When CO2 is considered gas of interest, flue gas from natural gas or coal-fired power plants, cement, and iron and steel industries mostly comprises of pollutants including NOx, O2, SOx, and flue dust which can potentially affect the performance of the amine blend in the presence of oxygen. Flue dust comes from a variety of industrial sources and is made up of tiny inorganic oxide particles including Al2O3, Fe2O3, ZnO, CuO, MgO, MnO and SiO2.Understanding how these impurities dissolve and interact with the blend is crucial for designing more robust and efficient CO2 capture processes.

Regardless of the effectiveness of electrostatic precipitators which remove most of the dust particles from flue gases before CO2 capture, traces of these dust particles can escape and accumulate in a downstream absorber overtime, hence clogging packings, pipelines and heat exchangers. This can reduce the efficiency of the equipment. The most detrimental impact of these dust particles is their ability to catalyze the rate of degradation of an amine solvent. This leads to the formation of degradation products which can decrease the performance of the solvent through foaming, fouling and corrosion. This easily primes to amine losses hence the need for reclaiming and to replace with fresh amine which can incur a lot of operating cost.

Another direct impact is the release of toxic compounds due to the degradation of the amine which pose a threat to the environment. These inorganic oxides serve as catalysts in a typical oxidative amine degradation. Oxidative degradation occurs in the presence of oxygen and other oxidants in flue gas. Upon dissolution with the amine, these metal oxides release their metal ions which reacts with the amine with a direct electron transfer redox reaction. The dissolved metal serves as a Lewis acid by accepting electron from the amine which leads to the formation of an amine radical hence the release of ammonia as a predominant emission from amine degradation.  The reduced metal is further oxidized by the dissolved oxygen and this becomes an alternating procedure till the complete degradation of the amine solvent.

The research involves conducting comprehensive laboratory experiments, carefully simulating the conditions encountered in an actual CO2 absorption system. The effects of these flue gas impurities on the amine blend’s stability will be critically analyzed to determine the degradation rates. Based on these rates, a model will be developed to predict the stability of any new solvent when exposed to different flue gas concentration scenarios. This information can be used to optimize the capture process and ensure that it is as efficient as possible. By studying these interactions, potential challenges will be identified and effective mitigation strategies proposed.

The global concern over climate change has led to the implementation of various measures to reduce greenhouse gas emissions, including carbon capture and storage (CCS) technology. One of the most promising CCS technologies involves the removal of CO2 from flue gas emitted by power plants and industrial processes, and either use or store it. However, the presence of sulfur dioxide (SO2) and nitrogen dioxide (NO2) in flue gas poses challenges to the efficient operation of amine-based CO2 capture systems. SO2 and NO2 in the flue gas does not only contribute to air pollution and acid rain but also, harm the CO2 capturing process by reacting with the amine to form Heat Stable Amine Salts (HSAS). HSAS causes corrosion, promote foaming and ‘handcuff’ the amine solution used for CO2 absorption.

Processes such as Selective Catalytic Reduction (SCR), Selective Non-catalytic Reduction (SNCR), and Flue Gas Desulfurization (FGD) are employed in industries to control SOx and NOx emissions. Nonetheless, with the deployment of these pollutant removal technologies, residual quantities of SO2 and NO2 remain in the flue gas entering the carbon capture system. For this reason, two of the major suppliers of CO2 capture plant, Fluor and Mitsubishi Heavy Industries (MHI), recommend limits for these contaminants in the flue gas entering the amine scrubber in other to minimize the detrimental effect of these impurities. Fluor suggested a SOx and NOx limits of 10 ppmv and 20 ppmv, and Mitsubishi Heavy Industries (MHI) discussed a SOx limit of 1–2 ppmv and a low but undefined NO2 limit (Reddy et al., 2008). As a result, to optimize the performance of amine-based CO2 capture systems, it is essential to develop effective pretreatment methods that enable simultaneous removal of SO2 and NO2 from flue gas before carbon capture with amine solvents.

Integrated wet scrubbing involves the use of tailored scrubbing solutions or suspensions that can effectively absorb both SO2 and NO2 simultaneously. This approach minimizes the need for separate treatment systems and reduces capital and operating costs. Additionally, combined sorbent-based systems utilize advanced sorbent materials capable of selectively capturing both SO2 and NO2 from flue gas. These materials exhibit high sorption capacities, selectivity, and stability, ensuring efficient removal of pollutants without compromising the performance of amine solvents in subsequent CO2 capture steps. Integration of these pretreatment techniques with amine-based CO2 capture systems can enhance overall process efficiency, reduce energy consumption, and minimize environmental impacts.

