The latest IFRF ‘Topic-Orientated Technical Meeting’ (TOTeM) took place last week. Organised jointly by the Gas- und Wärme-Institut Essen e. V. (GWI) and IFRF, and hosted by GWI at its facilities in Essen, Germany, TOTeM 44 was on the subject of ‘Gaseous fuels for industry and power generation: challenges and opportunities’. The meeting covered the future of a broad range of gaseous fuels in three sessions addressing: natural gas quality and its impact on large-scale gas-fired equipment; the use of hydrogen or hydrogen/natural gas mixtures (e.g. in ‘power-to-gas’ applications); and the utilisation of biogas or syngas in industrial furnaces or for power generation.
The participants were welcomed by GWI’s Jörg Leicher, who introduced GWI before setting the scene for the future of gaseous fuels. He re-examined the IEA’s use of the term “golden age of gas” (coined in 2011 as a scenario in its World Energy Outlook): While the future for gas is bright in many regards (the abundance of conventional/non-conventional gas worldwide; its lower emissions of CO2, NOx, SOx and particulate matter compared with coal; its flexible use in turbines and engines complementing the use of renewable energy sources; and the fact that it is a well-established source of energy in a range of sectors), it also faces a number of challenges (it is a non-renewable fossil fuel emitting CO2 at point-of-use – although the use of hydrogen in ‘power-to-gas’ (P2G) schemes and biogas present interesting options; there are environmental and political concerns relating to its production, i.e. fracking, leakage, etc.; and although it is used in many applications, there are different requirements for the gas in terms of its quality and constituents).
Terry Williams of Orbital Gas Systems (sponsor of the TOTeM – see separate article) presented the keynote address of the meeting. This excellent ‘tour de force’ covered all of the range of gaseous fuels, as well as identifying the key challenges and opportunities associated with them. After providing the background to gas quality changes in terms of the current drivers of gas composition changes, Terry used the familiar ‘Dutton diagram’ (i.e. Wobbe Index versus percentage of non-methane components) to examine the interchangeability of a range of gaseous fuels – natural gas via pipeline interconnectors, vaporised LNG, shale gas, H2/CH4 mixes and biogas/biomethane. The variability of the Wobbe Index can be significant in all such cases (5-15%), and in terms of the Dutton diagram (representing conventional wisdom on gas interchangeability), many traded LNGs, most US shale gases and H2/CH4 mixes where the H2 accounts for ~20% or above, fall outside the acceptable operational ‘envelope’ on the graph. Such variability of Wobbe Index, calorific value, relative density and chemical composition of gaseous fuels emphasises the need for accurate and responsive gas quality monitoring – Terry reviewed the current options including, of course, Orbital’s GasPTi! The keynote presentation concluded by identifying the main challenges and opportunities for combustion systems in industrial and power generation applications. Terry identified the main challenges as: the increased variability of gas composition and quality – exacerbated by the increasing diversity of geographical sources; the addition of hydrogen in natural gas impacting efficiency, flame stability and emissions; growing concerns about climate change leading to more stringent emission reduction targets; all leading to an increasing requirement for modifying combustion control systems and burner designs to maintain performance. Conversely, opportunities for the future were mainly around embracing the growth in the use of renewable energy sources; innovation to enable biogas combustion in larger systems; and ensuring that the addition of hydrogen to natural gas networks does not have adverse effects on burner performance.
This overview set the context for the three sessions on natural gas quality, hydrogen, and biogas and syngas.
Natural gas quality:
Kris de Wit of ARGB (now renamed Gas.be) described the activities of the CEN Sector Forum Gas (SFGas) Working Group on standardising gas quality, leading to the publication of EN 16726 in December 2015. Kris outlined the coverage of EN 16726, before describing what were the future foci for SFGas – this included the national publication of EN 16726 leading to the withdrawal of national standards, an EU Gas Quality Harmonisation Pilot activity leading to a harmonisation framework, and (in parallel to the CEN process) ENTSOG will analyse the impact and issues of EN 16726 on the complete gas chain and submit a proposal to amend the Network Code on Interoperability and Data Exchange Rules. After reviewing the role of the Madrid Forum (monitoring the development of the Standard), the CEN SFGas WG membership and governance structure, Kris highlighted a couple of issues that need to be addressed and how these were being taken forward – this included the issues around the use of the Wobbe Index and gaining a better understanding of national/local/sectoral constraints.
