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Examination of Zero Flare Benefits

As stated previously, environmental improvement without legislation can only be achieved alongside acceptable financial reward. The experience in Norway clearly influenced financial reward to the extent that new technology was developed. Today the technology is available for all to use. The cost of retrofit on existing offshore facilities often draws into question the benefit of full zero flare solutions but many operators have accepted flare gas recovery or zero flaring as a requirement for new facilities. It is important, however, for all existing facilities to re-examine the full benefits of full installation of zero flare systems, or to consider where partial installation will be of benefit.

Figure 1: Gas Flared Onshore and Offshore (tonnes) 

Maintenance Issues

One of the main areas of real benefit for operators using zero flaring systems is the major reduction in maintenance requirements of the flare system. To understand the full impact of the maintenance benefit on both new and older facilities, it inecessary to understand a little of the requirements of the flare system itself.

The flare system is a key safety system, unique in that it cannot be accessed for maintenance at any time other than complete shutdown and degassing of the entire process facility. Failure of components within the flare system will at best cause safety concern, and at worst ensure an unexpected facility shutdown. If uncorrected, damage to the flare system can impact operational integrity of the process facility. The major cause of component failure on the flare system is low flowrate flaring when the flame wafts about in the breeze impinging directly on the flare tip itself, the pilots and any other equipment on the flare deck. Any flare system, and particularly one located on vertical towers, is susceptible to dropped objects. There is usually a relatively small top flare deck and if any part of the flare system were to fail, there becomes a risk of dropped objects. Typical dropped objects may include areas of the outer wind fence on the flare itself damaged by heat load and battered by wind. Other items susceptible to breaking away from the flare will include elements of the pilot and ignition assembly. There is plenty of experience within the industry as a whole, of pilot nozzles failing, or parts of the ignition rods breaking free. In more extreme cases, parts of the flare have fallen. Finally the flare deck will require periodic repair particularly if during the process upset liquid has been flared resulting in very high heat loads on the flare deck.

Figure 2: Sources of Norwegian CO₂ emissions, 2001

Figure 3 shows evidence of heat load on the flare deck itself, pilots and ignition systems have been removed from previous damage, and the flare tips themselves are showing some signs of thermal damage. Note there are no deck railings. Railings on a flare deck that have been subjected to flame impingement are dangerous. It is better not to fit them in the first place or to specify removable railings.

Figure 3

Every facility will have different requirements regarding flare system maintenance. Where dropped objects are critical, for example on vertical flare towers with process equipment, or personnel access below some offshore installations have taken to a policy of adopting routine helicopter surveys of the flare system conditions, including looking for dropped objects. Such surveys may take place routinely twice a year, involving a shuttle helicopter and specialist photographer. These services are offered by companies such as PCC Sterling Limited (Argo Flare Services division). If problems are identified within such routine inspections then more frequent inspection schedules are arranged to quantify risks, and planning is put in place for a shutdown to carry out remedial work. Some installations have now introduced a routine shutdown to carry out detailed flare deck and systems inspections every two or three years and flare tip change every five years or so. The cost of such a programme can best be estimated by individual installations but excluding losses in production over a minimum period of two to three days for a quick flare system, only shutdown will be approaching £500,000. To reduce these costs, the following considerations may be made:

• simplify flare system by removing non-essential equipment such as flare pilots and use ignition system compatible with no pilots;
• adopt a zero flaring approach, where the flare is normally not lit, and will only be ignited on demand; or
• remove all hand railings if installed permanently, which are a safety hazard.

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