Use of steam jet booster as an integration strategy to operate a natural gas combined cycle with post-combustion CO2 capture at part-load

Apan-Ortiz, Jorge Igor; Sánchez-Fernández, Eva; González-Díaz, Abigail

doi:10.1016/j.energy.2018.09.148

Cited by 7 publications

(5 citation statements)

References 16 publications

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“…Due to rising GT outlet temperatures at part load (lower isentropic efficiency) the HP and IP flow temperature is controlled via attemperation to the maximum design levels of the steam turbines (601°C). Steam turbine isentropic efficiencies are assumed to be constant at part load (Sanchez Fernandez et al 2016, Apan-Ortiz et al 2018.…”

Section: Part Load Strategymentioning

confidence: 99%

Operating flexibility of natural gas combined cycle power plant integrated with post-combustion capture

Spitz

González-Díaz

Chalmers

et al. 2019

International Journal of Greenhouse Gas Control

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Highly flexible, low-carbon electricity generation with gas-fired power stations with CO 2 capture addresses the challenges of balancing variable renewable electricity supply in low carbon electricity systems. This detailed technical assessment of flexible CO 2 capture plant operation at natural gas combined cycle power stations with post-combustion CO 2 capture examines the operating strategies of capture plant bypass and interim solvent storage. We show that solvent storage allows expanding the operating envelope of gas fired CCS power stations by +/-10%. Further we demonstrate that electricity and CO 2 output can be decoupled for up to 3 hours with approx. 6000 m 3 of additional solvent inventory for the purpose of reducing the CO 2 flow variability in downstream transportation and storage systems, mitigating potentially deleterious injection well effects. 1hr of solvent storage operation at full load can be regenerated in as fast as 2.1hrs during continuous operation of the CCS power plant by choosing a controlled steam extraction strategy from the combined cycle and thus throttling the low pressure turbine. The electricity output penalty associated with the delayed regeneration of solvent ranges from 420-450kWh/tCO 2 with this strategy, which compares to 380kWh/tCO 2 for immediate regeneration at full load design conditions. By deploying a novel variable speed drive integrally geared compressor model, we find that, unlike previously thought, an uncontrolled steam extraction strategy, referred as a floating steam extraction strategy, can lead to choking of the CO 2 compressor during additional solvent regeneration. A pre-compression stage would be necessary under this extraction strategy to restore feasible operation of the main CO 2 compressor, and makes this strategy more complex to implement. When decreasing the desorber pressure at part-load care must, therefore, be taken to respect the operating limits of the compressor. To assist with the use of rigorous plant performance data in wider electricity system models, correlations for key performance parameters of NGCC-CCS power plants at varying load, with capture bypass and additional solvent regeneration are provided.

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Section: Part Load Strategymentioning

confidence: 99%

Operating flexibility of natural gas combined cycle power plant integrated with post-combustion capture

Spitz

González-Díaz

Chalmers

et al. 2019

International Journal of Greenhouse Gas Control

Self Cite

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“…The air/fuel mass flow rate ratio of the GT plays an important role in controlling the turbine exhaust temperature (TET). 28 As shown in Figure 9(b), the ratio is relatively constant for 100−80% load and the turbine inlet temperature (TIT) remains practically unchanged. As the load decreases below 80%, the ratio increases to avoid an excessive increase in the exhaust temperature.…”

Section: Resultsmentioning

confidence: 85%

“…GT efficiency decreases with decreasing load, and this results in an increase in the flue gas temperature as shown in Figure (a). The air/fuel mass flow rate ratio of the GT plays an important role in controlling the turbine exhaust temperature (TET) . As shown in Figure (b), the ratio is relatively constant for 100–80% load and the turbine inlet temperature (TIT) remains practically unchanged.…”

Section: Resultsmentioning

confidence: 98%

Evaluation of Novel Configurations of Natural Gas Combined Cycle (NGCC) Power Plants for Load-Following Operation using Dynamic Modeling and Optimization

