A prospective life cycle assessment was performed for global ammonia production across 26 regions from 2020 to 2050. The analysis was based on the IEA Ammonia Roadmap and IMAGE electricity scenarios model for three climate scenarios related to a mean surface temperature increase of 3.5 °C, 2.0 °C, and 1.5 °C by 2100. Combining these models with a global perspective and new life cycle inventories improves ammonia's robustness, quality, and applicability in prospective life cycle assessments. It reveals that complete decarbonisation of the ammonia industry by 2050 is unlikely from a life cycle perspective because of residual emissions in the supply chain, even in the most ambitious scenario. However, strong policies in the 1.5 °C scenario could significantly reduce climate impacts by up to 70% per kilogram of ammonia. The cumulative greenhouse gas emissions from the ammonia supply chain between 2020 and 2050 are estimated at 24, 21, and 15 gigatonnes CO₂-equivalent for the 3.5 °C, 2.0 °C, and 1.5 °C scenarios, respectively. The paper examines challenges in achieving these scenarios, noting that electrolysis-based (yellow) ammonia, contingent on electricity decarbonisation, offers a cleaner production pathway. However, achieving significant GHG reductions is complex, requiring advancements in technologies with lower readiness, like carbon capture and storage and methane pyrolysis. The study also discusses limitations such as the need to reduce urea demand, potential growth in ammonia as a fuel, reliance on CO₂ transport and storage, expansion of renewable energy, raw material scarcity, and the longevity of existing plants. It highlights potential shifts in environmental impacts, such as increased land, metal, and mineral use in scenarios with growing renewable electricity and bioenergy with carbon capture and storage.

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In this study, the effect of halide anions on the selectivity of the CO₂ reduction reaction to CO was investigated in choline-based ethylene glycol solutions containing different halides (ChCl : EG, ChBr : EG, ChI : EG). The CO₂RR was studied using silver (Ag) and gold (Au) electrodes in a compact H-cell. Our findings reveal that chloride effectively suppresses the hydrogen evolution reaction and enhances the selectivity of carbon monoxide production on both Ag and Au electrodes, with relatively high selectivity values of 84 % and 62 %, respectively. Additionally, the effect of varying ethylene glycol content in the choline chloride-containing electrolyte (ChCl : EG 1 : X, X=2, 3, 4) was investigated to improve the current density during CO₂RR on the Ag electrode. We observed that a mole ratio of 1 : 4 exhibited the highest current density with a comparable faradaic efficiency toward CO. Notably, an evident surface reconstruction process took place on the Ag surface in the presence of Cl⁻ ions, whereas on Au, this phenomenon was less pronounced. Overall, this study provides new insights into anion-induced surface restructuring of Ag and Au electrodes during CO₂RR, and its consequences on the reduction performance on such surfaces in non-aqueous electrolytes.

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Electrochemical CO₂ reduction in non-aqueous solvents is promising due to the increased CO₂ solubility of organic-based electrolytes compared to aqueous electrolytes. Here the effect of nine different salts in propylene carbonate (PC) on the CO₂ reduction product distribution of polycrystalline Cu is investigated. Three different cations (tetraethylammonium (TEA), tetrabutylammonium (TBA), and tetrahexylammonium (THA)) and three different anions (chloride (Cl), tetrafluoroborate (BF₄), and hexafluorophosphate (PF₆)) were used. Chronoamperometry and in-situ FTIR measurements show that the size of the cation has a crucial role in the selectivity. A more hydrophobic surface is obtained when employing a larger cation with a weaker hydration shell. This stabilizes the CO₂⁻ radical and promotes the formation of ethylene. CO₂ reduction in 0.7 M THACl/PC shows the highest hydrocarbon formation. Lastly, we hypothesize that the hydrocarbon formation pathway is not through C−C coupling, as the CO solubility in PC is very high, but through the dimerization of the COH intermediate.

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Electrolytic bicarbonate conversion holds the promise to integrate carbon capture directly with electrochemical conversion. Most research has focused on improving the faradaic efficiencies of the system, however, the stability of the system has not been thoroughly addressed. Here, we find that the bulk electrolyte pH has a large effect on the selectivity, where a higher pH results in a lower selectivity. However, the bulk electrolyte pH has no effect on the stability of the system. A decrease in CO selectivity of 30 % was observed within the first three hours of operation in an optimized system with 3 M KHCO₃ and gap between the membrane and electrode. Single-pass electrolyte experiments at various constant pH values (8.5, 9.0, 9.5, and 10.0), show that only at a pH of 10 the CO selectivity was stable during three hours, reaching a faradaic efficiency toward CO of only 18 % as compared to an initial 55 % at pH 8.5. Trace metal impurities present in the electrolyte were found to be the cause of the decrease in stability as these deposit on the electrode surface. By complexing the trace metal ions with ethylenediaminetetraacetic acid (EDTA), the metal deposition was avoided and a stable CO selectivity was obtained.

