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

Abstract

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.

Transient CO2 capture for open-cycle gas turbines in future energy systems

“…The pressure drop and the consequent loss in purity has an effect on the compression system required to pressurise the CO2 for pipeline transportation and storage [68,69]. More information on the effects of transient CO2 production on a compression system can be found in Spitz et al [23] and Mechleri, et al [25]. CO 2 Captured (tCO 2 /Operation)…”

“…It can even be economically beneficial by exploiting higher electricity prices during peak periods [21]. Several simulation based studies have investigated operational flexibility of coal-and gas-PCC, focussing on comparing operating strategies [22,23,24], developing process control strategies [25,26], and multi-period optimisation [27]. Montañés et al [28] identifies the operational requirements of flexible CO2 capture, and concluded future work should consist of validated dynamic process models evaluating various transient operating scenarios, to discover potential bottlenecks during flexible operation.…”

Coordinated G&TEP and carbon capture and storage expansion planning model for emission constrained power systems

“…For instance, the work in [7] investigated the CCS retrofitting of coal power plants. In [8], the integration of CCS in a natural gas combined cycle power plant was investigated. The use of CCS technology with thermal steam cycle power plant fuelled by bagasse was also investigated in [9].…”

Controlling capture plants to avoid CO2 emissions penalties during peak load demand

“…In future, requirements of flexible operation from power stations integrated with carbon capture plants will be highly increased (Spitz, et al 2019). As many of the CCS plants integrated with power plants will have to operate at low load factors, costs will increase at an increasing rate as the emissions are reduced (Davison, 2011).…”