241 research outputs found
Integration of LNG Regasification and Air Separation Units
No full textThrough the various LNG cold recovery applications, cryogenic air separation is the only one recovering the coldest range of exergy, which is also the most valuable. Several designs of integrated ASU and LNG regasification have been proposed but there is still a lack of fair comparison between the existing options. In this study, promizing configurations have been selected and classified according to the number of columns in the ASU block and the use of LNG cold exergy either for feed air cooling or in the nitrogen liquefaction loop. Each case has been modelized in the commercialized software Aspen HYSYS and evaluated thanks to a range of performance indicators: LNG cold exergy use, work requirement per amont of liquid nitrogen produced, Exergy Transfer Effectiveness and the decomposition of material stream exergy variations both at stream level and at component level. The two first indicators where insufficient to compair fairly the cases and required to scale the designs to a common set of constraints. ETE provided a tool to fairly compare the designs, with regards to all the ASU products, without re-scaling the original models. Yet, the high energy requirements for ASU processes overweighted material stream exergy variations in ETE results, making it close to a ratio of expansion to compression work. Further decomposition of material exergy variations confirmed that exergy analysis at component level was more consistant than stream level calculation for processes with a chemical change. Single column designs were more efficient than two-column ASU configurations, the best performing cases among integrated designs being the recuperative vapor recompression ASU using heat pump effect proposed by Fu and Gundersen (2013) followed by the integration of column draws coupled to compression-expansion described by Mehrpooya et al (2015)
Integration of LNG Regasification and Air Separation Units
No full textThrough the various LNG cold recovery applications, cryogenic air separation is the only one recovering the coldest range of exergy, which is also the most valuable. Several designs of integrated ASU and LNG regasification have been proposed but there is still a lack of fair comparison between the existing options. In this study, promizing configurations have been selected and classified according to the number of columns in the ASU block and the use of LNG cold exergy either for feed air cooling or in the nitrogen liquefaction loop. Each case has been modelized in the commercialized software Aspen HYSYS and evaluated thanks to a range of performance indicators: LNG cold exergy use, work requirement per amont of liquid nitrogen produced, Exergy Transfer Effectiveness and the decomposition of material stream exergy variations both at stream level and at component level. The two first indicators where insufficient to compair fairly the cases and required to scale the designs to a common set of constraints. ETE provided a tool to fairly compare the designs, with regards to all the ASU products, without re-scaling the original models. Yet, the high energy requirements for ASU processes overweighted material stream exergy variations in ETE results, making it close to a ratio of expansion to compression work. Further decomposition of material exergy variations confirmed that exergy analysis at component level was more consistant than stream level calculation for processes with a chemical change. Single column designs were more efficient than two-column ASU configurations, the best performing cases among integrated designs being the recuperative vapor recompression ASU using heat pump effect proposed by Fu and Gundersen (2013) followed by the integration of column draws coupled to compression-expansion described by Mehrpooya et al (2015)
Optimal diluent allocation in production systems with diluent-ESP-lifted wells
No full textIn this research, the author presents the development of a numerical model for production systems (wells and surface flowlines) to determine optimal diluent allocation. The model includes the main inflow performance equations to represent reservoir deliverability, pressure and temperature drop calculations in tubing, electric submersible pump (ESP) modeling including viscosity and frequency correction equations, and oil blending models for the injection module. For the injection module, both ASTM D7152-11 standard and Cragoe (1933) methods are available. For the production fluid modeling, the author considered the black oil model to calculate thermodynamic properties and an emulsion model to calculate fluid viscosity depending on its water cut. The gas phase was neglected. The model was developed by using object-oriented programming (OOP) in a commercial software
Optimal design of heat exchanger networks with pressure changes.
No full textDue to climate change is it desirable to improve the energy efficiency of production systems. The environmental impact will decrease with increasing energy efficiency and it will even reduce the operational cost. Heat integration is a much used method for improving the energy efficiency and the annualized cost. The usual heat exchanger network synthesis problem is to design a heat exchanger network that minimizes the annualized cost. A set of hot streams which needs to be cooled and a set of cold streams which need to be heated is given. When the possibility of expanding or compressing some of the streams is added, the problem gets more complex. Without pressure manipulation the streams are continuously heated/cooled from the supply temperature to the target temperature. Pressure manipulation changes the temperature of the fluid going through the turbine/compressor, so the stream is split into two parts. This can cause the streams to change identity and makes the modeling and optimization more difficult. The objective is to minimize the hot and cold utilities, minimize compression work and maximize the work produced by turbines. Because of the difference in energy quality is exergy going to be used instead of energy. Fu and Gundersen (2015b) have made some insights and a graphical procedure that finds a good solution to the problem. The procedure and theorems have not been received as well as the authors hoped, so an optimization model not based on their insights was of interest. A MINLP model, which did not utilize the insights from Fu and Gundersen (2015b), was developed in the project thesis. The model handled expansion of hot and cold streams above ambient. In this master thesis have the model been extended to also include compression and below ambient temperatures. The MINLP model did not always find the optimal solution, so a new model with the use of insights was developed. The model became a much simpler LP model and have for all test cases found an equally good or better solution than the first model and the graphical procedure. Both models have been implemented in GAMS and have been tested on several test cases. The concept of simultaneous work and heat integration is quite novel and the models developed in this thesis is just a step in the right direction. The end will probably be an optimization model which designs the work and heat exchange network with respect to the annualized costs
Optimal design of heat exchanger networks with pressure changes.
