Mechanochemical and Size Reduction Machines for Biorefining

In recent years, we have witnessed an increasing interest in the application of mechanochemical methods for processing materials in biomass refining techniques. Grinding and mechanical pretreatment are very popular methods utilized to enhance the reactivity of polymers and plant raw materials; however, the choice of devices and their modes of action is often performed through trial and error. An inadequate choice of equipment often results in inefficient grinding, low reactivity of the product, excess energy expenditure, and significant wear of the equipment. In the present review, modern equipment employing various types of mechanical impacts, which show the highest promise for mechanochemical pretreatment of plant raw materials, is examined and compared—disc mills, attritors and bead mills, ball mills, planetary mills, vibration and vibrocentrifugal mills, roller and centrifugal roller mills, extruders, hammer mills, knife mills, pin mills, disintegrators, and jet mills. The properly chosen type of mechanochemical activation (and equipment) allows an energetically and economically sound enhancement of the reactivity of solid-phase polymers by increasing the effective surface area accessible to reagents, reducing the amount of crystalline regions and the diffusion coefficient, disordering the supramolecular structure of the material, and mechanochemically reacting with the target substances.     

Hydrodynamic analogies between the equations of classical hydrodynamics and electrodynamics in electrochemistry

It is shown that the use of equations of hydrodynamics of an incompressible and compressible fluid gives similar results for a number of experimental data from the field of classical electrodynamics used in electrochemistry. The analogue of electric current in wires is a stream that creates around itself a flow of a fluid. The analogue of electric field is the acceleration of a flow, whereas the analogue of magnetic induction is the frequency of a rotational motion of the fluid. Ampere’s law in hydrodynamics describes the interaction of flows with real bodies in terms of the Zhukovsky equation. The power laws in the fluid are similar, with some distinctions, to Maxwell equations. The expansion of the equations of conservation of momentum and mass in a series in perturbations leads to wave equations also similar to the Maxwell equations for the propagation of electromagnetic waves.     

Study of high-temperature oxygen permeability in Sr1 ? xLaxCo0.8 ? yNbyFe0.2O3 ? z perovskites

The oxygen permeability of ceramic SrCo_{0.8 − y} Fe_0.2Nb _y O_{3 − z} (0 ≤ y ≤ 0.2) and La_0.3Sr_0.7Co_0.6Fe_0.2Nb_0.2O_{3 − z} disc membranes as a function of temperature and oxygen partial pressure was studied. Kinetic analysis was performed based on the experimental data on oxygen permeability as a function of oxygen partial pressure.     

Spectral composition of the light from plasmas created by electron beams in nitrogen and He-N2 and Ne-N2 mixtures

Plasmas created by electron beams in N₂ and He-N₂ and Ne-N₂ mixtures at high pressures are studied experimentally. It is shown that N ₂ ⁺ ions in the B² _u ⁺ state are produced during charge exchange of Ne ₂ ⁺ ions with N₂ molecules. A comparison of the intensity of light from the B² _u ⁺ X² _g ⁺ transition of the N ₂ ⁺ ion in He-N₂ and Ne-N₂ mixtures shows that under these experimental conditions charge exchange of Net ions with N₂ is less effective than the analogous process involving He ₂ ⁺ ions. It is found that in an Ne-N₂ mixture the intensity of emission on transitions of the 2^t system of nitrogen is greater than in N₂.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 57–61, December, 1977.     

Investigation of the flow pattern in a gas-jet Hartmann resonator

A flow in a gas-jet resonator is investigated numerically and experimentally. The definition of the problem and a method of mathematical simulation are outlined. The results of simulation are discussed in comparison with the experimental data.     

The Effective Ionization of Air and Oxygen in a Near-Critical Electric Field at High Pressures

The effective ionization of air and oxygen at early stages of electric discharge development at medium and high pressures is analyzed. Ionization in an applied field with the participation of background electrons, electron sticking to and detachment from oxygen atoms and molecules, and recharging and conversion of negative ions is considered. The dependence of ion-molecular processes on external field is taken into account. The effective ionization value is shown to be different in constant and microwave fields. The effective air ionization values obtained in a microwave field are in agreement with the experimental data. It is shown that background electrons determine the possibility of effective ionization, whereas conversion processes determine the existence of a threshold E/N value, where E is the electric field strength and N is the density of neutral particles.     

Effective ionization of air in a near-critical electric field at high temperatures

The effective ionization at the early stages of the development of an electric discharge in air at moderate and high temperatures and pressures was analyzed. Ionization in an external electric field were studied with consideration given to background electrons, the attachment and detachment of electrons from atoms and molecules, and recharging and conversion of anions. The rates of ion-molecular reactions, in particular, detachment, depend not only on the external field strength but also on the temperature. The ionization thresholds were demonstrated to decrease with increasing temperature.