| 1. |
- Guio Perez, Diana Carolina, 1985, et al.
(författare)
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Thermochemical Energy Storage with Integrated District Heat Production—A Case Study of Swede
- 2023
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Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 16:3
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Tidskriftsartikel (refereegranskat)abstract
- The implementation of electricity-charged thermochemical energy storage (TCES) using high-temperature solid cycles would benefit the energy system by enabling the absorption of variable renewable energy (VRE) and its conversion into dispatchable heat and power. Using a Swedish case study, this paper presents a process for TCES-integrated district heating (DH) production, assesses its technical suitability, and discusses some practical implications and additional implementation options. The mass and energy flows of a biomass plant retrofitted with an iron-based redox loop are calculated for nine specific scenarios that exemplify its operation under electricity generation mixes that differ with respect to variability and price. In addition, the use of two types of electrolyzers (low-temperature and high-temperature versions) is investigated. The results show that for the Swedish case, the proposed scheme is technically feasible and capable of covering the national DH demand by making use of the existing DH plants, with an estimated process energy efficiency (electricity to heat) of 90%. The results also show that for a retrofit of the entire Swedish DH fleet, the required inventories of iron are approximately 2.8 Mt for the intermediate scenario, which represents 0.3% and 11.0% of the national reserves and annual metallurgical production rates of the national industry, respectively. In addition to the dispatchable heat, the process generates a significant amount of nondispatchable heat, especially for the case that employs low-temperature electrolyzers. This added generation capacity allows the process to cover the heat demand while decreasing the maximum capacity of the charging side computed herein.
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| 2. |
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| 3. |
- Martinez Castilla, Guillermo, 1993, et al.
(författare)
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A novel experimental method for determining lateral mixing of solids in fluidized beds – Quantification of the splash-zone contribution
- 2020
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Ingår i: Powder Technology. - : Elsevier BV. - 1873-328X .- 0032-5910. ; 370, s. 96-103
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Tidskriftsartikel (refereegranskat)abstract
- An experimental method to investigate the lateral mixing of bulk solids in bubbling fluidized beds is presented.The method utilizes finite volume analysis of the measured temperature field over the bed surface, from which the solids dispersion coefficient is determined. The temperature field is measured with a thermographic camera,which in this work is applied to a fluid-dynamically down-scaled fluidized bed that resembles the conditions relevant for hot large-scale operation.The method is applied to investigate the effect of key parameters for the solids mixing process; fluidization velocity, particle size and pressure drop over the air distributor plate. The results showed up-scaled dispersion coefficients in the order of 10−3m2/s for the conditions investigated. The lateral mixing of solids decreased with increasing particle size and increased with increases in the fluidization velocity and pressure drop over the air distributor. The method was also used to quantify the contribution of the splash zone to the total lateral solids mixing. When lateral solids mixing in the splash zone was blocked with a vertical baffle the lateral solids dispersion was reduced by some 90%.
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| 4. |
- Martinez Castilla, Guillermo, 1993, et al.
(författare)
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Calcium looping for combined CO 2 capture and thermochemical energy storage
- 2023
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Ingår i: Circular Economy Processes for CO2 Capture and Utilization: Strategies and Case Studies. - 9780323956680 ; , s. 119-162
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The carbonation of calcium oxide (CaO) has been extensively investigated concerning the separation of CO2 from gaseous streams. The carbonation reaction is of special interest in postcombustion processes for the capture of CO2 since the produced calcium carbonate (CaCO3) can be calcined in a separate reactor to generate a stream of pure CO2 for sequestration and storage. The cycle, which consists of carbonation and calcination reactions, involves considerable heat of reaction, rendering the process relevant not only for CO2 capture but also for energy storage purposes in the form of thermochemical energy storage (TCES). Energy storage is envisioned as an important flexibility measure to increase the penetration of variable renewable electricity (VRE), thereby increasing the value of VRE due to the reduced share of generation that needs to be curtailed. In this chapter, the general characteristics of the calcium looping process for both CO2 capture and energy storage are presented. Thereafter, the process that combines these two features is described, focusing on its layout specifications, associated opportunities and challenges, and the most recent advances toward its development.
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| 5. |
- Martinez Castilla, Guillermo, 1993, et al.
