Development of stable low-electroosmotic mobility coatings

Long-time rinsings of the Z6040-methlycellulose coating used successfully on the ASTP MA=011 experiment indicate the permanency of this coating is inadequate for continuous flowing systems. Two approaches are described for developing coatings which are stable under continuous fluid movement and which exhibit finite and predictable electroosmotic mobility values while being effective on different types of surfaces, such as glass, plastics, and ceramic alumina, such as is currently used as the electrophoresis channel in the GE-SPAR-CPE apparatus. The surface charge modification of polystyrene latex, especially by protein absorption, to be used as model materials for ground-based electrophoresis experiments, and the preliminary work directed towards the seeded polymerization of large-particle-size monodisperse latexes in a microgravity environment are discussed

Electrophoresis experiment for space

The Apollo 16 electrophoresis experiment was analyzed, demonstrating that the separation of the two different-size monodisperse latexes did indeed take place, but that the separation was obscured by the pronounced electroosmotic flow of the liquid medium. The results of this experiment, however, were dramatic since it is impossible to carry out a similar separation on earth. It can be stated unequivocally from this experiment that any electrophoretic separation will be enhanced under microgravity conditions. The only question is the degree of this enhancement, which can be expected to vary from one experimental technique to another. The low-electroosmotic-mobility coating (Z6040-MC) developed under this program was found to be suitable for a free-fluid electrophoretic separation such as the experiment designed for the ASTP flight. The problem with this coating, however, is that its permanency is limited because of the slow desorption of the methylcellulose from the coated surface

Reverse electrodialysis – Multi effect distillation heat engine fed by lithium chloride solutions

Salinity Gradient Heat Engines (SG-HEs) have been proposed as a promising technology for converting low-temperature heat into electricity. The SG-HE includes two different processes: (i) a salinity gradient process where the salinity gradient between two solutions is converted into electricity and (ii) a thermal regeneration process where low-grade heat (T<100°C) is used to re-establish the original salinity gradient of the two streams. Among the proposed working solutions, aqueous solution of lithium chloride has been identified as one of the most promising thanks to its remarkable solubility and activity. In this work, a process model to study the performance of a SG-HE constituted by a Reverse ElectroDialysis (RED) unit coupled with a Multi Effect Distillation (MED) unit fed with lithium chloride solution is presented. The influence of the concentration of the inlet solution in the RED unit and the temperature difference in the evaporators of the MED unit on the performance were evaluated by considering ideal membranes. Furthermore, the impact of membrane permselectivity and resistance on the system performance was evaluated. Results showed promising system efficiencies, making this technology attractive for conversion of low-grade heat (<100°C) into electricity, but membrane properties should be enhanced

Process for preparation of large-particle-size monodisperse latexes

Monodisperse latexes having a particle size in the range of 2 to 40 microns are prepared by seeded emulsion polymerization in microgravity. A reaction mixture containing smaller monodisperse latex seed particles, predetermined amounts of monomer, emulsifier, initiator, inhibitor and water is placed in a microgravity environment, and polymerization is initiated by heating. The reaction is allowed to continue until the seed particles grow to a predetermined size, and the resulting enlarged particles are then recovered. A plurality of particle-growing steps can be used to reach larger sizes within the stated range, with enlarge particles from the previous steps being used as seed particles for the succeeding steps. Microgravity enables preparation of particles in the stated size range by avoiding gravity related problems of creaming and settling, and flocculation induced by mechanical shear that have precluded their preparation in a normal gravity environment

Adsorption from Solution

A major problem of the thermodynamic theory of adsorption at the solid/liquid interface is concerned with the definition of the heterogeneous surface in terms of mathematically treatable model. The paper gives a review of the theoretical approaches applied to studies of adsorption from concentrated and diluted binary mixtures. Experimental work has enjoyed much success since the uniform surface, graphitized carbon blacks became available. Results are described and discussed of measurements of heats of immersion on such surfaces

Adsorption from Solution

A major problem of the thermodynamic theory of adsorption at the solid/liquid interface is concerned with the definition of the heterogeneous surface in terms of mathematically treatable model. The paper gives a review of the theoretical approaches applied to studies of adsorption from concentrated and diluted binary mixtures. Experimental work has enjoyed much success since the uniform surface, graphitized carbon blacks became available. Results are described and discussed of measurements of heats of immersion on such surfaces

Evaluation of the economic and environmental performance of low-temperature heat to power conversion using a reverse electrodialysis - Multi-effect distillation system

