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To attain a net zero-carbon emissions energy system, the grid needs dispatchable and flexible power production capable of responding to wind and solar energy variability. Hydrogen-fired gas turbines could play a role in meeting this requirement in the electricity grid; however, research and development are needed to assess the impact of the fuel change on these systems. This study aims to determine the effect of fuel switching on the cycle performance of a typical aero-derivative gas turbine, ranging from 25-35MW when combined with various steam-based bottoming cycles using Aspen Plus thermodynamic simulations. The gas turbine cycle's efficiency and net output power increased by about 2.26% and 5.24%, respectively, when fueled with hydrogen for the constant TIT control strategy compared with the base case. The other two control strategies—constant TOT and heat input—are also positive. The performance of the combined heat and power configurations, expressed by the fuel charged to power, is better for almost all the hydrogen-fired cases compared with the methane case. This implies that using hydrogen as fuel in the gas turbine and duct-firing requires less fuel to produce heat and electricity. Although hydrogen integration into the overall system may pose challenges with auxiliary equipment, storage, supply, and combustion, hydrogen as fuel shows promise in improving the performance of gas turbine combined heat and power units. • Hydrogen for GTs will be an enabler of low-carbon and flexible power production. • Switching to hydrogen enhances power and heat production in all operating strategies. • The GT performance improves with the hydrogen fraction for all operating strategies. • Hydrogen firing increases the operational flexibility of GT-based CHP configurations. [ABSTRACT FROM AUTHOR]

Ammonia is currently investigated as a sustainable energy source. Its mixture with hydrogen may present combustion characteristics that are similar to those of hydrocarbon, which motivates its use in gas turbines burners. Such similarities were discussed at atmospheric pressure in previous works for a fuel blend with a molar fraction of hydrogen X H 2 Fuel = 0.46 , which is further studied here. The influences of pressure and wall heat loss on ammonia/hydrogen/air flames are for the first time investigated via large eddy simulation. A first campaign is led at both 1 and 5 atm, to estimate the effect of pressure. It demonstrates that NO emissions are favoured by flame interactions with a hot wall, along which NO is convected. Accordingly, the flame length reduction observed at high pressure, due to higher heat release rates, leads to a more efficient NO consumption. Increasing the pressure shifts the equivalence ratio for optimal NH 3 and NO X emissions towards the lean side. It results in lower hydrogen emissions and therefore an increase of the combustion efficiency. Finally, the NH 3 and NO X emissions at optimal equivalence ratio are reduced from 450 ppmv for φ = 1.27 at 1 atm, to ∼ 100 ppmv for φ = 1.20 at 5 atm. A second campaign is led at both 1 and 5 atm, by varying the burner wall thermal boundary conditions. Lean combustion with cold walls presents high N 2 O emissions of 607 ppmv while in rich cases, the higher gas temperatures and the excess of H radicals in the burned gases yield complete N 2 O consumption. It is shown that heat loss effect on N 2 O fractions distribution is reduced at high pressure due to weaker flame interaction with the cold walls. Finally, thermal boundary conditions are found to significantly affect NO X , N 2 O and NH 3 emissions, showing that heat losses should be considered when modelling such configuration. • Effects of pressure and heat loss on NH 3 /H 2 combustion were explored with LES. • Passing from 1 to 5 atm lowers NOx and NH 3 emissions of rich mixture by a factor 5. • Low temperature of burner wall is favourable to NO consumption. • N 2 O emissions are correlated to H radicals and wall temperature. • Heat losses to the wall affect significantly NOx, N 2 O and NH 3 emissions. [ABSTRACT FROM AUTHOR]

Residential building heating stands as a significant energy consumer with substantial environmental implications. To facilitate a sustainable transition, it is essential to assess the emissions and costs associated with current heating practices. This study investigates the economical and environmental aspects of residential building heating in the Brussels-Capital Region (BCR), Belgium. Employing a bottom-up methodology that integrates Energy Performance of Buildings (EPB) certificates with specific emissions and cost data, the analysis evaluates the emissions (including direct and indirect greenhouse gases (GHG), NO x , SO 2 and PM 2.5) and the levelized cost of heat (LCOH) of the existing array of heating appliances in the BCR. The analysis reveals notable variations in emissions intensity and LCOH across diverse heating technologies, highlighting the intricate interplay between environmental sustainability and economic viability. Wood and electric-powered appliances demonstrate relatively low GHG emissions compared to fossil fuel appliances. Nonetheless, individual wood-fueled appliances exhibit elevated NO x and PM 2.5 emissions compared to the current weighted average emissions intensity of the BCR. Furthermore, sensitivity analysis underscores the substantial influence of fuel price scenario on the most cost-effective heating technology. This study provides a balanced framework for informed decision-making on residential building heating, offering benchmarks for transitioning to a more sustainable urban heating infrastructure. • Analysis of residential building heating appliances in Brussels-Capital Region. • Research based on Energy Performance of Buildings certificates. • Insights into cost-emission trade-offs for individual building heating appliances. [ABSTRACT FROM AUTHOR]

