| 1. |
- Saeed, Muhammad Nauman, 1995, et al.
(författare)
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Production of aviation fuel with negative emissions via chemical looping gasification of biogenic residues: Full chain process modelling and techno-economic analysis
- 2023
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 241
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Tidskriftsartikel (refereegranskat)abstract
- The second-generation bio aviation fuel production via Chemical Looping Gasification (CLG) of biomass combined with downstream Fischer-Tropsch (FT) synthesis is a possible way to decarbonize aviation sector. The CLG process has the advantage of producing undiluted syngas without the use of an air-separation unit (ASU) and improved syngas yield compared to the conventional gasification processes. This study is based on modelling the full chain process of biomass to liquid fuel (BtL) with LD-slag and Ilmenite as oxygen carriers using Aspen Plus software, validating the model results with experimental studies and carrying out a techno-economic analysis of the process. For the gasifier load of 80 MW based on LHV of fuel entering the gasifier, the optimal model predicts that the clean syngas has an energy content of 8.68 MJ/Nm3 with a cold-gas efficiency of 77.86%. The optimized model also estimates an aviation fuel production of around 340 bbl/day with 155 k-tonne of CO2 captured every year and conversion efficiency of biomass to FT-crude of 38.98%. The calculated Levelized Cost of Fuel (LCOF) is 35.19 $ per GJ of FT crude, with an annual plant profit (cash inflow) of 11.09 M$ and a payback period of 11.56 years for the initial investment.
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| 2. |
- Roshan Kumar, Tharun, 1995
(författare)
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Decarbonization in Carbon-Intensive Industries - An Assessment Framework for Enhanced Early-Stage Identification of Optimal Decarbonization Pathways
- 2024
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Carbon-intensive industries currently account for a quarter of global annual CO2 emissions. Achieving mandated climate targets necessitates the rapid implementation of decarbonization technologies in these industries. Such deployments typically involve substantial upfront investments amidst technical, economic, and policy uncertainties. Consequently, careful selection of decarbonization technologies or a combination thereof, coupled with measures like process electrification and energy efficiency, becomes increasingly crucial. In this context, numerous early-stage comparative assessment studies utilizing process integration and techno-economic methods to identify cost-optimal decarbonization technologies in unabated industries often overlook key considerations at the systems, plant, and site levels. This thesis presents limitations in existing methodological approaches for comparing decarbonization pathways, spanning systems, plant, and site-level considerations. A generalized hybrid assessment framework was developed that addresses these limitations with individual framework methodologies developed in the appended papers. At the systems level, extended boundaries and exergy as a metric were used to compare two CO2 capture technologies with inherently different exergy requirements per unit of CO2 captured, considering plant owner and end-user perspectives. At the plant level, an iterative exergy-pinch analysis combined with techno-economic analysis was developed to identify promising process modifications in unabated process plants that maximize overall exergy utilization and CO2 avoidance with successive designs towards net-zero emissions. Finally, a site-specific techno-economic analysis was developed incorporating site-specific factors expected to impact the final cost of CO2 avoidance. These frameworks were demonstrated with industrial case studies on bio-CHP in a district heating system, propane dehydrogenation, and steam cracker plant, respectively. The case study results show that preserving electric power in bio-CHP plants through the integration of amine-based CO2 capture technology, complemented with industrial heat pumps, would not only ensure a greater potential for district heat delivery but also provide greater product flexibility in terms of both heat and power production, and negative CO2 emissions. The iterative exergy-pinch analysis applied to the propane dehydrogenation plant revealed unconventional process modifications, resulting in a substantial reduction in CO2 avoidance cost (58–70%) compared to CO2 capture from the highly diluted flue gas stream from the unmodified process (167–181 €/tCO2). Finally, utilizing site-specific techno-economic analysis, the cost escalation due to site-specific factors, in terms of CO2 avoidance, was approximately 80% higher for the post-combustion CO2 capture process (43 €/tCO2) compared to the alternative of hydrogen-firing in the cracker furnaces, through the pre-combustion CO2 capture process (24 €/tCO2). These findings reveal that cost factors that are commonly neglected could significantly influence the choice of decarbonization technology at an early stage. In summary, the proposed assessment framework, combining these individual framework methodologies, can be utilized to obtain a comprehensive early-stage indication of the optimal decarbonization pathway for specific industrial sites.
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| 3. |
- Roshan Kumar, Tharun, 1995, et al.
