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