Search Results (1,067)

Carbon capture is an essential technology for reducing industrial CO₂ emissions, particularly in the power and cement sectors. Among the various capture methods, solvent-based absorption systems are widely used due to their efficiency and scalability, making the selection of the right solvent critical for near-term applications. This study analyzes several solvents for use in an absorption-based CO₂ capture system, emphasizing identifying the most suitable solvent for 2025–2030. The research methodology involves process modeling in Aspen Plus, sensitivity analysis, and evaluation of the regeneration duty for each solvent. The objective is to achieve at least 90% CO₂ capture and 95% CO₂ purity. The flue gas composition considered in this analysis is 19.8% CO₂, 9.3% O₂, 63% N₂, 7.5% H₂O, and other trace gases. Various solvents are evaluated to determine their effectiveness in capturing CO₂ while minimizing the energy consumption during solvent regeneration. A sensitivity analysis was conducted to optimize the system’s performance based on the solvent type, operating conditions, and regeneration duty. The results showed that amine blends demonstrated a CO₂ capture rate of 92% and a CO₂ purity of 96%, with regeneration energy requirements of around 3.2 GJ/ton of CO₂, significantly lower than those of traditional MEA systems, which typically require around 4.0 GJ/ton. In contrast, ionic liquids showed a CO₂ capture rate of 89% and a purity of 95%, with a regeneration energy of 2.8 GJ/ton, though their current cost is higher, limiting their immediate large-scale application. Annual capital expenditure (CAPEX) calculation revealed that amine blends could potentially reduce the CAPEX by 15–20% compared to MEA, while amino acid salts showed similar CAPEX reductions with a capture efficiency of 90%. Overall, the results indicate that hybrid amine solvents are the most cost-effective and practical solution for 2025–2030, with ionic liquids and amino acid salts emerging as promising alternatives as their costs decrease. Full article

The increasing atmospheric concentration of carbon dioxide (CO₂) poses a critical threat to global climate stability, highlighting the need for efficient carbon capture technologies. While amine-based solvents such as monoethanolamine (MEA) are widely used for industrial CO₂ capture, they are subject to limitations such as high energy requirements for regeneration, solvent degradation, and environmental concerns. This study investigates potassium carbonate/bicarbonate system as an alternative solution for CO₂ absorption. The absorption mechanism and reaction kinetics of potassium carbonate in the presence of bicarbonates were reviewed. A rate-based model was developed in Aspen Plus, using literature kinetics, to simulate CO₂ absorption using 20 wt% potassium carbonate (K₂CO₃) solution with 10% carbonate-to-bicarbonate conversion under different industrial conditions. Three flue gas compositions were evaluated: cement industry, biomass combustion, and anaerobic digestion, each at 3000 m³/h flow rate. The simulation was conducted to determine minimum column height and solvent loading requirements with a target output of 90% CO₂ removal from the gas streams. Results demonstrated that potassium carbonate systems successfully achieved the target removal efficiency across all scenarios. Column heights ranged from 18 to 25 m, with molar K₂CO₃/CO₂ ratios between 1.41 and 4.00. The biomass combustion scenario proved most favorable due to lower CO₂ concentration and effective heat integration. While requiring higher column heights (18–25 m) compared to MEA systems (6–12 m) and greater solvent mass flow rates, potassium carbonate demonstrated technical feasibility for CO₂ capture. The findings of this study provide a foundation for technoeconomic evaluation of potassium carbonate systems versus amine-based technologies for industrial carbon capture applications. Full article

