Optimisation rationnelle des performances énergétiques et environnementales d’une centrale à charbon pulvérisé fonctionnant en oxy-combustion

The objective of the thesis is the conception of an optimized oxy-fired pulverized-coal power plant. Such a power plant is constituted of an oxygen production system (ASU), a boiler, power cycle, depollution equipments and a CO2 purification and compression system (CPU). After a first step consists in understanding, analyzing and modeling the different processes composing the oxy-combustion system; the work will focus on the optimization of the performances and the configuration of the power plant by minimizing exergy destructions while ensuring economic competitiveness of the obtained solution. At the end of the thesis, the origins of the exergetic losses in the system as well as the thermal integration scheme allowing the maximization of the energetic gains at power plant level will be identified. Additionally, the most adapted flue gas depollution strategies will be defined and the new integrated process schemes will be evaluated on both a techno-economic and flexibility basis.L’objectif de la thèse est de concevoir un design le plus optimisé possible d’une centrale à charbon pulvérisée fonctionnant en oxy-combustion. Une telle centrale intègre un système de production d’oxygène (ASU), une chaudière, un cycle électrogène, des équipements de dépollution ainsi qu’un système de purification et de compression du CO2 (CPU). Ainsi, dans un premier temps, la thèse portera sur la compréhension, l’analyse et la modélisation des différents procédés qui composent la chaîne d’une centrale fonctionnant en oxy-combustion. Ensuite, les performances et la configuration de la centrale seront optimisées de façon à réduire la destruction d’exergie tout s’assurant de la compétitivité économique de la solution ainsi obtenue. A l’issue de cette thèse, les origines des pertes exergétiques du système étudié et les schémas d’intégration permettant de maximiser les gains énergétique à l’échelle de la centrale seront identifiées. De plus, les stratégies de dépollution des fumées les plus adaptées seront définies et les nouveaux procédés intégrés seront évalués à la fois d’un point de vue technico-économiques et flexibilité

Assessment of the Flue Gas Recycle Strategies on Oxy-Coal Power Plants using an Exergy-based Methodology

A presentation of this paper was given at the 16th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction, Rodes(Greece) 29 September- 2 October 2013This article is available online at http://www.aidic.it/cet/13/35/057.pdfInternational audienceWhile oxy-combustion CO2 capture was foreseen to have higher improvement potential than post-combustion a decade ago, research has not been carried out at the same pace since then and today, the latter exhibits higher technological maturity along with low energy penalty thanks to advanced process integration and solvents formulation. Thus, significant efficiency improvement is needed for the oxy-combustion route to be competitive with post-combustion for carbon capture on coal-fired power plants. In order to achieve such improvements, process integration at system level is required to assess the true energy savings potential of oxy-combustion. In this study, an exergy-based methodology is performed to compare various flue gas recirculation strategies on a state-of-the-art 1100 MWe gross oxy-fired power plant. Exergy analysis at unit operation level allows the identification of the location and the magnitude of the thermodynamic irreversibilities occurring in the process, leading to an enhanced understanding of the studied system. In addition to the reference case in which the secondary recycle is fully depolluted and dehydrated; three alternative flue gas recirculation options have been investigated. Among the studied strategies, recirculation of the secondary flow prior the regenerative heat exchanger with a high temperature particle removal device leads to the highest net plant efficiency. This option not only allows the minimal exergy losses in the boiler but also minimizes the flowrate going through the downstream depollution devices. The net plant efficiency obtained for this architecture is 38.0%LHV, which represents a 3% increase compared to the reference oxy-combustion plant. Comparing this figure to an air-fired power plant modeled with the same set of hypotheses, the energy penalty is 8.1%-pts

Towards Second Generation Oxy-pulverized Coal Power Plants: Energy Penalty Reduction Potential of Pressurized Oxy-combustion Systems

