Binary Vapor-Liquid Phase Equilibrium for Methane in Selected Heavy Normal Paraffins, Naphthenes, and Aromatics

An existing experimental apparatus was modified for the determination of bubble point pressures for binary mixtures of methane in paraffinic, naphthenic, and aromatic solvents at temperatures from 311 to 433 K and pressure to 113 bar. Precise bubble point data were obtained for methane binaries involving n-C??, n-C??, n-C??, n-C??, n-C??, cyclohexane, t-decalin, benzene, naphthalene, phenanthrene, and pyrene. The solvents n-C??, n-C??, n-C??, n-C??, n-C??, naphthalene, phenanthrene, and pyrene are solid at room temperature. Correlative efforts for methane + n-paraffins (C? and above) and methane + naphthenes and aromatics included: (1) Interaction parameters were determined for Soave-Redlich-Kwong (SRK) and Peng-Robinson (PR) equations of state using least squares regression of bubble point pressure data. (2) Several generalization schemes have been implemented for the SRK and PR interaction parameters in terms of pure hydrocarbon properties to extend the predictive capabilities of these equations to binary mixtures of methane + hydrocarbon solvents. (3) The new data and the data found in the literature were analyzed using the Krichevsky-Kasarnovsky model. This provided estimates of Henry's constants and infinite-dilution partial molar volumes of methane and demonstrated the internal consistency of the acquired data.Chemical Engineerin

Boron removal from saline water.

Although boron is an essential micronutrient for some plants, animals and humans, the range between deficiency and excess is narrow. The effects of excess boron on plants includes the reduction of root cell division, retarded shoot and root growth, inhibition of photosynthesis, deposition of lignin and suberin and decrease in leaf chlorophyll. A report by the World Health Organization (WHO) suggests a safe maximum level of boron daily intake of 13 mg/d an excessive level of boron can be toxic to and can causes serious diseases. There are several methods applied for boron removal from aqueous solutions and seawater. Among these methods, ion exchange, which is the most extensively method. Ion-exchange and adsorption are widely used techniques to remove metals and other solutes from aqueous solutions. This includes the removal of boron from reverse osmosis (RO) permeate in the process of seawater desalination. The use of boron-selective ion exchange resins based on macroporous polystyrene matrices with the active group N-methyl-D-glucamine (NMG) seems to still have the highest importance for the elimination of boron. Kinetics of adsorption or IEX is in many cases strongly influenced by diffusion resistance in particles of adsorbent. This resistance can be decreased by using smaller particles. Sorbents can be used as very fine particles which results in increase of the surface area and the process rate, considerably. Hybrid adsorption membrane filtration has gained the interest lately as it can be used for the removal of very small quantities of harmful substances from water. This thesis deals used hybrid system on both lab and pilot scale where a pilot plant was designed for the removal of boron. Boron separation combines two phenomena: i) sorption with fine sorbent particles and ii) membrane separation of B-loaded macromolecules/particles. The hybrid system includes two separation loops. Loop 1: Binding of boron (B) on Amberlite IRA743 resin (S), which is subsequently followed by separation of this (BS) complex from the water by means of semi-permeable microfiltration membrane. Here, pure water (W) is the main product whereas the complex (BS) passes to the second stage of separation. The effects of different parameters on boron removal using Amberlite IRA743 resin were investigated in this thesis. These parameters are, resin particle size, solution pH, temperature, contact time, initial boron concentration, resin concentration and the existence of different salts and ions like NaCl, Na2SO4 and MgCl2. The removal increased with increasing pH, temperature, contact time and resin dosage while it decreased with increasing initial boron concentration and resin particle size. For the microfiltration stage, three Polyvinylidene fluoride (PVDF) with different pore size have been used in this thesis. The effects of operational parameters like membrane pore size, transmembrane pressure, resin concentration and pH on permeate flux for hybrid adsorption-microfiltration were studied. The permeate flux increased with increasing the transmembrane pressure and pH but it decreased with increasing the resin concentration. The regeneration of loaded resin with boron was investigated. Hydrochloric acid (HCl) and sulfuric acid (H2SO4) at different concentrations have been used for the elution of boron from the saturated resin and then washing with sodium hydroxide (NaOH). There was an improvement in the boron removal after cycles of regeneration. The integrated adsorption-microfiltration was applied for boron removal from water and encouraging results were achieved

