Two-stage Separation Process Research Articles

Recovery of Rare Metals from Superalloy Scraps by an Ultrasonic Leaching Method with a Two-Stage Separation Process

Superalloy scraps are deemed as potential unconventional sources of rare metals. In this study, an ultrasonic leaching method with a two-stage separation process was proposed. A series of Eh-pH diagrams for rare metals was constructed, and the results indicated that the leaching and separation process could be realized by adjusting the potential and pH values of leaching solutions. In the ultrasonic leaching process, results showed that the economic leaching percentages of Re, Ni, Co, Al, and Cr were 92.3%, 95.2%, 98.5%, 98.7%, and 97.5%, respectively. Compared with conventional leaching, ultrasonic leaching can improve the leaching percentages of rare metals by approximately 20%. In the two-stage separation process, the optimal recovery efficiencies of Al and Cr were 94.6% and 82.1% at a pH of 4.5, and Ni and Co were 99.5% and 98.3% at a pH of 7.5. With a two-stage precipitate process, rare metals can be efficiently recovered without generating any waste acid.

Coordination Cages Selectively Transport Molecular Cargoes Across Liquid Membranes.

Chemical purifications are critical processes across many industries, requiring 10–15% of humanity’s global energy budget. Coordination cages are able to catch and release guest molecules based upon their size and shape, providing a new technological basis for achieving chemical separation. Here, we show that aqueous solutions of FeII4L6 and CoII4L4 cages can be used as liquid membranes. Selective transport of complex hydrocarbons across these membranes enabled the separation of target compounds from mixtures under ambient conditions. The kinetics of cage-mediated cargo transport are governed by guest binding affinity. Using sequential transport across two consecutive membranes, target compounds were isolated from a mixture in a size-selective fashion. The selectivities of both cages thus enabled a two-stage separation process to isolate a single compound from a mixture of physicochemically similar molecules.

Rapid Separation and Precise Determination of Strontium Isotopic from Geological Samples with High Rubidium/Strontium Ratios

Abstract In the isotopic measurement of strontium (Sr) of geological samples with high rubidium (Rb)/Sr ratios, it is difficult to completely remove the isobaric interference of Rb on Sr isotopic analysis by a single separation and purification using traditional strong acid cation exchange resin. Actually, one purification procedure performed twice is necessary to eliminate the interference of 87Rb on the testing of 87Sr/86Sr. Although the purification procedure can ensure a good effect on the separation and purification of Sr, the process is tedious and time-consuming, which is not suitable for simultaneous separation and purification of Sr from large quantity of geological samples with high Rb/Sr ratios. In this study, the conventional two-stage separation process was optimized, and an experimental method for rapid separation of Sr from geological samples with high Rb/Sr ratios was established. In this method, the Sr solution after purified by AG50 resin was directly added to a new AG50 resin to purify Rb and Sr again. The whole separation process would be accomplished quickly and efficiently. The method combined with highly sensitive thermal ionization mass spectrometer (TIMS) technique was completely satisfied in high precision determination of 87Sr/86Sr isotope ratio in the samples with high Rb/Sr ratios. Through the application of the novel separation method with a large number of geological samples with high Rb/Sr ratios, it was proved that the experimental process was stable and reliable and showed crucial application value.

Techno-economic evaluation of helium recovery from natural gas; A comparison between inorganic and polymeric membrane technology

Natural gas produced at high pressure (50-70 bar) is the only industrial source of helium (He). A membrane separation process may offer a more efficient production system with smaller footprint and lower operational cost than conventional cryogenic system. Inorganic membranes with high mechanical strength are known to exhibit good stability at high pressure. In this work, two inorganic membranes, porous silica and carbon molecular sieve (CMS) were studied by simulation for their applicability in the He recovery process and compared against a Matrimid polymeric membrane. An in-house developed membrane simulation model (Chembrane) interfaced with Aspen HYSYS was used to simulate the membrane area and energy requirement for the He separation process. He was separated directly from a mixture containing methane (CH4) and 1-5 mole% He in the feed stream, and natural gas containing 1-5 mole% of He in a mixture of CH4 and N2. These streams were considered at 70 bar pressure and 25 °C. Single and two-stage membrane separation processes with and without recycle stream were simulated to achieve 97 mole % purity and 90% recovery of He. The simulation results showed that all three membranes can achieve required purity and recovery in a two-stage separation process. However, a recycle is required while using Matrimid membrane which adds cost and complexity to the system. The highest net present value (NPV) for silica, CMS, and Matrimid membrane was $M 2.5, 2, and 1.75 respectively when 5% He is present in feed gas and 15 years of plant life is considered.

