Flue Gas Research Articles

Insights into local wall erosion characteristics and prevention measures for cyclone separators

Cyclone separators are separation devices that use the principle of inertia to remove particulate matter from flue gases. The present study mainly focuses on wall erosion in cyclone separators and associated research. The main locations of erosion in gas–solid cyclone separators, including the entrance impact section, cyclone roof corner, vortex finder outer surface, spiral-type erosion strip, and lower cone section, are examined in detail. The main factors influencing wall erosion are discussed, including inlet flow velocity, solid particle properties and loading, geometrical structure, and manufacturing quality. Finally, several practically preventive measures against wall erosion are presented, including adjustment of operating conditions, the use of erosion-resistant materials, optimization of geometrical structures, and the addition of auxiliary devices, all of which are essential for ensuring operational efficiency, equipment reliability, safety, and environmental protection in various industrial applications. This paper aims to provide a basis for further research into erosion in cyclone separators as well as guidance for engineers involved in their industrial applications.

Tailoring d‐Band Center of Single‐Atom Nickel Sites for Boosted Photocatalytic Reduction of Diluted CO2 from Flue Gas

AbstractPhotocatalytic reduction of diluted CO2 from anthropogenic sources holds tremendous potential for achieving carbon neutrality, while the huge barrier to forming *COOH key intermediate considerably limits catalytic effectiveness. Herein, via coordination engineering of atomically scattered Ni sites in conductive metal–organic frameworks (CMOFs), we propose a facile strategy for tailoring the d‐band center of metal active sites towards high‐efficiency photoreduction of diluted CO2. Under visible‐light irradiation in pure CO2, CMOFs with Ni‐O4 sites (Ni‐O4 CMOFs) exhibits an outstanding rate for CO generation of 13.3 μmol h−1 with a selectivity of 94.5 %, which is almost double that of its isostructural counterpart with traditional Ni‐N4 sites (Ni‐N4 CMOFs), outperforming most reported systems under comparable conditions. Interestingly, in simulated flue gas, the CO selectivity of Ni‐N4 CMOFs decreases significantly while that of Ni‐O4 CMOFs is mostly unchanged, signifying the supremacy for Ni‐O4 CMOFs in leveraging anthropogenic diluted CO2. In situ spectroscopy and density functional theory (DFT) investigations demonstrate that O coordination can move the center of the Ni sites′ d‐band closer to the Fermi level, benefiting the generation of *COOH key intermediate as well as the desorption of *CO and hence leading to significantly boosted activity and selectivity for CO2‐to‐CO photoreduction.

Tailoring d-Band Center of Single-Atom Nickel Sites for Boosted Photocatalytic Reduction of Diluted CO2 from Flue Gas.

Photocatalytic reduction of diluted CO2 from anthropogenic sources holds tremendous potential for achieving carbon neutrality, while the huge barrier to forming *COOH key intermediate considerably limits catalytic effectiveness. Herein, via coordination engineering of atomically scattered Ni sites in conductive metal-organic frameworks (CMOFs), we propose a facile strategy for tailoring the d-band center of metal active sites towards high-efficiency photoreduction of diluted CO2. Under visible-light irradiation in pure CO2, CMOFs with Ni-O4 sites (Ni-O4 CMOFs) exhibits an outstanding rate for CO generation of 13.3 μmol h-1 with a selectivity of 94.5 %, which is almost double that of its isostructural counterpart with traditional Ni-N4 sites (Ni-N4 CMOFs), outperforming most reported systems under comparable conditions. Interestingly, in simulated flue gas, the CO selectivity of Ni-N4 CMOFs decreases significantly while that of Ni-O4 CMOFs is mostly unchanged, signifying the supremacy for Ni-O4 CMOFs in leveraging anthropogenic diluted CO2. In situ spectroscopy and density functional theory (DFT) investigations demonstrate that O coordination can move the center of the Ni sites' d-band closer to the Fermi level, benefiting the generation of *COOH key intermediate as well as the desorption of *CO and hence leading to significantly boosted activity and selectivity for CO2-to-CO photoreduction.