Hydrogen, with its unique flammability characteristics, demands additional consideration due to its broader flammable range compared to fossil fuels. Its low density at atmospheric conditions results in significant buoyancy, mitigating risks in outdoor applications. In confined spaces, hydrogen releases can lead to flammable cloud formation. To study this problem, independent of its dimensions, a dimensional analysis is introduced based on Buckingham's Π -theorem. This work focuses on thirteen functional parameters, including mole fraction, time, release velocity, orifice diameter, reduced gravity, molecular mass diffusion, viscosity and geometric dimensions. Four dimensional scenarios are simulated and compared in this study, to assess the adequacy of the proposed non-dimensional approach. The setup involves a parallelepiped enclosure with a single release point. RANS simulations are conducted. The proposed non-dimensional formulation proves valuable for interpreting data and discussing practical applications. The study contributes to a deeper understanding of hydrogen filling regimes in confined spaces, offering insights for safety assessments and risk mitigation strategies. [Display omitted] • Functional parameters for hydrogen distribution are proposed. • Application of Buckingham's Π -theorem yields essential non-dimensional ratios. • RANS CFD-model used to simulate and discuss four similar scenarios. • Time series analysis of non-dimensional flammable volume reveals similarity. • Ratios and non-dimensional flammable volume enable dimension-independent safety analysis. [ABSTRACT FROM AUTHOR]

Micro Gas Turbines (mGT) appear as a promising technology for small-scale (up to 500 kW) Combined Heat and Power (CHP) production. However, their rather low electric efficiency limits their profitability when the heat demand decreases. Hot liquid water injection in mGTs –particularly within the micro Humid Air Turbine (mHAT) cycle– allows increasing electric efficiency by making use of the flue gas residual heat in moments of low heat demand. Based on simulations performed on a Turbec T100 mGT –modified to operate as an mHAT– installed at the VUB, this paper presents an analysis of the economic profitability of such facility running on real network conditions. The study is performed assuming typical electricity and heat demand profiles for a domestic consumer. 25 natural gas and electricity price combinations have been taken into consideration, along with two types of domestic customers –with higher and lower heat demands. Results show that the profitability of the mHAT with respect to the equivalent CHP facility increases with higher electricity and lower natural gas prices. In particular, given a certain number of CHP running hours and a natural gas price, there is a threshold for the electricity price above which the net income of the mHAT unit is always higher than that of the corresponding CHP unit. In addition, water-cleaning costs for the mHAT case appear to constitute only 1 to 2.5% of total running costs. [ABSTRACT FROM AUTHOR]

Abstract: Numerous industrial applications dedicated to the conversion of biomass into heat and power include a pyrolysis step conducted under severe thermal conditions (heating rates of 103…105 K s−1 and maximum temperatures higher than 1000 K). While pyrolysis might not be the central phenomenon of the considered processes, it is often an essential input for the other steps to be modelled, for instance the successive oxidation of the pyrolysis volatiles in combustion applications. Two competitive, multi-component pyrolysis mechanisms have been compared to low (1 K s−1) and high (103 K s−1) heating rate experimental results. One of them features a characterization of the emitted gaseous species. It was found that both mechanisms reasonably agree with measurements at low heating rate, and that they diverge at higher heating rates, none of them being able to reasonably fit the experimental data. The observed discrepancies have been studied and modifications have been proposed for the most comprehensive mechanism. The resulting scheme has been combined with a two-dimensional physical model of a single particle that is necessary for problems that cannot be considered as thermally thin. The resulting model is a powerful predicting tool for the emitted species yields from a pyrolysing particle, even in high temperature applications. [Copyright &y& Elsevier]