Jörg Leicher of GWI talked about the impact of gas quality on industrial combustion processes. Having illustrated the importance of natural gas to industrial processes (and vice versa), Jörg highlighted the factors that had caused more attention to be given to gas quality in recent years. Gas quality regulations in Germany and other EU states were reviewed, with some interesting perspectives on the focus on the Wobbe Index, despite its potential variation – reinforced by considering the results of the MARCOGAZ Survey. The role of the Wobbe Index in characterising gas quality was further considered before examining some work done by GWI on local Wobbe Index and net CV which demonstrated the variability (not necessarily related), the major changes that occurred during the study period, the importance of considering WI along with relative density and GCV, sensitivity assessments, etc. Other studies in Europe and the USA were referenced concerning gas quality variations and consequential damage to burners. Lastly, a study of a regenerative glass-melting furnace was described, indicating that control of the combustion process was possible despite varying gas quality, albeit expensive. Jörg concluded that: industries will have to expect greater fluctuations in gas quality and composition (amplitude and frequency); applications will become more sensitive to gas quality due to a greater degree of specialisation, optimisation and changing requirements; the Wobbe Index is not well-suited to describing the effect of gas quality fluctuations (should be addressed in future gas quality regulations); and for many sensitive situations, advanced monitoring capability is/will be needed.
Berthil Slim of DNV GL described why innovations in fuel-adaptive burner control systems were needed to manage wider gas quality parameters and gas quality fluctuations in the future. He described how a fuel-adaptive burner control system (basic feed-forward control) built with commercially-available components has been successfully demonstrated: The next step is a fuel-adaptive control concept known as ‘Sustainoflame’, which will demonstrate operation in a wide variety of gas quality fluctuation conditions and with weather control. Berthil also described a project where a domestic heating boiler is used as a gas sensor utilising a Honeywell ionisation current control: This worked very well and has led on to Honeywell developing a low-cost solution for smart gas grids. Finally, he described an H2/natural gas burner system feasibility study being conducted in north and west Netherlands, where a gas sensor is linked to the burner’s primary and secondary ports.
PhD student Jon Runyon from the University of Cardiff’s Gas Turbine Research Centre (GTRC) presented the work he is doing on the influence of higher hydrocarbons in LNGs on natural gas flame stability under elevated conditions. Having described the motivation for this research (i.e. GTs having to operate with increasing flexibility due to more intermittent renewable in the energy mix, increasingly stringent emissions regulations and greater fuel flexibility – globally, regionally and locally – due to LNG use), Jon presented the scope and aims of his work characterising flame shape, thermoacoustics and emissions at simulated GT operating conditions using GTRC’s HP Combustion Rig, HP Optical Chamber and HP Generic Swirl Burner. Four LNG ‘mixes’ were tested – ‘BASE’ (100% CH4), ‘MIDNG’ (average LNG composition), ‘FARNG’ (maximum C2H6 for LNG with 10% balancing CH4) and ‘EMIX1’ (85% CH4, 12.6% C3H8, 2.4% N2) – with a range of non-intrusive diagnostic measurements taken. Jon presented the test results for the four LNG mixes considering flame stabilisation under stable operating conditions, fuel composition effects, NOx emissions and reaction zone thickness, and flame stretch effects, drawing conclusions on swirl flame heat release distribution and combustion noise levels and describing ongoing work.
Hydrogen and hydrogen/natural gas mixtures:
Johannes Schaffert of GWI described P2G technologies as a toolbox for ‘sector coupling’ (i.e. overlaying) gas and electricity in the energy sector, pointing out that greater flexibility options exist when looking at integrating power, gas and heat systems. Energy storage is a key attribute in such coupling, with both hydrogen and SNG capable of being stored. In considering the Technology Readiness Levels of ‘power-to-x’ technologies, methane and methanol synthesis from CO2, hydrogen-enriched natural gas (HENG) fed into natural gas grids and water electrolysis hydrogen production emerge as the most promising. Over 40 P2G projects have been developed in Europe (mainly in Germany, the Netherlands and Scandinavia), and Johannes described the Virtual Institute for Power to Gas and Heat (GWI coordinate), the P2G Demo Centre at GWI (under construction in 2017/18), the ene.field project (fuel cell micro-CHP), the Tolerance to Hydrogen project, the EC’s SRORE&GO project and various geo-informational projects looking at mapping electricity and gas grids to examine potential convergence.
