Research Abstracts

Abedinzadegan Abdi M., Hussain A., Hawboldt K., and Beronich E. 'Experimental Study of Solubility of Natural Gas Components in Aqueous Solutions of Ethylene Glycol at Low Temperature and High Pressure Conditions', under review, Journal of Chemical and Engineering Data, 2007.

Abstract: A new experimental setup has been validated to measure gas solubility at low-temperature and high-pressure conditions. Solubility of natural gas components, for example, methane, nitrogen, and carbon dioxide, was measured in aqueous solutions of 40 and 60 mass % of ethylene glycol at 15.00 and 20.00 MPa and at temperatures of -10.0, 0.0, and 10.0 ^oC.
Jassim E., Abedinzadegan Abdi M., and Muzychka Y. 'Computational Fluid Dynamics Study for Flow of Natural Gas through High Pressure Supersonic Nozzles: Part 1 - Real Gas Effects and Shockwave', in press, Journal of Petroleum Science and Technology, PET/06/097, 2006.

Abstract: The computational fluid dynamics technique was used to study the behaviour of high pressure natural gas in supersonic nozzles. Although many applications of gas flow produce insignificant errors when the gas is assumed ideal, our results indicate significant variation of gas properties. This paper illustrates natural gas behaviour when it is considered to be real and how erroneous the properties may become when the gas is assumed to be ideal. The paper also presents the influences of properties related to the flow of natural gas through supersonic nozzles. Using a quite accurate equation of state model, real gas effects are studied and compared with the perfect gas case. The results show a significant variation in gas properties estimation. Location of shockwave is also analyzed. The comparison of results for two gases (methane and nitrogen) indicated that shockwave position can significantly change when the gases considered as real rather than perfect.
Jassim E., Abedinzadegan Abdi M., and Muzychka Y. 'Computational Fluid Dynamics Study for Flow of Natural Gas through High Pressure Supersonic Nozzles: Part 2 - Nozzle Geometry and Vorticity', in press, Journal of Petroleum Science and Technology, PET/06/098, 2006.

Abstract: The computational fluid dynamics technique is used to study the behaviour of high pressure natural gas when it flows through nozzles with supersonic velocities. Effect of nozzle geometry is discussed by inserting a constant area channel between the convergent and divergent parts of the system. Various conduit lengths are analyzed to show how the minimum temperature could be influenced by the geometry of the nozzle. The results also show that changing channel length can affect the position of shockwave. The results for the effect of vorticity on the performance of the nozzles show that although losses in pressure increase due to inlet swirl flow, vorticity increases very sharply in the vicinity of the shock. It could be concluded that the region just before the shock spot is the main region where fine particles can be separated because of the large vorticity strength. Shock with reasonable strength may be favoured in practical applications where fine particles separation is desired.
Jassim, E., A. Abdi M., and Muzychka Y. 'Thermal Effects of Cold Jet on Pressure Vessels and Surrounding Equipment', proceedings of the 2006 International Marine CNG Standard Forum, St. John's, NL, Canada, November 7-9, 2006.

Abstract: Cold jet is a result of a high pressure leak through a wall crack or valve stem or any other opening caused by an accident or failure to a high pressure device. Computational Fluid Dynamics, CFD, was used to study the phenomena and its effect on the surrounding equipment.
A. Abdi M., Hawboldt, and K. Hussain A. 'Gas Behaviour during Loading and Unloading: Need for Standard Gas Behaviour Tests', Proceedings of the 2006 International Marine CNG Standard Forum, St. John's, NL, Canada, November 7-9, 2006.

Abstract: The results of preliminary dynamic simulation of loading and unloading with emphasis on accuracy of the existing thermodynamic models were presented. It was shown that current models failed to predict the state of the fluid under high pressure low temperature conditions prevailing in the majority of marine CNG loading unloading systems. The presentation also discussed the need for standard fluid behaviour tests particular to marine CNG systems.
Jassim, E., Abedinzadegan Abdi M., and Muzychka Y. 'Simulation of Natural Gas Flow through Complex Geometries Using Computational Fluid Dynamics', Proceedings of the International Oil and Gas CFD Conference (IOCC), London, UK, 30 November 1 December, 2006.

