• Estimation of Dulling Rate and Bit Tooth Wear Using Drilling Parameters and Rock Abrasiveness

      Mazen, Ahmed Z.; Rahmanian, Nejat; Mujtaba, Iqbal M.; Hassanpour, A. (2019)
      Optimisation of the drilling operations is becoming increasingly important as it can significantly reduce the oil well development cost. One of the major objectives in oil well drilling is to increase the penetration rate by selecting the optimum drilling bit based on offset wells data, and adjust the drilling factors to keep the bit in good condition during the operation. At the same time, it is important to predict the bit wear and the time to pull out the bit out of hole to prevent fishing jobs. Numerous models have been suggested in the literature for predicting the time to pull the bit out to surface rather than predict or estimate the bit wear rate. Majority of the available models are largely empirical and can be applied for limited conditions, and do not include all the drilling parameters such as the formation abrasiveness and bit hydraulic. In this paper, a new approach is presented to improve the drill bit wear estimation that consists of a combination of both Bourgoyne and Young (BY) drilling rate model and theory of empirical relation for the effects of rotary speed (RPM), and weight on bit (WOB) on drilling arte (ROP) and rate of tooth wear. In addition to the drilling parameters, the formation abrasiveness and the effect of the jet impact force of the mud have also been accounted to estimate the bit wear. The proposed model enables estimation of the rock abrasiveness, and that lead to calculate the dynamic dulling rate of the bit while drilling that used in more accurate to assess the bit tooth wear compared with the mechanical specific energy (MSE). Then the estimated dulling rate at the depth of pulling out is used to determine the dull grade of the bit. The technique is validated in five wells located in two different oil fields in Libya. All studied wells in this showed a good agreement between the actual bit tooth wear and the estimated bit tooth wear.
    • An experimental investigation into the permeability and selectivity of PTFE membrane: a mixture of methane and carbon dioxide

      Gilassi, S.; Rahmanian, Nejat (Taylor & Francis, 2016)
      Research and technology innovations in the 1970s led to the significant commercial practice of gas separation by membranes that exists today. These advances involved developing membrane structures that could produce high fluxes and modules for packing a large amount of membrane area per unit volume (Murphy et al., 2009). At present, the share of using a polymeric membrane in the capture of CO2 is increasing and gradually the membrane technology is considered as the promising method in separation units, although the number of commercial membranes is not high. CO2 capture from natural gas is one of the controversial topics that many researchers and engineers try to find the best method satisfying both high efficiency and low capital cost. In common, chemical physical absorption towers are applied to remove CO2 from natural gas in order to prevent pipeline corrosion, even though the other component such as H2S gives rise to operating problems. The obscure angle of a conventional unit is related to the high energy consumption while the absorbent needs to be purified by the regeneration units which implement the temperature as a unique manipulating parameter for separating amine groups. The great advantages of using the membrane in gas industry are the low capital cost, easy installation and maintenance so that for this simple reason, new membranes come to the market for different types of processes. Capture of CO2 from natural gas accounts for one of the major difficulties so that the engineers try to employ membrane modules as to alter the process efficiency. However, there are only a limited number of membranes that can be used in real industry and the research still continues over this interesting topic (Burggraaf and Cot, 1996).
    • An experimental investigation on seeded granulation of detergent powders

      Rahmanian, Nejat; Halmi, M.H.; Choy, D.; Patel, Rajnikant; Yusup, S.; Mujtaba, Iqbal M. (2016-08-20)
      Granulation is commonly used as an enlargement process of particles produce granules with desirable characteristics and functionality. Granulation process transforms fine powders into free-flowing, dust-free granules with the presence of liquid binder at certain operating conditions. The main focus of this research is on seeded granulation of detergent powders, a new phenomenon of granulation in which a layer of fine powders surround the coarse particle. This is already proven for calcium carbonate (Rahmanian et al., 2011). Here, detergent granules were produced in a 5 L high shear Cyclomix granulator using different fine/coarse powder ratio (1/3, 1, 3) and different binder ratio of 10 %, 20 % and 30 %. The granules were then characterized for their particle size distribution, strength and structure. It was found that a high percentage (70 wt. %) of granules in the desired size range between 125 - 1,000 µm were produced using the powder ratio of 1/3 and a binder content of 10 %. Low mean crushing strength (3.0 N) with a narrow distribution was obtained using this condition. Structure characterization of the detergent granules produced in the granulator shows that consistent seeded granule structures are produced under the optimum process and formulation conditions of 1/3 powder ratio with 10 % binder.
    • Feasibility of Integrated Batch Reactive Distillation Columns for the Optimal Synthesis of Ethyl Benzoate

