Abstract
The competitiveness of biofuels may be increased by integrating biomass gasification plants with electrolysis units, which generate hydrogen to be combined with carbon-rich syngas. This option allows increasing the yield of the final product by retaining a higher amount of biogenic carbon and improving the resilience of the energy sector by favoring electric grid services and sector coupling. This article illustrates a techno-economic comparative analysis of three flexible power and biomass to methanol plants based on different gasification technologies: direct gasification, indirect gasification, and sorption-enhanced gasification. The design and operational criteria of each plant are conceived to operate both without green hydrogen addition (baseline mode) and with hydrogen addition (enhanced mode), following an intermittent use of the electrolysis system, which is turned on when the electricity price allows an economically viable hydrogen production. The methanol production plants include a gasification section, syngas cleaning, conditioning and compression section, methanol synthesis and purification, and heat recovery steam cycle to be flexibly operated. Due to the high oxygen demand in the gasifier, the direct gasification-based plant obtains a great advantage to be operated between a minimum load to satisfy the oxygen demand at high electricity prices and a maximum load to maximize methanol production at low electricity prices. This allows avoiding large oxygen storages with significant benefits for Capex and safety issues. The analysis reports specific fixed-capital investments between 1823 and 2048 €/kW of methanol output in the enhanced operation and LCOFs between 29.7 and 31.7 €/GJLHV. Economic advantages may be derived from a decrease in the electrolysis capital investment, especially for the direct gasification-based plants, which employ the greatest sized electrolyzer. Methanol breakeven selling prices range between 545 and 582 €/t with the 2019 reference Denmark electricity price curve and between 484 and 535 €/t with an assumed modified electricity price curve of a future energy mix with increased penetration of intermittent renewables.
Highlights
Within a carbon-constrained economy that aims to substantially reduce CO2 emissions, biogenic carbon is bound to be a scarce resource with high economic value
The main conclusions of the work are that 1) high capacity factors of the electrolysis system are necessary in order to provide costcompetitive e-methanol to the market and to amortize the high capital cost of the electrolysis unit, 2) the enhanced reactor design has to be preferred over the baseline reactor design because of the higher relative cost of hydrogen from electrolysis compared to the capital cost of oversizing the methanol synthesis unit, 3) the attractiveness of operating this kind of plants in a flexible way may increase significantly in future scenarios with very high penetration of intermittent renewables, leading to low average electricity prices, and periods of very high peak prices
The dual fluidized bed configurations (i.e., indirect gasification (IG) and sorption-enhanced gasification (SEG)) exhibit better economic performance at high electricity prices when free biomass is available because the feedstock cost has a higher share on the LCOF in the IG and SEG cases compared to their direct gasification (DG) counterfactuals
Summary
Within a carbon-constrained economy that aims to substantially reduce CO2 emissions, biogenic carbon is bound to be a scarce resource with high economic value. The main conclusions of the work are that 1) high capacity factors of the electrolysis system are necessary in order to provide costcompetitive e-methanol to the market and to amortize the high capital cost of the electrolysis unit, 2) the enhanced reactor design has to be preferred over the baseline reactor design because of the higher relative cost of hydrogen from electrolysis compared to the capital cost of oversizing the methanol synthesis unit, 3) the attractiveness of operating this kind of plants in a flexible way may increase significantly in future scenarios with very high penetration of intermittent renewables, leading to low average electricity prices, and periods of very high peak prices. The economic competitivity of flexibly operated plants when integrated with the electricity market is discussed, compared to inflexible plants conceived to operate with constant hydrogen input
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