Industrial Flue Gas Research Articles

Interface modulation of Mn-N4-C with optimized oxygen-containing functional groups for highly efficient mercury adsorption

To achieve enhanced capture performance of industrial gaseous mercury pollution in heterogeneous reactions, the directed construction of an active reaction interface is particularly critical. Here, we developed atomically dispersed manganese confined within a carbon framework doped with heteroatoms (Mn-N4-C) for strengthening the adsorption of elemental mercury at the interface. The results demonstrate that the adsorption performance of Mn-N4-C is primarily determined by the surrounding coordination environment of individual metal sites. Due to the unique axial-coordination microenvironment, Mn-N4-C with abundant oxygen-containing functional groups (Mn-N4-C(EDA)) exhibits excellent affinity towards elemental mercury, with an adsorption capacity of up to 29.5 mg/g surpassing the most carbon-based materials. Furthermore, it also exhibits excellent tolerance towards various industrial flue gas conditions, performing an adsorption capacity of 16.4 ± 0.2 mg/g within the wide temperature range of 20–200 °C and being promoted by the NO, HCl and H2O, which facilitates practical industrial applications. Theoretical simulations further indicate that the bonding between individual Mn and oxygen sites significantly enhances the mercury adsorption capability of Mn-O-N4 sites, benefiting from the optimization of manganese's electronic structure by oxygen-containing species. Therefore, this study presents a multitude of opportunities for enhancing the adsorption of elemental mercury at interfaces through the directed modulation of metal-oxygen bonds(M-O).

CO2-Rich Gas Conversion to Carbon Nanotube via Molten Salt Electrolysis

The CO2 capture via electrolysis process is a potentially promising and attractive pathway for greenhouse gas removal and global warming reduction by converting CO2 into value-added materials. In this study, the conversion of CO2 from CO2-rich gas into value-added carbon nanomaterial was successfully achieved via molten Li2CO3 electrolysis with a NiCr anode and a stainless steel cathode. The characterization by FESEM and TEM analyses showed that the obtained carbon product was a carbon nanotube with a bamboo-like structure and an outer average diameter of 36 nm. The EDS and XRD characterization indicated the growth of carbon nanotube in electrolysis was achieved through metal nucleation points on the electrolysis cathode. In addition, the Raman analysis showed that the carbon product exhibited high quality and crystallinity. The results from the present study revealed that the molten carbonate electrolysis offered a viable approach for direct transformation of CO2 from industrial flue gas into valuable carbon product, providing an alternative solution to reduce CO2 emissions.

Industrial demonstration of indirect mineral carbonation in the cement and concrete sector

This paper reports on the successful construction, commissioning and operation of a mobile indirect mineral carbonation (IMC) pilot plant in the concrete sector. This work confirms the technical feasibility of IMC at large scale, while producing precipitated calcium carbonate (PCC) and leached recycled concrete aggregate (RCA) as useful products. The plant is capable of handling industrial flue gas or pure CO2 as carbon feedstock, while processing around 80 kg/h of RCA as calcium feedstock, and storing around 0.9 kg/hr of CO2. Good recyclability of the aqueous ammonium nitrate mother liquor is suggested, although small changes occurred over time, with only small effects on the operation. Importantly, some CaCO3 precipitates in the dissolution reactor, especially at high CO2 feed rates; this does not decrease the CO2 storage rate, but it reduces the PCC production rate. The plant may be operated at a variety of operating conditions and it responds to them as expected from thermodynamic considerations. Similarly, the trade-offs in terms of performance parameters also change as expected. The observed calcium extraction efficiency is rather low due to the thermodynamic nature of the batch dissolution step. Also, the ammonium nitrate losses are rather high due to the plant not having a solvent recovery step integrated. Potentially alternative reactor concepts for the dissolution section can improve the calcium extraction efficiency while including a washing step, thus alleviating the main limitation. Material tests with the products of the process suggest that leached RCA is as good as, or even better than fresh RCA for use as aggregate in concrete; ground PCC performs similar as ground limestone in cement, however it is not the most attractive use of fine PCC, as higher value applications exist. Although improvements to the plant design are necessary to make the process economically and environmentally viable, this work represents an important steppingstone towards industrial implementation of IMC, and confirms its technical feasibility in the concrete sector.

