Precise measurement of beta spectra was always of great importance in some fundamental problems, including those of neutrino physics. The results obtained by measuring the spectrum of a
Ce–
Pr source ...with setups of two types to a precision substantially improved in relation to earlier investigations are presented. The correctness of a theoretical fit is tested using the shape of the
Pr (0
)
Nd (1
) allowed beta transition.
The article describes the investigation of the torrefaction process of four samples of biomass (brewer’s grains, sewage sludge, distillery stillage, and coffee grounds) in a fluidized bed in an ...environment of superheated steam at a temperature of 300°C and in a flue gas environment (oxidative torrefaction) at a temperature of 250°C. It has been established that the torrefaction of brewer’s grains, distillery stillage and coffee grounds produces biochar with a higher carbon content and a higher calorific value than that of the raw biomass. In addition, it has been found that the best raw material for producing biochar among the studied biomass samples is coffee grounds; brewer’s grains is somewhat inferior to it. It is not advisable to use sewage sludge and distillery stillage as raw materials for biochar production.
Resonance excitation of the
83
Kr first nuclear level (
E
= 9.4 keV) by solar axions formed via the Primakoff mechanism is sought. The γ- and X-ray photons and the conversion and Auger electrons ...arising from the excited-level relaxation are detected with a gas proportional counter of a low-background detector in the underground Baksan Neutrino Observatory. The following experimental constraint is obtained for the product of the axion–photon coupling constant and the axion mass:|
g
A
γ
×
m
A
| ≤ 6.3 × 10
-17
In the framework of the hadronic-axion model, this corresponds to a new axion-mass constraint of
m
A
≤ 12.7 eV at 95% C.L.
In this work, two types of nanoporous alumina membranes were prepared and tested. Structural features of the samples obtained by using different acids were investigated by scanning electron ...microscopy (SEM). And further SEM-images were analyzed by different types of fractal dimension estimation methods. The transmission and scattering of accelerated He+ ions were studied in experiments on the ion irradiation of dielectric channels based on porous alumina. An ion accelerator was used as a source of the He+ beam with an energy of 1.7 MeV. Ion scattering was studied by Rutherford backscattering spectrometry. Helium transition through nanoporous alumina at various angles between the normal to the sample and the beam direction were observed. It is shown that the porous structure of anodic aluminum oxide is excellent as a dielectric matrix of nanocapillaries. Owing to the small angle scattering, it allows for the transportation of the accelerated charged particles through the dielectric capillaries, and, as a result, the localization of high energy ion irradiation effects. Additionally, according to the transmission of UV–V is spectra, the energy gaps of samples obtained were calculated.
A simple method is proposed for calculating the minimum velocity of fluidization of a bed consisting of particles differing considerably in shape and size. The method helps calculate with ...satisfactory engineering precision the minimum fluidization velocity on which depend the size of the reactor for wet biomass torrefaction, the flow rate of the fluidizing agent, and other characteristics of the torrefaction process.
An experimental investigation has been conducted into combined hydrothermal fluidized carbonization of poultry litter and sawdust in a superheated steam medium. The effects of temperature on the ...duration of the process of hydrothermal carbonization have been identified, and the composition of the noncondensable gaseous products of carbonization has been established.
