Assessing Hydrate Formation in Natural Gas Pipelines Under Transient Operation / Ocena zjawiska tworzenia się hydratów w warunkach nieustalonego przepływu gazu w gazociągach

2013 ◽  
Vol 58 (1) ◽  
pp. 131-144
Author(s):  
Andrzej Osiadacz
Keyword(s):  
Natural Gas ◽  
Gas Flow ◽  
Hydrate Formation ◽  
Operating Conditions ◽  
Gas Pipelines ◽  
Natural Gas Pipelines ◽  
Hydrate Phase ◽  
Real Gas Effects ◽  
Classical Thermodynamics

This work presents a transient, non-isothermal compressible gas flow model that is combined with a hydrate phase equilibrium model. It enables, to determine whether hydrates could form under existing operating conditions in natural gas pipelines. In particular, to determine the time and location at which the natural gas enters the hydrate formation region. The gas flow is described by a set of partial differential equations resulting from the conservation of mass, momentum, and energy. Real gas effects are determined by the predictive Soave-Redlich-Kwong group contribution method. By means of statistical mechanics, the hydrate model is formulated combined with classical thermodynamics of phase equilibria for systems that contain water and both hydrate forming and non-hydrate forming gases as function of pressure, temperature, and gas composition. To demonstrate the applicability a case study is conducted.

Identification and Mitigation of a Landslide Threatening Four Operating Natural Gas Pipelines

2020 ◽  
Author(s):  
Amir Ahmadipur ◽  
Alexander McKenzie-Johnson ◽  
Ali Ebrahimi ◽  
Anthony H. Rice
Keyword(s):  
Natural Gas ◽  
Landslide Hazard ◽  
Management Process ◽  
Gas Pipelines ◽  
Hazard Management ◽  
Natural Gas Pipelines ◽  
South Central ◽  
Subsurface Investigation ◽  
Landslide Stabilization

Abstract This paper presents a case study of a landslide with the potential to affect four operating high-pressure natural gas pipelines located in the south-central US state of Mississippi. This case study follows a landslide hazard management process: beginning with landslide identification, through pipeline monitoring using strain gauges with an automated early alert system, to detection of landslide movement and its effects on the pipeline, completion of a geotechnical subsurface investigation, conceptual geotechnical mitigation planning, landslide stabilization design and construction, and stress relief excavation. Each step of the landslide hazard management process is described in this case study.

Steady State Performance Simulation of Natural Gas Pipeline Driven by Compressor Stations

2016 ◽  
Author(s):  
S. M. Suleiman ◽  
Y. G. Li
Keyword(s):  
Steady State ◽  
Natural Gas ◽  
Flow Rate ◽  
Operating Conditions ◽  
Simulation Approach ◽  
Gas Pipelines ◽  
Performance Simulation ◽  
Natural Gas Pipelines ◽  
Natural Gas Pipeline ◽  
Pumping Stations

Natural gas pipeline plays an important role in transporting natural gas over a long distance. Its performance and operating behavior are affected by many factors, such as ambient conditions, natural gas flow rate, operation and control of compressor pumping stations, etc. Better understanding of the performance and behavior of an integrated pipeline-compressor system used for gas transmission will be beneficial to both design and operation of natural gas pipelines. This paper introduces a novel steady-state thermodynamic performance simulation approach for natural gas pipelines based on fundamental thermodynamics with the inclusion of the coupling between a pipeline and compressor pumping stations. A pipeline resistance model, a compressor performance model characterized by an empirical compressor map and a pipeline control schedule for the operation of an integrated pipeline-compressor system are included in the simulation approach. The novel approach presented in this paper allows the analysis of the thermodynamic coupling between compressors and pipes and the off-design performance analysis of the integrated pipeline-compressor system. The introduced simulation approach has been applied to the performance simulation of a typical model pipeline driven by multiple centrifugal compressor pumping stations. It is assumed in the pipeline control schedule that the total pressure at the inlet of compressor stations is kept constant when pipeline operating condition changes. Such pipeline operating conditions include varying ambient temperature and varying natural gas volumetric flow rate. The performance behavior of the pipeline corresponding to the change of operating conditions has been successfully simulated. The introduced pipeline performance simulation approach is generic and can be applied to different pipeline-compressor systems.

scholarly journals Hydrate Phase Transition Kinetic Modeling for Nature and Industry–Where Are We and Where Do We Go?

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4149
Author(s):  
Bjørn Kvamme ◽  
Matthew Clarke
Keyword(s):  
Phase Transition ◽  
Natural Gas ◽  
Kinetic Modeling ◽  
Hydrate Formation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Massive Growth ◽  
Hydrate Phase ◽  
Induction Times ◽  
Classical Thermodynamics

Hydrate problems in industry have historically motivated modeling of hydrates and hydrate phase transition dynamics, and much knowledge has been gained during the last fifty years of research. The interest in natural gas hydrate as energy source is increasing rapidly. Parallel to this, there is also a high focus on fluxes of methane from the oceans. A limited portion of the fluxes of methane comes directly from natural gas hydrates but a much larger portion of the fluxes involves hydrate mounds as a dynamic seal that slows down leakage fluxes. In this work we review some of the historical trends in kinetic modeling of hydrate formation and discussion. We also discuss a possible future development over to classical thermodynamics and residual thermodynamics as a platform for all phases, including water phases. This opens up for consistent thermodynamics in which Gibbs free energy for all phases are comparable in terms of stability, and also consistent calculation of enthalpies and entropies. Examples are used to demonstrate various stability limits and how various routes to hydrate formation lead to different hydrates. A reworked Classical Nucleation Theory (CNT) is utilized to illustrate that nucleation of hydrate is, as expected from physics, a nano-scale process in time and space. Induction times, or time for onset of massive growth, on the other hand, are frequently delayed by hydrate film transport barriers that slow down contact between gas and liquid water. It is actually demonstrated that the reworked CNT model is able to predict experimental induction times.