Development of novel mortar using fine river sand and pretreated waste flue gas desulfurization gypsum powder and pond fly ash

The objective of this study is to investigate the potential of combined pond fly ash (PFA) and flue gas desulfurization gypsum (FGDG) as a partial replacement for cement by mixing them with fine river sand for green mortar development. We studied the physical, mechanical, and microstructural properties of mortars by using techniques such as scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDXS) and X-ray diffraction (XRD) for chemical component identification of the hydrated phase. These experimental results show that mortar containing pond fly ash, FGDG, and cement concentrations of 5 wt%, 5 wt%, and 90 wt% yields the maximum compressive strength (8.9 MPa) and flexural strength (3.4 MPa) after 28 days. This mortar has 12.6% higher compressive strength and 48% lower shrinkage in comparison with control specimens. A reduction in shrinkage is attributed to the denser structure of the mortar, as the calcium silicate hydrate (C–S–H) gel is found to exist in the SEM image and also identified through XRD studies. It is also concluded that excessive ettringite formation causes expansion in the volume of mortar, voids formation, and results in the reduction of strength. The application of this mortar can be in the internal plaster, bricks, and masonry.

Thermodynamic and Economic Analysis of a High-efficiency System Integrating ORC Power Generation, CO2 Capture, and CO2 Storage Driven by Complementary LNG Cold Energy and Flue Gas Waste Heat.

Thermodynamic and Economic Analysis of a High-efficiency System Integrating ORC Power Generation, CO2 Capture, and CO2 Storage Driven by Complementary LNG Cold Energy and Flue Gas Waste Heat.

Reforming Natural Gas for CO2 Pre-Combustion Capture in Trinary Cycle Power Plant

Today, most of the world’s electric energy is generated by burning hydrocarbon fuels, which causes significant emissions of harmful substances into the atmosphere by thermal power plants. In world practice, flue gas cleaning systems for removing nitrogen oxides, sulfur, and ash are successfully used at power facilities but reducing carbon dioxide emissions at thermal power plants is still difficult for technical and economic reasons. Thus, the introduction of carbon dioxide capture systems at modern power plants is accompanied by a decrease in net efficiency by 8–12%, which determines the high relevance of developing methods for increasing the energy efficiency of modern environmentally friendly power units. This paper presents the results of the development and study of the process flow charts of binary and trinary combined-cycle gas turbines with minimal emissions of harmful substances into the atmosphere. This research revealed that the net efficiency rate of a binary CCGT with integrated post-combustion technology capture is 39.10%; for a binary CCGT with integrated pre-combustion technology capture it is 40.26%; a trinary CCGT with integrated post-combustion technology capture is 40.35%; and for a trinary combined-cycle gas turbine with integrated pre-combustion technology capture it is 41.62%. The highest efficiency of a trinary CCGT with integrated pre-combustion technology capture is due to a reduction in the energy costs for carbon dioxide capture by 5.67 MW—compared to combined-cycle plants with integrated post-combustion technology capture—as well as an increase in the efficiency of the steam–water circuit of the combined-cycle plant by 3.09% relative to binary cycles.

Oxygen‐Stable Electrochemical CO2 Capture using Redox‐Active Heterocyclic Benzodithiophene Quinone

AbstractElectrochemical carbon capture offers a promising alternative to thermal amine technology, which serves as the traditional benchmark method for CO2 capture. Despite its technological maturity, the widespread deployment of thermal amine technologies is hindered by high energy consumption and sorbent degradation. In contrast, electrochemical methods, with their inherently isothermal operation, address these challenges, offering enhanced energy efficiency and robustness. Among emerging strategies, electrochemical carbon capture systems using redox‐active materials such as quinones stand out for their potential to capture CO2. However, their practical application is currently limited by their low stability in the presence of oxygen. We demonstrate that benzodithiophene quinone (BDT‐Q), a heterocyclic quinone, exhibits high stability in electrochemical carbon capture processes with oxygen‐containing feed gas. Conducted in a cyclic flow system with a simulated flue gas mixture containing 13 % CO2 and 3.5 % O2 for over 100 hours, the process demonstrates high oxygen stability with an electron utilization of 0.83 without significant degradation, indicating a promising approach for real world applications. Our study explores the potential of new heterocyclic quinone compounds in the context of carbon capture technologies.

Oxygen-Stable Electrochemical CO2 Capture using Redox-Active Heterocyclic Benzodithiophene Quinone.

Electrochemical carbon capture offers a promising alternative to thermal amine technology, which serves as the traditional benchmark method for CO2 capture. Despite its technological maturity, the widespread deployment of thermal amine technologies is hindered by high energy consumption and sorbent degradation. In contrast, electrochemical methods, with their inherently isothermal operation, address these challenges, offering enhanced energy efficiency and robustness. Among emerging strategies, electrochemical carbon capture systems using redox-active materials such as quinones stand out for their potential to capture CO2. However, their practical application is currently limited by their low stability in the presence of oxygen. We demonstrate that benzodithiophene quinone (BDT-Q), a heterocyclic quinone, exhibits high stability in electrochemical carbon capture processes with oxygen-containing feed gas. Conducted in a cyclic flow system with a simulated flue gas mixture containing 13 % CO2 and 3.5 % O2 for over 100 hours, the process demonstrates high oxygen stability with an electron utilization of 0.83 without significant degradation, indicating a promising approach for real world applications. Our study explores the potential of new heterocyclic quinone compounds in the context of carbon capture technologies.