Separation of metals from metal-rich particles of crushed waste printed circuit boards by low-pressure filtration

In recent years, recovery of metals from electronic waste (e-waste) within China has become increasingly important due to potential supply risk of strategic raw material and environmental concerns. Printed circuit boards (PCBs) contain lots of valuable metals together with plenty of hazardous materials, which are considered both an attractive secondary resource and an environmental contaminant. Pressure filtration is an effective and environmentally friendly method for separating and recycling comminuted PCBs. Present work is focused on the recovery of metals from PCBs by low-pressure filtration separation. A two-stage separation process was adopted to selectively recover Pb-Sn and Cu alloys at different temperatures. The results showed that the temperature and pressure had great influence on the recovery of metals in the separation process. After the two-stage separation process, the total recoveries of Pb, Sn, Cu and Zn were 79.96%, 89.91%, 88.80% and 68.57% respectively, when the temperature is 1350 °C and the pressure is 0.30 MPa. This is a high-efficiency, short-flow, clean-production, and environmental-friendliness that can improve the recovery of metals and realize the reuse of waste resources.

Optimal activated carbon for separation of CO2 from (H2\u2009+\u2009CO2) gas mixture

Seven types of activated carbon were used to investigate the effect of their structure on separation of CO2 from (H2 + CO2) gas mixture by the adsorption method at ambient temperature and higher pressures. The results showed that the limiting factors for separation of CO2 from 53.6 mol% H2 + 46.4 mol% CO2 mixture and from 85.1 mol% H2 + 14.9 mol% CO2 mixture were different at 20 °C and about 2 MPa. The best separation result could be achieved when the pore diameter of the activated carbon ranged from 0.77 to 1.20 nm, and the median particle size was about 2.07 µm for 53.6 mol% H2 + 46.4 mol% CO2 mixture and 1.41 µm for 85.1 mol% H2 + 14.9 mol% CO2 mixture. The effect of specific area and pore diameter of activated carbon on separation CO2 from 53.6 mol% H2 + 46.4 mol% CO2 mixture was more significant than that from 85.1 mol% H2 + 14.9 mol% CO2 mixture. CO2 in the gas phase can be decreased from 46.4 mol% to 2.3 mol%–4.3 mol% with a two-stage separation process.

Development of the imitation model of the two-stage separation process of oil

In accordance with the law of preservation of the amount of substance, an imitation model for the process of two-stage oil separation has been developed. The creation of this model took into account the features of the operating mode of the horizontally placed separators B-1 and B-2 of the first and second stages of separation. The simulation mathematical model after the identification of parameters was investigated by a numerical method that takes into account the effect of perturbations on the separation process, which is a consequence of the action of a number of physical quantities from the environment on the object. Automated control systems that operate on the principle of negative feedback were used to stabilize the main technological parameters of oil separation. But since the deviation of the regulated quantities from their given values is small, this allowed linearizing the nonlinear model of the two-stage separation process. After studying the simulation model by a numerical method, it is established that the mathematical model of the installation of two-stage separation can be used for the synthesis of effective control systems of the two-stage separation process and the creation of mathematical models in terms of “input-output”. The obtained numerical and graphical result in the form of functional dependencies allows us to establish the relationship of technological parameters, in other words, the change of the value of the parameters at the second stage of separation will depend on the first one and vice versa. Thus, the applied aspect of using the obtained scientific result is the possibility of improving the typical technological process of oil separation.

