CO2 Flow Rate Research Articles

Selecting the approach for dynamic modelling of CO2 capture in biomass/waste fired CHP plants

Integrating CO2 capture with biomass/waste fired combined heat and power (CHP) plants is a promising method to achieve negative emissions. However, the use of versatile biomass/waste and the dynamic operation of CHP plants result in bigger fluctuations in the properties of flue gas (FG), e.g. CO2 concentration (CO2vol%) and flowrates, and the heat that can be used for CO2 capture, when comparing with coal fired power plants. To address such a challenge, dynamic modelling is essential to accurately estimate the amount of captured CO2 and optimize the operation of CO2 capture. This paper compares three dynamic approaches commonly used in literature, namely using the ideal static model (IST) and using dynamic models without control (Dw/oC) and with control (DwC), for MEA based chemical absorption CO2 capture. The performance of approaches is assessed under the variations of key factors, including the flowrate and CO2vol% of FG, and the available heat for CO2 capture. Simulation results show clear differences. For example, when the CO2vol% drops from 15.7 % to 9.7 % (about 38 %) within 4 hours, DwC gives the highest amount of captured CO2, which is 7.3 % and 22.3 % higher than IST and Dw/oC, respectively. It is also found that the time step size has a clear impact on the CO2 capture amount, especially for DwC. Based on the results, suggestions are also provided regarding the selection of dynamic modelling approaches for different purposes of simulations.

Making Methane Gas from CO2 using Ni/Al2O3 Catalyst in a fixed bed reactor

CO2 emissions are a component of greenhouse gases, it is estimated that around 18.35 billion tons of CO2 are released each year (Sulistyono, 2012). This is the result of the global economic recovery from the COVID-19 pandemic. IEA data shows that industrial processes and energy combustion account for nearly 89% of the energy sector's greenhouse gas emissions by 2021, with greenhouse gas emissions from gas combustion of just 0.7%. Converting CO2 to chemicals, or hydrogenating CO2 to methane, is one way of reducing CO2 in the atmosphere. Many studies have been conducted on how CO2 turns into CH4 using various methods, catalysts and other variables. The aim of this research is to make a fixed reactor bed for CO2 methanation. In addition, this research will use a nickel catalyst with alumina support (Al2O3).The method used is in situ. In this study, CO₂ was used as a raw material with a Ni/Al2O3 catalyst. The NaOH concentration was adjusted with variations of 1M, 1.5M, 2M, 2.5M, 3M. The CO2 flow rate was adjusted with 0.1 L/Minute, 0.2 L /Minute, 3 L/Minute Operating Time 60 minutes at 55°C. For the analysis of the Methane (CH) gas produced, it will be analyzed using a Multi Gas Detector Analyzer.

Experimental study on characterization of lime-based mineral carbonation reaction and CO2 sequestration.

This paper reports for the first time the use and application of a novel technique in the characterization of mineral carbonation reaction and CO2 sequestration in soil stabilization using flow meters. Soils based on SiO2 with two different sizes were tested. Lime (Ca(OH)2) was used as the reactant. Instant CO2 flow rate (L/min), total CO2 volume (L), temperature (°C), and absolute pressure (kPa) were monitored and recorded for 1h by flow meters connected to the mold inlet and outlet. It was determined that the mineral carbonation reaction started in the first seconds and ended before the 5th minute. The mineral carbonation is a short-term and potential reaction, and it is not a time-dependent reaction. It is separated from other carbonation reactions with these characteristics. The highest CO2 captured value was obtained in the soil mixed with 5% lime, where fines were not used. The second highest CO2 captured value was obtained in soil mixed with 1% lime, where fines were not used. CO2 captured with 1% lime is more than CO2 captured with 5% lime in the soil containing fines. Accordingly, 1-5% lime can be used in soil carbonation studies. According to the soil properties, the highest CO2 captured and the CO2 efficiency was achieved with the use of 6-7% water by weight.

