Asia-Pacific Journal of Chemical Engineering最新文献

The ammonia/coal co-combustion technology aligns with China's national energy condition, which is crucial for China to achieve carbon emission reduction in power plants and meet the “carbon peaking and carbon neutrality goals.” However, due to the distinct combustion characteristics of ammonia compared to traditional fossil fuels, blending ammonia into coal-fired power plants could lead to combustion instability and increase NO_x generation. In the present study, the combustion and NO_x emission characteristics of ammonia/coal co-firing in a 300-MW tangentially fired boiler were numerically investigated with elucidation on the impacts of NH₃ blending ratio, air distribution strategy, boiler load, load adjustment method and location of ammonia injection. The results indicate that ammonia injection can adversely affect coal burnout. When NH₃ blending ratio is 60%, the coal burnout rate decreases by about three percentage points compared with NH₃ blending ratio at 10%. Too high (more than 30%) or too low (less than 20%) NH₃ blending ratio could raise boiler NO_x emissions. The air distribution strategy is of great significance in reducing NO_x emissions. When α₁ rises from 0.95 to 1.0, the NO_x emissions increase by 223.2 mg·m⁻³ (6% O₂). The coal burnout rate and NO_x emissions can better meet energy conservation and emission reduction engineering requirements under the condition that the ammonia blending ratio is 20% and α₁ is 0.95. As the boiler load decreases, ammonia/coal co-combustion could efficiently decrease boiler NO_x emissions and increase the coal burnout rate, which is different from individual combustion of coal. The coal burnout rate increases by 2.2 percentage points with the boiler load reduced from 100% to 70%. In addition, compared with each burner evenly injected with ammonia, concentrated injection of ammonia can exert a significant rise in NO_x emissions, with a maximum increase of 449 mg·m⁻³ (6% O₂). The study can offer a certain reference for the low-carbon transformation of power plants in China.

In order to clarify the thermal reaction mechanism between iron/calcium (Fe₂O₃/CaO)-based oxygen carriers and coal char, the gas escape from the reaction process was resolved by TG-MS coupling, and the equivalent characteristic spectrum analysis (ECSA) method was used to determine the specific reactions occurring. Under Ar atmosphere, Fe₂O₃ starts to be reduced by graphite at 560°C, producing CO₂, and at 1040°C, CO is produced from the reaction between graphite and CO₂. When CaO is added to Fe₂O₃, CaO absorbs the CO₂ produced, affecting the path of the reaction. The reaction to produce CO₂ also occurs first in the two iron/calcium-based oxygen carrier conditions of sintered and pelletized ore, and CO production also occurs at high temperatures. In the case of air atmosphere combustion, only O₂ is consumed, and CO₂ is produced, no CO is formed. Graphite combustion consumes oxygen at a maximum value of 0.0393 mmol/min, and the addition of sintered ore reduces the maximum value of oxygen consumption to 0.0294 mmol/min, a decrease of about 25%, reflecting the oxygen buffering effect of oxygen carriers. Because the reaction of the coal char condition was concentrated at 300°C–700°C, this temperature interval, the addition of pelletized ore to coal char reduced the area of O₂ consumption from 3.36 to 3.01, indicating that the oxygen carrier provided additional oxygen in the reaction and reduced the oxygen consumption. The addition of iron/calcium oxygen carriers also reduces the reaction activation energy and makes the thermal reaction easier.

This study focuses on optimizing the performance of the Kosti Thermal Power Plant in Sudan using pinch analysis. Pinch technology offers a systematic approach to improving energy efficiency by analyzing heat transfer and energy flows based on the first and second laws of thermodynamics. The Kosti Thermal Power Plant, a 4 × 125-MW crude oil–fired station, was selected for benchmarking to evaluate its energy consumption and potential for optimization. The study identified that the plant operates at a thermal efficiency of 38%, and several heat streams within the system were examined for their contribution to overall energy use. Using pinch technology, the minimum hot utility required was determined to be 53 050.3 kW, and the minimum cold utility required was 185.7 kW. Through the application of pinch analysis, energy savings opportunities were identified, such as optimizing heat recovery and reducing the energy demand for external heating and cooling utilities. The study's findings emphasize the importance of stream matching, pinch point identification, and energy recovery in enhancing thermal power plant efficiency.

