41 research outputs found
Lamp-post with an outflow and the hard state of Cyg X-1
Relativistic reflection observed in the hard states of accreting black holes
often shows a weak amplitude relative to the main Comptonization component,
which may result from either a disc truncation or a non-isotropy of the X-ray
source, e.g. due to a motion away from the reflector. We investigate here the
latter case, assuming that the X-ray source is located on the symmetry axis of
the Kerr black hole. We discuss effects relevant to a proper computation of the
reflected radiation and we implement them in the model for data analysis,
reflkerrV. We apply it to the simultaneous Suzaku and NuSTAR observation of Cyg
X-1 in the hard state and we find a good fit for an untruncated disc irradiated
by the source moving away from it at 0.36c. However, we find a slightly better
solution in a geometry closely approximating the truncated disc irradiated by
an inner hot flow. In this solution we either still need a subrelativistic
outflow or the source opposite to the observer must contribute to the directly
observed radiation. We also discuss differences between the implementation of
the outflow effect in reflkerrV and in relxilllpCp.Comment: MNRAS, in pres
Torrefaction and gasification of biomass for polygeneration: Production of biochar and producer gas at low load conditions
In this paper, a matter of biomass torrefaction and gasification is closely looked at from different points of view during low load and low equivalence ratio regime, defined as lambda = 0.08. Considering gas production, the hot gas efficiency of conversion (30%) and its energy content (4.14 MJ m(-3)) were not quite satisfying, however, this matter of fact was compensated by an interesting yield of biochar. This material was generated in 0.387 and 0.314 rates for torrefaction and torrefaction + gasification processes, respectively, which, in both cases, represents an attractive, alternative approach to the functional energy storage. It was determined that a CO2 offset of 721 kg and 660 kg could be achieved per 1 tonne of woodchips for gasification of raw woodchips and a 2-stage process with torrefaction and gasification, respectively. The measured data from both technological complexes were compared with the computational model, applying equilibrium reactions for gas components determination. In addition, the question of tar compounds contained within the producer gas, is investigated through GC-MS analysis on both qualitative and quantitative basis.Web of Science814413
Combustion and explosion characteristics of pulverised wood, valorized with mild pyrolysis in pilot scale installation, using the modified ISO 1 m(3) dust explosion vessel
Featured Application Design of explosion safety measures for torrefaction installations and design of pulverized-fired burners for biocoal. Biomass is a renewable energy source with great potential worldwide and in the European Union. However, valorization is necessary to turn many types of waste biomass into a tradable commodity that has the potential to replace coal in power plants without significant modifications to firing systems. Mild pyrolysis, also known as torrefaction, is a thermal valorization process of low-quality biomass that could be suitable for such a purpose. In this work, typical Spruce-Pine-Fir residues from a sawmill were tested in terms of the explosion and flame propagation properties. The ISO 1 m(3) dust explosion vessel was used, with a modified and calibrated dust dispersion system that could cope with very coarse particles. The deflagration index, K-st, was higher for the torrefied sample, with a peak at 36 bar m/s compared with 27 for the raw biomass. The peak flame speeds were similar for both samples, reaching 1 m/s. The peak P-max/P-i was between 7.3 and 7.4 bar for both untreated and torrefied biomass. The mechanism for coarse particle combustion is considered to be influenced by the explosion-induced wind blowing the finer fractions ahead of the flame, which burns first, subsequently devolatilizing the coarser fractions.Web of Science1224art. no. 1292
Integrating life cycle assessment and machine learning to enhance black soldier fly larvae-based composting of kitchen waste
Around 40% to 60% of municipal solid waste originates from kitchens, offering a valuable
resource for compost production. Traditional composting methods such as windrow, vermi-, and
bin composting are space-intensive and time-consuming. Black soldier fly larvae (BSFL) present a
promising alternative, requiring less space and offering ease of handling. This research encompasses
experimental data collection, life cycle assessment, and machine learning, and employs the Levenberg–
Marquardt algorithm in an Artificial Neural Network, to optimize kitchen waste treatment using
BSFL. Factors such as time, larval population, aeration frequency, waste composition, and container
surface area were considered. Results showed that BSFL achieved significant waste reduction, ranging
from 70% to 93% by weight and 65% to 85% by volume under optimal conditions. Key findings
included a 15-day treatment duration, four times per day aeration frequency, 600 larvae per kilogram
of waste, layering during feeding, and kitchen waste as the preferred feed. The larvae exhibited a
weight gain of 2.2% to 6.5% during composting. Comparing the quality of BSFL compost to that
obtained with conventional methods revealed its superiority in terms of waste reduction (50% to 73%
more) and compost quality. Life cycle assessment confirmed the sustainability advantages of BSFL.
Machine learning achieved high accuracy of prediction reaching 99.5%.Web of Science1516art. no. 1247
Advancing sustainable decomposition of biomass tar model compound: Machine learning, kinetic modeling, and experimental investigation in a non-thermal plasma dielectric barrier discharge reactor
This study examines the sustainable decomposition reactions of benzene using non-thermal
plasma (NTP) in a dielectric barrier discharge (DBD) reactor. The aim is to investigate the factors
influencing benzene decomposition process, including input power, concentration, and residence
time, through kinetic modeling, reactor performance assessment, and machine learning techniques.
