| 1. |
- Kamel, Dina A., et al.
(författare)
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Temperature driving force (TDF) curves for heat exchanger network retrofit - A case study and implications
- 2017
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Ingår i: Energy. - : Elsevier BV. - 0360-5442. ; 123, s. 283-295
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Tidskriftsartikel (refereegranskat)abstract
- In the present contribution, concepts supporting a new analysis method to retrofit heat exchanger networks (HENs) are presented. The new graphical representation appears to be simple to use and needs no simulation tools or software packages to perform the retrofit calculations and is found valuable for conceptual applications. The temperature driving force new representation (TDF) is accordingly applied to an existing HEN in an Egyptian refinery to boost its energy efficiency and generate cost-effective opportunities. This refinery is the most recent unit installed in Egypt as it has been built in 1994. Since this refinery is very modern, its energy consumption exceeds the benchmark by only 21.5% which is relatively very low compared to its counterparts worldwide. The graphical revamping in application applied on the HEN shows savings of approximately 10.5% in the energy demand with minor structural modifications, achieving some 60% of the potential energy savings with respect to Pinch Analysis benchmarks. The modified preheat train only exceeds the benchmark by 8.8%. Implications and advantages of the new developed approach are also discussed, highlighting the merits of the proposed method.
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| 2. |
- Abdelaziz, Omar Y., et al.
(författare)
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Novel process technologies for conversion of carbon dioxide from industrial flue gas streams into methanol
- 2017
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Ingår i: Journal of CO2 Utilization. - : Elsevier BV. - 2212-9820. ; 21, s. 52-63
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Tidskriftsartikel (refereegranskat)abstract
- This research aims to develop efficient process technologies that are capable of converting/utilising CO2 streams into energy-rich liquid products (fuels). This would result in better solutions with near-zero-carbon-emissions level. From an energetic and economic point of view, methanol synthesis from CO2 is a competitive alternate to methanol production from biomass. Our work considers the CO2 balance for the technologies proposed, taking into account all CO2 flows from/to the environment. Flue gas CO2 streams released from electric power stations, steel industry, petroleum industry, and cement industry are good candidates for the developed technologies. Three new processes are developed and modelled for converting CO2 streams into liquid methanol. The total cost of equipment and utility for all process scenarios are evaluated and compared. The energy targets as well as the CO2 emissions (balance) are determined. Heat integration is performed on the best selected process technology. The case study employed for the present work is a power station plant burning natural gas for electricity production with a capacity of 112 MW, releasing 328 t/h flue gases to the atmosphere, of which CO2 gas accounts for 14%; hydrogen required for CO2 conversion comes from the chlor-alkali industry. The optimum process technology reached in this contribution results in methanol production of 0.625 t-per-tonne of CO2 waste gas supply, leading to an annual production of 222,507 tons methanol with a profit of 56.55 M$/y. Thus, the CO2 release to the environment is cut by about 62%.
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| 3. |
- Ali, Dalia A., et al.
(författare)
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Co-gasification of coal and biomass wastes in an entrained flow gasifier: Modelling, simulation and integration opportunities
- 2017
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Ingår i: Journal of Natural Gas Science and Engineering. - : Elsevier BV. - 1875-5100. ; 37, s. 126-137
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Tidskriftsartikel (refereegranskat)abstract
- Gasification processes convert carbon-containing material into syngas through chemical reactions in the presence of gasifying agents such as air, oxygen, and steam. Syngas mixtures produced from such processes consist mainly of carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2), and methane (CH4); this gas can be directly utilised as a fuel to produce electricity or steam. Besides, it is regarded as a basic feedstock within the petrochemical and conventional refining industries, producing various useful products like methanol, hydrogen, ammonia, and acetic acid. In this work, a rigorous process model is developed to simulate the co-gasification of coal-biomass blends through an entrained flow gasifier. The proposed model is tested originally for American coal. The model validation is made against literature data and results show good agreement with these practical data, providing a robust basis for integration and retrofitting applications. Effects of critical parameters, comprising gasification temperature, steam/O2 ratio, and feedstock variability on the syngas composition and gasifier efficiency are studied. The developed model is further applied in a project to revamp an existing Egyptian natural gas-based power plant, replacing its standard fuel with coal-rice straw blends. The revamping project integrates the existing plant with a gasification unit burning a blend of coal and rice straw to replace the conventional fuel used. The feedstock used constitutes a dry Egyptian coal and a coal-rice straw blend (10 wt% rice straw), gathered locally. Different blending scenarios are investigated and the best performance is achieved with coal to rice straw ratio of 90:10 on weight basis, attaining 85.7% cold gas efficiency and significant economic savings. Results showed that the total annualised cost of the revamped process decreased by 52.7% compared with a newly built integrated gasification combined cycle (IGCC) unit.
