Study of Gas-Solid Two Phase Flow in Horizontal Pipeline

Hydrate generation and pipe blockage in long-distance natural gas transmission pipelines hasalways been a major issue affecting the transmission safety. Although considerable progresshave been made in recent years, there is still a long way to go in the study of the hydratesgeneration and plugging prediction in the gas pipelines. In this project, the risk of hydrateformation and parameters that affecting on its formation has been reviewed. One of theparameters that monitor hydrate formation in pipelines is the hydrate formation region (HFR).HFR is defined as the length of the pipeline where hydrate formation is possible. AvoidingHFR by injecting inhibitors is the key to ensure the safe transmission.Accurate prediction of hydrate risk in deep water submarine pipelines is essential for safe gastransportation. The research provides the theoretical guidance for safe and efficient naturalgas resources development and transportation.IntroductionCompared with traditional energy sources such as coal and petroleum, natural gas (NG) hasthe advantages of high calorific value of combustion, low pollution, and low greenhouse gasemissions. Natural gas has become an important energy source for households and industries.The transportation of natural gas is often achieved through underground transmission lines,and the safety of gas transportation deserves our attention (Gue et al ۲۰۱۶). Due to differentfluid properties and complex temperature and pressure changes in the gas transmissionprocess, the generation of gas hydrates is an important factor that threatens the safe operationof gas transmission (Koh ۲۰۰۲).Gas hydrates are crystalline inclusion compounds, which are formed by the contact ofhydrocarbon gases (e.g., methane, ethane, etc.) with free water under particular pressure andtemperature conditions (Solan and Koh ۲۰۰۸). The formation and deposition of gas hydratesin oil and gas transmission pipelines lead to an increase in the flow resistance and may even cause hydrate blockage, a small amount of hydrate formation can reduce the gas flow path,generate throttling, increase the pressure difference in the pipeline, and further accelerate theformation of hydrates. The large amount of hydrate generated can cause plugging of pipelinevalves and equipment, resulting in critical damage and even causing serious pipelineaccidents and casualties. One of the most concerning issues is the hydrate formation in thesubmarine pipelines, where the temperature is very low. Therefore, the prevention andtreatment of hydrates in gas transmission pipelines is particularly necessary. In theconventional strategies of preventing the damage due to hydrates in pipelines, large amountsof thermodynamic hydrate inhibitors, such as methanol or mono-ethylene glycol, areemployed to prevent hydrate formation under the given operating conditions. In this method,the large amounts of thermodynamic inhibitors lead to high production costs (Boxall et al۲۰۰۵). Some researchers proposed an alternative hydrate management method, that is, donothing when no significant blockage risk exists in pipelines. But this method has not beengenerally accepted because the current theoretical models and simulation tools cannotaccurately predict the risk of hydrate blockage in pipelines.

کلیدواژه ها:

natural gas transmission ، horizontal pipeline ، prevention-control measures