Comparative feasibility study of CO2 capture in hollowfiber membrane processes based on process models and heat exchanger analysis

Carbon dioxide capture based on membrane separation process is one of the most promising methods to reduce greenhouse gases emissions. Many studies concerning economic competitiveness of membrane separation processes have been conducted. Heat exchangers can be effectively used to reduce the total energy consumption in the membrane separation process. The two-stage membrane separation processes considered in this work include heat exchangers with H2O sweep. The necessity of this work arose from the need to apply the heat exchanger network analysis in order to identify the optimal process configuration based on the process models. Typical multicomponent separation models for the counter-current flow pattern using hollowfiber membranes are validated with experimental data. Effects of the pressure ratio and membrane area to achieve a target CO2 purity (90%) and recovery (90%) are investigated. Energy analysis including heat recovery and utility power are performed using pinch technology. The results show that significant amount of total energy (1.31MJ/kg CO2) can be reduced by introducing heat exchangers compared to the two-stage separation process without heat exchangers.

Experiment on the separation of tail gases of ammonia plant via continuous hydrates formation with TBAB

We used hydrate separation method in this paper to recover H2 and N2 from tail gases of ammonia plant in the presence of tetra-n-butylammonium bromide (TBAB). The formation condition of H2/N2/CH4/TBAB hydrates was measured by pressure search method. Then the continuous separation of H2/N2/CH4 via hydrates formation was conducted in the presence of TBAB, and a two-stage separation process was proposed to increase the recovery of H2 and N2. The influences of experimental pressure, temperature and gas flow on the separation results were investigated. The results show that the total concentration of H2 and N2 in the unhydrated gas (recovered gas) is 95.28 mol%, and the total recovery of H2 and N2 is more than 90%. This work supplies the preliminary ideas and fundamental data for the industrial application of hydrate separation method.

Isothermal enriching and separation of perovskite phase from CaO–TiO2–SiO2–Al2O3–MgO melt by centrifugal force

A new approach to isothermal enriching combined with separating perovskite phase from CaO–TiO2–SiO2–Al2O3–MgO melt by centrifugal force was investigated. Using a two-stage centrifugal separation process, the recovery ratio of Ti in the second concentrate was 99·34% and the tailings were 0·66%, thus demonstrating excellent Ti separation. These materials can be considered as suitable raw materials for titanium white and cement respectively.

Coupling dynamic simulation and interactive multiobjective optimization for complex problems: An APROS-NIMBUS case study

Dynamic process simulators for plant-wide process simulation and multiobjective optimization tools can be used by industries as a means to cut costs and enhance profitability. Specifically, dynamic process simulators are useful in the process plant design phase, as they provide several benefits such as savings in time and costs. On the other hand, multiobjective optimization tools are useful in obtaining the best possible process designs when multiple conflicting objectives are to be optimized simultaneously. Here we concentrate on interactive multiobjective optimization. When multiobjective optimization methods are used in process design, they need an access to dynamic process simulators, hence it is desirable for them to coexist on the same software platform. However, such a co-existence is not common. Hence, users need to couple multiobjective optimization software and simulators, which may not be trivial. In this paper, we consider APROS, a dynamic process simulator and couple it with IND-NIMBUS, an interactive multiobjective optimization software. Specifically, we: (a) study the coupling of interactive multiobjective optimization with a dynamic process simulator; (b) bring out the importance of utilizing interactive multiobjective optimization; (c) propose an augmented interactive multiobjective optimization algorithm; and (d) apply an APROS-NIMBUS coupling for solving a dynamic optimization problem in a two-stage separation process.

Experiment on the Separation of Air-Mixed Coal Bed Methane in THF Solution by Hydrate Formation

Because of the technology limitation and safety requirement, a large amount of air-mixed coal bed methane is released directly to the atmosphere. It leads to severe waste of resources and exacerbates the greenhouse effect. This work tries to alleviate this problem by separating CH4 from a mixture of CH4 and N2 via hydrate separation method. Several experiments were systematically carried out in 6 mol % tetrahydrofuran (THF) solution to separate CH4/N2 gas mixtures containing 4.90 to 71.23 mol % CH4. The results that THF can significantly reduce the formation pressure of CH4–N2 hydrate materialize the possibility of separating CH4 and N2 using hydrate separation technology in industrial scale. CH4 can be separated effectively from CH4/N2 mixture and concentrated in hydrate phase with the presence of THF. The recovery of CH4 ranges from 34.06% to 58.16% and the separation factor is between 2.29 and 5.17. A two-stage separation process of 46.28 mol % CH4/53.72 mol % N2 with recycle is designed to increase th...