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Carbon capture and utilization (CCU) plays a key role in reducing greenhouse gas emissions and reaching carbon neutrality goals. This study assesses the environmental impacts of producing carbon nanotubes (CNTs) via molten salt CO2 capture and electrochemical transformation (MSCC-ET) and Catalytic Chemical Vapor Deposition (CCVD), both using CO2 as feedstock. We screened and selected technologies using a parameter-based method and conducted process modeling and an ex-ante Life Cycle Assessment (LCA) to move beyond lab-scale evaluations and included the purification steps. The MSCC-ET approach showed advantages in reducing impacts related to climate change, energy, and ozone depletion impacts, specifically suggesting lower CO2 emissions. However, traditional CCVD outperformed MSCC-ET in several other impact categories. Key contributors to the environmental impacts of MSCC-ET were found in high material use in electrolysis, purification, and electricity consumption, modeled using the Belgium grid. Moreover, including the carbon capture unit in the assessment could provide a complete view of the environmental impacts regarding CCU. For every 100 tons of MWCNTs produced, a monoethanolamine (MEA)-based carbon capture unit integrated into the MSCC-ET system could roughly reduce 716.5 tons CO2-eq. Additionally, electricity consumption was found to constitute a significant portion of the environmental impacts. Therefore, a sensitivity analysis was conducted, revealing that changes in the electricity source, catalyst used, and CO2 source significantly influenced the environmental performance of both technologies. Furthermore, we summarize practical insights from this study to guide the effective application of ex-ante LCA for carbon nanomaterials. The paper concludes with actionable recommendations for early-stage technology developers on optimizing energy use, improving material efficiency, and integrating recycling to enhance sustainability. In addition, we provide recommendations for LCA practitioners on incorporating dynamic systems to transition from lab-scale to industrial contexts, thereby bridging the gap between research and practical implementation.@en

Aqueous electrolytes are most commonly used for the CO₂ reduction reaction (CO₂RR), but suffer from a low CO₂ solubility that limits the reaction. Electrochemical CO₂ reduction in nonaqueous electrolytes can provide a solution, due to the higher CO₂ solubility of organic solvent-based electrolytes. Herein, the product distribution of the electrochemical CO₂ reduction on polycrystalline Cu in 0.7 m tetraethylammonium chloride in propylene carbonate with different water additions (0, 10, and 90 v%), and for different operating conditions (10, 25, 40, and 60 °C), is investigated. It is found that CO₂ reduction on Cu in a propylene carbonate solution results in H₂, CO, and formic acid formation only, even though Cu is known to produce C₂₊ products such as ethylene and ethanol in aqueous electrolytes. Increasing the operating temperature increases the CO₂RR kinetics and shows an improvement in CO formation and decrease in H₂ formation. However, increasing the operating temperature also increases water transport through the membrane, resulting in an increase of H₂ formation over time when operating at 60 °C.

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The International Maritime Organization has set clear objectives towards drastically reducing greenhouse gas emissions the coming decades in the maritime sector. While different ways to reduce emissions are already proposed, these are not expected to generate high CO₂ abatement rates (in the case of fuel saving measures) or to be available and cost competitive in the near future (in the case of alternative fuels). Alternatively, ship-based carbon capture (SBCC) technology could be implemented on the shorter term and has the potential to drastically reduce the CO₂ emissions of the maritime sector. This study discusses the advancements made towards the SBCC technology on board of LNG-fuelled ships using the results of the DerisCO2 project. The study covers general design considerations for the SBCC technology (solvent selection, heat integration and effect of ship movement), next to specific design considerations for the Sleipnir ship of Heerema Marine Contractors (analysis of operational profile, conceptual design and high level integration of the SBCC system), which is used as a case study for SBCC in this paper. Simulation of the SBCC technology including a techno-economic analysis on the case studies are included. The SBCC technology is a technically and economically viable solution for the maritime sector to reduce emissions the coming decades, with the cost of CO₂ capture for the Sleipnir calculated between 119-133 €/ton CO₂. The most important proposed next step for fast development of the SBCC system is on board demonstration of the technology.

