Nejat Rahmanian

Analysis of Physiochemical Parameters to Evaluate the Drinking Water Quality in the State of Perak, Malaysia

The drinking water quality was investigated in suspected parts of Perak state, Malaysia, to ensure the continuous supply of clean and safe drinking water for the public health protection. In this regard, a detailed physical and chemical analysis of drinking water samples was carried out in different residential and commercial areas of the state. A number of parameters such as pH, turbidity, conductivity, total suspended solids (TSS), total dissolved solids (TDS), and heavy metals such as Cu, Zn, Mg, Fe, Cd, Pb, Cr, As, Hg, and Sn were analysed for each water sample collected during winter and summer periods. The obtained values of each parameter were compared with the standard values set by the World Health Organization (WHO) and local standards such as National Drinking Water Quality Standard (NDWQS). The values of each parameter were found to be within the safe limits set by the WHO and NDWQS. Overall, the water from all the locations was found to be safe as drinking water. However, it is also important to investigate other potential water contaminations such as chemicals and microbial and radiological materials for a longer period of time, including human body fluids, in order to assess the overall water quality of Perak state.

SIMULATION OF UREA PRILLING PROCESS: AN INDUSTRIAL CASE STUDY

A local industrial urea prilling tower with a rectangular cross-sectional area under the operating conditions of free convection was mathematically modeled. In this model the prilling process has been simulated by simultaneous solution of the continuity, hydrodynamic, and thermal equations. Temperature distributions of the particles and the cooling air along the height of the tower were calculated from the model. The air temperature profile predicted by the model was compared with the measured air temperature along the tower. The data predicted by the model were almost in agreement with the plant data, indicating the validity of the model. The result of this study suggests that an increase in heat transfer from the particles using installation of induced fans can reduce the temperature of produced prills and hence reduce caking tendency of the prilled urea.

Flow Analysis of Melted Urea in a Perforated Rotating Bucket

A comprehensive study of the internal flow field for the prilling application in a perforated rotating bucket has been carried out. Computational Fluid Dynamics (CFD) is used to investigate the flow field of urea melt inside the perforated rotating bucket. The bucket is mounted at the top of the prilling tower. In prilling process, urea melt is sprayed by the perforated rotating bucket to produce the urea droplets, which falls down due to gravity. These drops fall down through a cooling medium and solidify into prills. The velocity field in the bucket is very important to study, as it has great effect on the heat and mass transfer performance in prilling process. ANSYS 14.0 CFD package is used to simulate and Design Modeler and Catia V5 are used for geometrical model of the perforated prilling bucket. Velocity distribution on different planes are obtained and discussed.

CFD Modelling of a Hollow Fibre Membrane for CO2 Removal by Aqueous Amine Solutions of MEA, DEA and MDEA

Abstract A mass transfer model was developed to capture CO2 from a gas mixture in hollow fibre membrane contactors under laminar flow conditions. The axial and radial diffusions through membrane and convection in tube and shell sides with chemical reaction were investigated. COMSOL software was used to numerically solve a system of non-linear equations with boundary conditions by use of the finite element method. Three different amine solutions of monoethanolamine (MEA), diethanolamine (DEA) and n-methyldiethanolamine (MDEA) were chosen as absorbent in lumen to consider the mass transfer rate of CO2 and its removal efficiency. The modelling results were compared with experimental data available in the literature and a good agreement was observed. The CFD results revealed that MEA had the best performance for CO2 removal as compared to DEA and MDEA under various operating conditions due to the different CO2 loading factor of absorbents. Furthermore, efficiency of CO2 removal was highly dependent on the absorbent concentration and flow rate, increasing of the gas flow rate caused a reduction in gas residence time in the shell and consequently declined CO2 mass transfer. The modelling results showed the effect of absorbent concentration on the CO2 mass transfer was improved due to availability of absorbent reactants at the gas-liquid interface.

Heat Exchanger Network Optimization by Differential Evolution Method

The synthesis of heat exchanger network (HEN) is a comprehensive approach to optimize energy utilization in process industry. Recent developments in HEN synthesis (HENS) present several heuristic methods, such as Simulated Annealing (SA), Genetic Algorithm (GA), and Differential Evolution (DE). In this work, DE method for synthesis and optimization of HEN has been presented. Using DE combined with the concept of super-targeting, the optimization is determined. Then DE algorithm is employed to optimize the global cost function including the constraints, such as heat balance, the temperatures of process streams. A case study has been optimized using DE, generated structure of HEN and compared with networks obtained by other methods such as pinch technology or mathematical programming. Through the result, the proposed method has been illustrated that DE is able to apply in HEN optimization, with 16.7% increase in capital cost and 56.4%, 18.9% decrease in energy, global costs respectively.

