Hassan Alfadala

Qatar University, Ad Dawḩah, Baladīyat ad Dawḩah, Qatar

Are you Hassan Alfadala?

Claim your profile

Publications (20)10.74 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents results from a preliminary study of the effectiveness of using inquiry-guided learning instructional strategies both in chemical engineering classrooms and laboratories. For readers unfamiliar with the instructional strategy, the paper describes the general approach and then reports on results of its application for the fluid mechanics course taken by undergraduate students in the Chemical Engineering Department at Qatar University. Inquiry-guided activities were developed after a series of interviews with recent chemical engineering graduates and employers to gather data on difficulties of chemical engineering graduates during the transition period from the university to industry. Some common daily problems were gathered, discussed, listed and used to formulate in an inquiry guided activity structure. Students were asked to participate in a role-play approach in which client-contractor relationship and rules of engagements were simulated. Both laboratory projects and in-class inquiry guided approach were conducted. Student performance and ability to approach conceptual problems and design-related issues were monitored and graded. Assessments were done after initial coverage of fundamentals of fluid mechanics (8 weeks into the course). Activities promoted in-class engagement and student performance was observed to enhance student performance and engagement to subject when compared to years at which the inquiry teaching methods were not used. This observation is observed to be valid for both with respect to conceptual approaches as well as design-related issues in the early stages of chemical engineering education.
    No preview · Article · Jan 2014 · International Journal of Engineering Education
  • M. M. Faruque Hasan · Iftekhar A. Karimi · Hassan E. Alfadala
    [Show abstract] [Hide abstract]
    ABSTRACT: Global concern about energy, ecology and environment strongly suggests that energy should be utilized efficiently. Although liquefied natural gas (LNG) is an attractive source of clean fossil fuel, it involves energy intensive liquefaction. Moreover, compressors are often operated in suboptimal fashion in the process, which results in higher energy consumption. The APCI propane precooled mixed refrigerant process is most widely used process in base-load LNG plants. To this end, we optimize the compressor operations for the twin refrigeration cycles of the APCI process. The objective here is to minimize the total power cost for the refrigerant compressors. We identify that the propane pressure in the propane precooling cycle plays a role for the power consumption in the compressors and hence use it as a decision variable. Without much loss of generality, this model could be also used for other LNG processes. Finally, we present a case study on an existing LNG plant model.
    No preview · Chapter · Dec 2009
  • M.M. Faruque Hasan · Iftekhar A. Karimi · Hassan E. Alfadala
    [Show abstract] [Hide abstract]
    ABSTRACT: Although multi-component phase changes are frequently present in petrochemicals, gas processing industries, cryogenic applications and chemical industries where distillation, stripping, etc., are common, most literature on heat exchanger network synthesis (HENS) assumes isothermal phase changes only. However, multi-component phase change occurs over a range of temperatures and the temperature–enthalpy (T-Q) relations are highly nonlinear. In such cases, isothermal approximations lead to suboptimal or even inaccurate networks. To this end, we present an MINLP model using a second order T-Q correlation that rigorously accounts for multi-component phase changes in HENS problem. It is shown that incorporating multi-component phase changing streams in the network reduces the total annualized cost of the network and improves the overall energy savings. In doing so, it is also possible for multi-component condensers and reboilers to become part of the plant-wide heat integration.
    No preview · Chapter · Dec 2009
  • [Show abstract] [Hide abstract]
    ABSTRACT: Multistream heat exchangers (MSHE) enable the simultaneous exchange of heat among multiple streams, and are preferred in cryogenic processes such as air separation and LNG. Most MSHEs are complex; proprietary and involve phase changes of mixtures. Although modeling MSHE is crucial for process optimization, no such work exists to our knowledge. We present a novel approach for deriving an approximate operational (vs. design) model from historic data for an MSHE. Using a superstructure of simple 2-stream exchangers, we propose a mixed-integer nonlinear programming (MINLP) formulation to obtain a HE network that best represents the MSHE operation. We also develop an iterative algorithm to solve the large and nonconvex MINLP model in reasonable time, as existing commercial solvers fail to do so. Finally, we demonstrate the application of our work on an MSHE from an existing LNG plant, and successfully predict its performance over a variety of seasons and feed conditions. © 2008 American Institute of Chemical Engineers AIChE J, 2009
    No preview · Article · Jan 2009 · AIChE Journal
  • Source
    Hassan E Alfadala · Essa Al-Musleh
    [Show abstract] [Hide abstract]
    ABSTRACT: Adopting a rigorous equilibrium stage model for simulating an amine-based Acid Gas Removal (AGR) process is not straightforward technique. It may also be a frustrating exercise in simulation. The complexity of the system is mainly attributed to the necessity of considering both chemical and phase equilibrium issues to characterize such an electrolytic system. This paper discusses an effective approach for simulating a Methyldiethanolamine (MDEA) system using Aspen Plus RadFrac equilibrium stage model. For thermodynamic modeling, the approach uses the electrolyte-NRTL model, Redlich-Kwong-Soave equation of state, and Henry's law. Component Vaporization efficiencies were incorporated in the simulation to account for the departure from equilibrium. To test its validity, the latter approach was tested against real design data obtained from a plant located in the State of Qatar. Furthermore, another process simulator namely ProMax and developed by Bryan Research and Engineering, Inc. was used for the purpose of comparison. Challenges faced during this practice (e.g., unit operation convergence, recycle convergence, etc.) and troubleshooting are also considered.
