Search Results (207)

Industrial control of volatile organic compound (VOC) emissions from medium-density fibreboard (MDF) production remains constrained by a shortage of compound-resolved evidence from full-scale plants, where wood furnish, amino resin chemistry, heat transfer, gas flow, and wet gas cleaning act simultaneously. Here, we analysed more than 20,000 synchronized operating records from a full-scale single-stage flash-tube MDF dryer at an industrial SWISS KRONO production line and linked total VOC (TVOC) measurements from flame ionization detection with Fourier-transform infrared speciation on the cleaned stack. Five compounds—α-pinene, 3-carene, limonene, methanol, and formaldehyde—accounted for more than 80% of the resolved VOC signal. Process–state contrasts showed that higher digester residence time, discharge screw speed, adhesive amount, urea amount, dryer inlet temperature, and scrubber–water temperature increased one or more representative compounds, whereas higher hardwood share, additional flue-gas supply, and higher scrubber–water pH decreased them. Limonene, methanol, and formaldehyde were substantially more process-sensitive than α-pinene. An exploratory decorrelation step further showed that a drying/throughput domain explained about half of the variability of the screened process space. The study therefore identifies the small set of compounds and operating domains that most strongly govern the cleaned dryer-stack signature and provides a mechanistically grounded prioritization framework for follow-up causal experiments, source apportionment, and emission-mitigation design in industrial MDF manufacture. Unlike product or chamber emission studies, this work links the compound-resolved FTIR/FID chemistry of the final cleaned industrial stack with synchronized production variables; it therefore addresses a scale-integration gap by transforming routine compliance-type exhaust monitoring into a process-diagnostic framework for ranking emission sources, abatement-sensitive variables, and mitigation experiments. Full article

Elemental mercury (Hg⁰) in coal-fired flue gas has become a focal yet challenging issue in mercury pollution control due to its high toxicity, bioaccumulation potential, and high volatility. There is an urgent need to develop a technology of Hg⁰ catalytic oxidation that is both low-cost and highly efficient. On the other hand, waste fluid catalytic cracking (WFCC) catalysts generated from the petroleum refining industry are classified as hazardous solid waste, necessitating effective harmless disposal and resource recovery. Herein, a composite support (A-P) was constructed by combining an activated WFCC catalyst (AFCC) with the natural mineral palygorskite, followed by the loading of VO_x active species to prepare a Vx/A-P catalyst for Hg⁰ removal from flue gas. Moreover, the effects of the preparation process and conditions of the Vx/A-P catalyst on the Hg⁰ removal performance were systematically studied. This work aims to provide a theoretical basis and technical support for the development of low-cost, high-performance mercury removal catalysts, while also promoting the green recycling and value-added utilization of waste catalysts. Full article

Achieving selective SO₂ capture at low pressures is pivotal and challenging for possible flue gas desulfurization and air pollution control. In this study, we synthesized a series of ionic covalent organic frameworks (iCOFs) with β-ketoenamine linkages and sulfonic acid groups using a solvothermal method. TpPa-SO₃H and TpBD-(SO₃H)₂ show a higher SO₂ uptake of 4.46 and 5.24 mmol g⁻¹ than TpPa-1 (4.24 mmol g⁻¹) at 1 bar and 298 K, respectively, due to the combination of the good SO₂ affinity of the polar sulfonic acid groups, higher pore volumes, and the good stability of β-ketoenamine COFs. TpBD-(SO₃H)₂ captured 2.83 mmol g⁻¹ of SO₂ at 0.1 bar and 298 K, which is 1.6 times higher than TpPa-1 (1.82 mmol g⁻¹) under the same conditions. Notably, the IAST SO₂/CO₂ selectivity of TpBD-(SO₃H)₂ and TpPa-1 are 61 and 51, respectively, reflecting the impact of the incorporated SO₃H groups’ higher affinity toward SO₂. Notably, the multicomponent gas mixture breakthrough experiments confirm that TpBD-(SO₃H)₂ displays longer breakthrough time than TpPa-1 (987 vs. 311 min g⁻¹). These β-ketoenamine iCOFs demonstrate nearly complete retention of crystallinity and porosity after exposure to dry or humid SO₂. This work demonstrates that iCOFs are promising adsorbents for SO₂ capture due to their high capacity, stability, and affinity for SO₂ at low pressure. Full article

