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Gas switching reforming (GSR) is a promising technology for natural gas reforming with inherent CO2 capture. Like conventional steam methane reforming (SMR), GSR can be integrated with water-gas shift and pressure swing adsorption units for pure hydrogen production. The resulting GSR-H2 process concept was techno-economically assessed in this study. Results showed that GSR-H2 can achieve 96% CO2 capture at a CO2 avoidance cost of 15 $/ton (including CO2 transport and storage). Most components of the GSR-H2 process are proven technologies, but long-term oxygen carrier stability presents an important technical uncertainty that can adversely affect competitiveness when the material lifetime drops below one year. Relative to the SMR benchmark, GSR-H2 replaces some fuel consumption with electricity consumption, making it more suitable to regions with higher natural gas prices and lower electricity prices. Some minor alterations to the process configuration can adjust the balance between fuel and electricity consumption to match local market conditions. The most attractive commercialization pathway for the GSR-H2 technology is initial construction without CO2 capture, followed by simple retrofitting for CO2 capture when CO2 taxes rise, and CO2 transport and storage infrastructure becomes available. These features make the GSR-H2 technology robust to almost any future energy market scenario.
Shareq Mohd Nazir; Jan Hendrik Cloete; Schalk Cloete; Shahriar Amini. Pathways to low-cost clean hydrogen production with gas switching reforming. International Journal of Hydrogen Energy 2020, 46, 20142 -20158.
AMA StyleShareq Mohd Nazir, Jan Hendrik Cloete, Schalk Cloete, Shahriar Amini. Pathways to low-cost clean hydrogen production with gas switching reforming. International Journal of Hydrogen Energy. 2020; 46 (38):20142-20158.
Chicago/Turabian StyleShareq Mohd Nazir; Jan Hendrik Cloete; Schalk Cloete; Shahriar Amini. 2020. "Pathways to low-cost clean hydrogen production with gas switching reforming." International Journal of Hydrogen Energy 46, no. 38: 20142-20158.
Integrated gasification combined cycles (IGCC) are promising power production systems from solid fuels due to their high efficiency and good environmental performance. Chemical looping combustion (CLC) is an effective route to reduce the energy penalty associated with CO2 capture. This concept comprises a metal oxygen carrier circulated between a reduction reactor, where syngas is combusted, and an oxidation reactor, where O2 is withdrawn from an air stream. Parallel to CLC, oxygen carriers that are capable of releasing free O2 in the reduction reactor, i.e., chemical looping oxygen production (CLOP), have been developed. This offers interesting integration opportunities in IGCC plants, replacing energy demanding air separation units (ASU) with CLOP. Gas switching (GS) reactor cluster technology consists of a set of reactors operating in reduction and oxidation stages alternatively, providing an averaged constant flow rate to the gas turbine and a CO2 stream readily available for purification and compression, and avoiding the transport of solids across reactors, which facilitates the scale up of this technology at pressurized conditions. In this work, exergy analyses of a gas switching combustion (GSC) IGCC plant and a GSOP–GSC IGCC plant are performed and consistently benchmarked against an unabated IGCC and a precombustion CO2 capture IGCC plant. Through the exergy analysis methodology, an accurate assessment of the irreversible loss distribution in the different power plant sections from a second-law perspective is provided, and new improvement pathways to utilize the exergy contained in the GSC reduction gases outlet are identified.
Carlos Arnaiz Del Pozo; Angel Jiménez Álvaro; Jan Hendrik Cloete; Schalk Cloete; Shahriar Amini; Cloete. Exergy Analysis of Gas Switching Chemical Looping IGCC Plants. Energies 2020, 13, 544 .
AMA StyleCarlos Arnaiz Del Pozo, Angel Jiménez Álvaro, Jan Hendrik Cloete, Schalk Cloete, Shahriar Amini, Cloete. Exergy Analysis of Gas Switching Chemical Looping IGCC Plants. Energies. 2020; 13 (3):544.
