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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]

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]

Cascade impactors, such as the Dekati electrical low pressure impactor (ELPI+), are useful measuring devices as they can classify particles per size range based on their inertial behaviour. However, various mechanisms, such as particle loss and particle bounce, make the measured particle size distribution to diverge from the real distribution. Moreover, some of these mechanisms depend on the amount of particles that have already been collected in an impactor stage and consequently the collection efficiency of a stage may be time-dependent. In this work, such mechanisms are investigated and their impact on the performed measurements is assessed. The use of greased and ungreased aluminium collection substrates and porous sintered impactor plates were extensively tested in the ELPI+. The aluminium substrates, regardless of the initial greasing, show an exponential decrease in total number concentration and an exponential increase in geometric mean particle diameter with increasing particle load on the substrates. This is the result of an exponential concentration decrease of the stages that collect particles smaller than the accumulation peak and a concentration increase of the stages that collect larger particles. The effect is attributed to the decrease in particle bounce with increasing particle loading. On the other hand, the sintered impactor plates show barely any time-dependent collection behaviour. [Display omitted] • The particle size distribution obtained with ELPI+ depends on the collection surface. • Total number concentration reduces exponentially over time with aluminium substrates. • Geometric mean diameter increases exponentially over time with aluminium substrates. • Greasing no longer improves collection behaviour after high particle loading. • Sintered impactor plates show barely any time-dependent collection behaviour. [ABSTRACT FROM AUTHOR]

Increasing the share of Renewable energy sources in District Heating (DH) systems is of great importance to mitigate their CO2 emissions. The combined integration of Solar Thermal Collectors (STC) and Thermal Energy Storage (TES) into existing Combined Heat and Power (CHP) systems can be a very cost-effective way to do so. This paper aims at finding the optimal design of STC and TES systems integrated in existing CHP's considering two distinct objectives: economic profitability and environmental impact. To do so, we developed a three-stage framework based on Pareto-optimal solutions generated by multi-objective optimization, a Technique for Order Preference by Similarity to Ideal Solution (TOPSIS)-entropy method to select the optimal solution, followed by the definition of final Operation strategy. We proposed relevant improvement of the state-of-the-art models used in similar analysis. We also applied the proposed methodology to the case of a representative, 12 MWth CHP plant. Our results show that, while the addition of TES or STC alone results in limited performances and/or higher costs, both the cost and the CO2 emissions can be reduced by integrating the optimal combination of STC and TES. For the selected, optimal solution, carbon emissions are reduced by 10%, while the Annual Total Cost (ATC) is reduced by 3%. It also improves the operational flexibility and the efficiency by peak load shaving, load valley filling and thus by decreasing the peak load boiler operation. Compared to the addition of STC alone, the use of TES results in an increased efficiency, from 88% to 92%. The optimal share of STC is then increased from 7% to 10%. [ABSTRACT FROM AUTHOR]

Abstract: Let be a continuous, 2-dimensional and absolutely irreducible mod p representation of the absolute Galois group of a number field . In this work, we study the existence of lifts of to , for which the restrictions to the decomposition groups above p are abelian. The tools and philosophy come from the Taylor–Ramakrishna method. As an application we produce finitely ramified extensions over with Galois group , for some p. These extensions are unramified at p. [Copyright &y& Elsevier]

A scientific mathematical law is causal if and only if it is a process law that contains a time derivative. This is the intrinsic criterion for causal laws we propose. A process is a space-time line along which some properties are conserved or vary. A process law contains a time variable, but only process laws that contain a time derivative are causal laws. An effect is identified with what corresponds to a time derivative of some property or magnitude in a process law, whereas the other terms correspond to the cause(s). According to our criterion, causes are simultaneous with their effects and causality has no temporal direction. Several examples from natural and social disciplines support the applicability of our criterion to all scientific laws. Various objections to our proposal are presented and refuted. The merits our intrinsic theory of causality vis-à-vis the Salmon–Dowe conserved quantity theory are discussed. [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]

