Search

The construction sector is among the most polluting industries globally, accounting for approximately 37.5% of the European Union's total waste generation in 2020. Therefore, it is imperative to develop strategies to enhance the sustainability of this sector. This paper proposes a multiscale COMSOL Multiphysics numerical model for an ex situ mineral carbonation process of hydrated lime. The carbonation process is characterized at both the micro- and macroscale levels, encompassing interactions within and between the particles. This model incorporates both reaction and diffusion phenomena, considering the effects of porosity and liquid-water saturation parameters. Generally, liquid-water saturation enhances the reaction kinetics but not CO2 diffusion, while porosity improves CO2 diffusion throughout the granular bed. The model has been experimentally validated, showing promising results by accurately characterizing carbonation tendencies and the influence of the CO2 flow rate and the initial water-to-solid ratio on the carbonation process. The proposed mathematical model facilitates the study of various parameters, including particle radius, reactor geometry, and material porosity. This analysis is valuable for both current and future projects, as it aims to identify the most profitable configurations for the hydrated lime carbonation process. [ABSTRACT FROM AUTHOR]

Compared to conventional monoethanolamine (MEA), alternative solvents are expected to substantially contribute to reduce the energy demand of postcombustion CO2 capture from flue gases. This study presents a comprehensive techno-economic analysis of a 27wt% 2-amino-2-methyl-1- propanol (AMP) + 13wt% piperazine (PZ) aqueous solution for CO2 capture, compared to a 30 wt% MEA solution. The study addresses the retrofit of a carbon capture unit to a biomass-fired combined heat and power (CHP) plant, effectively making it a bioenergy with a carbon capture and storage (BECCS) system. The treated flue gas has a flow rate of 23 tons/hour (t/h) with 11.54 vol% CO2 and a 90% capture rate is aimed for. Aspen Plus V14 was employed for process simulations. Initially, binary interaction parameters for AMP/PZ, AMP/H2O, and PZ/H2O are regressed using vapor-liquid equilibrium (VLE) data, which were retrieved from literature along with reaction kinetics. Validation of parameters from available experimental literature yields an average absolute relative deviation (AARD) of only 5.9%. Afterwards, a process simulation model is developed and validated against experimental data from a reference pilot plant, using a similar AMP/PZ blend, resulting in 5% AARD. Next, a sensitivity analysis optimizes operating conditions, including solvent rate, absorber/stripper packing heights, and stripper pressure, based on regeneration energy impact. Optimized results, compared to MEA, reveal that AMP/PZ reduces the energy consumption from 3.61 to 2.86 GJ/tCO2. The retrofitting of the capture unit onto the selected CHP plant is examined through the development of a dedicated model. Two control strategies are compared to address energy unavailability for supplying the capture unit. The analysis spans 4 months, selected to account for seasonal variations. At nominal capacity, CO2 emissions, rendered negative by biomass combustion and CO2 capture, reach a maximum of -3.4 tCO2/h compared to 0.36 tCO2/h before retrofitting. Depending on the control strategy and CHP plant operating point, the Specific Primary Energy Consumption for CO2 Avoided (SPECCA) ranges from 4.91 MJ/kgCO2 to 1.76 MJ/kgCO2. Finally, an economic comparison based on systematic methodology reveals a 7.87% reduction in capture cost favoring the AMP/PZ blend. Together, these findings highlight AMP/PZ as a highly favorable alternative solvent. [ABSTRACT FROM AUTHOR]

Solvent degradation represents one of the main operational drawbacks of the post-combustion CO2 capture process. Degradation not only induces additional costs for solvent make-up, it also impacts the process efficiency and its environmental penalty due to the emission of various degradation products. There is still a gap of knowledge about the influence of process operating conditions on degradation, making it currently impossible to predict the solvent degradation rate in CO2 capture plants. Morever, the reaction mechanisms corresponding to solvent degradation are very slow, significantly complicating its study in industrial units. In the present work, appropriate experimental equipment and analytical methods are developed for accelerating the degradation of monoethanolamine solvents (MEA). The relevance of accelerated conditions is established by comparing artificially degraded solvent samples with degraded solvent samples from industrial CO2 capture pilot plants. Two approaches are evaluated implying either discontinuous or continuous gas feed, this latest being the most representative of industrial degradation. The respective influences of the gas feed composition and the gas-liquid transfer are evidenced and quantified. Finally, the present study leads to a better understanding of solvent degradation in the CO2 capture process with MEA. More generally, it also evidences that accelerated conditions at laboratory-scale may provide relevant information for the study of slow phenomena taking place in large-scale industrial processes. Further works include the development of a kinetic model for MEA solvent degradation and the extension of this methodology to other promising solvents in order to facilitate the operation and large-scale deployment of CO2 capture. [ABSTRACT FROM AUTHOR]

In the present work, the influenceof metal ions and oxidativedegradation inhibitors on the stability of monoethanolamine solvents(MEA) is studied. Solvent degradation induces additional costs andimpacts the environmental balance of the CO2capture processas well as its efficiency. The two main degradation pathways of MEAare studied under accelerated conditions: oxidative degradation withcontinuous gas feed and thermal degradation in batch reactors. Itis confirmed that metal ions (resulting from solvent impurities andwall leaching) enhance the oxidative degradation of MEA, while theydo not impact its thermal degradation. Moreover, different oxidativedegradation inhibitors are tested with varying results according tothe inhibitor. It appears that at the selected concentration, radicalscavengers like Inhibitor A and DMTD (2,5-dimercapto-1,3,4-thiadiazole)are more efficient than chelating agents like HEDP (1-hydroxyethylidenediphosphonic acid) at inhibiting oxidative degradation. Furthermore,attention must be paid to the influence of oxidative degradation inhibitorson the thermal degradation of MEA. Indeed, some inhibitors like DMTD,DTPA (diethylenetriaminepentaacetic acid), and DTDP (3,3′-dithiodipropionicacid) appeared to decrease the MEA thermal stability, which cannotbe accepted in industrial applications. Finally, a further drawbackof DTPA is its high affinity for metal ions, leading to a more corrosivesolution, so its use is not recommended for CO2captureapplications. [ABSTRACT FROM AUTHOR]