Cascade Reactions for Enhanced CO2 Capture: Concurrent Optimization of Porosity and N‐Doping

AbstractCarbon capture emerges as a pivotal decarbonization technology for addressing global warming challenges. Porous carbons, despite their cost‐effectiveness and ease of regeneration for CO2 capture, typically exhibit limited capacity owing to insufficient adsorption sites. Here, nitrogen‐doped porous carbons (NPCs) are introduced that overcome the prevalent trade‐offs between specific surface area and N‐doped content in NPCs fabrication through cascade reactions. The optimized NPC, which features hierarchical porosity ranging from ultra‐micropores to macropores, shows a superior CO2 capture capacity of 4.46 mmol g−1, ranking in the top 10% of the reported NPCs. This capacity exceeds that of the NPC fabricated with the conventional method by 58% and surpasses the control porous carbon by 106%. Langmuir adsorption modeling and mathematic correlation analysis revealed that this enhanced capacity is attributed to significantly improved ultra‐micropores volume and nitrogen‐species content. Moreover, this optimized NPC demonstrates exceptional stability, preserving its adsorption performance over 110 adsorption–desorption cycles under simulated flue gas conditions. This research not only highlights the integration of templating and N‐doping within NPCs fabrication but also offers an effective strategy to optimize porosity and nitrogen functionality in carbon materials, advancing beyond conventional methodologies.

Research on the Propagation Law of Fire Smoke on the Working Face of a Belt Conveyor

In view of the spread and distribution of high-temperature toxic smoke on the working face during belt conveyor fires, the FDS was used to carry out numerical simulation, establish a belt conveyor fire simulation model, set up a variety of working conditions, and study the flue gas spread of the working face with different ignition source locations and different heat release rates. The results show that the flue gas reaching the working face varies greatly from different ignition source locations, and the smoke propagation time of the working face decreases first and then increases with the increase in the scale of the fire. The location of the fire source is from 0 to 700 m, and the visibility of the working face will drop to less than 3 m within 10 min, which seriously affects emergency evacuation; the maximum concentration of CO in the working face is proportional to the heat release rate, the fire source is less than 100 m away from the working face, and the temperature of the air inlet area of the working face is higher than 60 °C, which poses a great threat to personnel evacuation. When the fire source is less than 200 m away from the working face, the evacuees will encounter smoke damage on the working face, and when the fire scale reaches 4 MW and 6 MW, the CO concentration will have a great impact on the evacuation and make people incapacitated.

Improving the method for calculating carbon emissions from waste incineration: confirmed with carbon-14 testing of flue gas

An improved method was developed to calculate direct emissions from seven municipal solid waste incineration plants by adjusting the physical compositions of waste by invoking the proportion of co-incinerated waste and the bottom ash yield. The fossil carbon fractions of the waste components were determined by carbon-14 (14C) testing. Based on the improved method, direct emissions were in the range of 222–610 kg CO2-eq/t waste, corresponding to reductions of 3.4–221 kg CO2-eq/t waste compared with the method without waste composition adjustment. The 14C contents of the flue gas before and after gas cleaning were tested to validate the improved method, and indicated fossil CO2 emissions of 249–446 and 233–405 kg CO2-eq/t waste, respectively. The direct emissions obtained by the improved method were closer to the results of 14C testing, due to more accurate estimations of the actual waste composition. The method was further combined with a life cycle analysis of the waste incineration process, obtaining total carbon emissions in the range from –33.2 to 483 kg CO2-eq/t waste. The findings provide a new means of accurately calculating carbon emissions from waste incineration.Graphical

Ladder-Like Polyphenylsilsesquioxane Membranes for Dissolved Oxygen Removal in Liquid–Liquid Membrane Contactors

The main disadvantage of absorption with aqueous alkanolamine solvents is the solvent degradation under process conditions in the presence of oxygen captured from flue gases. In this communication, the direct dissolved oxygen removal from an amine solvent in liquid–liquid membrane contactors is examined. The membranes from ladder-like polyphenylsilsesquioxanes are used for the first time for this process. The membrane deoxygenation is demonstrated in the O2 removal process from monoethanolamine (MEA) into an aqueous solution of Na2SO3. In this case, the O2 removal efficiency reached up to 40% within 1 h.