Our student will investigate the simultaneous NO2 and SO2 removal from flue gas using a novel, low-cost, and formulated green solvent. His study will emphasize the significance of optimizing operational parameters, such as temperature, residence time, and flue gas composition, to achieve efficient simultaneous removal of SO2 and NO2. The study will be conducted on a laboratory batch-scale using a simulated flue gas stream with varying concentrations of NO2 and SO2. Furthermore, empirical data generated from his work will be evaluated to study the performance and kinetics of the formulated solvent for further study.

In this post, we explain why carbamate of sterically hindered AMP is unstable relative to that of MEA. The instability of AMP carbamate leads to an easy break down to release CO2 and amine in the desorption process, thus giving rise to a higher CO2 loading and a lower desorption heat requirement than those of MEA. As shown on the graphical abstract, AMP structurally has 2 methyl groups (-CH3) on the tertiary carbon adjacent to the nitrogen while in contrast to MEA, the same carbon has only 2 hydrogens attached to it. Methyl groups in AMP are known as electron releasing groups so that they are relaying their electron density to the tertiary carbon and then the nitrogen.

This phenomenon causes AMP carbamate to destabilize by being explosed to 1) increased electron density on the N which is highly desirable for a reaction with proton from amine (H+) to trigger the carbamate breakdown process and 2) increased electron repulsion with the delocalized electrons on the carbonyl group whose effect destabilizes the carbamate and makes the break-down process more favorable.

In comparison to MEA, the 2 hydrogens (-H) on the tertiary carbon do not have the same inductive effect as seen from the methyl groups. As a result, the carbamate nitrogen reactivity is not enhanced by any extra electron density as seen in AMP carbamate and so its reaction with proton to break down it. The instability effect triggered by electron repulsion with the carbonyl group also is not there. The stability of MEA carbamate is therefore attributed to a combination of these 2 factors which then makes the compound break down process harder to occur compared to that of AMP. The CO2 loading and heat requirement as a result are higher than the case of AMP.

In order to attain net zero carbon emissions by 2050 and meet a 45% of biofuel production from waste resources target by 2030, there is the need to explore catalysts for increasing biofuel yield. This work will explore the use of environmentally benign materials for biodiesel production.

Through photosynthesis, plants use water and CO2 in the atmosphere produce oxygen and glucose which is converted to alcohol (ethanol) on fermentation. Some plants can synthesize oils. This process helps in reducing the carbon content in the atmosphere as afforestation is being encouraged for this purpose. However, the use of fossil-based fuels releases enormous amounts of CO2 into the atmosphere. This release effect cannot be curbed by plant photosynthesis only.  Bio-based fuels have relatively lower carbon content and hence release relatively minimal amounts of CO2 during energy production. Recycling of CO2 produced from biofuels (biodiesel) into plants via photosynthesis, to produce oxygen as a by-product, yields a net zero carbon emission into the atmosphere. Waste cooking oil (WCO) from restaurants and ethanol will be used as the main raw materials for the biodiesel production via transesterification reaction.

Heterogeneous catalysts have attracted great attention in recent times for use in biodiesel production. The need for the development of heterogeneous catalysts has risen because homogeneous catalysts used for biodiesel production pose some drawbacks, such as wastewater generation and loss of biodiesel as a result of washing. Various environmentally benign catalysts are being developed to increase biodiesel yields and quality. Cheap yet efficient catalysts, including fish scales, cow bones, and eggshells, are being investigated in this research due to their high CaO content, which has higher basicity, is non-corrosive, easier to handle than homogenous catalysts, and is safe to the ecosystem which makes it an interesting choice for a catalyst. The main purpose of this research work is to modify fish scales, cow bones, and eggshells as environmentally benign catalysts to have a large surface area and high basicity to enhance the production of biodiesel from waste cooking oil feedstock. The catalyst production procedure will also be varied in terms of catalyst mix ratio, catalyst mix procedure and catalyst impregnation species. The best performing catalyst will be characterized by BET, XRD, XRF, SEM, TGA and CO2-TPD techniques. The transesterification reaction parameters will be specified for the best performing catalyst blend [catalyst dose, reaction temperature, stirring rate and reaction time, WCO to ethanol ratio] to determine the optimum conditions. GC-MS will be used to quantify the purity (FAME composition) of the produced biodiesel.

Neural network is a type of machine learning algorithm that is inspired by the structure and function of the human brain. It is composed of interconnected nodes or “neurons” that process information and make predictions based on that information. Neural networks are typically used for tasks such as classification, regression, and pattern recognition.

