AlN Production in Co-Flow Filtration Mode at Low Pressures

In this work, the process for obtaining aluminum nitride in the combustion mode of co-flow filtration of a nitrogen–argon mixture was investigated. The combustion of granules consisting of aluminum and aluminum nitride as an inert diluent was studied under conditions of co-current filtration in a flow of nitrogen and a nitrogen–argon mixture in the range of a specific flow rate of 1.5–5.0 cm3/(s∙cm2). It was found that the specific flow rate of the gas mixture and the amount of argon in the nitrogen–argon mixture had a significant effect on the rate and the temperature of combustion. The structure and phase composition of the synthesis products were studied. The maximum achieved yield of the AlN phase was 95 wt.%. Moreover, this method is energy efficient and allows the production of metal nitrides without the use of high-pressure reactors.

The Study of Fire-extinguishing Process of Modelled Fire Seats

Test-fires to determine fire-extinguishers’ efficiency for extinguishing B class fires are conducted by operators equipped with working clothes, which does not comply with the requirements of physical modelling. This is why the ranks of extinguished modelled seats are significantly overestimated. The quantitative results of fire seats’ extinguishing can be comparatively evaluated in accordance with the value of specific flow rate of a fire-extinguishing agent. As it was detected, the specific flow rate of a fire-extinguishing agent does not actually depend on the rank of modelled fire seat when extinguished by an operator wearing thermal-protective clothes. At the same time, it is increasing along with the expansion of the fire zone scale in case the fire is extinguished without special protective clothes. Consequently, to increase the fire-extinguisher’s efficiency data reliability, the certifying tests should be conducted in conditions close to the real application conditions when the first person to firefight is not equipped with such special protective clothes. The experimental studies to determine the specific flow rate of a fire-extinguishing agent used modelled fire seats of various ranks. The analysis of results showed that the fire-extinguishers ensuring generation of drops of prevailing size more than 0,5 mm are required to extinguish the modelled sire seats. The degree of increasing flow rate for the fire-extinguishing agent to eliminate a fire and observation of a safe distance from the flame for an operator are conditioned by the scale of fire zone and affect the specific flow rate of agent required to ensure stable fire-extinguishing. Based on the results of extinguishing the fire seats «34В» or «55В», it is demonstrated that via using a correction factor it is possible, assuming an acceptable error, to evaluate the flow rate of fire-extinguishing agent to extinguish a modelled fire seat of any rank.

Determining the main regularities in the process of mineral fertilizer granule encapsulation in the fluidized bed apparatus

This paper has substantiated the expediency and prospects of obtaining organomineral fertilizers by encapsulating mineral granules with an organic suspension in fluidized bed apparatuses. An overview of existing approaches to the mathematical description of the kinetics of granule growth in granulation processes in fluidized bed apparatuses is presented. A mathematical model of the kinetics of the formation of a hard shell around granules in a fluidized bed has been built. It shows that the kinetics depend on the size of the retour particles, the specific flow rate of the suspension, the density of the suspension and granules, and the time of the process. Equations have been derived for determining the thickness of the hard shell and the specific flow rate of the suspension for individual granulation stages in a multi-stage granulator of the fluidized layer. Analytically, graphical dependences were built, which showed an increase in the thickness of the hard shell due to an increase in the specific flow rate of the suspension, the diameter of the retour particles, and the time of the encapsulation process. The equations make it possible to determine the rational regime and technological parameters of the encapsulation process in order to obtain a coating of the predefined thickness at the surface of the granules. This ensures that a quality product is obtained, with a granulometric composition in a narrower range of particle size. To obtain granules of 2.5–4 mm in size, it is necessary to carry out the process in three- or four-stage granulators of the fluidized bed at specific suspension consumption of (10–20)∙10-4 kg/(kg∙s.). It is shown that with uniform growing of granules with a constant increase in the thickness of the shell in multistage granulators, the suspension consumption decreases by 2‒3 times from the first stage to the subsequent ones. This approach reduces the operating and energy costs of the process.