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We performed H-cell and flow cell experiments to study the electrochemical reduction of CO2 to oxalic acid (OA) on a lead (Pb) cathode in various nonaqueous solvents. The effects of anolyte, catholyte, supporting electrolyte, temperature, water content, and cathode potential on the Faraday efficiency (FE), current density (CD), and product concentration were investigated. We show that a high FE for OA can be achieved (up to 90%) at a cathode potential of -2.5 V vs Ag/AgCl but at relatively low CDs (10-20 mA/cm2). The FE of OA decreases significantly with increasing water content of the catholyte, which causes byproduct formation (e.g., formate, glycolic acid, and glyoxylic acid). A process design and techno-economic evaluation of the electrochemical conversion of CO2 to OA is presented. The results show that the electrochemical route for OA production can compete with the fossil-fuel based route for the base case scenario (CD of 100 mA/cm2, OA FE of 80%, cell voltage of 4 V, electrolyzer CAPEX of $20000/m2, electricity price of $30/MWh, and OA price of $1000/ton). A sensitivity analysis shows that the market price of OA has a huge influence on the economics. A market price of at least $700/ton is required to have a positive net present value and a payback time of less than 10 years. The performance and economics of the process can be further improved by increasing the CD and FE of OA by using gas diffusion electrodes and eliminating water from the cathode, lowering the cell voltage by increasing the conductivity of the electrolyte solutions, and developing better OA separation methods.

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Logistics of hydrogen is one of the bottlenecks of a hydrogen economy. In this study, a pressure swing adsorption (PSA) system is proposed for the separation of hydrogen from natural gas, co-transported in the natural gas grid. The economic feasibility of hydrogen supplied by a PSA system at a refuelling station is assessed and compared with other alternatives. The adsorbent material is key to the design of a PSA system, which determines the operation performance and cost. It is concluded that a refuelling station with hydrogen supplied by a PSA system is economically feasible. The final hydrogen price including hydrogen supply, compression, storage, and dispensing is compared with two other hydrogen supply methods: on-site electrolysis and tube-trailer transported hydrogen. Currently, PSA supplied hydrogen is a more economical option. On-site electrolysis can become a more economical option in the future with improved cell efficiencies and reduced electricity prices. Tube-trailer transported hydrogen is highly influenced by the distance travelled. The findings of this study will help with more efficient distribution of hydrogen.

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The concept of liquid metal membranes for hydrogen separation, based on gallium or indium, was recently introduced as an alternative to conventional palladium-based membranes. The potential of this class of gas separation materials was mainly attributed to the promise of higher hydrogen diffusivity. The postulated improvements are only beneficial to the flux if diffusion through the membrane is the rate-determining step in the permeation sequence. Whilst this is a valid assumption for hydrogen transport through palladium-based membranes, the relatively low adsorption energy of hydrogen on both liquid metals suggests that other phenomena may be relevant. In the current study, a microkinetic modeling approach is used to enable simulations based on a five-step permeation mechanism. The calculation results show that for the liquid metal membranes, the flux is limited by the dissociative adsorption over a large temperature range, and that the membrane flux is expected to be orders of magnitude lower compared to the membrane flux through pure palladium membranes. Even when accounting for the lower cost of the liquid metals compared to palladium, the latter still outperforms both gallium and indium in all realistic scenarios, in part due to the practical difficulties associated with making liquid metal thin films.

