Blending Hydrogen into Natural Gas Pipeline Networks: A Review of Key Issues

Abstract

xii cost of recompressing the natural gas to the original natural gas pipeline pressure can be avoided. The resulting estimated extraction cost for a 10% concentration and 80% recovery factor is $0.3-$1.3/kg, with the range resulting from economies of scale for a system size or recovery rate of 1,000-100 kg/day (see Figure 18). These costs per kilogram are reduced by approximately 10% if the hydrogen concentration is increased to 20%. PSA extraction could therefore become a relatively small cost component of the total delivered cost of hydrogen if the extraction is done at a pressure-reduction facility. With major pressure reduction stations often located near large urban areas, downstream extraction could prove to be an economical delivery option. It has been estimated that there are 11,200-14,800 metering and pressure regulating stations with inlet pressures greater than 300 psig in the United States (see section 3.1), and 34,600-56,700 stations with inlet pressures between 100 and 300 psig. Approximately 23%-25% of the stations with inlet pressures greater than 300 psig are contained within vaults, which is typical for stations located near urban or suburban areas. Therefore, it is likely that several thousand high-pressure city gate stations are located in close proximity to large U.S. urban areas where natural gas is transferred from transmission lines to distribution lines, and many of these may be candidates for hydrogen extraction.

The Technical and Energetic Challenges of Separating (Photo)Electrochemical Carbon Dioxide Reduction Products

“…Natural gas blending rules also limit the amount of H 2 in pipelines in order to minimize H 2 leaks and metal embrittlement, although compositional tolerances are unclear. Various studies indicate different maximum blending levels (Altfeld and Pinchbeck, 2013;Melaina et al, 2013;Hodges et al, 2015); the overall conclusion is that the safe level for H 2 blended into natural gas pipelines is ≤20%, and must be assessed on a case-by-case basis due to differences in pipeline materials, operating pressures, and states of repair. Other impurities that must be completely removed from natural gas (e.g., H 2 S, Hg, oils) and/or biogas (amine, chlorine and siloxane compounds) (Luostarinen et al, 2011;Götz et al, 2016;Corvini et al, no date) are not produced from CO 2 RR so would not be problematic unless contamination or degradation of materials occurred.…”

Transition of Future Energy System Infrastructure; through Power-to-Gas Pathways

“…This limitation which is based on the fraction of the hydrogen allowable in the natural gas can be in the range of 5 to 20% for different applications [40][41][42][43]. Note that even with these concentrations, there is a need to build and install many electrolysers [31].…”

“…Safety and risk associated to blending hydrogen into natural gas: Safety and risk analysis are two important issues that should be considered when blending hydrogen into natural gas pipelines that depend on the hydrogen concentration, pipeline types and material, as well as failure mode conditions [40]. The main concern regarding the risk of blending hydrogen into natural gas pipelines is the possibility of ignition.…”

“…The main concern regarding the risk of blending hydrogen into natural gas pipelines is the possibility of ignition. The literature [40,46,47] shows that natural gas systems enjoy a lower risk of severe accidents than large-scale power plants such as coal and nuclear, however, they pose a higher risk than renewable systems such as solar PV and wind [47]. Moreover, the risk associated with the transmission and distribution pipelines may be different, for instance, the distribution systems should be reassessed for the severity of the explosion, when near urban areas.…”

Electrochemical Hydrogen Compression: Efficient Pressurization Concept Derived from an Energetic Evaluation

“…For both scenarios hydrogen is compressed from 0.1 to 0.2 MPa absolute pressure, for case i) pure hydrogen is supplied and in case ii) a gas mixture with 5% H 2 in N 2 , in order to simulate the dilution in the natural gas grid where the 5% are considered an upper limit with respect to today's regulations. 32 Thus compression ratios of 2 and 40 are realized in scenarios i) and ii), respectively.…”