| 1. |
- Allgurén, Thomas, 1986, et al.
(författare)
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Alkali sulfation during combustion of coal in a pilot scale facility using additives to alter the global sulfur to potassium and chlorine to potassium ratios
- 2021
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 38:3, s. 4171-4178
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Tidskriftsartikel (refereegranskat)abstract
- Due to the urgent needs to reduce anthropogenic carbon dioxide emissions there is an increasing interest in the use of alternative fuels. For this reason, there is a need for new knowledge on how to design and adapt existing heat and power plants to biogenic and waste-derived fuels. This work relates to co-firing of biomass and coal and the sulfation of alkali chlorides in coal-fired flames doped with chemical additives. We aim to examine the global time scales of alkali sulfation and chlorination based on combustion experiments that were conducted in a 30-kW coal flame. Temperature, gas and particle composition measurements were conducted. Both experiments and modelling support that the apparent alkali sulfation kinetics are fast in a coal-fired flame and that it is dominated entirely by the presence of SO 2. The availability of oxygen and carbon monoxide, or hydrocarbons, is also critical to sustain the sulfation reaction cycle; low concentrations are sufficient. For industrial boilers this implies that sulfur addition, in combination with reburning, should constitute an efficient strategy to mitigate alkali-chlorination and the related high temperature corrosion.
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| 2. |
- Allgurén, Thomas, 1986, et al.
(författare)
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Chemical Interactions between Potassium, Sulfur, Chlorine, and Carbon Monoxide in Air and Oxy-fuel Atmospheres
- 2020
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 34:1, s. 900-906
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents experimental and modeling work on the interaction between the K, Cl, and S components, and these chemical interactions are studied in both air-fuel and oxy-fuel atmospheres. Detailed kinetic modeling is conducted to examine the potassium chloride sulfation and its interaction with CO oxidation in both nitrogen- and carbon-dioxide-based atmospheres. The oxidation of CO enhances the kinetics of alkali sulfation for typical post-flame conditions, below 1000 °C, in both atmospheres. For higher temperatures, sulfation kinetics are promoted even further in CO2-rich atmospheres. Oxy-fuel atmospheres, i.e., CO2-rich atmospheres, also promote increased levels of CO in technical-scale flames. Therefore, in practical systems, enhanced sulfation kinetics will automatically be promoted by flue gas recirculation. Also, the availability of sulfur, in the form of an increased SO2 concentration, often enables complete sulfation of alkali in oxy-fuel atmospheres as a result of the flue gas recirculation. The availability of SO3 may increase in oxy-fuel compared to air-fuel atmospheres as a result of either elevated SO2 levels or different sulfation reaction patterns, as discussed in the modeling of this work. However, SO3 has no significant impact on the overall sulfation rates in oxy- compared to air-fired systems.
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| 3. |
- Allgurén, Thomas, 1986, et al.
(författare)
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NO formation during co-combustion of coal with two thermally treated biomasses
- 2022
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 235
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Tidskriftsartikel (refereegranskat)abstract
- The combustion behavior of biomass as a fuel varies dependent on source of the raw material, but also on the type of pre-treatment. In this work steam exploded and torrefied woody biomass were studied with respect to NOx formation in co-firing experiments. Most of the reported data is based on small scale experiments and simulations. In this work, however, have three different cases been investigated experimentally in a 1.5MW(th) combustor supported by reaction simulations. One case corresponds to firing 100% Utah bituminous coal and two cases where 15% of the coal (on a mass basis) has been replaced with either torrefied or steam exploded biomass. Two of the cases was also studied in a utility scale 1.3 GW(th) industrial boiler. In both units did the case with pure coal result in the highest amount of NO formed, which was expected due to the higher amount of fuel-bound nitrogen in the coal, as compared to the biomass fuels. The fuel analyses indicate that the nitrogen content is the same in the two investigated biofuels. However, the amount of NO formed differed. Gas composition measurements reveal that the partitioning of volatile nitrogen species (HCN and NH3) varies between the biomass co-firing cases. This was investigated further using detailed reaction simulations and is suggested as the main reason for the observed difference in NO formation.
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| 4. |
- Blackburn, Landen D., et al.