Research Assistant Dan Pugh from the University of Cardiff’s GTRC described work on the behaviour of pre-mixed CH4/H2 flames in a pressurised generic swirl burner for P2G applications. With the application of P2G in mind for utilising surplus renewable electricity, the aim of this work is to investigate the influence of hydrogen addition to CH4 in GTs and examine the comparative influences on flame stability, operability, dynamic pressure and emissions. As for the work presented earlier by Jon Runyon, a number of CH4/H2 mixtures (e.g. ‘FARH2’, ‘EMIX1’, etc.) were prepared and tested on the GTRC’s rigs under similar conditions to the work presented previously, with results on flame structure, etc. presented in a similar manner. Observations were made concerning the influence of swirl number and the acoustic response. Dan presented his conclusions and outlined ongoing work, which included the burning of H2/NH3 mixtures.
René Braun of B&B-AGEMA GmbH presented on the development of a DLN hydrogen combustion technology for GT application. The background for this work is the ‘Hydrogen Energy Supply Chain’ (HESC) concept in Japan (Australian brown coal gasified to produce CO2 (to CCS) and H2, which is liquefied, stored and shipped to Japan to be used in silicon chip and PV cell manufacturing, combined cycle power plants, in energy equipment and in transportation. The challenge is to control NOx emissions (i.e. high flammability makes pre-mixing not feasible, consequently high temperature produces higher NOx emissions. Work to identify alternative combustion technology to address this has led to two concepts: development of the Kawasaki DLN combustor (partial firing with hydrogen) – the pilot burner and main burner fired on natural gas, a supplemental burner on natural gas and increasing quantities of hydrogen as the load rises (overall, NOx <25ppm); and development of the Micromix Combustion technology, utilising multiple (~200) small flames within the combustor can – application to a real GT combustor has yielded ~18ppm NOx at 2bar and 34.4ppm at 10bar, with the objective to reach 25ppm.
Biogas and syngas:
Jörg Leicher of GWI described, on behalf of HVG, work looking into the utilisation of untreated biogas for glass melting. The glass industry is highly energy intensive but also has a requirement for very high product quality, with natural gas being the dominant fuel. In response to pressure to reduce GHG emissions, the industry has examined both efficiency measures (e.g. improved pre-heating, oxyfuel combustion, optimised process control, recycling, etc. – all subject to technological limits) and switching fuels to lower carbon alternatives. In this second category, partial or entire substitution with biogas is an attractive consideration, although the industry needs to know how combustion behaviour, heat transfer, refractory properties and glass quality are affected. Jörg presented a comparison table considering CV, relative density, the Wobbe Index of natural gas versus biogas, and also indicating that the gases have a very different composition and pollutant speciation. This work led on to the AiF Research Project that considered the fundamentals of combustion and emissions, and then cofired natural gas with raw biogas in a test furnace at GWI. The overall conclusions were that untreated biogas represents an interesting alternative with no negative impact on glass quality or refractory lifetime, with cofiring with natural gas being more feasible due to potential supply bottlenecks with biomass feedstock. However, current market conditions (i.e. very low ‘price’ on CO2 and NOx emissions) make cofiring uneconomic.
The Wobbe Index and/or GCV discussion resurfaced in a presentation by Mathieu Ourliac of ENGIE’s research and innovation centre in gas and new energie (CRIGEN) on dealing with gas quality variations in glass melting using biogas. In looking at France’s supplies of natural gas since the 1970s, Mathieu noted the shift from Lacq (France) to pipelined gas from Norway and Russia and LNG from Algeria, Tunisia, etc., with 6-8% variation in WI in a few hours not uncommon (e.g. up to 2MJ/m3 within an hour!). After considerable reflection, Mathieu was of the view that WI remains central to gas quality monitoring, and that thermal input will vary with WI. However, what is the impact on gas appliances and burners, and how do you deal with such variations in industrial processes? CRIGEN has considered both ‘closed loop’ and ‘open loop’ control in a boiler – the former may be too slow and measuring combustion products too difficult, but the latter, on the other hand, needs gas quality information (GCV, WI). They trialed continuous GCV/WI metering with integration into the burner control loop, with consequential efficiency improvements and considerable fuel savings. The changing world of gaseous fuel end-users has put a focus on biogas, producer gas, syngas and biomethane, with R&D into gasification, methanation and syngas of rising importance. The BioVine Project (uses wood residues from a vineyard to melt glass in wine bottle production) has conducted 500 hours of tests using a downdraft gasifier: Verralia (project lead) will communicate results in due course.