Single-Pass Demonstration of Integrated Capture and Catalytic Conversion of CO2 from Simulated Flue Gas to Methanol in a Water-Lean Carbon Capture Solvent

Single-Pass Demonstration of Integrated Capture and Catalytic Conversion of CO₂ from Simulated Flue Gas to Methanol in a Water-Lean Carbon Capture Solvent

Performance Analysis of Cement Plant Waste‐Heat Recovery for Power Generation Based on Partial Evaporating Cycle with Ejector

In the cement industry, much waste heat is released into the environment. The organic Rankine cycle is widely utilized to harness waste heat for power generation. However, significant energy is lost in the heat recovery process due to the finite temperature difference between the heat source and working fluid, resulting in low power output andefficiency. To enhance the heat recovery from the cement flue gas and increase power output and overall efficiency, a novel partial evaporating cycle with ejector is proposed and investigated in this study. Pinch point analysis is performed to characterize the heat recovery process in the evaporator. The effects of the evaporating temperature, outlet quality of the evaporator, and exit pressure of the primary expander on system performance are also investigated. Results show that partially evaporating the fluid improves heat matching and reduces the irreversibilities in the evaporator by up to 18.1% when the outlet quality of the fluid is 0.33. Maximum net power of 803.15 kW can be generated with an evaporating temperature of , outlet quality of 0.33, and expander exit pressure of 1054.9 kPa. Additionally, the inclusion of the ejector increases the net power produced by up to 76.07 kW.

Effect of organic acid additives on sulfite oxidation in a calcium-based slurry

The forced oxidation of sulfite ions was conducted to obtain high-quality gypsum in the flue gas desulfurization system. The effects of formic, lactic, acrylic, acetic, propionic, and hexanoic acids added to calcium-based slurry on sulfite oxidation were investigated in this study. Sulfite oxidation was inhibited when the pKa value of organic acids was small or the carbon chain was long. In the identical slurry pH 6, the SO4 2- fractions of slurries with formic and lactic acids, which have the smallest pKa values, were lower than half that of the additive-free slurry. The addition of hexanoic acid with the longest carbon chain showed a similar SO4 2- fraction to that of additive-free slurry. These results indicate that the inhibitory effect on sulfite oxidation is more expressed by the acidity of organic acids. The SO4 2- fraction in the slurry affects the growth and quality of gypsum crystals. The slurry with acetic acid presented the highest SO4 2- fraction and resulted in the formation of high-quality gypsum crystals. The findings of this study can contribute to the selection of organic acid additives with high desulfurization efficiency and the production of high-quality gypsum.

Enhancing Particle Segregation in Stem Wood Combustion Flue Gas Wet Scrubbers: Experimental Investigation of Operational Conditions

This study investigates the impact of various parameters on particulate-matter (PM) collection from biomass combustion flue gas using a packed-bed wet scrubber. It is important to note that most of the particulate release during biomass combustion is dominated by particle sizes <10 μm(PM10). The experiments studied parameters affecting submicron PM collection efficiency, such as the gas velocity, bed material, and flue gas humidity. The experimental results and analyses focused on the PM10 collection efficiency and provided valuable insights. A higher flue gas velocity reduces the time for the contact between the flue gas and the absorption solution, leading to decreased efficiency. In addition, the findings indicate that a higher flue gas humidity improves the collection efficiency by having a positive effect on the diffusiophoresis force. Testing the packed-bed material confirmed that a wet scrubber half-filled with steel-pall-rings showed a better performance than the same scrubber half-filled with ceramic-Berl-saddles. Furthermore, water was less effective in the absorber than salt solutions since the diffusiophoresis force produced by water acted in the opposite direction to that of the force produced by the salt solutions. The PM released after the wet scrubber absorber is below the EU's established limits for boiler power < 500kW.

Comparison of theoretical methods for describing the heat transfer in vertical tube condensers under conditions corresponding to the condensation of flue gas from a biomass boiler

Abstract A theoretical and experimental study was conducted on water vapor condensation in a vertical tube condenser under conditions corresponding to the condensation of flue gas from biomass boiler where flue gas is considered as a mixture of water vapor and a high content of noncondensable gas (NCG). Four fundamental theoretical methods were identified to determine the heat transfer coefficient and condenser heat output - Empirical correlations, Heat and mass transfer analogy, Diffusion layer theory, Boundary layer theory. These methods were compared with respect to usability in the design of flue gas condensers in energy systems and experimentally verified. Experiments were carried out in a 1.5 m long vertical double-pipe condenser with a condensing gas flowing downward in an inner tube with a diameter of 25 mm. The mass concentration of NCG in a mixture with water vapor ranged from 11 to 86 vol.% and the inlet Reynolds number of the condensing gas ranged from 1936 to 14408, which corresponds with the conditions of condensing flue gas from biomass boilers. The boundary layer theory is very complex and impractical for the calculation of heat exchangers. Empirical correlations have a wide dispersion of the result, because they take into account only the basic parameters of the process. However, Heat and mass transfer analogy and Diffusion layer theory seem to be the most suitable for flue gas condensers since they capture the physical essence of the phenomena.