There are many different types of neural networks, but they all share some common characteristics. A typical neural network is composed of several layers of interconnected neurons, with each layer processing the output of the previous layer. The first layer is the input layer, which receives the data that the network is being trained on. The final layer is the output layer, which produces the network’s prediction. Neural networks can be a powerful tool for solving complex problems in a wide range of fields, from image recognition to natural language processing.

In this study, CO2 capture, and neural network meet to recognize patterns that exist between solvent structures and their stability performance. Understanding these patterns can be the key to predicting the stability of potential amines in the early stages of research, eliminating guess work, and improving productivity.

Carbon capture has been proposed as a viable method of lowering CO2 emissions. The most widely used technology is the use of amines to capture CO2. However, the strategy commonly encounters operational concerns due to the repeated use of an amine, which is amine degradation. Recognizing the amine’s stability prior to the start-up of the CO2  capture plant allows us to develop an effective degradation prevention strategy required to reduce or potentially eliminate degradation from the amine-based CO2 capture process. Furthermore, the structural correlation will aid in amine selection during the initial stages of building a CO2 capture unit, ensuring that only the least degradable amines are used.

The degradation experiment of 27 amines was performed to investigate the degradation rate of each amine type. The assessment of the relationship of amine structure comprising of amino (in non-cyclic and cyclic amines), alkyl (in non-cyclic and cyclic amines), and hydroxyl groups and their linkages, reactivity and amine degradation rate was carried out. Information from this data was further used to developed the mathematical model using multiple linear regression to predict the amine degradation rate. The developed model was produced with a 22% AAD accuracy.

In this work, the degradation rate predictive model will be using machine learning regression with additional assumptions, other measurement criteria, alternative data cleaning techniques, or even incorporated ensemble learning to increase the model’s reliability over our previous degradation model by lowering overall error for greater accuracy.

The development of catalysts for post-combustion carbon capture is important for reducing greenhouse gas emissions and addressing the challenge of climate change. Catalysts can improve the efficiency of Carbon (IV) Oxide capture, and reduce the energy requirements and costs associated with the process; making it more economically viable. One approach being explored is the use of heterogeneous solid catalysts in combination with amine-based chemical absorption post-combustion capture.

The focus of this research is to develop heterogeneous solid catalysts that improve the carbon dioxide absorption capacity of a novel amine bi-blend solvent and to assess its impact on a system designed to obtain net zero through the indirect co-combustion of natural gas with biomass. The catalysts would be synthesized to have a high specific surface area, large pore volume, and a high number of basic sites, making them ideal for enhancing Carbon dioxide capture kinetics. This would involve; an informed catalyst selection process, catalyst synthesis, characterization of the developed catalyst, screening, optimization and data analysis carried out on the performance of the catalyst as applied to a bench-scale pilot plant.

To test the effectiveness of these catalysts, however, a laboratory batch-scale Carbon dioxide screening apparatus will be used to evaluate the carbon dioxide removal activity of each catalyst. The synthesized catalysts will also be characterized using various techniques such as Braeuer-Emmett-Teller (BET) to determine physical properties, Temperature programmed desorption (TPD) to determine basicity, and X-Ray diffraction analysis (XRD) to determine the crystallographic structure and chemical composition. Finally, the Carbon dioxide capture ability of the superbase catalyst and its impact on net zero will be systematically examined under operational settings in a bi-blend amine solvent.

By introducing the catalyst, one could potentially increase the efficiency of the carbon capture system, leading to a reduction in carbon emissions and a more effective move towards carbon neutrality or carbon negativity. The specific impact of the catalyst on net zero would also depend on the specific characteristics of the system and the type of catalyst used. In the design, one thing to consider would also be the cost-effectiveness and scalability of the technology when retrofitting an existing one.

This information is essential for conducting an optimization study of the catalyst and enhancing its performance in post-combustion carbon capture processes which involve the indirect co-combustion of biomass and natural gas.

Studies on various means of reducing CO2 emission or on the capture, storage and sequestration of emitted CO2 have been conducted to provide mitigation measures for greenhouse-induced temperature increases from a medium-and long-term perspective (Jang et al., 2016). The majority of currently available technologies include the utilization of CO2 in the manufacturing of chemicals, fuels, and fire extinguishers, as well as the injection of CO2 into oil reservoirs to improve oil recovery (CO2-EOR) (IEA 2019). Henceforth, utilizing captured CO2 in a process that yields valuable materials has consequently recently attracted a lot of attention. One of the prime examples is the sequestration of CO2 by mineral carbonation and transformation into an industrially useful product. (Jang et al., 2016).