Abstract: Biomass combustion in pulverized-fuel boilers is a growing way to produce electricity from a renewable source of energy. Slagging and fouling limit however the reliability of the units that were initially designed for coal combustion. Computational Fluid Dynamics (CFD) codes aiming at studying those phenomena include simplified models of biomass particle pyrolysis, of which the pertinence has already been questioned for the typical conditions of interest. A comprehensive model has been developed to investigate pyrolysis of particles in pulverized-fuel boilers, with sizes ranging from 17μm to 2.5mm. The detailed model accounts for internal heat conduction, internal gaseous convection, moisture evaporation and particle shrinkage. It includes a competitive, multi-component kinetic scheme, improved for high temperatures. The discrepancy between the simplified models integrated in most CFD applications and the detailed simulations is highlighted. The simplified isothermal models underestimate pyrolysis time for the largest particles. Moreover, such models delay and shorten the volatiles release. The flame lengths, the local temperature fields and the pollutant emissions might be importantly impacted in global combustion simulations. Apparent kinetic parameters have been derived from the detailed simulations. Their use in existing simplified models improves the behavior of the biomass particles during pyrolysis, and offers therefore an efficient alternative to the integration of complex pyrolysis models in CFD codes. [ABSTRACT FROM AUTHOR]

Ammonia and hydrogen are promoted as potential energy carriers for centralized energy restitution. This article investigates ammonia/hydrogen/air premixed turbulent combustion, using Large-Eddy Simulations, in an academic atmospheric gas turbine swirled burner. A one-dimensional flame analysis demonstrates the existence of a trade-off in NO X and NH 3 emissions for ammonia/hydrogen blends, and the possibility to obtain 1D flame propagation characteristics close to that of a lean methane flame by adjusting the amount of H 2. Large-Eddy Simulations of the PRECCINSTA burner exhibit stable combustion, while the optimized trade-off equivalence ratio is pinpointed at φ = 1.46 for X H 2 Fuel = 0.46. Corresponding emissions are X N O X ≈ X N H 3 ≈ 300 ppmv. Large amounts of hydrogen are found in the exhaust gases, inducing a low combustion efficiency. The flame structure, combustion dynamics, influence of kinetics modelling and mesh resolution are discussed. This work paves the way for future studies, in the perspective of applications to industrial systems. • Combustion characteristics of NH 3 /H 2 blends were explored from 1D simulations. • NO X /NH 3 emissions trade-off is found for a precise equivalence ratio in rich blends. • The equivalence ratio at emissions trade-off increases with hydrogen addition. • 3D LES yields NO X /NH 3 emissions of ∼300 ppmv for φ = 1.46 and X H 2 Fuel = 0.46. [ABSTRACT FROM AUTHOR]

• Overview on regulations regarding bottom ash utilisation in 22 European countries. • Diverse regulation of bottom ash utilisation in the EU. • Utilisation rates vary between 0% and 100% between investigated countries. • Critical discussion of limit values and comparison between countries. • Proposal of key-points for a uniform legislation at EU level. Almost 500 municipal solid waste incineration plants in the EU, Norway and Switzerland generate about 17.6 Mt/a of incinerator bottom ash (IBA). IBA contains minerals and metals. Metals are mostly separated and sold to the scrap market and minerals are either disposed of in landfills or utilised in the construction sector. Since there is no uniform regulation for IBA utilisation at EU level, countries developed own rules with varying requirements for utilisation. As a result from a cooperation network between European experts an up-to-date overview of documents regulating IBA utilisation is presented. Furthermore, this work highlights the different requirements that have to be considered. Overall, 51 different parameters for the total content and 36 different parameters for the emission by leaching are defined. An analysis of the defined parameter reveals that leaching parameters are significantly more to be considered compared to total content parameters. In order to assess the leaching behaviour nine different leaching tests, including batch tests, up-flow percolation tests and one diffusion test (monolithic materials) are in place. A further discussion of leaching parameters showed that certain countries took over limit values initially defined for landfills for inert waste and adopted them for IBA utilisation. The overall utilisation rate of IBA in construction works is approximately 54 wt%. It is revealed that the rate of utilisation does not necessarily depend on how well regulated IBA utilisation is, but rather seems to be a result of political commitment for IBA recycling and economically interesting circumstances. [ABSTRACT FROM AUTHOR]

