Band 18, Heft 1

Mineral processing facilities concern an enormous amount of dynamically complex unit operations (due to nonlinearities), for instance ball mill system. Normally, these processes need multivariable controllers to smooth actions by designing for plant constraints such as deadtimes and dynamics interactions. The present work presents a comparison between a classical PI and nonlinear moving average autoregressive-linearization level 2 (NARMA-L2) controllers based on artificial neural network (ANN) for a ball mill system. The manipulated variables of this plant are the rotation velocity (Vr) and the feeding weight (Wf), while the controlled parameters are the hold up (HU) and the mass fraction under 45 μm (P45). The simulation was built in the MATLAB software (Simulink), comparing the actions of PI and NARMA-L2 controllers in the face of operational changes in specific regions (constraints). The performance of proposed controllers was verified by the integral of absolute error (IAE), integral of squared error (ISE), or the integral of time-weighted absolute error (ITAE). The results of simulation showed the validity of the model obtained and the control technique proposed in this paper, which contributes to studies of multivariate controller designs for ball mills with significant applications. Additionally, this paper brings a first hybrid approach (PI/NARMA-L2) with successful implementation described in the literature.

In this article, a unified control scheme is proposed for dead-time compensation and disturbance rejection via feedback and feedforward controller. The objectives of this work are suggested in two folds, first tuning of fractional order feedback controller via delayed Bode’s ideal transfer function instead of conventional Bode’s ideal transfer function with the benefits of dead time compensator and second feedforward controller for disturbance rejection. An existing method is utilized for comparison with the proposed scheme. To examine the efficacy of the proposed method robustness test is also carried out via sensitivity analysis. For quantifiable evaluation of the proposed scheme Integral Absolute Error (IAE) and Integral Square Error (ISE) are utilized. For the usefulness of the proposed scheme, two practical problems are demonstrated in this paper. The limpidity and instinctive appeal of the proposed scheme make it beautiful for industrial applications.

In the present work, three-Dimensional stationary numerical simulations were accomplished for a deeper understanding of the gas mixtures separation by the thermogravitational column. To address the optimum condition and examine the limitation of the process, the thermogravitational column behavior has been thoroughly analyzed. First, the simulation model was validated by the experimental results of Youssef et al. then the model was developed for the pilot column. The mixture of helium-argon was chosen as feed composition. It was concluded that the variation of the separation factor in relation to pressure for both columns was almost the same. The optimum condition verified as p = 0.2  atm , θ = 0.4 , m ° = 4   SCCM $p=0.2\text{atm},\theta =0.4,m{}^{\circ}=4\hspace{0.17em}\text{SCCM}$ .

This work reveals an Internal Model Control (IMC)-based series cascade control for the non-minimum phase and time delay process. The combination of a higher-order fractional IMC filter and inverse response compensator for designing the outer loop controller illustrates the uniqueness of this work. For the time delay term, a higher-order approximation is considered. The standard IMC-PID structure adopts for the inner loop controller design. While the higher-order fractional filter coupled with inverse response compensator takes for the design of the outer loop controller. The suggested scheme demonstrates enhanced exhibition for setpoint tracking and disturbance rejection. Moreover, the sensitivity analysis is also accomplished to determine the robustness of the closed-loop system under process parameter variations.

Despite the fact of being intensive energy consumption, MSF is a mature technology that characterised by a high production capacity of high-quality water. The multistage flash (MSF) desalination process is one of the prominent thermal desalination used in the industry of seawater desalination to produce high quantity and high quality of freshwater. However, this process consumes large amount of energy and faces thermal limitations due to its high degree of exergy destruction at several units of the process. Therefore, the research of MSF is still existed to elevate the performance indicators and to resolve the concern of high energy consumption. To rectify these limitations, it is important to determine the units responsible in dissipating energy. This study aims to model an industrial MSF process validated against real data and then investigate the exergy destruction and thermodynamic limitations of the process. As a case study, Azzour MSF seawater desalination plant, located in Al Khiran in Kuwait is under the focus. A comprehensive model is developed by analysing several published models. Specifically, the calculation of exergy destruction has embedded both physical and chemical exergies that identified as a strong point of the model developed. As expected, the highest exergy destruction (55.5%) occurs within the heat recovery section followed by the brine heater with exergy destruction of 28.26% of the total exergy destruction. This study identifies the sections of the industrial process that cause the highest energy losses.

In this study, numerical simulations were carried out to investigate the separation of the helium-argon gas mixture by thermal diffusion column. This research determined the significant parameters and their effects on the process performance. Effects of feed flow rate, cut ratio, and hot wire temperature in a 950 mm height column with an inner tube of 9.5 mm radius were examined through the simulation of the thermal diffusion column. For minimizing the number of simulations and obtaining the optimum operating conditions, response surface methodology (RSM) was used. Analysis of separative work unit (SWU) values as a target function for helium-argon separation clearly showed that the maximum amount of SWU in thermal diffusion column was achieved, when hot wire temperature increased as large as technically possible, and the feed rate and cut ratio were equal to 55 Standard Cubic Centimeters per Minute (SCCM) and 0.44, respectively. Finally, the SWU value in optimum conditions was compared with the experimental data. Results illustrated that the experimental data were in good agreement with simulation data with an accuracy of about 90%.

