A carbon molecular sieve membrane-based reactive separation process for pre-combustion CO2 capture

Zeolite Membrane-Based Low-Temperature Dehydrogenation of a Liquid Organic Hydrogen Carrier: A Key Step in the Development of a Hydrogen Economy

Methylcyclohexane (MCH) dehydrogenation is an equilibrium-limited reaction that requires high temperatures (>300 °C) for complete conversion. However, high-temperature operation can degrade catalytic activity and produce unwanted side products. Thus, a hybrid zeolite membrane (Z) is prepared on the inner surface of a tubular support and used it as a wall in a membrane reactor (MR) configuration. Pt/C catalysts is packed diluted with quartz sand inside the Z-coated tube and applied the MR for MCH dehydrogenation at low temperatures (190-250 °C). Z showed a remarkable H2-permselectivity in the presence of both toluene and MCH, yielding separation factors over 350. The Z-based MR achieved higher MCH conversion (75.3% ± 0.8% at 220 °C) than the conventional packed-bed reactor (56.4% ± 0.3%) and the equilibrium state (53.2%), owing to the selective removal of H2 through Z. In summary, the hybrid zeolite MR enhances MCH dehydrogenation at low temperatures by overcoming thermodynamic limitations and improves the catalytic performance and product selectivity of the reaction.

Field-Scale Testing of a High-Efficiency Membrane Reactor (MR)-Adsorptive Reactor (AR) Process for H2 Generation and Pre-Combustion CO2 Capture

The study objective was to field-validate the technical feasibility of a membrane- and adsorption-enhanced water gas shift reaction process employing a carbon molecular sieve membrane (CMSM)-based membrane reactor (MR) followed by an adsorptive reactor (AR) for pre-combustion CO2 capture. The project was carried out in two different phases. In Phase I, the field-scale experimental MR-AR system was designed and constructed, the membranes, and adsorbents were prepared, and the unit was tested with simulated syngas to validate functionality. In Phase II, the unit was installed at the test site, field-tested using real syngas, and a technoeconomic analysis (TEA) of the technology was completed. All project milestones were met. Specifically, (i) high-performance CMSMs were prepared meeting the target H2 permeance (>1 m3/(m2.hbar) and H2/CO selectivity of >80 at temperatures of up to 300 °C and pressures of up to 25 bar with a <10% performance decline over the testing period; (ii) pelletized adsorbents were prepared for use in relevant conditions (250 °C < T < 450 °C, pressures up to 25 bar) with a working capacity of >2.5 wt.% and an attrition rate of <0.2; (iii) TEA showed that the MR-AR technology met the CO2 capture goals of 95% CO2 purity at a cost of electricity (COE) 30% less than baseline approaches.

Mitigation approaches and techniques for combustion power plants flue gas emissions: A comprehensive review

Population growth and urbanization are driving energy demand. Despite the development of renewable energy technologies, most of this demand is still met by fossil fuels. Flue gases are the main air pollutants from combustion power plants. These pollutants include particulate matter (PM), sulfur oxides (SOx), nitrogen oxides (NOx), and carbon oxides (COx). The release of these pollutants has adverse effects on human health and the environment, including serious damage to the human respiratory system, acid rain, climate change, and global warming. In this review, a wide range of conventional and new technologies that have the potential to be used in the combustion power plant sector to manage and reduce flue gas pollutants have been examined. Nowadays, conventional approaches to emissions control and management, which focus primarily on post-combustion techniques, face several challenges despite their widespread use and commendable effectiveness. Therefore, studies that have proposed alternative approaches to achieve improved and more efficient methods are reviewed. The results show that new advances such as novel PM collectors, attaining an efficiency of nearly 100 % for submicron particles, microwave systems, boasting an efficiency of nearly 90 % for NO and over 95 % for SO2, electrochemical systems achieving above 90 % efficiency for NOx reduction, non-thermal plasma processes demonstrating an efficiency close to 90 % for NOx, microalgae-based methods with efficiency ranging from 80 % to 99 % for CO2, and wet scrubbing, exhibit considerable potential in addressing the shortcomings of conventional systems. Furthermore, the integration of hybrid methods, particularly in regions prioritizing environmental concerns over economic considerations, holds promise for enhanced control and removal of flue gas pollutants with superior efficiency.