Thermal Protection Materials (TPM) such as carbon/phenolic composites are used to protect spacecraft structures from extreme conditions. This protection is, in part, achieved by the decomposition via pyrolysis of the phenolic resin. Finite rate chemistry models are however still unable to predict the chemical production rates and composition of the pyrolysis products accurately. This is mostly due to the scarcity of experimental data for model validation. In this work, the decomposition of a phenolic material representative of thermal protection material is studied in a unique micro-pyrolysis unit for the temperature range 300-800 °C. This unit is equipped with highly sensitive detectors allowing us to identify and quantify products in a broad range of molecular weights up to 240 g mol−1. More than 50 different products of the pyrolysis of phenolic resin have been quantified with a mass balance closure greater than 80%. The major compound groups found are permanent gases, phenols as well as larger molecules such as diphenols and naphthalenes. In addition, the char yield obtained at the fast heating rates employed in our apparatus was found ∼ 5 % -points lower compared to traditional thermogravimetry. [ABSTRACT FROM AUTHOR]

Flue Gas Condensers (FGC) are used to increase the thermal output of biomass boilers. This reduces the emissions per unit of produced energy but furthermore, fine dust particles will be collected in the condenser. These condensers therefore have a double effect on the specific particulate matter emissions. In addition to the mechanisms that cause particle capture such as thermophoresis and diffusiophoresis, other agglomeration or condensation growth mechanisms also influence the size of the emitted particles. Due to the combination of these mechanisms, the capture efficiency depends on particle size. A size range presenting a lower capture efficiency, called a penetration window, is generally observed. Measurements on a 5 MW th boiler showed that this penetration window is in size range 0.07–0.49 μm where the capture efficiency is reduced by around 20%. Measurements on an 18 kW th boiler showed that the penetration window is in the size range 0.04–0.49 μm and the capture efficiency can even be negative in this window. For the medium-scale boiler, the condenser reduces the overall particulate emissions by 64% in number and 62% in mass per m3, and 70% in number and 69% in mass per MJ. For the small-scale boiler, the condenser reduces the overall particulate emissions by 4% in number and 50% in mass per m3, and 14% in number and 55% in mass per MJ. • FGC particle collection efficiency has a penetration window with reduced efficiency. • Overall FGC particle collection efficiency is positive in both mass and number. • Minimum FGC collection efficiency occurs at peak of accumulation mode. • Maximum baghouse collection efficiency occurs at peak of accumulation mode. [ABSTRACT FROM AUTHOR]

Simulations of atmospheric entry of spacecraft and satellites require accurate knowledge of thermo-physical properties such as heat capacity in a wide temperature range. However, the characterization of this quantity is not straightforward for carbon composites at high temperatures, due to pyrolysis reactions that occur in the material. We develop a methodology for determining the heat capacity and required heat of pyrolysis for carbon composites in these conditions. The methodology consists of three steps: organic elemental analysis to determine composition, differential scanning calorimetry experiments on the different components to determine apparent heat capacity, and computations to separate the apparent heat capacity into heat capacity and heat of pyrolysis. This methodology is applied to the Zuram ® carbon/phenolic ablator from room temperature up to 1100 K. The results obtained were compared to separate analyzes of the different components of the material, assuming that heat capacity is an additive property. It was found that compressing the samples into disks provides improved resolution and repeatability for low density materials. This provided a determination of the heat capacity of the decomposing composite with a relative standard deviation < 10 % and of < 20 % for the heat of pyrolysis. The proposed methodology can directly be applied to other carbon composites such as carbon/epoxy systems. [ABSTRACT FROM AUTHOR]

Carbon/phenolic ablators are successfully used as thermal protection material for spacecraft. Nevertheless, their complex thermal degradation is not yet fully understood, and current pyrolysis models do not reproduce important features of available experimental results. Accurate and robust thermal degradation models are required to optimize design margin policy. We investigate whether the competitive kinetic schemes commonly used to model biomass pyrolysis are appropriate to describe the thermal degradation of carbon/phenolic composites. In this paper, we apply competitive pyrolysis mechanisms for the thermal degradation of the carbon/phenolic ablator PICA. Model parameters are then calibrated using a robust two-step methodology: first deterministic optimization is used to obtain the best estimation of the calibration parameters based on the experimental data, then a stochastic Bayesian inference is performed to explore plausible set of solutions taking into account the experimental uncertainties. The proposed calibrated model provides an accurate description of the pyrolysis process at different heating rates. The model shows great flexibility and robustness at a similar computational cost as the traditional devolatilization models. This opens the possibility for more complex mechanisms when more experimental data becomes available. [ABSTRACT FROM AUTHOR]