Effective use of hydrogen sulfide and natural gas resources available in the Black Sea for hydrogen economy

In this article, we propose a novel system to effectively deploy an integrated fuel processing system for hydrogen sulfide and natural gas resources available in the Black Sea to be used for a quick transition to the hydrogen economy. In this regard, the proposed system utilizes offshore wind and offshore photovoltaic power plants to meet the electricity demand of the electrolyzer. A PEM electrolyzer unit generates hydrogen from hydrogen sulfide that is available in the Black Sea deep water. The generated hydrogen and sulfur gas from hydrogen sulfide are stored in high-pressure tanks for later use. Hydrogen is blended with natural gas, and the blend is utilized for industrial and residential applications. The investigated system is modeled with the Aspen Plus software, and hydrogen production, blending, and combustion processes are analyzed accordingly. With the hydrogen addition up to 20% in the blend, the carbon dioxide emissions of combustion decrease from 14.7 kmol/h to 11.7 kmol/h, when the annual cost of natural gas is reduced from 9 billion $ to 8.3 billion $. The energy and exergy efficiencies for the combustion process are increased from 84% to 97% and from 62% to 72%, respectively by a 20% by volume hydrogen addition into natural gas.     

Fire prevention technical rule for gaseous hydrogen transport in pipelines

This paper presents the current results of the theoretical and experimental activity carried out by the Italian Working Group on the hydrogen fire prevention safety issues in the field of the hydrogen transport in pipelines [Grasso N, Ciannelli N, Pilo F, Carcassi M, Ceccherini F. Fire prevention technical rule for gaseous hydrogen refuelling stations. Proceedings of the International Conference on Hydrogen Safety, 8–10 September 2005, Pisa, Paper 420064]. From the theoretical point of view a draft document has been produced beginning from the Italian regulations in force on the natural gas pipelines; these have been reviewed, corrected and integrated with instructions suitable to use with hydrogen gas. From the experimental point of view a suitable apparatus has been designed and installed at the University of Pisa; this apparatus will allow simulations of hydrogen releases from a pipeline with or without ignition of the hydrogen–air mixture. The experimental data will help the completion of the above-mentioned draft document with the instructions about the safety distances. However, in the opinion of the Group, the work on the text contents is concluded and the document is ready to be discussed with the Italian stakeholders involved in the hydrogen applications.     

Flammability limits of hydrogen-enriched natural gas

This paper reports both the lower and upper flammability limits of hydrogen-enriched natural gas with hydrogen fractions of 20%, 40%, 60% and 80% respectively as well as these of natural gas and hydrogen, measured by using a constant volume combustion chamber together with a high-speed schlieren photographic system. Based on investigating pressure rise history inside the combustion chamber as well as flame photos, the effect of hydrogen enrichment on the flammability characteristics is discussed. Our experimental results show that the flammability limits of methane-hydrogen mixtures can be used for hydrogen-enriched natural gas as long as their hydrogen fractions are the same. In this paper, the flammability data of methane-hydrogen mixtures available in the literature are reviewed. Correlations for both the lower and upper flammability limits of methane-hydrogen mixtures are summarized.     

Blue sky mining: Strategy for a feasible transition in emerging countries from natural gas to hydrogen

Natural gas is often considered a transition fuel to a deep decarbonized world. However, for this to happen, new technologies should be fostered, among which a natural gas-based H₂ industry can become a key-option. This study tests the hypothesis that the development of a natural gas-based H₂ industry equipped with CO₂ capture can monetize natural gas remaining resources, mitigate CO₂ emissions and facilitate the transition to the renewable energy-based H₂. To do that, this study evaluates a stepwise strategy for setting up the development of H2, departing from the idle capacity in the existing natural gas industry, to progressively create a H₂ independent supply. Findings indicated that this strategy can be feasible, according to the case study assessed at relatively moderate crude oil prices. Nevertheless, CO₂ storage can become a constraint to deal with the co-produced CO₂ from the steam methane reforming units. Therefore, it is worth developing storage options.     