Aromatics and hydrogenated aromatics constitute the primary constituents of the recycled solvent utilized in coal liquefaction. However, the presence of hydrogenated aromatics complicates the assessment of the effects of aromatic compounds during the coal liquefaction process. To eliminate the effect of hydrogenated aromatics, solvent-free experiments and experiments with specific polycyclic aromatic compounds (pyrene, fluoranthene, phenanthrene, and naphthalene) were conducted, along with utilizing density functional theory calculations. Results show that the shuttle role of naphthalene is influenced by catalyst activity. In the presence of a low-active catalyst, naphthalene acts as a shuttle agent facilitating indirect hydrogen transfer. However, with a high-active catalyst, direct transfer of hydrogen from H₂ to pyrolysis radicals occurs without involving naphthalene as an intermediary. Polycyclic aromatic compounds exhibit higher hydrogen shuttle ability (pyrene > fluoranthene > phenanthrene > naphthalene). The high hydrogen shuttle ability can be attributed to the higher reactivity in hydrogenation and lower energy barriers for hydrogen transfer. A nonradical hydrogen transfer pathway has been proposed, promoting cleavage of strong covalent bonds and enhancing the yield of asphaltene and preasphaltene. Additionally, π–π inter actions between polycyclic aromatic compounds and pyrolysis radicals have been evaluated. The interactions contribute positively to radical stability. Substances characterized by a greater number of aromatic rings display a more pronounced stabilizing effect on free radicals.

The behavior of organic inhibitors, particularly heterocyclic compounds, is significantly impacted by the replacement. Our aim is to determine the most important effects of (-PhCl) and (-PhCH₃) on the deportment of (PP-PhCl) and (PP-PhCH₃) during the corrosion process abstraction of C-steel surface protection. The findings highlight the excellent performance of both inhibitors, with the highest values for PP-PhCl and PP-PhCH₃ reaching 95.1% and 92.3%, respectively, at the model concentration of 10⁻³ M. A mixed-type inhibitory behavior is demonstrated by the PP-PhCl and PP-PhCH₃ polarization curves from PDP. In the instance of PP-PhCl, an energy effect mechanism with a beneficial anodic reaction blocking procedure is used. However, a geometric blocking mechanism is exerted by the PP-PhCH₃. Due to the (-PhCH₃) effect, the higher concentration showed a greater impact on the inhibitory effectiveness of PP-PhCH₃ than PP-PhCl. After overcoming the temperature effect, the pyran–pyrazole inhibitors continue to protect the C-steel surface, despite a slight drop in inhibition efficiency as the temperature rises. This is explained by the fact that, particularly at low concentrations, the main cathodic region reactions are controlled rather than both reactions. According to the EIS study, the pyran–pyrazole inhibitors use the adsorption process to create a protective layer on the C-steel surface by increasing concentration, which causes a drop in Cdl and a rise in Rp. The PP-PhCl and PP-PhCH₃ interact by physisorption predominance, as determined by the activation parameters and the Langmuir adsorption isotherm. This describes how sensitive the protective layer is to changes in temperature. The MEB surface characterization results approved the PP-PhCl and PP-PhCH₃ layers that were created. EDX analysis confirms their composition. Additionally, the theoretical calculation shows that PP-PhCl is mostly found in the examined solution in its bi-protonated state, whereas PP-PhCH₃ is found in its protonated form. In addition, the DFT demonstrates that bi-protonated PP-PhCl is a stronger surface protector for C-steel than protonated PP-PhCH₃. According to FMO's theory and Fukui indices, the primary active sites that provide this protection are NH₂, N-pyrazole heteroatoms, and O-pyran heteroatoms. In actuality, Monte Carlo simulation (MC) has demonstrated that the molecule's orientation face to the C-steel surface is caused by (-PhCl) and (-PhCH₃).

The objective of our paper is to compare the CO₂ adsorption and the kinetic studies of ZSM-5 zeolite and activated carbon (AC). Both adsorbents were described with N₂ adsorption–desorption isotherm, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The CO₂ adsorption isotherms were collected at different temperatures over a wide range of pressures and modeled with the Langmuir and Freundlich models. The characterization results showed that AC exhibited larger total pore volume, higher BET surface area, and higher crystallinity in comparison with the ZSM-5 zeolite. The results showed that the quantities of CO₂ adsorbed on the AC were greater than on ZSM-5, since AC exhibits more important textural parameters than zeolite. Furthermore, the Langmuir model provides the perfect adjustment to the experiments, with a correlation coefficient (R²) of 0.99. The CO₂ adsorption kinetics can be depicted by the linear driving force (LDF) model. With rising temperature, the mass transfer constants of CO₂ adsorption on the two adsorbents rise. With increasing pressure, the adsorption activation energy Ea for CO₂ on both adsorbents is reduced. Moreover, the $�\left(\mathrm{Ea}\right)$ of AC was higher than that of zeolite ZSM-5 at low pressure. The findings can be integrated into the adsorption system for removing CO₂ from the gases.