Graphite-assisted microwave carbon dioxide gasification of wet stalks

In order to realize the low-carbon gasification of the typical wet stalks, the graphite was used as the microwave-absorbing agent and the heat transfer medium in the microwave field, and CO2 was used as the gasification agent to explore the characteristics of microwave CO2 gasification. After mixing the corn stalks, the rice stalks or the wheat stalks with different water contents and the graphite in a mass ratio of 4:1, CO2 was introduced for gasification in a microwave field. Experiments showed that with the increase in the water content, the carbon conversions, the gas yields and the volume fractions of the effective components all increased slowly in the front and rear sections, and increased rapidly in the middle section. When the CO2 flow rate was 0.6 Nm3·kg−1·min−1, the carbon conversions, the gas yields and the volume fractions of the effective components all reached their peaks. It was found that the structure of the three stalks changed from smooth to porous during the intermediate process of the graphite-assisted microwave gasification. The deashed stalks with water content of 60 % was gasified in a microwave field of 700 W for 1.25 min, and the BET specific surface areas of the generated porous carbon reached 2041–2054 m2 g−1, and the volume fractions of the effective components of the gasification gas were more than 95 %. With the prolongation of the gasification time, the carbon conversions increased slowly in the early and late stages, but increased rapidly in the middle stage. The reason was that the large amount of porous carbon generated in the middle stage was the gasifiable strong microwave-absorbing agent, which greatly increased the gasification temperature and accelerated the reaction rates. When the graphite was reused 10 times, the carbon conversions could still reach more than 80 %. The XRD tests were carried out on the graphite used many times to explore its deactivation mechanism. This paper has practical significance for the low-carbon CO2 recycling of stalks biomass, and provides a new way for the preparation of biomass-based porous carbon.

Effects of coal permeability rebound and recovery phenomenon on CO2 storage capacity under different coalbed temperature conditions during CO2-ECBM process

During the permeability evolution process, coal permeability rebound and recovery is an important behaviour. Currently, studies on it mainly focus on the effects of reservoir pressure changes, but the influence of temperature is also significant. In the study, a binary gas permeability evolution model was constructed, which considers the competition mechanism between effective stress, gas adsorption/desorption, and thermal expansion. The model was employed to study the dynamic evolution of various parameters during CO2 injection into CH4-containing coal at different temperatures. The findings demonstrate a complex permeability evolution over time, characterized by a rapid decrease followed by a significant increase and then another gradual decrease. And the time required for permeability rebound and recovery increases as the temperature increases. Moreover, by monitoring the law of gas migration at fixed points and other methods to obtain the changing trend of CO2 flow rate and CO2 cumulative storage volume on a time scale. The results showed that both CO2 flow rate and CO2 cumulative storage volume decreased with increased permeability rebound and recovery time. Inspired by the abovementioned laws, this study proposed using the stage-pressure injection method in high-temperature coal. Results indicate that the stage-pressure method can increase the CO2 injection effect.

Effect of conditions on wet carbonation products of recycled cement paste powder

Wet carbonation is deemed a successful approach to recycling waste concrete powder. Controlling the growth and properties of products in the recycled cement paste powder (CPP) is highly dependent on the wet carbonation conditions. Therefore, this study aims to examine the effect of wet carbonation parameters on wet carbonation products in CPP. The wet carbonation of CPP resulted in mixed distribution of silica gel and CaCO3 without significant layering on the CaCO3. In contrast, silica gel covered the outside of the CaCO3 in the case of dry carbonation. Increasing the temperature from 25 °C to 80 °C promoted and accelerated the crystallization and growth of amorphous CaCO3, increased the crystallite size of CaCO3 by 1.1–5.1 nm, and favored the formation of aragonite and vaterite; however, it also led to a significant crystal defect and/or distortion within CaCO3. Higher temperatures also promoted silica gel formation and increased its polymerization degree by 68.2%. On the other hand, increasing the CO2 flow rate from 3 L/min to 5 L/min facilitated the crystallization and growth of CaCO3 and contributed to the increase in the crystallite size of CaCO3 by 3.0–6.6 nm. Higher CO2 flow led to the incorporation of aluminum into silica gel and resulted in the transformation of its gel pores into capillary pores. The findings of this study contribute to a better understanding of the best experimental parameters to achieve a more efficient and effective concrete waste recycling process.