Removal of arsenic from aqueous solution containing hexafluoroarsenate

Arsenic removal from aqueous solutions containing hexafluoroarsenate or arsenate by strong and weak base anion exchangers was studied by dynamic column tests that were carried out using solution containing arsenic and accompanying anions (chlorides, sulfates and fluorides). The specific flow rate of solution was 6 BV/h. Desorption of arsenic was carried out by 1 mol/L NaOH or 2 mol/L KSCN. All the studied anion exchangers performed well in the absence of accompanying anions. In the presence of chlorides and sulfates, studied exchangers showed high selectivity towards hexafluoroarsenate.

Highly accurate and New approach for quantiϐication of Gramicidin in medication by RP-HPLC

A significant Reverse Phase-High performance Liquid Chromatography technique was developed for a more accurate, unique and quick economical method was developed for the analysis of Gramicidin in medication dosage forms. The separation of this drug Gramicidin was done by using the X-Bridge phenyl column as a stationary phase, and a mixture of acetonitrile + buffer in 50:50 v/v ratio was used as a movable phase. The buffer used in this method was Octane sulphonic acid of pH-2.5 adjusted with OPA. The maximum absorbance of eluents was observed at 235 nm. A specific flow rate (1 ml/minute) was maintained throughout the runtime of 8 min. The selected drug is eluted at 2.49 minutes. The selected drug obeys Beer Lambert's law in the concentration range of 0.5-7.5 µg/ml of Gramicidin. The percentage of recovery was found to be within the acceptable limit. The selected approach was corroborated with ICH standard ground rules, and the results of parameters like method precision, accuracy, ruggedness, robustness, and degradation studies were found to be within the allowable limit. Thus, the present method was successfully applied for the simultaneous analysis of Gramicidin in routine industrial work.

A NOVEL DESIGN OF THE ROOTS BLOWER

This paper reports a novel curve developed from non - circular gearing theory, which can be applied in rotor profile design of the two - lobe Roots blower. The formulas for calculating the volumetric efficiency and specific flow rate of the blower have also been established. To evaluate this type of the Roots blower, the volumetric efficiency and specific flow rate are being compared with those parameters of the two traditional designs and one recent variant.

Recent Developments in Efficiency Enhancement of Non-Concentrating Photovoltaic Systems by Thermal Methods

Two different methods for reducing the operating temperatures of non-concentrating photovoltaic panels are analyzed and the performances are compared. Forced air cooling using a low power fan and use of a thermo siphon heat pipe are the modifications proposed for the purpose of efficiency enhancement. Experimental results of the two techniques are compared. It was found that, using a specific flow rate and selection of the proper heat pipe fluid and its operating conditions could help to reduce panel temperature considerably.

A Harmony Search Algorithm for the Reproduction of Experimental Data in the Social Force Model

Crowd dynamics is a discipline dealing with the management and flow of crowds in congested places and circumstances. Pedestrian congestion is a pressing issue where crowd dynamics models can be applied. The reproduction of experimental data (velocity-density relation and specific flow rate) is a major component for the validation and calibration of such models. In the social force model, researchers have proposed various techniques to adjust essential parameters governing the repulsive social force, which is an effort at reproducing such experimental data. Despite that and various other efforts, the optimal reproduction of the real life data is unachievable. In this paper, a harmony search-based technique called HS-SFM is proposed to overcome the difficulties of the calibration process for SFM, where the fundamental diagram of velocity-density relation and the specific flow rate are reproduced in conformance with the related empirical data. The improvisation process of HS is modified by incorporating the global best particle concept from particle swarm optimization (PSO) to increase the convergence rate and overcome the high computational demands of HS-SFM. Simulation results have shown HS-FSM’s ability to produce near optimal SFM parameter values, which makes it possible for SFM to almost reproduce the related empirical data.

Factors Influence on Bacterial Cellulose Growth in Static Reactors

Synthesis of bacterial cellulose by Acetobacter xylinum in static conditions was performed. In order to optimize the cultivation conditions a factorial experiment with four factors (operating temperature, substrate concentration, co-substrate concentration and air specific flow rate) and two levels was used. Correlations between cellulose yield, respectively added water specific use, and process factors were established.