Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Analysis of radiation shields for the protection of polymeric patches employed in flare stacks
Submission Author:
Luiz Cesar Coutinho Junior , RJ
Co-Authors:
Luiz Cesar Coutinho Junior, Robson Silva, Jaqueline Diniz da Silva, Fabio Toshio Kanizawa, Kleber Marques Lisbôa, Leandro Alcoforado Sphaier
Presenter: Luiz Cesar Coutinho Junior
doi://10.26678/ABCM.COBEM2023.COB2023-1327
Abstract
Polymeric patches are used for quick in situ damage repair of flare stacks, avoiding costly substitutions or long periods of unavailability of the equipment and plant. However, the very nature of the deployment imposes a significant thermal load to these patches due to the surrounding high temperature flames. Radiation shields were specifically designed and experimentally tested with the purpose of evaluating the adequacy of different configurations and development of concepts to avoid overheating the patch. The experimental apparatus consists of a lidless chamber wherein a sample tube is positioned involved by the patch within radiation shields fixed to its external surface. Two infrared heaters are positioned at the top of the chamber facing the sample and powered with up to 3840 W(e) each to simulate the flames. Thermocouples are positioned in three locations at the base of the patch (below) and another one is fixed to the center of its top side (above); temperature sensors were also fixed to the radiation shields when they are present. A heat flux sensor is employed to monitor the radiation intensity, while an autotransformer is used to control the power delivered to the heaters. A rectified air flow system is installed to continuously renovate the air within the chamber, but mimicking conditions dominated by natural convection. The measurements show that a single shield is already capable of drastically reducing the temperature of the patch, while adding more shields to the stack has a limited benefit. Perforated shields and the associated enhancement of convective heat removal do not compensate the additional radiation flux that is allowed to directly reach the patch through the holes. Radiation shields covering just the patch along the axis of the tube are allowed for a significant amount of radiation to directly reach the patchless portion of the sample, a part of which is conducted to the bottom of the patch overheating it, and thus should be seldom used. Finally, to simulate the aging of the radiation shields, they are coated with high-temperature black paint yielding it significantly less effective at protecting the polymeric patches. The results are expected to guide a design and an implementation of thermal protection systems for polymeric repairs, therefore, allowing to reduce the costly maintenance of flare stacks.
Keywords
Radiation shields, Polymeric repair, thermal radiation, High temperature flame
