![]() However, the high thermal inertia of this material slows down the load following capabilities of the plant ( Lockwood, 2013). The high fuel flexibility is made possible by a large proportion of inert particles in the fluidized bed, e.g., sand and ash. The most common approach for co-combustion is direct co-combustion ( Al-Mansour and Zuwala, 2010 Basu et al., 2011), where the fuels are combusted in the same furnace, which causes low capital costs for retrofitting existing power plants. CFB co-combustion of several fuels can reduce operating costs by responding to regional and seasonal fuel availability and has a large potential for CO 2 emission reduction at low costs ( Sami et al., 2001 Hansson et al., 2009 Werther, 2009 Al-Mansour and Zuwala, 2010). It can be used both on a small scale ( Yates and Lettieri, 2016) for decentralized solutions and on a centralized level with an electrical power of up to 600 MW el ( Jäntti et al., 2012 Lyu et al., 2019). It is a highly efficient technology ( Grace et al., 1997 Oka, 2003 Lockwood, 2013) and is suitable to combust solid fuels with very different mechanical, physical, and chemical properties ( Walter and Epple, 2017 Peters et al., 2020). Carbon capture processes such as chemical looping ( Ströhle et al., 2014 Ströhle et al., 2015 Ohlemüller et al., 2017 Ohlemüller et al., 2018), calcium looping ( Helbig et al., 2017 Hilz et al., 2019 Haaf et al., 2020 Ströhle et al., 2020), or integrated gasification combined cycle ( Descamps et al., 2008 Cormos, 2012 Heinze et al., 2018 Heinze et al., 2019) can be used for this purpose, but retrofitting power plants or building new plants is costly and time-consuming.ĬFB combustion of solid fuels can be a cost-effective and rapidly applicable option for this particular task. At the same time, the CO 2 emissions of these processes should be as low as possible, i.e., they require high efficiency and they should be able to utilize fuels from renewable sources such as biomass and waste-derived fuels. Faster load changes become necessary and the minimum load of the technologies must be reduced. The demand for the ability of these technologies to perform faster load cycling operations will increase as the development of fluctuating energy sources progresses. One way to integrate these intermittent energy sources into the energy market is to use conventional technologies that can provide electrical energy on demand. These technologies have in common that they are not suitable for baseload operation due to their fluctuating electricity supply ( Paraschiv et al., 2014). The worldwide installed capacity of power from wind and photovoltaics increased from 183 GW el in 2009 ( Paraschiv et al., 2014) to 1,096 GW el in 2018 ( Renewables, 2019). ![]() Fluctuating energy sources such as solar and wind play a decisive role in this context. The usage of renewable energy sources in the energy sector is necessary to mitigate climate change ( Edenhofer et al., 2011). Based on the results, concepts were developed to accelerate load ramping by controlling the hydrodynamic conditions and the temperature on the fireside. The step size of the fuel mass flow had a positive effect on the load change rate. ![]() The step input of the primary air had a large influence on the load ramps, as it strongly affects the solids concentration in the upper furnace. In a 1 MW th pilot CFB combustor fifteen load changes were performed with a varying step input of the primary air, the secondary air, and the fuel mass flow. Co-combustion of lignite, straw, and refuse derived fuel (RDF) was carried out. This study investigates the influence of the operating parameters of the fire side on the speed of load changes on the waterside. A circulating fluidized bed (CFB) boiler is a suitable solution due to its fuel flexibility, but the thermal inertia of the fluidized bed can have negative effects on the load following capabilities. The integration of intermittent renewable energy sources into the electricity market requires flexible and efficient technologies that compensate for the fluctuating electricity demand.
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