Effect of additives on sulfur resistance of catalytic filter material during denitrification and synergistic decomposition of 1,2-DCBz.

Modified Mn-Ce/P84 catalytic filter material can be used to achieve high removal efficiency of NOx and 1,2-DCBz in bag-filtering dust precipitator synergistic removal of multiple pollutants. However, the presence of SO2 in the actual industrial flue gas has an adverse impact on the catalytic performance of the catalytic filter material. In this paper, a kind of Mn-Ce catalytic filter material was prepared by the impregnation method, which was modified by Fe, Cu, and Co, respectively. As a result, the sulfur resistance of the catalytic filter material was improved. The change of catalytic activity of the three kinds of modified catalytic filter material at different concentrations was compared in the SO2 flue gas fixed bed system. And the modified catalytic filter materials were characterized by SEM, BET, XPS, XRD, and H2-TPR. When the temperature was over 80 °C, different concentrations of SO2 were injected into the simulated flue gas to test the denitrification activity of the catalytic filter material. The results showed that under the low SO2 concentration of 150 ppm, the denitrification activity and 1,2-DCBz activity of Fe, Co, and Cu-modified filter material were increased, and the sulfur resistance of Fe was better under the flue gas conditions of 300 ppm and 450 ppm SO2. Under the condition of 450 ppm SO2 and 200 °C reaction, 93.4% denitrification efficiency and 96.1% 1,2-DCBz removal efficiency could be achieved by using modified Fe-Mn-Ce catalytic filter material.

Oxidation of CO and slipped NH3 over a WS2-Loaded Pt/TiO2 catalyst with an extended reaction temperature range

The recent tightening of emission regulations aims to reduce the release of CO and slipped NH3 with industrial flue gas, necessitating the development of improved CO and NH3 oxidation catalysts, as conventional Pt catalysts are easily poisoned by the SO2 present in flue gas. In particular, the reaction temperature range of existing Pt/TiO2 catalysts and their resistance to sulfur poisoning can be improved by enhancing Pt dispersion through modification with WS2. This study examined the ability of WS2-doped Pt/TiO2 catalysts prepared using different WS2 loadings (3.6 and 5 wt%) at various calcination temperatures (300, 400, and 500 °C) to promote the oxidation of CO and NH3 in the absence and presence of SO2. The partial conversion of WS2 to WO3 at high calcination temperatures is found to be of key importance for securing high catalyst performance. The optimal catalyst exhibits high oxidation activity and sulfur resistance at low temperatures, achieving CO and NH3 oxidation efficiencies of ≥85% and 100%, respectively, at an SO2 content of 100 ppm and 280 °C.

Carbon dioxide capture with aqueous calcium carbide residual solution for calcium carbonate synthesis and its use as an epoxy resin filler

Calcium carbide residue (CCR) is a waste obtained from the production of acetylene gas by the hydration reaction of calcium carbide. This residue is generated in large quantities annually and requires appropriate disposal. The main composition of the residue is calcium hydroxide (Ca(OH)2). Ca(OH)2 can react with CO2 gas and form CaCO3 particles. This process is well known but not very attractive since Ca(OH)2 is obtained from limestone using an energy-intensive thermal conversion process. This paper examined the synthesis of CaCO3 from CCR solutions by capturing CO2 with the aid of triethanolamine (TEA) solutions at doses of 0, 5, 10 and 20% w/w. The precipitated CaCO3 was characterized, and the application of CaCO3 as a filler in epoxy resin was tested. The results showed that the precipitated CaCO3 was mainly calcite, with a 76.6% yield. Cubic calcite was primarily obtained in TEA solutions, whereas small and agglomerated spherical vaterite and cubic calcite particles were formed in non-TEA solutions. The CaCO3-filled epoxy composites showed higher compressive strength than the neat resin. However, the transparency of specimen plates was reduced. These results can serve as guidelines for the application of CCR slurry filtrate obtained from the sedimentation ponds of acetylene plants and help to reduce the amount of wastewater that needs to be treated. CO2 gas from industrial flue gas combined with TEA solution could be applied to precipitate CaCO3 for carbon-neutral manufacturing.