Fossil-based fuels led to the excessive increase in atmospheric CO₂ leading to global warming and climate change. One of the methods to overcome the issue is CO₂ capture and sequestration. In this view, in the present work, an activated rice husk biochar (ARHBC) was synthesized due to its excellent CO₂ capture properties. In addition, a mixture was prepared with bitumen and 6% ARHBC to study the adsorption isotherm and reaction kinetic behaviour for road construction application. The adsorption isotherms and reaction kinetics for ARHBC as well as the mixture were measured at various temperatures like 298–328 K with the supply pressure till 5 bar, using in-house fabricated Sievert's apparatus. The CO₂ storage of 0.33, 0.05 and 0.02 g/g of ARHBC, mixture and bitumen, respectively, was observed at 5-bar supply and ambient temperature. In addition, physical characterizations like BET, SEM, FTIR and TGA were carried out to understand the CO₂ capture behaviour of adsorbents. Thereafter, the adsorption isotherms were modelled using the Langmuir isotherm model, whereas the reaction kinetics were modelled using the pseudo–second-order kinetic model and validated successfully with experimental data. The coefficient of correlation and normalized standard deviation indicate that the predicted isotherm and kinetic data closely correspond with the experimental values. Later, the adsorption isotherms of ARHBC were predicted for higher equilibrium pressure of 100 bar, which is observed to be similar to isotherms reported in literature.

The n-butane isomerization process, which involves its conversion into branched chain hydrocarbons such as isobutane, produces high octane-rating fuel. This fuel is essential for spark ignition engines to generate high power output while ensuring a high fuel economy and long lifespan. This process is typically performed in a distillation column with a packed bed tubular reactor to enhance the conversion. However, most of the control systems proposed in the literature rely heavily on experience and rule-of-thumb, which often results in a suboptimal control system. This situation is particularly evident for a highly integrated plant, such as a plant with a combination of reactors and recycling streams. Hence, in this project, a framework called integrated framework of simulation and heuristics (IFSH) will be demonstrated for the n-butane isomerization process to build a plantwide control system that embeds the simulation into the plantwide control design to support heuristic decision-making. The results showed that the plantwide control system reduced the operating cost by 0.15% to 0.24% during reduced feed flow or isobutane composition. In exchange for a small variation in operating cost, a relatively long process settling time is required due to tight composition control.

Clay-rich high-phosphorus oolitic iron ore (HPOIO) represents a refractory low-grade iron resource that has rarely been documented in the literature. On the basis of detailed mineralogical characterization, this study developed a process for iron enrichment and phosphorus removal. Mineralogical analysis revealed a predominant particle size distribution of 0–5 μm, with hematite intimately intergrown with gangue minerals forming complex concentric ooids. Notably, the ores presented significantly higher contents of SiO₂ (25.46%), Al₂O₃ (10.56%), and FeO (19.44%) than conventional HPOIO. Crucially, extensive Fe–Al isomorphic substitution occurred, resulting in more than 35% of the iron existing as iron silicate phases. These unique characteristics render the ore exceptionally resistant to liberation, reduction, and separation compared with typical HPOIO. Process optimization demonstrated that neither standalone physical separation nor chemical leaching could yield a suitable iron concentrate. Through an innovative integrated process combining magnetizing roasting, magnetic separation, and sequential alkali/acid leaching, a final concentrate was obtained with 58.11% TFe and 0.052% P, with an iron recovery of 63.53%. Magnetizing roasting converted hematite to magnetite, enabling rough concentrate recovery, whereas combined alkali–acid leaching effectively removed phosphorus and silicon impurities. This novel approach overcomes the processing challenges of HPOIO, achieving simultaneous iron upgrading and impurity control.

Conventional polymer-based binders have been extensively utilized in lithium-ion batteries (LIBs); however, their high cost and disposal challenges have raised environmental and economic concerns in recent years. Consequently, there is increasing interest in identifying alternative binder materials that can retain or enhance battery performance. In this study, electrode slurries were fabricated using various ratios of polyvinylidene fluoride (PVDF) and petroleum pitch (SM260) to develop a composite binder. To optimize physical and electrochemical performance, LIBs incorporating the PVDF/SM260 composite binder were systematically evaluated through charge–discharge testing, electrochemical impedance spectroscopy (EIS), and adhesion strength measurements using a universal testing machine (UTM). The optimized LIBs demonstrated a discharge capacity of 432 mAh g⁻¹, an initial coulombic efficiency (ICE) of 94%, and an adhesion strength of 35.4 g_f mm⁻¹ at a slurry composition ratio of 90 wt% (active material, AM): 1 wt% (conductive material, CM): 9 wt% (binder material, BM). These findings indicate that the PVDF/SM260 composite binder offers significant potential as a viable replacement for conventional PVDF binders in LIB applications.