      Aqar, D.Y.; Rahmanian, Nejat; Mujtaba, Iqbal M. (2017-12-08)
      The synthesis of ethyl benzoate (EtBZ) via esterification of benzoic acid (BeZ) with ethanol in a reactive distillation is challenging due to complex thermodynamic behaviour of the chemical reaction and the difficulty of keeping the reactants together in the reaction zone (ethanol having the lowest boiling point can separate from the BeZ as the distillation proceeds) causing a significant decrease in the conversion of BeZ in a conventional reactive distillation column (batch or continuous). This might be the reason of not reporting the use of reactive distillation for EtBZ synthesis although the study of BeZ esterification reaction is available in the public literature. Our recently developed Integrated Conventional Batch Distillation (i-CBD) column offers the prospect of revisiting such reactions for the synthesis of EtBZ, which is the focus of this work. Clearly, i-CBD column outperforms the Conventional Batch Distillation (CBD) column in terms of product amount, purity and conversion of BeZ and eliminates the requirement of excess use of ethanol. For example, compared with CBD column, the i-CBD operation can yield EtBZ at a much higher purity (0.925 compared to 0.730) and can convert more benzoic acid (93.57% as opposed to only 74.38%).
    • Feasibility of novel integrated dividing-wall batch reactive distillation processes for the synthesis of methyl decanoate

      Aqar, D.Y.; Rahmanian, Nejat; Mujtaba, Iqbal M. (2018-08-31)
      The production of methyl decanoate (MeDC) through esterification of decanoic acid (DeC) with methanol by reactive distillation is operationally challenging and energy-intensive due to the complicated behaviour of the reaction system and the difficulty of retaining the reactants together in the reaction region. Methanol being the lightest component in the mixture can separate itself from the reactant DeC as the distillation proceeds which will cause a massive reduction in the conversion of DeC utilizing either a batch or continuous distillation process. Aiming to overcome this type of the potential problem, novel integrated divided-wall batch reactive distillation configuration (i-DWBD) with recycling from the distillate tank is established in this study and is examined in detail. This study has clearly demonstrated that the integrated divided-wall batch reactive distillation column (i-DWBD) is superior to the traditional conventional batch distillation (CBD) and both the divided-wall (DWBD), and split reflux divided-wall (sr-DWBD) batch reactive distillation configurations in terms of maximum achievable purity of MeDC and higher conversion of DeC into MeDC. In addition, significant batch time and energy savings are possible when the i-DWBD is operated in multi-reflux mode.
    • Flow analysis of melted urea in a perforated rotating bucket

      Muhammad, A.; Rahmanian, Nejat; Pendyala, R. (2013-10)
      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.
    • Heat exchanger network optimization by differential evolution method

      Thuy, N.T.P.; Pendyala, R.; Rahmanian, Nejat; Marneni, N. (2014)
      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 ΔTmin 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.
    • High-pressure solubility of light gases in heavy n-alkanes from apredictive equation of state: Incorporating Henry’s law constant intobinary interaction parameter

      Nasrifar, K.; Rahmanian, Nejat (2014-11-15)
      Using fugacity coefficient of a cubic equation of state, Henry’s law constant of a solute in a solvent isincorporated into binary interaction parameter of the classical attractive parameter mixing rule. Thedeveloped equation is a function of temperature. The binary interaction parameter is evaluated by purecomponent critical properties and acentric factors of the solute and the solvent and the Henry’s lawconstant of the solute in the solvent. The developed model accurately describes the solubility of gasesincluding methane, ethane, nitrogen, carbon dioxide and hydrogen sulphide in heavy n-alkanes from lowto high pressure for wide range of temperature. The solubility of methane and carbon dioxide in wateris also predicted adequately.
    • Hydrodesulfurization of crude oil over Co-Mo catalysts in a slurry reactor