Chicago/Turabian StyleCarlos Arnaiz Del Pozo; Angel Jiménez Álvaro; Jan Hendrik Cloete; Schalk Cloete; Shahriar Amini; Cloete. 2020. "Exergy Analysis of Gas Switching Chemical Looping IGCC Plants." Energies 13, no. 3: 544.
This work presents a novel integrated gasification combined cycle (IGCC) power plant configuration for CO2 capture with minimal energy penalty. The proposed oxygen production pre-combustion (OPPC) power plant synergistically integrates a gas switching oxygen production (GSOP) unit into a pre-combustion IGCC power plant, reducing the energy penalty through two channels: 1) avoidance of a cryogenic air separation unit and 2) pre-heating the air sent to the combined power cycle, which reduces the steam requirement for shifting CO to H2 and the CO2 capture duty involved in pre-combustion CO2 capture. Relative to a conventional pre-combustion IGCC benchmark, the OPPC configuration improves the electric efficiency by about 6%-points, although the CO2 capture ratio reduces by about 6%-points. OPPC as avoids the maximum temperature limitation of Chemical Looping Combustion based plants, and can therefore benefit from efficient modern gas turbine technology operating at very high inlet temperatures. CO2 removal via physical absorption (Selexol) generally results in higher efficiencies, but lower CO2 avoidance than chemical absorption (MDEA). Plant efficiency also benefits from an increase in GSOP operating temperature, although the maximum temperature was limited to 900 °C to avoid any temperature-related challenges with oxygen carrier stability or downstream valves and filters. OPPC therefore appears to be a promising configuration for minimizing the energy penalty of CO2 capture in IGCC power plants, combining well known and proven technology blocks with a GSOP reactor cluster instead of an ASU.
Carlos Arnaiz del Pozo; Schalk Cloete; Jan Hendrik Cloete; Ángel Jiménez Álvaro; Shahriar Amini. The oxygen production pre-combustion (OPPC) IGCC plant for efficient power production with CO2 capture. Energy Conversion and Management 2019, 201, 112109 .
AMA StyleCarlos Arnaiz del Pozo, Schalk Cloete, Jan Hendrik Cloete, Ángel Jiménez Álvaro, Shahriar Amini. The oxygen production pre-combustion (OPPC) IGCC plant for efficient power production with CO2 capture. Energy Conversion and Management. 2019; 201 ():112109.
Chicago/Turabian StyleCarlos Arnaiz del Pozo; Schalk Cloete; Jan Hendrik Cloete; Ángel Jiménez Álvaro; Shahriar Amini. 2019. "The oxygen production pre-combustion (OPPC) IGCC plant for efficient power production with CO2 capture." Energy Conversion and Management 201, no. : 112109.
Limiting global temperature rise to well below 2 °C according to the Paris climate accord will require accelerated development, scale-up, and commercialization of innovative and environmentally friendly reactor concepts. Simulation-based design can play a central role in achieving this goal by decreasing the number of costly and time-consuming experimental scale-up steps. To illustrate this approach, a multiscale computational fluid dynamics (CFD) approach was utilized in this study to simulate a novel internally circulating fluidized bed reactor (ICR) for power production with integrated CO2 capture on an industrial scale. These simulations were made computationally feasible by using closures in a filtered two-fluid model (fTFM) to model the effects of important subgrid multiphase structures. The CFD simulations provided valuable insight regarding ICR behavior, predicting that CO2 capture efficiencies and purities above 95% can be achieved, and proposing a reasonable reactor size. The results from the reactor simulations were then used as input for an economic evaluation of an ICR-based natural gas combined cycle power plant. The economic performance results showed that the ICR plant can achieve a CO2 avoidance cost as low as $58/ton. Future work will investigate additional firing after the ICR to reach the high inlet temperatures of modern gas turbines.