Excess properties, spectral analyses, and CO2 capture performance of N-methyldiethanolamine + polyethylene glycol 300 binary system

Density (ρ) and viscosity (η) data of polyethylene glycol 300 (PEG300) + N-methyldiethanolamine (MDEA) binary system at T = (298.15–318.15) K with a step of 5 K were measured at P = 1005 hPa. After that, the experimental ρ and η values were correlated and predicted by several semi-empirical models. Meanwhile, the Jouyban-Acree model presented a better fitting for the density, and the McAllister four-body equation presented a better fitting for the kinematic viscosity. Based on the ρ and η values, excess molar volume (VmE), partial molar volume (V1¯ and V2¯), viscosity deviation (Δη), and excess Gibbs energy of activation of viscous flow (ΔG∗E) of PEG300 (1) + MDEA (2) binary system were systematically calculated and analyzed. These excess properties showed the predominance of intermolecular self-conjugation in PEG300 (1) + MDEA (2) binary system, and it was further demonstrated by various spectral characterizations. Importantly, the PEG300 + MDEA aqueous system was used for 5 CO2 absorption (room temperature)-desorption (371.15 K) cycles at a CO2 flow rate of 200 mL/min, with the average CO2 capture performance of 0.65 mol CO2/mol MDEA of per cycle, demonstrating excellent absorption capability, and remained stable throughout the entire cycle.

Enzyme activities of rhizosphere soil with different root diameters had varied responses to N deposition in Pinus tabuliformis forest

Root system exhibits hierarchical traits in physiology and exudation, and responds variably to environmental changes. However, it remains unclear if these phenomena result in corresponding alterations in the microbial characteristics of rhizosphere soil and diverse responses to nitrogen (N) deposition. This study evaluated microbial biomass, gas flow, and enzyme activity in rhizosphere soil of three root diameter classes (R1, <0.5 mm; R2, 0.5–1.0 mm; R3, 1.0–2.0 mm) of P. tabuliformis, and their responses to N application (0, 3, 6, 9 g N m−2 y−1, corresponding to CN, LN, MN, and HN) in a P. tabuliformis forest. Rhizosphere soil of R1 exhibited significantly higher microbial biomass N (MBN) content, enzyme activities, CO2 and N2O flow rates than those of R2 and R3 (P < 0.05). Soil microbial biomass carbon (MBC) and phosphorus (MBP) contents, N2O and CH4 flow rates significantly increased with N applications. While soil MBN content increased with the LN treatment and decreased with the HN treatment, the largest value was observed in the LN treatment (84.89 mg kg−1). N application promoted Alkaline phosphatase (ALP) and Alanine transaminase (ALT) activities in R1 rhizosphere soil while decreasing their activities in R2 and R3 rhizosphere soils. Moreover, β-glucosidase (BG), N-acetyl-β-Glucosaminidase (NAG), β-xylosidase (XYL), and β-D-cellulosidase (CBH) activities in R1 rhizosphere soil were inhibited, while their activities in R2 and R3 rhizosphere soils were promoted by N application. N application directly promoted microbial biomass then inhibited enzyme activity. Besides, nutrient content of rhizosphere soil decreased with root diameters, which indirectly reducing enzyme activity and microbial biomass. N application directly affected soil CH4 flow rate, while N2O flow rate was indirectly promoted by N application through increasing microbial biomass. CO2 and CH4 flow rates were inhibited by N application through decreasing enzyme activity. Root diameter slowed down the CO2 and CH4 flow rates by reducing soil nutrient content and enzyme activity. In conclusion, N deposition has varied effects on microbial characteristics in rhizosphere soil of different diameter roots, which are relevant to the corresponding changes in root system and soil properties.