The Energy Return On Investment (EROI) is a recognised indicator for assessing the relevance of an energy project in terms of net energy delivered to society. For woody biomass divergences remain on the right methodology to assess the EROI leading to large variations in the published estimates. This article presents an in‐depth discussion about the EROI of woody biomass in three different forms: woodchips, pellets and liquid fuels. The conceptualisation of EROI is further developed to reach a consistent definition for biomass post‐processed fuels. It considers, on top of the external energy investments, the grey energy associated with the energy used to enrich the fuel. With the proposed methodology, all woodchips have an EROI of the same order of magnitude, between 20 and 37, depending on forestry types, operations and machineries. For secondary residues, the first estimate is 170 if, as co‐products, no energy investment is allocated to the forestry operations and transport. On the basis of a mass allocation for forestry operations and transport, the EROI for secondary residues becomes of the same order of magnitude as that for wood chips. Woodchips can be further post‐processed into pellets or liquid fuels. Pellets have an EROI of 4–7 if the heat is externally supplied and 8–23 if internally supplied (self‐consumption of part of the raw material). Liquid fuels derived from primary wood and residues through gasification and Fischer‐Tropsch synthesis have an EROI between 4 and 16. Fuel enhancement with hydrogen (Power & Biomass to Liquids) impacts negatively the EROI due to the low EROI of hydrogen produced from renewable electricity. However, these fuels offer other advantages such as improved carbon efficiency. A correct estimate of EROI for forestry biomass, as proposed in this work, is a necessary dimension in assessing the suitability of a project. [ABSTRACT FROM AUTHOR]

Despite their obvious benefit in terms of energy efficiency and their potential benefit on pollutant emissions, Flue Gas Condensers (FGCs) are still not widely spread in biomass combustion plants. Although their costs have significantly decreased during the last decade, the economic viability of FGC retrofits is not straightforward and their return on investments is mainly dependent on the temperature of the available heat sink and the moisture content of the fuel. Based on a new techno-economic model of a FGC validated with recent industrial data, this paper presents a methodology to assess the economic viability of an FGC retrofitting in a medium-scale biomass combustion plant. The proposed methodology is applied to the case of a typical District Heating plant for which real data was collected. For the first time, the usual assumptions of constant process data generally used are challenged by considering the variability of the return temperature and heat demand over the year. Furthermore, a new concept of optimal configurations in terms of energy savings is introduced in this paper and compared to a strictly economic optimum. The economic feasibility is mainly evaluated by means of the Net Present Value (NPV), Discounted Payback Period (DPP), and the Modified Internal Rate of Return (MIRR). As expected, results show that the higher the humidity level and the lower the return temperature, the higher the economic profitability of a project. The NPV is, however, increased when considering variable inputs: Even with an average return temperature of 60 °C, a mixed operation of the FGC as a condenser and an economizer along the year is predicted, which results in an increased profitability assessment. Considering a constant return temperature over the year can lead to a 20% underestimation of the project NPV. An alternative averaging method is proposed, where two distinct temperature zones are considered: above and below the flue gas dew point. The discrepancy with a detailed temperature variation is reduced to a few percents. Our results also show that increasing the FGC surface beyond the highest NPV can lead to substantial energy savings at a reasonable cost, up to a certain level. The energetic optimum we defined can lead to an increase in energy savings by 17% for the same relative decrease of the NPV. [ABSTRACT FROM AUTHOR]

Accurately measuring particulate matter emissions from biomass combustion is crucial for evaluating the performance of fuels, combustion appliances and flue gas cleaning methods. These measurements are essential for refining emission inventories for health risk assessments and environmental models and for defining pollution control strategies. However, as air quality standards become increasingly stringent and emission levels decrease, it is important to develop reliable, accurate measurement methods. This study presents a comprehensive evaluation of two particulate dilution systems, namely a full flow dilution (FFD) tunnel and a two-stage partial flow dilution system (porous tube diluter combined with ejector diluter, PTD + ED), for characterising the particle number size distribution from a wood pellet boiler. The maximum relative sampling errors due to not sampling isokinetically increase with particle size and dilution ratio (DR), but are less than 1% for particles smaller than 1 μm for both systems. The total particle number concentration with FFD is on average 35% lower than with PTD + ED, which suggests substantial particle loss during FFD. In addition with FFD, a strong negative correlation is observed between DR and the average particle size. On the other hand with PTD + ED, both the dilution air temperature and DR have no substantial influence on the particle number emissions. However, it is observed with both systems that the particle distribution is affected by coagulation, and this effect becomes more pronounced as dilution decreases. Overall, this work provides insights into the strengths and limitations of particulate dilution systems for accurately measuring emissions from biomass combustion, which can support the development of more reliable measurement methods and assist in implementing effective pollution control strategies. • Dilution temperature with partial flow dilution does not affect particulate matter. • Particle number concentration is 35% lower with full flow dilution. • Decreasing the dilution ratio with full flow dilution yields larger particles. • Coagulation has a larger impact on particulate measurements when dilution decreases. • Errors due to anisokinetic sampling increase with increasing dilution. [ABSTRACT FROM AUTHOR]