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| 4. |
- Ali, Dalia A., et al.
(författare)
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Modelling of coal-biomass blends gasification and power plant revamp alternatives in Egypt's natural gas sector
- 2016
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Ingår i: Chemical Engineering Transactions. - 2283-9216. - 9788895608426 ; 52, s. 49-54
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Bokkapitel (refereegranskat)abstract
- Recently, there has been a growing research interest in the co-gasification of biomass with coal to produce syngas and electricity in a sustainable manner. Co-gasification technology do not only decrease potentially the exploitation of a significant amount of conventional coal resources, and thus lower greenhouse gases (GHG) emissions, but also boost the overall gasification process efficiency. In the present work, a rigorous simulation model of an entrained flow gasifier is developed using the Aspen Plus® software environment. The proposed simulation model is tested for an American coal and the model validation is performed in good agreement with practical data. The feedstocks used in the proposed gasifier model are dry Egyptian coal and a blend of an Egyptian coal and rice straw that is gathered locally. The proposed gasifier model mainly consists of three reactors. The first one is a yield reactor where the coal pyrolysis occurs, the second reactor is a stoichiometric reactor where the gasification reactions arise, and the third reactor is a Gibbs reactor where the water-gas and steam-methane reforming reactions take place. The influence of using a feed mixture of 90 % coal and 10 % rice straw on the gasifier efficiency is investigated. The developed model provides a robust basis for revamping of an existing Egyptian natural gas-based power plant to replace its standard fuel with a coal-rice straw blend, in case of low natural gas supply. The model is further employed to assess different revamping scenarios and alternatives within the natural gas power plant. For a dry blend of (90 % Egyptian coal and 10 % rice straw), the cold gas efficiency is estimated as 85.7 %, while for dry Egyptian it is calculated as 79.61 %. The revamped Egyptian natural gas power plant decreases the total annualized cost (TAC) by 52.7 % with respect to a new constructed integrated gasification combined cycle (IGCC) plant. Besides, the payback period decreases to 1.24 y rather than 12 y in case of the construction of a new IGCC power plant.
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| 5. |
- Alhajri, Ibrahim H., et al.
(författare)
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Retrofit of heat exchanger networks by graphical Pinch Analysis - A case study of a crude oil refinery in Kuwait
- 2021
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Ingår i: Case Studies in Thermal Engineering. - : Elsevier BV. - 2214-157X. ; 26
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Tidskriftsartikel (refereegranskat)abstract
- Energy integration of the existing chemical and petrochemical facilities is regarded as a keystone for sustainable energy systems. It is widely known that a considerable number of the petrochemical industries are not applying efficient heat exchanger network (HEN) systems to minimise the use of external utilities. In the present study, a Pinch Analysis-based graphical approach is used to retrofit an existing HEN for optimising a crude oil distillation operation. The existing HEN is represented using Thot-Tcold diagram, where the cold stream temperatures are plotted on the x-axis and the hot stream temperatures are plotted on the y-axis, for each exchanger unit. The graphical approach is applied to a real case study of a petroleum refinery plant located in Kuwait with the objective of performing energy analysis and retrofitting the existing HEN. Retrofit modifications are extracted from the graphical representation to enable scenarios for energy and emission reduction. The application of the proposed approach resulted in substantial energy savings of about 10.4 MW compared to the current operation, leading to annual operating cost savings of about MM$2 and less than one-year payback time. Overall, this study provides tools to address the energy traits in crude preheat trains of industrial feature, which can improve the overall economic-environmental sustainability of existing refineries.
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| 6. |
- Bayomie, Omar S., et al.