      Porgar, S.; Rahmanian, Nejat (2015)
      In this paper, hydrodesulfurization (HDS) of crude oil in the three-phase slurry reactor over cobalt – molybdenum catalyst (CoMo / ɣ- AL2O3) is studied. Effects of space velocity and length of reactor on the conversion rate and catalyst effectiveness for HDS process have been investigated. Kinetics of the reaction rate for this process is primarily and Arrhenius equation for the rate constant is used. The results show that the effectiveness factor for catalyst along the length of reactor is decreased about 83%. By increasing liquid velocity from 4 to 10 1/s, the conversion of sulfur components is decreased about 22% at the temperature of 523 K. At the same temperature, by increasing liquid velocity from 36 to 84 1/s conversion is reduced to 25%. The results of the variation of the dimensionless reaction rate against conversion show that with increasing conversion, the reaction rate decreases and the reaction is stopped when the conversion is 100%.
    • Influence of type of granulators on formation of seeded granules

      Kitching, V.R.; Rahmanian, Nejat; Jamaluddin, N.H.; Kelly, Adrian L.; CCIP grant (Collaboration, Capacity and IP Develop-ment) fund from the University of Bradford. (2020-08)
      It has been shown that seeded granules of calcium carbonate can be produced in commercial batch high shear granulators such as the Cyclomix high-shear impact mixer. Seeded granules are attractive to the pharmaceutical industry due to their high uniformity and good mechanical properties which can assist efficient tablet manufacture. In the current study, attempts to produce seeded granules of Durcal 65 and PEG 4000 binder using hot melt granulation are reported, in response to the recent shift towards continuous pharmaceutical manufacturing. Various screw configurations and rotation speeds were investigated in a series of experiments to determine the relationship between process conditions and granule properties. Particle size analysis, strength measurement and structural characterisation were used to quantify granule properties. It was found that using a series of kneading elements arranged at a 60° staggering angle located near to the feed section of the extruder screw generated strong, spherical granules. From structural characterisation approximately 5–15% of extruded granules were found to be seeded. Twin screw melt granulation is therefore considered to be a promising technique for continuous production of seeded granules, although a more detailed investigation is required to optimise yield and quality.
    • Integrated Batch Reactive Distillation Column Configurations for Optimal Synthesis of Methyl Lactate

      Aqar, D.Y.; Rahmanian, Nejat; Mujtaba, Iqbal M. (2016-10)
      Although batch reactive distillation process outperforms traditional reactor-distillation processes due to simultaneous reaction and separation of products for many reaction systems, synthesis of Methyl lactate (ML) through esterification of lactic acid (LA) with methanol in such process is very challenging due to difficulty of keeping the reactants together when one of the reactants (in this case methanol) has the lowest boiling point than the reaction products. To overcome this challenge, two novel reactive distillation column configurations are proposed in this work and are investigated in detail. These are: (1) integrated conventional batch distillation column (i-CBD) with recycled methanol and (2) integrated semi-batch and conventional batch distillation columns (i-SBD) with methanol recovery and recycle. Performances of each of these configurations are evaluated in terms of profitability for a defined separation task. In i-SBD column, an additional constraint is included to avoid overflow of the reboiler due to continuous feeding of methanol into the reboiler as the reboiler is initially charged to its maximum capacity. This study clearly indicates that both integrated column configurations outperform the traditional column configurations (batch or semi-batch) in terms of batch time, energy consumption, conversion of LA to ML, and the achievable profit.
    • Investigation about profitability improvement for synthesis of benzyl acetate in different types of batch distillation columns

      Aqar, D.Y.; Rahmanian, Nejat; Mujtaba, Iqbal M. (2018-08-01)
      In this work, for the first time, the synthesis of benzyl acetate via the esterification of acetic acid and benzyl alcohol is investigated in the reactive distillation system using a middle vessel (MVD), inverted (IBD), and conventional batch reactive distillation columns. The measurement of the performance of these column schemes is determined in terms of profitability through minimization of the batch time for a defined separation task. The control variables (reboil ratio for MVD, IBD columns) and (reflux ratio in case of CBD column) are considered as piecewise constants over batch time. The optimization results obviously indicate that the CBD system is a more attractive process in terms of batch time reduction, and maximum achievable yearly profit as compared to the MVD, and IBD operations.
    • Investigation of Effect of Aluminium Oxide Nanoparticles on the Thermal Properties of Water-Based Fluids in a Double Tube Heat Exchanger

