Development of a Dynamic Modeling Approach to Simulate a Segmented Distillation Column for Flexible Operation

The need for flexible process equipment has increased over the past decade in the chemical industry. However, process equipment such as distillation columns have limitations that significantly restrict flexible operation. We investigate a segmented tray column designed to allow flexible operation. The design consists of radial trays connected at the downcomer of each tray. Each segment can be operated separately, but depending on the capacity of the feed stream, additional segments can be activated or deactivated. The connection between the trays aims to transfer liquid from one stationary segment to the adjacent inactive segment, thereby reducing the time required for the start-up process. In a case study on the separation of methanol and water, we perform dynamic simulations to assess the reduction in the start-up time of inactive segments. The results confirm the advantages over standard tray designs. The segmented distillation column is a step towards improving the flexibility of separation operations.

Effect of H2O2 Antiseptic on Dispersal of Cavitation-Induced Microdroplets

The persisting outbreak of SARS-CoV-2 has posed an enormous threat to global health. The sustained human-to-human transmission of SARS-CoV-2 via respiratory droplets makes the medical procedures around the perioral area vulnerable to the spread of the disease. Such procedures include the ultrasonic dental cleaning method, which occurs within the oral cavity and involves cavitation-induced sprays, thus increasing the risk of pathogen transmission via advection. To understand the associated health and safety risks for patients and clinicians, it is critical to understand the flow pattern of the spray cloud around the operating region, the size and velocity distribution of the emitted droplets, and the extent of fluid dispersion until ultimate deposit on surfaces or escape through air vents. In this work, the droplet size and velocity distributions of the spray emerging from the tip of a free-standing common ultrasonic dental cleaning device were characterized via high-speed imaging. Deionized water and 1.5% and 3% aqueous hydrogen peroxide (H2O2) solutions were used as working fluids, with the H2O2—an established oxidizing agent—intended to curb the survival of virus released in aerosols generated from dental procedures. The measurements reveal that the presence of H2O2 in the working fluid increases the mean droplet size and ejection velocity. Detailed computational fluid dynamic simulations with multiphase flow models reveal benefits of adding small amounts of H2O2 in the feed stream of the ultrasonic cleaner; this practice causes larger droplets with shorter residence times inside the clinic before settling down or escaping through air vents. The results suggest optimal benefits (in terms of fluid spread) of adding 1.5% H2O2 in the feed stream during dental procedures involving ultrasonic tools. The present findings are not specific to the COVID-19 pandemic but should also apply to future outbreaks caused by airborne droplet transmission.

Exergy Analysis of a Turbo Expander: Modeling and Simulation

Natural gas is a mixture that is widely used in the industries. Knowledge of its thermodynamic properties is essential for evaluating the process and equipment performance. This paper quantifies the energy that can be extracted from natural gas using a turbo expander. Natural gases of wide-ranging compositions collected from 6 different gas fields in Egypt were investigated based on energy and exergy analysis. The study was conducted using MATLAB. Numerous simulation runs were made by taking various typical feed compositions classified as lean and rich. The effects of increasing the amount of C1, C5 in the feed stream on the efficiency of energy utilization are presented. A validation analysis was performed. The results show similar trends and good agreements. It was concluded from the results that when the concentration of methane in the gas mixture increase, the exergetic efficiency decreases. The results also show that the values of thermodynamic properties depend on the relative amount of heavy components in the feed stream.

Modeling of Bimolecular Nitroxide Mediated Radical Polymerization of Styrene in Batch Reactor and Steady State Analysis of CSTR Reactor

