solvent was 30% higher than that of MAPA/water solvent because DMF displayed higher CO2 solubility and lower MAPA-carbamate solubility than water. Differential scanning calorimetry and thermogravimetry experiments revealed that MAPA(H+)2 and MAPA(CO2–)2 compositions in MAPA-carbamate precipitate first decomposed (peak temperature = 59.9 °C). Subsequently, the MAPACO2 compositions in precipitate also decomposed (peak temperature = 124.2 °C).

Co-combustion of dried waste activated sludge (WAS) and lignite was conducted in a horizontal tube furnace system. The mineral transformation and emission behaviors of Cd, Cr, Ni, Pb, and Zn during combustion were examined. The above heavy metals (HMs) were selected because they are more abundant in WAS than in lignite. In the combustion condition of 1000 °C–21% O2–30 min, the minerals in lignite ash were mainly anorthite (CaAl2Si2O8), quartz (SiO2), pyroxene [Ca(Mg,Fe)Si2O6], and albite (NaAlSi3O8). By contrast, the minerals in WAS ash were mainly quartz (SiO2), anorthite (CaAl2Si2O8), and hematite (Fe2O3). When 90% lignite and 10% WAS were co-combusted, hematite was hardly detected in the combustion product because hematite reacted with quartz and calcium oxide, which are abundant in lignite ash, and generated a large amount of pyroxene. Anorthite and pyroxene were generated continuously during the combustion process, but albite was mainly generated during the first 5 min of combustion. High temperature promoted the generation of complex components, such as sodian anorthite [(Ca, Na)(Si, Al)2Si2O8 or (Ca, Na)(Si, Al)4O8]. High O2 concentration promoted the reaction among the three main mineral elements, i.e., silicon, aluminum, and calcium, and generated a large amount of anorthite. During the co-combustion of WAS and lignite, the volatilization percentages of Cd, Pb, and Zn exceeded 30% after a combustion time of 30 min, and the order was Cd > Pb > Zn. By contrast, the volatilization percentages of Cr and Ni were lower than 15%. High temperature caused an increase in the volatility of HMs, especially Zn and Ni, although the volatilization percentage of Ni remained low. High O2 concentration also caused an increase in the volatility of HMs, except for Cr and Ni, which showed a slight increase or decrease with increasing O2 concentration in the inlet atmosphere.

In this study Yimin lignite coal from Inner Mongolia was taken for investigating the influence of hydrothermal dewatering (HTD) on trace elements (Hg, As, Se) under different conditions. First, the coal samples were treated through HTD process at a temperature range of 200–300 °C, then proximate analysis was performed to check changes in the coal. Meanwhile, inductively coupled plasma-mass spectrometry and atomic fluorescence spectrometry were used to detect the concentrations of trace elements. Furthermore, minerals in samples were analyzed by powder X-ray diffraction (XRD). Sequential chemical extraction procedure (SCEP) was also performed to determine the occurrence modes of trace elements. The results showed that HTD treatment is effective in removing moisture and upgrading coal rank, and the operating temperature should be in good control at a certain range due to the loss of volatile mass. Minerals in this type of coal mainly include quartz and kaolinite, and HTD may have an effect on removing minor minerals muscovite and siderite. HTD can remove all three elements mentioned above. The highest removal rate detected is about 15% for As, 45% for Hg and 43% for Se. The experimental result shows that occurrence mode of Hg and As exist mainly in pyritic fraction while Se mainly in pyritic fraction and organic fraction. During HTD, all fractions of Hg and Se decrease obviously. However, for As, the decreasing amount in carbonate and pyritic fractions is much smaller than that in organic and silica bond fractions. It can be inferred that pyrite in coal may not decompose but only lose the bonds with trace elements. Pyrolysis behavior of coal and the strong solubility of sub-critical water should be responsible for the removal of trace elements.

The addition of lithium to Al–H2O reaction is proven an effective means to produce hydrogen. This study conducted experiments on a specially designed test system. Results of the experiment indicated that Al–Li alloy had a high reactive activity in water vapor. The reaction of Al–Li alloy with water vapor at the range of 300°C to 700°C can produce H2 of 980–1120.8 ml/g. A thermal infrared imager in the specially designed reactor recorded the surface temperature change in the reaction process. Temperature analysis can guide the utilization of the heat released in Al–H2O reaction.