2019

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With increasing penetration of intermittent renewable energy sources into the electric grid, conventional thermal power plants are being forced to cycle their load and operate under low-load conditions much more frequently. A high-fidelity dynamic model of a natural gas combined cycle (NGCC) power plant with rigorous equipment level submodels is developed in this work. A model of the gas turbine (GT) for estimating its performance under off-design conditions, a thermo-hydraulic model for the heat recovery steam generator (HRSG), and a model of the steam turbine (ST) with moisture detection and model adaptation capability are also developed. Five novel configurations are proposed for controlling the main steam and reheat steam temperatures while avoiding “spraying to saturation” during fast load-following by considering different final high-pressure superheater (HP SH2)/reheater (RH) arrangements (in series or in parallel) and attemperation strategies (single-stage, two-stage, and damper-assisted attemperation). Load-following operation is studied under two operational strategies, i.e., the industry-standard coordinated control strategy and dynamic optimization. Dynamic optimization is used to maximize the plant efficiency while satisfying the operational constraints and state transition constraints. It was observed that while more than one configuration can avoid spraying to saturation and maintain the steam temperatures within their limits even during very fast load transients, their efficiency can greatly vary and that dynamic optimization, when feasible, can lead to superior efficiency than the coordinated control system. The parallel HP SH2/RH configuration using the damper-assisted attemperation strategy shows the highest efficiency.

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“…Under the sliding-pressure operation, the drum pressure slides as the load decreases. The sliding-pressure operation leads to higher efficiency . However, under the sliding-pressure operation, the HP drum experiences large variations in the steam pressure and temperature, affecting the transient response of mechanical and thermal stresses depending on the detailed drum design.…”

Section: Ngcc Plant Dynamic Modelmentioning

confidence: 99%

“…The load-following operation of NGCC plants can be done under fixed-pressure mode or sliding-pressure mode. 37 Under the fixed-pressure mode, the drum pressure and therefore the temperature of the saturated steam from the drum remain fairly constant. Under the sliding-pressure operation, the drum pressure slides as the load decreases.…”

Section: Ngcc Plant Dynamic Modelmentioning

confidence: 99%

Multiobjective Dynamic Optimization for Optimal Load-Following of Natural Gas Combined Cycle Power Plants under Stress Constraints

Wang

Bhattacharyya

Turton

2021

Ind. Eng. Chem. Res.

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With the increasing penetration of intermittent renewable energy sources into the electric grid, there is an associated need for conventional thermal power plants that are designed to operate at base-load conditions to cycle their load rapidly and frequently and operate under low-load conditions. Fast load-following operations lead to plant efficiency loss and the reduction of equipment life. A high-fidelity dynamic model of a natural gas combined cycle power plant, with rigorous equipment level submodels, is developed to capture the plant transient performance and the thermomechanical stress evolution at the high-pressure drum is computed to assess the drum life consumption. Stress evolution is modeled for the location of the edge at the drum/downcomer junction that experiences high circumferential stress amplitude during the fast load-following operation, leading to higher fatigue damage than locations considered under existing design standards. A dynamic optimization problem is solved for optimal load-following operation. Depending on the value of the stress constraint and the desired ramp rate, satisfying the desired stress constraint may be infeasible without relaxing the ramp rate. A multiobjective dynamic optimization problem is solved using a lexicographic approach that minimizes ramp rate relaxation and maximizes efficiency while satisfying stress constraints, avoiding spraying to saturation, and maintaining main steam and reheat steam temperature within bounds. It was observed that the optimal ramp rate can be highly nonlinear as opposed to the industry-standard linear ramp rate. Nonlinear optimal ramp-rate profiles not only help to avoid stress constraints that may be unavoidable by using the linear profile but also result in higher efficiency than the linear profile. The study shows that there is a strong tradeoff between the relaxation in the plant ramp rate and the time-average thermal efficiency.

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Use of steam jet booster as an integration strategy to operate a natural gas combined cycle with post-combustion CO2 capture at part-load

Cited by 7 publications

References 16 publications

Operating flexibility of natural gas combined cycle power plant integrated with post-combustion capture

Operating flexibility of natural gas combined cycle power plant integrated with post-combustion capture

Evaluation of Novel Configurations of Natural Gas Combined Cycle (NGCC) Power Plants for Load-Following Operation using Dynamic Modeling and Optimization

Multiobjective Dynamic Optimization for Optimal Load-Following of Natural Gas Combined Cycle Power Plants under Stress Constraints

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