H 2 S is becoming more and more appealing as a source for hydrogen and syngas generation. Its hydrogen production potential is studied by several research groups by means of catalytic and thermal conversions. While the characterization of catalytic processes is strictly dependent on the catalyst adopted and difficult to be generalized, the characterization of thermal processes can be brought back to wide-range validity kinetic models thanks to their homogeneous reaction environments. The present paper is aimed at providing a reduced kinetic scheme for reliable thermal conversion of H 2 S molecule in pyrolysis and partial oxidation thermal processes. The proposed model consists of 10 reactions and 12 molecular species. Its validation is performed by numerical comparisons with a detailed kinetic model already validated by literature/industrial data at the operating conditions of interest. The validated reduced model could be easily adopted in commercial process simulators for the flow sheeting of H 2 S conversion processes.

This study presents a novel design and techno-economic analysis of processes for the purification of captured CO 2 from the flue gas of an oxy-combustion power plant fueled by petroleum coke. Four candidate process designs were analyzed in terms of GHG emissions, thermal efficiency, pipeline CO 2 purity, CO 2 capture rate, levelized costs of electricity, and cost of CO 2 avoided. The candidates were a classic process with flue-gas water removal via condensation, flue-gas water removal via condensation followed by flue-gas oxygen removal through cryogenic distillation, flue-gas water removal followed by catalytic conversion of oxygen in the flue gas to water via reaction with hydrogen, and oxy-combustion in a slightly oxygen-deprived environment with flue-gas water removal and no need for flue gas oxygen removal. The former two were studied in prior works and the latter two concepts are new to this work. The eco-technoeconomic analysis results indicated trade-offs between the four options in terms of cost, efficiency, lifecycle greenhouse gas emissions, costs of CO 2 avoided, technical readiness, and captured CO 2 quality. The slightly oxygen-deprived process has the lowest costs of CO 2 avoided, but requires tolerance of a small amount of H 2 , CO, and light hydrocarbons in the captured CO 2 which may or may not be feasible depending on the CO 2 end use. If infeasible, the catalytic de-oxygenation process is the next best choice. Overall, this work is the first study to perform eco-technoeconomic analyses of different techniques for O 2 removal from CO 2 captured from an oxy-combustion power plant.

Ethyl acetate (EtAc) reactive distillation (RD) configurations often use atmospheric pressure, and this operating pressure can be reduced further to conserve energy based on the condenser cooling water temperature. Using the Aspen Plus simulator, two proposed configurations, RD column with stripper and pressure swing reactive distillation (PSRD), were simulated at lower operating pressure. The impact of RD column operating pressure on total energy usage and total annual cost (TAC) was studied. All design parameters were optimized using sequential iterative optimization procedures and sensitivity analysis to minimize the energy cost while maintaining the required product purity at 99.99%. The simulation results showed that the RD column with a stripper is better than PSRD with a saving of 23.17% in TAC and 31.53% in the specific cost of EtAc per kg. Compared to literature results, the proposed configurations have lower reboiler duty requirements and lower cost per kg of EtAc.

This paper presents cost-effective heat pump assisted vapor recompression (VRC) design algorithms for the separation of ternary wide boiling mixture in batch distillation in order to reduce total annual cost (TAC) and carbon dioxide (CO 2 ) emissions. A minimum TAC and CO 2 is required by the batch distillation process industry for any investments in heat integrated systems, such as VRC. Consequently, the design conditions for implementing VRC should be chosen such that the energetic performance is maximum at minimum TAC. The model system selected in this paper is an application involving high temperature lift, that is, hexanol–octanol–decanol ternary wide boiling mixture. First, a systematic simulation algorithm was developed for conventional multicomponent batch distillation (CMBD) and single-stage vapor recompressed multicomponent batch distillation (SiVRMBD) to determine the optimal number of stages based on the maximum TAC savings. The SiVRMBD saves more energy and TAC than CMBD. However, SiVRMBD has a high compression ratio (CR) throughout the operation, which is not practically feasible for the batch distillation processing. Second, in order to increase the performance and minimize the SiVRMBD weakness, a novel optimal multi-stage vapor recompression algorithm was proposed to operate at the lowest possible CR (<3.5) throughout the batch operation while also conserving the most TAC. Overall, the findings suggest that the proposed optimal multi-stage VRC reduces TAC and CO 2 emissions significantly when compared to CMBD. Finally, the influence of the different feed compositions on VRC performance is also studied.