Building a Target Reliability Adaptive to China Onshore Natural Gas Pipeline

2014 ◽  
Author(s):  
Jinyuan Zhang ◽  
Zhenyong Zhang ◽  
Zhifeng Yu ◽  
Wen Wu ◽  
Yingshuai Chen
Keyword(s):  
Natural Gas ◽  
Population Density ◽  
Limit State ◽  
Operating Conditions ◽  
Risk Level ◽  
Ultimate Limit State ◽  
Gas Pipelines ◽  
Natural Gas Pipelines ◽  
Average Population Density ◽  
Average Population

To introduce and apply Reliability-Based Design and Assessment (RBDA) method to China’s onshore natural gas pipelines, China Petroleum Pipeline Engineering Corporation (CPPE) undertook a research project based on achievements from a series of researches sponsored by PRCI. RBDA method aims to maintain a consistent risk level throughout the lifecycle of pipelines by rational designs, professional operations and scientific maintenance. The basis of RBDA method is a set of risk-based reliability targets for pipelines, especially the target value of Ultimate Limit State (ULS). CPPE has developed a database for 37,000km natural gas pipelines in China and defined 148 operating conditions corresponding to various pressures, pipeline diameters, steel grades and pipeline lengths in different location classes. Failure calculation models are modified according to the corrosion and equipment impact under each specified operating condition. While calculating the failure consequences, 20,000 kilometers pipes from different locations classes were selected and statistics of average population density was made. Statistics of failure consequences were made again. Finally, the overall risk level of built natural gas pipelines was calculated. This paper introduces 148 operating conditions, failure probabilities, calculation method regarding failure consequences and average population density of all locations of different classes. Based on target reliability of pipelines set on country level, design and construction plan for newly-built pipelines are optimized by using RBDA method for rationally guiding subsequent operation and maintenance to reach the most optimal and cost-efficient plan in whole lifecycle of pipelines.

Analysis of Two-Phase Stratified Flow and Liquid Hold Up at Dead Ends of T-Sectioned Natural Gas Pipelines

2015 ◽  
Author(s):  
Kaushik Das ◽  
Debashis Basu ◽  
Xihua He ◽  
Stuart Stothoff ◽  
Kevin Supak ◽  
...  
Keyword(s):  
Natural Gas ◽  
Flow Rate ◽  
Liquid Water ◽  
Liquid Velocity ◽  
Analytical Data ◽  
Operating Conditions ◽  
Gas Pipelines ◽  
Internal Corrosion ◽  
Natural Gas Pipelines ◽  
Superficial Liquid Velocity

T-sectioned configurations with a deadleg at the stopple are present in natural gas pipelines, where liquid water may accumulate, increasing the potential for internal corrosion. The objectives of the present study are to explore the pipeline operating conditions under which water enters the deadleg and define an operating protocol to prevent water accumulation in deadlegs. A combined computational fluid dynamics (CFD) experimental and analytical study was conducted to understand the behavior of liquid slugs at the T-junctions with dead ends. The flow equations were solved as an unsteady multiphase (gas and water) incompressible flow problem using the Volume of Fluid (VoF) Method. The analytical calculations were based on a modified form of the macroscopic mechanical energy balance equation. In order to computationally simulate the critical velocity at which water enters the deadleg, the inlet gas flow rate was specified to be a fixed value, while the water flow rate was gradually increased. The liquid entirely bypasses the deadleg until the liquid water velocity exceeds a critical value, which was noted as the critical superficial liquid velocity. The experimental study was conducted using a flow loop to understand the behavior of liquid water at the T-junction and determine the condition when liquid enters the deadleg. The analytical and computed solutions were compared with experimental observations. The computed results follow the same pattern as the experimental and analytical data. Solutions indicate that critical superficial liquid velocity is linearly dependent on superficial inlet gas velocity.

History Beneath the Surface: Natural Gas Pipelines and the National Historic Preservation Act

2004 ◽  
Vol 26 (1) ◽  
pp. 105-122 ◽  
Author(s):  
Christopher Castaneda
Keyword(s):  
Natural Gas ◽  
Historic Preservation ◽  
Advisory Council ◽  
Gas Pipelines ◽  
National Register ◽  
Natural Gas Pipelines ◽  
National Historic Preservation Act

This article is a case study of how natural gas pipelines have been treated under the National Historic Preservation Act (NHPA). It examines three recent pipeline projects that involved determinations of eligibility for the National Register of Historic Places. In one case, a pipeline firm sought an exemption from Section 106 review, and this led to a proposed congressional amendment to the NHPA. In order to forestall a legislative amendment, the Advisory Council on Historic Preservation issued an administrative exemption from Section 106 review for natural gas pipelines. This essay traces the process and events that led to this exemption.

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