Boron (B) has potential applications in energetic materials as additive fuel. In order to understand the combustion mechanism of B with various scales, the ignition and combustion characteristics of micro- and nano-sized B under different pressures (0.4 MPa, 0.8 MPa and 1.2 MPa) and atmospheres (60% O2 + 40% N2, 80% O2 + 20% N2 and 100% O2) were studied by a laser ignition and combustion experimental system. The evolution images and specialized parameters of ignition and combustion under different conditions were obtained, and the effects of atmosphere and pressure on the ignition and combustion characteristics of micro- and nano-sized B were discussed. Meanwhile, the crystal structure and morphology of condensed combustion products were observed by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM), and then the compositions in micro-areas were analyzed by energy dispersive X-ray spectroscopy (EDX). The results show that, the burning of micro-sized B is relatively slow, while the burning of nano-sized B is intensified, and a deflagration-like phenomenon is observed for nano-sized B in pure oxygen with pressures of 0.8 and 1.2 MPa. The ignition delay time, combustion time and maximum flame temperature of nano-sized B are smaller than those of micro-sized B, while the maximum characteristic spectral intensity of nano-sized B is stronger. Besides, B2O3, B6O and BN exist in condensed combustion products of micro-sized B, but only B2O3 is detected for nano-sized B, and products agglomerating is observed for nano-sized B. In general, nano-sized B has significant advantages than micro-sized B in the ignition and combustion characteristics, especially under conditions of high oxygen concentrations and high pressures.

Biomass combustion is a promising method in combustion facilities to reduce CO2 emissions. Biomass fuel has unfavorable characteristics, such as low temperature ash minerals and high particulate matter (PM) emission in the combustion facility, which influences operation and creates environmental issues. In this work, different types of empty fruit bunch (EFB) and palm kernel shell (PKS) biomass samples, such as raw biomass, demineralized biomass, and its biomass pretreated by torrefaction were studied to identify their char combustion characteristics by thermogravimetric analysis (TGA) and their ash deposition behaviors and PM emissions in a drop tube furnace (DTF) experiment. Regarding the char combustion characteristic results obtained by TGA, demineralization pretreatment did not clearly influence the char combustion reactivity compared to that of raw biomass, but torrefaction pretreatment lowered the char combustion reactivity at low temperatures. In the DTF experiments, torrefaction pretreatment led to increasing ash deposition and PM emissions during biomass combustion. However, demineralization pretreatment clearly lowered the amount of ash deposition and PM emissions because potassium (K), chlorine (Cl), and sulfur (S) were significantly removed by demineralization pretreatment. In particular, scanning electron microscopy with dispersive X-ray spectroscopy (SEM-EDX) analysis results showed that the demineralized biomass samples having low K, Cl, and S components emitted relatively large PM compared to untreated biomass. Therefore, demineralization pretreatment might be a good method to produce cleaner biomass fuel.

High-concentration organic waste liquids have complex components and their treatment is difficult. These liquids also contain hydrophobic organic pollutants. The preparation of waste liquid coal water slurry (WCWS) can aid with environmental protection and resource utilization. In this study, xanthan gum was selected from 11 types of additives because it overcomes the problem of solution incompatibility during the mixing of various high-concentration organic waste liquids. The experimental results showed that with 0.08 wt% addition of xanthan gum, no stratification occurred in the mixed waste liquid and the apparent viscosity of the WCWS was 921.1 mPa ∙ s. In this study, the role of xanthan gum was studied, and the effect of its addition on the coal particle surface was characterized by zeta potential and contact angle measurement. In addition, various interaction energies in the WCWS system were calculated using the extended DLVO theory. The results showed that xanthan gum introduced steric hindrance interaction energy into the WCWS system, enabling the system to be stably dispersed.

Zhundong coal represents a large portion of China’s future energy supply, because of the large reserve capacity. Although Zhungdong coal has low ash and good ignition characteristics, it also contains large amounts of sodium, which can foul and corrode heat-transfer surfaces. For economically viable use of Zhundong coal or other high-alkali coals, the alkali release must be mitigated prior to or within the burner. This can be done either by washing the coal, using sorbents to trap the sodium, or a combination of these methods. Additive influence on the release of sodium over the entire coal combustion process was measured using a calibrated laser-induced breakdown spectroscopy (LIBS) technique. The additives used were alumina, silica, and five mineral sorbents comprising blends of silica, alumina, and various other inorganic compounds; different coal/sorbent ratios were assessed (1%, 3%, and 5% additive, by weight). During the three stages of sample coal combustion, it was found that the first stage, devo...

With high calorific value and the environmental friendly features, hydrogen has been attached much importance. Aluminum–water reactions at medium–high temperature perform well in hydrogen generation as well as heat utilization. Active researches of the aluminum–water reactions in recent years can be attributed to the increasing interest of hydrogen generation and energy conversion. In the basis of aluminum–water reactions, the concept of a novel electricity and heat co-generation system was proposed here and it was primarily composed of a reactor, one or two turbines and generators, heat exchanger for heat user, a fuel cell and a pump. Two layouts were designed and analyzed: the one turbine layout (OTL) and the two turbine layout (TTL). The effects of key parameters, such as the steam temperature and pressure at turbine inlet, the heat user temperature and fuel cell conversion efficiency were investigated. The co-generation system could generate heat and electricity of about 22.2 MJ/kg (Al) in the OTL design. The system utilization efficiency, the ratio of the output was approximate 70% and the electricity generation efficiency could reach up to 41.52% (OTL) and 49.25% (TTL) in the two cases respectively. The OTL presented a higher heat user utilization efficiency than TTL, because of the higher turbine outlet parameters. The TTL layout with the integration of fuel cell and heat user enhanced electricity output by 45.06% in comparison with the OTL layout. The steam temperature at turbine inlet showed considerable impacts on the system utilization efficiency at the TTL case. Enhancing fuel cell conversion efficiency benefited the system and fuel cell utilization efficiencies, especially at the TTL case.