Controlled radical polymerization (CRP) is a rapidly developing area in polymer science. Its versatility and ability to produce novel polymer structures are the main reasons which attract both academic and industrial interests. In particular, Nitroxide mediated Radical Polymerization (NMRP) is currently one of the three popular approaches in CRP. Polymeric materials synthesized by NMRP can be utilized for coatings, adhesives, lubricants, gels, thermoplastic and also for biomedical applications. Open literature shows an academic controversy over the kinetic mechanisms of NMRP and also over the kinetic reaction rate parameters. In this study, a kinetic mechanism describing the bimolecular NMRP was thoroughly discussed, reviewed and improved. In fact, two side reactions have been added to the most updated NMRP reaction scheme. Therefore, a kinetic model for a NMRP polymer reactor operating in batch and CSTR modes was developed based on a detailed reaction mechanism for thermal polymerization of styrene and also for bimolecular NMRP of styrene using benzoyl peroxide (BPO) as initiator and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as a radical controller. The kinetic model, consisting of a set of ordinary differential equations, was numerically integrated and validated with a set of experimental data obtained at temperature 120°C and [TEMPO]/[BPO] molar ratio 1.1. This model validation was done by means of a parameter estimation scheme to determine the "best" kinetic parameters. The model predictions were compared with data at 120 and 130°C for [TEMPO]/[BPO] molar ratios of 0.9, 1.1, 1.2, and 1.3. A good to very good agreement was obtained between the prediction and data. The non-linear behavior of the CSTR polymerization reactor was also analyzed using Matlab continuation program Matcont package. Typical hysteresis behavior, input and output multiplicities, as well as disjoint bifurcations were determined for this reactor. The bifurcation parameters selected are the coolant flow rate, feed stream temperature, residence time, initiator feed stream concentration and controller feed stream concentration. Bifurcation analyses reveal the stable and unstable operating regions of the reaction. Thus, the results obtained can be employed as a guide to develop a process control strategy for a better and safer operation of the NMRP polymerization reactors. Finally, a steady state optimization for the CSTR reactor was carried out in order to identify the optimal operating conditions of the NMRP process.

Modeling of Bimolecular Nitroxide Mediated Radical Polymerization of Styrene in Batch Reactor and Steady State Analysis of CSTR Reactor

Controlled radical polymerization (CRP) is a rapidly developing area in polymer science. Its versatility and ability to produce novel polymer structures are the main reasons which attract both academic and industrial interests. In particular, Nitroxide mediated Radical Polymerization (NMRP) is currently one of the three popular approaches in CRP. Polymeric materials synthesized by NMRP can be utilized for coatings, adhesives, lubricants, gels, thermoplastic and also for biomedical applications. Open literature shows an academic controversy over the kinetic mechanisms of NMRP and also over the kinetic reaction rate parameters. In this study, a kinetic mechanism describing the bimolecular NMRP was thoroughly discussed, reviewed and improved. In fact, two side reactions have been added to the most updated NMRP reaction scheme. Therefore, a kinetic model for a NMRP polymer reactor operating in batch and CSTR modes was developed based on a detailed reaction mechanism for thermal polymerization of styrene and also for bimolecular NMRP of styrene using benzoyl peroxide (BPO) as initiator and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as a radical controller. The kinetic model, consisting of a set of ordinary differential equations, was numerically integrated and validated with a set of experimental data obtained at temperature 120°C and [TEMPO]/[BPO] molar ratio 1.1. This model validation was done by means of a parameter estimation scheme to determine the "best" kinetic parameters. The model predictions were compared with data at 120 and 130°C for [TEMPO]/[BPO] molar ratios of 0.9, 1.1, 1.2, and 1.3. A good to very good agreement was obtained between the prediction and data. The non-linear behavior of the CSTR polymerization reactor was also analyzed using Matlab continuation program Matcont package. Typical hysteresis behavior, input and output multiplicities, as well as disjoint bifurcations were determined for this reactor. The bifurcation parameters selected are the coolant flow rate, feed stream temperature, residence time, initiator feed stream concentration and controller feed stream concentration. Bifurcation analyses reveal the stable and unstable operating regions of the reaction. Thus, the results obtained can be employed as a guide to develop a process control strategy for a better and safer operation of the NMRP polymerization reactors. Finally, a steady state optimization for the CSTR reactor was carried out in order to identify the optimal operating conditions of the NMRP process.