Design and Modeling of UHF Partial Discharge Sensors: FE-Based PD Signal Propagation in High Voltage Systems

The determination of whether high voltage (HV) devices suffer from high levels of partial dis charge (PD) has received significant attention to ascertain the safety of neighboring utilities and achieve economic satisfaction. Such HV devices include gas-insulated switchgear (GIS), power transformers, rotating electric machines, and power transmission lines. Albeit such capital assets are rarely damaged due to their high robustness, such devices can still experience significant degradation, primarily due to PD events. Therefore, monitoring high voltage systems against PD has become of paramount significance. This has contributed to developing a plethora of PD-based detection techniques, including acoustics, optical, electromagnetic (using Ultra-high frequency sensors and high-frequency current transformers), and chemical techniques. The recent advances in ultra-high frequency-based (UHF) techniques have led to the utilization of such techniques in PD detection for many high voltage devices like GIS, transformers, and power cables. This is attributed to the superior immunity and high sensitivity of UHF techniques in detecting, localizing, and classifying different PD defects. UHF detection was predominantly concerned with implementing antennas or sensors to detect PD activities and localizing PD defects based on the time-of-flight (ToF) or the time-difference-of-arrival (TDoA) in GIS and power transformers. The work done hitherto covered either simplified models of disconnecting parts inside GIS enclosures or addressed a single disconnecting part at a time. This work, on the other hand, analyzes EM waves due to multiple disconnecting parts simultaneously. First, this work utilizes CIGRE sensitivity verification recommendations to overcome the treeing issue associated with partial discharge and properly analyze EM waves inside two different GIS structures. A 145kV L-structured GIS model was implemented in COMSOL multi-physics, and EM wave propagation has been analyzed. Moreover, a 550kV Siemens π model GIS has also been implemented and analyzed. The obtained results have been compared with experimental results to verify the model’s accuracy. It has been shown that GIS systems are very complex structures for propagating electromagnetic waves due to the multiple barriers existing within such devices. Hence, many reflections and signal attenuation are experienced by electromagnetic waves. Then, a disk-cone (DISCONE) planar class of antennas has been optimized, implemented, and tested against partial discharge. A size-reduction technique, which utilizes the structural symmetry of the antenna, has also been proposed and discussed to reduce the cost of implementation and improve the antenna’s directivity. The experimental results largely agree with the simulation results verifying the modeling accuracy. A maximum gain of 6.25dBi has been achieved using the proposed antenna, and 47% size-reduction has been accomplished without significant performance degradation. After testing the antenna performance, the device has also been tested against PD activities within ceramic insulators and induction machines. The obtained results show that the antenna can be used to obtain different PD signatures, and hence, PD defect classification can be easily performed

Feasibility of the direct generation of hydrogen for fuel-cell-powered vehicles by on-board steam reforming of naphtha

A process flow sheet for the production of hydrogen to run a 50 kW fuel-cell-powered-vehicle by steam reforming of naphtha is presented. The major units in the flow sheet involve a desulfurization unit, a steam reformer, a low temperature (LT) shift reactor, a methanation reactor, and a membrane separator unit. The flow sheet is simulated using HYSYS (a steady state simulator) and the material and energy flows for each stream are obtained. For the peak load of 50 kW, it is found that 14 l/h naphtha is needed, which means that a 70 l fuel tank in the vehicle is sufficient for 5 h drive. The amount of water needed is not a critical factor, since it is generated in the fuel cell and quantities of water-makeup can be kept at the minimum level.\ud \ud Catalytic processes involved are briefly reviewed and commercial catalysts used are indicated. The amount of catalyst required in each reactive unit is computed by employing the design parameters (temperature, pressure, and space velocities) reported in the literature. In the desulfurization step, it is found that about 1.6 l of a bed of ZnO is capable of handling a stream of naphtha with 1500 ppm of sulfur for 45 h of continuous operation before regeneration or replacement of the bed becomes necessary. This, however, is based on operation at 10 atm. Operation at lower pressure level will increase the desulfurization catalyst requirements, maybe to a prohibitive level. Over the reformer Liquid-Hourly Space-Velocity range of 1–4 h−1, the amount of the supported nickel catalyst varies from 14 to 4 l, respectively. For the LT shift reactor the amount of catalyst required ranges from 4 to 60 l on going from 3×102 to 4×103 h−1 typical Gas-Hourly Space-Velocity. The catalyst here is CuO–ZnO supported on Al2O3. The last methanation step to remove traces of poisonous CO requires about 3.5 l of nickel supported by various oxides. To selectively separate hydrogen, it is suggested to use a palladium–silver membrane, which is reported to give ultra-pure hydrogen

