Two-stage Concentration Research Articles

Spectral splitting solar energy transfer in small-diameter multimode optical fiber based on two-stage concentration

A two-stage concentration system (TSC) is proposed for transfer spectral splitting solar energy via a small-diameter multimode optical fiber. The TSC includes a Fresnel lens that concentrates the energy before passing it through UV700 for spectral splitting. The system employs an optical fiber coupler for the second concentration stage and a single-diameter multimode fiber for energy transfer. We established a mathematical model of TSC, coupled optical fiber transmission, and analyzed it via simulation and experimentation. Simulation results demonstrate that the TSC reduces the spot's energy by 42% of the thermal radiation spectrum, decreases the focal spot radius by 58%, and improves the energy flux by 10.93 times with UV700. Additionally, experimental findings reveal that the TSC reduces the focal spot energy by 40.46% of the thermal radiation spectrum, decreases the fiber end temperature by 59.52%, identifies the optimal coupling distance at 308.75 mm, and yields a coupling efficiency of 60.7%.

Integration of a micropreconcentrator with solid-phase microextraction for analysis of trace volatile organic compounds by gas chromatography-mass spectrometry

The analysis of toxic volatile organic compounds (VOCs) in environmental air is important because toxic VOCs induce adverse effects on human health. Although gas chromatography- mass spectrometry (GC–MS) is the standard instrument for analysis of trace VOCs in air, this mode of analysis requires preconcentration and cryogenic processes. The preconcentration and subsequent thermal desorption of VOCs require special instruments and a long time of processing sample that significantly limit applications of GC–MS for monitoring indoor and outdoor VOC levels. Using a microfabricated preconcentrator for VOC analysis also has the challenge of a large sample volume for concentration. Using solid-phase microextraction (SPME) for VOC analysis by GC–MS often approaches the limit of detection of the GC–MS instrument for trace VOCs in air. This work reports a simple method to integrate microfabricated preconcentrators with commercial SPME fibers in a two-stage concentration processes to achieve rapid and reliable measurement of trace VOCs in air by GC–MS. We designed and fabricated a preconcentrator with micropillars in a microfluidic chamber to support sorbents and to increase the heat transfer rate to the sorbents for rapid thermal desorption. The effects of air flow rates through the preconcentrator on VOCs adsorption and thermal desorption were optimized for increasing analytical accuracy of VOCs measurements. The integration of a micropreconcentrator with SPME enabled measurements of sub-ppb levels of benzene, toluene, ethylbenzene, and xylene (BTEX), and trichloroethylene (TCE) in environmental air by GC–MS.

Transversely pumped solar Nd3+-doped fiber laser

In order to improve the coupling efficiency of solar fiber lasers, a new kind of transversely pumping geometry is proposed. A two-stage concentration system is designed to concentrate the sunlight into the Nd-doped fiber coiled in a ring chamber with high-reflective inner surfaces. The primary concentrator is an off-axis Fresnel lens with a radius of 600 mm, and the secondary concentrator is a compound parabolic optical waveguide. With this concentration configuration, the collection efficiency can be as high as 21.4%. 73.5 W solar power is absorbed by the fiber core according to ray-tracing simulation. Output characteristics of the solar fiber laser are further analyzed by calculating the rate equations. 2.6 W laser output is obtained and the slope efficiency reaches 3.7%.

Высокопроизводительный аэрозольный пробоотборник с рециркуляцией жидкой фазы и предварительным концентрированием

Testing the surrounding environment for the presence of biogenic aerosols is crucial in ensuring its safety for the population. It is often necessary to collect aerosol samples from large areas in short time, which demands excellent particle collection efficiency, a sufficient incoming air flow rate and a capacity to maintain the viability of the collected samples. Below we present the aerosol sampler with a high volumetric flow rate based on a two-stage particle concentration algorithm and consisting of a virtual impactor and a cyclone concentrator with a recirculating liquid phase. We provide all necessary calculations and an algorithm for modeling impactor parameters. The sampler was tested using dry and liquid formulations dispersed into the particles of 0.5 to 5 μm in diameter. We demonstrate that at volumetric flow rates over 4,000 l/min efficiency of particle collection into the liquid phase at a volume of 10 ml makes over 20% of the total aerosol mass and at volumetric flow rates over 300 l/min this value is over 60%. The proposed device maintains viability of the collected microorganisms. The sampler is portable, with flexible settings for sampling and cleaning, and can be controlled remotely over the network.

