This study aims to explore more sustainable ammonia production routes for urea and ammonium nitrate fertilizers to support the rising global food demand and help achieve the Net Zero Emissions ...scenario by 2050. The research uses process modelling tools and Life Cycle Assessment methodology to evaluate the technical and environmental performance of green ammonia production compared to blue ammonia production, both pathways coupled with urea and ammonium nitrate production processes. The blue ammonia scenario uses steam methane reforming for H
production, while the sustainable approach scenarios consider water electrolysis with renewable resources (i.e., wind, hydro and photovoltaics) and nuclear power as a carbon-free source for H
generation. The study assumes an annual productivity of 450,000 tons for both urea and ammonium nitrate. The environmental assessment uses mass and energy balance data derived from process modelling and simulation. A cradle-to-gate environmental evaluation is conducted using GaBi software and the Recipe 2016 impact assessment method. Results show that green ammonia production requires less raw materials but has higher energy consumption due to electrolytic H
production (i.e., >90% of total energy requirements). The use of nuclear power achieves the highest reduction in global warming potential (i.e., 5.5 times for urea and 2.5 times for ammonium nitrate production processes), while hydro power coupled with electrolytic H
production shows lower environmental impacts in most categories (i.e., six out of ten impact categories). Overall, the sustainable scenarios prove to be suitable alternatives for fertilizer production towards achieving a more sustainable future.
As global power generation is currently relying on fossil fuel-based power plants, more anthropogenic CO2 is being released into the atmosphere. During the transition period to alternative energy ...sources, carbon capture and storage seems to be a promising solution. Chemical-looping combustion (CLC) is an energy conversion technology designed for combustion of fossil fuel with advantageous carbon capture capabilities. In this work, a 1D computational fluid dynamics (CFD) multiscale model was developed to study the reduction step in a syngas-based CLC system and was validated using literature data (R=0.99). In order to investigate mass transfer effects, flow rate and particle dimension studies were carried out. Sharper mass transfer rates were seen at lower flow rates and smaller granule sizes due to suppression of diffusion limitations. In addition, a 3D CFD particle model was developed to investigate in depth the reduction within an ilmenite particle, with focus on heat transfer effects. Minor differences of 1 K were seen when comparing temperature changes predicted by the two models during the slightly exothermic reduction reaction with syngas.
Membrane technology is considered an innovative and promising approach due to its flexibility and low energy consumption. In this work, a comprehensive 3D-CFD model of the Hollow-Fiber Membrane ...Contactor (HFMC) system for CO2 capture into aqueous MEA solution, considering a counter-current fluid flow, was developed and validated with experimental data. Two different flow arrangements were considered for the gas mixture and liquid solution inside the HFMC module. The simulation results showed that the CO2 absorption efficiency was considerably higher when the gas mixture was channeled through the membranes and the liquid phase flowed externally between the membranes, across a wide range of gas and liquid flow rates. Sensitivity studies were performed in order to determine the optimal CO2 capture process parameters under different operating conditions (flow rates/flow velocities and concentrations) and HFMC geometrical characteristics (e.g., porosity, diameter, and thickness of membranes). It was found that increasing the membrane radius, while maintaining a constant thickness, positively influenced the efficiency of CO2 absorption due to the higher mass transfer area and residence time. Conversely, higher membrane thickness resulted in higher mass transfer resistance. The optimal membrane thickness was also investigated for various inner fiber diameters, resulting in a thickness of 0.2 mm as optimal for a fiber inner radius of 0.225 mm. Additionally, a significant improvement in CO2 capture efficiency was observed when increasing membrane porosity to values below 0.2, at which point the increase dampened considerably. The best HFMC configuration involved a combination of low porosity, moderate thickness, and large fiber inner diameter, with gas flow occurring within the fiber membranes.
Chemical looping combustion (CLC) offers innovative carbon capture via oxygen carrier (OC) circulation between separate reactors. Circulating fluidized beds facilitate OC transport between fuel and ...air reactors for reduction and oxidation. By avoiding direct contact between fuel and air, minimal energy is required for CO
2
separation. Disadvantages resulting from the conventional circulating fluidized bed system are the additional energy necessary for OC transportation and the challenge to operate at elevated pressure. A novel approach to CLC is proposed by considering a packed bed system with stationary OC particles undergoing periodic reduction and oxidation stages by shifting feed gas streams. The major design benefit lies in the prospect of process operation at high pressure. Finding optimal operating conditions is a mandatory step prior to implementing the process at industrial level. In this work, COMSOL Multiphysics was used for computational fluid dynamics (CFD) modelling in order to simulate the syngas-based CLC process with ilmenite OC in a packed bed reactor configuration. Mass, momentum and heat transfer mechanisms were accounted for to describe the combustion, purge and regeneration stages within a bed of randomly packed spherical OC particles at both macro- and micro-scale dimensions. The scope of the particle-resolved CFD multiscale model with realistic bed morphology was the in-depth analysis of the intraparticle phenomena occurring during the redox reactions, with emphasis on heat transport. Model results agree with published literature and provide additional understanding regarding the process in order to contribute towards the design of a flexible and energy efficient power plant concept.