This study employs numerical simulation methods to systematically analyze the multiphase flow and heat transfer characteristics in a circulating fluidized bed flue gas desulfurization (CFB-FGD) reactor handling ascharite ore roasting flue gas. Based on the simulation results, key structural optimization strategies are proposed. A three-dimensional mathematical model was developed based on the Fluent 19.1 platform, and the multiphase flow process was simulated using the Eulerian-Lagrangian method. The study examined the effects of venturi tube structure, atomized water nozzle installation height, and gas injection disruptor configuration on reactor performance. Optimization strategies for key structural components were systematically evaluated. The results show that the conventional inlet structure leads to significant non-uniformity in the velocity field. Targeted adjustments to the dimensions of venturi tubes at different positions markedly improve the velocity distribution uniformity. Reducing the atomized water nozzle installation height from 1.50 m to 0.75 m increased the temperature distribution uniformity index in the middle part of the straight pipe section by 5.5%. Moreover, a gas injection disruptor was installed in the upper part of the straight pipe section of the CFB-FGD reactor. Increasing the gas injection velocity from 15 m/s to 30 m/s increased the average residence time of desulfurization sorbents by 17.0%. This increase effectively enhances gas–solid mixing within the CFB-FGD reactor. The optimization strategies described above significantly reduced the extent of flow dead zones and low-temperature regions in the CFB-FGD reactor and improved flow conditions. This study provides important theoretical and technical support for the optimization and industrial application of CFB-FGD technology for ascharite ore roasting flue gas. Full article

The conventional method of flue gas desulfurization gypsum (FGDG) application, i.e., blending with flood irrigation, is hindered by low water efficiency and significant amendment loss due to runoff and uncontrolled leaching, particularly in arid and semi-arid regions in which water scarcity is a major constraint. This study aimed to evaluate a novel integration of FGDG band application with drip irrigation to enhance targeting and resource efficiency. A laboratory-scale experiment investigated the effects of two FGDG application methods (band and blend application) and drip rates (0.3 and 0.6 L h⁻¹) on soil water movement and chemical properties. Band application significantly accelerated initial wetting front advancement by up to 44.9 cm h⁻¹ near the emitter and sustained horizontal propagation, while blend application promoted a more uniform water distribution. Chemically, band application created localized zones of reduced pH (7.57–8.62) and elevated water-soluble Ca²⁺ (up to 492.2 mmol kg⁻¹), facilitating a 79.1% reduction in exchangeable Na⁺ near the emitter. In contrast, blend application resulted in broader but shallower amendment distribution, reducing exchangeable sodium percentage uniformly to 1.99–4.16% across the soil profile. The combination of banded FGDG and drip irrigation achieves targeted amelioration, with superior Na⁺/Ca²⁺ exchange and favorable moisture dynamics resulting from the synergy between amendment placement and water delivery. This approach is a viable strategy for precision reclamation in arid regions. Full article

Supercritical carbon dioxide (SC-CO₂) power cycles offer a promising solution for offshore platforms’ gas turbine waste heat recovery due to their compact design and high thermal efficiency. This study proposes a novel parallel-preheating recuperated Brayton cycle (PBC) using SC-CO₂ for waste heat recovery on offshore gas turbines. An integrated energy, exergy, and economic (3E) model was developed and showed good predictive accuracy (deviations < 3%). The comparative analysis indicates that the PBC significantly outperforms the simple recuperated Brayton cycle (SBC). Under 100% load conditions, the PBC achieves a net power output of 4.55 MW, while the SBC reaches 3.28 MW, representing a power output increase of approximately 27.9%. In terms of thermal efficiency, the PBC reaches 36.7%, compared to 21.5% for the SBC, marking an improvement of about 41.4%. Additionally, the electricity generation cost of the PBC is 0.391 CNY/kWh, whereas that of the SBC is 0.43 CNY/kWh, corresponding to a cost reduction of approximately 21.23%. Even at 30% gas turbine load, the PBC maintains high thermoelectric and exergy efficiencies of 30.54% and 35.43%, respectively, despite a 50.8% reduction in net power from full load. The results demonstrate that the integrated preheater effectively recovers residual flue gas heat, enhancing overall performance. To meet the spatial constraints of offshore platforms, we maintained a pinch-point temperature difference of approximately 20 K in both the preheater and heater by adjusting the flow split ratio. This approach ensures a compact system layout while balancing cycle thermal efficiency with economic viability. This study offers valuable insights into the PBC’s variable-load performance and provides theoretical guidance for its practical optimization in engineering applications. Full article

