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To investigate the flow characteristics of sieve tray columns with circular downcomers, the Euler–Euler gas–liquid two‐phase flow model is used to simulate a three‐dimensional sieve tray column. Each phase is regarded as an interpenetrating continuum with independent transport equations. The velocity distribution, clear liquid height, and foam layer height are predicted by the model. The correlation is established for predicting the clear liquid height on the sieve tray. The results show the following: (1) The sensitivity of the clear liquid height to the gas phase load is greater than that of the liquid phase load. (2) When the gas–liquid distribution is stable, the flow on the round sieve tray column presents a piston flow pattern. (3) The average liquid holdup of the circular downcomer of the three heights all showed a slow decrease at first, and then an inflection point appeared near the height of 0.02 m, after which the liquid holdup dropped sharply. (4) The established correlation has good predictive performance for calculating the clear liquid height in the column, and the relative error between the calculated value and the actual value is less than 10%. [ABSTRACT FROM AUTHOR]

This article provides a comprehensive exploration of the imperative necessity for coupling the utilization of low-rank coal, sewage sludge, and straw. It studies the challenges and limitations of individual utilization methods, addressing the unique hurdles associated with feedstocks. It focused on achieving integrated and sustainable resource management, emphasizing efficient resource utilization, waste minimization, and environmental impact reduction. The investigation extends to the intricate details of reaction processes in co-processing, with a specific emphasis on the drying of raw materials to enhance combustion characteristics. The molding and preparation of feedstock are dissected, encompassing raw material selection, mixing, and the crucial addition of additives and binders. The proportions and homogenization of these feedstocks are intricately examined for uniformity and effectiveness. Furthermore, it presents theoretical approaches for investigating the co-combustion of these diverse feedstocks, contributing a solid foundation for future studies in this dynamic field. The findings presented in it offer valuable insights for researchers, practitioners, and policymakers seeking sustainable solutions in the co-disposal technology of these feedstocks. Therefore, it provides a holistic understanding of the challenges and opportunities in coupling the utilization of these selected feedstocks. By addressing individual limitations and emphasizing integrated resource management, the article establishes the groundwork for sustainable and efficient co-processing practices. The exploration of reaction processes gives a comprehensive framework for future research and application in the field of co-combustion technology. The insights gleaned from this study contribute significantly to advancing knowledge in the sustainable utilization of diverse feedstocks, guiding efforts towards environmentally responsible and resource-efficient practices. [ABSTRACT FROM AUTHOR]

This study investigates the potential of using sewage sludge and low-rank coal for the sustainable production of sulfuric acid, which can then be used for the hydrolysis of straw through ASPEN PLUS simulation. Pyrolysis and gasification processes were used to convert sewage sludge and low-rank coal into syngas, which were then purified and oxidized to produce H2SO4 and NH3 gas. The pyro-gasification enhanced syngas yield. The effects of key process parameters such as temperature, steam-to-biomass ratio, equivalence ratio, and feedstock composition on the yield and composition of syngas and H2SO4 coupled with minor parameters like pressure were investigated. The simulation was conducted over the temperature and pressure range of 400 – 900°°C and 70 – 150 kPa respectively. While the steam-to-biomass ratio and equivalence ratio were respectively varied from 0.66 – 1.65 and 0.14 – 0.35. Part of the 1012.88 kg/h of H2SO4 produced was used to hydrolyze straw, producing glucose as a valuable feedstock for biorefineries. About 3989.10 kg/h of NH3 was produced. Results showed that the use of sewage sludge and low-rank coal as feedstocks for syngas production can be a sustainable and cost-effective alternative to traditional fossil fuels. The resulting H2SO4 can also be used for various other applications, such as in the production of fertilizers and detergents. Overall, this study agrees with the literature, demonstrates the potential of integrating biomass and waste resources for the sustainable production of high-value chemicals and fuels, and contributes to the field of sustainable chemical and energy production while addressing environmental and economic considerations. [ABSTRACT FROM AUTHOR]

