The αdecay path of the Hoyle state in
12
C (E
x
= 7:654MeV) represents one ofthe most challenging questions of modern nuclear physics. Its knowledge can help in theunderstanding of cluster ...configurations in light nuclei and the possible existence of Bose-Einstein condensates in nuclei. In stars, it is involved in the so-called 3αprocess, wherethe
12
C nucleosynthesis occurs. We studied the
14
N(d; α2)
12
C(7:654) reaction at 10:5MeVincident energy to probe its direct decay component. We found, with a precision higherof a factor 5 than any other previous experiment, an almost total absence of direct decaysby-passing the ground state of
8
Be. From our analysis, a new upper limit of such decayis found at 0:043% (95% C.L.). Astrophysical 3α process reaction rate calculations haveto be accordingly revised.
The investigation of the effects of average atomic ionization on nuclear reactions is of prime importance for nuclear astrophysics. No direct experimental measurement using a plasma target has been ...done yet. In this regard, we measured for the first time the neutron production of a (p,n) reaction in different states of ionization. The studied nuclear reaction was 51V(p,n)51Cr. We measured a significantly lower neutron production than expected when the target was ionized, even when taking into account existing electron screening theory or the effect of the stopping power in the target on the injected proton beam. This experiment is a first step in the process to characterize the influence of ionization at astrophysically relevant energies.
The decay path of the Hoyle state in \(^{12}\)C (\(E_x=7.654\textrm{MeV}\)) has been studied with the \(^{14}\textrm{N}(\textrm{d},\alpha_2)^{12}\textrm{C}(7.654)\) reaction induced at ...\(10.5\textrm{MeV}\). High resolution invariant mass spectroscopy techniques have allowed to unambiguously disentangle direct and sequential decays of the state passing through the ground state of \(^{8}\)Be. Thanks to the almost total absence of background and the attained resolution, a fully sequential decay contribution to the width of the state has been observed. The direct decay width is negligible, with an upper limit of \(0.043\%\) (\(95\%\) C.L.). The precision of this result is about a factor \(5\) higher than previous studies. This has significant implications on nuclear structure, as it provides constraints to \(3\)-\(\alpha\) cluster model calculations, where higher precision limits are needed.
Electron screening in an important effect that cannot be neglected in nuclear astrophysics, since it influences nuclear reaction cross sections at low energies. We are trying to understand why most ...measurements in inverse kinematics on solid targets give electron screening potentials more than an order of magnitude above predictions. Below we report our latest results on electron screening in nuclear reactions
1
H(
14
N,γ)
15
O and
2
H(
19
F,ρ)
2
°F in both inverse and normal kinematics. The analysis is in progress.
Devolatilisation is a process of volatile components formation that takes place immediately after the drying process and precedes combustion or gasification. The paper presents the procedure for ...determining the composition of devolatilisation products on the wheat residue biomass sample. The components considered devolatilisation products are carbon monoxide, carbon dioxide, hydrogen, water vapor, hydrogen sulfide, ammonia, ethene, methane, and tar. The procedure relies on two independent models that adopt two distinct principles. The first model of energy and mass balance does not consider the analysis of the influence of temperature, and therefore the system is indeterminate. The second model that involves the temperature influence is based on defining the equilibrium composition of gaseous components of the devolatilisation process by applying the principle of minimum Gibbs function. This model gives the gas-phase composition of the water/carbon dioxide, carbon monoxide/carbon dioxide, and hydrocarbons/carbon dioxide systems. Combining these two models using an iterative procedure leads to an exact composition of the devolatilisation products, including tar as a condensed product. The analysis was performed in the temperature range of 700–950 K. The model is validated against already published numerical and experimental work and presented a high level of agreement. The main advantage of the proposed combined parametric modelling relies on the simplicity of its input data which refers to the proximate and the ultimate analysis of the biomass feedstock.
•The combination of the energy and mass balance and the equilibrium composition models.•The model uses data only from proximate and ultimate fuel analysis.•Results accurately present the composition of devolatilisation products of wheat residue biomass.•The model can be applied to a wide range of energy-positive substances.
The article aims to define the optimal operating parameters of the gasifier such as temperature, equivalence ratio, steam-to-fuel ratio and selection of gasification medium for the process of thermal ...plasma gasification of sewage sludge. A comprehensive parametric study is carried out with the developed one-dimensional mathematical thermodynamic equilibrium model for plasma gasification. The model is based on the principle of the minimum of the Gibbs function and uses only the ultimate and proximate analysis data as input to the model. The output of the model is the equilibrium composition of the thermal plasma gasification products as a function of temperature in the plasma reactor. The parametric analysis has shown that the optimum conditions for the gasification process of sewage sludge are a temperature of 1200 K and an equivalence ratio of 0.2 for the air gasification case, i.e. 1200 K and the steam-to-fuel ratio of 0.1 for the case of steam gasification. When comparing the different gasification media, gasification with steam leads to a higher yield of H2 in the produced syngas. For the selected optimal conditions, the economic analysis of the process shows that the price of gasification per ton of sewage sludge is lower in the case of steam gasification and amounts to 72.30 €/t, compared to 88.12 €/t in the case of air gasification. The analysis was carried out using the example of a plant with a capacity of 360 kg/h. The sensitivity analysis was carried out taking into account the influence of the electricity price, labor costs, the price of CO2 emissions and the ash disposal price. The analysis shows that labor costs have the greatest influence on the price of thermal plasma gasification of sewage sludge.
•Treatment of hazardous waste with polychlorinated biphenyls in thermal plasma.•The influence of different working media on the process parameters was investigated.•Yield of harmful and combustible ...species at different system temperatures calculated.•Suitable mixing of hazardous waste with used engine oil showed advantages.•Distinct optimum was found with regard to the working medium and power consumption.
This paper proposes a mathematical modelling approach to determine the thermodynamic equilibrium of chemical systems in order to optimise the operating parameters of the plasma chemical processes in a low-temperature thermal plasma pilot reactor with a direct current electric arc for the treatment of hazardous waste containing polychlorinated biphenyls. The model is primarily based on the principles of mass action and minimum Gibbs free energy. The obtained results can serve as a basis for multi-criteria optimisation based on ecological aspects, reduction of energy consumption and the possibility of using the produced synthetic gas for energy recovery in the process. The analysis carried out clearly showed the advantages of using water vapour as a plasma working medium and the appropriate mixing of the organic waste containing polychlorinated biphenyls with used engine oil for enriched syngas production. The presented analysis determines the optimal reactor temperature for an ecologically efficient treatment and shows possibilities for energy recovery in the process. The proposed model can also be used for other chemical reactors and for the treatment of other chemical substances.
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