Profitability analysis of H2 production by water electrolysis in an integrated oxy-fuel combustion thermal power plant

Abstract

Integrating oxy-fuel combustion into waste-to-energy power plants with electrolysis is a promising strategy to address waste management and reduce CO₂ emissions. However, the economic implication of retrofitting a combined heat and power plant into oxy-fuel should be compared to its conventional air-fired strategy to enhance investments for carbon capture strategies. This paper investigates the integration of a waste-to-energy combined heat and power plant with an alkaline electrolyzer for oxy-fuel combustion and its economic competitiveness against the non-retrofitted air-fired combined heat and power plant. An air-fired power plant and its retrofitting into oxy-fuel combustion were modeled using AspenPlus based on the data from a real power plant (250 MW${}_{\text{th}}$), situated in Finland. Retrofitting the chosen air-fired power plant required additional electric power of 320 MW${}_{\text{el}}$, supplemented by the grid, to satisfy the demand of the electrolyzer (372 MW). Nevertheless, the implementation of oxy-fuel combustion and waste heat recovery from the electrolyzer increased the district heating output from 154  to 350 MW${}_{\text{th}}$. Owing to a sensitivity analysis, it was found that the optimal exploitation of the thermal energy in the flue gas was achieved with a recirculation fraction of 70 %–80 % (70.5 % in this study). The oxy-fuel system produced a mass flow rate of CO₂ equal to 18.4 kg/s with a purity of 99.2 mol% and 2.06 kg/s of pure H₂ with a molar ratio of 2.5:1 (H₂–CO₂). The price of H₂, produced by the oxy-fuel retrofitted system, to obtain the same profit as the conventional air-fired combined and heat power plant was 1.57 EUR/kg. Due to its economic competitiveness, the proposed retrofitting into oxy-fuel combustion can be implemented on large scale, thus making a significant impact on reducing CO₂ emissions.