Optical analysis and output evaluation for a two-stage concentration photovoltaic system by using Monte Carlo ray-tracing method

A two-stage reflecting concentration photovoltaic (CPV) system is proposed by this paper. The optical analysis is carried out by using the Monte Carlo ray-tracing (MCRT) method. The relevant probabilistic models required in that method have been established. The effects of the CPV structural parameters on the optical performance are analyzed and a set of the preferred parameter values is obtained. Furthermore, the tracking error and the slope errors of the reflectors are considered in the optical simulation. Their influences on the position and size of the solar image are simulated. Then the scopes those errors should be limited in are proposed through the detailed optical analysis. The complete structural model of the CPV system is finally established. On its basis, the output characteristic of the CPV cell is analyzed in contrast with the flat PV cell. The calculated result shows that the output power of CPV system is higher than that of the flat PV system in some cases. And there is further potential for the CPV system to improve the photoelectric conversion efficiency and reduce the cost.

Modeling and optimization of fine coal beneficiation by hydrocyclone and multi-gravity separation to produce fine lignite clean coal

ABSTRACTWe evaluated the suitability, contribution to the national economy, and environmental impact of hydrocyclone and Multi-Gravity Separation (MGS) processes using fine-sized coal taken from the Soma coal sludge pond. The lignite coal tailings were treated by a two-stage concentration scheme for the recovery of fine clean coal. Pre-enrichment experiment parameters were determined by the Taguchi experimental design method, and the results were interpreted by the Statistical Packages for the Social Sciences (SPSS) 15.0 program to evaluate the optimum parameter values. The tailings initially contained 54.82% ash and had a LCV of 2,279 kcal/kg; after hydrocyclone pre-enrichment, the concentrate was 42.60% ash and had a calorific value of 2,573 kcal/kg (55.75% coal yield). After the final enrichment process, the ash of the pre-concentrated coal was decreased to 24.21% and left a clean coal with a base calorific value of 3,226 kcal/kg (36.16% coal yield). The total sulfur of the obtained clean coal was 0.52% and the combustible sulfur rate was 0.10%. To reduce the ash content of the obtained clean coal, a decantation process was performed that decreased the ash content to 21.84% and the base calorific value was increased to 4,109 kcal/kg.

Development of a highly effective multi-stage surface acoustic wave SU-8 microfluidic concentrator

As an important step in sample preparation, sample concentration step helps to improve sampling techniques that are often necessary to detect low levels of pathogenic bacteria in food safety inspections, reducing or completely eliminating the need for time-consuming cell enrichment process for detection. In this study, we investigated strategies to significantly enhance performances of a surface acoustic wave (SAW) microfluidic device to concentrate various particles, including microbeads, bacterial and mammalian cells in suspensions. A low acoustic energy loss material, SU-8, was used to fabricate the microfluidic concentrator, and SAW reflectors were designed to efficiently use the SAW generated acoustic energy for particle concentration. The concentration performance was further improved by using a two-stage concentration design. We demonstrated that the SU-8 microfluidic concentrator with a two-stage concentration configuration was able to concentrate 2.00μm bead samples at an overall concentration factor of ∼65-fold with a particle recovery efficiency of 81.9±5.9% at a inflow rate of 300μl/h. Similarly, when the concentrator was used to concentrate E. coli DH5α and NIH/3T3 cells, overall concentration factors of ∼59 and 75-fold with particle recovery efficiencies of 81.0±17.2% and 90.8±5.0% were obtained, respectively. These results show significant improvements upon those previously reported for either bacterial or mammalian cell concentration applications. In addition, the device fabrication process developed in this work is fully compatible with regular microfabrication processes, making this microfluidic concentrator readily integrable with other on-chip functionalities for cell manipulation and detection applications.

Separation Development Studies on the Beneficiation of Fine Lignite Coal Tailings by the Knelson Concentrator

While disposing of fine coal without use was cheaper and more permissible previously, recovering some of the fine coal changes the mass balance of wastes and makes co-disposal or integrated dumps possible. The present study aims to investigate the processing of fine lignite coal tailings with 59.08% ash content from Soma tailings ponds in Turkey using a Knelson concentrator and to identify in both numerical and experimental methods the fundamentals of the reason why the Knelson concentrator must be operated in hindered settling conditions for high efficiency separation of high ash-bearing fine lignite coal tailings. The lignite coal tailings were treated by a two-stage concentration scheme for the recovery of fine clean coal. Pre-enrichment experiment parameters were determined by the Taguchi experimental design method, and the results were interpreted by the SPSS 17.0 program to evaluate the optimum parameter values. After the pre-enrichment process, a coal concentrate (42.60% ash, 0.71% total sulfur, an...