Synergy of copper vacancies and amorphous regions in copper sulfides enables superior capacity for Hg0 adsorption

Adsorption is a high-efficiency and low-cost approach to control elemental mercury emission from industrial flue gas. However, the adsorption capacity is unsatisfactory due to its surface-only adsorption. In this work, a facile method was used for preparing the crystalline-amorphous co-existed copper sulfides (CA-CuS) with an abundance of copper vacancies and amorphous regions through temperature-controlled ultrasonic cavitation. The CA-CuS was used in the flue gas wet scrubbing and displayed outstanding Hg0 capture performance, achieving a removal efficiency of 99.8% and an adsorption capacity up to 573.8 mg·g-1 with a sulfur atomic utilization ratio of 27.5%. Experimental results and density functional theory (DFT) calculation verified that the copper vacancies at di-coordinated sites led to the formation of robust mercury binding sites (i.e., S2-(CN=3)) and unsaturated coordinated oxidizing sites (i.e., S22-). Meanwhile, the amorphous regions facilitated the internal migration of adsorbed mercury on the surface and promote the exchange with Cu2+ in the interior of adsorbents. The synergistic effect of copper vacancies and amorphous regions enables superior mercury adsorption capability and high atomic utilization.

Interactive adsorption mechanism and product distribution of impurity gases on CO2 adsorption over amine-grafted ZSM-5/SBA-16 adsorbent

Solid amine adsorbents hold promising application prospects in the realm of industrial flue gas decarbonization. Nevertheless, there remains a need for substantial improvement in the cycling stability of solid amine adsorbents. Additionally, the competitive adsorption mechanism of solid amine adsorbents pertaining to flue gas components lacks thorough verification. In this study, amine-grafted micro-mesoporous ZSM-5/SBA-16 adsorbents were synthesized to improve the CO2 adsorption capacity and investigate the effect of impurity gases on CO2 adsorption. Various characterization techniques, including X-ray diffraction (XRD), thermogravimetric analysis (TGA), N2 adsorption, and elemental analysis, were employed to analyze the properties of the adsorbents. The loading analysis of the micro-mesoporous molecular sieve revealed that ZS-A-2.0 exhibited the highest CO2 adsorption capacity of 41.39 mg/g. Mass spectrometry was utilized to evaluate the co-adsorption experimentation involving multicomponent gases. The breakthrough curves of CO2 displayed dual stages at low concentrations, suggesting the simultaneous occurrence of physical and chemical adsorption throughout the entire adsorption process. Based on temperature programming desorption (TPD) and in situ Fourier transform infrared spectroscopy (FTIR), the results indicated a notable enhancement in CO2 adsorption due to the presence of H2O. Conversely, the presence of SO2 and NO exhibited adverse effects on CO2 adsorption, consequently hindering the formation of carbamate and (RNH3)2CO3 adsorption products. This study presents, for the first time, a comprehensive investigation into the interactive adsorption mechanism and product distribution between CO2 and impurity gases. The findings presented herein provide valuable insights and essential support for practical flue gas applications.

Renewable Methanol from Industrial Carbon Emissions: A Dead End or Sustainable Way Forward?