Dust concentration control in coal-fired power plants is challenged by large time delays and various disturbances, particularly in dry electrostatic precipitator-wet flue gas desulfurization (DESP-WFGD) processes, where the inner-loop dynamics are slower than those of the outer loop, limiting the effectiveness of conventional cascade tuning methods. This paper proposes a compensation-based simultaneous tuning method for cascade proportional-integral-derivative (PID)-PID control systems. The cascade structure is transformed into an equivalent single-loop system, allowing the outer-loop controller to reshape the equivalent plant dynamics. An equivalent controller is then designed using the simple internal model control method, from which the inner-loop controller is derived. Controller parameters are iteratively refined based on maximum sensitivity, overshoot, and integral absolute error. A feedforward controller is further introduced to reject measurable outer-loop disturbances. Simulation results under nominal, uncertain, and noisy conditions show that the proposed method achieves zero overshoot, improved robustness, and smoother control action compared with conventional separate tuning and Lee’s simultaneous tuning method. The proposed approach provides an effective and practical solution for dust concentration control in DESP-WFGD processes, and is extendable to industrial cascade systems with similar dynamic characteristics. Full article

Ceramic membranes show potential for high-temperature CO₂ extraction from flue gas; nevertheless, their performance under simultaneous heat and pressure stress is not well comprehended. This research addresses the temperature-dependent CO₂/N₂ separation characteristics of a commercial ceramic membrane (pore size ~0.1–1 µm) utilizing simulated flue gas (11.8% CO₂, 74.2% N₂, 2.5% O₂, remainder CH₄) at temperatures ranging from 60 to 140 °C and pressures between 4 and 6 bar. Calibrated GC-TCD was used to quantify permeate compositions across multiple operating valve openings. With a CO₂/N₂ selectivity (α) of 0.75 at 4 bars, the maximum CO₂ enrichment peaked at 80 °C (10.8 mol%), getting close to the Knudsen diffusion limit (0.80). Selectivity decreased dramatically beyond 100 °C—α = 0.61 (100 °C), 0.45 (140 °C)—and CO₂ dropped to 5.8% at 4 bar and 2.2% at 6 bars. Viscous flow dominance was shown by the strong pressure amplification—α decreased by more than 60% from 4 to 6 bar at all temperatures. These findings emphasize the possibility of performance collapse in hot, pressured flue streams and identify the limited operating window under which Knudsen-controlled transport can be maintained. The study provides quantitative evidence of a transition in transport regime under mixed flue-gas conditions. Full article

The global energy transition and the implementation of carbon capture, utilization, and storage (CCUS) strategies require energy-efficient and scalable CO₂ separation technologies. Mixed-matrix membranes (MMMs), combining polymer matrices with functional inorganic or hybrid nanofillers, have emerged as advanced separation platforms capable of surpassing the conventional permeability–selectivity trade-off observed in neat polymer membranes. This review critically evaluates recent developments in modern hybrid membranes for CO₂ separation from synthetic and industrial gas mixtures, including CO₂/N₂ (flue gas), CO₂/CH₄ (natural gas and biogas upgrading), and syngas systems. Particular emphasis is placed on MMMs incorporating covalent organic frameworks (COFs), metal–organic frameworks (MOFs), graphene oxide (GO), MXenes, transition metal dichalcogenides (TMDs), carbon nanotubes (CNTs), g-C₃N₄, layered double hydroxides (LDH), zeolites, metal oxides, and magnetic nanoparticles. Reported performance ranges include CO₂ permeability (P_CO2) typically between 100 and 800 Barrer, CO₂/N₂ selectivity up to 319, and CO₂/CH₄ selectivity up to 249, depending on filler chemistry, loading, and interfacial compatibility. The mechanisms governing gas transport—molecular sieving, selective adsorption, facilitated transport, and diffusion-pathway engineering—are systematically discussed. Key challenges addressed include filler dispersion, polymer–filler interfacial defects, physical aging, moisture sensitivity, oxidation (particularly in MXenes), and scalability toward industrial membrane modules. Future perspectives focus on sub-nanometer pore engineering, surface functionalization to enhance CO₂ affinity, controlled alignment of 2D nanosheets to promote directional transport, multifunctional core–shell and hollow structures, and the integration of computational modeling and machine learning for accelerated material design. Modern hybrid MMMs are identified as strategically important materials enabling high-efficiency CO₂ separation processes aligned with decarbonization and energy transition objectives. Full article