Experimental investigation on paraboloid solar concentrator with a conical secondary concentrator

Material removal through ablation caused by concentrated solar thermal power is investigated. Experiments are conducted using a mirror-finish electroplated paraboloid along with a conical secondary concentrator in both fall and summer months in Al Ain city, UAE. Data collection for melting of aluminum shims facilitated the assessment of the feasibility of utilizing the available solar irradiance after the two-stage concentration. A geometric concentration factor of over 2800 is achieved for the first stage of power concentration with the current installation that also has a two-axis sun tracking system and a built-in pyrheliometer. The results confirm the feasibility of the approach, as the available power for ablation around solar noon is order of magnitudes higher than the power needed for the task, for the aluminum shim used. The main aim of the study is to hone the process to the power and precision of continuous pulse laser material removal, notably CO2 lasers, as challenges further reduction of the concentrated solar beams to acceptable tolerances remain to be successfully resolved. Copyright © 2014 John Wiley & Sons, Ltd.

Discrete Spectral Local Measurement Method for Testing Solar Concentrators

In order to compensate for the inconvenience and instability of outdoor photovoltaic concentration test system which are caused by the weather changes, we design an indoor concentration test system with a large caliber and a high parallelism, and then verify its feasibility and scientificity. Furthermore, we propose a new concentration test method: the discrete spectral local measurement method. A two-stage Fresnel concentration system is selected as the test object. The indoor and the outdoor concentration experiments are compared. The results show that the outdoor concentration efficiency of the two-stage Fresnel concentration system is 85.56%, while the indoor is 85.45%. The two experimental results are so close that we can verify the scientificity and feasibility of the indoor concentration test system. The light divergence angle of the indoor concentration test system is 0.267° which also matches with sunlight divergence angle. The indoor concentration test system with large diameter (145 mm), simple structure, and low cost will have broad applications in solar concentration field.

Design and analysis of two-stage transmitted-reflected concentration PV/thermal system with spectral beam splitter

For the traditional photovoltaic (PV) system which is under a full spectral concentrating condition, only a part of solar energy can be used by solar cells for PV power generation, the other part is not effective for the PV power generation and can result in temperature of solar cells increasing. High temperature can reduce the PV transformation efficiency of solar cells. In this study, a concentration PV/thermal system with beam splitter is proposed, which is composed of a linear Fresnel lens, a concave lens, a beam splitter, solar cells and a thermal receiver. The selective transmission coating on the splitter is designed to improve the incident condition of the sunlight on the surface of solar cells and reflect the noneffective part of sunlight to the thermal receiver for recycling. Theoretical analysis of the PV/thermal system is made and the results show that compared with the traditional concentration PV system, the two-stage transmitted- reflected concentration spectral beam splitting PV/thermal system has a high efficiency.

Two-stage electrodialytic concentration of glyceric acid from fermentation broth

The aim of this research was the application of a two-stage electrodialysis (ED) method for glyceric acid (GA) recovery from fermentation broth. First, by desalting ED, glycerate solutions (counterpart is Na+) were concentrated using ion-exchange membranes, and the glycerate recovery and energy consumption became more efficient with increasing the initial glycerate concentration (30 to 130 g/l). Second, by water-splitting ED, the concentrated glycerate was electroconverted to GA using bipolar membranes. Using a culture broth of Acetobacter tropicalis containing 68.6 g/l of D-glycerate, a final D-GA concentration of 116 g/l was obtained following the two-stage ED process. The total energy consumption for the D-glycerate concentration and its electroconversion to D-GA was approximately 0.92 kWh per 1 kg of D-GA.

Convection and surface radiation heat losses from modified cavity receiver of solar parabolic dish collector with two-stage concentration

Numerical analysis of solar dish modified cavity receiver with Cone, CPC and Trumpet reflectors is presented. Three-dimensional modeling is carried out to estimate the convective and radiative heat loss from the receiver for different angles of inclination and operating temperatures. Incorporating reflectors in the modified cavity receiver for second stage concentration, the natural convection heat losses are reduced by 29.23, 19.81 and 19.16%, respectively. The receiver with the trumpet reflector has shown better performance as compared to other configurations.

Wedge-shaped light concentrator using total internal reflection

One- and two-stage concentrations using wedge-shaped concentrators were proposed as static solar concentrators, where the light changes its direction with specular reflection at the rear surface and refraction or total internal reflection at the front surface. The condition for the total internal reflection gives the critical tilt angle of the wedge and consequently determines the maximum value of the concentration ratio. When the tilt angle is larger than the critical one, only the reflection at the front surface lowers the collection efficiency. Two-stage concentration can give a higher concentration ratio than one-stage concentration. A truncated-cone-shaped concentrator with tracking system can give higher concentration ratios than the two-dimensional wedge-shaped concentrators.