As the urgency to achieve net-zero emissions by 2050 intensifies, industries face an imperative to reimagine their role in the fight against climate change. One promising avenue arises from the realization that industrial emissions, often deemed pollutants, can be the building blocks of a circular economy strategy. By directly utilizing these carbon emissions as raw materials, we can produce net-zero or low-carbon fuels, carbonates, polymers, and chemicals. At the heart of this paradigm shift lies the production of carbon-neutral methanol from industrial flue gas-a technically viable approach that has gained significant momentum in recent years. The conditions under which such a circular economy model for producing renewable methanol becomes commercially sustainable based on realistic constraints, however, are not sufficiently explored in the existing literature. This paper fills this gap by investigating if and when net-zero methanol production from industrial flue gas will be a sustainable long-term strategy. Using detailed technoeconomic modeling of integrated hydrogen and methanol production ecosystems for two production capacities, I will evaluate 32 practical production scenarios using realistic regulatory, economic, and market conditions. Even though renewable methanol from industrial emissions can be a viable technical solution to address climate change and global warming, I will show why this strategy will be commercially feasible only under favorable economic, regulatory, and market conditions. Furthermore, I will demonstrate how the market price of methanol and the cost of carbon-free electricity critically influence the commercial feasibility of this approach. When these two parameters are unfavorable, I will show why other factors, namely, carbon credits and byproduct (oxygen) sales, will not be sufficient to create an economically sustainable circular economy of renewable methanol from industrial emissions. Finally, I will provide arguments on why one has to think through stakeholder cooperation and public-private partnerships to mitigate various project risks. Despite the importance of this topic, it is not sufficiently covered in the available scientific literature. To advance policy and regulatory frameworks in this area, I strongly believe that further research and development is needed. I will also share perspectives on regulatory derisking mechanisms, which can help align regulations with private investors' preferences. With the analyses and arguments showcased in this paper, I will firmly assert that without favorable conditions, strong partnerships, and stakeholder cooperation, the production of renewable net-zero methanol from industrial emissions risks becoming a dead-end strategy.

Degradation of o-dichlorobenzene by DBD-NTP co-modified titanium gel catalyst

In order to study the degradation process of dioxins in industrial flue gas, the decomposition of o-dichlorobenzene (o-DCB) in a DBD plasma catalytic reactor was investigated. The results showed that an NTP-catalyzed system, especially using the CuMnTiOx catalyst, had better o-DCB degradation performance compared to plasma alone. The combination of the CuMnTiOx catalyst with NTP can achieve a degradation efficiency of up to 97.2% for o-DCB; the selectivity of CO and CO2 and the carbon balance were 40%, 45%, and 85%, respectively. The dielectric constant and electrical property results indicated that the surface discharge capacity of the catalysts played a major role in the degradation of o-DCB, and a higher dielectric constant could suppress the plasma expansion and enhance the duration of the plasma discharge per discharge cycle. According to the O1s XPS and O2-TPD results, the conversion of CO to CO2 follows the M-v-K mechanism; thus, the active species on the catalyst surface play an important role. Moreover, the CuMnTiOx and NTP mixed system exhibited excellent stability, which is probably because Cu doping improved the lifetime of the catalyst. This work can provide an experimental and theoretical basis for research in the degradation of o-DCB by plasma catalyst systems.

Limestone hydrogenation combined with reverse water–gas shift reaction under fluidized and iso-thermal conditions using MFB-TGA-MS

The integrated CO2 capture and utilization (ICCU) in conjunction with the reverse water–gas shift (RWGS) reaction has emerged as a promising approach to achieve carbon neutrality. However, the scalability of CaCO3 hydrogenation in the context of large volumes of industrial flue gas is impeded by the limited understanding of its performance under fluidized and iso-thermal conditions. This study utilized micro-fluidized bed thermogravimetric analysis coupled with mass spectrometry (MFB-TGA-MS) and in-situ measurements to investigate limestone decomposition under H2 and Ar atmospheres. Results showed that H2 atmosphere increased the limestone decomposition rate by 5-fold (79.1% CO2 conversion and ∼100% CO selectivity at 710 °C) compared to Ar, with RWGS as the dominant route and self-catalytic activity of calcined CaO. Morphology evolution revealed finer pores and textures under H2 conditions. Meanwhile, apparent kinetic models analyzed experimental data and showed a reduction in activation energy from 178.5 kJ/mol (Ar) to 161.3 kJ/mol (H2). These findings support the effectiveness of ICCU-RWGS approaches for further commercialization.