CO2 can be utilized as an input in concrete making process. CO2-derived concrete could be used for the same applications as conventional concrete, provided the material properties are similar or better. Concrete is made by combining cement, water, and various types of solid aggregates (such as sand, gravel, and crushed stone) in a mixing container. CO2 can be utilized a s a component of the filler (aggregate), as a feedstock in the production of the binding material (cement), and as an input for the curing of concrete. The formation of carbonates, which are the type of carbon that is found in concrete, is the result of the reaction of CO2 with certain minerals, such as calcium oxide or magnesium oxide. (ICEF 2017_roadmap1, n.d.).

The term “curing” refers to a series of processes that take place in concrete after it has been mixed with water, cement, and aggregates. Cement is transformed into crystals that interlock with one another and bind the components of concrete together during this process. This gives the material the its strength. By injecting CO2 as part of the concrete mixing process, water is replaced by CO2 to produce calcium carbonate. In point of fact, this process takes place naturally in regular concrete, but at a very slow rate. This is because the CO2 in the air only penetrates the concrete at a rate of a couple of millimeters per year (Ecofys, 2017).

In order to solve this problem of inefficient CO2 uptake by concrete, the CO2-rich aqueous ionic liquid will then be utilized directly in a cement-based material such as concrete. This could reduce the amount of cement needed in the concrete mixture, thus leading to reduced energy consumption and CO2 emission from the production of cement. Other potential benefits are shorter curing time, less water consumption and a higher strength of concrete compared to conventional concrete.

As we look at minimizing the cost of CO2 capture process by removing the desorption unit and its ancillary equipment, there is also a need to pay attention to the size of the absorption column as it equally translates into cost. Smaller absorption columns result in minimal cost compared to bigger absorption columns. This is where the application of catalysts come into play in CO2 capture. Since the introduction of catalysts to CO2 absorption by our research group, the focus of CO2 capture has geared towards developing the best catalyst that possess good characteristics and gives the best performance as well. In looking out for catalysts with best characteristics and performance, it is expedient that we understand how the catalyst works in order to achieve the best performance.

As proposed by Caplow in 1967, carbamate formation is the rate determining step of the reaction mechanism of CO2 absorption. In the rate limiting step of the non-catalyzed process, a molecule of the amine in the solution has to donate an electron pair to the zwitterion to form a stable carbamate and a protonated amine. The reaction is represented as:

RN+H2COO– + RNH2  <->  RNHCOO– + RH3+

However, in the catalyzed process, the catalyst being used for the absorption process, which is principally a Lewis base (electron pair donor) comes in to replace the amine which donates the electron pair to the zwitterion. The catalyst then quickly donates an electron pair to the zwitterion instead of waiting for the amine to do so. This helps to speed up the carbamate formation process, providing an alternate route with lower activation energy. At the end of the process, the catalyst helps to boost the CO2 loading causing the rich loading of the catalyzed process to be higher than the non-catalyzed process as well as the initial absorption rate.

At the end of this work, CO2 emissions from large point sources would be reduced by capturing it using an ionic solvent at a faster rate with the help of the catalyst. The rich ionic solvent (ionic solvent + CO2) would then be utilized in the cement industry to replace the water content in mortar, concrete and grout.

Concerns about climate change have intensified as human and industrial activities continue to emit increasing amounts of carbon emissions. There has been an urgent need to explore and develop techniques to reduce emissions and/or achieve net-zero greenhouse gas emissions in order to resolve this issue and restore balance.

One of the results of this pursuit is the birth of the carbon capturing technology, a process which aids in capturing CO2 directly from power plants or industrial facilities before it enters into the atmosphere. Of the three methods employed in this endeavour, solvent-based post combustion carbon capture has become widely accepted due to its cost-effectiveness and efficiency in removing CO2 from flue gases. Additionally, its ease of integration into existing power plants without major changes have made it highly desirable.

Given that amine-based solvents offer a lower energy requirement, a high CO2 removal efficiency, and swift kinetics, among other advantages, they have emerged as one of the most successful solvents for the capture of carbon from these point sources. There has been further study on amine solvent blending to optimize its kinetics and performance for the carbon capture process.

The focus of this study is to evaluate the performance and kinetics of a novel amine blend, earlier developed by an elite member of the group, in post combustion-based carbon capture processes.  Specifically, this research shall be carried out using a bench scale pilot plant in an attempt to mimic the solvent blend’s performance and kinetics in a miniature industrial setup using laboratory simulated flue gas from the combustion of biomass and natural gas. The research will focus on analysing how different configurations and operational parameters (e.g., temperature, pressure, reactant concentrations) affect the carbon removal efficiency. This includes understanding how various physical and chemical properties (such as reaction kinetics) influence their effectiveness at capturing CO2 from selected point sources.