Jan Hendrik Cloete; Mohammed N. Khan; Schalk Cloete; Shahriar Amini. Simulation-Based Design and Economic Evaluation of a Novel Internally Circulating Fluidized Bed Reactor for Power Production with Integrated CO2 Capture. Processes 2019, 7, 723 .
AMA StyleJan Hendrik Cloete, Mohammed N. Khan, Schalk Cloete, Shahriar Amini. Simulation-Based Design and Economic Evaluation of a Novel Internally Circulating Fluidized Bed Reactor for Power Production with Integrated CO2 Capture. Processes. 2019; 7 (10):723.
Chicago/Turabian StyleJan Hendrik Cloete; Mohammed N. Khan; Schalk Cloete; Shahriar Amini. 2019. "Simulation-Based Design and Economic Evaluation of a Novel Internally Circulating Fluidized Bed Reactor for Power Production with Integrated CO2 Capture." Processes 7, no. 10: 723.
Shareq Mohd Nazir; Jan Hendrik Cloete; Schalk Cloete; Shahriar Amini. Efficient hydrogen production with CO2 capture using gas switching reforming. Energy 2019, 185, 372 -385.
AMA StyleShareq Mohd Nazir, Jan Hendrik Cloete, Schalk Cloete, Shahriar Amini. Efficient hydrogen production with CO2 capture using gas switching reforming. Energy. 2019; 185 ():372-385.
Chicago/Turabian StyleShareq Mohd Nazir; Jan Hendrik Cloete; Schalk Cloete; Shahriar Amini. 2019. "Efficient hydrogen production with CO2 capture using gas switching reforming." Energy 185, no. : 372-385.
Filtered Two Fluid Models (fTFMs) aim to enable accurate industrial-scale simulations of fluidized beds by means of closures accounting for the effects of bubbles and clusters. The present study aims to improve anisotropic closures for the drift velocity, which is the primary sub-grid effect altering the filtered drag force, by deriving increasingly complex closures by considering additional independent variables (markers). Three different anisotropic closures, as well as an isotropic closure, are evaluated. A priori tests revealed a significant increase in the predictive capability of the closures as the complexity, in terms of the number of markers considered, increases. However, this improvement is relatively small when compared to the effect of considering anisotropy. Next, a posteriori tests were completed by comparing coarse-grid simulations of bubbling, turbulent and core-annular fluidization against benchmark resolved TFM simulations. This analysis shows good performance of all anisotropic closures, with negligible to minor effects of increasing the drag closure’s complexity by considering additional markers. On the other hand, the isotropic closure lacks generality and shows poor grid independence behaviour. It is therefore concluded that it is essential to include important physical effects, such as anisotropy, in fTFM closures, while complexity in terms of the number of markers considered is of lesser importance.
Jan Hendrik Cloete; Schalk Cloete; Stefan Radl; Shahriar Amini. On the choice of closure complexity in anisotropic drag closures for filtered Two Fluid Models. Chemical Engineering Science 2019, 207, 379 -396.
AMA StyleJan Hendrik Cloete, Schalk Cloete, Stefan Radl, Shahriar Amini. On the choice of closure complexity in anisotropic drag closures for filtered Two Fluid Models. Chemical Engineering Science. 2019; 207 ():379-396.
Chicago/Turabian StyleJan Hendrik Cloete; Schalk Cloete; Stefan Radl; Shahriar Amini. 2019. "On the choice of closure complexity in anisotropic drag closures for filtered Two Fluid Models." Chemical Engineering Science 207, no. : 379-396.