Sulfur Dioxide Promoted Mercury Fast Deposition over a Selenite-Chloride-Induced Surface from Wet Flue Gas.

Gaseous elemental mercury (Hg0) extraction from industrial flue gases is undergoing intense research due to its unique properties. Selective adsorption that renders Hg0 to HgO or HgS over metal oxide- or sulfide-based sorbents is a promising method, yet the sorbents are easily poisoned by sulfur dioxide (SO2) and H2O vapor. The Se-Cl intermediate derived from SeO2 and HCl driven by SO2 has been demonstrated to stabilize Hg0. Thus, a surface-induced method was put forward when using γ-Al2O3 supported selenite-chloride (xSeO32--yCl-, named xSe-yCl) for mercury deposition. Results confirmed that under 3000 ppm SO2 and 4% H2O, Se-2Cl exhibited the highest induced adsorption performance at 160 °C and higher humidity can accelerate the induction process. Driven by SO2 under the wet interface, the in situ generated active Se0 has high affinity toward Hg0, and the introduction of Cl- enabled the fast-trapping and stabilization of Hg0 due to its intercalation in the HgSe product. Additionally, the long-time scale-up experiment showed a gradient color change of the Se-2Cl-induced surface, which maintained almost 100% Hg0 removal efficiency over 180 h with a normalized adsorption capacity of 157.26 mg/g. This surface-induced method has the potential for practical application and offers a guideline for reversing the negative effect of SO2 on gaseous pollutant removal.

A Review of the Recent Advancement of Bioconversion of Carbon Dioxide to Added Value Products: A State of the Art

Excessive dependence on fossil fuels increases GHG emissions and carbon levels in the atmosphere, leading to climatic changes. This phenomenon can be reversed by capturing the carbon via “carbon capture and storage” (CCS) or “carbon capture and utilize” (CCU) technologies. In CCS methods, the captured carbon is stored in natural sinks (e.g., oceans), whereas, in CCU methods, the carbon is converted into useful products. Among CCU methods, the biological conversion of CO2 (BioConCO2) into value-added chemicals has gained great attention. This review focuses on providing an overview of the recent advances in CO2 utilization technology with a focus on the BioConCO2. The theoretical background and technical drivers, challenges, and setbacks of upscaling and commercialization of BioConCO2 are critically discussed with implications for future improvements. The BioConCO2 is increasingly attracting the attention of researchers and industrialists for its capacity to operate under low CO2 concentrations and in the presence of impurities (common conditions in industrial flue gases)—among other numerous advantages. While upscaling algae-based BioConCO2 has operational and financial challenges, bioconversion via bacteria and genetically engineered cyanobacterial seems promising due to their efficiency and flexibility.

Integrated capture and solar-driven utilization of CO2 from flue gas and air

Integrated capture and solar-driven utilization of CO2 from flue gas and air

REDUCTION OF OCCUPATIONAL RISKS FOR THE HEALTH OF WORKERS AND IMPROVEMENT OF ECOLOGICAL SAFETY OF THE ENVIRONMENT DURING CLEANING OF INDUSTRIAL EMISSIONS OF METALLURGICAL ENTERPRISES