(författare)
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Comparison of the Dynamic Behaviour between Bubbling and Circulating Fluidized Bed Combustors
- 2020
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Ingår i: INFUB - 12th European Conference on Industrial Furnaces and Boilers.
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Konferensbidrag (refereegranskat)abstract
- This work compares the dynamic behaviour of the flue gas side of large-scale bubbling and circulating fluidized bed (BFB and CFB respectively) boilers. For this, a dynamic model is developed and presented. The model is used to simulate two industrial units and is validated against steady-state operational data. The model is applied to investigate and compare the transient behaviour of BFB and CFB boilers of the same size given step changes in load and moisture content. Results show that for a certain load change the heat transfer to the waterwalls stabilizes faster in BFB units, yielding larger relative changes in temperature once a new steady state is established. Differences in stabilization time between the dense bed and the top of the furnace are observed in both units, caused by the distribution of solids along the combustor: the dense bed contains more solids than regions located higher up in the furnace and therefore it is found to be less sensitive to changes and slower to respond, with stabilization times of around 15 minutes in contrast to the 1-8 minutes observed for the upper furnace. This behaviour is accentuated in the BFB case where all the solids remain in the dense bottom region.
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| 6. |
- Martinez Castilla, Guillermo, 1993, et al.
(författare)
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Comparison of the Transient Behaviors of Bubbling and Circulating Fluidized Bed Combustors
- 2023
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Ingår i: Heat Transfer Engineering. - : Informa UK Limited. - 0145-7632 .- 1521-0537. ; 44:4, s. 303-316
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Tidskriftsartikel (refereegranskat)abstract
- This work compares the transient behaviors of the flue gas sides of large-scale bubbling and circulating fluidized bed (BFB and CFB, respectively) boilers. For this purpose, a dynamic model of the in-furnace side of fluidized bed combustors presented and validated by the authors in a former work is used to simulate two industrial units. The results show that for load changes the heat transfer to the waterwalls stabilizes more rapidly in BFB units. Differences in stabilization time between the dense bed and the top of the furnace are observed in both units, caused by the distribution of solids along the combustor: the dense bed contains more solids than regions located higher up in the furnace and, therefore slower to respond, with stabilization times of around 15 minutes, as compared to stabilization times in the range of 1-8 minutes for the upper furnace. This behavior is accentuated in the BFB, where all the solids remain in the dense bottom region. The effect of the characteristic times of the main in-furnace mechanisms (fluid-dynamics, fuel conversion, and heat transfer) on the dynamic performance of BFB and CFB units has been explored and expressed through proposed mathematical relationships.
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| 7. |
- Martinez Castilla, Guillermo, 1993, et al.
(författare)
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Dynamic modeling of the flue gas side of large-scale circulating fluidized bed boilers
- 2021
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Ingår i: CFB 2021 - Proceedings of the 13th International Conference on Fluidized Bed Technology. ; , s. 59-64
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Konferensbidrag (refereegranskat)abstract
- This paper presents a 1.5D dynamic model of the gas side of large-scale circulating fluidized bed boilers. The model accounts for the solid’s hydrodynamics, the fuel conversion and the heat transfer to the waterwalls. The model is validated with industrial data from a 100 MWth unit, showing a good agreement between simulation results and measured data. The validated model is used to study the dynamics of the furnace after a load change is introduced. Simulation results show that regions with large concentration of solids are slower to reach steady-state but are less sensitive to load changes.
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| 8. |
- Martinez Castilla, Guillermo, 1993, et al.