Energy penalty is the primary challenge facing CO2 capture and storage (CCS) technology. One possible solution to this challenge is gas switching combustion (GSC): a promising technology for gaseous fuel combustion with integrated CO2 capture at almost no direct energy penalty. However, previous work showed that GSC integrated into an IGCC power plant still imposed an energy penalty of 5.7%-points relative to an unabated IGCC plant. This penalty originates mainly from the maximum temperature limitation of the GSC reactors and inefficient power production from the CO2-rich stream. Addressing these challenges via an additional combustor after the GSC reactors and improved heat integration successfully eliminated the aforementioned energy penalty, although feeding carbon-containing fuels to the additional combustor reduces the CO2 capture ratio. Furthermore, GSC presents two channels for exceeding the efficiency of an unabated benchmark plant: 1) the high steam partial pressure in the CO2-rich stream allows most of the steam condensation enthalpy to be recovered and 2) pre-combustion gas clean-up can potentially be replaced with post-combustion clean-up because pollutants remain concentrated in the CO2-rich stream. In combination, these effects can boost plant efficiency by a further 2%-points, exceeding the efficiency of an unabated IGCC plant. Ultimately, the most efficient plant evaluated in this study achieved 50.9% efficiency with 80.7% CO2 capture. The GSC-IGCC power plant can therefore solve the most fundamental challenge facing CCS and more detailed feasibility studies are strongly recommended.
Carlos Arnaiz del Pozo; Schalk Cloete; Jan Hendrik Cloete; Ángel Jiménez Álvaro; Shahriar Amini. The potential of chemical looping combustion using the gas switching concept to eliminate the energy penalty of CO2 capture. International Journal of Greenhouse Gas Control 2019, 83, 265 -281.
AMA StyleCarlos Arnaiz del Pozo, Schalk Cloete, Jan Hendrik Cloete, Ángel Jiménez Álvaro, Shahriar Amini. The potential of chemical looping combustion using the gas switching concept to eliminate the energy penalty of CO2 capture. International Journal of Greenhouse Gas Control. 2019; 83 ():265-281.
Chicago/Turabian StyleCarlos Arnaiz del Pozo; Schalk Cloete; Jan Hendrik Cloete; Ángel Jiménez Álvaro; Shahriar Amini. 2019. "The potential of chemical looping combustion using the gas switching concept to eliminate the energy penalty of CO2 capture." International Journal of Greenhouse Gas Control 83, no. : 265-281.
Models for predicting flows in large scale fluidized beds, such as filtered Two Fluid Models (fTFMs), must account for meso-scale phenomena that manifest spontaneously in sedimenting gas-particle suspensions. Next to the closures for interphase momentum exchange, the filtered solids stresses also require closure in such models. A budget analysis reveals that, for large filter sizes, the meso-scale solids stresses, which arise due to the particles’ sub-grid velocity fluctuations, are the most important contribution to these stresses. Previously, closures for meso-scale stresses have commonly adopted a Boussinesq approach where (i) a filtered solids pressure is used to close the mean normal stress, and (ii) a filtered solids viscosity is modelled to close the deviatoric stress components. The present study highlights that such a Boussinesq approach fails to accurately predict the forces arising from the meso-scale stresses. This is primarily due to the fundamental inability of a viscosity-based formulation to approximate deviatoric stress components in sedimenting gas-particle suspensions. The present study proposes a novel anisotropic approach in which both normal (i.e., diagonal) and shear (i.e., off-diagonal) stress components are modelled individually. The proposed anisotropic closure explains resolved stress data significantly more reliably (i.e., with a correlation coefficient of R2≈0.62R2≈0.62) compared to a conventional Boussinesq-based approach (R2≈-0.65)(R2≈-0.65) using a single model equation. Finally, these findings are confirmed by evaluating different stress closures in fTFM simulations of bubbling and turbulent fluidization. These simulations indicate that the novel anisotropic stress closure leads to improved model generality and better grid independence. Most important, it is found that a classical Boussinesq-based closure leads to worse predictions compared to a complete neglect of meso-scale solids stresses. Thereby, the present study underlines that it is essential to account for anisotropy when closing the meso-scale solids stress in fTFMs.
Jan Hendrik Cloete; Schalk Cloete; Stefan Radl; Shahriar Amini. Development and verification of anisotropic solids stress closures for filtered Two Fluid Models. Chemical Engineering Science 2018, 192, 906 -929.