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This chapter presents discussion of four selected case studies for sustainable carbon capture. The first case study is a high-level techno-economic integration study for CO2 capture in the waste to energy (WtE) sector, which may result in negative emissions, as a large part of the CO2 is biogenic. Integration of CO2 capture in this sector is essential when the need for district heating is low and/or heat is available at a relatively low price. The second case study describes a groundbreaking techno-economic integration study for CO2 capture on board ships, also called ship-based carbon capture (SBCC). The study considers the operational profile of the ship and uses the available heat integration options to minimize the costs of the process. The third case study entails the techno-economic evaluation of integrating carbon dioxide capture with a biogas facility for biogas upgrading to biomethane. The integrated cycle offers carbon-neutral energy with the potential for negative emissions by storing carbon dioxide underground. The final case study is related to the carbon capture applications in the cement and iron/steel sector. This Page is compulsory Book Title – Sustainable Carbon Capture: Technologies and Applications Chapter Author(s) Jasper A. Ros, TNO, The Netherlands, jasper.ros@tno.nl Juliana G.M-S. Monteiro, TNO, The Netherlands, Juliana.monteiro@tno.nl Earl L.V. Goetheer, TNO, The Netherlands, earl.goetheer@tno.nl Randi Neerup, Center for Energy Resources Engineering (CERE), Department of Chemical and Biochemical Engineering, Technical University of Denmark (DTU), Søltofts Plads 229, 2800, Kgs. Lyngby, Denmark, rand@kt.dtu.dk Wentao Gong, Center for Energy Resources Engineering (CERE), Department of Chemical and Biochemical Engineering, Technical University of Denmark (DTU), Søltofts Plads 229, 2800, Kgs. Lyngby, Denmark, wengon@kt.dtu.dk Sai Hema Bhavya Vinjarapu, Center for Energy Resources Engineering (CERE), Department of Chemical and Biochemical Engineering, Technical University of Denmark (DTU), Søltofts Plads 229, 2800, Kgs. Lyngby, Denmark Jens Kristian Jørsboe, Center for Energy Resources Engineering (CERE), Department of Chemical and Biochemical Engineering, Technical University of Denmark (DTU), Søltofts Plads 229, 2800, Kgs. Lyngby, Denmark Sebastian Nis Bay Villadsen, Center for Energy Resources Engineering (CERE), Department of Chemical and Biochemical Engineering, Technical University of Denmark (DTU), Søltofts Plads 229, 2800, Kgs. Lyngby, Denmark Philip Loldrup Fosbøl, Center for Energy Resources Engineering (CERE), Department of Chemical and Biochemical Engineering, Technical University of Denmark (DTU), Søltofts Plads 229, 2800, Kgs. Lyngby, Denmark, plf@kt.dtu.dk Chapter Number and Title – Chapter 11, Special Case Studies in Sustainable Carbon Capture

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One of the major issues encountered in the Post Combustion CO₂ Capture processes is the degradation of the solvent which can be in great part attributed to the presence of oxygen in the solution. The present report focuses on the demonstration of DORA (Dissolved Oxygen Removal Apparatus), a technology developed by TNO as a counter-measure of oxidative degradation. The DORA was first operated in combination with TNO's mobile bench-scale CO₂ capture pilot (5 Nm³/h flue gas capacity) with artificial flue gas, showing an instant drop of 15% and an overall reduction of approximately 70% in the ammonia emissions from the absorber, which is an indication of reduced degradation. The technology was also demonstrated using the same pilot in an industrial environment in collaboration with the facility PlantOne bringing DORA from TRL5 to TRL6. This campaign proved that DORA contributed to the deacceleration of solvent degradation. The tests were executed with a porous membrane, and it was observed that exposure to degraded solvents led to solvent leakage through this membrane. Therefore, the use of a coated membrane was proposed to optimize the operation and increase oxygen removal. The use of this membrane is demonstrated at TRL3. Along with that, a model was developed to determine mass transfer resistances and the membrane area required to remove different levels of dissolved oxygen.

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After a 13,000-hour test campaign with aqueous 30 wt% MEA (2-aminoethanol) solvent at the CO₂ capture pilot plant at Niederaussem, another long-term test was carried out as part of the ALIGN-CCUS project. This test ran for more than 12,275 hours with aqueous AMP/PZ (2-Amino-2-methyl-1-propanol/piperazine) solvent, named CESAR1 (3.0 molar AMP (~26.74 wt%) and 1.5 molar PZ (~12.92 wt. %)). A minimum specific reboiler duty of 2,970 MJ/t_CO2 was identified for the capture plant operation with four active absorber beds (total 16 m packing height) and intercooling (40°C). Neither a lower desorber pressure of 1.5 bar(a), instead of 1.75 bar(a), nor a change of the different positions of intercooling had a significant effect on energy consumption. Reduction of the active packing height to three beds (i.e., 12 m), resulted in a moderately higher specific energy demand (+100 MJ/t_CO2). Tests with CO₂ capture rates between 90 and 98% showed only a small increase of the specific energy demand at 95% (+20 MJ/t_CO2) and four active packings (98%: +250 MJ/t_CO2). The average solvent consumption of CESAR1 during 400 days of operation was 0.45 kg/t_CO2 and is lower than for MEA if the phase of accelerated non-linear degradation of MEA is taken into account. CESAR1 follows a slow-progressing linear degradation behavior; neither a critical metal ion concentration threshold value could be found that triggers fast degradation nor a correlation between accumulated trace components or metal ion concentrations in the solvent and the degradation rate was observed. Highly transient tests were conducted to investigate the dynamic behavior of the capture plant and subsequently special settings were chosen to stimulate high emissions for the investigation of aerosol-based emissions, connected with performance tests of several emission mitigation measures: single water wash, double water wash, acid wash, dry bed, wet electric precipitator and flue gas pre-treatment. When applying the dry bed configuration, emissions of AMP between 15 - 20 mg/Nm³, PZ between 3 - 7 mg/Nm³, and NH₃ below 3 mg/Nm³ were achieved.