Abstract: The multi-phase flow of a real multi-component natural gas mixture through various channel shapes was modeled to analyze the flow behaviour and predict the phase change regions and nuclei formation using CFD models. While most researchers constrain their analysis to perfect gases, only a few have considered real gas effects. Due to the scarcity of theoretical, as well as experimental information on cold jet behaviour, we embarked on a work on analyzing the behaviour of real gas (non-ideal) compressible flow through crack and conduits with complex geometries which is being financially supported by Centre for Marine CNG Inc.This information is needed to analyze fracture mechanics of compressed natural gas (CNG) tanks. During the study, the fluid flow and heat transfer phenomena related to the behaviour of a cold jet created from crack on a typical high pressure CNG vessel was simulated. The cold jet phenomenon from the crack was assessed in three areas: the leak flow through the crack, the jet influence on the areas surrounding the crack, and the wall temperature distributions on the adjacent tanks, connecting lines, valves and fittings. The flow field developed through a small orifice with known geometry was simulated. A nozzle shape was selected for the preliminary studies since the inner geometry of a crack can be irregular. For the preliminary study, the working fluid used in the simulation was pure methane. The simulation will be linked to suitable property estimation software using parameter-tuned equations of state to predict real multi-component natural gas flow conditions.
A. Abdi M. and Hawboldt K. 'Gas Treatment Requirements for Marine Transportation of Natural Gas', Proceedings of 2005 International Marine CNG Standard Forum,Delta Hotel, St. John's NL, Canada, August 18-20, 2005.

Abstract: The loading and unloading processes were conceptualized. The specification of natural gas for various transportation technologies was compared. The requirement for processing was outlined based on the existing and future standards.
Marine CNG Risk & Safety Assurance (Craig Young & Jeff Seitz, 2007) A Framework for Risk Assessment and Hazard Identification

Abstract: Concept stage risk assessments are broad in focus and shallow in depth. This paper has outlined a proposed method to completing a risk assessment of a marine transportation chain of CNG by using a matrix approach with key systems and key components. They form bounded areas for individual assessments that are clearly defined and are manageable for a small risk assessment team.

General notes have been presented that will aid the risk assessment team in completing an assessment. This includes pre-planning, completion steps and document recording format. This report describes a process to complete risk assessments for the transportation of compressed natural gas. This includes a general framework to be followed for concept risk assessments as well as specific notes for marine CNG. This report has attempted to address current systems in place as well as being able to handle new designs. This report has been designed to act as a guide and may apply to various transportation chains.
Marine CNG Gas Transfer Systems (J Melville & C Young, 2007) An Evaluation of Potential Gas Transfer Systems for Marine CNG

Abstract: The ability to load and unload marine Compressed Natural Gas (CNG) safely and efficiently is key to the marine CNG value chain. The transfer of high pressure natural gas presents significant technical challenges such as frequent connects and disconnects, the requirement to transfer higher volumes of high pressure natural gas, and the requirement to transfer natural gas that is at pressures ranging up to 4000 psi (250 bar). These parameters are outside of the boundaries currently used for natural gas transfer (pipelines, for example).

Marine CNG implies that transfer systems will bring natural gas from the supply source to market by marine vessel. The supply sources could be onshore or offshore. An onshore supply source would include marine terminals and inshore subsea pipelines, while an offshore supply source would likely be oil and gas production facilities. The potential delivery locations could be offshore/near shore unloading systems to subsea pipeline or an onshore marine terminal or pipeline.

This report presents a set of technical evaluation criteria for fluid transfer systems that could be used for marine CNG and analyzes five transfer systems against this set of criteria. The transfer systems were selected based on the maturity of the design, existing (or modified) solutions highly applicable to marine CNG, as well as solutions that we believe require warrant further research to fill a void in the value chain. The five fluid transfer systems are:
1. Submerged Turret Loading System (STL)
2. Tower Mooring System
3. Blueflex Buoy System
4. Single Anchor Loading System (SAL)
5. Flexible Hoses System.
In addition, the report has developed a number of scenarios for evaluation. These illustrate how the technical criteria can be used to comparatively analyze different project possibilities. This is not intended to define an optimal system, but to provide a framework for evaluation of future projects.

The scope of this report is technical in nature and does not include financial considerations. The analysis demonstrates that the right transfer system for a project depends upon the application, weather conditions at the loading/unloading location and the facilities required for compression, gas drying, heating, and so on. There is potential for transfer systems to evolve to better meet the requirements of marine CNG: specifically, the Flexible Hose systems. All the transfer systems discussed in this report could be optimized to meet the physical conditions, gas volumes, and vessel selection needs of marine CNG. In particular, attention needs to be paid to ensuring both barge and small vessels can be accommodated. The number of potentially effective technical solutions that we have to chose from reflects the experience, competence, and competitive nature of the marine system supply market.