Abstract. Nickel laterite ore contains oxide of iron, aluminum or both with nickel, cobalt and chromium which can be leached out using hydrometallurgical process. For the purpose of meeting the world's increasing demand of nickel, there is a need to invent environmentally friendly process to efficiently leach nickel. This experiment used nickel laterite ore obtained from Pomalaa, South Sulawesi. The leaching agent is metabolic citric acid produced by Aspergillus niger under optimum condition. Leaching process was done in three-necked flask in atmospheric temperature and constant stirring speed of 200 rpm. The variable examined in the experiment was pulp density and particle size of nickel laterite ore. Samples were taken at 3, 7, 10, 14, and 17 minutes and then filtered and diluted to be analyzed using ICP-AES. The result of the experiment showed the maximum recovery of metals increase with the decrease of the pulp density. The maximum recovery for varying pulp density were at 5% solid/liquid ratio and the recovery were Ni at 1.63%, Al at 0.47%, Fe at 0.23% and Mg at 1.09%. The effect of particle size on leaching process showed that the leaching process follows the shrinking core model. The maximum recovery of metals at particle size were at 100-120 mesh with Ni at 1.37%, Fe at 0.10%, Al at 0.72% and Mg at 0.62%.
In operating biogas-fueled SOFC module, impurities such as H2S and siloxane can poison reforming catalyst and anode. To achieve a stable SOFC operation, fuel impurity poisoning of Ru/γ-Al2O3 catalyst has to be examined. Poisoning test for the reformer and the reformer-SOFC series were performed at 700oC. Humidified simulated biogas with varied concentration of H2S or siloxane was supplied to Ru/γ-Al2O3 beads-packed reformer. H2S poisoning test during biogas steam reforming showed a correlation between the degradation rate of CH4 conversion and the decrease rate of Ru surface area which increased with increasing H2S concentration. In the case of siloxane poisoning test, accumulated-silica covered the catalyst surface, resulting in the degradation of CH4 conversion although milder than the case of H2S. The poisoning tests for the reformer-SOFC series revealed that the degradation rate of cell voltage was considerably lower than that of CH4 conversion in the reformer for both impurities.
Abstract-In this research, Proportional-Integral-Derivative (PID) controller was integrated into the advanced control system to achieve an optimal performance. One type of advanced control system is cascade control. In conventional cascade control, controller parameters in primary and secondary loops are tuned sequentially. First, the parameters in secondary controller are tuned using certain tuning rule, meanwhile the primary loop in the open loop mode. Furthermore, the controller parameters in primary loop are tuned by considering the influence of the controlled secondary loop. This makes the tuning of PID cascade control more difficult and takes more time consuming. This paper describes a method of simultaneous tuning cascade control system using Duelist Algorithm (DA) to estimate the proper control parameters of the primary and the secondary loops in the plants. The analysis was conducted based on the evaluation of the closedloop response to a step set point changes. The results show that the proposed method has better control performance than the previous method. PID auto tuning using DA provide more robust performance of the control system.
Ionic liquids demonstrated successful potential applications in the industry most specifically as the new generation of solvents for catalysis and synthesis in chemical processes, thus knowledge of their physico-chemical properties is of great advantage. The present work presents a mathematical correlation that predicts density of binary mixtures of ionic liquids with various alcohols (ethanol/methanol/1-propanol). The artificial neural network algorithm was used to predict these properties based on the variations in temperature, mole fraction, number of carbon atoms in the cation, number of atoms in the anion, number of hydrogen atoms in the anion and number of carbon atoms in the alcohol. The data used for the calculations were taken from ILThermo Database. Total experimental data points of 1946 for the considered binaries were used to train the algorithm and to test the network obtained. The best neural network architecture determined was found to be 6-6-10-1 with a mean absolute error of 48.74 kg/m3. The resulting correlation satisfactorily represents the considered binary systems and can be used accurately for solvent related calculations requiring properties of these systems.
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