Purification of the two major proteins from whey concentrate using a cation‐exchange selective adsorption process

The packed-bed adsorption and elution of aqueous solutions of whey concentrate powders were investigated at pH 3.7 using a 5-mL SP Sepharose FF column to separate and isolate two major proteins namely, alpha-lactalbumin (ALA) and beta-lactoglobulin (BLG) from these solutions. ALA displaced and eluted BLG from the column in a pure form. Pure ALA could then be eluted with good recovery. A novel consecutive two-stage separation process was developed to separate ALA and BLG from whey concentrate mixtures. Almost all of the BLG in the feed was recovered, with 78% being recovered at 95% purity and a further 20% at 86% purity. In addition, 67% of ALA was recovered, 48% at 54% purity and 19% at 60% purity.

Application of Electrostatic Separation to the Recycling of Plastic Wastes: Separation of PVC, PET, and ABS

Plastics are widely used in everyday life as a useful material, and thus their consumption is growing at a rate of about 5% per year in Korea. However, the constant generation of plastic wastes and their disposal generates environmental problems along with economic loss. In particular, mixed waste plastics are difficult to recycle because of their inferior characteristics. A laboratory-scale triboelectrostatic separator unit has been designed and assembled for this study. On the basis of the control of electrostatic charge, the separation of three kinds of mixed plastics, polyvinyl chloride (PVC), poly(ethylene terephthalate) (PET), and acrylonitrile-butadiene-styrene (ABS), in a range of similar gravities has been performed through a two-stage separation process. Polypropylene (PP) and high-impact polystyrene (HIPS) were found to be the most effective materials for a tribo-charger in the separation of PVC, PET, and ABS. The charge-to-mass ratio (nC/g) of plastics increased with increasing air velocity in the tribo charger. In the first stage, using the PP cyclone charger, the separation efficiency of particles considerably depended on the air velocity (10 m/s), the relative humidity (< 30%), the electrode potential (> 20 kV), and the splitter position (+2 cm from the center) in the triboelelctrostatic separator unit. At this time, a PVC grade of 99.40% and a recovery of 98.10% have successfully been achieved. In the second stage, using the HIPS cyclone charger, a PET grade of 97.80% and a recovery of 95.12% could be obtained under conditions of 10 m/s, over 25 kV, a central splitter position, and less than 40% relative humidity. In order to obtain 99.9% PVC grade and 99.3% PET grade, their recoveries should be sacrificed by 20.9% and 27%, respectively, with moving the splitter from the center to a (+)6 cm position.

摩擦帯電選別とエアテーブル選別による ＰＶＣ選別プロセスの開発

In 2003, 2.16 million tons of polyvinyl chloride (PVC) have been produced in Japan, i.e. the third large proportion of plastic production. However, only 20% of PVC wastes have been recycled, while the rest was disposed or incinerated. In order to improve the PVC recycling rate, a two-stage separation process that combines the triboelectric separation and the air tabling has been designed. The developed process is able to sort PVC from other types of plastics. The efficiency of the process was investigated for two three-component plastic mixtures, i.e. (1) ABS (acrylonitrile-butadiene-styrene), PP (polypropylene) and PVC, which are used in production of home electric appliances or automobiles; and (2) PET (polyethylene terephthalate), PP and PVC, which are utilized in production of plastic containers or everyday products. In order to sort the ABS-PP-PVC mixture, the triboelectric separator was employed in the first stage of process to collect the ABS flakes as positively charged fraction. The negatively charged fraction of PP and PVC was then separated by means of the air table by taking advantages of differences in density. Hence, at the end of the process, the collected PVC fraction had a grade and a recovery of 90.2% and 78.0%, respectively. Regarding the separation of the PET-PP-PVC mixture, the air table was used in the first stage to collect the PP flakes as a low-density fraction. Then, the triboelectric separator was employed in the second stage to recover 89.0% of PVC with a grade of 93.7%.