Carbon capture is pivotal for achieving carbon neutrality; however, its high energy consumption severely limits the operational flexibility of power plants and remains a key challenge. This study, targeting a full flue gas carbon capture scenario for a 1000 MW coal-fired power plant, identified the dual-element (“steam” and “power generation”) coupling convergence mechanism. Based on this mechanism, a comprehensive set of mathematical model equations for the “carbon–electricity–heat” coupling process is established. This model quantifies the dynamic relationship between key operational parameters (such as unit load, capture rate, and thermal consumption level) and system performance metrics (such as power output and specific power penalty). To address the challenge of flexible operation, this paper further proposes two innovative coupled modes: steam thermal storage and chemical solvent storage. Model-based quantitative analysis indicated the following: (1) The power generation impact rate under full THA conditions (25.7%) is lower than that under 30% THA conditions (27.7%), with the specific power penalty for carbon capture decreasing from 420.7 kW·h/tCO₂ to 366.7 kW·h/tCO₂. (2) Thermal consumption levels of the capture system are a critical influencing factor; each 0.1 GJ/tCO₂ increase in thermal consumption leads to an approximate 2.83% rise in unit electricity consumption. (3) Steam thermal storage mode effectively reduces peak-period capture energy consumption, while the chemical solvent storage mode almost fully eliminates the impact on peak power generation and provides optimal deep peak-shaving capability and operational safety. Furthermore, these modeling results provide a basis for decision-making in plant operations. Full article

Flue gas is an industrial waste gas produced by the combustion of fossil fuels. Its application in reservoir development can increase oil recovery factor and achieve underground storage of CO₂. Flue gas gravity flooding experiments were conducted to clarify the displacement and storage characteristics of flue gas gravity flooding. The results show that the experiment can be divided into three stages based on the output characteristics, and the oil recovery factor curve exhibits a stepwise increase. During the pure oil production stage, the crude oil output is approximately half of the total output. When the experimental pressure is 18 MPa, the oil recovery factor is 11.53%. As the experimental pressure increases, the extraction and viscosity reduction effects of the flue gas are enhanced. Therefore, the oil recovery factor gradually increases and the crude oil in the micropores and small pores is better displaced. The storage rate of flue gas is 8.42% at a pressure of 18 MPa. When the experimental pressure increases to 25 MPa, the storage rate of flue gas reaches 19.70%. The increase in permeability and the extension of displacement time can effectively improve the oil recovery factor. The research results provide a new approach for the resource utilization of flue gas and offer theoretical support for flue gas flooding in tight reservoirs. Full article

Nitrogen dioxide (NO₂) is a major atmospheric pollutant and also a recoverable nitrogen resource, for which adsorption offers a promising technical pathway. This review systematically summarizes the recent progress in the removal of NO₂ from flue gas by adsorption methods, with a focus on material-level and process-level advancements. From the material perspective, three representative adsorbents—zeolites, activated carbons, and metal oxides—are comparatively evaluated in terms of their physicochemical properties, active sites, and adsorption mechanisms. Emphasis is placed on their adsorption capacity, selectivity, and hydrothermal stability, supported by both experimental and theoretical insights. From the process perspective, four adsorption-based technologies—Pressure Swing Adsorption (PSA), Temperature Swing Adsorption (TSA), Vacuum Pressure Swing Adsorption (VPSA), and Vacuum Temperature Swing Adsorption using multiple Gas circulations (GVTSA)—are analyzed regarding their principles, operational workflows, and engineering applications, with particular attention to the process intensification potential of GVTSA. The review identifies existing challenges in terms of material stability under complex conditions and process scalability, especially for severe environments such as nuclear reprocessing tail gases. Finally, future research directions are proposed toward developing multifunctional composite adsorbents with high capacity, strong environmental tolerance, and excellent regenerability, along with optimized and integrated adsorption processes, to achieve efficient NO₂ abatement and high-value recovery. Full article