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This work aims to understand oxygen solubility in pure and aqueous amine solvents for CO₂ capture. Commercially available dissolved oxygen sensors were studied to evaluate whether these can be used for measuring oxygen solubility in the carbon capture processes. It also aims to understand the possible discrepancies from realistic concentrations of oxygen when using a dissolved oxygen sensor. Two independent measurement principles were used for this purpose, both electrochemical and optical. Furthermore, a Winkler titration method was used to aid the validation of the sensors as well as understanding salting-out effects. A simple model for predicting oxygen solubility in CO₂-loaded ethanolamine solutions was made, which also has potential for predicting oxygen solubility in other loaded amine solutions. The results of the study show that dissolved oxygen sensors may be applied for measurement of oxygen concentrations in amine solutions and that different amines and different concentrations in water only show small variations in oxygen solubility. The sensors may also be used in CO₂-loaded amine solutions, but here the increased conductivity of the solution may give a higher measured concentration of oxygen, than it is in reality. In ethanolamine, the consumption of oxygen is faster than the mass transfer of oxygen from gas to liquid phase, giving lower concentrations of oxygen than it should be in absence of a chemical reaction between oxygen and amine.

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Carbon dioxide (CO2) is currently considered as a waste material due to its negative impact on the environment. However, it is possible to create value from CO2 by capturing and utilizing it as a building block for commodity chemicals. Electrochemical conversion of CO2 has excellent potential for reducing greenhouse gas emissions and reaching the Paris agreement goal of zero net emissions by 2050. To date, carbon capture and utilization technologies (i.e., capture and conversion) have been studied mostly independently. In this communication, we report a methodology based on the integration of CO2 capture and conversion by the direct utilization of a CO2 capture media as the electrolyte for electrochemical conversion of CO2. This has a high potential for reducing capital and operational cost when compared to traditional methodologies (i.e., capture, desorption, and then utilization). A mixture of chemical and physical absorption solvents allowed for the captured CO2 to be converted to formate with faradaic efficiencies of up to 50% and with carbon conversion of ca. 30%. By increasing the temperature in the electrochemical reactor from 20 to 75 °C, the reaction rate toward formate increased by a factor of 10, reaching up to 0.7 mmol/m2·s. The direct conversion of captured CO2 was also demonstrated for carbon monoxide formation with faradaic efficiencies of up to 45%.

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Carbon utilisation is gaining attention on a scientific and public level, as part of a strategy to close the carbon cycle. Existing CO2 utilisation strategies, based on the use of pure CO2, lead to relatively high cost for e-fuels and commodity chemicals. This paper proposes an integration of CO2 capture with CO2 utilisation, directly in the CO2 capture solvent, to improve the cost performance. In this concept, ammonium bicarbonate is produced by CO2 capture and subsequently hydrogenated to ammonium formate. With the use of a thermal split, the ammonium formate can be split into a formic acid product solution and ammonia. Techno-economics show the potential of this route supported by proof-of-concept experiments for the innovative steps in the process. Assessment of a 100 ktonne/y CO2 capture and utilization leads to a formic acid production price of 365-456 €/t, using a varying hydrogen price of 2-4 €/kg, which is in the price range of industrial formic acid.@en

Nowadays, nearly 50% of the hydrogen produced worldwide comes from Steam Methane Reforming (SMR) at an environmental burden of 10.5 t_CO2,eq/t_H2, accelerating the consequences of global warming. One way to produce clean hydrogen is via methane pyrolysis using melts of metals and salts. Compared to SMR, significant less CO₂ is produced due to conversion of methane into hydrogen and carbon, making this route more sustainable to generate hydrogen. Hydrogen is produced with high purity, and solid carbon is segregated and deposited on the molten bath. Carbon may be sold as valuable co-product, making industrial scale promising. In this work, methane pyrolysis was performed in a quartz bubble column using molten gallium as heat transfer agent and catalyst. A maximum conversion of 91% was achieved at 1119 °C and ambient pressure, with a residence time of the bubbles in the liquid of 0.5 s. Based on in-depth analysis of the carbon, it can be characterized as carbon black. Techno-economic and sensitivity analyses of the industrial concept were done for different scenarios. The results showed that, if co-product carbon is saleable and a CO₂ tax of 50 euro per tonne is imposed to the processes, the molten metal technology can be competitive with SMR.