AMA StyleJan Hendrik Cloete, Schalk Cloete, Stefan Radl, Shahriar Amini. Development and verification of anisotropic solids stress closures for filtered Two Fluid Models. Chemical Engineering Science. 2018; 192 ():906-929.
Chicago/Turabian StyleJan Hendrik Cloete; Schalk Cloete; Stefan Radl; Shahriar Amini. 2018. "Development and verification of anisotropic solids stress closures for filtered Two Fluid Models." Chemical Engineering Science 192, no. : 906-929.
Jan Hendrik Cloete; Schalk Cloete; Federico Municchi; Stefan Radl; Shahriar Amini. Development and verification of anisotropic drag closures for filtered Two Fluid Models. Chemical Engineering Science 2018, 192, 930 -954.
AMA StyleJan Hendrik Cloete, Schalk Cloete, Federico Municchi, Stefan Radl, Shahriar Amini. Development and verification of anisotropic drag closures for filtered Two Fluid Models. Chemical Engineering Science. 2018; 192 ():930-954.
Chicago/Turabian StyleJan Hendrik Cloete; Schalk Cloete; Federico Municchi; Stefan Radl; Shahriar Amini. 2018. "Development and verification of anisotropic drag closures for filtered Two Fluid Models." Chemical Engineering Science 192, no. : 930-954.
This paper presents the process improvement studies of a combined cycle power plant integrated with a novel gas switching reforming (GSR) process for hydrogen production with integrated CO2 capture. The overall process is denoted as GSR-CC (gas switching reforming-combined cycle). Five cases are presented in which a systematic approach was adopted to improve the net electrical efficiency of the GSR-CC process. Two cases focus on reducing the number of unit operations and the other three cases focus on heat integration. The net electrical efficiency of the base case GSR-CC process is 45.8% whereas the improved GSR-CC has a net electrical efficiency of 51.1%. The efficiency penalty in the improved GSR-CC process is only 7.2 %-points with respect to the reference case natural gas combined cycle power plant without CO2 capture, and is less than post-combustion capture methods presented in literature. The CO2 avoidance in the GSR-CC is more than 95%. GSR-CC also gives a flexibility in the output from the plant in terms of pure H2 or electricity and the optimal plant configuration is designed to maximize this flexibility.
Shareq Mohd Nazir; Jan Hendrik Cloete; Schalk Cloete; Shahriar Amini. Gas switching reforming (GSR) for power generation with CO2 capture: Process efficiency improvement studies. Energy 2018, 167, 757 -765.
AMA StyleShareq Mohd Nazir, Jan Hendrik Cloete, Schalk Cloete, Shahriar Amini. Gas switching reforming (GSR) for power generation with CO2 capture: Process efficiency improvement studies. Energy. 2018; 167 ():757-765.
Chicago/Turabian StyleShareq Mohd Nazir; Jan Hendrik Cloete; Schalk Cloete; Shahriar Amini. 2018. "Gas switching reforming (GSR) for power generation with CO2 capture: Process efficiency improvement studies." Energy 167, no. : 757-765.
This work presents a validation study of new filtered Two Fluid Model closures for interphase momentum exchange and mesoscale solids stresses. Good quantitative comparisons to experimental data were achieved over a wide range of fluidization velocities. The new models also showed good grid independence behaviour compared to two benchmark models from literature. These encouraging results in realistic 3D flows were achieved even though the models were derived from 2D resolved simulations. Comparisons to a benchmark model derived from 3D simulations suggests that it may be more accurate to derive filtered models from resolved simulations conducted in a large 2D domain than from resolved simulations in a small 3D domain. Furthermore, the new model validated in this work could achieve good results in wall-dominated flows without the use of specialized wall corrections. Further work is therefore recommended to test these new filtered models in more flow situations and to further assess the ability of filtered models derived in 2D to predict real 3D flows.