      Porgar, S.; Rahmanian, Nejat (2021-06-24)
      The thermal behavior of aluminium oxide-water nanofluid in a double pipe carbon steel heat exchanger was investigated in the present study. The overall heat transfer coefficient, Nusselt, and heat transfer coefficient of nanofluid were compared with the base fluid. The volume fraction of the nanoparticles was 1%. By adding nanoparticles to the fluid, the thermal properties of the base fluid improved significantly. The hot and cold fluid flow was considered counter-current, and the nanofluid was pumped into the inner tube and once into the outer tube, and the flow rate of each fluid was 0.05 kg/s. The convective heat transfer and the overall heat transfer coefficient enhanced 94% and 253% for the hot fluid flow in the outer tube and 308 % and 144% for the hot fluid flow in the inner tube, respectively. The pressure drop calculations also showed that the pressure drop would not change significantly when using nanofluid.
    • Investigation of the Growth of Particles Produced in a Laval Nozzle

      Zhalehrajabi, E.; Rahmanian, Nejat; Zarrinpashne, S.; Balasubramanian, P. (2014)
      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.
    • An investigation on process of seeded granulation in a continuous drum granulator using DEM

      Behjani, M.A.; Rahmanian, Nejat; Ghani N.F.b.A.; Hassanpour, A. (2017)
      Numerical simulation of wet granulation in a continuous granulator is carried out using Discrete Element Method (DEM) to discover the possibility of formation of seeded granules in a continuous process with the aim of reducing number of experimental trials and means of process control. Simple and scooped drum granulators are utilized to attain homogenous seeded granules in which the effects of drum rotational speed, particles surface energy, and particles size ratio are investigated. To reduce the simulation time a scale-up scheme is designed in which a dimensionless number (Cohesion number) is defined based on the work of cohesion and gravitational potential energy of the particles. Also a mathematical/numerical method along with a MATLAB code is developed by which the percentage of surface coverage of each granule is predicted precisely. The results show that use of continuous granulator is promising provided that a high level of shear is considered in the granulator design, e.g. it is observed that using baffles inside the drum granulators is essential for producing seeded granules. It is observed, moreover, that the optimum surface energy for scooped granulator with rotational speed of 50 rpm is 3 J/m2 which is close to the number predicted by Cohesion number. It is also shown that increasing the seed/fine size ratio enhances the seeded granulation both quantitatively (60% increase in seeds surface coverage) and qualitatively (more homogeneous granules).
    • Mathematical modelling and numerical simulation of CO2/CH4 separation in a polymeric membrane

      Gilassi, S.; Rahmanian, Nejat (2015-11-01)
      CO2 capture from natural gas was experimentally and theoretically studied using a dead-end polymeric permeation cell. A numerical model was proposed for the separation of CO2/CH4 using Polytetrafluoroethylene (PTFE) in a flat sheet membrane module and developed based upon the continuity, momentum and mass transfer equations. The slip velocity condition was considered to show the reflection of gas flow in contact with the membrane surface. The solution method was based on the well-known SIMPLE algorithm and implemented using MATLAB to determine the velocity and concentration profiles. Due to change in velocity direction in the membrane module, the hybrid differencing scheme was used to solve the diffusion-convection equation. The results of the model were compared with the experimental data obtained as part of this work and good agreement was observed. The distribution of CO2 concentration inside the feed and permeate chambers was shown and the velocity profile at the membrane surface was also determined using reflection factor for polymericmembrane. The modelling result revealed that increasing the amount of CO2 in gas feed resulted in an increase in the CO2 in the permeate stream while the gas feed pressure increased. By changing the permeability, the model developed by use of the solution-diffusion concept could be used for all polymeric membranes with flat sheet modules.
    • Mathematical modelling of performance and wear prediction of PDC drill bits: impact of bit profile, bit hydraulic, and rock strength