Formation characteristics and leakage termination effects of CO2 hydrate cap in case of geological sequestration leakage

Geological sequestration of carbon dioxide (CO2) has been considered one of the most effective strategies against global warming. The greatest concern on the stored CO2 in sub-seabed sediments is leakage risk and can be solved by the plugging effect of CO2 hydrate cap, which is derived from the capillary force change by hydrate crystal formation inside pores. This study experimentally simulated CO2 upward leakage process in water-containing sediments and investigated the plugging characteristics of formed hydrate cap via magnetic resonance imaging (MRI) and flow characteristic analysis. Different CO2 flow rates (0.3–4.0 ml/min) and initial pressures (1.8–3.0 MPa) were employed for experimental conditions, and the hydrate cap appeared with no CO2 efflux any longer after hydrate formation for several minutes. It is found that both slow flow of CO2 and high pressure are beneficial for the formation of hydrate cap, and the strength of hydrate caps formed in all cases is confirmed by 10.0 MPa pressure test without any CO2 leakage. In addition, the spatial water distribution and the hydrate cap location inside the sediments are analyzed by multi-level MRI images and pressure evolution calculation, respectively. Ultimately, this study conducted a CO2-water flow case and found that the strength of hydrate cap increases with the continuous formation of hydrates. Approximately 27.8% of hydrate saturation is a watershed of the plugging strength of CO2 hydrate cap. This study provides experimental evidences for the plugging effect of hydrate cap on terminating CO2 leakage and is of great significance for the scheme design and risk assessment of CO2 geological sequestration.

CO2 plasma gasification of bakelite-based electrical switch waste feedstock

Poor degradability of e-waste causes severe soil and water contamination. In recent times, plasma gasification has been an attractive way of solid waste management towards energy recovery considering the environmental benefits. To reduce the short end-of-life electrical products and net CO2 emissions, the low-grade feed of electrical switch waste (ESW) comprising of bakelite (BAK) is chosen for generating clean syngas through the plasma method using CO2. The influence of the feed rate of solid waste, feed CO2 gas and plasma torch power on the product yield and syngas composition is evaluated. Energy and exergy (2-E) analyses are performed to assess the feasibility of the process. The experiment results indicate a maximum syngas yield of ∼85% at the highest torch power of 1.6 kW, with high concentrations of H2 (24.36 vol%) and CO (43.61 vol%). At low torch power of 0.5 kW, the residual solid yield reaches 24.58%. Considering all the cases, syngas with a medium calorific value of up to 10.20 MJ/m3 is attained. For the optimum feed rate of 40 g/10 min, CO2 flow rate of 0.6 lpm and plasma power of 0.75 kW, the process achieved the highest cold gas and exergy efficiency of 42.33% and 35.99%, respectively. The obtained oil (viscosity = 6.43 cP, density = 0.975 g/ml, pH = 8.01 and LHV = 31.47 MJ/kg) is suitable for applications in combustion, transportation and chemical production after quality upgradation. The solid residue (volatile matter = 11 wt%, fixed carbon = 65.67 wt%, ash = 23.33 wt% and LHV = 15.51 MJ/kg) obtained containing Ba (70.42 wt%), Zn (3.87 wt%), Ti (3.25 wt%), etc. in the ash, can be used for making corrosion coating agents, alloys and paints after recovery. The oil analysis showed the formation of NH3 during the reaction at a high torch power of 1.6 kW. Lastly, the reaction mechanism of plasma gasification for the conversion of ESW into syngas is proposed.

Breaking K+ Concentration Limit on Cu Nanoneedles for Acidic Electrocatalytic CO2 Reduction to Multi‐Carbon Products

AbstractElectrocatalytic CO2 reduction reaction (CO2RR) to multi‐carbon products (C2+) in acidic electrolyte is one of the most advanced routes for tackling our current climate and energy crisis. However, the competing hydrogen evolution reaction (HER) and the poor selectivity towards the valuable C2+ products are the major obstacles for the upscaling of these technologies. High local potassium ions (K+) concentration at the cathode's surface can inhibit proton‐diffusion and accelerate the desirable carbon‐carbon (C−C) coupling process. However, the solubility limit of potassium salts in bulk solution constrains the maximum achievable K+ concentration at the reaction sites and thus the overall acidic CO2RR performance of most electrocatalysts. In this work, we demonstrate that Cu nanoneedles induce ultrahigh local K+ concentrations (4.22 M) – thus breaking the K+ solubility limit (3.5 M) – which enables a highly efficient CO2RR in 3 M KCl at pH=1. As a result, a Faradaic efficiency of 90.69±2.15 % for C2+ (FEC2+) can be achieved at 1400 mA.cm−2, simultaneous with a single pass carbon efficiency (SPCE) of 25.49±0.82 % at a CO2 flow rate of 7 sccm.