CFD Simulation of Droplet Formation under Various Parameters in Prilling Process

A computational fluid dynamics (CFD) model is used to investigate the droplet formation and deformation under the influence of different parameters. Droplet breakup phenomenon depends on several factors such as viscosity, velocity, pressure difference, and geometry. The most important parameter for droplet breakup is the Weber number (We) which is the ratio of disrupting aerodynamics forces to the surface tension forces. Volume of fluid (VOF) model is used in present work to simulate the droplet breakup. This work presents the effect of liquid velocity, viscosity, and orifice diameters on droplet formation and breakup.

Oil and gas properties and correlations

Crude oil and gas are naturally occurring mixtures composed of mainly hydrocarbons and small amounts of nonhydrocarbon compounds such as sulfur, oxygen, and nitrogen. Crude oil and gas samples are characterized in petroleum engineering by their different physical properties. The composition of reservoir fluid is known as the most significant factor, which affects its PVT behavior. The phase behavior of the reservoir fluid and reservoir temperature are two important factors; the type of reservoir fluid is determined based on them. Crude oil and gas properties are used in various steps of petroleum engineering in order to evaluate oil and gas reserves, recovery efficiency, production optimization, etc. More particularly, the phase behavior of natural gas should be addressed precisely not only for gas reservoirs, but also for oil reservoirs, due to its substantial role in oil production mechanisms of saturated oil reservoirs. Therefore, an accurate evaluation of reservoir fluid properties is required for prediction of oil and gas production during the life time of a hydrocarbon reservoir. Obviously, the best source for description of properties is laboratory experiments of actual reservoir fluid sample. However, there are many correlations that can be used in lack of experimental data for prediction of oil and gas properties. In this chapter, the most physical and thermodynamic properties of crude oil (oil density, oil gravity, compressibility, bubble point pressure, solution gas ratio, oil formation volume factor, and viscosity) and gas (gas density, gas compressibility, gas formation volume factor, and viscosity) are defined, and the corresponding correlations are presented.

Optimal design and operation of semi-batch reactive distillation for methyl lactate synthesis with fixed product demand

Abstract Esterification of lactic acid is a well-known process producing a number of industrially important chemical products such as alky esters, alkyl t-butyl ethers. However, the synthesis of methyl lactate (ML) using batch or semi-batch reactive distillation (SBRD) was not widely considered in the past. Here, the design and operating parameters of SBRD process are optimised while maximising the profit under fixed product demand and strict purity specification. Methanol is fed continuously to improve the conversion of lactic acid. For a given product demand, the profitability is used as the performance measure which is maximized while a number of design (vapour load) and operating parameters (reflux ratio and feed rate) are optimized using model based techniques via gPROMS software. Sensitivity of the operating and utility costs as well as the raw materials prices on the design and operation are discussed. The reboiler is initially fed to the full capacity and an additional constraint is added into the optimisation problem to avoid overloading of still pot (reboiler) at any time of the operation due to continuous feeding of methanol. The control variables (reflux ratio, the methanol feed rate) are treated as a piecewise constant over batch time.

Investigation of the Growth of Particles Produced in a Laval Nozzle

This study focuses on numerical modeling of condensation of water vapor in a Laval nozzle, using the liquid drop nucleation theory. Influence of nozzle geometry, pressure, and temperature on the average drop size is reported. A computer program written in MATLAB was used used to calculate the nucleation and condensation of water vapor in the nozzle. The simulation results are validated with the available experimental data in the literature for steam condensation. The model reveals that the average drop size is reduced by increasing the divergent angle of the nozzle. The results also confirm that increasing the inlet pressure has a direct effect on the average drop size while temperature rise has an inverse effect on the drop size.

Nucleation and Condensation Modeling of Metal Vapor in Laval Nozzle

Nucleation and condensation of mercury vapor has been investigated in various divergent angle and operating condition. Divergent angle has a great effect on droplet size at the end of nozzle. Influence of operating condition such as pressure and temperature on the size of droplet has been investigated. A one-dimensional mathematical model based on classical nucleation and growth has been developed to calculate the nucleation and condensation of mercury vapor. A mercury vapour turbine has been used in conjunction with a steam turbine for generating electricity. The mercury cycle offers an efficiency increase compared to a steam-only cycle because energy can be injected into the Rankine Cycle at higher temperature. The target of modeling is predicting the droplet size of mercury nanoparticles during rapid expansion. The results are verified by accurate experimental data available in the literature. The governing equations were solved using Runge-Kutta third-order numerical method in MATLAB software.