The growing share of renewable energies in our electricity production, together with the still lacking storage capacity, strongly reinforces the need for more flexible electricity production units. In this context, combined cycle gas turbines (CCGTs) have a role to play, both in the current and future electricity production system due to their high efficiency, high load flexibility, and low CO2 emissions compared to other conventional thermal power plants. Nevertheless, bearing in mind our current challenges concerning climate change, the CO2 emissions of these CCGTs need to be reduced drastically. The amine-based absorption carbon capture (CC) process is currently the most mature and applicable CC technology. This process is known to require a considerable amount of thermal energy, degrading plant performance. However, to back-up renewable production, CCGTs will operate most of the time under part-load conditions. The impact of these part-load operations on the CC is still relatively unknown. Within this framework, this study aims to assess the performance of the CC process applied to a typical CCGT under part-load operation using specific simulation models. The CC plant model has been successfully validated against experimental data from a pilot-scale capture facility. Then, the CC plant has been scaled-up to the CCGT scale and the process has been optimized for each operating condition. The simulation results show that the specific reboiler duty increases for part-load operation, while the specific cooling requirements decrease. Moreover, the analysis of the yearly CCGT operation highlights a relative increase in CC energy penalty of 21% for an annual CCGT load factor of 0.5, impacting significantly plant performance. The next step will involve reducing this energy penalty. [ABSTRACT FROM AUTHOR]

Energy crops on marginal lands are seen as an interesting option to increase biomass contribution to the primary energy mix. However, in the literature there is currently a lack of integrated assessments of margin land availability, energy crop production potential and supply chain optimisation. Assessing the potential and the cost of these resources in a given region is therefore a difficult task. This work also emphasises the importance on a clear definition and discussion about marginal lands and the related ethical issues embedded in the concept to ensure positive societal impacts of the results. This study proposes a methodology to estimate and analyse, in terms of economic costs, the potential of miscanthus grown on marginal lands from the production to the final point of use. Different datasets are assembled and a supply chain optimisation model is developed to minimize the total cost of the system. Miscanthus is used as a representative energy crop for the Belgian and French case studies. High temperature heat demand is considered as final use. The miscanthus can be traded by truck either in the form of chips or pellets. The results show that the miscanthus on marginal lands could supply high temperature heat up to 38 TWh in France and 1.4 TWh in Belgium with an average cost of around 50 €/t. The different sensitivity analyses showed that the yield variation has the strongest influence on the final cost, together with the distances and the cost of production of miscanthus. The main pattern observed is the local consumption of miscanthus chips and export of the surplus (if any) to the neighbouring regions. Pellets are only of marginal interest for France and are never observed for Belgium. Distances and availability of sufficient feedstocks are the two main parameters impacting the production of pellets. [ABSTRACT FROM AUTHOR]

Predicting the demisability upon re-entry of space debris objects is of great importance due to the threat these objects pose if they were to fall in an inhabited area. In particular, carbon/epoxy composite materials have been found on Earth in several occasions. Accurate models to assess the demisability of such components require, in particular, detailed thermal degradation data for the epoxy resin. In this work, we analyze a resin used to manufacture such components, using thermogravimetric analysis (TGA), organic elemental analysis, and pyrolysis coupled to comprehensive two-dimensional gas chromatography. The epoxy resin rapidly decomposed in a relatively narrow range of temperatures (300–400∘C) in more than 70 different volatile products. A one-step kinetic model is proposed for the pyrolysis of epoxy based on thermogravimetry observations. The information on the species and elemental composition can be used to develop more accurate material degradation models for predicting the demisability upon re-entry of space debris. • Studied thermal decomposition of epoxy resin using different techniques. • Developed single step kinetics model based on TGA data. • Quantified 70 different products of pyrolysis of epoxy resin. [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]