(författare)
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Plant and system-level performance of combined heat and power plants equipped with different carbon capture technologies
- 2023
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Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 338
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Tidskriftsartikel (refereegranskat)abstract
- Installing carbon capture and storage (BECCS) capability at existing biomass-fired combined heat and power (bio-CHP) plants with substantial emissions of biogenic CO2 could achieve significant quantities of the negative CO2 emissions required to meet climate targets. However, it is unclear which CO2 capture technology is optimal for extensive BECCS deployment in bio-CHP plants operating in district heating (DH) systems. This is in part due to inconsistent views regarding the perceived value of high-exergy energy carriers at the plant level and the extended energy system to which it belongs. This work evaluates how a bio-CHP plant in a DH system performs when equipped with CO2 capture systems with inherently different exergy requirements per unit of CO2 captured from the flue gases. The analysis is based upon steady-state process models of the steam cycle of an existing biomass-fired CHP plant as well as two chemical absorption-based CO2 capture technologies that use hot potassium carbonate (HPC) and amine-based (monoethanolamine or MEA) solvents. The models were developed to quantify the plant energy and exergy performances, both at the plant and system levels. In addition, heat recovery from the CO2 capture and conditioning units was considered, as well as the possibility of integrating large-scale heat pumps into the plant or using domestic heat pumps within the local DH system. The results show that the HPC process has more recoverable excess heat (∼0.99 MJ/kgCO2,captured) than the MEA process (0.58 MJ/kgCO2,captured) at temperature levels suitable for district heating, which is consistent with values reported in previous similar comparative studies. However, using energy performance within the plant boundary as a figure of merit is biased in favor of the HPC process. Considering heat and power, the energy efficiency of the bio-CHP plant fitted with HPC and MEA are estimated to be 90% and 76%, respectively. Whereas considering exergy performance within the plant boundary, the analysis emphasizes the significant advantage the amine-based capture process has over the HPC process. Higher exergy efficiency for the CHP plant with the MEA capture process (∼35%) compared to the plant with the HPC process (∼26%) implies a relatively superior ability of the plant to adapt its product output, i.e., heat and power production, and negative-CO2 emissions. Furthermore, advanced amine solvents allow the BECCS plant to capture well beyond 90% of its total CO2 emissions with relatively low increased specific heat demand.
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| 4. |
- Roshan Kumar, Tharun, 1995, et al.
(författare)
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Process Analysis of Chemical Looping Gasification of Biomass for Fischer-Tropsch Crude Production with Net-Negative CO 2 Emissions: Part 1
- 2022
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 36:17, s. 9687-9705
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Tidskriftsartikel (refereegranskat)abstract
- Large-scale biofuel production plants require an efficient gasification process that generates syngas of high quality (with minimal gas contaminants and inert gases) to minimize the extent of the syngas cleaning processes required for liquid biofuel production. This work presents process modeling of the chemical looping gasification (CLG) process for syngas production. The CLG process is integrated with a Fischer-Tropsch synthesis (FTS) process to produce Fischer-Tropsch (FT) crude with net-negative CO2 emissions, enabling process and system-level analyses of this novel biomass-to-liquid process. CLG resembles indirect gasification in an interconnected circulating fluidized bed reactor, where instead of inert bed material, a solid-oxygen carrier, such as mineral ores rich in iron or manganese oxides, is used. The oxygen carrier particles undergo oxidation and reduction in the air reactor and fuel reactor, respectively, thereby providing heat and oxygen for gasification. This work uses data from CLG experiments performed with steel converter slag as the oxygen carrier and investigates its potential when integrated with different downstream gas cleaning trains and the subsequent fuel synthesis process with the primary objective of quantifying and evaluating the performance of the integrated CLG-FT process plant. Syngas with a high energy content of 12 MJ/Nm3 (lower heating value basis) is predicted with a cold gas efficiency of 73%. CO2/CO ratios, higher than indirect biomass gasification, are also predicted in the raw syngas produced; thus, there exists an opportunity to capture biogenic CO2 with a relatively lower energy penalty in the subsequent gas cleaning stages. This work quantifies other key performance indicators, such as heat recovery potential, negative CO2 emission capacity, and FT crude production efficiency of the CLG-FT plant. A 100 MWth CLG plant produces roughly 677-696 barrels per day of FT crude, with net-negative emissions of roughly 180 kilotonnes of CO2 annually.
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| 5. |
- Roshan Kumar, Tharun, 1995, et al.
(författare)
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Techno-Economic Assessment of Chemical Looping Gasification of Biomass for Fischer-Tropsch Crude Production with Net-Negative CO2 Emissions: Part 2
- 2022
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 36:17, s. 9706-9718
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Tidskriftsartikel (refereegranskat)abstract
- This work presents a techno-economic analysis of a used as the primary gasification process for biofuel production through Fischer-Tropsch synthesis (FTS). Two different gas cleaning process configurations, cold-gas cleanup and hot-gas cleanup process trains, are explored, along with off-gas utilization possibilities, to study their influence on the process economics of an integrated CLG-FT process plant. Off-gas recirculation to increase Fischer-Tropsch (FT) crude production has a significant influence on reducing the levelized production costs for FT crude. The results indicate that the specific production cost estimated for a CLG-FT plant with a hot-gas cleanup train is roughly 10% lower than the case with a cold-gas cleanup train, while the total plant costs remain relatively the same for all plant configurations. In addition to this, the former has a considerably higher overall system energy efficiency of 63%, roughly 18% more than the latter, considering the co-production of FT crude, district heating, and electricity. The specific investment costs range from 1.5 to 1.7 M euro 2018/MWLHV, and the specific FT crude production cost ranges from 120 to 147 euro 2018/MWhFT. Roughly 60% of total carbon fed to the process is captured, enabling net-negative CO2 emissions. A CO2 price for negative emissions would significantly reduce the specific fuel production costs and would, hence, be competitive with fossil-based liquid fuels.
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