Transiente motstrøms tyngdekrafts-drevne olje-vann strømningsforsøk ble gjort i en to meter lang lukket plexiglass sylinder. Et enkelt eksperimentelt oppsett baser på visuelle observasjoner ble laget med formål for disse forsøkene. Eksperimenter ble gjort for et stort utvalg av inklinasjoner mellom 0 og 90 grader fra horisontalen. Effektene av ulike eksperimentelle parametere ble undersøkt ved å bruke to typer olje, Exxsol D80 og Marcol 52, to sylindere med ulik indre diameter, 50mm og 90mm, i tillegg til tre ulike vannkutt; 0,25, 0,5 og 0,75. For å simulere et bredt utvalg av strømnings situasjoner ble det brukt tre ulike start kondisjoner med varierende grad av miksing av innholdet. Totalt ble det gjort 755 eksperimenter i løpet av denne oppgaven. Resultatene fra observasjonene har blitt brukt til å danne slip relasjoner som skal bli implementert i en slug-tracking simulator som blir utviklet ved NTNU. Fire ulike strømningsmønster har blitt identifisert for denne type strømning. Kun små forskjeller i strømningsmønster ble observert for ulike olje faser og sylinder diametere. Helninger mellom 15 og 30 grader ble funnet til å gi høyest slip hastighet mellom olje og vann fasene.

This dissertation consists of three chapters; each models competition in natural gas markets. These models provide insight into interactions between changes in market conditions/policies and market players’ strategic behavior. In all three chapters, we apply our models to a natural gas trade network formed by using BP’s Statistical Review of World Energy 2010 major trade flows. In the first chapter, we develop a model for the world natural gas market where buyers and sellers are connected by a trading network. Each natural gas producer is a Cournot player with a fixed supply capacity. Each of them is also connected to a unique set of importing markets. We show that this constrained noncooperative Cournot game is a potential game and its potential function has a unique maximizer. In the scenario analysis, we find that any exogenous change affecting Europe also has an effect in the Asia Pacific. The reason is that two big producers, Russia and the Middle East, are connected to both markets. We also find that a collusive agreement between Russia and the Middle East leads them to specialize in supply to markets based on their marginal costs of exporting natural gas. The second chapter is devoted to analyzing the impacts of North American shale gas on the world natural gas market. To better represent the North American natural gas market, this chapter also allows for perfect competition in that market. We find that North America exports natural gas when its supply curve is highly elastic and hence the domestic price impact of its exports is very small. Even so, the price impacts on the importing markets are substantial. We also find that shale gas development in North America decreases dominant producers’ market power elsewhere in the world and hence decreases the incentive of any parties to form a natural gas cartel. In the third chapter, we relax the assumption of fixed supply capacities and allow for natural gas producers to invest in their supply capacities. We assume a two period model with no uncertainty and show that there is a unique Cournot-Nash equilibrium and the open-loop Cournot-Nash equilibrium and closed-loop Cournot-Nash equilibrium investments coincide.

Most of nowadays base load LNG plants are localized in the area around equator, with stable warm air and cooling water temperature. For new LNG developments in arctic areas there are several features that differ them from plants operating further south. In this work a ConocoPhillips Optimized Cascade LNG process model has been established in HYSYS® and evaluated. The evaluation focus on the driver configuration and cooling method used in order to optimize process efficiency and capacity of the plant for operation in cold climate. Simulations with air cooling and water cooling have been done. Each cooling method has been evaluated for an aero derivative gas turbine compressor driver, an industrial heavy duty gas turbine compressor driver, and an electric compressor driver configuration. Yearly temperature statistics from Kola has been used. The air cooled simulations have a design temperature of 20°C and the water cooled simulations have a design temperature of 4°C seawater temperature and an air temperature of 5°C. The air cooled cases are not close to design operation the entire year. The aero derivative driver configuration will have problems operating at high air temperatures and a higher design temperature is needed. The heavy duty gas turbine driver configurations have limitation in speed variation and this leads to low process efficiency at low temperatures. The electrical driver configuration will not have problems operating. The results show that air cooling is not the desired cooling method because of lower production variation and lower process efficiency. The water cooled cases are close to design conditions the entire year; hence it has the highest flexibility when it comes to production variation and highest process efficiency. The aero derivative driver configuration varies most throughout the year with lowest production in the summer. The heavy duty gas turbine driver configuration has a lower variation in production. The power delivered to the electrical motors will not be affected by air temperature which lead to high process efficiency and stable production plateau throughout the year.