(författare)
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Exceeding Pinch limits by process configuration of an existing modern crude oil distillation unit – A case study from refining industry
- 2019
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Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526. ; 231, s. 1050-1058
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Tidskriftsartikel (refereegranskat)abstract
- Crude Distillation Unit (CDU) represents significant challenge for retrofitting and energy optimisation as the most energy intensive consumer in a conventional crude oil refinery. Pinch Technology and its based-methodologies are found primary keys for decades to energy savings in refining industries for a range of common economic-based and environmental objectives or applications. Typical benefits in energy savings are reported within 20–40% of original designs. However, such savings are limited and questioned when modern refiners are dealt with. The current paper addresses the revamping of a modern refinery exhibiting an existing high energy efficiency (≈93%). This implies the maximum potential energy savings would only be 7% at current process conditions. The present research proposes an algorithm that tackles energy recovery of modern refiners, enabling additional savings beyond the energy targets set by the existing process. The algorithm starts by process simulation and validation against real plant data, followed by a network optimisation, e.g. stream splitting, to reach the energy targets set by Pinch Analysis. The energy targets are then moved to another lower level by performing potential process modifications to reduce the energy consumption further. Results showed that the current modern refinery unit could reach its energy targets by stream splitting modifications with hot energy savings of 2.69 MW. Process modifications resulted in additional energy savings of 31.3% beyond the current level of the existing plant alongside less than a year of payback period for estimated capital investment. An environmental assessment is performed, and comparable reductions were obtained with respect to greenhouse gas, with reduction in CO2 emissions by 45.1%. The proposed retrofit methodology is applicable to minimising energy consumptions of refiners including modern units to achieve energy levels beyond energy targets by new process modifications.
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| 7. |
- Gadalla, Mamdouh A., et al.
(författare)
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Conceptual insights to debottleneck the Network Pinch in heat-integrated crude oil distillation systems without topology modifications
- 2016
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904. ; 126, s. 329-341
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Tidskriftsartikel (refereegranskat)abstract
- Heat exchanger network pinch sets the limitations of heat recovery for existing network topologies. Improving the heat recovery within a pinched-network is independent of the areas of individual exchangers present in the network, rather the topology of the network must be altered. Such a change in the topology can be very capital intensive and in many cases seems not easy to implement. This research aims to overcome the Network Pinch through proposing process operation changes, avoiding network topology alterations; hence, debottlenecks the heat-integrated systems towards further energy savings beyond the maximum heat recovery limitations. A new graphical representation is recently proposed to simulate existing preheat trains/networks with all energy equipment. The recent graphical representation is employed in this work to identify the pinching matches that limit heat recovery. Therefore, such graphs are key tools to identify potential process changes by which the Network Pinch is overcome. New graphs are constructed involving hot stream temperatures against cold stream temperatures. Existing exchangers are described by straight lines, with slopes related to flows of process streams and heat capacities. Exchanger matches touching the line where hot outlet stream temperature equals cold inlet stream temperature are pinching matches; this condition corresponds to absolute maximum heat recovery (ΔT = 0). Potential process changes within a distillation unit are identified to relax the Network Pinch and further heat recovery is maximised. The slope of such an exchanger match is decreased or the location of the pinching match is altered keeping the same slope. These changes are translated into process changes within the crude oil distillation unit. Accordingly, the process changes are determined based on which match is pinched besides its location within the network. An illustrative example shows that process changes overcome the Network Pinch and energy recovery is increased by 14% beyond the maximum level achieved for the existing process conditions. Capital investments imposed are minor compared with substantial energy cost savings.
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| 8. |
- Umar, Yusuf, et al.
(författare)
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A renewable lignin-derived bio-oil for boosting the oxidation stability of biodiesel
- 2022
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Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481. ; 182, s. 867-878
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Tidskriftsartikel (refereegranskat)abstract
- The valorisation of lignin is being increasingly recognised to improve the economics of pulp and paper making mills. In the present study, an integrated lignin–glycerol valorisation strategy is introduced with an overarching aim for enhancing the process value chains. LignoBoost kraft lignin was subjected to base-catalysed depolymerisation using glycerol as a co-solvent. The generated bio-oil was used as a renewable additive to biodiesel for enhancing its oxygen stability. The influence of three independent parameters including temperature, time and glycerol amount on lignin depolymerisation was investigated. Response surface methodology was applied to design the experiments and to optimise the process for maximising the yield and antioxidant impact of bio-oil. The results showed that glycerol has a positive qualitative and quantitative impact on the produced bio-oil, where an enhancement in the yield (up to 23.8%) and antioxidant activity (up to 99 min induction period) were achieved using the PetroOxy method (EN16091). The addition of 1 wt% bio-oil to biodiesel has led to an improvement in the oxidation stability over a neat sample of up to ∼340%, making it compliant with European standard (EN14214). The proposed process presents a biorefinery paradigm for the integrated utilisation of waste cooking oil, lignin and glycerol.
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