Schalk Cloete; Jan Hendrik Cloete; Shahriar Amini. Hydrodynamic validation study of filtered Two Fluid Models. Chemical Engineering Science 2018, 182, 93 -107.
AMA StyleSchalk Cloete, Jan Hendrik Cloete, Shahriar Amini. Hydrodynamic validation study of filtered Two Fluid Models. Chemical Engineering Science. 2018; 182 ():93-107.
Chicago/Turabian StyleSchalk Cloete; Jan Hendrik Cloete; Shahriar Amini. 2018. "Hydrodynamic validation study of filtered Two Fluid Models." Chemical Engineering Science 182, no. : 93-107.
Jan Hendrik Cloete; Schalk Cloete; Federico Municchi; Stefan Radl; Shahriar Amini. Corrigendum to “The sensitivity of filtered Two Fluid Model to the underlying resolved simulation setup” [Powder Technol. 316 (2017) 265–277]. Powder Technology 2018, 326, 498 .
AMA StyleJan Hendrik Cloete, Schalk Cloete, Federico Municchi, Stefan Radl, Shahriar Amini. Corrigendum to “The sensitivity of filtered Two Fluid Model to the underlying resolved simulation setup” [Powder Technol. 316 (2017) 265–277]. Powder Technology. 2018; 326 ():498.
Chicago/Turabian StyleJan Hendrik Cloete; Schalk Cloete; Federico Municchi; Stefan Radl; Shahriar Amini. 2018. "Corrigendum to “The sensitivity of filtered Two Fluid Model to the underlying resolved simulation setup” [Powder Technol. 316 (2017) 265–277]." Powder Technology 326, no. : 498.
Jan Hendrik Cloete; Schalk Cloete; Federico Municchi; Stefan Radl; Shahriar Amini. The sensitivity of filtered Two Fluid Model to the underlying resolved simulation setup. Powder Technology 2017, 316, 265 -277.
AMA StyleJan Hendrik Cloete, Schalk Cloete, Federico Municchi, Stefan Radl, Shahriar Amini. The sensitivity of filtered Two Fluid Model to the underlying resolved simulation setup. Powder Technology. 2017; 316 ():265-277.
Chicago/Turabian StyleJan Hendrik Cloete; Schalk Cloete; Federico Municchi; Stefan Radl; Shahriar Amini. 2017. "The sensitivity of filtered Two Fluid Model to the underlying resolved simulation setup." Powder Technology 316, no. : 265-277.
Jan Hendrik Cloete; Schalk Cloete; Stefan Radl; Shahriar Amini. Evaluation of wall friction models for riser flow. Powder Technology 2016, 303, 156 -167.
AMA StyleJan Hendrik Cloete, Schalk Cloete, Stefan Radl, Shahriar Amini. Evaluation of wall friction models for riser flow. Powder Technology. 2016; 303 ():156-167.
Chicago/Turabian StyleJan Hendrik Cloete; Schalk Cloete; Stefan Radl; Shahriar Amini. 2016. "Evaluation of wall friction models for riser flow." Powder Technology 303, no. : 156-167.
Jan Hendrik Cloete; G Akdogan; Sm Bradshaw; Dk Chibwe. Physical and numerical modelling of a four-strand steelmaking tundish using flow analysis of different configurations. Journal of the Southern African Institute of Mining and Metallurgy 2015, 115, 355 -362.
AMA StyleJan Hendrik Cloete, G Akdogan, Sm Bradshaw, Dk Chibwe. Physical and numerical modelling of a four-strand steelmaking tundish using flow analysis of different configurations. Journal of the Southern African Institute of Mining and Metallurgy. 2015; 115 (5):355-362.
Chicago/Turabian StyleJan Hendrik Cloete; G Akdogan; Sm Bradshaw; Dk Chibwe. 2015. "Physical and numerical modelling of a four-strand steelmaking tundish using flow analysis of different configurations." Journal of the Southern African Institute of Mining and Metallurgy 115, no. 5: 355-362.