I hereby certify that I am responsible for the work submitted in this project, that the original work is mine except as noted in the references and acknowledgments, and that the original work contained herein has not been taken or performed by unspecified sources or persons. This paper discusses the effectiveness of N-methyl-2-pyrrolidone (NMP) as a kinetic hydrate inhibitor compared to polyvinylpyrrolidone (PVP). This will help to understand the phase equilibrium behavior and the effect on the phase equilibrium line using different inhibitors; EMS and PVP.
Due to insufficient experimental data for this study in the open literature and the clogging of methane hydrate with regard to pipeline flow assurance, the production of hydrate inhibitor research has become important to address hydrate formation in pipelines. The experiment is carried out using HYDREVAL equipment at high pressure and low temperature to obtain the phase equilibrium of NMP and PVP. The findings of this study will inform better design of industrial operations in such a way that prevention of gas hydrate formation can be achieved by understanding gas hydrate and inhibitor behavior.
First, praise to Most Graceful, Allah SWT for his blessings and guidance, through high and low, I can complete my final year project without any difficulty. I would like to express my gratitude to both my parents who prayed for my success and constantly supported and encouraged me on any decision made. My deepest appreciation goes to my final year project leader, Siti Sarah Binti Salehudin, for her trust and support towards my project.
Last but not least, thanks also go to the technicians who spent their time helping to handle chemicals and equipment throughout this project.
INTRODUCTION
- Background of Study
- Problem Statement
- Objectives
- Scope of Study
Rapid growth of methane hydrate in the pipeline can block the flow path, rupture the pipeline, and form ice balls that can act as dangerous projectile movement during remediation. Although the thermodynamic inhibitor such as methanol and mono-ethylene glycol (MEG) is effective in preventing the formation of methane hydrate in a pipeline, the concentration of methanol and MEG that must be added is high as well as expensive. Alternatively, low dose hydrate inhibitor (LDHI) such kinetic inhibitor is able to provide smaller volume used to inhibit methane hydrate.
Since the concept of LHDI works at low dosing rates, an investigation of chemical that can act as kinetic hydrate inhibitor (KHI) is required to reduce the presence of methane hydrate in the pipeline. To compare and evaluate the effectiveness of NMP with commercial hydrate inhibitor, PVP in the process of hydrate dissociation. This project requires a comprehensive understanding of methane hydrate formation in relation to factors leading to methane hydrate formation, associated risk of methane hydrate formation is pipeline as well as effective and economical prevention methods.
NMP and PVP are used to serve as LHDI and therefore the effectiveness of NMP as KHI is being studied and experimented. Laboratory work will be conducted to demonstrate the effectiveness of the NMP as a KHI. The weight percent use of NMP in this study should be less than 1 wt% to meet the concept of LDHI.
This device is designed to experimentally determine the thermodynamic stability of hydrate in the oil and gas phase.
LITERATURE REVIEW
- Hydrates
- Risk of Hydrate Formation
- Hydrate Countermeasure
- Polyvinylpyrrolidone
- N-Methyl-2-Pyrrolidone
According to Carrol (2003), there is another phenomenon that increases hydrate formation; turbulence, nucleation site and free water. By observing the hydrate formation curve, the area on the left side of the curve shows the hydrate formation area, while the area on the right side is hydrate free [1]. Transient operations such as start-up, shutdown and blowdown are very likely to trigger hydrate blockages, as this is when the temperature of the production system begins to move into the hydrate formation zone.
Underwater equipment such as valve and manifold will be damaged if not insulated when hydrates form. Increasing the risk of hydrate formation in long-distance pipelines and the remediation process will become more complex due to the precision of the location of the water retention. The formation of hydrates will take place during the cold start of the well - until the well reaches a sufficiently warm temperature from production.
The Pig tool is used in the pipe mainly to clean the pipe in which the tool fits snugly in the pipe and scrapes into it. Thus, it is important to ensure that there are no points in the pipeline drop in the region of hydrate formation. Thermal control is one of the methods of heat to prevent hydrate, which provides sufficient insulation in the pipeline and underwater equipment that prevents the temperature of the pipeline and equipment from falling below the zone of hydrate formation.