(författare)
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Dynamic Modeling of the Reactive Side in Large-Scale Fluidized Bed Boilers
- 2021
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 60:10, s. 3936-3956
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Tidskriftsartikel (refereegranskat)abstract
- This work presents a dynamic model of the reactive side of large-scale fluidized bed (FB) boilers that describes the in-furnace transient operation of both bubbling and circulating FB boilers (BFB and CFB, respectively). The model solves the dynamic mass and energy balances accounting for the bulk solids, several gas species, and the fuel phase. The model uses semi-empirical expressions to describe the fluid dynamics, fuel conversion, and heat transfer to the furnace walls, as derived from units other than the studied ones. The model is validated against operational data from two different industrial units: an 80 MW CFB and a 130 MW BFB, both at steady-state and transient conditions. The validated model is used to analyze: (i) the performance of the reactive side of two FB boilers under off-design, steady-state conditions of operation; and (ii) the open-loop transient response when varying load or fuel moisture. The results underline the key role of heat capacity on the stabilization time. Within a given unit, the differences in heat capacity between the top and bottom of the furnace affect also the stabilization times, with the furnace top (lower heat capacity) being 1–3 times faster in the CFB unit and up to 10 times faster in the BFB unit. Due to the differences in gas velocity, the investigated boilers are found to stabilize more rapidly to input changes when running at full load than at partial load. Lastly, a variable ramping rate analysis shows that the inherent transient responses of the reactive side disappear when disturbances are introduced at (slower) rates, typical of industrial operation. Thus, the reactive side could be modeled as pseudo-static.
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| 9. |
- Martinez Castilla, Guillermo, 1993, et al.
(författare)
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Dynamics and control of large-scale fluidized bed plants for renewable heat and power generation
- 2023
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 219:B
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Tidskriftsartikel (refereegranskat)abstract
- As the share of variable renewable electricity increases, thermal power plants will have to adapt their operational protocols in order to remain economically competitive while also providing grid-balancing services required to deal with the inherent fluctuations of variable renewable electricity. This work presents a dynamic model of fluidized bed combustion plants for combined heat and power production. The novelty of the work lays in that (i) it provides an analysis of the transient performance of biomass-based fluidized bed combustion plants for combined heat and power production, (ii) the dynamic model includes a description of both the gas and water- steam sides and (iii) the model is validated against operational data acquired from a commercial-scale plant. The validated model is here applied to analyze the inherent dynamics of the investigated plant and to evaluate the performance of the plant when operated under different control and operational strategies, using a relative gain analysis and a variable ramping rate test. The results of the simulations reveal that the inherent dynamics of the process have stabilization times in the range of 5–25 min for all the step changes investigated, with variables connected to district heating production being the slowest. In contrast, variables connected to the live steam are the fastest, with stabilization times of magnitude similar to those of the in-furnace variables (i.e., around 10 min). Thus, it is concluded that the proper description of the dynamics in fluidized bed combustion plants for combined heat and power production requires modeling of both the gas and water sides (which is rare in previous literature). Regarding the assessment of control strategies, the boiler-following and hybrid control (combined fixed live steam and sliding pressure) strategies are found to be able to provide load changes as fast as 5%-unit/s, albeit while causing operational issues such as large pressure overshoots. The relative gain analysis outcomes show that these control structures do not have a steady-state gain on the power produced, and therefore it is the dynamic effect of the steam throttling that triggers the rapid power response. This study also includes the assessment of a turbine bypass strategy, the results of which show that it enables fast load-changing capabilities at constant combustion load, as well as decoupling power and heat production at the expense of thermodynamic losses.
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| 10. |
- Martinez Castilla, Guillermo, 1993, et al.
(författare)
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Dynamics of large-scale bubbling fluidized bed combustion plants for heat and power production
- 2022
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Ingår i: 24th Fludiized Bed Conversion proceeding.
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Konferensbidrag (refereegranskat)abstract
- This paper presents a dynamic model of bubbling fluidized bed (BFB) units for combined heat and power (CHP) production that results from connecting a model of the gas side with a process model of the water-steam side. The model output is validated by comparison with operational data measured in a 130-MWth BFB plant that produces electricity, district heating (DH) water and steam to industrial clients. The validation shows that the model can satisfactorily describe both multi-load steady-state operation as well as load transients. The validated model is here used to compute the inherent process dynamics of the reference plant. The simulation results highlight the fact that the water-steam cycle reaches stabilization faster after changes in the DH line and steam delivered to clients than to changes in the combustor load. The timescales of the plant outputs for different changes have been computed, with stabilization times ranging between 2 and 15 min for the power production versus 2-25 min characterizing the DH production. When comparing these results with the characteristic times of the gas side, it is concluded that the water-steam side is an order of magnitude slower, i.e., limiting the transient operation capabilities of BFB-CHP plants. This in in contrast to earlier findings for circulating fluidized bed plants, where the characteristic times of both sides are in the same order of magnitude.
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