The Effect of Biogas Origin on the Electricity Production by Solid Oxide Fuel Cells

This work simulates electricity production in a Solid Oxide Fuel Cell (SOFC)-based power plant, fed by biogas of various compositions. Steam reforming of the gas feed stream is used to produce the required supply for the SOFC. Given the constraints of the feed stream compositions, resulting from the origin of biogas, i.e., by the biomass from which the biogas has been produced as well as by the operating conditions selected for its production, the overall plant performance is modelled in terms of energy and exergy. The model provides results on the efficiency, power output and thermal behavior of the system, thus presenting the potential to offer great advantages in generating electricity from biogas and reducing the environmental impact. This research study presents the efficiency of such a system in terms of energy and exergy, by considering several values of the operational parameters (extensions of reactions that take place in the apparatus, temperatures, feed stream compositions, etc.). It is found that moving towards a methane richer fuel, the energy and exergy efficiency can remain almost constant at high levels (around 70%), while in absolute value the electric energy can increase up to 35% according to the system’s needs. Therefore, under this prospect, the present research study reveals the usefulness of low content methane fuels, which through the optimization process can succeed identical energy management compared to high content methane fuels.

Validation of the Molar Flow Rates of Oil and Gas in Three-Phase Separators Using Aspen Hysys

A three-phase separator is the first vessel encountered by well fluids. The application of separators has been of great value to the oil and gas industry. In order to generate the gas phase envelope that is applicable to the study of reservoir fluid and the selection of optimum operating conditions of separators, this research utilizes a specified reservoir fluid stream to simulate a three-phase separator executed in Aspen HYSYS. Subsequently, a comparative study of the effects of specified inlet operating conditions on the output of gas and oil streams was carried out. The results show that changing the inlet pressure of the separator from 1000 to 8000 kPa reduces the gas outlet flow from 1213 to 908.6 kg mol/h, while it increases the liquid flow rate from 374 to 838.0 kg mole/h. By changing the temperature of the separator feed stream from 13 to 83 °C, the gas outlet stream was raised from 707.4 to 1111 kg mol/h, while the liquid flow rate dropped from 1037.0 to 646.1 kg mol/h. It was observed that the concentration of the outlet methane product is not affected by changing the flow rate of the feed stream at a specific pressure and temperature. Therefore, the thermodynamic property method is appropriate to simulate the separation of reservoir fluids which was achieved by selecting the Peng–Robinson (PR) model. The operating conditions of the separator were at 8000 kPa and 43 °C, which lies right on the dew point line. This is comparable to similar work on CHEMCAD which was in turn validated by plant data. Thus, the gas flow rate and the oil flow rate were dependent on pressure and temperature conditions of the plant.

Development of a continuous evaporation system for an API solution stream prior to crystallization

A bubble column was investigated as a method to achieve a desired and controllable rate of evaporation of a pharmaceutical solution in continuous processing mode. Applying a developed thermodynamic model to predict the rate of evaporation, all predicted values achieved accuracies within the bounds of instrumentation errors. The model accounted for the measured effect of reduced vapor pressure caused by dissolved solids as a function of their concentration. A general method to obtain accurate measurement of this effect is introduced and applied, improving the accuracy of model predictions. Predicting the rate of evaporation using the developed model, consistent and repeatable evaporation rates ranging from 0.7–6.9 g/min were achieved. Applying the column as a controllable evaporator, the concentration of a dilute feed stream was increased in a single equilibrium stage and coupled to a crystallizer. The configured system achieved a steady state of controllable operation over a duration of 5 hours

Reducing the Impacts of Biofouling in RO Membrane Systems through In Situ Low Fluence Irradiation Employing UVC-LEDs

Biofouling is a major concern for numerous reverse osmosis membrane systems. UV pretreatment of the feed stream showed promising results but is still not an established technology as it does not maintain a residual effect. By conducting accelerated biofouling experiments in this study, it was investigated whether low fluence UV in situ treatment of the feed using UVC light-emitting diodes (UVC-LEDs) has a lasting effect on the biofilm. The application of UVC-LEDs for biofouling control is a novel hybrid technology that has not been investigated, yet. It could be shown that a low fluence of 2 mJ∙cm−2 delays biofilm formation by more than 15% in lab-scale experiments. In addition, biofilms at the same feed channel pressure drop exhibited a more than 40% reduced hydraulic resistance. The delay is probably linked to the inactivation of cells in the feed stream, modified adsorption properties or an induced cell cycle arrest. The altered hydraulic resistance might be caused by a change in the microbial community, as well as reduced adenosine triphosphate levels per cells, possibly impacting quorum sensing and extracellular polymeric substances production. Due to the observed biofilm attributes, low fluence UV-LED in situ treatment of the feed stream seems to be a promising technology for biofouling control.