In the examined heat engine, reverse electrodialysis (RED) is used to generate electricity from the salinity difference between two artificial solutions. The salinity gradient is restored through a multi-effect distillation system (MED) powered by low-temperature waste heat at 100 ◦C. The current work presents the first comprehensive economic and environmental analysis of this advanced concept, when varying the number of MED effects, the system sizing, the salt of the solutions, and other key parameters. The levelized cost of electricity (LCOE) has been calculated, showing that competitive solutions can be reached only when the system is at least medium to large scale. The lowest LCOE, at about 0.03 €/kWh, is achieved using potassium acetate salt and six MED effects while reheating the solutions. A similar analysis has been conducted when using the system in energy storage mode, where the two regenerated solutions are stored in reservoir tanks and the RED is operating for a few hours per day, supplying valuable peak power, resulting in a LCOE just below 0.10 €/kWh. A life-cycle assessment has been also carried out, showing that the case with the lowest environmental impact is the same as the one with the most attractive economic performance. Results indicate that the material manufacturing has the main impact; primarily the metallic parts of the MED. Overall, this study highlights the development efforts required in terms of both membrane performance and cost reduction, in order to make this technology cost effective in the future

On the Reduction of Power Consumption in Vortexing Unbaffled Bioslurry Reactors

Bioremediation of polluted soils via bioslurry reactors is an interesting option among those available nowadays, especially when recalcitrant pollutants are present. Vortexing unbaffled stirred tanks may be a valuable choice to this purpose as they were recently found to be more efficient than baffled vessels for solid suspension processes where mixing time is not a controlling factor. When operated at sufficiently high agitation speeds, the central vortex bottom reaches the impeller and air bubbles start to be distributed throughout the system, thus avoiding any sparger and related clogging issues. In the present work, a vortexing unbaffled stirred tank with solid loadings ranging from 2.5% w/w (weight of the solid/weight of the liquid) up to the very high 160% w/w was studied. Different turbine types including Rushton turbine, up- and down-pumping pitched blade turbines, and A310 were investigated. The minimum impeller speeds for complete particles' suspension (N-js) and system aeration (N-cr) along with the relevant power (P-js, P-cr) and specific power (per mass unit) consumptions (epsilon(js), epsilon(cr)) were assessed, in order to identify the geometrical configuration and operating condition providing the lowest power consumption. Results showed that the Rushton turbine and a solid concentration B of about 30% may be the most economically convenient arrangement to achieve system aeration and complete particles' suspension at the same time inside the reactor

Comparison of Agitators Performance for Particle Suspension in Top-Covered Unbaffled Vessels

Power savings is a problem of crucial importance nowadays. In process industry, suspension of solid particles into liquids is usually obtained by employing stirred tanks, which often are very power demanding. Notwithstanding tanks provided with baffles are traditionally adopted for this task, recent studies have shown that power reductions can be obtained in top-covered unbaffled vessels. In the present work experiments were carried out in a top-covered unbaffled vessel with a diameter T=0.19m and filled with distilled water and silica particles. Two different turbines were tested: a standard six-bladed Rushton Turbine (RT) and a 45\ub0 four bladed Pitched Blade Turbine (PBT). For the case of the PBT both the up-pumping (PBT-Up) and the downpumping (PBT-Down) operation mode were tested. Two different impeller sizes D (T/3 and T/2) and clearances C (T/3 and T/10) were investigated. The effects of particle size and concentration were also assessed. Investigations concern the assessment of the minimum impeller speed for complete suspension (Njs) along with the measurement of the relevant power consumption (Pjs) aiming at identifying the most efficient tank-turbine configuration among those investigated here. Results were also compared with corresponding ones pertaining to baffled tanks (obtained via correlations available in the literature). Results have shown that the RT with D=T/3 and C=T/3 and the PBT-Up with D=T/2 and C=T/10 appear to be the most convenient (least power demanding) options. Finally, a significant power saving with respect to the most efficient baffled configurations was observed thus confirming the convenience of operating solid-liquid suspensions in an unbaffled system for all those processes where the mixing time is not a limiting factor

Production of large-particle-size monodisperse latexes

The research program achieved two objectives: (1) it has refined and extended the experimental techniques for preparing monodisperse latexes in quantity on the ground up to a particle diameter of 10 microns; and (2) it has demonstrated that a microgravity environment can be used to grow monodisperse latexes to larger sizes, where the limitations in size have yet to be defined. The experimental development of the monodisperse latex reactor (MLR) and the seeded emulsion polymerizations carried out in the laboratory prototype of the flight hardware, as a function of the operational parameters is discussed. The emphasis is directed towards the measurement, interpretation, and modeling of the kinetics of seeded emulsion polymerization and successive seeded emulsion polymerization. The recipe development of seeded emulsion polymerization as a function of particle size is discussed. The equilibrium swelling of latex particles with monomers was investigated both theoretically and experimentally. Extensive studies are reported on both the type and concentration of initiators, surfactants, and inhibitors, which eventually led to the development of the flight recipes. The experimental results of the flight experiments are discussed, as well as the experimental development of inhibition of seeded emulsion polymerization in terms of time of inhibition and the effect of inhibitors on the kinetics of polymerization