A Review on Membrane Biofouling: Prediction, Characterization, and Mitigation

Water scarcity is an increasing problem on every continent, which instigated the search for novel ways to provide clean water suitable for human use; one such way is desalination. Desalination refers to the process of purifying salts and contaminants to produce water suitable for domestic and industrial applications. Due to the high costs and energy consumption associated with some desalination techniques, membrane-based technologies have emerged as a promising alternative water treatment, due to their high energy efficiency, operational simplicity, and lower cost. However, membrane fouling is a major challenge to membrane-based separation as it has detrimental effects on the membrane’s performance and integrity. Based on the type of accumulated foulants, fouling can be classified into particulate, organic, inorganic, and biofouling. Biofouling is considered the most problematic among the four fouling categories. Therefore, proper characterization and prediction of biofouling are essential for creating efficient control and mitigation strategies to minimize the damage associated with biofouling. Moreover, the use of artificial intelligence (AI) in predicting membrane fouling has garnered a great deal of attention due to its adaptive capability and prediction accuracy. This paper presents an overview of the membrane biofouling mechanisms, characterization techniques, and predictive methods with a focus on AI-based techniques, and mitigation strategies

Adsorption of -Dihydroxybenzene from Single, Binary and Ternary Aqueous Systems onto Activated Charcoal

The adsorption of para -dihydroxybenzene ( p -DHB) from aqueous multi-component systems onto activated charcoal was investigated. The study involved the adsorption of p -DHB from systems containing all combinations of p -DHB, phenol and 4-amino-1-naphthalene sulphonic acid sodium salt (ANSA) in aqueous solutions. Equilibrium isotherms were generated at three temperature values (30°C, 40°C and 55°C). As expected for exothermic physical adsorption, the adsorption of p -DHB from the single-component system and from the binary system containing ANSA decreased with increasing temperature. However, the adsorption of p -DHB from the binary system containing phenol increased with temperature. The effect of KCl and NaCl (at a concentration of 0.05 M) at 30°C was also investigated. The adsorption of p -DHB varied from one system to another. Both salts reduced the adsorption of p -DHB from the single and binary systems. The reduction in adsorption capacity (relative to the adsorption capacity in a salt-free system) attained only ca. 35% in the case of single-solute adsorption and ca. 20% and 33% from the binary systems containing p -DHB and phenol or ANSA, respectively. In contrast, the presence of KCl or NaCl had no appreciable effect on the adsorption of p -DHB from the ternary system

Stability limits and consolute critical conditions for liquid mixtures

<p>This work addresses the determination of stability limits and consolute critical conditions for multicomponent liquid mixtures. Using the NRTL model, thermodynamic stability and criticality criteria are implemented for ternary liquid mixtures to predict stability limit loci and critical composition at its specified temperature and pressure. The method is general and applicable for the prediction of spinodal curves and critical points for liquid–liquid-phase transitions in multicomponent liquid mixture using liquid–liquid equilibrium data even over a limited range of composition. Stability limits’ loci for 18 aqueous and 3 nonaqueous ternary liquid mixtures were used in validating the method. For ternary systems that were studied over the whole composition range including the critical zone, where experimental compositions at the critical point were available, the predicted results agree with the experimental measurements within 0.7 mol%.</p