Dynamic population balance and flow models for granular solids in a linear vibrating screen

Vibrating screens are a widely applied form of particle separations. In spite of this significance, their understanding is still an obstacle. Three approaches were used to characterize the flow of granular material in a linear vibrating screen. The statistical model, mass action, and kinetic model based on conservation of momentum were derived. Experiments were then conducted on a multi‐sized prototype screen and glass beads of sizes 0.75, 1, 2, 3 mm. Deck inclinations were varied over 7.5,12.5, and 17.5°, and frequencies over 7, 15, and 20 Hz. A total of 72 feed batches and a constant power of 50 W was used. The experimental data was then used to validate the models. The three models provided accurate flow prediction over the screens. Additionally, the kinetic model also provided a basis for optimal design of the screening unit operation, by allowing manipulation of seven design variables to obtain a 95–100% efficient vibrating screen. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3889–3898, 2016     

European Minor Constituent Radiometer: A New Millimeter Wave Receiver for Atmospheric Research

EMCOR is a heterodyne receiver for the frequency range of 201 to 210 GHz. It has been designed for ground-based measurements of various minor constituents of the stratosphere involved in ozone chemistry. Since the aim was the detection of faint spectral lines, a superconducting tunnel junction has been chosen as mixer element and special care has been taken in developing the calibration unit of the system. The front-end is completed by a quasi-optical system, a solid state local oscillator with electronic tuning and a HEMT pre-amplifier. In the back-end an acousto-optical spectrometer is employed to analyse the signal. A PC controls the whole system. The instrument has been installed at a high mountain site in the Swiss Alps.     

Cooled Schottky varactor frequency multipliers at submillimeterwavelengths

The efficiency of a Schottky varactor frequency multiplier at submillimeter wavelengths can be increased by cooling the diode. The increased mobility of the free carriers causes the series resistance to decrease, and the efficiency can increase as much as a few dB at low input power levels. At high output frequencies and at high power levels the efficiency of the multiplication is decreased by the current saturation, because the junction capacitance cannot be pumped effectively. When the diode is cooled, the maximum current of the diode increases and much more output power can be expected. There are also slight changes in the I-V characteristic and in the diode junction capacitance, but they have a negligible effect on the efficiency of the multiplier. The theoretical maximum output power near 1 THz is calculated to increase by about 10 dB from 50μW to 500μW, when the multiplier chain is cooled to 77 K. However, considerable improvement in the efficiency can be achieved by cooling to 150 K, which is easily attained in space by passive cooling     

Assessment of water quality in the vicinity of peat extraction sites: The case of Pien‐Saimaa,Finland

Peatlands have an important global role as carbon sinks. Locally, however, peat bog extraction can cause pollution in nearby watercourses. The aim of this study is to investigate the application of multivariate methods in the renovation and protection of eutrophic lakes surrounded by agricultural and peat extraction areas. The analytical data used in the study originated from a national water quality database and the period studied was 2000–2013. Multivariate methods: Principal Component Analysis (PCA) and Parallel Factor Analysis (PARAFAC) were applied to solve interactions of variables and pollution sources in a complex water ecosystem. Leaching from the peat bog area was found to be the main source of iron, which has an important role as a precipitator of phosphorus in loose sediment and in water. Nutrient ratios had no direct correlation to algae blooms, but high ratios indicated an increased likelihood of an upcoming bloom.     

Influence and CFD analysis of cooling air velocity on the purification of aqueous nickel sulfate solutions by freezing

Finite energy resources and their rapidly waning imprint necessitate a sustainable wastewater treatment method. Nature could be exploited to freeze wastewater in locations which experience subzero temperatures during winter. The two most vital components that influence the efficiency of natural freezing are the ambient temperature and air velocity. The turbulent and unsteady air‐cooled natural freezing is simulated for ice crystallization from 0.1 wt % and 1 wt % NiSO₄ (aq) solutions. The efficiency of natural freezing is tested for different air velocities (2 ms^?1, 5 ms^?1) and levels of undercooling (ΔT = 0.5°C, 1°C) from the freezing temperature of the corresponding solution. The airflow in the winter simulator is modeled by computational fluid dynamics to investigate its behavior and to assess its effect on freezing. © 2017 American Institute of Chemical Engineers AIChE J, 63: 200–208, 2018     

A frequency doubler for 200 GHz with a planar Schottky varactor

A frequency doubler for 200 GHz utilising a planar surface channel Schottky varactor was designed, constructed and tested. The doubler employes novel split-waveguide mount design with two sliding backshorts at both input and output waveguides. The theoretical maximum efficiency of the doubler is 44.0 % with input power level of 32 mW and the maximum output power is 16.5 mW with input power level of 50 mW. The measured maximum efficiency of the doubler was 7.1 % and the maximum output power was 2.6 mW     

Spawning habitat of Atlantic salmon and brown trout: general criteria and intragravel factors

Generalized habitat criteria for spawning sites of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) using depth, water velocity and substrate size were created based on published information. In addition, information on critical intragravel conditions for egg development was summarized. Salmon spawned mostly in relatively deep, swift‐velocity habitats (20–50 cm, 35–65 cm s^?1), whereas trout selected slightly shallower and slower flowing spawning sites (15–45 cm, 20–55 cm s^?1). Salmon and trout preferred pebbles (16–64 mm) for spawning. The minimum oxygen concentration for successful incubation of eggs varies with the developmental stage of eggs, and supply of it may be reduced by deposited fine sediment. Habitat criteria for spawning sites are narrower than those for small juveniles; therefore the use of separate criteria is recommended. In addition to the traditional habitat criteria variables (depth, water velocity, substrate), the critical intragravel factors affecting egg survival should be incorporated in biologically meaningful criteria for spawning habitat modelling. Copyright © 2008 John Wiley & Sons, Ltd.     

Process control and monitoring of reactive crystallization of L‐glutamic acid

The aim of the present study was to investigate feedback control of a reactive crystallization process. The present study built up a control structure needed to control the driving force of reactive crystallization using the feed rate of added acid. The concentration of the crystallizing compound and pH was used to compute feedback in the closed‐loop control of semi‐batch precipitation. The concentration of L ‐glutamic acid was determined from measured MID‐IR ATR‐FTIR spectra based on a multivariate model. Dynamic change of set value was based on the mass of added sulfuric acid and pH. The studied properties of the product crystals were polymorphism and crystal size. The polymorphic composition was analyzed with a Raman spectrometer and was expressed by mass fraction of the α‐polymorph. The obtained results showed that the developed feedback process control system allows effective control of forming of polymorphs. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Screening of Binary Solvent Mixtures and Solvate Formation of Indomethacin

The applicability of solubility parameters and solvent activity in the screening of binary solvent mixtures was studied. The solubility of indomethacin was measured in binary mixtures of dichloromethane, acetone, and ethyl acetate with methanol and ethanol. Solubility extremes in the mixed solvents were observed. The solubility maxima were related to the excess Gibbs free energy of the solvents and the hydrogen bonding term of the Hansen solubility parameter. The solvates of indomethacin were characterized with a confocal Raman spectrometer, and the desolvation of the solvates was investigated with thermogravimetry.