    Preview · Article · Jan 2009
  • [Show abstract] [Hide abstract]
    ABSTRACT: Most literature on the synthesis of heat exchanger networks via mathematical programming methods has dealt with phase changes by assuming nearly isothermal conditions. Many multicomponent phase changes of practical interest (e.g., those in sub-ambient processes) occur over ranges of temperatures and exhibit nonlinear temperature-enthalpy relations (T-H curve). In such cases, isothermal approximations may lead to inferior or unacceptable networks. In this article, we propose a mixed-integer nonlinear programming formulation and a solution algorithm to incorporate nonisothermal phase changes in heat exchanger network synthesis. We approximate the nonlinear T-H curves via empirical cubic correlations, and propose a procedure to ensure minimum temperature approach at all points in the exchangers. Our approach successfully solves two industry examples and shows promise for significant cost reductions when compared with existing processes. © 2009 American Institute of Chemical Engineers AIChE J, 2009
    No preview · Article · Jan 2009 · AIChE Journal
  • [Show abstract] [Hide abstract]
    ABSTRACT: Industrial cooling using seawater is a critical technology that results in one of the most profound environmental impacts on water quality and public health in Qatar and throughout the Arabian Gulf. The usage of chemical biocides to control growth of unwanted organisms leads to the discharge of enormous quantities of toxic and carcinogenic pollutants. These have a direct impact on aquatic life in the region which leads to subsequent impacts on the food chain. Additionally, there is a serious risk to human health, because the discharges are made to the same body of water used as a source of drinking water. The impact of seawater cooling becomes increasingly pronounced with the implementation of gas and chemical processing mega-projects in the industrial cities Ras Laffan and Mesaieed. The problem has been identified to be of national interest to the State of Qatar and research is underway to assess environmental impacts and identify remedial actions. This paper will report on progress in the development and application of a holistic approach to developing optimal strategies for addressing the environmental, technical, and economic issues of seawater cooling systems. Sponsored by the Qatar National Research Fund under the National Research Program scheme, the research initiative aims to provide the world with the implementation tools needed to address this problem. The project has six key aims: To develop quantitative techniques for predicting the reaction mechanisms, kinetics, and characteristics of biocides and their reaction products. To develop computational tools to predict the fate of biocides and their reaction products within the system as well as after release into the environment. To develop process optimization tools that can identify highly efficient operational strategies and retrofit design alternatives for the seawater cooling systems. To develop process integration tools that can identify highly efficient design alternatives for the industrial process that requires cooling. To conduct case studies that assess the environmental impact and optimize the operation of cooling water systems at the industrial cities of Ras Laffan and Messaieed in collaboration with the governmental and industrial project partners. To develop knowledge and problem solving capacities of decision-makers and practicing engineers in Qatar's government and industry through technology transfer and advanced training schemes. The project works towards the development of a scientific framework for sustainable strategies that address the environmental issues of seawater cooling, aid in developing sound regulatory policies, and describe short- and long-term implementation strategies.