Carbon capture and storage (CCS) technologies are an important step to mitigate CO₂ emissions. This study focuses on CO₂ capture from biomass combustion in fluidized bed boilers using a vacuum pressure swing adsorption (VPSA) process. A pilot-scale VPSA unit was used to evaluate the dynamic adsorption behavior of zeolite 13X and clinoptilolite under realistic operating conditions. Moreover, a simplified one-dimensional isothermal mathematical model of a fixed-bed adsorption column was developed to simulate breakthrough curves to validate whether the model reproduces the observed experimental trends. Experimental results confirmed that fresh zeolite 13X exhibited the highest CO₂ adsorption capacity, while clinoptilolite showed moderate uptake. For both sorbents, a decrease in derived adsorption capacity was observed after prior use. The developed mathematical model successfully reproduced the experimental breakthrough curves, achieving coefficients of determination (R²) up to 0.99 and percentage fit (%Fit) values close to 94% for fresh sorbents, while lower correlations were observed for used sorbents. The model reliably captured the breakthrough curves, validating its applicability for process prediction. These results highlight the effectiveness of combining experimental measurements with modeling to assess sorbent performance and guide further optimization of VPSA processes under realistic flue gas conditions. Full article

CO₂ valorization from real feedstocks through CH₄ tri-reforming (CH₄-TR), combining steam reforming (SR), dry reforming (DR), and partial oxidation (CPO) of methane in a single process, is a desirable strategy for greenhouse gas mitigation and syngas (CO + H₂) production. NiCo/γ−Al₂O₃ catalysts prepared by impregnation at different relative metal contents (Ni₅₀Co₅₀ and Ni₃₀Co₇₀) were investigated for CH₄-TR in a fixed-bed reactor under conventional heating and characterized by XRD, FESEM, and Raman spectroscopy after catalytic runs. This study focused on the role of the Ni/Co ratio and feed composition on selectivity for CO₂ valorization, syngas yield, and deactivation resistance. Both the catalysts showed high activity, with a superior performance of Ni₅₀Co₅₀ confirming Ni metal species as the active sites. While in DR, a slow deactivation occurred due to coke deposition, in CH₄-TR, the addition of small O₂ and/or H₂O amounts stabilized activity and selectivity due to surface carbon removal. Large O₂ and H₂O amounts strongly inhibited CO₂ conversion due to competition with CPO and SR, in the order CPO ≥ DR > SR. Interestingly, the stoichiometric CH₄-to-oxidants ratio favored the DR pathway, giving very high CO₂ conversion. Modulating CH₄ addition into real flue mixtures renders CH₄-TR on NiCo/γ-Al₂O₃ catalysts a favorable strategy for effective valorization of CO₂ industrial or biomass-derived streams. Full article

The CO₂ capture process in coal-fired power plant flue gas still faces the difficulties of low material performance and high energy and cost consumption. It is necessary to develop new capture solvents and materials, and also new capture process configurations, to achieve breakthroughs in capture performance and process technology. In various process configurations for CO₂ absorption, lean solution vaporization and compression (LVC) is a commonly used and effective one for reducing the energy and cost consumption. This work propose a partial lean solution vaporization and compression (PLVC) configuration to decrease energy and cost consumption for CO₂ capture, considering the price difference in heat and electricity with the high prices of compressors. The three heat exchange methods of no heat exchange, separate heat exchange, and merged heat exchange for lean solution after flash evaporation are also proposed with PLVC, which could be used in the range of low (0–25%), middle (25–75%), and high split ratios (75–100%) of lean solution for the lowest total heat consumption of the aqueous AMP + PZ solvent. Therefore, the comprehensive cost of the capture process can be minimized by considering different prices of steam heat, electricity, and compression facility. Full article

Ammonia–coal co-firing is emerging as a promising technological pathway to reduce carbon production during coal-fired power generation. However, the coupling effects of the ammonia energy ratio (E_NH3) and equivalence ratio on the ignition mechanism and emission characteristics—particularly under staged injection conditions—remain insufficiently understood. This study investigates these characteristics in a laboratory-scale furnace. Spontaneous chemiluminescence imaging and flue gas analysis were employed to decouple the effects of aerodynamic interactions and chemical kinetics. The experimental results reveal that the ammonia injection strategy is the critical factor governing coal ignition performance. Compared to the premixed mode, staged injection—which establishes an independent, high-temperature ammonia flame zone—provides a superior thermal environment and circumvents oxygen competition between the fuels, thereby markedly promoting coal ignition. At an E_NH3 of 50%, the staged configuration reduces the ignition delay time of coal volatiles by a striking 60.93%. Within the staged configuration, increasing either the co-firing ratio or the overall equivalence ratio further enhances coal ignition. Analysis of pollutant emissions elucidates that the formation of NO, N₂O, and NH₃ is intimately linked to the local combustion conditions of ammonia. An excessively lean local equivalence ratio leads to incomplete ammonia combustion, thereby increasing N₂O and NH₃ slip. Full article