Breaking K+Concentration Limit on Cu Nanoneedles for Acidic Electrocatalytic CO2Reduction to Multi-Carbon Products.

Electrocatalytic CO2 reduction reaction (CO2RR) to multi-carbon products (C2+) in acidic electrolyte is one of the most advanced routes for tackling our current climate and energy crisis. However, the competing hydrogen evolution reaction (HER) and the poor selectivity towards the valuable C2+ products are the major obstacles for the upscaling of these technologies. High local potassium ions (K+) concentration at the cathode's surface can inhibit proton-diffusion and accelerate the desirable carbon-carbon (C-C) coupling process. However, the solubility limit of potassium salts in bulk solution constrains the maximum achievable K+ concentration at the reaction sites and thus the overall acidic CO2RR performance of most electrocatalysts. In this work, we demonstrate that Cu nanoneedles induce ultrahigh local K+ concentrations (4.22 M) - thus breaking the K+ solubility limit (3.5 M) - which enables a highly efficient CO2RR in 3 M KCl at pH = 1. As a result, a Faradaic efficiency of 90.69±2.15% for C2+ (FEC2+) can be achieved at 1400 mA.cm-2, simultaneous with a single pass carbon efficiency (SPCE) of 25.49±0.82% at a CO2 flow rate of 7 sccm.

Ethylene production by partial oxidation of biogas using lime as catalyst

AbstractBACKGROUNDThe oxidative coupling of methane (OCM) is an interesting route for direct conversion of methane into ethylene and ethane. Nevertheless, COx is a secondary product of this route, which decreases the selectivity of hydrocarbons. In this work it is proposed to overcome this drawback by using biogas as source of methane. In addition to being a renewable source of methane, the presence of CO2 in biogas may shift the balance of the methane combustion. For this purpose, it was evaluated how process conditions such as O2 and CO2 flow rates and temperature affect biogas‐based OCM, in the temperature range of 650–800 °C, using lime as catalyst.RESULTSThe increase in CO2 flow from 0 to 15 mL.min−1 increased the ethylene selectivity from 25.9% to 44.5% at 800 °C. As consequence, CO2 formation dropped from 53.9% to 18.3%. Methane conversion was not affected significantly by CO2 flow rate, remaining in the range of 22–25%. O2 flow was essential to activate the OCM reaction and the presence of higher concentrations of O2 favored the selectivity of ethylene, but also increased the CO2 produced through methane combustion. In the OCM experiments with variable flow of CO2, the highest C2 yield of 18% was obtained for the highest flow of co‐fed CO2, whereas the experiments with biogas and variable O2 flow showed the highest yield of ethylene for the highest flow of air co‐fed.CONCLUSIONThus, biogas‐based OCM was shown to be a promising route to improve C2 selectivity, since the CO2 present in the biogas minimizes the formation of CO2 in the reaction. The use of lime as a low‐cost catalyst proved to be viable for the OCM reaction, presenting results compatible with those obtained for catalysts with more complex composition. © 2023 Society of Chemical Industry.

Nanocrystalline silicon-oxygen based tunneling recombination junctions in perovskite/silicon heterojunction tandem solar cells