Three portable dilution devices (a two-stage dilutor, a one-stage dilutor and an axial dilutor) and a stationary dilution tunnel were compared by employing them in an experimental setup for particle emission measurements from a 40 kW pellet boiler. Total concentrations and number size distributions of particles were detected by an ELPI + analyzer. Averaged values of total particle emission per MJ received from measurements with available dilution devices were within the range between 3.14 × 1013 and 1.15 × 1014 for the full power regime, and between 1.54 × 1013 and 5.03 × 1013 for the reduced power regime. Measured particle concentrations decreased by using dilution devices in the following order: a two-stage dilutor, a one-stage dilutor, a dilution tunnel and an axial dilutor. The number size distributions of particles for the majority of cases are qualitatively similar for all devices for similar combustion regimes of the boiler. Applying dilution air with or without heating did not significantly affect the results of measurements. During multiple series of measurements the degree of dilution was varied when possible for different devices within a range between 8 and 102. No dependence of particle concentrations on the degree of dilution could be determined from these experiments. Applying a method of one-way analysis of variance revealed the statistically significant difference in particle concentrations measured with different dilution devices. Implementing this method to CO, and CO2 gas emission components of different series it was determined that the boiler operation was stable as the measured data belong to the same distribution. Thus, the statistical differences in particle concentrations most likely relate to the varied measuring equipment, i.e., dilution devices. Copyright © 2021 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Electrostatic precipitators (ESP) are an effective means of reducing particulate matter emissions from biomass combustion. This study presents a comprehensive evaluation of the performance of an ESP integrated in a 240 kW wood chip boiler. The boiler-integrated ESP is commercially available and is evaluated in-situ using two types of wood chips, unlike previous studies, which mainly focuses on prototypes or lab-based constructions. The obtained results indicate a mass-based ESP efficiency of 94%–96%, surpassing previously reported values for small-scale boiler-integrated ESPs. Furthermore, the number-based ESP efficiency is 83%–92%, which is in line with values reported in literature. Despite the promising performance, the widespread adoption of integrated ESPs in small-scale appliances faces challenges due to the lack of financial, regulatory and energetic incentives. Nevertheless, the application of ESPs in this context remains crucial in addressing local air pollution and reducing the overall environmental impact of small-scale biomass combustion. To facilitate broader implementation, further research and policy initiatives are necessary. This study provides valuable insights into the true effectiveness of a small-scale ESP in mitigating particulate matter emissions. • Study of commercially available ESP in real-world use. • Particle mass-based ESP collection efficiency is 94–96%. • Particle number-based ESP collection efficiency is 83–92%. • ESP effectively reduces particulate emissions from small-scale biomass combustion. • Lack of financial, regulatory and energetic incentives to invest in small-scale ESP. [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]

• Developed first pyrolysis model for PICA at high heating rate. • Devolatilization models calibrated by coupling material solver and genetic optimizer. • New pyrolysis models reproduce experimental data at flight-like heating rate. • Model captures both material thermal decomposition and pyrolysis gas production. A novel model for the pyrolysis of the Phenolic Impregnated Carbon Ablator (PICA) at high heating rate is developed and calibrated based on high fidelity thermal decomposition experiments. The calibration relies on accurate quantification of pyrolysis gases obtained from mass spectroscopy analysis during thermal decomposition at fast heating rates simulating flight conditions. Model calibration is achieved by coupling the Porous material Analysis Toolbox based on OpenFOAM (PATO) with an optimization software (Dakota). A multi-objective genetic algorithm is used to fit the experimental data by optimizing the model parameters for an element and a species-based formulation. The new model captures both the material mass loss and the gaseous species produced during pyrolysis. [ABSTRACT FROM AUTHOR]