Abstract
In future energy supply systems, hydrogen and electricity may be generated in decarbonized industrial clusters using a common infrastructure for natural gas supply, electricity grid and transport and geological storage of CO2. The novel contribution of this article consists of using sequential combustion in a steam methane reforming (SMR) hydrogen plant to allow for capital and operating cost reduction by using a single post-combustion carbon capture system for both the hydrogen process and the combined cycle gas turbine (CCGT) power plant, plus appropriate integration for this new equipment combination. The concept would be widely applied to any post-combustion CO2 capture process. A newly developed, rigorous, gPROMs model of two hydrogen production technologies, covering a wide range of hydrogen production capacities, thermodynamically integrated with commercially available gas turbine engines quantifies the step change in thermal efficiency and hydrogen production efficiency. It includes a generic post-combustion capture technology – a conventional 30%wt MEA process - to quantify the reduction in size of CO2 absorber columns, the most capital intensive part of solvent-based capture systems. For a conventional SMR located downstream of an H-class gas turbine engine, followed by a three-pressure level HRSG and a capture plant with two absorbers, the integrated system produces ca. 696,400 Nm3/h of H2 with a net power output of 651 MWe at a net thermal efficiency of 38.9%LHV. This corresponds to 34 MWe of additional power, increasing efficiency by 4.9% points, and makes one absorber redundant compared to the equivalent non-integrated system producing the same volume of H2. For a dedicated gas heated reformer (GHR) located downstream of an aeroderivative gas turbine engine, followed by a two-pressure level HRSG and a capture plant with one absorber, the integrated system produces ca. 80,750 Nm3/h of H2 with a net power output of 73 MWe and a net thermal efficiency of 54.7%LHV. This corresponds to 13 MWe of additional power output, increasing efficiency by 13.5% points and also makes one absorber redundant. The article also presents new insights for the design and operation of reformers integrated with gas turbines and with CO2 capture.
Highlights
Electricity and hydrogen are two low-carbon energy vectors expected to play key roles in a zero carbon economy, for example to decarbonize power, buildings, transport and industry sectors
It operates with a mechanical power output of 446 MWe and 43.2%low heating value (LHV) thermal efficiency at ISO ambient conditions and 100% load, with the assumption that the pressure drop across the reformer is compensated by the forced draft fan of the carbon capture plant
The steam methane reformer (SMR) furnace requires to be designed for larger heat transfer surface areas to achieve the equilibrium temperature of 912◦C that leads to a methane conversion of 84%
Summary
Electricity and hydrogen are two low-carbon energy vectors expected to play key roles in a zero carbon economy, for example to decarbonize power, buildings (heating and cooling), transport and industry sectors. Besides being a fuel or raw material for some energy intensive industries, low-carbon hydrogen can replace natural gas for space heating in buildings, industrial processes and back-up power generation and be used as a fuel in heavy transport. Natural gas reforming with carbon capture and storage (CCS) is expected to be a cost-effective option for industrial scale production of low-carbon hydrogen and can help lay the foundation for much higher use of hydrogen across the whole economy (Committee on Climate Change [CCC], 2018). In addition to the supply of natural gas as feedstock for synthesis gas and hydrogen production in a SMR, the combustion of natural gas and the tail gas from hydrogen production and separation provides the thermal energy for the high temperature heat transfer necessary to drive the endothermic reforming reactions in the catalytic reactor
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