Complex Flare Network Analysis Best Practices

Many petrochemical companies are currently engaged in flare systems review and upgrade projects. They wish to ensure continuing safe operations, to maximize the use of their existing flare systems, and to minimize the need for modifying existing flare structures or building new ones. This presentation summarizes the stages involved in a comprehensive flare systems evaluation, outlines the design criteria to be addressed, and provides guidance on best practices for this vital part of a plant's safety systems. A case study involving a complex flare network is also presented.

A primary component to help ensure the mechanical integrity of any refinery or petrochemical plant is a well-designed pressure relief system, typically comprising multiple pressure relief valves connected to a flare system. The pressure relief valve ensures mechanical integrity of equipment by opening at a specific pressure, during an overpressure situation, thereby preventing a rupture of the equipment. The flare system then safely disposes of any potentially hazardous fluid vented during the overpressure scenario, by separating the liquids and vapors, and burning the vapors from a flare stack. 

The Texas City incident in March 2005 demonstrated the catastrophic consequences that can result from an improperly designed effluent handling system. Recommendations made by the US Chemical Safety Board following their incident investigation now have many petrochemical companies currently engaging in reviews of their effluent handling and flare systems. They wish to ensure continuing safe operations, to eliminate hazardous atmospheric releases, to maximize the use of their existing flare systems, and to minimize the need for modifying existing flare structures or building new ones.

Broadly speaking, a flare systems analysis can by summarized in the main points below:

• Establish Global Overpressure Scenarios
• Verify Relief Device Capacity
• Construct Flare Networks Model
• Analyze Flare Systems Hydraulics
• Assess Design Checks and Resolve Deficiencies
• Re-analyze Flare Systems Hydraulics

With Process Safety Office^® SuperChems™, ioMosaic was able to create a dynamic model of a very complex flare network where all other software packages failed. Once developed, the model is easily modified to stay current with changes to the system.