The tunneling recombination junction (TRJ) of efficient perovskite/silicon heterojunction tandem cells should possess excellent optoelectronic characteristics to minimize light parasitic absorption and carrier transport/recombination losses. One effective approach is the utilization of hydrogenated nanocrystalline silicon-oxygen (nc-SiOx: H) materials, which characteristics can be controlled by adjusting the flow rate of CO2 and doped gas during the fabrication process. By carefully screening the material properties, the suitable n/p-doped nc-SiOx: H materials can be identified. For n-nc-SiOx: H, it is necessary to use a lower CO2 flux and perform moderate doping, while for p-nc-SiOx: H, strict control of CO2 and Trimethylboron (TMB) fluxes at lower levels is essential to preserve the electrical properties. Compared to the TRJ based on nc-Si: H, the TRJ based on nc-SiOx: H exhibits notable improvements in the open-circuit voltage (VOC) and short-circuit current density (JSC) of the tandem cell. The VOC increases by 38 mV (from 1.822 V to 1.864 V), and the JSC gains 0.82 mA/cm2 (from 19.00 mA/cm2 to 19.82 mA/cm2). Consequently, the conversion efficiency of the tandem cell, with an aperture area of 0.5091 cm2, is enhanced from 25.70% to 27.16%. Additionally, by considering the distinct lateral and vertical growth characteristics of nc-SiOx: H, the fill factor (FF) experiences a significant enhancement when applied to the TRJ of large-area tandem cells. Specifically, the FF increases from 55.21% to 69.68%. As a result, for a tandem cell with an aperture area of 12.5 cm2, the conversion efficiency improves from 17.87% to 23.39%.

A Green Approach to Preparing Vaterite CaCO3 for Clean Utilization of Steamed Ammonia Liquid Waste and CO2 Mineralization

In the salt lake industry, large amounts of steamed ammonia liquid waste are discharged as byproducts. The conversion of the residues into high value-added vaterite-phase calcium carbonate products for industrial applications is highly desirable. In this research, the feasibility of preparing vaterite-phase CaCO3 in different CaCl2-CO2-MOH-H2O systems using steamed ammonia liquid waste was studied in the absence of additives. The effects of initial CaCl2 concentration, stirring speed and CO2 flow rate on the composition of the CaCO3 crystal phase were investigated. The contents of vaterite were researched by the use of steamed ammonia liquid waste as a calcium source and pure calcium chloride as a contrast. The influence of the concentration of CNH3·H2O/CCa2+ on the carbonation ratio and crystal phase composition was studied. The reaction conditions on the content, particle size and morphology of vaterite influence were discussed. It was observed that single vaterite-phase CaCO3 was favored in the CaCl2-CO2-NH4OH-H2O system. Additionally, the impurity ions in steamed ammonia liquid waste play a key role in the nucleation and crystallization of vaterite, which could affect the formation of single-phase vaterite. The obtained results provided a novel method for the preparation of single vaterite particles with the utilization of CO2 and offered a selective method for the extensive utilization of steamed ammonia liquid waste.

The role and effect of CO2 flow rate on the structure formation of ultrahigh porous activated carbon from H3PO4-impregnated waste cotton used as supercapacitor electrode material

The role and effect of CO2 flow rate on the structure formation of ultrahigh porous activated carbon from H3PO4-impregnated waste cotton used as supercapacitor electrode material

Description and Validation of Flow-Through Chambers of Respirometry for Measuring Gas Exchange in Animal Trials.

Indirect calorimetry (IC) is a widely used method to study animal energy metabolism by measuring gas exchange. The accuracy of IC depends on detecting variations in signals reflecting the metabolic response, which can be challenging due to measurement noise and external factors. This study proposes a methodology to validate IC systems, including an easy-to-use spreadsheet for data computing, to verify accuracy and detect whole-system leaks. We conducted a recovery test using a simulation of CO2 dynamics in MS Excel and injecting a known CO2 concentration into four respirometry chambers. The thought flow rate of CO2 was observed and compared to the expected rate from the simulation. Data filtering and computing, including a detailed calculation of signals calibration, Bartholomew transformation, and noise reduction, was developed to obtain the gas exchange and heat production parameters using an open-circuit IC system. The results from the recovery test in our system show that the proposed methodology is accurate and precise. The proposed methodology and recovery test can be used to standardize the validation of IC systems together with adequate data computing, providing accurate measurements of animal energy metabolism in different environmental conditions and energy utilization from feeds.