(författare)
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Development of novel dynamic machine learning-based optimization of a coal-fired power plant
- 2022
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Ingår i: Computers and Chemical Engineering. - : Elsevier BV. - 0098-1354. ; 163
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Tidskriftsartikel (refereegranskat)abstract
- The increasing fraction of intermittent renewable energy in the electrical grid is resulting in coal-fired boilers now routinely ramp up and down. The current state-of-the-art operation for such boilers is to apply steady-state, neural network-based optimization to make control decisions in real-time, and this work demonstrates the feasibility of extending this to dynamic, neural network-based optimization using a long short-term memory neural network. A simplified numerical simulation of a t-fired coal boiler and supporting equipment is used to represent a real plant subjected to both steady-state, neural network-based optimization and dynamic, neural network-based optimization. Using the same intervals and a particle swarm optimization algorithm, the dynamic optimization outperforms the steady-state optimization and realizes up to 4.58% improvement in thermal efficiency. Dynamic optimization with a long short-term memory neural network is shown to both be feasible and beneficial for operation of a coal-fired boiler under changing load.
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| 5. |
- Blackburn, Landen D., et al.
(författare)
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Dynamic machine learning-based optimization algorithm to improve boiler efficiency
- 2022
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Ingår i: Journal of Process Control. - : Elsevier BV. - 0959-1524. ; 120, s. 129-149
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Forskningsöversikt (refereegranskat)abstract
- With decreasing computational costs, improvement in algorithms, and the aggregation of large industrial and commercial datasets, machine learning is becoming a ubiquitous tool for process and business innovations. Machine learning is still lacking applications in the field of dynamic optimization for real-time control. This work presents a novel framework for performing constrained dynamic optimization using a recurrent neural network model combined with a metaheuristic optimizer. The framework is designed to augment an existing control system and is purely data-driven, like most industrial Model Predictive Control applications. Several recurrent neural network models are compared as well as several metaheuristic optimizers. Hyperparameters and optimizer parameters are tuned with parameter sweeps, and the resulting values are reported. The best parameters for each optimizer and model combination are demonstrated in closed-loop control of a dynamic simulation, and several recommendations are made for generalizing this framework to other systems. Up to 0.953% improvement is realized over the non-optimized case for a simulated coal-fired boiler. While this is not a large improvement in percentage, the total economic impact is $991,000 per year, and this study builds a foundation for future machine learning with dynamic optimization.
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| 6. |
- Draper, Teri, et al.
(författare)
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A comparison of industrial-scale (471 MWe) radiometer heat flux measurements between pulverized-coal and 85% coal/15% biomass co-firing combustion
- 2021
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work evaluates and compares radiative heat transfer measurements conducted at the 471 MWe Hunter Powerplant Unit 3 utility boiler in Utah, USA, during commercial operation with coal and during tests with co-firing of coal and biomass. The coal used was a Utah sourced bituminous coal, which was mixed with 15 wt% of torrefied wood in the co-firing test. The measurements were gathered using two different narrow angle radiometers and one ellipsoidal radiometer to measure the radiative heat flux. Data were gathered at several floors through port openings in the boiler wall and the samplings were spread out over several hours. Additionally, the gas temperature was measured at positions close to the inner walls of the different floors. Overall, the measured heat fluxes decreased with increasing boiler floor level, and while the measurement data spread is rather high for each measurement, the data spreads for both fuel conditions significantly overlap each other, indicating that it is likely the heat flux profile remains unchanged when running either type of fuel.
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| 7. |
- Dziejarski, Bartosz, 1995, et al.
(författare)
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CO 2 capture materials: a review of current trends and future challenges
- 2023
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Ingår i: Materials Today Sustainability. - 2589-2347. ; 24
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Forskningsöversikt (refereegranskat)abstract
- Over the last decade, CO2 adsorption technology has quickly gained popularity and is now widely applied in global CCUS projects due to playing an important role in achieving net-zero emissions by 2050. As a result, novel materials, or post-modification methods of those already available have been successively reported to enhance the efficiency of CO2 capture from flue gases. This paper discusses a systematic understanding of fundamental aspects of current research trends in terms of developing selected solid CO2 adsorbent, with a particular emphasis on the upcoming challenges. The candidates are reviewed considering the practical drawbacks of imposed by industrial scale and economics, including carbon-based materials, metal-organic frameworks (MOFs), polymers, zeolites, silica, alumina, metal oxides, amine-based adsorbents, and other composite porous materials. Sustainable sorbents derived from biomass and industrial residues are also studied due to the high need for cost-effective raw materials and their crucial role in the circular economy. Lastly, a techno-economic analysis (TEA) is included to provide the most important criteria that should be considered when adsorbents are implemented on an industrial scale. Consequently, the review is summarized, and recommendations are offered for future research in the advancement of CO2 capture materials. The paper aims to establish a comprehensive theoretical basis of adsorption technologies currently progressed to reduce CO2 emissions, along with highlighting the identification and precise articulation of the most important future research paths that could be beneficial to address over the next years.
