Volume 19, Issue 3

Spontaneous condensation occurs due to high steam speeds, leading to droplets in the stream that not only decrease performance but also hazard the security of the nozzle. This study aims to predict the position and size of suitable injected water droplets due to reduced losses due to liquid mass fraction. Firstly, the model of steam flow has been confirmed by experimental data using the Eulerian–Eulerian approach in Moore’s nozzle B. Then, the flow turbulence caused by phase change is modelled by k – w sst model. Then, the injection has applied in three sizes (coarse, medium, and fine) at four different positions of the nozzle and has analysed, which according to the findings of fine droplet size, has led to an enhancement in Mach number and on the other hand, injection in nucleation zone has resulted in a 7 % and 3 % reduction in wetness losses for the radius of coarse and fine droplets, respectively. It is predicted that the nucleation rate will decrease the smaller the injected droplets are in the nucleation region. Injection with a number droplet of 1.015 × 10 18 and a radius of 0.013 (μm) in the nucleation zone of 10 mm after the throat increased by 4.5 % of Mach number.

Gas sweetening with an aqueous solution of diethanolamine is a crucial and common process in natural gas processing. However, the process, particularly in the solvent regeneration section, consumes a substantial amount of energy, significantly escalating the cost of gas. This paper presents a simulation and optimization of an existing natural gas refinery plant using a lean vapor compression method. The simulation results indicate that the current process requires 2.73 GJ/t acid gas for solvent regeneration, with exergy destruction of 14,120.59 kW in the solvent regeneration section. The total annualized cost for the current process is 11.68 M$. A modified scheme is proposed to address the issue of high energy consumption and the associated costs. The proposed scheme demonstrates significant improvements in the aforementioned parameters. Specifically, energy for solvent regeneration, exergy destruction in the solvent regeneration section, total annualized cost, and cost of gas are reduced by 16.12 %, 25.04 %, 20.97 %, and 20 % compared to the current process, respectively. These improvements enhance the thermoeconomic indexes, making the proposed scheme a viable and cost-effective alternative to the current process.

In the current essay, the numerical investigation of heat transfer in an exchanger containing nanofluid with Cu nanoparticles in the presence of a new inserter is carried out. The equations governing the turbulent fluid flow have been solved utilizing single-phase models with the aid of the finite volume method in ANSYS-FLUENT software using the k-ε turbulence model for the Re number ranging from 4000 to 8000. Furthermore, the influence of Reynolds number, nanoparticle volume fraction, and geometric characteristics of turbulator on the friction factor and Nusselt number have been scrutinized. Outcomes reveal that the newly introduced inserter performs well and increases the Nusselt number by roughly 34–54 times and the friction coefficient by approximately 1.8–3.2 times compared to the smooth tube. It is also observed that a 2 % increase in the nanoparticles volume fraction has resulted in a rise in the Nusselt number by around 92 %. To attain the optimal performance of the presented turbulator, the longitudinal distance between the inserters is recommended as S/D = 5.27, for which Performance evaluation criteria values in the range of 3.01–9.23 in the Reynolds range under investigation are acquired.

This work presents a superstructure for maximizing the annual profit of biodiesel production with Advanced Interactive Multidimensional Modeling System (AIMMS). The novelty features are the combination of pinch-based heat integration with a wide range of biodiesel feedstocks and the application of superstructure to evaluate the effect of uncertainties on the optimized design. The case study is a pilot refinery with the infeed capacity of 8000 tonnes feedstock per year. The biodiesel production route from tallow with reactive distillation technology and a heterogeneous acid catalyst has the highest total annual profit of 3.5 million USDs. The heating and cooling utilities can be reduced by 30 % with the heat integration. The result from the sensitivity analysis shows that the biodiesel and feedstock prices, and the production capacity have the most pronounced effects. From technical assessment, the reactive distillation process is the best choice for biodiesel production from different feedstocks.

Performance and robustness are essential characteristics for the application of unstable time-delayed systems. As tasks become more complex, traditional control methods cannot meet such demands for performance and robustness. The present work aims to develop fractional order-based controllers for enhanced Smith predictor-based unstable first-order plus time-delayed systems (FOPTD) with improved performance and robustness. In the current work, fractional order controllers using a Genetic Algorithm (GA) are designed with enhanced SP (Smith Predictor) structure to control unstable first-order time-delayed processes to improve performance. Furthermore, in the feedback path a fractional order (FO) filter is used to further improve robustness and performance. A systematic methodology is proposed for obtaining the optimum fractional order filter parameters based on the minimization of Integral Absolute Error (IAE). The recommended approach is beneficial to balance the necessary tradeoff between performance and robustness. Also, the proposed method provides flexibility in tuning the degree of freedom by adding a fractional order integrator, thus leading to robust performance. The efficacy of the recommended controller is analyzed by simulating numerical examples from the literature. The proposed controller provides enhanced performance and robustness compared to the literature.

The kinetic study on sophorolipids (SLs) production by Candida catenulata from glucose, raw sunflower soapstock was investigated at different initial concentrations ranging from 0 to 100 g L −1 . The Monod model with a maximum specific growth rate ( μ max ) of 0.0167 h −1 and half-saturation coefficient ( K S ) of 6.91 g L −1 best described the cell growth kinetics of C. catenulata on glucose. The best-fitted constants of the Monod model for raw sunflower soapstock were μ max  = 0.0157 h −1 and K S  = 16.01 g L −1 . Determination of Luedeking-Piret constants indicated SLs mainly produced as an associated growth product in the systems. Dynamic features of the fermentation were modeled using the obtained constants and results showed the prediction power of the developed model in describing the behavior of the process. Also, a modified kinetic model was developed for the dynamic modeling of the dual carbon sources system.