This will allow the hydrate to melt, but it takes some time for the hydrate to melt. As for the hydrate inhibitor, the chemical is used to prevent the formation of hydrate particles by shifting the balance of hydrocarbons resulting in less severe hydrate formation conditions. It is important to note that the hydrate inhibitor does not prevent the formation of hydrate, but merely inhibits it.
Thermodynamic inhibitor tends to shift the hydrate state to less severe state by chemical potential change of water phase leading to lower temperature and higher pressure of hydrate dissociation curve. This property made the PVP able to prevent the hydrate formation by eliminating the water which is the host molecule for hydrate formation. Moreover, NMP is a stable, basic substance that is polar and there is however no possibility of hydrogen bonding.
This is likely to ensure that NMP does not form a host molecule for hydrate formation. The fact that NMP can recover a hydrocarbon and has excellent solvent properties, there is a possibility that NMP can act as a KHI in reducing the occurrence of hydrate formation in the pipeline.
![Figure 1: Hydrate formation curve [1].](https://thumb-ap.123doks.com/thumbv2/azpdforg/10376094.0/15.918.201.769.527.848/figure-1-hydrate-formation-curve-1.webp)
METHODOLOGY
- Research Methodology
- Gantt chart
- Equipment Required
- Materials
- Experimental Procedure
5 Submission of the Final Draft-Report 6 Submission of the Dissertation (Bund Bound) 7 Submission of the Technical Paper 8 Viva. In this experiment, HYDREVAL equipment can be used to determine the formation and dissolution of the hydrate state and to evaluate the effectiveness of the inhibitor. The device is based on motor-driven PVT cell, which can be used in different configurations to perform the required test.
The equipment chamber is enclosed at one end by the piston of the embedded pump and the other by a dedicated cell head made of titanium alloy. Parameters such as pressure, temperature and volume can be monitored and observed through available software for interpretation. Note that the mass of solution is the sum of 1 g of sample and the mass of distilled water, which equals 100 g.
Therefore, the amount of distilled water required to produce 1 wt% NMP and PVP solution is 99 g. 3.6. Experimental procedure. The magnetic stirrer was set at 600 rpm to dissolve NMP in distilled water. 6) 25 cc of prepared sample was loaded above the piston by using a pump to fill the void volume above the piston and the piston was set to 80 cc.
55cc of methane gas was charged into the void volume above the piston once the prepared sample was loaded. The pressure can be controlled by a pressure gauge at the gas tank and the equipment was left for two hours to ensure that the pressure fully stabilized and no leakage occurred around the sapphire cell.
RESULTS AND DISCUSSION
In Figure 8, as the temperature decreases from point A to point B, energy loss of gas in the sapphire cell results in a decrease in pressure. This is because methane gas has been converted into hydrate in the sapphire cell. Once the temperature starts to rise from point C (a heating process takes place), the methane hydrate formed in the sapphire cell starts to dissociate.
In Figure 9, the volume-temperature diagram of 1 wt% NMP with methane hydrate shows that there is no change in total volume even though the temperature is changing. Therefore, the diagram shows that the volume is constant throughout the occurrence of hydrate formation and dissociation in the sapphire cell. From the phase diagram, the two plots were made to observe the effect of shifting the 1 wt% NMP phase boundary with the pure methane phase boundary.
From the observation, 1 wt % NMP temperature limit shifted slightly to the left as the pressure increases. Note that area below the phase boundary is considered hydrate-free zone, while area above the phase boundary is hydrate stability zone. Since 1 wt % NMP shifted temperature boundary slightly to the left of pure methane phase boundary, it widened the area of hydrate-free zone and finally reduced the area of hydrate stability zone.
The comparison of 1wt % NMP, 1wt % PVP and the phase boundary of pure methane is shown in Figure 11. In Figure 11, it is clearly seen that although 1 wt % NMP are able to shift the phase boundary to the left of the methane phase boundary of pure, it is not as efficient as 1 wt % PVP which give the largest displacement phase boundary.
CONCLUSION AND RECOMMENDATION
Jassim, Hydrate formation and deposition in natural gas flow line, LAP LAMBERT Academic Publishing GmbH & Co.
