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Even though the energy penalties and solvent regeneration costs associated with amine-based absorption/stripping systems are important challenges, this technology remains highly recommended for post-combustion decarbonization systems given its proven capture efficacy and technical maturity. This study introduces a novel centralized and decentralized hybrid control strategy for the post-combustion carbon capture plant, aimed at mitigating main disturbances and sustaining high system performance. The strategy is rooted in a comprehensive mathematical model encompassing absorption and desorption columns, heat exchangers and a buffer tank, ensuring smooth operation and energy efficiency. The buffer tank is equipped with three control loops to finely regulate absorber inlet solvent solution parameters, preventing disturbance recirculation from the desorber. Additionally, a model-based controller, utilizing the model predictive control (MPC) algorithm, maintains a carbon capture yield of 90% and stabilizes the reboiler liquid temperature at 394.5 K by manipulating the influent flue gas to the lean solvent flowrates ratio and the heat duty of the reboiler. The hybrid MPC approach reveals efficiency in simultaneously managing targeted variables and handling complex input–output interactions. It consistently maintains the controlled variables at desired setpoints despite CO2 flue gas flow disturbances, achieving reduced settling time and low overshoot results. The hybrid control strategy, benefitting from the constraint handling ability of MPC, succeeds in keeping the carbon capture yield above the preset minimum value of 86% at all times, while the energy performance index remains below the favorable value of 3.1 MJ/kgCO2. [ABSTRACT FROM AUTHOR]

Perovskites such as SrTiO3 are interesting for photocatalytic applications due to their structure-related and electronic properties. These properties are influenced by the presence of SrCO3 which is often formed simultaneously during the hydrothermal synthesis of SrTiO3. In this study, SrTiO3-SrCO3 composites with different contents of SrCO3 (5–24 wt%) were synthesized. Their morphological, structural, and optical properties were investigated using complementary methods such as scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen sorption, and diffuse reflectance spectroscopy (DRS). Their photocatalytic activity was assessed during the degradation of diclofenac (DCFNa) in aqueous solution and CO2 photoreduction under Xe lamp irradiation. Improved photocatalytic efficiency in DCFNa degradation was observed for all the studied composites in comparison with SrTiO3, and the highest mineralization efficiency was obtained for the sample with 21 wt% SrCO3 content. The presence of SrCO3 led to an increased concentration of active species, such as •OH radicals. Otherwise, its presence inhibits CH4 and C2H6 production during CO2 photoreduction compared with pure SrTiO3. [ABSTRACT FROM AUTHOR]

The paper presents a new control system configuration for the post combustion CO2 carbon capture process using amines. The control system structure consists in six control loops and has in its core the cascade control strategy. The proposed cascade control system has the desired carbon capture rate as the master controller target, and the molar ratio between the lean MEA and the influent CO2 flowrates as the slave controller manipulated setpoint. They have associated the reboiler temperature control in the stripper and the concentration of MEA, temperature and level control in the buffer tank. The buffer tank, accompanied by its control loops, was specifically introduced in the carbon capture plant in order to reduce the interaction between the absorption and stripping units. The decentralized control system was tested for assessing its performance to cope with the typical influent CO2 flowrate disturbance, considered to act in a periodic scenario. Good disturbance rejection and effective restoration of the nominal operation state were achieved, while the energy performance index value was kept at reduced values. They demonstrate valuable operation flexibility of the controlled CO2 carbon capture plant. [ABSTRACT FROM AUTHOR]

There is a significant interest in modelling the wastewater treatment plants (WWTP) because with a calibrated model a large variety of operational strategies can be evaluated, the control system design may be improved and enhanced constructive alternatives may be proposed. The Activated Sludge Model No. 1 (ASM1) has the potential of describing the biochemical processes taking place in WWTPs, in association with the Benchmark Simulation Model No. 1 (BSM1) which adds the description of the involved physical processes. An important challenge for reliable simulators development is the dynamically changing composition of the influent wastewater, also varying from one WWTP to another. Due to this reason, it is necessary to fit the model for each WWTP. This paper proposes a new methodology for the dynamic simulator calibration of a municipal WWTP. Different optimization methods are used for the simulator calibration and results of the different approaches are comparatively presented. Based on WWTP measurements a set of influent variables, bioreactor parameters and settler parameters are calibrated. Optimization was carried out based on classical, genetic, hybrid and Pareto multiobjective algorithms and their performance is discussed, revealing their strengths and limitations. [ABSTRACT FROM AUTHOR]

The influent temperature has an important effect on the activated sludge process at the municipal Wastewater Treatment Plants (WWTPs). This research is associated to a case study of a Romanian municipal WWTP with Anaerobic-Anoxic-Aerobic (A2O) layout. Based on mathematical modelling it was studied the influent wastewater temperature effect on the effluent components concentration and on the concentration of pollutants and biomass concentrations at the outlet of biodegradation basins aerobic zone. Three influent temperature profiles were considered and implemented in the simulator. They reveal the representative 22 days period of the months: February (coldest water season), May (intermediate season) and July (warmest season). The simulations were performed both in steady and dynamic state. It was observed that higher influent temperatures intensify the nitrification and denitrification processes. As a result, the concentration of the nitrogen compounds in the effluent and at the end of the bioreactors decreases with the increase of the temperature. The carbon rich organic components feature a minor increase in the effluent. The study reveals that short time daily influent temperature changes do not have significant effect on the effluent components concentration, but the long-term ones affect the WWTP performance. [ABSTRACT FROM AUTHOR]

Abstract: Although the activated sludge models for waste water treatment plants (WWTPs) offer comprehensive description of their involved biochemical and physical processes, it is a challenging task to calibrate the model for the operational plant. The article first presents a systematic calibrating procedure applied to the Activated Sludge Model No.1 (ASM 1), showing its potential to be extended to other WWTPs. It particularly addresses cases when comprehensive knowledge on the WWTP influent composition does not exist. An optimisation‐based approach is used for the WWTP model calibration and for finding the partially unknown influent composition. Dynamic model validation shows good match between model predicted values and WWTP measured data. Second, a new feed‐forward control strategy is designed for the WWTP and compared with the conventional nitrate‐nitrite nitrogen and dissolved oxygen control. The evaluation based on the effluent quality index, pumping and aeration energy and the number of effluent violations assessment tools, demonstrates incentives for the proposed control approach. [ABSTRACT FROM AUTHOR]