      Mazen, Ahmed Z.; Mujtaba, Iqbal M.; Hassanpour, A.; Rahmanian, Nejat (2020-05)
      The estimation of Polycrystalline Diamond Compact (PDC) cutters wear has been an area of concern for the drilling industry for years now. The cutter's wear has been measured practically by pulling the bit out for evaluation at the surface. It is important to find the right time for tripping out as this helps to avoid the fishing job and reduces the operational cost significantly. The prediction of the drilling performance is based on the interaction of cutter and rock. Several authors focused on the cutter-rock interface but only a few researchers tried to model the wear of the PDC bit cutters. The aim of this research is to understand the relationships between the rate of penetration (ROP) and the drilling variables per each foot, and then determine the overall bit efficiency for the whole drilling operation. A new mathematical model is derived to predict the PDC bit performance by considering the factors that were already not taken into account. These factors include rock strength, bit design, and bit hydraulic. The model investigates the effect of these parameters to estimate the abrasive cutters wear on the inner and the outer bit cones by deriving modified equations to calculate the mechanical specific energy (MSE), torque, and depth of cut (DOC) as a function of effective blades (EB). The model is used to forecast the bit cutters wear conditions in four wells in the oil fields located in Libya, which were drilled with three different PDC's sizes. The model enables the results to be compared to the actual bit cutters wear measured for inner and outer cones. The results are found that are well in agreement with the actual field data obtained in bit records.
    • Methyl lactate synthesis using batch reactive distillation: Operational challenges and strategy for enhanced performance

      Aqar, D.Y.; Rahmanian, Nejat; Mujtaba, Iqbal M. (2016-01-28)
      Batch reactive distillation is well known for improved conversion and separation of desired reaction products. However, for a number of reactions, the distillation can separate the reactants depending on their boiling points of them and thus not only reduces the benefit of the reactive distillation but also offers operational challenges for keeping the reactants together. Methyl lactate (ML) synthesis via the esterification of lactic acid (LA) with methanol in a reactive distillation falls into this category and perhaps that is why this process has not been explored in the past. The boiling points of the reactants (LA, methanol) are about 490 K and 337 K while those of the products (ML, water) are 417 K and 373 K respectively. Clearly in a conventional reactive distillation (batch or continuous) methanol will be separated from the LA and will reduce the conversion of LA to ML significantly. Here, first the limitations of the use of conventional batch distillation column (CBD) for the synthesis of ML is investigated in detail and a semi-batch reactive distillation (SBD) configuration is studied in detail where LA is the limiting reactant and methanol is continuously fed in excess in the reboiler allowing the reactants to be together for a longer period. However, this poses an operational challenge that the column has to be carefully controlled to avoid overflow of the reboiler at any time of the operation. In this work, the performance of SBD for the synthesis of ML is evaluated using model based optimization in which operational constraints are embedded. The results clearly demonstrate the viability of the system for the synthesis of ML.
    • A novel split-reflux policy in batch reactive distillation for the optimum synthesis of a number of methyl esters

      Aqar, D.Y.; Rahmanian, Nejat; Mujtaba, Iqbal M. (2019-08-15)
      The production of a number of methyl esters such as methyl decanoate (MeDC), methyl salicylate (MeSC), and methyl benzoate (MeBZ) by esterification reactions of several carboxylic acids such as decanoic acid (DeC), salicylic acid (ScA), and benzoic acid (BeZ) with methanol, respectively, through a reactive distillation system (batch or continuous) is cost-intensive and operationally challenging operation. It is difficult to keep the reaction species together in the reaction section due to wide boiling point differences between the reactants. Methanol (in those esterification processes) having the lowest boiling temperature in the reaction mixture can separate easily from carboxylic acid as the distillation progresses, resulting in a severe drop in the reaction conversion ratio of the acid employing batch/continuous distillation system. In order to overcome this type of challenge and to increase the overall reaction conversion, a novel split-reflux conventional batch reactive distillation configuration (sr-BRD) is proposed/studied in detail in this investigation. The optimal performance of BRD/ sr-BRD column is determined in terms of maximum achievable conversion of acids, and highest concentration of the esters produced for each chemical reaction scheme. The results for given separation tasks are compared with those obtained using conventional batch distillation (BRD) process. The optimization results clearly show that the sr-BRD process significantly improves the process efficiency, the conversion ratio of acid, and the product purity of methyl esters compared to that obtained via the BRD process.
    • Nucleation and Condensation Modeling of Metal Vapor in Laval Nozzle

      Zhalehrajabi, E.; Rahmanian, Nejat (2014)
      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 nano-particles 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.