The performance of diffusion flame (DF) burners strongly depends on how effectively combustion gases mix and retain heat, yet the influence of exhaust nozzle geometry on these processes remains insufficiently characterized. This study examines how varying exhaust nozzle angle affects the thermal behavior and emissions of a methane (CH₄) diffusion flame under atmospheric conditions. A laboratory-scale burner with interchangeable exhaust nozzles (0°, 25°, and 50°) was operated at 1.8 kW using a fixed methane flow of 3 L/min and co-swirled air and fuel at 30°, across equivalence ratios (Φ) of 1.0, 0.7, and 0.5. Axial temperature measurements and exhaust gas analyses (Carbon dioxide (CO₂) and Carbon monoxide (CO)) were conducted to assess mixing, heat retention, and post-flame oxidation. Results show that exhaust nozzle geometry notably influences flame position and heat distribution, producing non-monotonic temperature trends with equivalence ratio. The 25° nozzle angle yielded the highest near-stoichiometric downstream and flue temperatures, reaching about 204 °C at x = 45 cm and 277 °C in the flue, compared with 72 °C and 177 °C for the 0° nozzle. In contrast, the 50° nozzle produced more uniform downstream temperatures (about 150–160 °C) and the lowest CO emissions, approaching zero near Φ ≈ 1.0. These findings demonstrate that coordinated control of swirl and exhaust nozzle angle can enhance thermal response and CO reduction in diffusion flame burners without significantly changing CO₂ levels. Full article

Industrial emissions of large amounts of CO₂ have seriously affected human health, making it imperative to reduce atmospheric CO₂ concentrations. However, carbon capture technologies such as chemical absorption and membrane separation are still limited by high regenerative energy costs, corrosion, and low efficiency in diluting flue gas. Within this technological landscape, physical adsorption separation technology, due to its advantages such as a wide operating temperature range, low equipment corrosivity, and low regeneration energy consumption, has gradually become a research hotspot in carbon capture technology. The core of physical adsorption lies in finding high-quality adsorbents. Metal–organic frameworks (MOFs), with their ultra-high specific surface area, tunable pore structure, and abundant functionalization sites, are considered highly promising next-generation CO₂ adsorbent materials. This review summarizes strategies for modifying MOFs to improve CO₂ adsorption performance, focusing on aperture adjustment, doped metal ions, functional group doping, and computational screening. Performance enhancements are mechanism-dependent rather than simply additive. Moderate aperture adjustment and defect engineering can improve gas selectivity and CO₂ capture capacity, while excessively narrow pores sacrifice available pore volume and gas diffusion. Doped metal ions, particularly in MOF-74 and related materials, can enhance CO₂ capture capacity while controlling framework integrity and dopant composition. Functional group Doping remains an effective method for capturing low-partial-pressure CO₂. Computational screening is shifting from ranking based on single adsorption capacity to a comprehensive consideration that includes humidity tolerance, stability, and regenerability. Overall, under industrial conditions, modified MOFs should be evaluated by balancing affinity, selectivity, capacity, stability, and energy efficiency. This review provides guidance for the rational design of MOF-based carbon capture adsorbents. Full article