As the main goal achieved with this master thesis, a plant design was constructed for an acid gas removal process with methanol operating at low temperatures. First, a bibliographical research was made in terms of sour gas treatment; with special focus of physical absorption processes involving methanol as the solvent to achieve separation; such as Rectisol and Ifpexsol. The literature research was extended to thermodynamic data; compiling equilibrium values for binary systems between methanol and carbon dioxide (CO2), hydrogen sulphide (H2¬S) and methane (CH4); respectively. The simulator Pro II with Provision was selected as the computational tool to achieve thermodynamic calculations for the gas stream to be treated. The thermodynamic Equation of State (EOS) utilized to model the properties of the system was a simulator built in modified version of the Soave-Redlich-Kwong-Panagiotopuolos-Reid EOS. Comparisons between the researched equilibrium values and the simulated data were done; corroborating that the model was strong enough to perform calculations for components related with acid gas removal. A natural gas stream rich in Carbon Dioxide (CO2), Nitrogen (N2) and heavy-hydrocarbons was selected from Statoil’s Snøhvit gas treatment processing in order to be subject of acid gas removal. The plant design for the sour gas treatment was developed in three individual stages that were later integrated: heavy-hydrocarbons removal, absorption with methanol and solvent regeneration. The design proposed was effective into removing the CO2 present in the natural gas stream down to a value of 40 ppmv.Finally, a brief pinch analysis was sketched; thus identifying the actual possibility of heat integrating the system with an LNG processing unit. In conclusion, simple simulation and thermodynamic tools can conduct to efficient designs for integral acid gas removal plants.

Severe slugging is an undesirable unsteady multiphase flow phenomenon which occurs in riser-pipeline systems. During the course of this masters thesis work, a dynamic coupling has been shown to exist between this flow phenomenon and the flexible riser in which it occurs. To analyse the influence of this coupling, the cyclic displacement of the riser and the loads exerted by this cyclic displacement on the risers attachment point to a topside vessel have been evaluated.A small scale experiment has been set up of a flexible riser (L and S configurations) undergoing the severe slugging cycle. The flexible risers were produced from a flexible transparent hose of internal diameter 0.016 metres and a load cell was used to measure the loads on the riser attachment point to a topside vessel. Three accelerometers were attached along the riser to measure the acceleration of the riser at defined points. The experiment was video recorded and from this, video analysis was used to calculate the displacement of the flexible riser during the severe slugging cycle. Data from the experiments was logged by Catman analysis tool and was compared with numerical simulations from OLGA.Substantial displacement of the flexible riser has been recorded on both configurations of the flexible riser. Displacements in the order of approximately 1 metre have been recorded on some riser points on both riser configurations. When this occurs, there is a cyclic loading on the attachment point of the flexible riser to the topside vessel and this loading in the long term could lead to fatigue of the riser and probable failure. This loading has been illustrated, and maximum and minimum values for both riser configurations have been recorded.For the constructed L-riser, the displacement of the riser at the top, middle and bottom sections were found to be 0.8588, 0.9760 and 0.5856 metres respectively. The maximum and minimum loads on the attachment points of the L-riser to the topside vessel during the severe slugging cycle have been found to be 0.1 and 6.4 Newtons respectively.For the constructed S-riser, the displacement of the riser at the top, middle and bottom section were found to be 0.112, 0.7760 and 0.957 metres respectively. The maximum and minimum loads on the attachment point of the S-riser to the topside vessel during the severe slugging cycle have been found to be 8.0 and 13.6 Newton respectively.

The main goal of this thesis is to find out if a liquefied natural gas multistream heat exchanger numerical model is achievable. This should include several features usually neglected in nowadays available heat exchanger models, such as flow maldistribution, changes in fluid properties and heat exchanger dynamic behaviour. In order to accomplish that objective a simpler case is modelled. Efforts are put in achieving numerical stability.A counter flow natural gas and mixed refrigerant heat exchanger is modelled. Some important characteristics of the obtained model are: (1) it allows a dynamic study of the heat exchanger, (2) mass flow rate is a consequence of inlet and outlet pressure difference, (3) fluid properties change is taken into account, (4) it presents a time step control function and (5) fluid movement is not neglected. Some interesting numerical behaviours included in heat exchangers models design that have been observed during the course of this thesis are discussed. For instance, the comparison of the effects of choosing one heat transfers correlation or another.Dynamic response of the modelled heat exchanger during start up and during an abrupt change in mixed refrigerant inlet temperature are shown and discussed.