    No preview · Conference Paper · Nov 2008
  • Hassan E Alfadala · GV Rex Reklaitis · Mahmoud M El-Halwagi

    No preview · Book · Jan 2008
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Recent growth in world-wide consumption of natural gas highlights its immense importance as a source of primary energy. Liquefied natural gas (LNG) is the most economic way to transport natural gas over long distances. Main Cryogenic Heat Exchanger (MCHE) is a very critical equipment in an energy intensive LNG plant. To that end, modeling MCHE is the inevitable first step in the optimization of LNG plant operation. In this paper, we develop a model that is designed to simulate and predict the performance of an existing MCHE without knowing its physical details. The concept of superstructure representation is employed to derive an equivalent 2-stream heat exchanger network. The objective is to address the rating of an existing MCHE or the prediction of its performance rather than finding the area for a design or minimizing the cost. We use a mixed-integer nonlinear programming (MINLP) approach to select the best network that describes an existing MCHE. An example case is also presented to assess the ability of our model in predicting the performance of a MCHE. 2 M. M. F. Hasan et al.
    Preview · Article · Dec 2007 · Computer Aided Chemical Engineering
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Liquefied natural gas (LNG) is increasingly becoming an attractive alternate for crude oil and its usage is expected to grow tremendously in the coming years. Liquefaction of natural gas is a highly energy-intensive process. Because of its cryogenic nature, vapors called as boil-off gases (BOG) are generated at various places in an LNG plant due to heat leak, vapor displacement, flashing, and hot contact. The BOG from storage tanks, called as tankage BOG is usually compressed and exported to the plant fuel system. However, in some LNG plants, there exists another source of BOG; the one from intermittent loading, called as jetty BOG. As plant capacities grow and economic efficiency becomes important, it makes sense to integrate the jetty BOG optimally into the existing fuel gas network. We propose a novel superstructure and nonconvex mixed-integer nonlinear program for addressing this problem. An industrially based case study showed that our approach is efficient and practically useful.
    Full-text · Conference Paper · Jun 2007
  • Farouq S Mjalli · S Al-Asheh · H E Alfadala
    [Show abstract] [Hide abstract]
    ABSTRACT: A reliable model for any wastewater treatment plant is essential in order to provide a tool for predicting its performance and to form a basis for controlling the operation of the process. This would minimize the operation costs and assess the stability of environmental balance. This process is complex and attains a high degree of nonlinearity due to the presence of bio-organic constituents that are difficult to model using mechanistic approaches. Predicting the plant operational parameters using conventional experimental techniques is also a time consuming step and is an obstacle in the way of efficient control of such processes. In this work, an artificial neural network (ANN) black-box modeling approach was used to acquire the knowledge base of a real wastewater plant and then used as a process model. The study signifies that the ANNs are capable of capturing the plant operation characteristics with a good degree of accuracy. A computer model is developed that incorporates the trained ANN plant model. The developed program is implemented and validated using plant-scale data obtained from a local wastewater treatment plant, namely the Doha West wastewater treatment plant (WWTP). It is used as a valuable performance assessment tool for plant operators and decision makers. The ANN model provided accurate predictions of the effluent stream, in terms of biological oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solids (TSS) when using COD as an input in the crude supply stream. It can be said that the ANN predictions based on three crude supply inputs together, namely BOD, COD and TSS, resulted in better ANN predictions when using only one crude supply input. Graphical user interface representation of the ANN for the Doha West WWTP data is performed and presented.
    No preview · Article · Jun 2007 · Journal of Environmental Management
  • Sameer Al-Asheh · Farouq Sabri Mjalli · Hassan E. Alfadala
    [Show abstract] [Hide abstract]
    ABSTRACT: We consider the problem of predicting the future behavior of wastewater treatment plant quality indicators by creating prediction models using historical plant data. One of the main aims of this work is to be able to predict plant operational situations in advance so that corrective actions can be taken in time. Sets of historical plant data, such as BOD, COD and TSS were collected for a local wastewater treatment plant in Doha, the capital of the State of Qatar. These variables characterize the performance of any wastewater treatment plant and can be considered as quality indicators of the plant performance. Data were collected over a period of 4 years for the influent and effluent streams of the station. The plant influent and effluent predictions were performed using different techniques. These include time-series analysis, where the ARIMA (Autoregressive Integrated Moving Average) model was implemented in this case, and two Artificial Neural Networks (ANN) algorithms, namely Adaptive Linear Neuron networks (ADALINE) and Multi-layer Feedforward (ML-FF) neural networks. The predictions from the three techniques were presented and compared. The ML-FF model predictions proved to be more reliable than that of the equivalent ARIMA predictions followed by the ADALINE predictions, particularly for the finial effluent stream variables. Copyright © 2007 The Berkeley Electronic Press. All rights reserved.