Presently, selective catalytic reduction (SCR), with either carbon monoxide, urea, hydrocarbons, hydrogen, or ammonia as a reductant, has become a nitrogen oxide (NOx) removal technology (NOx conversion) of many catalytic companies and diesel engine exhaust gas. Although, there exists a serious threat of low-temperature limitations. So far, certain scientists have shown that barium-based (Ba-based) catalysts have the potential to be highly effective at SCR of NOx at low temperatures when ammonia is used as the reducing agent. The process of NOx storage and reduction which alternate SCR is known as the Lean NOx trap. Herein, we give the condensed advancements and production of the catalysts that involve BaO in low-temperature NH3-SCR of NOx, the advantages of BaO catalysts compared to the recently hot electrocatalysis, the stability of BaO catalyst materials, and the condensed advancements and production of the catalysts that involve BaO in low-temperature NH3-SCR of NOx. These catalysts are viewed in the light of their preparation method, particulate, and posture in mixed oxides. Also, the characteristic features of Ba-based catalysts are carefully considered and briefed under the following areas: preparation method and precursor, crystallinity, calcination temperature, morphology, acid sites, the specific surface area for reaction, redox property, and activation energy of catalysts. More to these are the discussions on Eley–Rideal [E-R] and Langmuir–Hinshelwood [L–H] mechanisms, the H2O/SO2 and O2 permissiveness, and the NH3-SCR reaction mechanism over Ba-based catalysts highlighting their possible effects. Finally, we proposed the prospect and the likely future research plan for the low-temperature NH3-SCR of NOx. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction (SCR) is now an established NOx removal technology for industrial flue gas as well as for diesel engine exhaust gas. However, it is still a big challenge to develop a novel low-temperature catalyst for NH3-SCR of NOx, especially at a temperature below 200°C. In the past few years, many studies have demonstrated the potential of iron (Fe)-based catalysts as low-temperature catalysts for NH3-SCR of NOx. Herein, we summarize the recent progress and performance of Fe-based catalysts for low-temperature NH3-SCR of NOx. Catalysts are divided into three categories: single FexOy, Fe-based multimetal oxide, and Fe-based multimetal oxide with support catalysts. The catalytic activity and selectivity of Fe-based catalysts are systematically analyzed and summarized in light of some key factors such as activation energy, specific surface area, morphology, crystallinity, preparation method and precursor, acid sites, calcination temperature, other metal dopant/substitute, and redox property of catalysts. In addition, H2O/SO2 tolerance and the NH3-SCR reaction mechanism over Fe-based catalysts, including Eley-Rideal and Langmuir-Hinshelwood mechanism, are emphasized. Lastly, the perspectives and future research directions of low-temperature NH3-SCR of NOx are also proposed. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction (SCR) is now an established NOx removal technology for industrial flue gas as well as for diesel engine exhaust gas. However, it is still a big challenge to develop a novel low-temperature catalyst for NH3-SCR of NOx, especially at a temperature below 200°C. In the past few years, many studies have demonstrated the potential of iron (Fe)-based catalysts as low-temperature catalysts for NH3-SCR of NOx. Herein, we summarize the recent progress and performance of Fe-based catalysts for low-temperature NH3-SCR of NOx. Catalysts are divided into three categories: single FexOy, Fe-based multimetal oxide, and Fe-based multimetal oxide with support catalysts. The catalytic activity and selectivity of Fe-based catalysts are systematically analyzed and summarized in light of some key factors such as activation energy, specific surface area, morphology, crystallinity, preparation method and precursor, acid sites, calcination temperature, other metal dopant/substitute, and redox property of catalysts. In addition, H2O/SO2 tolerance and the NH3-SCR reaction mechanism over Fe-based catalysts, including Eley-Rideal and Langmuir-Hinshelwood mechanism, are emphasized. Lastly, the perspectives and future research directions of low-temperature NH3-SCR of NOx are also proposed. [ABSTRACT FROM AUTHOR]

To rationally utilize biomass as an auxiliary fuel for pulverized coal injection (PCI) technology, the process of co-injection of bio-syngas/coal into the blast furnace (BF) is designed. In this paper, a 3D CFD model with double lance is established to investigate the co-injection of bio-syngas/coal in the BF. The effects of bio-syngas injection rates and the location of double-lance on the in-furnace thermochemical behavior of pulverized coal (PC) are systematically analyzed. The results show that the combustion of the bio-syngas promotes the devolatilization of the PC, but hinders the volatile matter (VM) combustion. As the bio-syngas injection rate increases, the volume-average temperature of the raceway and the endpoint burnout of PC increases; In addition, a reduction in the distance between the bio-syngas lance and the tuyere, or an increase in the distance between the two lances, can facilitate the PC to obtain more oxygen and have a better endpoint burnout. However, the rise of the coal plume reduces the space for the particles to recirculate, resulting in a reduction in the overall burnout of the PC. • A 3D CFD model of bio-syngas/coal co-injection in a blast furnace is developed. • The interaction between bio-syngas and coal is discussed. • The combustion of the bio-syngas promotes the devolatilization of the coal, but hinders the volatiles combustion. • The increased distance between the two lances can facilitate the endpoint burnout of coal. [ABSTRACT FROM AUTHOR]