Purpose: prevention of occupational risks and reduction of the negative impact on the health of workers of industrial flue gases, along with the improvement of environmental safety thanks to mathematical modeling regarding the rationalization of technological indicators of sulfur removal at production enterprises. Design / methodology / approach: the use of regression analysis is implemented as the main research method. Conclusions: a multifactorial mathematical model of the dependence of the degree of reduction of the content of sulfur dioxide in gaseous products on the technological parameters of flue gas filtration was built using industrial data. This makes it possible to rationalize the technological parameters of production with further regulation of the sulfur dioxide purification process to increase its efficiency. Achieving a reduction in flue gas pollution with sulfur dioxide contributes to reducing the harmful effects on the health of workers, preventing occupational risks, and increasing the level of environmental safety. Limitations / implications of the research: the interrelationship of desulfurization production parameters was investigated in certain intervals according to the features of the technological process, which determines the corresponding limitations of the use of the constructed mathematical model. Practical consequences: the interrelationship of technological indicators of industrial production is determined, which allows adjusting the value of the degree of purification of flue gases from sulfur dioxide when changing the technological parameters of filtration with the establishment of the most favorable conditions. The obtained results can be used to improve the production process of enterprises whose activities are accompanied by gaseous emissions: metallurgical plants, thermal power plants, etc. Originality / value: a multifactorial mathematical model of the dependence of the degree of purification of flue gases from sulfur dioxide on the technological parameters of the industrial process was built. The obtained results were presented in the form of a multivariate regression equation. On the basis of the obtained dependence, for a better visual perception, graphs were constructed in the form of surfaces, respectively, for some of the studied technological parameters.

Numerical analysis of SO2 removal characteristics in industrial flue gas desulfurization reactor by spray drying adsorption

The flue gas desulfurization reactor by spray drying adsorption plays a crucial role in the process of gas purification. This study employed the multi-phase particle-in-cell method to accurately model the three-dimensional motion of particles of different sizes in the flue gas desulfurization reactor. The double-film theory was utilized to simulate the heat and mass transfer processes of desulfurization slurry droplets. Additionally, this study conducted a comprehensive analysis of various factors affecting gas-solid flow and mass transfer processes, including flue gas inlet velocity and temperature, Ca/S molar ratio, slurry particle size, and slurry temperature. The results demonstrate that the simulated and experimental results are in good agreement, validating the reliability of the developed model. The axial mass fluxes of gas and particles exhibit contrasting distributions in the central part and near the wall, with the turbulent viscosity being particularly pronounced in the top nozzle region. The inlet velocity of flue gas has a limited effect on the axial mass flux of particles, whereas the Ca/S molar ratio exerts a more significant influence. Furthermore, the Ca/S molar ratio has a substantial impact on the spatial distribution of flue gas temperature. The inlet velocity of flue gas and slurry particle size are negatively and positively correlated with particle residence time, respectively. Based on the mass transfer characteristics, the reactor interior can be divided into three zones: a high-efficiency desulfurization zone, a low-efficiency desulfurization zone, and a partial desulfurization zone. For the investigated operating conditions, the desulfurization efficiency is most strongly influenced by the slurry particle size, followed by the flue gas inlet velocity, Ca/S molar ratio, flue gas inlet temperature, and slurry temperature.

Effect of isopropanol on CO2 capture by activated carbon: Adsorption performance and regeneration capacity

Globally, fossil fuel combustion from various industrial processes has caused a significant increase in CO2 emissions, exacerbating the greenhouse effect and climate change. Therefore, effective CO2 capture technologies must be urgently developed. Vacuum temperature swing adsorption (VTSA) is an efficient technique for CO2 capture. The presence of water vapor, H2S, etc., is an important factor that affects the performance of CO2 adsorption, and they are usually removed prior to the adsorption separation process. However, volatile organic compounds (VOCs), a common component of industrial flue gas, can also affect the adsorption and capture of CO2, which is often ignored. Thus, in this study, the effect of isopropanol (IPA), one of the most common VOCs used in industry, on the CO2 removal performance is examined using an in-house VTSA device with activated carbon (AC) as the adsorbent. The effect of IPA on the CO2 adsorption performance of AC under varying IPA concentration, IPA content in AC, feed flow rate, and adsorption/desorption temperature is comprehensively investigated. The results verify that the impact of VOCs in the industrial exhaust gases on CO2 capture by adsorption cannot be disregarded.

