Complementing existing CHP plants using biomass for production of hydrogen and burning the residual gas in a CHP boiler

ABSTRACT

Biorefinery systems at combined heat and power (CHP) plants represent numerous technical, economic and environmental benefits by utilizing the existing biomass handling infrastructure and producing biofuels together with heat and power. This study evaluates the economic feasibility of integrating biomass gasification to an existing CHP plant. Integration includes biomass gasification with downstream processing of the synthesis gas to remove particles and tars, condense out water, remove CO₂ and use membrane filtration (polyamide membrane) to extract hydrogen. The separated residual gas components are utilized as extra fuel to the boiler in the CHP plant. Approximately 58.5 MW_th of synthesis gas can be produced from a 90 MW_th plant that represents 16.4 MW_th of hydrogen. The rest of the heating value of produced synthesis gas (in the form of methane and carbon monoxide) is utilized for heat and power production. From an economic perspective, the production cost of hydrogen is estimated to be 0.125–0.75 €/kg. This can be compared to the US governments goal that H₂ produced by wind power plus electrolyzers should have a maximum cost of 2.8–3.4 €/kg. The lower cost is for a unit operating at 3 bar and assuming that the costs are split between H₂ and the syngas residue that is combusted, while the higher prices assume an atmospheric gasifier and all costs are put on the H₂ produced.

KEYWORDS:

• Gasification
• CHP
• hydrogen production
• economic analysis

Acknowledgments

We thank our cooperation partners at Malarenergi, Fredrik Starfelt and our master students Linus, Victor, and Emil Nilsson. BioRegional MiniMills UK as well as Swedish Energy Agency and KKS-foundation have supported the gasification work financially.

Disclosure statement

No potential conflict of interest was reported by the authors.