Mansour Emtir

Libyan Petroleum Institute, Chemical industry, Chairman

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Papers by Mansour Emtir

Rigorous optimization of heat-integrated and Petlyuk column distillation configurations based on feed conditions

Clean Technologies and Environmental Policy, Oct 1, 2008

The steady-state design and rigorous simulation of conventional distillation configurations and s... more The steady-state design and rigorous simulation of conventional distillation configurations and several energy-integrated configurations has been studied for ternary mixture separation. The studied configurations are optimized rigorously based on total annual cost as the economic objective function. The energy-integrated distillation configurations are compared with conventional configurations to find the maximum achievable total annual cost savings. Changing feed conditions is considered as one of the optimization variables by investigating different states of feed conditions; feed at 15.5 °C temperature, liquid at bubble point and vapor at dew point. The investigated configurations are conventional direct and indirect separation sequence, heat-integrated direct sequences, Petlyuk column, heat-integrated sloppy sequence, and double heatintegrated sloppy sequence. Optimization results indicate that saving in energy and total annual cost of the configurations is affected by the states of the feed conditions.

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Performance Improvement of Gas Sweetening Units by Using a Blend of MDEA/PZ

DOAJ (DOAJ: Directory of Open Access Journals), Jun 1, 2021

This work investigates three gas sweetening units in Libya; particularly, Mellitah complex, Alest... more This work investigates three gas sweetening units in Libya; particularly, Mellitah complex, Alestiklal, and Sahel gas plant. These units are designed mainly to use Methyl diethanolamine (MDEA) as a solvent for the removal of H 2 S and CO 2 from the raw gas. Thus, the handling of higher gas production rates for the forthcoming years is a bottleneck without being upgraded. This work aims to increase throughput and reduce operating costs while maintaining the product quality of these units. HYSYS simulation was used to simulate the processes, assess the potential advantages of using a blend of MDEA and Piperazine (PZ), and investigate important parameters in the process. Results show that the MDEA/PZ blend provides high-performance as a gas treating solvent. The raw gas flow rate can be increased from 16,208 kmol/h to 18,820 kmol/h in the Mellitah complex with specs of 1.98 vol % CO 2 and 0.9915 ppm H 2 S. In the Alestiklal gas plant, the flow rate can be increased from 8,012.79 kmol/h to 8,750 with specs of 0.975 Mole % CO 2. But Sahel gas plant had a different behaviour, where the addition of Piperazine led to deviation of H 2 S from the required specification. The value of H 2 S reached 25.944 ppm, and the percent of CO 2 was 1.347 Mole %. However, the decrease of the amine temperature reduces H 2 S to 13.76 ppm and CO 2 to 1.276 Mole %. These results demonstrate the potential for significant improvements in increasing throughput via the use of PZ as an activator to the MDEA.

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Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction

Energy Integration and Reactive Distillation for Dimethyl Ether Synthesis via Catalytic Dehydration of Methanol

Distillation is the most widely used separation technique in the process industry. Its main disad... more Distillation is the most widely used separation technique in the process industry. Its main disadvantage is the high consumption of thermal energy: the heat requirements of the distillation columns often represent most part of the total energy cost of the plant, appropriate integration of the distillation columns with the overall process often results in a significant reduction of the energy consumption in many cases. In this work the concept of the integration has been applied by two integrated design approaches:  Heat-integrated design; where the distillation system of the process will be heat-integrated with the background process (i.e. integration between the distillation columns and the heat exchangers).  Reactive distillation design; where the reaction and distillation will be accomplished in the same unit. The process of dimethyl ether (DME) synthesis by the catalytic dehydration of methanol has been considered as a case study. Heat-integrated design of DME process showed a...

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Performance Analysis of Batch Reactive Distillation Column using Different Measures

Chemical Engineering Transactions, 2015

Batch distillation with chemical reaction when takes place in the same unit is referred to as bat... more Batch distillation with chemical reaction when takes place in the same unit is referred to as batch reactive distillation process. The combination reduces the capital and operating costs considerably. Among many different types of batch reactive distillation column configurations, conventional (CBRD) and middle vessel batch reactive distillation (MVBRD) columns are considered here for hydrolysis of methyl lactate and only CBRD is considered for an esterification of acetic acid and ethanol. Three different measures such as Maximum Profit under Fixed Demand (Measure 1), Maximum Productivity (Measure 2) and Minimum batch time (Measure 3) are used here to evaluate the performances of different columns. Optimal design and or operation policies are obtained under these measures and are compared. A detailed rigorous dynamic model consisting of mass, energy balances, chemical reaction and thermodynamic properties is used for evaluating the column performance.