Sulfur-iodine thermochemical cycle is considered as a promising route for hydrogen production without CO2 emission. In this cycle, the hydrogen iodide conversion rate plays an important role in the total thermal efficiency to some extent. To improve the efficiency of HI decomposition, the homemade carbon membranes supported by α-alumina porous tubes were well-designed in a specific way and evaluated aiming at removing H2 from HI decomposition reaction side. Permeability, selectivity and stability of self-designed carbon membranes are investigated in some gaseous components in the present work. Firstly, single-component (H2/Ar) permeance was observed with differential pressure ranging from 0.05 to 0.2 Mpa. The result shows that differential pressure has little effect on H2 and Ar permeance. Secondly, the hydrogen and argon permeance through carbon membrane is 3.1 × 10−8 mol m−2 s−1 Pa−1 and 5.7 × 10−10 mol m−2 s−1 Pa−1 respectively at 300 °C. The separation factor of H2 and Ar is 54, which is greater than the theoretical value calculated by Knudsen diffusion equation. Thirdly, hydrogen permeability in the H2 HI H2O gaseous mixture system owns nearly the same as that of the single-component (H2) at 300–500 °C. Due to the large molecule diameter, most of HI are stopped by carbon membrane. However, H2O molecules could pass through the carbon membrane obviously. The permselectivity of H2/HI is over 310 at 500 °C. Last, after 10 h of stability tests, some slight damage are observed on the surface of carbon membrane according to the scanning electron micrograph (SEM). The structure change of carbon membrane gave rise to a little increase of H2 permeance at 20–100 °C.

To explore the feasibility of co-combustion of lignite and wasted activated sludge (WAS) and examine their synergistic effects, combustion of lignite–WAS blend at a mass ratio of 90:10 in a horizontal tube furnace was conducted. Results showed that the synergistic effects occurred between lignite and WAS during their co-combustion because the actual conversion ratio of combustible substances (CR) was higher than the theoretical prediction. Effects of furnace temperature and O 2 concentration of inlet atmosphere on CR were also determined. High furnace temperature and O 2 concentration of the inlet atmosphere resulted in high CR. In the early combustion stage, the furnace temperature played a major role. In the middle stage, the furnace temperature and O 2 concentration of the inlet atmosphere exhibited a combined effect. In the late state, the O 2 concentration of the combustion atmosphere played a key role. Scanning electron microscopy (SEM) photos indicated that the micro appearance of solid particles and their changing trends during the combustion of lignite–WAS blend were similar to those of lignite because of the high proportion of lignite (90%) in the blend. However, when compared to the case of lignite, the solid particles of the lignite–WAS blend were smaller, rougher, and looser in structure as the combustion progressed. In the solid combustion products of blend, carbon (C), oxygen (O), and chlorine (Cl) contents exhibited different evolution behaviors. The C content first increased and decreased, the O content first decreased and increased, and the Cl content continuously decreased to zero.

Primary combustion products of boron-based propellants are incomplete combustion products that are emitted from the gas generator of a solid ducted rocket. Studying the composition of primary combustion products provides valuable information about the primary combustion process and also helps to better understand the secondary combustion process. The particle size of the primary combustion products is analyzed by a laser particle size analyzer. The qualitative analysis of the sample composition is performed by using x-ray diffraction, x-ray photoelectron spectroscopy, and thermogravimetry–differential scanning calorimetry experiments. Based on these results, an integrated quantitative analysis of the sample composition is conducted. The quantitative analysis methods include tube furnace heating, ion chromatography, infrared spectroscopy, and inductively coupled plasma chromatography. In addition, scanning electron microscopy and energy dispersive spectrometry are also used to analyze the micro-morphology and distribution of different components in the sample. The primary combustion products mainly contain B, C, B m C n , H3BO3, B2O3, BN, Mg, MgCl2, and NH4Cl. B m C n (22–24%), H3BO3 (20%), and B (16.8%) are the three major components, while B m C n , B, and C (9.8–11.8%) are the three combustible components present in the highest amounts. The oxidant NH4ClO4 is completely consumed during the primary combustion, while the metal additive Mg does not show much reactivity. The micro-morphology and distribution of B m C n , H3BO3 (or B2O3), B, Mg, and C in the sample are investigated. Some components in the primary combustion products are found to be agglomerated, while some components are dispersed. Large particles in the sample mainly include B and Mg, while B m C n , H3BO3 (or B2O3), and C particles are small. In general, the combustion completeness of the primary combustion products is rather low. Therefore, better understanding and controlling of the secondary combustion process is very important to improve the performance of B-based propellants.