This study has been carried out to demonstrate the control of a reactive distillation process in which the production of biodiesel was taken as the case study using an advanced control method, which is known as dynamic matrix control. The control was accomplished by employing the transfer function model of the reactive distillation process developed, using the System Identification Toolbox of MATLAB, from the dynamic data generated when the prototype plant of the process was simulated with the aid of ChemCAD process simulator. The results obtained from the dynamic matrix control were compared with those of a proportional-integral-derivative (PID) control system tuned with Ziegler-Nichols and Cohen-Coon methods, and it was discovered that the dynamic matrix control was able to perform best among the three (dynamic matrix control method, PID tuned with Ziegler-Nichols method and PID tuned with Cohen-Coon method) because it (the dynamic matrix control) was able to make the biodiesel mole fraction response not to exceed the maximum limit value of 1 in addition to having the lowest sum of absolute errors (SAE) and sum of squared errors (SSE) from the control systems that were simulated.
This work has been carried out to demonstrate the application of a process simulator known as CHEMCAD to the modelling and the simulation of a reactive distillation process used for the production of n-butyl acetate, with water as the by-product, from the esterification reaction between acetic acid and n-butanol. The esterification reaction, which is generally an equilibrium type, was modelled as two kinetic reaction types in the reaction section of the column used, which had 17 stages with the middle section (stages 6 – 12) being the reaction section. A reflux ratio of 3 and reboiler duty of 78 kJ/min as well as 30 mL/min of each of the reactants with 99% molar purity were used for the simulation of the column. The results obtained revealed that the developed model was a valid one because there was a very good agreement between the results and the theoretical knowledge of a distillation column based on the fact that the desired (which was the heavy) product (n-butyl acetate) was found to have the highest mole fraction in the bottom section of the column while the by-product of the process (water) was discovered to have a mole fraction higher than that of n-butyl acetate in the top (condenser) section of the column. Therefore, CHEMCAD has been applied to the steady-state simulation of the reactive distillation process used for the production of n-butyl acetate from the esterification reaction of acetic acid and n-butanol successfully.
Abstract.Reactive distillation is a process that combines chemical reaction and separation in a single piece of equipment (distillation column). The process has a lot of benefits especially for those reactions occurring at conditions suitable for the distillation of the process components, and these result in significant economic advantages. However, owing to the complexities resulting from the integration of reaction and separation, its control is still a challenge to process engineers because it requires a control method that is robust enough to handle its complexities. Therefore, in this work, model predictive control (MPC) has been applied to a reactive distillation process used for developing a renewable energy known as biodiesel. The control algorithm of the MPC was formulated with the aid of MPC toolbox of MATLAB/Simulink in which the closed-loop models of the process were developed and simulated. The analysis of the results obtained from the simulations carried out for the optimization of the tuning parameters revealed that, among the tuning parameters considered, integral absolute error of the control system was less affected by the control horizon because its p-value was greater than 0.05 based on 95% confidence level. Furthermore, the simulation of the closed-loop system of the process using model predictive control tuned with control horizon of 11, prediction horizon of 18, weight on manipulated variable rate of 0.05 and weight on output variable of 2.17, which were the optimum parameters obtained using Excel Solver, showed that the system was well handled by the controller under servo control because it was able to get settled at desired mole fractions within 60 min. However, the settling time recorded in the case of regulatory control system of the process with the same controller was found not to be encouraging. Therefore, it is recommended that further work should be carried out on this subject matter in an attempt to obtain tuning parameters that will make the settling time of the closed-loop system of the process under regulatory control simulation very reasonable. Nomenclature ANOVA
In this study, Dijah-Monkin bentonite clay was modified with a cationic surfactant hexadecyltrimethylammonium bromide (HDTMA-Br) at the level of twice the cation exchange capacity (CEC). This process results in the development of hydrophobic organoclay with an improved adsorption capacity. The clay obtained from Zing LGA Taraba State, North-East Nigeria, was beneficiated and pulverised to a particle size of 125 µm. The modification was performed without acid activation to prevent damages to the clay’s crystal structure. The organoclay was characterised for chemical composition, functional groups, mineralogical and surface morphology using X-ray fluorescence (XRF), Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The XRD showed an increase in the basal spacing from 15.681Å to 17.758 Å, while the XRF revealed a 5.35% concentration of Br on the modified clay, indicating successful intercalation. The FTIR spectra also revealed the appearance of symmetric and asymmetric stretching bands at 2847.7cm-1 and 2914.8cm-1, respectively, as a consequence of the modification, resulting in more sites for adsorption.
In the recent time, there is increasing research in the area of alternative fuels as the exhausts of presently used petroleum-based fuels have been identified to have negative effects on the environment. Fuels produced from plant oils and animal fats have the tendencies of replacing petro fuels since they are renewable in nature. One of these renewable fuels is biodiesel. However, the homogenous catalyst used in biodiesel production has some drawbacks such as difficulty in separation from the fuel, soap formation and corrosiveness of the product mixture. In this work, the use of heterogeneous catalyst sourced from local raw materials (kaolin and eggshell) for the production of biodiesel from oil of desert date seed has been investigated. The kaolin obtained from Alkaleri Mining Site, Bauchi, was calcined in an oven at 800 °C for 3 h. The calcined kaolin was then chemically activated. Also, the eggshell-based catalyst was produced from raw eggshells after washing, drying, grinding, sieving using 0.3 mm sieve size and calcining at 900 °C for 3 h. Furthermore, the oil content of the desert date seed, which was acquired from a local market in Bauchi, was extracted via solvent extraction in a laboratory with a yield of 42%. Then, the biodiesel was subsequently prepared by mixing the oil, methanol and catalyst in a flat bottom flask and heating the mixture for a specified period. The catalyst concentration, methanol to oil ratio and time of reaction were subsequently varied to obtain the best yield. The results obtained revealed that an optimum yield of 29% could be obtained at methanol to oil ratio of 6:1 and a reaction time of 60 min using 1.5 g of eggshell-based catalyst while an optimum yield of 22% was obtained with 0.6 g for kaolin-based catalyst at a reaction time of 60 min and methanol to oil ratio of 4:1. It is recommended that further work should be carried out to improve on the yield of the biodiesel obtained using the heterogeneous catalysts.
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