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Shortcut model for predicting refrigeration cycle performance

Compression refrigeration systems are very widely used to provide cooling to sub-ambient processe... more Compression refrigeration systems are very widely used to provide cooling to sub-ambient processes. The power demand of the cycle depends strongly on the temperature at which cooling is required, the temperature at which the refrigerant is condensed, as well as the type of refrigerant being used. At lower temperatures (typically lower than -40 �C), complex refrigeration schemes, such as cascaded refrigeration cycles, may be needed, increasing the complexity of the models used to predict the power requirements for a given cooling demand. This work proposes a simple model for predicting the power consumption of such complex cycles, based on regression of more rigorous process simulation models. A simple linear refrigeration model which relates the actual power demand of a refrigeration cycle to the ideal performance (i.e. the Carnot cycle) is developed. The model predicts the power demand prior to design of the refrigeration scheme given the condensing and evaporation temperatures of ...

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Comparison of integrated and coupled distillation schemes using different utility prices

Computers & Chemical Engineering, 1999

Separation of a ternary mixture by different distillation schemes was simulated rigorously at ste... more Separation of a ternary mixture by different distillation schemes was simulated rigorously at steady state. Conventional schemes, heat integrated schemes, and the fully thermally coupled structure (Petlyuk system) have been optimized over total annual cost including two different regional utility price systems (high and low utility prices): The results show that price ratios have considerable effect on the savings and consequently on the optimal schemes. Using low utility price the number of actual trays is reduced and the reflux ratios will be increased. At extreme high utility prices the Petlyuk system can be justified as one of the best schemes in savings, but not against the sloppy forward heat integrated scheme. The maximum savings in total annual cost in both cases are about 28%.

Energy savings of integrated and coupled distillation systems

Computers & Chemical Engineering, 2001

Based on theoretical considerations and economically evaluated case studies for ternary mixtures ... more Based on theoretical considerations and economically evaluated case studies for ternary mixtures it is demonstrated that the Petlyuk configuration and the dividing wall column scheme are not superior to the energy integrated configurations even in energy savings. Generally we can state that the sloppy separation path with external energy integration is always capable of achieving as much energy savings as that of the direct column coupling configurations. Short-cut estimation for the exergy losses is also outlined. This estimation prefers exergically the direct coupling in some areas but detailed studies do not confirm this result.

Challenges in controllability investigations of chemical processes

Computer Aided Chemical Engineering, 2003

The controllability investigation of any kind of chemical process is the interactive and challe... more The controllability investigation of any kind of chemical process is the interactive and
challenging part of process design or development. The investigation works on several
levels and uses different methods. First, the control targets are defined, the set of
controlled variables are determined and the set of possible manipulated variables are
selected. The proper pairing of the controlled and manipulated variables, that is the
design of the control structure, consists of first, the study of steady state control indices
and then dynamic behaviours in the cases of open and closed control loops of the
promising control structures. This investigation is presented on the design of energy
integrated separation schemes.
A new challenging method is offered by the Rough Set Theory (RS), which has been
already successfully used in several areas of artificial intelligence and data analysis e.g. for the discovery of patterns and dependencies in data. Its use for controllability
investigations is a new area at the revision of control structures of existing plants,
retrofit modifications, because it can detect the dependencies among the possible
controlled and manipulated variables with the analysis of the measured data and helps to fulfill the requirements of the control target. RS theory indicates also the measure of the dependencies among the variables.
The RS theory is used for the improvement of the control structure of a complex
chemical process, which is the fluid catalytic cracking unit (FCC). The analysis of the
data of existing FCC unit shows that the product quality significantly depends on the
temperature in the re-generator unit and its control is necessary. After considering the
degrees of freedom, a new control loop is designed for the proper control of the
temperature in the re-generator unit, which is accepted by the industry and it will be
included in the control structure of the FCC plant.