The management of hazardous municipal solid waste incineration (MSWI) residues represents a critical challenge for sustainable development due to their increasing generation and environmental risk. At the same time, the cement industry faces urgent pressure to reduce CO₂ emissions associated with clinker production, creating a demand for alternative supplementary cementitious materials. The aim of this study was to evaluate the feasibility of valorising hazardous municipal solid waste incineration (MSWI) air pollution control fly ash (EWC 19 01 07*) as a constituent of Portland composite cement, in line with circular economy principles and the need to reduce CO₂ emissions associated with clinker production. The investigated fly ash, originating from flue gas cleaning processes, is characterised by high alkalinity and elevated concentrations of heavy metals, which currently necessitate controlled landfilling. To enable its safe reuse, the ash was subjected to high-temperature thermal treatment following granulation and subsequently incorporated into cement formulations under semi-industrial conditions. Two Portland composite cements were produced with different ash contents, corresponding to CEM II/A-07 and CEM II/B-07, while a Portland cement manufactured from the same clinker was used as a reference material. The chemical and phase composition of the ash before and after thermal treatment was analysed using XRF and XRD, supported by SEM/EDS observations. The results demonstrate that thermal treatment at 1150 °C induces partial phase stabilisation of APC fly ash without full vitrification, allowing its integration into cement systems under semi-industrial conditions. The incorporation of ash significantly alters hydration behaviour through increased water demand governed by particle porosity, CaO-rich phase composition, and early ionic interactions in the pore solution, leading to reduced workability and mechanical performance. While immobilisation efficiencies exceeding 99.5% were achieved for most heavy metals due to precipitation and incorporation into hydration products, barium exhibited persistent leaching controlled by its solubility under highly alkaline conditions and limited incorporation into C–S–H phases. These findings define both the technological feasibility and the key environmental constraints of APC fly ash utilisation in Portland composite cement. From a sustainability perspective, the proposed approach contributes to the reduction in hazardous waste landfilling and supports clinker substitution in cement production. The results demonstrate the potential of integrating waste management and low-carbon material design within a circular economy framework while highlighting current environmental limitations related to barium leaching. Full article

Biomass combustion, as a key technology for achieving a low-carbon transformation of the energy system, faces multiple challenges in its efficient and clean utilization, including the high heterogeneity of fuels, the complex multi-scale coupling of the combustion process, and the attainment of ultra-low emissions. Traditional research methods have significant disconnections between microscopic mechanism understanding, macroscopic performance prediction of reactors, and end-of-pipe pollution control, which restricts the improvement of system performance. This review presents recent advances in advanced numerical simulation, pollutant control strategies, and bioenergy with carbon capture and storage (BECCS) pathways targeting ultra-low emissions in biomass combustion. This work synthesizes progress across three interconnected domains. First, methodologies are examined for integrating detailed chemical kinetics, particle-scale models, and reactor-scale simulations to develop high-fidelity predictive tools. Second, low-nitrogen combustion and synergistic pollutant control strategies for primary furnace types (e.g., grate, fluidized bed) are evaluated, alongside process optimization from fuel pretreatment to flue gas purification. Third, the potential for integrated design of biomass energy systems with carbon capture is assessed, emphasizing that system efficiency hinges on holistic “fuel-combustion-capture” chain optimization rather than isolated unit improvements. Future research directions are highlighted, including the development of physics-informed AI modeling paradigms, deeper co-design of multiple processes, and the establishment of robust life-cycle assessment frameworks. This review aims to provide a structured reference to inform both fundamental research and the practical development of next-generation clean biomass combustion technologies. Full article