Dynamic behaviour of non-isothermal compressible natural gases mixed with hydrogen in pipelines

This paper focuses on non-isothermal transient flow in mixed hydrogen–natural gas pipelines. The effect of hydrogen injection into natural gas pipelines has been investigated in particular the pressure and temperature conditions, Joule–Thomson effect, linepack and energy consumption of the compressor station. The gas flow is described by a set of partial differential equations resulting from the conservation of mass, momentum and energy. Real gas effects are determined by the predictive Soave–Redlich–Kwong group contribution method. The Yamal-Europe gas pipeline on Polish territory has been selected as case study.     

The influences of hydrogen on the performance and emission characteristics of a heavy duty natural gas engine

Because blending hydrogen with natural gas can allow the mixture to burn leaner, reducing the emission of nitrogen oxide (NO_x), hydrogen blended with natural gas (HCNG) is a viable alternative to pure fossil fuels because of the effective reduction in total pollutant emissions and the increased engine efficiency.In this research, the performance and emission characteristics of an 11-L heavy duty lean burn engine using HCNG were examined, and an optimization strategy for the control of excess air ratio and of spark advance timing was assessed, in consideration of combustion stability. The thermal efficiency increased with the hydrogen addition, allowing stable combustion under leaner operating conditions. The efficiency of NO_x reduction is closely related to the excess air ratio of the mixture and to the spark advance timing. With the optimization of excess air ratio and spark advance timing, HCNG can effectively reduce NO_x as much as 80%.     

The recent areas of applicability of palladium based membrane technologies for hydrogen production from methane and natural gas: A review

In the wake of the devastating consequences of climate change, many countries are searching for alternative renewable energy. Hydrogen, the most abundant element on earth, is an alternative clean and non-toxic energy source. Palladium-based membranes and their alloys are categorized as inorganic metallic membranes with the highest selectivity and permeation rate for hydrogen production. Pd-based membranes have great potential for resolving environmental concerns and adverse side effects of greenhouse gases resulting from industrial processes. This paper analyses Pd-based membranes and their industrial applications while focusing on natural gas and methane as non-renewable feedstocks for hydrogen production. Steam reforming of natural gas and methane, partial oxidation reaction, auto thermal reforming, dry reforming, and gas to liquid process are among the processes that take place in a Pd-based membrane reactor and are discussed in this paper. Finally, all the ongoing research and development on both laboratory and industrial scales are reviewed.     

Study on the stratification of the blended gas in the pipeline with hydrogen into natural gas

When blending hydrogen into existing natural gas pipelines, the non-uniform concentration distribution caused by the density difference between hydrogen and natural gas will result in the fluctuations of local hydrogen partial pressure, which may exceed the set one, leading to pipeline failure, leakage, measurement error, and terminal appliance. To solve the problem, the H₂–CH₄ stratification in the horizontal and undulated pipe was investigated experimentally and with numerical simulations. The results show that in the gas stagnant situation, hydrogen-methane blending process will cause an obvious stratification phenomenon. The relations between the elevation, pressure, hydrogen fraction, etc., and the gas stratification are figured out. Moreover, even when the blended gas flows at a low rate, the hydrogen-caused stratification should also be considered. Thereafter, the blended gas should be controlled into a situation with low pressure and high speed, which could help to set the pressure, speed, the fraction of H₂.     

Engine characteristics of emissions and performance using mixtures of natural gas and hydrogen

An evaluation was performed on the efficiency and emissions from an engine fuelled with compressed natural gas (CNG) and a mixture of natural gas and hydrogen, respectively. The mixtures of CNG and hydrogen were named HCNG.     

Experimental and numerical study of hydrogen addition in a natural gas heavy duty engine for a bus vehicle

Hydrogen added to natural gas improves the process of combustion with the possibility to develop engines with higher performance and lower environmental impact. In this paper experimental and numerical analyses on a multi cylinder stoichiometric heavy duty engine, fuelled with natural gas–hydrogen blends, are reported. Some constrains on hydrogen content and maximum load achievable have limited the scope of investigation. A specific modelling of the reference engine was developed to extend the study at full load condition and at higher hydrogen content. The results showed a higher combustion speed when hydrogen content in the fuel is increased. However, the positive effect of shorter combustion duration on thermal efficiency is mitigated by higher wall heat loss, due to higher combustion temperatures. Therefore lower CO₂ emissions are due only to the substitution of natural gas with hydrogen, making crucial the way of hydrogen producing to have a benefit on well-to-wheel CO₂ emissions.     