To further enhance the understanding and modeling of the decomposition process, the researchers
determine the apparent decomposition rate constant, which is incorporated into a kinetic model
using a novel theoretical plug flow reactor analogy model. The resulting reactor model is simulated
using the ODE45 solver in MATLAB, with advanced machine learning algorithms and performance
metrics such as RMSE, MSE, and MAE employed to improve accuracy. The analysis reveals that
higher input discharge power and longer residence time result in increased tar analogue compound
(TAC) decomposition. The results indicate that higher input discharge power leads to a significant
improvement in the TAC decomposition rate, reaching 82.9%. The machine learning model achieved
very good agreement with the experiments, showing a decomposition rate of 83.01%. The model
flagged potential hotspots at 15% and 25% of the reactor’s length, which is important in terms of
engineering design of scaled-up reactors.Web of Science1615art. no. 583
Energy requirements for comminution of fibrous materials - qualitative chipping model
This paper aims to derive qualitative model for energy requirements for wood chipping process. There is relationship shown between energy requirements and properties of biomass, which is quite variable material. Relationship between comminution machinery and energy necessary for the process is highlighted. Derivation of the model is focused on chipping but in general it’s possible, to make it available both for different types of biomass (f. ex. agricultural residues) or for different type of comminution machinery (f. ex. hammermills) just by using different material properties adjusted to machinery mechanics. Properties used in derivation are mend to be easy to measure. Model is mend to be used as a base for quantitative model that, thanks to measurements performed on real comminution machinery and using wood with known properties, could give answers for two important questions: Would hypothetical changes in desired size of output material increase total system efficiency, taking into consideration lowest efficiency of combustion process (i. ex. higher amounts of unburned fuel)? How to optimise comminution as an operation in biofuel supply chain, with respect to energy used for the process
Energy requirements for comminution of fibrous materials - qualitative chipping model
This paper aims to derive qualitative model for energy requirements for wood chipping process. There is relationship shown between energy requirements and properties of biomass, which is quite variable material. Relationship between comminution machinery and energy necessary for the process is highlighted. Derivation of the model is focused on chipping but in general it’s possible, to make it available both for different types of biomass (f. ex. agricultural residues) or for different type of comminution machinery (f. ex. hammermills) just by using different material properties adjusted to machinery mechanics. Properties used in derivation are mend to be easy to measure. Model is mend to be used as a base for quantitative model that, thanks to measurements performed on real comminution machinery and using wood with known properties, could give answers for two important questions: Would hypothetical changes in desired size of output material increase total system efficiency, taking into consideration lowest efficiency of combustion process (i. ex. higher amounts of unburned fuel)? How to optimise comminution as an operation in biofuel supply chain, with respect to energy used for the process
Plasma Assisted Combustion as a Cost-Effective Way for Balancing of Intermittent Sources: Techno-Economic Assessment for 200 MWel Power Unit
Due to the increasing installed power of the intermittent renewable energy sources in the European Union, increasing the operation flexibility of the generating units in the system is necessary. This is particularly important for systems with relatively large installed power of wind and solar. Plasma technologies can be used for that purpose. Nonetheless, the wide implementation of such technology should be economically justified. This paper shows that the use of plasma systems for increasing the flexibility of power units can be economically feasible, based on the results of a net present value analysis. The cost of the installation itself had a marginal effect on the results of the net present value analysis. Based on the performed analysis, the ability to lower the technical minimum of the power unit and the relationship between such a technical minimum and the installed power of a plasma system can be considered decisive factors influencing the economics of the investment for such an installation. Further research on better means of prediction of the minimum attainable load, which would allow determining the influence of implementation of a plasma system, is recommended. This will be the decisive factor behind future decisions regarding investing in such systems
Evaluation of the performance of the cross/updraft type gasification technology with the sliding bed over a circular grate
In this article, a novel, pilot-scale gasification technology is closely described from the technological and design points of view. The construction of the fuel bed within the reactor is circular, operating according to the sliding bed principle, equipped with a tangential oxidiser intake. The technology combines principles of cross-draft and updraft gasification reactor type in an autothermal regime. In the model process with softwood pellets (spruce wood) as source fuel, the LHV of the producer gas reached 4.3 MJ.m- 3, with the overall conversion ratio reaching 80.3%. These results were obtained in a 709 +/- 10 degrees C environment with the fuel feed rate equal to exactly 30 kg.h-1 while the flow rate of the oxidising media was 17 +/- 1 m3 center dot h-1.The gas quality in terms of its content is a major factor to be considered. The purity of the producer gas is crucial for most final-use technologies. Thus, the question of polluting agents and undesired substances is ana-lysed and discussed in this article. The custom-made cleaning track of hereby described scientific technology can operate with 99.9% particulate matter removal efficiency, while tar compounds within the producer gas are kept as low as 9.7 g.m- 3.This article summarises a detailed description of a specific pilot-scale gasification unit where results of an experimental analysis are depicted along with real-time values and detailed schematic descriptions and illus-trations, providing a base for comparison with conventional technology designs.Web of Science167art. no. 10663