AbstractDuring the last decade, CO2 capture on coal power plants has been the subject of sustained attention as one of the most credible way to drastically reduce anthropogenic greenhouse gas emissions. Significant reduction in the energy penalty related to the oxy- combustion routes has been achieved but uncertainties remain in the operation of such a process inducing major modifications of the power island. In this context, for oxy-combustion, and more generally carbon capture to become a reality, its energy penalty shall be drastically reduced. In that perspective, cutting edge strategies allowing taking full advantage of oxy-fired operation have to be investigated. Among them, boiler pressurization has been identified as one of the most promising solution. Two major pressurized oxy-combustion concepts have emerged in literature: the flameless combustion technology (ISOTHERM®) and the staged-pressurized oxy-combustion (SPOC) concept. According to the authors describing those two processes, whilst very different in the combustion temperature control strategy, they both succeed in allowing pressurized operation.In this work, those two concepts have been compared to an air-fired, a conservative and optimized atmospheric oxy-fired power plants in terms of energy performances. The reason underlying below the observed differences, have been determined using exergy analysis. The SPOC process leads to significantly lower energy penalty, as low as 3.8%-pts compared to the ISOTHERM® concepts which lead to performance in the same order of magnitude than the optimized atmospheric design. It has been highlighted that this difference is essentially due to the large flue gas recycling requirement for the latter concept to control combustion temperature

Rational optimization of the energetic and environmental performances of an oxy-fired pulverized-coal power plant

L’objectif de la thèse est de concevoir un design le plus optimisé possible d’une centrale à charbon pulvérisée fonctionnant en oxy-combustion. Une telle centrale intègre un système de production d’oxygène (ASU), une chaudière, un cycle électrogène, des équipements de dépollution ainsi qu’un système de purification et de compression du CO2 (CPU). Ainsi, dans un premier temps, la thèse portera sur la compréhension, l’analyse et la modélisation des différents procédés qui composent la chaîne d’une centrale fonctionnant en oxy-combustion. Ensuite, les performances et la configuration de la centrale seront optimisées de façon à réduire la destruction d’exergie tout s’assurant de la compétitivité économique de la solution ainsi obtenue. A l’issue de cette thèse, les origines des pertes exergétiques du système étudié et les schémas d’intégration permettant de maximiser les gains énergétique à l’échelle de la centrale seront identifiées. De plus, les stratégies de dépollution des fumées les plus adaptées seront définies et les nouveaux procédés intégrés seront évalués à la fois d’un point de vue technico-économiques et flexibilité.The objective of the thesis is the conception of an optimized oxy-fired pulverized-coal power plant. Such a power plant is constituted of an oxygen production system (ASU), a boiler, power cycle, depollution equipments and a CO2 purification and compression system (CPU). After a first step consists in understanding, analyzing and modeling the different processes composing the oxy-combustion system; the work will focus on the optimization of the performances and the configuration of the power plant by minimizing exergy destructions while ensuring economic competitiveness of the obtained solution. At the end of the thesis, the origins of the exergetic losses in the system as well as the thermal integration scheme allowing the maximization of the energetic gains at power plant level will be identified. Additionally, the most adapted flue gas depollution strategies will be defined and the new integrated process schemes will be evaluated on both a techno-economic and flexibility basis

Efficiency evaluation procedure of coal-fired power plants with CO2 capture, cogeneration and hybridization

International audienceIn an energy landscape undergoing great change with regard to CO 2 emissions, the evaluation of solutions allowing a drastic reduction of the anthropogenic emissions are carried out for more than a decade. Among them, CO 2 capture and storage on coal power plants has been identified as a particularly promising solution but other options such as heat and electricity cogeneration and power plant hy-bridization with solar of biomass can also reduce the carbon footprint of electricity production. However, the implementation of an external process on a power plant impacts its electric production. Post-and oxy-combustion CO 2 capture, cogeneration for industries or districts, or hybridization are all examples of processes either demanding thermal and electrical energy or providing heat valorization opportunities. To identify the true potential of those systems, the evaluation of the performance of the integrated system is necessary. Also, to compare different solutions, a common framework has to be adopted since the performance of those systems are often highly dependent of the considered hypotheses. This paper presents a full integration procedure suited for both new built and retrofit coal-fired power plants by means of easy-to-use correlations, which links heat demand to production loss and waste heat availability to production increase, taking their exergy content into account. This correlative approach provides an analytical tool allowing a quick and realistic evaluation of a given concept or process layout, without the need of a detailed full power plant model. Examples are given for CO 2 capture, cogeneration and hybridization, illustrating the interest of the approach to evaluate and compare several technologies on a consistent manner. An Excel spreadsheet with the calculation procedure is available online (see supporting information)

Performance Simulation of Full-scale Wet Flue Gas Desulfurization for Oxy-coal Combustion

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Optimal Integration of the Flue Gas Heat for the Minimization of the Energy Penalty of Oxy-fired Power Plants