The final presentation was given by Professor Mohamed Porkashanian, Energy 2050, University of Sheffield (also General Secretary of IFRF) who provided a review of the fundamental research underlying the technical challenges in the use of syngas and biogas in power generation and industrial applications. The technical challenges for syngas and high-hydrogen-content (HHC) fuels are: effective combustion with fuel composition flexibility; meeting/beating environmental emission limits; and, as for all fossil fuels, syngas use produces a range of gaseous pollutants. Power generation from syngas via IGCC has been demonstrated, with emissions generation less than from CFB and PCFB plants (i.e. syngas is good in comparison with other fuels). Mohamed went on to examine, from a fundamental viewpoint, syngas and NOx, SOx, VOC and PAH, particulate, metal aerosols, CO and CO2 formation and emissions. He concluded that: syngas is a unique fuel in terms of pollutant formation; unlike natural gas, metals and halides are important; for power generation, emissions from syngas use are less than from direct coal use; for industrial uses of syngas, SOx, fly ash, NOx and metal aerosols emissions are similar; NOx, CO, VOC and PAH emissions are not related to composition but to the combustion system; and if natural gas is displaced by syngas, CO2 emissions go up due to the relative CVs. Possible future R&D areas were identified (including cryo-grinding of biomass) and two interesting were briefly examined (microGT with CCS firing syngas and biogas, and the BioCPV Integrated System for developing world situations).
In addition, four Posters were presented related to this session:
• ‘Leading the change towards eco-efficient furnaces’ (EC H2020 ‘VULCANO’ Project) – Jaroslaw Hercog of the Institute of Power Engineering (IET), Warsaw, described a novel furnace refurbishment solution including improved refractory materials, phase-change material-based energy recovery, cofiring with syngas, integrated monitoring and control, and a holistic in-house predictive tool. Demonstrations are being conducted in the steel and cement sectors, with replication potential in the aluminium manufacturing sector.
• ‘Replacing natural gas with syngas in the industrial furnace – CFD analysis’ (IET’s part of the VULCANO Project) – Piotr JóÅºwiak, IET, Warsaw presented that element of the VULKANO project being undertaken by IET, i.e. substitution of syngas for natural gas in the furnace. Piotr described the modelling activity in terms of the geometry, approach and goals. Four cases were examined: 1. Base case (no syngas); 2. Syngas premixed with natural gas in all burners; 3. Syngas fed through two existing burners; 4. Adding two extra syngas burners. The last proved best, with a best sub-case being with a low difference in Tmax.
• ‘PDF modelling of biogas flame of the Delft jet-in-hot-coflow burner including FGM tabulated chemical kinetics’ – Dirk Roeckaerts, Delft University of Technology presented work to mimic flameless combustion without the need for a furnace. The DJHC burner produces a turbulent diffusion flame from which Dirk had generated a coflow composition representation. He explained the construction of the flamelet generated manifold (FGM), before presenting his results and conclusions.
• ‘Flameless combustion in a lab-scale furnace: ignition and flame behaviour’ – Dirk Roeckaerts, Delft University of Technology described the objectives of this work, i.e. to study ignition and flame stabilisation behaviour of flameless combustion in a lab-scale furnace, and thereby obtain more insights of flameless combustion and the external range of operating conditions. He presented the experimental set-up, the characteristics of the combustion process and the ignition behaviour, before giving his conclusions.
IFRF would like to thank all the presenters at TOTeM 44 for the excellent quality of their presentations and which led to such in-depth discussions. A report will be prepared for all participants of the TOTem and for Members of IFRF.
Sincere thanks go to Jörg, Anne and Stephanie of GWI for organising and hosting such an interesting TOTeM.