Band 18, Heft 6

In this paper, proportional-integral-derivative (PID) controllers are tuned for unstable first-order plus dead time (UFOPDT) systems. Genetic algorithm (GA) is used to find the parameters of the PID controller for UFOPDT systems under the constraint of robustness measure. By curve fitting, the controller parameters are expressed as the functions of the UFOPDT model parameters. Two tuning formulas which consider robustness and the tradeoff between disturbance rejection and robustness of the closed-loop system are proposed. The proposed tuning formulas extend the application range of the existing methods and simulation results show that the tuned PID controllers can achieve good performance for UFOPDT systems.

Concerning global warming, an energy-efficient power source must produce low or no pollutant emissions and provide an unlimited fuel supply. Proton Exchange Membrane fuel cell (PEMFC) is an electrochemical device that transforms chemical energy into electrical energy. The performance and durability of PEM fuel cells are affected by voltage reversals and fuel starvation. Oxygen Excess Ratio (OER) is a crucial factor in controlling the fuel starvation of the PEMFC system. First, this work identified the PEMFC as an integer order and fractional-order first order plus time delay models using the predictor error method and Grunwald–Letnikov simulation method based on a trust-region-reflect algorithm, respectively. Fractional order models more accurately represented the PEM fuel cell system dynamics. Then, robust fractional filters cascaded with PID controllers based on the Internal Model Control scheme (IMC) are designed for identified integer and fractional order models to regulate the OER by compressor voltage manipulation. The genetic Algorithm (GA) optimization technique is used to find the optimal fractional filter tuning parameters. The proposed controller’s performance regarding Integral Absolute Error (IAE) and Total Variance (TV) is analyzed. Furthermore, the robustness of a perturbed plant and fragility with perturbed controllers are elucidated. The results show that a fractional filter cascaded with fractional order PID controller improves the performance compared to a fractional filter cascaded with integer order PID controllers.

This paper suggests a novel framework to retrieve the squandered heat of the Naphtha Hydrotreating Unit of the petrochemical plants. In this idea, the distillation tower’s output of the hydrotreating naphtha unit of the plant is employed as the working fluid to run an organic Rankine cycle with benzene. The procedure is evaluated comprehensively from energy, economic and exergetic point of view using Aspen Haysys software. An advanced case study, including sensitivity analysis, is provided for the Bouali petrochemical plant in Iran to realistically indicate the performance of the suggested configuration. The air cooler in the distillation unit of the aforementioned plant removes (squanders) about 3418 kW of energy, which an organic Rankine cycle can recover. Based on the findings, the exergetic and thermal efficiency of the suggested cycle is 82.53 % and 13.28 %, respectively, with a 1,3620kWh/day rate of energy production. According to the exergetic analysis, the ORC turbine has the highest exergy destruction rate of about 178.76 kW. Also, using the distillation tower squander heat as the heat source to the organic Rankine cycle leads to the least exergy destruction rate. Besides, the output exergy ratio of the whole integrated system to its input is 0.907. The suggested integrated system reduces the total energy consumption from 0.4 to 0.29 GJ E /ton Feed with a total investment cost of 11.97 M$, in which the turbines have the highest portion of about 11.2 M$. Hence, the suggested plan’s total income is around 31.94 M$/year.

The present study performs a three-dimensional CFD analysis to investigate the hydrodynamic and thermal properties of annular finned tubes in a heat exchange system. All computations are performed in the turbulent flow regime (4330 ≤  Re  ≤ 8790), and the Transition SST model is applied for turbulence modelling. The impact of Prandtl number (0.7 ≤  Pr  ≤ 50) on the various parameters, such as the heat transfer coefficient, heat transfer rate, and pressure drop, are considered. The results indicate that the thermo-hydraulic behaviour is significantly affected by incrementing both Reynolds and Prandtl numbers. The fin’s surface temperature distribution is examined to get a better insight into its thermal performance, and it is observed that the rear portion of the fin contributes the least to heat transfer. Other important parameters like the fin efficiency and Colburn heat transfer factor are found to significantly impact the performance of the heat exchange system for the above range of settings. The velocity contours show the horseshoe vortex formation near the fin-tube junction, and the channelling effect is observed between consecutive tubes. Different fluids are compared based on the j / f factor for enhanced heat transfer at the minimum possible flow resistance.

The current investigation proposes an efficient process to produce methanol through the natural gas vapor reforming and direct hydrogenating of CO 2 that reduces CO 2 emission. The proposed process includes methanol synthesis in the catalytic reactor with an injection of carbon dioxide recovered from the plant’s flue and separation of methanol by distillation. An Aspen HYSYS code analyzes the proposed plant to assess the energy, exergy, economic, and environmental performances. Also, the effect of captured CO 2 flow on the methanol production, carbon efficiency, stoichiometric number of synthesized gas, and reboiler and condenser duties are investigated as a sensitivity analysis. The results indicate that the methanol production rate of 82,040 kg/h provides carbon, energy and exergy efficiencies of 85 %, 77.26 % and 77.32 %, which are higher than the similar proposed plants. Regarding exergy analysis, the total exergy destruction rate is about 238,468.21 kW, in which the reforming and burner sections contribute to the highest portions of about 47 % and 30 %. The global warming potential of the process is obtained at about 0.26  k g C O 2 , e q / k g M e O H ${\mathrm{k}\mathrm{g}}_{{\mathrm{C}\mathrm{O}}_{2,\mathrm{e}\mathrm{q}}}/{\mathrm{k}\mathrm{g}}_{\mathrm{M}\mathrm{e}\mathrm{O}\mathrm{H}}$ , which is reduced by captured CO 2 . The annual costs of investment and income are about 416,772,399 $ and 236,292,429 $, yielding 1.72 years payback period.

