Eventos Anais de eventos
ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
INTERFACE TEMPERATURE MEASURMENTS AND CRYSTAL VISUALIZATION DURING WAX DEPOSIT FORMATION ON COLD SURFACES
Submission Author:
Luis Fernando Alzuguir Azevedo , RJ
Co-Authors:
Ricardo Linhares, Luis Fernando Alzuguir Azevedo
Presenter: Luis Fernando Alzuguir Azevedo
doi://10.26678/ABCM.ENCIT2022.CIT22-0213
Abstract
Wax deposition in pipelines is a critical problem for the oil and gas industry. The correct prediction of the wax buildup is important for the planning stages of new projects and optimization of pig’s passage. The current wax deposition models, widely used in the oil industry, account for incorrect deposition mechanisms and, therefore, their accuracy is compromised and dependent on adjustment parameters that fit only specific conditions found empirically. In this work a test section with a simple geometry, well controlled conditions and a model oil with known proprieties is employed. This test section is used to validate simulation models and provide valuable information on the wax deposition mechanisms. A miniature probe was developed to measure the evolution of the deposit-liquid interface temperature and the deposit thickness for three different Reynolds numbers in the laminar regime, causing negligible disturbance to the flow. Differently from what is found in literature, the deposit-liquid interface temperature was found to increase from the wax appearance temperature (WAT) to a temperature between the WAT and the wax disappearance temperature (WDT). As the deposit-liquid interface temperature is never below the WAT, these results indicate that the main mechanism responsible for the deposit growth is the heat transfer followed by phase change, while the molecular diffusion becomes more important in later stages for the deposit aging. The effect of the cooling rate was also investigated. It was found that the cooling rate had no influence on the final deposit thickness and the final deposit-liquid interface temperature. Using a high resolution camera, the transparent plexyglass test section allowed for the acquisition of original images of the deposit formation and growth, as well as the appearance of wax crystals flowing in suspension above the deposit. The images also show the competition between the yield stress of the newly formed deposit and the shear stress imposed by the flowing oil.
Keywords
Wax deposition, petroleum pipelines, flow assurance flowing crystals, interface temperature