    No preview · Article · Jan 2007 · Chemical Product and Process Modeling
  • Source
    Maryam Zargarzadeh · Iftekhar A Karimi · Hassan Alfadala
    [Show abstract] [Hide abstract]
    ABSTRACT: Exergy analysis is important and has been widely used to evaluate the thermodynamic efficiency of a variety of processes. Therefore, there is a need to develop a tool for monitoring exergy of a process in real-time and for studying the effects of various feed, equipment, process and environmental changes. The ultimate aim of this work is to develop a tool to enable dynamic and online exergy analysis in an interactive manner at various levels of equipment, process, and plant. However, in this paper, we develop methods for the online analysis of exergy in various units of a base-load liquefied natural gas (LNG) process.
    Full-text · Article · Jan 2007
  • Source
    Hassan E. Alfadala · Bilal M. Ahmad · Abdulla F. Warsame
    [Show abstract] [Hide abstract]
    ABSTRACT: The objective of this paper is to optimize the thermal performance of a fractionation unit within a liquefied natural gas (LNG) facility. Typical fractionation units in an LNG facility consisting of three distillation columns, namely de-ethanizer, de-propanizer and de-butanizer were used in this study. A hierarchical approach is developed to optimizing the system. In this approach, increasing levels of model complexity are used and various thermal targets are set and implemented. The column targeting tool available within the simulation package of Aspen Plus© software was used to optimize a fractionation unit in an LNG facility. First, integrated thermal analysis was used in identifying design targets for improvements in energy consumption and efficiency. The column targeting tool is used in the design of distillation columns by setting targets to reduce utility cost, improve energy efficiency, reduce capital investment and facilitate column debottlenecking. Starting from a short-cut distillation design calculation using the DSTWU method which is based on the well-known Fenske-Underwood-Gilliland correlations, the minimum and actual reflux ratios, minimum and actual number of stages, optimum feed location and condenser and reboiler duties were estimated. These estimates were used as starting points in the rigorous fractionation column design method RADFRAC available in Aspen Plus©. The column Grand Composite Curve (CGCC) for each column was generated to give an insight of the actual operation and guide the optimization process. Starting with appropriate feed placement, the CGCC will show the scope for reflux ratio modification by increasing the number of stages. Feed would be either preheated or precooled due to the availability of sharp enthalpy change in the condenser or reboiler side. Finally, the scope for a side condensing or side reboiling can be identified from the area beneath or above the CGCC pinch point.
    Preview · Article · Jan 2005 · Computer Aided Chemical Engineering
  • H. E. Alfadala · A. K. Sunol · M. M. El-Halwagi
    [Show abstract] [Hide abstract]
    ABSTRACT: A systematic procedure for the retrofitting of mass-exchange networks (MENs) with temperature effects is developed. Alternative structural configurations of interest are examined, and both series and parallel structures are discussed. Two primary retrofitting strategies are employed: those restricted by no-capital constraints and those involving capital expenditure. The no-capital alternatives include enhancing the performance of current system and solvent substitution. The capital-based alternatives include the addition of new equipment. A new type of temperature-based mass-pinch retrofitting analysis is developed to maximize the utilization of existing capital while reconciling added capital with operating cost. The main concept in this novel pinch diagram is identifying maximum performance as dictated not only by thermodynamic limitations but also by physical­-size limitations. Different process alternatives are considered and screened to attain the optimum design.
    No preview · Article · Dec 2001 · Computer Aided Chemical Engineering
  • H. E. Alfadala · A. K. Sunol · M. M. El-Halwagi
    [Show abstract] [Hide abstract]
    ABSTRACT:  The synthesis of optimal mass exchange networks (MENs) deals with the identification of a cost-effective network of mass exchangers that preferentially transfer certain species from rich streams to lean streams. To date, MEN synthesis has dealt with grass-root design where the emphasis is on the maximization of process lean streams usage and the minimization of operating cost. Another important class of problems is the retrofit of MENs in which mass-exchange units already exist in the plant and the focus is to maximize the usage of the process units so as to minimize capital cost of newly added units and trade it off with operating cost. In this paper, we develop a systematic procedure for the retrofitting of MENs. First, we identify alternative structural configurations of interest through heuristics. Series and parallel structures are addressed. Next, we focus on two primary retrofitting strategies: those restricted by no capital constraints and those involving capital expenditure. The no-capital alternatives include enhancing performance of a current system as well as solvent substitution. The capital-based alternatives include the addition of new equipment. A new type of mass-pinch analysis is developed to maximize the utilization of existing capital while reconciling added capital with operating cost. The main concept in this novel pinch diagram is identifying maximum performance as dictated not only by thermodynamic limitations but also by physical size limitations. Different process alternatives are considered and screened to attain the optimum design. A case study is presented to demonstrate the broad applicability and potential benefits of the novel approach.