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| 8. |
- Dziejarski, Bartosz, 1995, et al.
(författare)
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Current status of carbon capture, utilization, and storage technologies in the global economy: A survey of technical assessment
- 2023
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 342
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Forskningsöversikt (refereegranskat)abstract
- The latest tremendously rapid expansion of the energy and industrial sector has led to a sharp increase in stationary sources of CO2. Consequently, a lot of concerns have been raised about the prevention of global warming and the achievement of climate mitigation strategies by 2050 with a low-carbon and sustainable future. In view of this, the current state of various aspects of carbon capture, utilization, and storage (CCUS) technologies in general technical assessment were concisely reviewed and discussed. We concentrated on precisely identifying the technology readiness level (TRL), which is beneficial to specifically defining the maturity for each key element of the CCUS system with a commercialization direction paths. In addition, we especially presented and emphasized the importance of CO2 capture types from flue gases and CO2 separation methods. Then, we determined valuable data from the largest R&D projects at various scales. This paper provides a critical review of the literature related to challenges of the CCUS system that must be overcome to raise many low TRL technologies and facilitate their implementation on a commercial scale. Finally, our work aims to guide the further scaling up and establishment of worldwide CO2 emission reduction projects.
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| 9. |
- Dziejarski, Bartosz, 1995, et al.
(författare)
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Upgrading recovered carbon black (rCB) from industrial-scale end-of-life tires (ELTs) pyrolysis to activated carbons: Material characterization and CO 2 capture abilities
- 2024
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Ingår i: Environmental Research. - 0013-9351 .- 1096-0953. ; 247
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Tidskriftsartikel (refereegranskat)abstract
- The current study presents for the first time how recovered carbon black (rCB) obtained directly from the industrial-scale end-of-life tires (ELTs) pyrolysis sector is applied as a precursor for activated carbons (ACs) with application in CO2 capture. The rCB shows better physical characteristics, including density and carbon structure, as well as chemical properties, such as a consistent composition and low impurity concentration, in comparison to the pyrolytic char. Potassium hydroxide and air in combination with heat treatment (500–900 °C) were applied as agents for the conventional chemical and physical activation of the material. The ACs were tested for their potential to capture CO2. Ultimate and proximate analysis, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), Raman spectroscopy, thermogravimetric analysis (TGA), and N2/CO2 gas adsorption/desorption isotherms were used as material characterization methods. Analysis revealed that KOH-activated carbon at 900 °C (AC-900K) exhibited the highest surface area and a pore volume that increased 6 and 3 times compared to pristine rCB. Moreover, the AC-900K possessed a well-developed dual porosity, corresponding to the 22% and 78% of micropore and mesopore volume, respectively. At 0 °C and 25 °C, AC-900K also showed a CO2 adsorption capacity equal to 30.90 cm3/g and 20.53 cm3/g at 1 bar, along with stable cyclic regeneration after 10 cycles. The high dependence of CO2 uptake on the micropore volume at width below 0.7–0.8 nm was identified. The selectivity towards CO2 in relation to N2 reached high values of 350.91 (CO2/N2 binary mixture) and 59.70 (15% CO2/85% N2).
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| 10. |
- Edland, Rikard, 1990, et al.
(författare)
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Evaluation of NOx-Reduction Measures for Iron-Ore Rotary Kilns
- 2020
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 34:4, s. 4934-4948
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Tidskriftsartikel (refereegranskat)abstract
- The grate-kiln process is employed for sintering and oxidation of iron-ore pellets. In this process, a fuel (typically coal) is combusted with a large amount of excess air in a rotary kiln, and the high air-to-fuel ratio leads to significant NOx formation. The current Article is an assessment of NOx reduction measures that have been tested in pilot-scale and in full-scale by the Swedish iron-ore company Luossavaara-Kiirunavaara Aktiebolag (LKAB). The results show that the scaling between the full-scale kiln and the pilot-scale kiln is crucial, and several primary measures that reduce NOx significantly in pilot-scale achieve negligible reduction in full-scale. In the investigated full-scale kiln, thermal NOx formation is efficiently suppressed and low compared with the NO formation from the fuel-bound nitrogen (especially char-bound nitrogen). Suppressing the NO formation from the char-bound nitrogen is difficult due to the high amounts of excess air, and all measures tested to alter mixing patterns have shown limited effect. Switching to a fuel with a lower nitrogen content is efficient and probably necessary to achieve low NOx emissions without secondary measures. Simulations show that replacing the reference coal with a biomass that contains 0.1% nitrogen can reduce NOx emissions by 90%.
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