Advanced Materials Research Vol. 917

Abstract: Effluent containing high concentration of alkanolamine from a sweetening process of natural gas plant is commonly generated during maintaining, cleaning and scheduled inspection of the absorption and desorption column. The effluent is not readily biodegradable and cannot be treated in the conventional biological treatment. Advanced oxidation processes (AOPs) is a promising method for the treatment of recalcitrant organic contaminant. Most methods used are Fenton reagent, UV/Ozone and UV/H₂O₂. Based on the advantages of the UV/H₂O₂ such as no formation of sludge during the treatment, high ability in production of hydroxyl radical and applicable in the wide range of pH, the UV/H₂O₂ has been chosen to treat the effluent from refinery plant, which has high concentration of methyldietnaolamine (MDEA). The factors influencing in the degradation of refinery wastewater that contain MDEA were screened using response surface methodology (RSM). It was found that degradation process of the refinery effluent was highly dependent on oxidant concentration (H₂O₂) and initial pH. Temperature of oxidation process was found oppositely. Since the temperature gave insignificant effect on the TOC removal process, hence the independent factor temperature will be eliminated during the further optimization process condition of degradation. Thus, the optimization process condition of degradation will be more effective and simpler.

Abstract: The coating of the fluorescent-lamp material inside the fluorescent tube is prone to defect such as dark line formation. A one-dimensional mathematical model based on Navier-Stokes equation, which describes the flow of drying coating on horizontal planar substrates, was developed to investigate the defect formation. The effect of temperature distribution on surface tension gradient was incorporated into the model, to quantify defect formation in drying coating. The results showed that, temperature-induced surface tension gradient plays a major role in defect formation while the effect of pressure gradient is insignificant. The evaporation rate and viscosity affect the defect thickness and spread, and also the defect formation time. The temperature gradient seems to have the largest influence on surface tension gradient, thus defect formation. The model developed can be used as a process analysis tool in industrial applications of fluorescent tube coating.

Abstract: Semi-empirical threshold fouling models predict higher fouling rates at high surface or film temperatures. Several experimental fouling data reported in literature and from our study were analyzed with respect to increase in surface and bulk temperatures that showed a decrease in fouling rates. The existing threshold fouling models do not adequately describe the phenomenon of decreasing fouling rates with increase in surface or bulk temperatures. The possible causes including the effect of temperature difference, heating regime and solubility of fouling precursors were analyzed and reported.

Abstract: In this paper, a model for urea prilling tower with co-current flow of cooling air and urea prills (particles) is presented. The process is modelled by simultaneous solution of the differential equations for hydrodynamics, heat and mass transfer between the air and prills. The process variables such as temperature, absolute and relative humidity of air along the height of the tower were obtained from this model. Temperature and moisture distribution of urea prills and their radial and vertical velocities were also calculated. The results of the present model were compared with the counter-current operation model available in the literature. The simulation results show that heat transfer performance for co-current operation is significantly less than that of the counter-current scenario. This is more pronounced for small prills, i.e. 1.0 mm than that of the large prills. The advantage of the model is that it can be used to investigate influence of operating parameters on efficiency of the co-current process. This also helps us to set the process control strategies for design and quality control purposes of the process.

Abstract: Mismatches between model and plant can degrade the controller performance. Detection and correction of model parameters are required to prevent re-identification process of the whole plant. This paper proposes a method to automatically detect and correct model gain mismatch in the case of Wood-Berry column. Taguchi experiments are initially carried out to identify the most significant model gains. A set of variables called the linear residual-input ratio (LRIR) are developed to detect changes in the plant gains thus correcting the gains to bring the process to the desired setpoint. The proposed method is able to correct the mismatches in magnitude for individual and multiple gains within the range of the linear equations.

Abstract: Crude distillation unit (CDU) is one of the largest energy consumer units in a refinery. It consumes around 35-40% of the total process energy in refinery. This paper presents a systematic approach for selecting optimization variables using Taguchi method. These variables are subsequently employed in minimizing energy consumption per unit diesel production at CDU. A steady state model of the CDU was developed under the HYSYS 7.2 environment and utilized to demonstrate the efficacy of this method. Optimum energy consumption per unit diesel production obtained from Taguchi were validated by comparing the results with those obtained from HYSYS built-in SQP solver. The results reveal that the combination of Taguchi and SQP solver can reduce CPU time for optimization purposes.

Abstract: A pipe segment system has been used to estimate its inherent resilience properties for the variation of mass flow rate, inlet temperature and inlet pressure. Superheated steam is taken as the process fluid. The magnitude of the resilience decreases from 927.8 kJ/m³s to 43 kJ/m³s and 31.5 kJ/m³s for variation of mass flow rate, inlet pressure and inlet temperature respectively. In this work, a novel methodology has been described for quantification of inherent system resilience and resilience magnitude has been found to be highest (927.8 kJ/m³s) in case of variation of mass flow rate through the pipe segment system. A useful correlation T = T_a(1-e^-nL)+T_se^-nL has been formulated for estimation of process fluid temperature, T at any pipe length, L.

Abstract: This paper is an attempt to compare the the performance of the three different Multilayer Perceptron training algorithms namely Backpropagation, Scaled Conjugate Gradient and Levenberg-Marquardt for the prediction of the gas hold up and frictional pressure drop across the vertical pipe for gas non-Newtonian liquid flow from our earlier experimental data. The Multilayer Perceptron consists of a single hidden layer. Four different transfer functions were used in the hidden layer. All three algorithms were useful to predict the gas holdup and frictional pressure drop across the vertical pipe. Statistical analysis using Chi-square test (χ2) confirms that the Backpropagation training algorithm gives the best predictability for both cases.

Abstract: This study aims to investigate the impact of process parameters to the column temperature rise during the absorption process using response surface methodology (RSM). The parameters studied were liquid temperature, column pressure, CO₂ inlet concentration and gas flow rate. While all the factors studied had significant impact to the quadratic model for the temperature rise, the magnitude of temperature rise was more obvious with the variation of column pressure and CO₂ inlet concentration. The column temperature rise was found to be high when the liquid temperature, column pressure and CO₂ inlet concentration were high. Similar behavior of high column temperature rise was also observed when the gas flow rate was low.

Abstract: A 2D axi-symmetric, steady state and pressure-based model for the riser of an industrial RFCC unit was developed with ANSYS FLUENT in workbench 13.0. The EulerianEulerian approach was applied to simulate the flow behavior of the two phases and the catalytic cracking reactions. The k-ε gassolid turbulent flow per phase model was used, and the particle-level fluctuations are modeled in the framework of the kinetic theory of granular flow. Two different drag models were used separately to simulate the gas solid interaction in the riser fluidized bed. The 14-lump kinetic model was chosen to describe the complex catalytic cracking of the heavy residual feed stock. The particle volume fraction, velocity and temperature profiles, as well as product yields in the riser were analyzed and validated with results from open literature and the industrial RFCC plant data.