International audienceOxy-fired coal power plants require the recycling of flue gas to dilute the oxygen in order to moderate the combustion in the boiler. This induces a significant structural modification of the boiler and flue gas train compared to air-fired power plants, offering the opportunity for new thermal integrations opportunities.In this study, a methodology allowing the assessment of the net plant efficiency increase brought by finely integrating heat sources into the steam cycle with minimal simulation runs is used for the comparison of several flue gas heat valorization layouts. Three configurations described in literature have been compared to an alternative option aiming for the minimization of exergy losses. For each of those configurations, the net plant efficiency after integration has been assessed and compared to an air-fired power plant in order to determine the energy penalty induced by carbon capture. Results show that the proposed alternative leads to promising energy performances: a net plant efficiency increase of 0.5%LHV can still be obtained compared to the already integrated base-case, reducing the energy penalty from 7.1%-pts down to 6.5%-pts

Techno-economic Optimization of First Generation Oxy-fired Pulverized-coal Power Plant

International audienceIn this paper, a holistic approach taking into account process economics is employed in order to assess the true potential of first generation oxy-fired power plants. The proposed methodology is carried out in two-steps. The first step consists in the minimization of the energy penalty: an exergy analysis is performed on a conventional base-case oxy-fired power plant in order to identify the possible improvement paths, including structural modifications and thermal integrations. At the end of this step, the process layout leading to a minimized energy penalty is obtained. However, as the introduction of a process modification impacts the plant's CAPEX, each modification highlighted in the previous step is characterized by a techno-economic criterion in order to determine its profitability in a second step. The marginal cost of electricity production, defined as the ratio between additional CAPEX and the net production increase is used for the process modification assessment.This procedure has been applied on state-of-the-art processes in order to estimate the potential of first generation oxy-combustion power plant. The optimization solely based on an energetic criterion leads to a plant layout with an energy penalty of 6.0%-pts, which represents a 38% reduction (the energy penalty of the base case plant is 9.4%-pts). However, the consideration of economic aspects has highlighted that some of the considered process modifications were not justified on an economic stand point. The optimal oxy-fired power plant, from a techno-economic point of view, exhibits an energy penalty of 6.9%-pts and allows a 20% reduction of the CO2 avoidance cost compared to the base-case oxy-fired plant

Performance assessment of first generation oxy-coal power plants through an exergy-based process integration methodology

International audienceIn this study, an exergy-based system level methodology is conducted to assess the energy penalty reduction potential of different configurations of first generation oxy-fired pulverized coal power plants. Once the process improvement potential is identified by exergy analysis on an oxy-fired plant with minimal integration, a heat integration methodology minimizing the exergy losses is carried out. Exergy analysis is employed as a guideline weighted by technological and operational constraints.This methodology has been applied to study the conventional cold flue gas recycle scheme and three alternative flue gas recirculation options including the widely studied warm recycle scheme. The integration potential of advanced cryogenic ASUs (air separation units) has also been assessed. Finally, the energy penalty associated to the capture when a high-purity CO2 flow is required has been determined.Among the different cases considered in this study, recirculation of the flue gas before the regenerative heater with an advanced ASU and a double-column CPU (compression and purification unit) leads to the highest NPE (net plant efficiency). For this case, the NPE is 39.1 % based on the lower heating value (7 %-pts energy penalty), which corresponds to a 6.5% improvement compared to the base-case plant. When high-purity CO2 is desired, the energy penalty is increased by 0.2 %-pts for the same configuration

Remodelling of heat exchanger networks integrating the temperature dependence of the calorific flows of the streams: Application to the hydrodesulphurization unit of a refinery

The fight against global warming and the reduction of greenhouse gas emissions is now a major challenge for society and industry. In this context of decarbonization, combined with a rise in energy prices, the latter are seeking to equip themselves with energy diagnosis and decision support tools to redesign existing processes and thus contribute to greater efficiency. energy of their production site. Generally based on the principles of pinch analysis (Linnhoff and Sahdev, 2000), different approaches and resolution techniques are proposed in the literature to address this issue. Review articles such as (Klemeš et al., 2018), (Čuček et al., 2019) summarize them and highlight the advantages and limitations of each of them. The RREflex software, developed at the LGC for several years and tested on other processes including a crude oil preheating train (Payet et al., 2018), is one of the tools for carrying out the initial synthesis as well as the remodelling of networks of heat exchangers with the aim of improving the energy performance of existing processes