Oxy-fuel combustion is a near-zero emission technology that utilizes high-concentration O₂ in place of air, combined with recycled flue gas, to achieve efficient combustion and enable effective CO₂ capture. In this study, air (21% O₂/79% N₂) was used as the control atmosphere, and rice straw combustion experiments were conducted using thermogravimetric analysis and differential scanning calorimetry and differential scanning calorimetry coupled with mass spectrometry (TG-MS) at heating rates of 10, 20, and 30 °C/min under oxy-fuel conditions of 30% O₂/70% CO₂, 50% O₂/50% CO₂, and 70% O₂/30%CO₂. The combustion behavior, pollutant emissions, reaction kinetics, and underlying mechanisms were systematically evaluated. The results show that CO₂ in oxy-fuel atmospheres exhibits a higher thermal inertia, due to its greater density and specific heat capacity, thereby enhancing flame stability. Oxy-fuel atmospheres reduce the ignition temperature (Tᵢ) and burnout temperature (T_f), shorten the combustion duration, shift DTG and DSC peaks to lower temperatures, and result in sharper peaks along with an increased ignition index (Cᵢ), burnout index (C_b), and comprehensive combustion index (S). Mass spectrometry (MS) analysis reveals that oxy-fuel atmospheres combined with heating rates of 20–30 °C/min suppress O₂ diffusion and thermal NO formation, reducing NO_x emissions by over 75% and simultaneously inhibiting the release of SO₂ and COS. Kinetic analysis using the FWO and Friedman methods shows that the activation energy decreases from 210.5 kJ/mol and 219.1 kJ/mol under air conditions to 110.5 kJ/mol and 114.6 kJ/mol in oxy-fuel atmospheres, representing a reduction in reaction barriers of 47.5% and 47.7%, respectively. The reaction mechanisms were identified as three-dimensional diffusion-controlled processes at heating rates of 20–30 °C/min, and random nucleation followed by growth under high O₂ concentration conditions at a heating rate of 30 °C/min. Optimizing the combustion atmosphere and heating rate enhances the rice straw combustion efficiency and reduces pollutant emissions, thereby providing theoretical support for its clean and efficient utilization. Full article

Supersulfated cement (SSC) is an environmentally friendly cementitious material with a low clinker content, in which industrial byproduct gypsum serves as the sulfate source, thereby enabling the valorization of solid waste. The hydration process, pore structure, microstructure, and hydration products were investigated using paste samples by means of isothermal calorimetry, X-ray diffraction (XRD), thermogravimetric analysis (TG–DTG), Fourier transform–infrared spectroscopy (FT-IR), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM), while compressive strength was evaluated using mortar specimens. Compared with ordinary Portland cement (OPC), SSC offers clear advantages in reducing energy consumption and greenhouse gas emissions. In this study, the effects of titanium gypsum (TG) and flue gas desulfurization gypsum (FGD) on the hydration behavior, fluidity, mechanical properties, and microstructural evolution of an anhydrite (AH)–phosphogypsum (PG)-based SSC were systematically investigated. The results indicate that the incorporation of 11% TG and FGD mitigates the strong sulfate environment caused by the rapid dissolution of soluble AH, thereby regulating the hydration process. As the proportion of TG and FGD increased, the cumulative heat release within 72 h gradually decreased. When AH was completely replaced, the cumulative heat release of TG4 and FG4 decreased by approximately 19.7% and 28.6%, respectively. TG and FGD exhibited opposite effects on the fluidity of SSC while both promoting strength development. Among all mixtures, TG2 and FG2 showed the best performance, with the highest 28-day compressive strengths of 50.15 MPa and 51.95 MPa, respectively. Microstructural analysis reveals that differences in particle size distribution and dissolution kinetics among gypsums governed the sulfate release characteristics and slag activation mechanisms, thus leading to distinct hydration pathways, pore structure evolution, and microstructural densification. This study provides a theoretical basis for the efficient utilization of various industrial byproduct gypsums and offers important guidance for the controllable design of SSC performance. Full article