Improving the removal of fine particles in cyclone using heterogeneous vapor condensation enhanced by atomization

Using a heat exchanger to cool high humidity flue gas can create a supersaturated water vapor environment, allowing fine particles to grow into large droplets by heterogeneous vapor condensation, which is conductive to the removal of fine particles by traditional equipment. However, due to the limited condensable vapor obtained by cooling, this technology can only be used in the flue gas with low particle concentration. In this study, atomization droplets were added before the heat exchanger to improve the effect of heterogeneous vapor condensation at high particle concentration, and then coupled with a cyclone separator, which was used for the deep treatment of the flue gas after the wet dedusting system. The particle removal characteristics were investigated through laboratory experiments and bypass experiments in a metallurgical company. The experimental results show that the application of atomization-heterogeneous condensation reduced the particles concentration after cyclone by 74.2 % compared with that of single heterogeneous condensation. Temperature-drop and atomized volume affected the removal of particles with size < 2 μm and > 2 μm, respectively. The industrial flue gas bypass experiment indicated that the system had strong adaptability to fluctuating conditions. When the inlet particle concentration did not exceed 2000 mg/Nm3, the outlet particle concentration can be maintained within 20 mg/Nm3.

Enhanced SO2 and CO2 synergistic capture with reduced NH3 emissions using multi-stage solvent circulation process

NH3-based SO2 and CO2 synergistic capture technology shows promise in reducing the costs associated with current flue gas desulfurization and CO2 capture systems. However, it faces challenges such as NH3 slip and high energy consumption. In this study, we proposed an advanced Multi-Stage Solvent Circulation (MSC) process that incorporates a desulfurization-washing solution circulation, which involved partitioned absorption according to different functions of SO2 capture, CO2 capture, and NH3 emission control. The experimental results demonstrated that using desulfurization solution in place of water for washing reduced the NH3 emissions from the absorber and desorber by 10.6 % and 7.9 %, respectively. Additionally, the recovered NH3 enhanced SO2 capture, resulting in a 61.8 % decrease in SO2 emission concentration. A pilot-plant trial model for SO2 and CO2 synergistic capture was further developed using Aspen Plus. The impact of operational time and parameters on capture efficiency and energy consumption were analyzed. Under typical flue gas conditions, the process achieved SO2 capture efficiency of > 99 %, regeneration energy consumption of 2.42 GJ/t CO2, NH3 emissions of < 5 ppm. This study presents a novel approach for designing a SO2 and CO2 synergistic capture system, which has the potential to facilitate the economic and effective implementation of post-combustion flue gas pollutant control management and carbon emission reduction.

Suspension-washcoat optimization for preparing copper-manganese oxide structured catalyst towards flue gas CO purification

Structured catalysts play significant role in nowaday environmental industry. The copper-manganese oxide (Cu-Mn) is a low cost and efficient catalyst for CO purification from flue gas, for which a robust preparation regarding stabilized suspension and washcoat process is still lacked. This work addressed this challenge by constructing the catalyst suspension by introducing absorbent polymer (SAP), polyvinyl alcohol (PVA), and nano-silica sol (SiO2-NA). The effects of the dosage of SAP, PVA, and SiO2-NA on suspension properties including viscosity, water-retention capacity and stability were systematically studied. The combined effect of the three additives regarding electrostatic-sterical stability and regionalized coating is demonstrated to avoids the destruction of connection between SiO2-NA and Cu-Mn due to the thermal stress during the drying process. After calcination, SiO2-NA is efficiently utilized, evenly distributed and tightly bonded to Cu-Mn catalyst, rendering strongly-attached, crack-free and compact washcoated layer. The optimized structured catalyst shows appreciable balance of loading (up to 182kg/m3) and strength (powder shedding rate <1wt%) without blockage. The potential of practical application was verified by CO purification from realistic iron-ore sintering flue gas with catalytic efficiency of above 90% for 240h. These findings indicated a promising strategy to design Cu-Mn structured catalysts efficient for industrial use.