An MILP model for the reformation of natural gas pipeline networks with hydrogen injection

A mixed integer linear programming (MILP) model is proposed for the reformation of natural gas pipelines. The model is based on the topology of existing pipelines, the load and pressure at each node and the design factors of the region and minimizes the annual substitution depreciation cost of pipelines, the annual construction depreciation cost of compressor stations and the operating cost of existing compressor stations. Considering the nonlinear pressure drop equations, the model is linearized by a piecewise method and solved by the Gurobi optimizer. Two cases of natural gas pipeline networks with hydrogen injection are presented. Several adjustments are applied to the original natural gas pipeline network to ensure that our design scheme can satisfy the safety and economic requirements of gas transportation. Thus, this work is likely to serve as a decision-support tool for the reformation of pipeline networks with hydrogen injection.     

Blending blue hydrogen with natural gas for direct consumption: Examining the effect of hydrogen concentration on transportation and well-to-combustion greenhouse gas emissions

Jurisdictions are looking into mixing hydrogen into the natural gas (NG) system to reduce greenhouse gas (GHG) emissions. Earlier studies have focused on well-to-wheel analysis of H₂ fuel cell vehicles, using high-level estimates for transportation-based emissions. There is limited research on transportation emissions of hythane, a blend of H₂ and NG used for combustion. An in-depth analysis of the pipeline transportation system was performed for hythane and includes sensitivity and uncertainty analyses. When hythane with 15% H₂ is used, transportation GHG emissions (gCO2eq/GJ) increase by 8%, combustion GHG emissions (gCO2eq/GJ) decrease by 5%, and pipeline energy capacity (GJ/hr) decreases by 11% for 50–100 million m³/d pipelines. Well-to-combustion (WTC) emissions increase by 2.0% without CCS, stay the same with a 41% CCS rate, decrease by 2.8% for the 100% CCS scenario, and decrease by 3.6% in the optimal CO₂-free scenario. While hythane contains 15% H₂ by volume only 5% of the gas’ energy comes from H₂, limiting its GHG benefit.     

Optimization of hydrogen production by filtration combustion of natural gas by water addition

The effect of adding steam during filtration combustion of natural gas–air mixtures was studied with the aim to evaluate the optimization of hydrogen production. Temperature, velocity, chemical products of combustion waves, and conversion from fuel to H₂ and CO were evaluated in the range of equivalence ratio (φ) from stoichiometric (φ = 1.0) to φ = 3.0 and steam content in the mixture from 0% to 39%, at filtration velocities from 12 to 25 cm/s. Numerical simulation was carried out using GRI-MECH 3.0. Results suggest that H₂ and CO concentrations, dominant for rich and ultrarich combustion, are products from partial oxidation and steam natural gas reforming processes. Experimental and numerical results show that hydrogen yield increase with an increase of steam content in the natural gas–air mixtures.     

Simulation of a hydrogen/natural gas engine and modelling of engine operating parameters

At the present work for improving the engine performance and decrease of emissions, a port injection gasoline engine is converted into direct injection. Engine performance behavior was investigated by AVL Fire software with adding hydrogen to natural gas from 0% up to 30%. Validation of the simulated model and experimental results show good confirmation. To determine the relationship between independent variables engine speed, ignition timing, injection timing and H₂% versus the dependent variables including engine performance parameters, specific fuel consumption, CO and statistical analysis models were used. Comparison between different errors models shows that Radial basis function model with training algorithm Bayesian regularization back propagation can estimate better engine performance variables. The results showed that adding hydrogen to natural gas cause the output power, torque, fuel consumption efficiency increase and specific fuel consumption drop. Also, CO decreases when ignition and injection timing be advanced and engine speed reaches to its largest.     