A novel concept of enhanced direct-contact condensation of vapour- inert gas mixture in a spray ejector condenser

An analytical model of direct steam condensation (DCC) in the novel idea of spray ejector condenser (SEC) in the presence of inert gas has been developed. It is based on continuity, momentum and energy equations for the steam-carbon dioxide mixture and direct contact condensation mechanisms due to heat transfer and concentration. Crucial in the process of DCC is atomisation of the motive fluid in the ejector. The effect of atomised droplet size is exhibiting a significant amplification influence with increasing size of the droplet. Motive fluid is driving the secondary fluid-mixture of steam and inert gas in the Venturi nozzle and is cold enough to cause direct condensation. The intensity of heat transfer process from steam to water when the phases are in direct contact is much higher than the heat transfer intensity in surface heat exchangers. The analytical model pertains to a subcritical flow of a mixture of steam and gas in SEC. The model exhibits satisfactory agreement with experimental data. The model of DCC predicts higher values of temperature drop between inlet and outlet from the mixing section for the case of smaller steam-CO2 flow rates. Increasing the flow rate of steam mixture from 1.2 g/s to 3.6 g/s results in a reduction of steam mixture temperature from 25 °C to 14 °C respectively, at CO2 flow rate of 6.8 m3/h. Condensation without presence of CO2 in the same range of steam flow rate, i.e. from 1.2 g/s to 3.6 g/s results in reduction of steam mixture temperature from 56 °C to 25 °C respectively, confirming in such way the effect of CO2 presence on the efficiency of DCC. Such model allow for discussion of parameters affecting process of condensation in SEC and ability of application such condenser in power plants.

Valorization of waste eggshell for CO2 sorbents production by sol-gel citric acid treatment in a fixed-bed reactor

This study assesses the potential of the eggshells as a promising and alternative CO2 adsorbent. With the aim of enhancing the CO2 capture performance of raw eggshell, it was modified by sol-gel citric acid treatment. Both adsorbents were characterized by N2 adsorption-desorption, XRF, XRD and SEM techniques. Preliminary adsorption tests in TGA revealed that the acid-modified eggshell achieved significantly higher carbonation conversion than the raw eggshell adsorbent in the 650–750 ºC adsorption temperature range, reaching a carbonation conversion of 69% at 700 ºC. The cyclic performance of the modified eggshell, tested in TGA at 700 ºC under 15 vol% CO2, confirmed that sol-gel acid treatment led to a very stable adsorbent, with a slight improvement in CO2 adsorption capacity during the first four cycles (from 0.54 to 0.58 gCO2 gads−1), followed by stable performance due to self-reactivation phenomena. Moreover, additional experiments were carried out in a fixed bed reactor under more realistic conditions to study the influence of temperature (600–750 ºC) and CO2 flow rate (50–125 mL min−1) using the modified eggshell. An increase in temperature under 15 vol% CO2 stream led to a decrease in the carbonation conversion of the adsorbent, with the maximum CO2 uptake at 600 ºC (0.64 gCO2 gads−1). Regarding the role of the CO2 flow rate at 700 ºC, increasing from 75 to 125 mL min−1 CO2 had minimal effect, maintaining a capture amount of approximately 0.49 gCO2 gads−1. These results confirmed the potential of the acid-modified eggshell as a low-cost and environmental friendly adsorbent for CO2 capture, which indeed may significantly improve the economic feasibility of the CCUS processes.

Valorization of food side streams by supercritical fluid extraction of compounds of interest from apple pomace

Supercritical CO2 (scCO2) extraction, a green technology still little applied to side streams, has been used to explore the potential recovery of beneficial compounds from apple pomace, a food industry byproduct. The study examines the potential of scCO2 extraction on freeze-dried and airflow dried apple pomace, using laboratory-scale equipment with varying pressures (200–400 bar), temperatures (35–55 °C) with a fixed CO2 flow rate. Extracts were analyzed through LC-MS and GC-MS, while antioxidant capacity was assessed using the ABTS assay. The results were compared to those from Soxhlet n-hexane extraction. Optimal conditions of 300 bar and 55 °C with freeze-dried apple pomace yielded the highest mass loss. The main compounds identified included glyceryl dilinoleate, linoleic acid, and diacyl glycerol, with significant ursolic acid content. A preliminary higher scale feasibility test under optimal conditions demonstrated promising, duplicable outcomes, supporting prior claim that apple pomace contains valuable ingredients that can be reused in various industrial sectors.