—
Accumulation of chicken manure with litter (sawdust or fragmented straw) that is produced in large quantities at poultry farms (in producing 1 kg of poultry, 1–3 kg of manure with litter is ...obtained) poses a serious problem for the environment. Poultry farms are among the largest consumers of electricity, which can be generated by combusting manure with litter, also jointly with coal, in bubbling or circulating fluidized bed furnaces. For making the combustion more efficient and environmentally friendly (reducing carbon oxide emissions) the manure wetness and the content of volatiles in it should be decreased, and its heating value should be increased. To this end, manure with litter can be subjected, prior to its combustion, to pretreatment using the hydrothermal carbonization or torrefaction method. The article presents a comparison of the results obtained from studies of methods for processing a mixture of chicken manure and sawdust into biofuel in superheated steam. Chicken manure and its mixture with sawdust in the ratios 1 : 1, 1 : 2, and 2 : 1 were subjected to thermochemical treatment. Hydrothermal carbonization was carried out in a batch laboratory autoclave at a temperature of 220°С for 1 and 4 h. Biomass torrefaction was carried out in a fluidized bed reactor with the bed formed by biochar particles that were preliminarily obtained in superheated steam at temperatures of 300 and 350°С. It has been found that by applying the hydrothermal carbonization method, the carbon content in manure with litter can be increased from 42 to 63%, and the higher heating value from 16.7 to 17.8 MJ/kg. In turn, by applying the method of fluidized bed torrefaction in superheated steam, these indicators can be increased to 75% and 18.8 MJ/kg, respectively. The hydrothermal carbonization and torrefaction processes require significant energy expenditures. For making both processes more economically efficient, the possibility of extracting, from the spent water (or condensate), 5-hydroxymethylfurfural, which is regarded as a key reagent, a so-called platform chemical, for producing various practically important substances, including polymers, pharmaceutical drugs, solvents, and fuels, is being researched. It has been determined that the content of 5-hydroxymethylfurfural in these aqueous media makes 0.02–0.80 g/dm
3
and depends on the biomass thermochemical treatment method and temperature at which the process was performed.
Consideration has been given to problems of chemical activation of a solid product of hydrothermal carbonization (hydrochar) of biomass. Pellets from a mixture of poultry litter and straw subjected ...to carbonization in a fluidized bed in a medium of superheated water vapor at a temperature of 300°C were impregnated with water solution of ferric nitrate, dried in the air at a temperature of 100°C, and held for 2 h at a temperature of 300°C for degradation of iron(III) nitrate and its transformation into iron oxides. The pellets were activated at a temperature of 700–800°C in a horizontal tube furnace in an inert argon atmosphere. The obtained ferromagnetic sorbents have a rather developed system of micro- and mesopores. Furthermore, a twofold increase in the duration of activation results in an 18% increase of the pore specific surface, and the rise in the temperature of the activation process leads to an increase in this surface by 45%.
Torrefaction is considered as a method for producing biofuels with improved characteristics compared to those of the “raw” biomass (higher calorific value, moisture resistance, better grindability). ...The torrefaction process is an endothermic process that is usually carried out in a gaseous atmosphere in the absence of oxygen. To reduce the required heat input, it is proposed to employ the oxidative torrefaction and conduct the process in a fluidized bed agitated with flue gases containing less than 6% oxygen. Preliminary studies of the oxidative torrefaction of sunflower husks, including thermogravimetric analysis of the treated material, have shown that the heat treatment time for the biomass should be at least 5 min. A fluidized bed is a reactor with ideal mixing of the treated material where uniform treatment of raw material particles cannot generally be attained. To overcome this disadvantage of the fluidization technique and achieve the required residence time for biomass in a fluidized bed during a continuous torrefaction process, it was proposed to equip a torrefaction reactor with a series of vertical baffles spaced at 50 mm. These baffles induce a loop-like flow of the processed biomass from the inlet to the outlet of the reactor. To investigate the residence time for husk particles in the reactor, a tracer, which was colored to husk particles' color with a water-soluble dye which did not change the weight and size of the particles, was injected into the bed of uncolored particles. Tracer samples were taken every 30 s at the outlet of the reactor and were analyzed using a special procedure to determine the fraction of colored particles in each sample. This enabled us to gauge the time during which the colored particles injected into the fluidized bed reached the point of their discharge from the bed. Studies performed in a “cold” model of the reactor showed that a series of vertical baffles in the bed can provide the required residence time for biomass in a reactor including commercial reactors. Plates can provide the necessary biomass residence time in the reactor.