No full textDue to climate change is it desirable to improve the energy efficiency of production systems. The environmental impact will decrease with increasing energy efficiency and it will even reduce the operational cost. Heat integration is a much used method for improving the energy efficiency and the annualized cost. The usual heat exchanger network synthesis problem is to design a heat exchanger network that minimizes the annualized cost. A set of hot streams which needs to be cooled and a set of cold streams which need to be heated is given. When the possibility of expanding or compressing some of the streams is added, the problem gets more complex. Without pressure manipulation the streams are continuously heated/cooled from the supply temperature to the target temperature. Pressure manipulation changes the temperature of the fluid going through the turbine/compressor, so the stream is split into two parts. This can cause the streams to change identity and makes the modeling and optimization more difficult. The objective is to minimize the hot and cold utilities, minimize compression work and maximize the work produced by turbines. Because of the difference in energy quality is exergy going to be used instead of energy. Fu and Gundersen (2015b) have made some insights and a graphical procedure that finds a good solution to the problem. The procedure and theorems have not been received as well as the authors hoped, so an optimization model not based on their insights was of interest. A MINLP model, which did not utilize the insights from Fu and Gundersen (2015b), was developed in the project thesis. The model handled expansion of hot and cold streams above ambient. In this master thesis have the model been extended to also include compression and below ambient temperatures. The MINLP model did not always find the optimal solution, so a new model with the use of insights was developed. The model became a much simpler LP model and have for all test cases found an equally good or better solution than the first model and the graphical procedure. Both models have been implemented in GAMS and have been tested on several test cases. The concept of simultaneous work and heat integration is quite novel and the models developed in this thesis is just a step in the right direction. The end will probably be an optimization model which designs the work and heat exchange network with respect to the annualized costs
Optimal diluent allocation in production systems with diluent-ESP-lifted wells
No full textIn this research, the author presents the development of a numerical model for production systems (wells and surface flowlines) to determine optimal diluent allocation. The model includes the main inflow performance equations to represent reservoir deliverability, pressure and temperature drop calculations in tubing, electric submersible pump (ESP) modeling including viscosity and frequency correction equations, and oil blending models for the injection module. For the injection module, both ASTM D7152-11 standard and Cragoe (1933) methods are available. For the production fluid modeling, the author considered the black oil model to calculate thermodynamic properties and an emulsion model to calculate fluid viscosity depending on its water cut. The gas phase was neglected. The model was developed by using object-oriented programming (OOP) in a commercial software
A systematic Design Methodology for Multicomponent Membrane Systems
No full textAbstract
Fossil fuel predominantly dominates the world energy supply. With energy demand set to increase, especially for developing countries, CO2 emissions tax and the environmental impact of high CO2 concentration in the atmosphere emphasises the need for a cost effective solution to CO2 emissions capture. Existing CO2 capture technologies are expensive, giving an opportunity for a new technology. Membrane technology is emerging has the alternative solution in the CO2 capture market.
Finding the right design and configuration for a membrane system is difficult and time consuming. A simple way has been developed which makes use of a graphical representation of stages of membrane system with cost curve for optimization. This method for systematic membrane design has been tested and seen to be a useful tool in the early design phase of a membrane system. This report develops this methodology in two main areas. First, it extends the graphical methodology from a binary feed to a ternary feed by the development of new design concepts. Secondly, it expands the application of the methodology to more industries other than CO2 post combustion capture by incorporating different process scenarios into the methodology
A systematic Design Methodology for Multicomponent Membrane Systems
No full textAbstract
Fossil fuel predominantly dominates the world energy supply. With energy demand set to increase, especially for developing countries, CO2 emissions tax and the environmental impact of high CO2 concentration in the atmosphere emphasises the need for a cost effective solution to CO2 emissions capture. Existing CO2 capture technologies are expensive, giving an opportunity for a new technology. Membrane technology is emerging has the alternative solution in the CO2 capture market.