Dynamic Modeling of Flue Gas Desulfurization Process via Bivariate EMD-Based Temporal Convolutional Network

Sulfur dioxide (SO2) can cause detrimental impacts on the ecosystem. It is well known that coal-fired power plants play a dominant role in SO2 emissions, and consequently industrial flue gas desulfurization (IFGD) systems are widely used in coal-fired power plants. To remove SO2 effectively such that ultra-low emission standard can be satisfied, IFGD modeling has become urgently necessary. IFGD is a chemical process with long-term dependencies between time steps, and it typically exhibits strong non-linear behavior. Furthermore, the process is rendered non-stationary due to frequent changes in boiler loads. The above-mentioned properties make IFGD process modeling a truly formidable problem, since the chosen model should have the capability of learning long-term dependencies, non-linear dynamics and non-stationary processes simultaneously. Previous research in this area fails to take all the above points into account at a time, and this calls for a novel modeling approach so that satisfactory modeling performance can be achieved. In this work, a novel bivariate empirical mode decomposition (BEMD)-based temporal convolutional network (TCN) approach is proposed. In our approach, BEMD is employed to generate relatively stationary processes, while TCN, which possesses long-term memory ability and uses dilated causal convolutions, serves to model each subprocess. Our method was validated using the operating data from the desulfurization system of a coal-fired power station in China. Simulation results show that our approach yields desirable performance, which demonstrates its effectiveness in the IFGD dynamic modeling problem.

Unveiling the temperature-dependent effect of Zn on phosphotungstic acid-modified MnOx catalyst for selective catalytic reduction of NOx: A poison at < 180 °C or a promoter at > 180 °C

MnOx-based catalysts are highly efficient for selective catalytic reduction (SCR) of NOx with NH3 at low temperatures, but Zn contained in industrial flue gas may poison conventional SCR catalysts, and MnOx-based catalysts usually have low Zn tolerance. Herein, phosphotungstic acid-modified MnOx (denoted as Mn-HPW) was prepared to study the Zn tolerance. It was found that the deposition of Zn on Mn-HPW decreases the SCR activity at < 180 °C, but both NOx conversion and N2 selectivity are enhanced at 180–300 °C, and > 95% NOx conversion can be achieved on Zn/Mn-HPW. Relevant catalysts were characterized and the results reveal that the decline in the activity at < 180 °C is related to the decrease in the quantities of Mn4+, Mn3+, and chemisorbed oxygen as well as the decreased capacities for adsorbing and activating NH3 and NOx. The unusual improvement of SCR performance on Zn/Mn-HPW at 180–300 °C is mainly attributed to two aspects: (i) HPW can protect effectively the surface acid sites from Zn poisoning; (ii) The decrease in oxidation properties alleviates the over-oxidation of NH3, promoting the participation of more NH3 in SCR.

Integration of membrane contactors and catalytic solvent regeneration for efficient carbon dioxide capture

To develop an energy-efficient and available carbon dioxide (CO2) capture technique with amine-based solvents and membrane contactors (MCs), an innovative technological route was proposed to remove CO2 from industrial flue gas by coupling MCs with catalyst-aided solvent regeneration (MC-CR). A laboratory-scale experimental setup with ceramic membrane module was then designed and built to accurately estimate the performance of the MC-CR route, using aqueous monoethanolamine (MEA) and powder metatitanic acid [TiO(OH)2] as the solvent and catalyst, respectively. The results indicated that the nanofluid effect of the catalyst reduced the mass transfer resistance and promoted a concentration change in the liquid film, resulting in a high CO2 absorption rate.The surface acidic sites of TiO(OH)2 boosted the process of proton transfer in the solvent, thus facilitating the decomposition of carbamate. The CO2 capture efficiency increased by 9.48% and the energy consumption of solvent regeneration considerably decreased by 40.8% at dosage of 2 wt% TiO(OH)2. In addition, matched pressure regulation for gas–liquid flow in the MCs effectively avoided membrane fouling and wetting after 180 min continuous operation. Industrial-scale simulation indicated that the MC-CR route achieved a low capture cost at $46.7/t CO2, a decrease of 28% compared with the cost of the traditional route. This study established the groundwork for developing MC technology as an effective approach for low-cost industrial CO2 capture.