Carbon Capture Materials in Post-Combustion: Adsorption and Absorption-Based Processes

Global warming and climate changes are among the biggest modern-day environmental problems, the main factor causing these problems is the greenhouse gas effect. The increased concentration of carbon dioxide in the atmosphere resulted in capturing increased amounts of reflected sunlight, causing serious acute and chronic environmental problems. The concentration of carbon dioxide in the atmosphere reached 421 ppm in 2022 as compared to 280 in the 1800s, this increase is attributed to the increased carbon dioxide emissions from the industrial revolution. The release of carbon dioxide into the atmosphere can be minimized by practicing carbon capture utilization and storage methods. Carbon capture utilization and storage (CCUS) has four major methods, namely, pre-combustion, post-combustion, oxyfuel combustion, and direct air capture. It has been reported that applying CCUS can capture up to 95% of the produced carbon dioxide in running power plants. However, a reported cost penalty and efficiency decrease hinder the wide applicability of CCUS. Advancements in the CCSU were made in increasing the efficiency and decreasing the cost of the sorbents. In this review, we highlight the recent developments in utilizing both physical and chemical sorbents to capture carbon. This includes amine-based sorbents, blended absorbents, ionic liquids, metal-organic framework (MOF) adsorbents, zeolites, mesoporous silica materials, alkali-metal adsorbents, carbonaceous materials, and metal oxide/metal oxide-based materials. In addition, a comparison between recently proposed kinetic and thermodynamic models was also introduced. It was concluded from the published studies that amine-based sorbents are considered assuperior carbon-capturing materials, which is attributed to their high stability, multifunctionality, rapid capture, and ability to achieve large sorption capacities. However, more work must be done to reduce their cost as it can be regarded as their main drawback.

Update on air pollution control strategies for coal-fired power plants

ABSTRACT

Coal is expected to remain a significant power supply source worldwide and shifting to carbon-neutral fuels will be challenging because of growing electricity demand and booming industrialization. At the same time, coal consumption results in severe air pollution and health concerns. Improvement in emission control technologies is a key to improving air quality in coal power plants. Many scientists reported removing air pollutants individually via conventional control methods. However, controlling multiple pollutants combinedly using the latest techniques is rarely examined. Therefore, this paper overviews the current and advanced physical technologies to control multi-air pollutants synergistically, including carbon control technologies. Also, the paper aims to examine how potential air pollutants (e.g., PM_2.5, SO₂, NOx, CO₂), including mercury from the coal-fired power plants, cause environmental impacts. The data synthesis shows that coal quality is the most significant factor for increasing air emissions, regardless of power plant capacity. It is found that selecting techniques is critical for new and retrofitted plants depending on the aging of a power plant and other socio-economic factors. Considering the future perspective, this paper discusses possible pathways to transform from linear to a circular economy in a coal power plant sector, such as utilizing energy losses through energy-efficient processes and reuse of syngas. The article provides an in-depth analysis of advanced cost-effective techniques that would help to control the air pollution level. Additionally, a life cycle assessment-based decision-making framework is proposed that would assist the stakeholders in achieving net-zero emissions and offset the financial burden for air pollution control in coal-fired power plants.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10098-022-02328-8.

On Process Intensification through Membrane Storage Reactors

In this work, a dynamic, one-dimensional, first principle-based model of a novel membrane storage reactor (MSR) process is developed and simulated. The resulting governing equations are rendered dimensionless and are shown to feature two dimensionless groups that can be used to affect process performance. The novel process is shown to intensify production of a desired species through the creation of two physically distinct domains separated by a semipermeable boundary, and dynamic operation. A number of metrics are then introduced and applied to a case study on Steam Methane Reforming, for which a parametric study is carried out which establishes the superior performance of the MSR when compared to a reactor operating at steady state (SSR).