    No preview · Article · Jan 2001 · Clean Technologies and Environmental Policy
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Hydrogen sulfide (H2S) is considered as one of the most noxious industrial gases. Its removal from natural gas is particularly required for reasons of health, odour problems, safety and corrosivity problems. H2S causes an irritating, rotten egg smell in concentrations above 1ppm, and at concentrations above 10ppm the toxicological exposure limits are exceeded. Many methods have been developed over the years for the removal of H2S from gaseous emissions. H2S removal, with subsequent sulphur recovery, is at present mostly preferred using a train of Claus process, Tail Gas Treating Unit and Amine Treating Unit. Some of the disadvantages of these methods for gas treatment are that they require relatively large investment and operational costs (e.g. special chemicals, equipment corrosion, high pressures and temperatures) and they require special operational safety and health procedures. Continual search for more economical removal methods has led to investigations into microbiological solutions for H2S removal. One of the most common technologies for biological treatment of sour gas is the THIOPAQ TM process. It removes H2S from gaseous streams by absorption into a mild alkaline solution followed by oxidation of the absorbed sulfide to elemental sulphur by naturally occurring micro organisms. On the other hand, the Shell Claus Off- gas Treating (SCOT) process can be viewed as the industry standard classical process for small scale gas treatment. The purpose of this study is to simulate the biological oxidation of H2S gas process (THIOPAQ TM ) and SCOT process using the software HYSYS. In addition, these processes are compared qualitatively and quantitatively in terms of economic considerations. The comparison revealed that the biological process is safe, simple, and is cost competitive with respect to the SCOT process
    Full-text · Article ·
  • Source
    Saad A Al-Sobhi · Hassan E Alfadala · Mahmoud M El-Halwagi
    [Show abstract] [Hide abstract]
    ABSTRACT: The global use of natural gas is growing rapidly. This is primarily attributed to the environmental advantages it enjoys over other fossil fuels such as oil and coal. One of the key challenges in supplying natural gas is the form (phase) at which it should be delivered and according to the cost-benefit analysis for each delivery method. Natural gas may be supplied to the consumers as a compressed gas through pipelines and as hydrates delivered in special containers. Another common form is to be compressed, refrigerated and supplied as a liquid known as liquefied natural gas (LNG). When there is a considerable distance involved in transporting natural gas, LNG is becoming the preferred method of supply because of technical, economic, safety, and political reasons. Thus, LNG is expected to play a major role in meeting the global energy demands. This paper addresses the simulation and optimization of an LNG plant. First, the process flowsheet is constructed based on a typical process configuration. Then, the key units are simulated using ASPEN Plus to determine the characteristics of the various pieces of equipment and streams in the plant. Next, process integration techniques are used to optimize the process. Particular emphasis is given to energy objectives through three activities. First, the synthesis and retrofitting of a heat-exchange network are considered to reduce heating and cooling utilities. Second, the turbo-expander system is analyzed to reduce the refrigeration consumption in the process. Third, the process cogeneration is introduced to optimize the combined heat and power of the plant. These activities will be discussed in details at future publications. A case study on a typical LNG facilities is solved to examine the benefits of simulation and integration of the process. The technical, economic, and environmental impact of the process modifications are also discussed.
    Full-text · Article ·
  • Source
    Ahmed Abdel-Wahab · Patrick Linke · Hassan Alfadala
    [Show abstract] [Hide abstract]
    ABSTRACT: Industrial cooling using seawater is a critical technology that results in one of the most profound environmental impacts on water quality and public health in Qatar and throughout the Arabian Gulf. The usage of chemical biocides to control growth of unwanted organisms leads to the discharge of enormous quantities of toxic and carcinogenic pollutants. These have a direct impact on aquatic life in the region which leads to subsequent impacts on the food chain. Additionally, there is a serious risk to human health, because the discharges are made to the same body of water used as a source of drinking water. This paper will report on progress in the development and application of a holistic approach to developing optimal strategies for addressing the environmental, technical, and economic issues of seawater cooling systems. Sponsored by the Qatar National Research Fund under the National Research Program scheme, the research initiative aims to provide the world with the implementation tools needed to address this problem.
    Full-text · Article ·
  • C. Shene · C. Diez · S. Bravo · S. Alasheh · F.S. Mjalli · H.E. Alfadala

    No preview · Article ·