The pinch analysis method has been applied to different processes successfully for heat integration. Since it does not include pressure as a factor in low temperature processes and it has important role in those processes, Extended Pinch Analysis and Design (ExPAnD) method has recently developed for heat integration in low temperature processes.The main motivation for this Master thesis is to further develop the ExPAnD methodology by considering cyclic processes and utilities, where the quality of the design is measured by the Exergy Transfer Effectiveness (ETE). In this project, the exergy concept is studied. A review among literatures has been done and different definitions for exergy efficiency are identified. The pinch analysis method and ExPAnD method are also reviewed briefly. Exergy analysis based on Exergy Transfer Effectiveness (ETE) has been applied to operation units which are used in LNG production processes. Moreover, dual independent expander refrigeration cycles process for LNG production has been analyzed from the exergy point of view. The related heuristic rules of ExPAnD method are studied. This method has been applied to the process of dual independent expander refrigeration cycles successfully. Finally, a new approach is proposed which improves the exergy efficiency of the cyclic low temperature processes.

Flow instabilities in long wells and risers under certain flow conditions, is well known. Expansion driven flow instability (EDI) which is relatively little known, refers to occurrence of flow instabilities in long wells and risers as a result of entrapment of gas upstream of the well or riser base. EDI can also occur in gas-lift systems at low pressure and low gas injection rate.This work was initiated to tackle flow instability problem related to deep water production operations where long wells and risers are extensively in use. The aim of this thesis is to investigate a type of flow instability known as “Expansion Driven Flow Instability (EDI) in Long Wells and Risers”. This involves experimental investigation as well numerical modelling of expansion driven flow instability in long wells and risers. Finally results of the experimental investigations are compared with numerical model data.An experimental flow loop was setup to verify EDI at varying pipe geometry, inlet flow pressure and gas flow rate to examine the effect of EDI in long wells and risers. The laboratory experiment was conducted using air and water at atmospheric conditions, in a flowline-riser system consisting of a 32mm diameter and 9.12m long riser. The expansion driven flow cycle was captured in video recording.Variation of inlet flow pressures was achieved by varying the height of the overflow tank. Three cases were considered, each at a different inlet pressure. Each inlet pressure of the fluid was examined against varying inclination angles of the horizontal pipe to the riser inlet. Different gas flow rates were tested at different inclination angles. It was observed that inclination angle has the greatest impact on EDI.Experimental result of one of the cases was modelled using OLGA and the results of the experimental compared against simulation results output. Discrepancies in the two sets of results were observed in some cases. These may be attributed to simplifications and assumptions made during the simulation model build.Both results of the experimental investigation and numerical simulation demonstrated that expansion driven flow instability can occur in laboratory setup and can probably occur in deep water natural-lift wells and risers as well as gas-lifted wells and risers under certain flow conditions and pipe inclinations. 

