Challenges and Constructability Solutions for New Flare Gas Recovery Modifications in Oil and Gas Refineries: Case Studies for Five Different Flare Stacks

Abstract

Changes and modifications to existing equipment and structures are often required to meet the process industry’s environmental regulations. Creative constructability solutions help minimize shutdown periods that affect production and reduce revenue. It is essential to find engineering constructability solutions for such modifications during shutdown periods while keeping the facilities within regulatory compliance. The case studies presented in this paper include modifications to five different flares in an oil refinery by adding a new flare gas recovery (FGR) to reduce emissions. The case studies examine the challenges to and solutions for projects that involved an oil refinery with FGR modifications for five different flares. These modifications required the bottom portion of existing derricked flare stacks to be removed and replaced with new stack tie-in sections designed to reduce emissions. The objective was to determine a way to accommodate the new FGR tie-in installations without having to perform a total removal of the flare stacks. Among the challenges included checking the capacity of the existing structures to support the dead load of the flare stack as well as temporary wind loads, maneuvering new steel through existing structures and piping leading to irregular geometries, and using temporary steel plate mat foundations in lieu of concrete foundations due to geotechnical concerns and limited excavation clearances. The solutions include reinforcing the existing derrick structures, using hydraulic jacks to control deflection, adding new additional support structures down to grade, and adding a new temporary foundation, or a combination of these solutions. The solutions presented saved the refinery significant time and money in additional downtime in case flare removal would be required. To develop the solutions, three-dimensional laser scanning and structural modeling was used, and a unique deflection-controlled hydraulic jacking process was developed.