Flares and Vents

Flare and vent systems represent the last line of defence in the safe emergency disposal of unwanted products released from emergency relief or depressurisation systems. It is vitally important that the flare system is well designed and maintained to achieve safe operation under all circumstances with acceptably small environmental impact. This course offers the design engineer faced with the task of designing or assessing the design of the flare system the necessary tools. Typical arrangements of various flare systems, identifying the purpose and importance of each component, are followed by an examination of gas combustion, air requirements, excess air and the how combustion affects emissions.

Differences between ground and elevated flares and their typical construction are explained, including the various types of elevated flare tip, together with methods of combining ground and elevated flares into an integrated system. Techniques for achieving good smokeless operation on elevated flare tips, such as air-blown, steam injected and sonic flares are reviewed and contrasted. Performance in terms of radiation, noise, emissions and utility requirements are identified together with their effects upon personnel and adjacent facilities.

Liquid knockout facilities are examined and appropriate system requirements identified to prevent liquid carryover to the flare. Seal pot systems, often used in flare staging, are considered and alternative methods of providing and disposing of the seal water are compared. Systems for flare gas recovery are examined and types of compressor are compared. The need for elevated flare stack purging is considered and alternative approaches using fuel and inert gases are compared. At each stage of the course, recommendations regarding essential maintenance and repair of the components of the flare system will be developed. Throughout the course the relevant contents of established specifications for flare systems, such as API 520 and API 521, are developed and related to the balance of the course content.