Hydrogels are possible materials that could be useful in medication delivery systems. Diverse release mechanisms are used when drug molecules embedded in the hydrogel structure need to be released. Both case I and case II of transport refer to the release of the medication during the intermolecular arrangement because of swelling. Numerous mathematical models have been proposed that only include one form of transport; nevertheless, both transport pathways are required for the entire release of a drug from a gel matrix. The case I transport during swelling and the case II transport during the fully swollen condition are both displayed by crosslinked hyaluronic acid hydrogel systems. The methodology put out in this paper enables for the selection of suitable gel compositions while attempting to account for both transit instances. In the Data Envelopment Analysis coupled with principal component analysis approaches are enable the optimization and selection of gel compositions that account for both transport situations.

The socio-economic feasibility of biogas as a renewable source of energy has been analyzed for the energy security of India. The impact of Indian government schemes such as the National Biogas and Manure Management Programme (NBMMP) for the implementation of Bioenergy has been discussed in detail. The feasibility of a water-based scrubber (high as well as low pressure) for Bio-methane production in the Indian scenario was analyzed. Theoretical modeling for Steady-State Digester Pressure Water-based Biogas Scrubber (DP-WBS) was performed using the Sum Rate Method. Design parameters for a DP-WBS-based scrubber having a capacity of 60 Nm 3 /h were optimized at the digester pressure of 110 mm of the Water Column (WC). Modeling for raw biogas (CH 4 64 %, CO 2 30 %, H 2 S 1000 ppm) scrubbing was done with and without water recirculation. Sensitivity analysis shows that a 90 m 3 /h water flow rate and a total of 7 theoretical stages are required to reduce the CO 2 concentration in biogas from 30 % to <2.58 % and H 2 S concentration from 1000 ppm to <20 ppm. H 2 S removal efficiency in the scrubber was found to be highly dependent on operating conditions at the regeneration section.

It is impossible to overstate the value of process simulators in teaching process engineers about petrochemical, chemical, nuclear, and biological processes. Several chemical engineering topics, including process design, thermodynamics, process integration, separation processes, safety, and others, are made easier to teach because of this. Only a handful of these process simulators are freeware, while most are largely commercial. The ones that are commercialized are renowned for their friendliness, extensive media coverage, and international credibility attained for their forecasts in several industrial applications. However, schools in low-income countries may not be able to buy them. In contrast, the freeware publicity is not relatively low, less friendly, and cheaper than the commercial ones. This research compares the agreement of the forecast of commercial process simulators with freeware ones in an effort to strengthen institutions’ trust in the prediction of freeware process simulators. The analysis modeled and simulated a chemical process involving the Gibbs reactor, heater, compressor, and mixer in the COCO and Aspen HYSYS simulators. Findings from the research reveal good agreement in the predicted results obtained from the various process simulators. With the use of COCO, different possible methane oxidation routes were analyzed. The analysis confirmed that the route leading to the formation of CO 2 and water would be less energetic than other routes. In addition, the formation of water would be much easier in the process than hydrogen at the condition employed in the study. Due to cost, the study recommends using the freeware process simulator instead of the cracked version, which is often utilized in educating process engineers and research projects in communities where research and education are poorly funded.

In this present work, a numerical study was conducted for the formation of a slug bubble for shear thinning non-Newtonian fluid in a cross-junction 2-D square horizontal microchannel. Carboxymethyl cellulose (CMC) of concentration 0.2 (w/w%) percent was used as a continuous phase that shows the shear thinning behavior of non-Newtonian fluid and Nitrogen (N 2 ) was used as the discrete phase. The pressure-based double precision solver was used in ANSYS FLUENT 2021 R2 with the volume of fluid (VOF) method. The finite volume method is applied for the discretization of the continuity and momentum equation. This article also focuses on the fluctuation of static pressure, mechanism of slug, annular, and churn annular flow i.e., obtained by the variation in the inlet velocities. On the other hand, a concept that was applied in this work was also validated with the prior literature data.

In recent years, evolutionary algorithms have been gaining popularity for finding optimal solutions to non-linear multimodal problems encountered in many engineering disciplines. Differential evolution (DE), an evolutionary algorithm, is a novel optimization method capable of handling nondifferentiable, non-linear, and multimodal objective functions. DE is an efficient, effective, and robust evolutionary optimization method. Still, DE takes large computational time to optimize the computationally expensive objective functions. Therefore, an attempt to speed up DE is considered necessary. This paper introduces a modification to the original DE that enhances the convergence rate without compromising solution quality. The proposed opposite point-based differential evolution (OPDE) algorithm utilizes opposite point-based population initialization, in addition to random initialization. Such an improvement reduces computational effort. The OPDE has been applied to benchmark test functions and high-dimensional non-linear chemical engineering problems. The proposed method of population initialization accelerates the convergence speed of DE, as indicated by the results obtained using benchmark test functions and non-linear chemical engineering problems.