Israel—New natural gas producer in the Mediterranean

In 2009 and 2010, major offshore natural gas reserves were discovered near the State of Israel. This article examines Israel's newly discovered natural gas reserves and the implications of this discovery for Israel, the Middle East, and the Mediterranean region. The article will discuss Israel's energy security approach; the role of natural gas in Israel's energy consumption patterns; the organization of Israel's natural gas sector; regional political and security implications of the natural gas discoveries; the prospects for export, and the outlook for various natural gas markets. These new discoveries significantly improve Israel's energy security. They may also spur Israel to develop technologies related to utilization of natural gas in a variety of sectors, such as transportation. The discoveries may contribute to the emergence of a number of maritime border delimitation conflicts in the Eastern Mediterranean. At current volumes, the Israeli discoveries will not be a game-changer for gas markets in southern Europe or liquefied natural gas (LNG) markets. However, they will lead to expanded natural gas consumption in the region. In addition, offshore exploration efforts in Israel and in neighboring countries are intensifying. Additional discoveries may turn the Eastern Mediterranean region into a new source of natural gas and oil.     

Auto-ignition and flame stabilization of hydrogen/natural gas/nitrogen jets in a vitiated cross-flow at elevated pressure

The influence of natural gas (NG) on the auto-ignition behavior of hydrogen (H₂)/nitrogen (N₂) fuel jets injected into a vitiated cross-flow was studied at conditions relevant for practical combustion systems (p = 15 bar, T_cross-flow = 1173 K). In addition, the flame stabilization process following auto-ignition was investigated by means of high-speed luminosity and shadowgraph imaging. The experiments were carried out in an optically accessible jet in cross-flow (JICF) test section. In a H₂/NG/N₂ fuel mixture, the fraction of H₂ was stepwise increased while keeping the N₂ fraction approximately constant. Two different jet penetration depths, represented by two N₂ fraction levels, were investigated. The results reveal that auto-ignition kernels occurred even for the lowest tested H₂ fuel fraction (XH_2/NG=XH₂/(XH₂+XNG)=80%)$\left(X_{{\text{H}}_2/\text{NG}}=X_{{\text{H}}_2}/\left(X_{{\text{H}}_2}+X_{\text{NG}}\right)=80\%\right)$, but did not initiate a stable flame in the duct. Increasing XH_2/NG$X_{{\text{H}}_2/\text{NG}}$ decreased the distance between the initial position of the auto-ignition kernels and the fuel injector, finally leading to flame stabilization. The H₂ fraction for which flame stabilization was initiated depended on jet penetration; flame stabilization occurred at lower H₂ fractions for the higher jet penetration depth (XH_2/NG$X_{{\text{H}}_2/\text{NG}}$ = 91% compared to 96%), revealing the influence of different flow fields and mixing characteristics on the flame stabilization process. It is hypothesized that the flame stabilization process is related to kernels extending over the duct height and thus altering the upstream conditions due to considerable heat release. This enabled subsequent kernels to occur close to the fuel injector until they could finally stabilize in the recirculation zone of the jet lee.     

Conversion of the UK gas system to transport hydrogen

One option to decarbonise residential heat in the UK is to convert the existing natural gas networks to deliver hydrogen. We review the technical feasibility of this option using semi-structured interviews underpinned by a literature review and we assess the potential economic benefits using the UK MARKAL energy systems model. We conclude that hydrogen can be transported safely in the low-pressure pipes but we identify concerns over the reduced capacity of the system and the much lower linepack storage compared to natural gas. New hydrogen meters and sensors would have to be fitted to every building in a hydrogen conversion program and appliances would have to be converted unless the government was to legislate to make them hydrogen-ready in advance.     

Effect of hydrogen addition on the route preference in natural gas flow in regular,horizontal T-junctions

During the transport of natural gas through pipelines small amounts of condensate can be formed due to temperature and pressure changes. If this natural gas/condensate flow arrives at a regular, sharp-edged T-junction in the pipeline system an interesting phenomenon may be observed i.e. unequal phase splitting of gas and condensate. In this paper its has been shown that the addition of hydrogen into a natural gas stream results in a different splitting behaviour in comparison with the natural gas flow without hydrogen addition.