ABSTRACT The time evolution of the methane reburn process at high temperature was investigated by the simulation method. The simulated results show that the time evolutions of each component are different with the stoichiometric ratio (SR) of the reburn zone and the reaction time. In the simulation conditions, CH4, C2H2, and H appear as SR is from 0.66 to 0.96; CH3 appears as SR is from 0.66 to 0.76; HCN, NH3, and HNCO appear as SR is from 0.66 to 0.86; OH appears as SR is from 0.82 to 0.96. In the case with SR of 0.76, C2H2 and CH3 only appear in the initial 0.2 s, NH3 and HNCO appear in the whole 2.0 s; In the case with SR of 0.82, C2H2 also appears in the initial 0.2 s, NH3 and HNCO only appear in initial 0.5 s, CH3 does not appear in the whole reaction time of 2.0 s. The reaction between CH3 and NO mainly occurs in the strong reducing atmosphere, and contributes significantly to remove NO to HCN, NH3, and HNCO. The interactions of NO with H and OH radicals mainly occur in the weak reducing atmosphere, and contribute to remove a small part of NO to N2. Through comparing the time evolutions of total fixed nitrogen (TFN) with different SR, it is suggested that the optimum SR for reducing TFN in the methane reburn process is about 0.82. © 2011 Curtin University of Technology and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The practice of injecting a coal/biomass blend can alleviate the pressure on carbon emissions and energy of ironmaking blast furnaces (BFs). In this paper, corn stalks treated by hydrothermal carbonization (HTC) are used as raw materials to eliminate the harm of alkali metals in the ash. The overall performance of individual behavior of the hydrochar, coal, and their blends are analyzed over the raceway with special reference to gas flow, temperature, species, and combustion efficiency. The results show that the hydrochar with higher volatile content is faster to devolatilize, showing a higher CO 2 content at the nozzle tip, and reaching a higher burnout in the raceway. The addition of hydrochar to coal can improve the overall flow and combustion performance of the blends. The simulated value is higher than the calculated value, indicating the synergistic effect has existed. When the proportion of the hydrochar is 75% in blends, the synergistic effect is most obvious. The model provides an effective tool for the design of coal/biomass blends. • The co-combustion process of hydrochar and coal in BF is simulated. • The burnout of hydrochar is higher than that of coal. • The synergistic effect of hydrochar/coal blending is examined in co-combustion process. • The simulated burnout is 2.1% higher than the calculated burnout in 25%coal/75%hydrochar case. [ABSTRACT FROM AUTHOR]

It is well-known that there is an interaction between biomass and coal in co-gasification process. In this paper, gasification of semi-coke (SC) and soybean straw char (SS) and their blends were carried out using non-isothermal thermogravimetric method. Interaction between SS and SC during co-gasification was investigated and synergy factors were calculated at different conversion stage. In order to explore whether the physical and chemical structure features have an effect on interaction, surface area analyzer, XRF and Raman spectrometer were adopted to determine the porous properties, ordering degree and ash composition for blends. The results show that the changes of porous properties and ordering degree for blends follow a linear law. The correlation expressions linking char characteristics to char reactivities indicate that the degree of graphitization is the main reason influencing the gasification reactivity. The interaction exhibits a negative synergetic effect at low conversion stage and a positive synergetic effect at high conversion stage. In addition, there are significant synergistic effects in the co-gasification of 75%SC/25%SS. Similar conclusions about synergetic effect are also observed from the kinetics data calculated by three kinetic models. • The biochar reactivities significantly greater than that of semi-coke. • The reactivities of biochar and semi-coke correlate well with their properties. • The increasing proportion of biochar weakens synergies during co-gasification. • Synergies on gasification of char vary with biochar/semi-coke mass ratio. • SF < 1 at low conversion stage and SF ＞1 at high conversion stage for co-gasification. [ABSTRACT FROM AUTHOR]

Maghemite (γ-Fe2O3) catalysts were prepared by two different methods, and their activities and selectivities for selective catalytic reduction of NO with NH3 were investigated. The methods of X-ray powder diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR), ammonia temperature-programmed desorption (NH3-TPD), transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDS), and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) were used to characterize the catalysts. The resulted demonstrated that the γ-Fe2O3 nanoparticles prepared by the facile method (γ-Fe2O3–FM) not only exhibited better NH3-SCR activity and selectivity than the catalyst prepared by the coprecipitation method but also showed improved SO2 tolerance. This superior NH3-SCR performance was credited to the existence of the larger surface area, better pore structure, a high concentration of lattice oxygen and surface-adsorbed oxygen, good reducibility, a lot of acid sites, lower activation energy, adsorption of the reactants, and the existence of unstable nitrates on the surface of the γ-Fe2O3–FM. [ABSTRACT FROM AUTHOR]

The selective catalytic reduction of NO with NH3 at low temperatures has been investigated with natural iron ore catalysts. Four iron ore raw materials from different locations were taken and processed to be used as catalysts. The methods of X-ray diffraction (XRD), X-ray fluorescence (XRF), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR), ammonia temperature-programmed desorption (NH3-TPD), scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) were used to characterize the materials. The results showed that the sample A (comprised mainly of α-Fe2O3 and γ-Fe2O3), calcined at 250 °C, achieved excellent selective catalytic reduction (SCR) activity (above 80% at 170–350 °C) and N2 selectivity (above 90% up to 250 °C) at low temperatures. Suitable calcination temperature, large surface area, high concentration of surface-adsorbed oxygen, good reducibility, lots of acid sites and adsorption of the reactants were responsible for the excellent SCR performance of the iron ore. However, the addition of H2O and SO2 in the feed gas showed some adverse effects on the SCR activity. The FT-IR analysis indicated the formation of sulfate salts on the surface of the catalyst during the SCR reaction in the presence of SO2, which could cause pore plugging and result in the suppression of the catalytic activity. [ABSTRACT FROM AUTHOR]