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The Using of Mixing Amines in an Industrial Gas Sweetening Plant

Abstract—Natural gas is defined as gas obtained from a natural underground reservoir. It generall... more Abstract—Natural gas is defined as gas obtained from a natural underground reservoir. It generally contains a large quantity of methane along with heavier hydrocarbons such as ethane, propane, isobutene, normal butane; also in the raw state it often contains a considerable amount of non hydrocarbons, such as nitrogen and the acid gases (carbon dioxide and hydrogen sulfide). The acid gases must be removed from natural gas before use. One of the processes witch are use in the industry to remove the acid gases from natural gas is the use of alkanolamine process. In this present paper, a simulation study for an industrial gas sweetening plant has been investigated. The aim of the study is to investigate the effect of using mixing amines as solvent on the gas treatment process using the software Hysys. Keywords—Natural gas, alkanolamine process, gas sweetening plant, simulation, mixing amines I.

Optimal Operation of Batch Reactive Distillation Process Involving Esterification Reaction System

Chemical engineering transactions, 2015

The performance of batch reactive distillation process involving the esterification of acetic aci... more The performance of batch reactive distillation process involving the esterification of acetic acid with methanol to produce methyl acetate and water is considered in this work. Two cases studies with varying amount of the reactants are considered. The reflux ratio (single time interval) is selected as the control variable to be optimised (treated as piecewise constant) for different but fixed batch time ranging from 5 to 15 h, so as to maximise the conversion of methanol subject to product purity of methyl acetate. The dynamic optimisation problem is converted to a nonlinear programming problem by Control Vector Parameterization (CVP) technique and is solved by using efficient SQP method. The optimisation results show that as the methanol and methyl acetate are wide boiling, the separation of methyl acetate is easier without losing much of methanol reactant. The conversion improves by 6.4 % due to sufficient amount of acetic acid being reacted with methanol. Moreover an excess of ac...

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The Effect of vibration on the absorption of CO2 with chemical reaction in aqueous solution of

calcium hydroxide.

Economic and controllability investigation and comparison of energy-integrated distillation schemes

Chemical and Biochemical Engineering Quarterly, 2003

Five different energy-integrated distillation schemes: two direct sequences with forward or backw... more Five different energy-integrated distillation schemes: two direct sequences with forward or backward heat integration (DQF, DQB), the Petlyuk or dividing wall system (SP), and two sloppy separation sequences with forward or backward heat integration (SQF, SQB) are investigated for the separation of a ternary mixture from economic and controllability points of view and compared to the non-integrated conventional direct separation scheme. The economic study shows that the optimal DQB has the highest total annual cost (TAC) saving: 37%. SQF and SQB have 34% and 33% TAC savings, respectively. The controllability analysis, based on steady state indices, shows that the control loops of DQF and DQB have less interactions than in the case of the other energy-integrated schemes studied. The dynamic investigations also prove that DQF and DQB show similar controllability features than the non-integrated conventional scheme. Although the SQF and SQB have good economic features but their control...

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Improving Conventional Distillation Configuration for Ternary Mixtures Separation

Chemical engineering transactions, 2007

Rigorous simulations at steady-state are conducted for the separation of two different ternary mi... more Rigorous simulations at steady-state are conducted for the separation of two different ternary mixtures by conventional distillation with direct and indirect separation sequence. The studied chemical systems are (ethanol/n-propanol/n-butanol) and (benzene/toluene/m-xylene) with 99 mol % products purity at different feed compositions: (45/10/45), (33.3/33.3/33.3), and (10/80/10). In order to reduce the remixing effects in the first column a sidedraw stream is introduced at peak point composition of middle component as transfer stream to the second column. Economic optimization is carried out for the conventional and improved configurations based on energy consumption and total annual cost (TAC) as the objective function. The results indicate that improvements of thermodynamic performance of both columns are achievable and the maximum TAC saving is 29 % in case of indirect sequence and 19 % for direct sequence at low concentration of middle component.

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Performance of esterification system in reaction-distillation column

In this work a comparative study of the performance of conventional and unconventional (semi-batc... more In this work a comparative study of the performance of conventional and unconventional (semi-batch configuration) batch reactive distillation column is presented for esterification reaction of ethanol and acetic acid to produce ethyl acetate (main product) and water. Dynamic optimisation problem is formulated to maximise the conversion of ethanol to ethyl acetate subject to product purity constraints for different amount of feed reactants while optimising reflux ratio of operation for conventional operation and both reflux ratio and the amount of acetic acid feed rate for the semi-batch operation. Flooding condition has been added as a constraint to the semi-batch operation. It is found that there are cases when semi-batch operation can be more effective in maximising the conversion.