Finding the right design and configuration for a membrane system is difficult and time consuming. A simple way has been developed which makes use of a graphical representation of stages of membrane system with cost curve for optimization. This method for systematic membrane design has been tested and seen to be a useful tool in the early design phase of a membrane system. This report develops this methodology in two main areas. First, it extends the graphical methodology from a binary feed to a ternary feed by the development of new design concepts. Secondly, it expands the application of the methodology to more industries other than CO2 post combustion capture by incorporating different process scenarios into the methodology
Optimization of Heat Exchanger Network using SeqHENS
No full textHvordan varmeveksler nettverk kan settes opp har vært forsket på siden 1970 tallet. Hovedmålet har da alltid vært å finne en mest mulig effektiv konfigurasjon for å overføre varme mellom masses- trømmer. Det begynte på 1970 tallet med pinch analyse og i dag finnes det flere programmer som kan analysere slike problemer. Dette prosjektet skal har som hovedfokus å teste et av disse pro- grammene SeqHENS.
Gjennom rapporten blir SeqHENS tested ved å redusere antallet temperatur intervaller. Ved å gjøre dette skal oppgaven se om det er mulig å redusere regnetiden til SeqHENS. Den andre delen av oppgaven vil være å utforme en "Difficulty Indicator" for SeqHENS. Den skal ha som mål å gi en indikasjon på hvor vanskelig det er å løse et "HENS»-problem. Resultatene fra denne studien diskuterer ut fra tre faktorer, kostnaden relaterte til resultatene, regne tiden når antallet temper- atur intervaller blir redusert og eventuelle feil som oppstår i resultatene når antallet temperatur intervaller blir redusert.
Under denne studien vil fire forskjellige "Difficulty Indicator" bli testet på de forskjellige casene i studien og sammenlignet etter hvor god indikasjon de gir for regne tiden til SeqHENS.
Resultatene fra case studiet viser at antallet mulige matcher gir en god indikasjon på hvor lang regne tiden til SeqHENS vil være. Resultatene viser også at ved å redusere antallet temperatur in- tervaller vil dette redusere kvaliteten på resultantene, og faktisk øke regne tiden under de fleste omstendigheter.How heat exchanger networks can be set up has been researched since the 1970s. The main goal then has always been to find the most efficient configuration for transferring heat between mass streams. It began in the 1970s with pinch analysis and today there are several programs that can analyze such problems. The main focus of this project is to test one of these programs SeqHENS.
Throughout the report, SeqHENS is tested by reducing the number of temperature intervals. By doing this, the task will be to see if it is possible to reduce the calculation time for SeqHENS. The second part of the task will be to design a "Difficulty Indicator" for SeqHENS. It aims to give an indication of how difficult it is to solve a HENS problem. The results of this study discuss based on three factors, the cost related to the results, calculate the time when the number of temperature intervals is reduced, and any errors that occurs in the results when the number of temperature intervals is reduced.
During this study, four different "Difficulty Indicator" will be tested on the different cases in the study and compared to how good the indication they give for calculation time in SeqHENS.
The results from the case study show that the number of possible matches gives a good indica- tion of how long the time of SeqHENS will be, and the results also show that by reducing the number of temperature intervals this will reduce the quality of the results and in fact increase the time in most circumstances
Optimalisering av DMR prosesser for flytendegjøring av naturgass
No full textFour DMR processes alternatives were modeled and optimized in Aspen HYSYS in order to evaluate their efficiency. The alternatives studied are processes developed by Shell, Air Products and Chemicals, Inc (APCI), Axens-IFP and Tealarc. The objective of the project was to test the Hyprotech SQP optimizer in Aspen HYSYS and report on the its performance, while comparing the energy requirements and the configuration complexity for the proposed processes. The mixed refrigerants composition, as well as their inlet pressures were the main variables in the optimization problem formulation. The degree of meeting the constraints of the process paid a crucial role when analyzing the performance of the optimizer. Exergy analysis was conducted in order to find the exergy loss and the exergy efficiency of the proposed solutions. The optimization results showed that the Shell alternative had the lowest specific power consumption of 214.8 kWh⁄ton , while the Tealarc alternative had the highest exergy efficiency of 56.8%. However, from the complexity point of view, Shell alternative was a better solution for the offshore floating vessels due to its lower equipment size. Further work should be conducted to improve the optimizer performance, by developing a new nonlinear programming method that would solve the optimization problem
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