Transient responses of reaction–desorption process were predicted from mathematical solutions of modeling equations for CSTR (continuously stirred tank reactor) containing core–shell adsorbent particles. Analytical solutions on the core–shell particles were derived for core–shell spherical, cylindrical, and slab-type morphologies, assuming inert-cores. Unlike continuous adsorber, CSTRs for reaction–desorption process containing spherical particles exhibited the slowest reduction rate of concentration of adsorbate, because the amount of adsorbed component on the particles is the largest among three kinds of particle shapes. Factors affecting the transient concentration in bulk medium of reaction–desorption process were investigated by adjusting inert-core thickness, inlet flow rate, initial concentration of reactant in inflow stream, amount of adsorbent, and Thiele modulus. Concentration profile inside the particles as well as average intra-particle concentration could be also predicted for comparison with bulk concentration of CSTR. For non-linear isotherm and non-linear reaction kinetics, concentration of active component could be predicted by solving non-linear coupled differential equation using finite element method. For connected CSTRs in series, systems of reaction-diffusion equations were solved by finite element method to study the effect of number of connected reactors. When the number of reactors was sufficiently large, the reactor system could be approximated to fixed bed reactor for reaction–desorption process.

A mathematical model was constructed to estimate the performance of an MFI-membrane reactor used for Fischer–Tropsch synthesis to produce a mixture of liquid hydrocarbons. In order to accurately evaluate the reactor’s performance a parametric study was performed. Under certain operational conditions, such as the total initial pressure in the reaction zone (1–4 MPa) and the hydrogen/carbon monoxide ratio (H 2 /CO: 1 to 2) on the performance of the studied reactor. The selectivity (productivity) of the hydrocarbon products ( S i ), the quantity of hydrocarbons permiated ( θ i ) and the separation factors of each space ( α i ) were predicted. With increasing pressure, it is observed that θ CO and θ H 2 ${\theta }_{{H}_{2}}$ are decreasing from 0.62 to 0.45 and from 0.55 to 0.49 respectively. However, as the H 2 /CO ratio rises, this measurement shows a slight increase. Aside from, the separation factors of the majority of the current species are unaffected by the H 2 /CO ratio increasing, while the separation factors of carbon monoxide and hydrogen are increasing. Similarly the selectivity of water, methane, carbon dioxide and ethane increases with increasing H 2 /CO ratio. Based on these findings it is revealed that the membrane can enable permeability for all species present in the products mixture with varying separation factors, and that the ability to separate species other than water from the reaction side is essentially non-existent.

The geometrical and hydraulic parameters have a great impact on the mass transfer characteristics of annular centrifugal contactors. The objective of this study is to evaluate the mass transfer performance of a single annular centrifugal contactor by applying the computational fluid dynamics informed compartment modelling approach. In the study, a steady state compartment model of an annular centrifugal contactor is developed in gProms general purpose process modeller by using the hydrodynamic parameters obtained from computational fluid dynamics simulations performed in OpenFOAM with the GEneralised Multifluid Modelling Approach (GEMMA). The mass transfer rate predicted by the developed compartment model is compared with data obtained from uranium extraction with Tributyl Phosphate experiments performed with a laboratory-scale annular centrifugal contactor. Uranium concentrations in the organic and aqueous outlets and the mass transfer rate evaluated by the developed compartmented contactor model are in good agreement with the experimental data. The results reveal that the use of a hydrodynamic-informed compartment modelling approach raises the possibility of designing full-scale annular centrifugal contactors without the need for detailed computational fluid dynamics simulations and the prediction of mass transfer performance of the whole system from laboratory scale experiments.

One of the most popular methods of fruit juice preservation is concentration since it offers a variety of advantages, like decreased volume, weight, packing, simpler transportation and handling, and a longer shelf life. The present paper studied the evaporation of fruit juice in single- and triple-effect evaporators using Aspen HYSYS software. The amount of juice was 3000 kg/h, and its concentration was raised from 10 to 50 °Brix. Four evaporator layouts were estimated and optimized: single-effect, modified single-effect, forward triple-effect, and triple-effect in parallel. It is a study of the effect of the temperature of saturated steam (120–300 °C) used to concentrate the juice and the pressure of the product (15–50 kPa) on the mass flow rate of steam required, economy, and overall heat transfer coefficient times area (UA) of the evaporator. The best operating conditions for each type of evaporation system were 15 kPa of the product’s pressure for all types of evaporators, 192, 240, 182, and 210 °C of the single-effect, modified single-effect, forward triple-effect, and parallel triple-effect, respectively. These operating conditions are equivalent to the steam required, economy, UA, and steam cost as follows: for each type, they were (3075, 338.4, 1224, and 1100 kg/h), (0.78, 7.1, 1.96, and 2.15), (40,182, 74,505, 539,987, 152,173 kJ/°C h), and (12.68 × 10 3 , 12.76 × 10 3 , 12.65 × 10 3 , and 12.73 × 10 3  $/h), respectively.