The optics of a two-stage solar furnace

The combination of a stationary parabolic dish concentrator and a heliostat has come to be known as solar furnace. The advantage of this combination as compared to a parabolic dish directly tracking the sun is that the focus is stationary. Both dish and instrumentation of the focus can be placed indoors. In the usual configuration a heliostat is facing a dish of approximately equal area. We have combined a rectangular glass heliostat of area 52 m 2 and focal length 100 m with a parabolic dish of area 5.7 m 2 and focal length 1.93 m to a two-stage concentrator. In this arrangement the heliostat produces a primary image of the sun at a distance of 100 m to the South. This image has a diameter of roughly 1 m. The bundle of rays contributing to this image has a cross section equal to the area of the dish at a distance of 70 m south of the heliostat. At this location we placed the dish in order to intercept all rays. From the primary image of the sun situated 30 m behind, the dish produces a secondary image in a plane situated 12 cm behind its focal plane. The secondary image is calculated to have a diameter of 6 cm and a numerical aperture of 0.64 ( f- number = 0.78 ). Thus except for reflectivity losses, the concentration ratio of the furnace is expected to correspond to that of the dish if used alone tracking the sun, while the total power is basically that intercepted by the much larger heliostat. This two-stage concentration has the advantage of requiring a smaller dish which can be at the same time cheaper and of higher optical quality. The disadvantage is that oblique reflection at the heliostat causes an astigmatism which distorts the secondary image to an ellipse roughly 15 cm × 6 cm and reduces the concentration ratio accordingly. This effect is larger for larger angles of incidence and for smaller dish dimensions. We show the flux distribution measured in the secondary plane of our heliostat and discuss possibilities to improve the optics by compensating the astigmatism.

Modified membrane-filter procedure for concentration of enteroviruses from tap water

Enteroviruses added to 114 liters of dechlorinated tap water were recovered in a 16-ml sample by a two-stage concentration procedure in which different types of membrane filters were used in each concentration stage. Viruses in tap water at pH 3.5 were first adsorbed to 10-in. (ca. 25.4-cm) epoxy-fiber glass filters (Filterite). Viruses adsorbed to these filters were eluted with a solution of 0.2 M sodium trichloroacetate buffered at pH 9 with 0.2 M lysine. Viruses in this solution were adsorbed to 47-mm asbestos filters (Seitz) without pH adjustment or other modification of the solution. Viruses were recovered from the Seitz filters with 16 ml of either Casitone or fetal calf serum at pH 9. With these procedures ca. 45% of several types of enteroviruses added to 114 liters of tap water could be recovered in the final 16-ml sample.

Fresnel lens analysis for solar energy applications

In this paper we analyze an arbitrarily shaped lineal Fresnel lens acting either as sole concentration stage or as the first stage of a two-stage concentration system in which the second stage considers the first as a Lambertian source. We determine the gain and position of the lens for all possible configurations, and we demonstrate that a curved lens with a refractive-index approaching infinity and with a given profile turns out to be an ideal concentrator.

Concentration of poliovirus from tap water using positively charged microporous filters

Microporous filters that are more electropositive than the negatively charged filters currently used for virus concentrations from water by filter adsorption-elution methods were evaluated for poliovirus recovery from tap water. Zeta Plus filters composed of diatomaceous earth-cellulose-"charge-modified" resin mixtures and having a net positive charge of up to pH 5 to 6 efficiently adsorbed poliovirus from tap water at ambient pH levels 7.0 to 7.5 without added multivalent cation salts. The adsorbed virus were eluted with glycine-NaOH, pH 9.5 to 11.5. Electropositive asbestos-cellulose filters efficiently adsorbed poliovirus from tap water without added multivalent cation salts between pH 3.5 and 9.0, and the absorbed viruses could be eluted with 3% beef extract, pH 9, but not with pH 9.5 to 11.5 glycine-NaOH. Under water quality conditions in which poliovirus recoveries from large volumes of water were less than 5% with conventional negatively charged filters and standard methods, recoveries with Zeta Plus filters averaged 64 and 22.5% for one- and two-stage concentration procedures, respectively. Electropositive filters appear to offer distinct advantages over conventional negatively charged filters for concentrating enteric viruses from water, and their behavior tends to confirm the importance of electrostatic forces in virus recovery from water by microporous filter adsorption-elution methods.