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Herein, we describe a study of the electrochemical reduction of oxalic and glyoxylic acids toward a feasible green and sustainable production of tartaric acid in aqueous and/or acetonitrile solvent using silver and lead electrodes. Our results show that on the silver electrode, for both oxalic acid and glyoxylic acid, the reduction reaction is more favorable toward the dimerization step, leading to tartaric acid, due to the increase in the local pH, while on the lead electrode, the step involving the protonation of the intermediate is more favorable, leading to the formation of glycolate. Techno-economic analysis shows that tartaric acid production from glyoxylic acid and from oxalic acid via electrochemical synthesis can be a potential process at the industrial scale. In the present case, the oxygen evolution reaction was chosen as the reaction at the other electrode for practical reasons, but oxygen is a low-value product. Another anodic reaction with a more valuable oxidation product can be selected to increase the profitability of the overall electrochemical process and thereby decrease the total production costs of tartaric acid.

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Electrochemical processes are a promising technology for industrial production of chemicals. One of the major drawbacks of electrochemical systems is the low mass transfer of reactants toward the active surface area of the electrode. In this paper, an approach is presented to enhance the mass transfer and increase the overall performance of the reactions. The strategy comprises introduction of a pulsed electrolyte flow in the electrochemical flow cell. This pulsating behavior results in an improved mass transfer of electroactive species due to a higher instantaneous velocity driven by the pulsations. Though the net residence time of the reactants will not be altered due to the pulsation, the resulting enhancement of mass transfer leads to an increase of the conversion. The oxidation of 1,2-propanediol to lactic acid and pyruvic acid mediated by 4-Acetamido-(2,2,6,6-Tetramethylpiperidin-1-yl) oxidanyl (ACT-TEMPO) was chosen to study the influence of the pulsed flow. Under the pulsating regime, a yield increase of lactic acid of a factor of two and a 15-20% gain in selectivity to a total of 95% toward lactic acid can be achieved by tuning the process parameters.

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Aerosol based emissions have been reported from several Post-Combustion CO₂ capture (PCCC)pilot plants. These are known to pose a significant challenge in large scale implementation of PCCC processes. The aerosol nuclei are in the form of H₂SO₄ droplets or Na₂SO₄ particles, typically less than 0.1 μm and 0.255 μm, respectively. A wet electrostatic precipitator (WESP)is considered to be a potential counter-measure for removing these ultrafine aerosol nuclei from the flue gas. However, it has been observed that at certain operating conditions of the WESP, additional particles are formed which can act as aerosol nuclei. This study was performed to find out the specific operating conditions in terms of feed SO₂ concentration and applied WESP voltage, at which WESP results in generation of new particles. In the absence of SO₂, no additional particles are formed for the entire range of applied WESP voltage. At the lowest SO₂ concentration of 9 ppmv, additional particles were generated beyond 10 kV. The smallest size fractions contribute to more than 99% of the total number of particles, with 0.006 μm contributing to more than 80%. At the outlet of the absorber, although majority of the particles are of 0.006 μm (>60%)and 0.0158 μm (ca. 5%), larger particles of sizes 0.0945 to 0.945 μm, contributes to the remaining 35% of the total number. The shift in number distribution results in increase of aerosol mass from about 10⁻⁴ to 5 × 10^-3 mg/m³ to 0.2 to 0.5 mg/m³, from the inlet to the outlet of the absorber, respectively. Aerosol based MEA emissions were observed for the lowest SO₂ concentration of 9 ppmv and a voltage of 16 kV. Total MEA emissions were in the range of 600–1050 mg/Nm³. Based on these tests, industrial scale WESPs are likely to result in additional particles which can act as aerosol nuclei even at a SO₂ concentration as low as 9 ppmv. Additional tests aimed at SO₂ concentration lower than 9 ppmv in the feed gas, combinations of varying H₂SO₄ aerosol and SO₂ in feed gas, and varying flue gas velocity needs immediate attention to define the operating limits for WESP.

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