Abstract
H2 yield and purity from sorption enhanced steam reforming (SE-SR) are determined by temperature, S:C ratio in use, and feed gas composition in hydrocarbons, N2 and CO2. Gases with high hydrocarbons composition had the highest H2 yield and purity. The magnitude of sorption enhancement effects compared to conventional steam reforming (C-SR), i.e. increases in H2 yield and purity, and drop in CH4 yield were remarkably insensitive to alkane (C1C3) and CO2 content (0.1–10 vol%), with only N2 content (0.4–70 vol%) having a minor effect. Although the presence of inert (N2) decreases the partial pressure of the reactants which is beneficial in steam reforming, high inert contents increase the energetic cost of operating the reforming plants. The aim of the study is to investigate and demonstrate the effect of actual shale gas composition in the SE-SR process, with varied hydrocarbon fractions, CO2 and N2 in the feedstock.
Highlights
All hydrocarbon fuels, be them conventional natural gases, shale gases, i.e., gases trapped in shale formations, associated gases or ‘flare’ gas produced at refineries, can be used in hydrogen (H2) production [1]
This was expected because of the combined effects of decreasing numerator and increasing denominator in Eq (4), as SG mixtures varied from SG1 to SG4
Highest equilibrium H2 yields for SG2-SG4 represented 25%, 45%, and 76% decreases compared to SG1, i.e. the same relative decreases can be calculated between the maximum H2 yield according to Eq (4) for SG1 and the rest of the shale gases
Summary
Be them conventional natural gases, shale gases, i.e., gases trapped in shale formations, associated gases or ‘flare’ gas produced at refineries, can be used in hydrogen (H2) production [1]. A boom in shale gas production [5] in the world foresees that gas will remain the main feedstock of steam reforming in the near term, in contrast to naphtha, which is declining due to high availability of natural gas [5,6]. The 2017 Annual Energy Outlook projected that the U.S (world largest producer of shale gas) natural gas production will increase (an estimate of nearly 4% annual average) as it has since 2005 [7]. Additional techniques of natural gas consumption are desirable (owing to its newfound abundance), including methodologies for proficient H2 production in small scale, ‘distributed fashion at a point of use’. Distributed H2 production will assist in overwhelming one of the key ‘barriers to the implementation of a so called H2 economy’ (the absence of large scale delivery infrastructure) [3]
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