Chemical Looping Combustion is one of the most promising way to limit the CO2 release to the atmosphere among the other technologies for Carbon Capture and Storage (CCS). It constitutes an indirect fuel combustion strategy, in which metal oxide is used as oxygen carrier, to transfer oxygen from the combustion air to the fuel, avoiding direct contact between air and fuel. It is basically an unmixed combustion process (fuel and air are never mixed) whose flue gases are mainly CO2 and steam. Thus, after condensation, the carbon dioxide can be easily separated from the exhaust.SINTEF Energy Research and the Norwegian University of Science and Technology (NTNU) have designed a 150kWth second generation chemical looping combustion reactor system. It consists of a double loop circulating fluidized bed (DLCFB) reactor system where both the air reactor and the fuel reactor are Circulating Fluidized Beds (CFB) meant to work in the fast fluidization regime and interconnected by divided loop-seals and a bottom extraction to achieve high solids circulation and be flexible in operation. The main purpose of this project is to be strongly industrial oriented in order to make the step from lab-scale to industrial application easier. A Cold Flow Model (CFM) has been built to verify the design of the CLC reactor system.CFM consists of two reactors, the fuel and the air reactor, with different diameters, each one having a loop seal . No chemical reaction happens inside the CFM, because its main goal is to have the understanding of the hydrodynamics of the system.An experimental campaign was performed in order to find the best conditions for the solid flux, reaching stability, and the proper flow regimes for the coupled reactors in the CFM. An investigation and mapping of the operating area of the coupled reactors was the target of the experiments.As the first step and for further research, the best set of operating conditions is selected by considering the stability and solid flux in order to meet the design targets. This experiment is used as the reference case and later all other operational modes in the cold flow model which resembles CLC are evaluated against the base data obtained.Different operational modes of Chemical Looping Combustion were designed by means of the CFM to validate the CLC reactor system design. A significant effort was done to reach part-load , maximum power , maximum fuel reactor concentration and reforming to define the best operational window. In each of the mentioned experiments pressure profiles and concentration of the solids are compared to the reference case of the CFM.As long as the loop seal plays a key role in the operation of the CFB, for assuring the solids movement in an endless loop, series of experiments were performed in the CFM in order to map the operational window of the loop seal. The sensitivity of the loop seal is evaluated by pressure difference in the bottom of the fuel reactor and air reactor during the operation of the CFM to obtain an operational window for the loop seal. For the last step, the effects of the total mass inventory circulating in the system for five different operational modes were investigated by increasing and decreasing the inventory. For each case the pressure profiles and concentration of the solids is compared with the reference case and the results are shown in this thesis work.

The four liquefaction processes proposed as a good candidate for LNG FPSO are simulated and evaluated. These processes include a single mixed refrigerant (SMR), dual mixed refrigerant (DMR), Niche LNG ( CH4 and N2 process) and dual nitrogen expander. The steady state hysys simulation of the processes were undertaken to ensure that each simulated liquefaction process was compared on the identical parameters. An in-depth optimization has not been conducted but the simulation was aimed at obtaining an optimal efficient processes based on the simulated constraints.This thesis presents the analysis of the effects of natural gas pressure, temperature and composition on the proposed liquefaction processes for LNG FPSO. During the simulations the effects were analyzed by examining specific power, power consumption and refrigerant flow rate of the proposed processes. To meet the demand of greater efficiency and large capacity for liquefaction processes, thermodynamic analysis on the liquefaction processes for LNG FPSO also has been evaluated. The analysis of specific powers, power consumptions and refrigerant flow rates on the proposed processes shows that DMR specific power is lower than that of dual nitrogen expander by 50%, Niche LNG by 41.6% and SMR by 9.6%. The power consumption of DMR is lower that of dual nitrogen expander by 54%, Niche LNG by 47.8% and SMR by 9.6%. Also DMR has lowest refrigerant flow rate than that of dual nitrogen expander by 157.6%, Niche LNG DMR by 96.4% and SMR by 30.9%The production capacity of simulated processes shows that DMR has higher production capacity per train of (0.91MTPA/Train) and dual nitrogen expander has the lowest which is (0.61MTPA/Train) based on maximum duty of one LM6000 gas turbine. DMR production capacity exceeded that of dual nitrogen expander by 33%, Niche LNG by 29.7% and SMR by 8.8%.The analysis of effect of natural gas supply temperature on the proposed processes shows that the change of natural gas supply temperature has major effect of SMR process compared to other process. The analysis shows that when natural gas supply temperature decreases from 15 to 50C SMR specific power and power consumption decrease by 14.99% and 15.10% respectively and when it is increases from 15 to 250C its specific power and power consumption increases by 39.27% and 39.19 respectively.The analysis of the effect of natural gas supply pressure on the proposed processes shows that when natural gas supply pressure decrease dual nitrogen expander has the highest effect with specific power and power consumption increases by 22.41% and 23.25% respectively and when natural gas supply pressure increases DMR has highest effect on specific power and power consumption which are 13.06% and 13.67% respectively.The effect of natural gas composition on the proposed natural gas liquefaction processes for LNG FPSO shows that for all proposed processes the change in natural gas composition may lead to increase or decrease of processes specific power, power consumptions or refrigerant flow rates. Energy efficiency is important to LNG production as feed gas is consumed in order to carry out the liquefaction process .The exergy analysis of the proposed process shows that shows that DMR process has highest useful exergy about 31% compared to the other processes. Niche LNG and dual nitrogen expander has almost same useful exergy.