Accurate and stable measurement of carbon dioxide (CO₂) concentrations in industrial flue gases is critical for emissions monitoring and carbon management. The present study developed a wavelength-modulated tunable diode laser absorption spectroscopy (WMS-TDLAS) system for measuring high-concentration carbon dioxide (CO₂) in flue gases, covering a range of 3–20% (by volume). To mitigate optical intensity fluctuations caused by particle scattering and detector gain drift in harsh flue gas environments, a normalized second harmonic (2f/1f) detection scheme based on a single-harmonic peak was employed. A digital phase-locked amplification algorithm replaces the conventional hardware lock-in amplifier, enabling simultaneous demodulation of multiple harmonic components and enhancing system integration. A comparison of the digital locking method with a commercial lock-in amplifier reveals that the former demonstrates comparable or superior stability, with relative standard deviations of 0.04% for the 2f signal and 0.02% for the first-harmonic signal. In order to address the sensitivity degradation of WMS-TDLAS at elevated CO₂ concentrations, a pressure control strategy was introduced. Maintaining the measurement cell pressure at 70 ± 0.005 kPa resulted in a 2.74-fold enhancement in system sensitivity at 13.01% CO₂ and a more than one-order-of-magnitude increase at 20.01% CO₂ compared to operation at atmospheric pressure. Concentration measurement error under reduced pressure also decreased from 1.101% to 0.075%. The system exhibited 0.6% repeatability in high-concentration CO₂ measurements, signifying its aptitude for industrial flue gas monitoring applications. Full article

Focusing on enhancing the performance of the ¹⁴C method in determining biomass–coal co-combustion ratios, this study developed two novel sample preparation systems: a direct flue gas injection benzene synthesis system based on Liquid Scintillation Counting (LSC) and a direct flue gas sealing graphitization system based on Accelerator Mass Spectrometry (AMS). These systems reduced sample preparation time from 20–24 h to 6–8 h. Experimental validation showed relative errors in biomass blending ratios (1–40%) below ±4% for LSC and ±3% for AMS, except at the 1% blending condition. Compared with conventional methods, both accuracy and efficiency were significantly improved. An enhanced ¹⁴C-based industrial measurement scheme was established and successfully applied for monitoring biomass blending ratios (15–50%) in industrial facilities. Deviations between AMS and LSC were within ±3%, confirming the method’s accuracy, despite discrepancies with the Distributed Control System (DCS) estimates. Additionally, predictive formulas for ¹⁴C activity in biomass and air CO₂ reduced economic investment, with relative errors from ±0.04% to ±3.25%. Overall, the new scheme improved accuracy by 50%, efficiency by 60%, and reduced detection costs by 60–80%, demonstrating feasibility and practical value for industrial applications. Full article

Traditional calcium hydroxide (Ca(OH)₂) typically exhibits low specific surface area and reactivity, significantly limiting its efficacy in industrial gas–solid reactions such as flue gas desulfurization and thermochemical energy storage. To address these limitations, this study proposes a two-stage synthesis strategy designed to enhance the surface properties and chemical activity of Ca(OH)₂. The process involves the preparation of high-activity calcium oxide (CaO), followed by controlled hydration using diethylene glycol (DEG). Drawing on established mechanisms from cement chemistry, wherein potassium ions (K⁺) catalyze the decomposition of calcium carbonate (CaCO₃), limestone particles (10–20 mm) were pre-soaked in a 0.1 mol/L potassium nitrate (KNO₃) solution for 48 h prior to calcination. Characterization via X-ray diffraction (XRD), scanning electron microscopy (SEM), and Blaine Air Permeability Method analysis revealed that this pretreatment accelerated decomposition kinetics by inducing surface defects, yielding CaO with a maximum reactivity of 435.7 mL. Subsequent hydration at 80 °C with 70 wt% DEG effectively suppressed particle agglomeration and promoted the formation of thin platelet structures. The resulting Ca(OH)₂ achieved a utilization efficiency of 98.5% and a specific surface area of 43.24 m²/g, demonstrating a robust technical route for fabricating high-performance calcium-based sorbents for environmental and energy applications. Full article