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Profitability Analysis for Batch Reactive Distillation Process Based on Fixed Product Demand

Chemical engineering transactions, 2009

Profit maximisation for batch reactive distillation process involving ethanol esterification reac... more Profit maximisation for batch reactive distillation process involving ethanol esterification reaction was conducted in this work using optimisation technique. The optimisation parameters considered are: vapour load (V) reflux ratio (R) and batch time (tb). Here, two cases were considered. In Case 1 the feed is composed of only the reactants (pure feed) and in Case 2 the feed is composed of reactants as well as a small fraction of one of the reaction products (diluted feed). The profit is maximised with fixed product demand ranging from 800 to 1200 kmol/year. For Case 1, the sensitivity of raw materials and or product prices is also investigated. For a given product demand, the optimization results show that, operating with Case 2 is always more profitable compared to the Case 1. This is due to low cost diluted feed and significant change in design and operation for Case 2 compared to Case 1. Also, changes in feed/product prices lead to different design and operation as well as produ...

The Effect of Product Purity on Controllability Analysis of Distillation Column

In this paper a controllability estimations of conventional direct sequence distillation column i... more In this paper a controllability estimations of conventional direct sequence distillation column in steady-state modes are studied for the separation of five different chemical systems at 99 and 95 mol % purity to obtain the best control configuration for controlled and manipulated variables based on steady-state control indices measurements. The following controllability indices are used to screen the best controllability features: The Niederlinski index (NI), the Morari resiliency (MRI), the relative gain array (RGA) and the condition number (CN). This study proved that for many different chemical systems of distillation process and at a certain product purity, the optimum control structure is found to be (D1-L2-B2) for 99% purity and (L1-L2-Q2) for 95 % purity based on steady state control indices criteria.

Optimization of Conventional and Energy-integrated Distillation Configurations at Different Feed Conditions

Chemical engineering transactions, 2007

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The Effect of Vibration on the Absorption of CO2 with Chemical Reaction in Aqueous Solution of Calcium Hydroxide

World Academy of Science, Engineering and Technology, International Journal of Chemical, Molecular, Nuclear, Materials and Metallurgical Engineering, 2007

interesting method to produce calcium carbonate is based in a gas-liquid reaction between carbon ... more interesting method to produce calcium carbonate is based in a gas-liquid reaction between carbon dioxide and aqueous solutions of calcium hydroxide. The design parameters for gas-liquid phase are flow regime, individual mass transfer, gas-liquid specific interfacial area. Most studies on gas-liquid phase were devoted to the experimental determination of some of these parameters, and more specifically, of the mass transfer coefficient, k L a which depends fundamentally on the superficial gas velocity and on the physical properties of absorption phase. The principle investigation was directed to study the effect of the vibration on the mass transfer coefficient k L a in gas-liquid phase during absorption of CO 2 in the in aqueous solution of calcium hydroxide. The vibration with a higher frequency increase the mass transfer coefficient k L a, but vibration with lower frequency didn't improve it, the mass transfer coefficient k L a increase with increase the superficial gas velocity.

Maximizing the Benefits of Refinery Residue Upgrading

The refining process separates, breaks, reshapes and recombines the molecules of crude oil into v... more The refining process separates, breaks, reshapes and recombines the molecules of crude oil into value-added products such as gasoline, diesel and aviation fuel. There is not one single upgrading solution that fits all refineries. Changing configurations in fuel demand, the trends to processing heavier crudes and increasing refinery complexity, and the growing globalization and trade in refined fuels, have introduced new dynamics to the economics of refining, and have shifted the drivers of refinery profitability. Refineries are classified according to the number of processes available for transforming crude into petroleum products. Simple refineries are designed to distil crude oil into a limited range and yield and products. They are referred to as topping or hydro-skimming plants. Topping is the most basic distillation process. Hydro-skimming involves distillation in the presence of hydrogen. Complex refineries involve a combination of interrelated processes to produce a broader r...

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