Graphical abstract
Modelling syngas-based CLC steps considering a realistic packed bed morphology for ilmenite OC conversion
The current study aims to assess the performance and industrial feasibility of using three-phase fluidized bed absorption columns for post-combustion carbon dioxide (CO2) capture. The analysis is ...based on a mathematical model of a scaled-up fluidized bed absorption column that has been validated using pilot plant experimental data. The focus is on evaluating the energy efficiency of the fluidized bed column in comparison to packed bed technologies, which are currently widely used. The results of the analysis are evaluated in terms of three performance indicators (i.e., absorption efficiency, carbon capture rate, and energy performance index) and compared to packed bed columns. Simulation results indicate that the best column configuration is represented by a three-stage absorber and that the system performs optimally when particle diameter and density decrease with each section. Consequently, this leads to an increase in the total fluidized bed height and carbon capture rate by up to 25%. The energy performance index is maintained below 3.6, indicating an energy-efficient operation of the system. As such, the findings of this study suggest that the use of gas-solid-liquid three-phase fluidized bed absorption columns for post-combustion CO2 capture is a promising technology for the implementation of CCUS and for achieving of climate neutrality targets.
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•Mathematical modeling through experimental assessment.•Consideration of a three phase, gas-solid-liquid, fluidized bed absorber for carbon capture.•Integration of gas-solid-liquid fluidized bed absorber in a full-scale carbon capture plant.•Performance analysis of three phase absorption in terms of energy and carbon capture efficiency.•Comparison of the obtained performance with the one obtained using regular packed bed absorbers.
•Validated CFD multiscale packed bed reactor model for CO2 adsorption in SEWGS.•Validated 3D-printed CFD bench-scale monolith model for CO2 adsorption in SEWGS.•Theoretical comparison between ...monolith and packed bed for SEWGS productivity.
Sorption Enhanced Water-Gas Shift (SEWGS) couples the water gas-shift reaction with CO2 adsorption on potassium-promoted hydrotalcite (K-HTC) sorbent material for hydrogen production and CO2 capture. Here, computational fluid dynamics (CFD) models are developed to simulate the adsorption step in SEWGS considering both packed bed and monolith reactors. The goal of this research is increasing SEWGS productivity by using 3D-printed structured bed reactors, as opposed to conventional packed bed reactors, due to the well-known advantages of monoliths, such as less mass transfer limitations and lower pressure drops. The paper presents numerical modeling and simulation work supported by experimental validation in order to compare packed bed and monolith reactors with respect to SEWGS performance. The packed bed multiscale CFD model is validated using breakthrough experimental data. A bench-scale CFD structured bed model is developed and validated based on breakthrough measurements performed by TNO using 3D-printed K-HTC monolith structures. Furthermore, geometry effects on mass transfer efficiency are investigated through CFD modeling for the bench-scale reactor. A scale-up of the monolith model to pilot-scale allows for a proper comparison with the packed bed technology. Monolith reactor model breakthrough predictions show there is a considerable increase in mass transfer rate over the packed bed reactor for the adsorption step in SEWGS, demonstrating promising potential towards enhancing the carbon capture technology.
Integrated Gasification Combined Cycle (IGCC) design represents a versatile electricity production method with key advantages for decarbonization. Carbon capture, utilization and storage methods are ...predicted to perform an essential role in reducing CO2 emissions. In this paper, two innovative reactive gas-solid systems are assessed in pre-combustion designs for gasification plant decarbonization. The most essential mass & energy integration issues for a decarbonized coal gasification power plant by innovative chemical & calcium looping systems are evaluated. The designs produce roughly 435–592 MW net electricity outputs having an adjustable hydrogen production (up to 200 MW thermal output) and a plant decarbonization degree higher than 90%. The prominent aim of this analysis is put on assessment of mass and energy integration elements to raise global energy conversion yield. The evaluation includes thermal integration of plant units and performing flexibility analysis. The overall conclusion is that gasification technology coupled with innovative chemical & calcium looping cycles proves to be very promising to deliver higher energy efficiency (up to 1.3 net percentage points), carbon capture rate (96–99% vs. 90%) and better economics and operational flexibility compared to Selexol™ gas-liquid absorption.
•Energy integration analysis for gasification plants with chemical looping cycles.•Higher energy efficiency of chemical looping cycles than gas-liquid absorption.•Superior CO2 capture rate of chemical looping cycles than gas-liquid absorption.•Energy and economic improvements by better thermal and air integration measures.•Flexible hydrogen and power co-generation using syngas-based looping cycles.
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