As the energy structure evolves, low-load operation of coal-fired boilers is becoming common, posing challenges to combustion stability. This study explored the co-combustion of brown gas (HHO) with bituminous coal and anthracite in a one-dimensional furnace. Results indicate that introducing HHO significantly elevated combustion temperatures, with maximum increases of 158 °C and 207 °C, respectively. In the premixed mode, the flame front shifted upstream, indicating advanced ignition timing. Moreover, HHO co-combustion notably enhanced the combustion stability of anthracite, as reflected in stabilized furnace temperatures. With increasing HHO flow rate, CO concentrations from both bituminous coal and anthracite were reduced by over 80%. The combustion efficiency of bituminous coal reached 98%, while the combustion efficiency of anthracite increased by 19% (premixed) and 13% (staged), confirming the premixed mode’s superiority in promoting complete combustion. HHO co-combustion increased SO₂ emissions but had a complex effect on NO_X emissions due to the competition between NO_X reduction caused by HHO and NO_X formation caused by the increased combustion temperature. HHO co-combustion changed the melting point of fly ash, increased the content of Al₂O₃, and reduced the content of Na₂O, K₂O, and MgO, influencing the slagging behavior of the boiler and the subsequent management of fly ash. Full article

Zeolites and molecular sieves have demonstrated remarkable potential in adsorption, ion exchange, and separation processes since their industrial revolution in the 1950s. Zeolites and molecular sieves are materials of choice in separation applications because of their well-defined microporous architecture, remarkable shape-selectiveness, and tunable characteristics. The adsorption process can be evaluated using an isotherm to determine the feasibility of gas mixture separation for practical applications. We will also discuss the basic structure of zeolites and molecular sieves based on different metals, along with their distinctive properties in detail. The purpose of this review is to contextualize the importance of zeolites and molecular sieves in adsorption and separation applications. The review has been divided into groups based on how zeolites as well as molecular sieves are established in the adsorption and separation processes. The fundamental adsorption characteristics, structures, and various separation methods that make zeolites appealing for different uses are covered. By incorporating knowledge of adsorption mechanisms, isotherms, and material changes, this review discusses the most recent developments. To augment zeolite-based materials for certain pollutant removal applications, it offers a strategic framework for future study. In this review, we will comprehensively discuss a range of separation and adsorption applications, including wastewater purification, CO₂ capture from flue gases, and hydrogen storage. Furthermore, the review will explore emerging prospects of zeolites and molecular sieves in innovative fields such as energy storage, oil refining, and environmental remediation. Emphasis will be placed on understanding how their tunable pore structures, surface chemistry, and metal incorporation can enhance performance and broaden their applicability in sustainable and clean energy systems. Full article

Barium slag is classified as a hazardous waste due to its high content of soluble Ba²⁺. To achieve safe disposal and high-value utilization, this study developed a novel all-solid-waste road base material by synergistically combining harmlessly treated barium slag (HTBS) with steel slag, blast furnace slag, and flue-gas-desulfurization gypsum (SWB). The primary novelty of this work lies in the dual-immobilization mechanism of barium within a multi-solid-waste cementitious system. Our results showed that the mixture containing 16% binder achieved unconfined compressive strengths of 4.24 MPa (7 days) and 8.06 MPa (28 days), meeting the technical requirements for heavy-load road bases. Microstructural analyses revealed that the system evolved into a dense network composed of C–S–H gels and ettringite (AFt). Mechanistically, environmental safety is ensured by two pathways: (1) the chemical precipitation of stable BaSO₄ and (2) the physical encapsulation of ions by the dense gel matrix. Leaching tests confirmed that Ba concentration remained far below the regulatory limit, ensuring environmental safety. This work provides a scalable, eco-friendly solution for the “waste-to-resource” conversion of hazardous barium slag in road engineering. Full article