Hydrogen separation using electrochemical method

Hydrogen is separated from a hydrogen/nitrogen/carbon dioxide mixture by an electrochemical separation method. By applying a direct current to a proton-conducting membrane, hydrogen can be electrochemically dissociated on the platinum catalyst of the anode, transported across the hydrated cation exchange membrane, and then recovered on the catalytic cathode. The operating principles and advantages of the electrochemical hydrogen separation method are described. The effects of temperature and pressure are examined and the optimum operating conditions are determined. Increase in cell temperature enhances the purity of hydrogen and the power efficiency. The pressure of the feeding gas increases both the performance and the amount of hydrogen product, but decreases the purity of the hydrogen because of the increasing permeation flux of impurities, i.e., nitrogen and carbon dioxide. High purity, (99.72%) hydrogen can be achieved from a low purity (30%) feed via a two-stage separation process at 700 mA cm −2 .

The use of biosurfactants in flotation: application for the removal of metal ions

The removal of zinc and chromium ions from aqueous solutions was investigated in the present study by the application of a two-stage separation process, termed sorptive flotation. The first stage consists of the metal ions sorption onto an appropriate sorbent material, followed by successive flotation as the second stage. The sorbent material was either laboratory prepared goethite, or in situ generated ferric hydroxide. The biologically produced surface active agents Surfactin-105 and Lichenysin-A, were applied as flotation collectors for the separation of the metal-loaded sorbents. The main studied parameters were the concentrations of sorbent materials, as well as of biosurfactants. Under the application of optimised conditions better floatabilities of metal-laden sorbents were obtained, when using the biosurfactants in comparison with the application of conventional (chemically produced) surfactants (sodium dodecyl sulphate or dodecylamine) examined under similar conditions.

Blind source separation by sparse decomposition in a signal dictionary.

The blind source separation problem is to extract the underlying source signals from a set of linear mixtures, where the mixing matrix is unknown. This situation is common in acoustics, radio, medical signal and image processing, hyperspectral imaging, and other areas. We suggest a two-stage separation process: a priori selection of a possibly overcomplete signal dictionary (for instance, a wavelet frame or a learned dictionary) in which the sources are assumed to be sparsely representable, followed by unmixing the sources by exploiting the their sparse representability. We consider the general case of more sources than mixtures, but also derive a more efficient algorithm in the case of a nonovercomplete dictionary and an equal numbers of sources and mixtures. Experiments with artificial signals and musical sounds demonstrate significantly better separation than other known techniques.

Study on the feasibility of obtaining highly enriched Carbon-13 in one- and two- stage modes of laser separation process

The feasibility of obtaining highly enriched (13C & 80%) carbon-13 by isotope-selective IR multiphoton dissociation (MPD) of Freon 22 (CF2HCl) molecules in one- and two-stage modes of the process in an apparatus with the intracavity arrangement of the separation reactor, which resembled current technological facilities in its basic characteristics, was studied. The one-stage separation scheme was realized using the selective MPD of Freon 22 by which13C is concentrated in the dissociation product tetrafluoroethylene (C2F4). Carbon-13 concentrations in the product and MPD yields were measured depending on the laser radiation frequency and Freon 22 and bath gas (nitrogen) pressure. At the chosen irradiation geometry and a laser pulse repetition rate of 30 Hz,13C concentrations of 83 and 89% in the final product with the production rate of ∼36 and ∼7 mg13C/h were attained. The two-stage separation scheme was furnished on the basis of isotopically selective dissociation of the intermediate product CF2HI enriched in13C by its buildup process upon irradiation of a CF2HCl mixture with HI. The final product in this case was CF2H2 having a13C concentration of 98 ± 1.5%. The production rate of the two-stage laser separation process was ∼22 mg13C/h.

Statistical representation of generalized distribution data for float-sink coal-cleaning devices: Baum jigs, Batac jigs, Dynawhirlpools

In an earlier paper (1978), Gottfried presented a method for combining distribution data for float-sink coal-cleaning devices into a single generalized distribution curve which, for a given device and feed size, is independent of specific gravity of separation. A non-linear, exponential-type equation was utilized to represent the generalized distribution curve, along with the corresponding generalized probable error. Distribution data for six common coal-cleaning devices have previously been treated by this method. This paper is an extension of two previous studies (Gottfried, 1978, 1980). The method described above is applied to three different float-sink coal-cleaning devices: Baum jig (replacing previously reported results), Batac jig and Dynawhirlpool separator. Results for the Baum jig and Batac jig reflect a two-stage separation process, with a set of generalized distribution curves obtained for each stage and another set for the overall separation. Several different feed size fractions are given for each vessel.