A techno-economic analysis of electric heating integration in fluidized bed boiler
Parkkila, Veera (2024)
2024
Ympäristö- ja energiatekniikan DI-ohjelma - Programme in Environmental and Energy Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2024-12-16
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-2024121111013
https://urn.fi/URN:NBN:fi:tuni-2024121111013
Tiivistelmä
The transition toward a carbon-neutral society has intensified efforts to electrify industrial systems, utilizing the increasing share of renewable energy sources (RES) in electricity generation. Electrification significantly raises the demand for flexible energy solutions, particularly due to the intermittent nature of renewable sources such as wind and solar. Combined heat and power (CHP) plants, which have traditionally relied on combustion processes, now operate with higher frequency in startups and part-load conditions to stabilize the grid. However, these operational changes often lead to reduced efficiency and profitability in boilers. To address these challenges, this Master’s thesis investigates the potential of electrifying fluidized bed boilers within CHP systems. Auxiliary electric heating is proposed to improve boiler profitability, especially during low load operations and periods of low electricity prices.
In collaboration with Valmet Technologies, this study examines the integration of electric heating into a bubbling fluidized bed (BFB) boiler. The research objectives include identifying possible limitations for fluidized bed boiler electrification and optimal placements for electric heaters through a review of relevant literature. Additionally, the changes to boiler operating parameters from the incorporation of electric heating were obtained using Valmet’s boiler design tool. This tool was used to model two electric heating applications: auxiliary air preheating and water vaporization. These cases were analyzed at both low (33 % of maximum continuous rating) and full boiler loads, with varying levels of electric heating applied.
Results indicated that both electric heating placements increase efficiency and reduce fuel consumption and emissions, though they exhibit distinct effects on boiler heat distribution and steam temperature. At full load, the ratio of fuel saved to electricity consumed (measured in watts) was up to 1.5 for vaporization and almost 1.2 for air preheating. Water vaporization led to higher fuel savings but resulted in a drop in live steam temperature. Air preheating, however, maintained a stable live steam temperature but raised the risk of bed agglomeration due to elevated bed temperatures. Nonetheless, the increase in bed temperature can be beneficial during boiler startup.
A financial evaluation assessed the profitability of electric heating across various fuel and electricity price scenarios. The analysis indicated that auxiliary electric heating is economically viable when hourly electricity prices drop by 60% compared to 2023 market levels. According to one study, such low electricity prices could occur by 2030 with an expansion of wind power capacity and moderate growth in electricity demand. In addition, potential future changes in biomass taxation and the inclusion of wood fuel within the emissions trading system (ETS), could significantly increase the benefits associated with electrification investments, making them profitable even under the 2023 electricity price profile. However, the financial comparison revealed that an electrode boiler is substantially more profitable than the proposed electric heating system.
In collaboration with Valmet Technologies, this study examines the integration of electric heating into a bubbling fluidized bed (BFB) boiler. The research objectives include identifying possible limitations for fluidized bed boiler electrification and optimal placements for electric heaters through a review of relevant literature. Additionally, the changes to boiler operating parameters from the incorporation of electric heating were obtained using Valmet’s boiler design tool. This tool was used to model two electric heating applications: auxiliary air preheating and water vaporization. These cases were analyzed at both low (33 % of maximum continuous rating) and full boiler loads, with varying levels of electric heating applied.
Results indicated that both electric heating placements increase efficiency and reduce fuel consumption and emissions, though they exhibit distinct effects on boiler heat distribution and steam temperature. At full load, the ratio of fuel saved to electricity consumed (measured in watts) was up to 1.5 for vaporization and almost 1.2 for air preheating. Water vaporization led to higher fuel savings but resulted in a drop in live steam temperature. Air preheating, however, maintained a stable live steam temperature but raised the risk of bed agglomeration due to elevated bed temperatures. Nonetheless, the increase in bed temperature can be beneficial during boiler startup.
A financial evaluation assessed the profitability of electric heating across various fuel and electricity price scenarios. The analysis indicated that auxiliary electric heating is economically viable when hourly electricity prices drop by 60% compared to 2023 market levels. According to one study, such low electricity prices could occur by 2030 with an expansion of wind power capacity and moderate growth in electricity demand. In addition, potential future changes in biomass taxation and the inclusion of wood fuel within the emissions trading system (ETS), could significantly increase the benefits associated with electrification investments, making them profitable even under the 2023 electricity price profile. However, the financial comparison revealed that an electrode boiler is substantially more profitable than the proposed electric heating system.