Figure 1: Gas Flaring: Courtesy of World Bank
The primary reasons for gas flaring at typical industrial facility includes:
- Old industrial facilities including oil &, chemical, petrochemicals, refineries, Cement, ….
- Lack of infrastructure to capture associated gas with oil production system. This could be due to remote locations, low incentives to recover the gas, low gas quantities or economically unattractive to recover the gas.
- Equipment failure and malfunction including process upsets
- Emergency gas flaring. The frequency of the emergency gas flaring is low, which limits the feasibility of developing and installing equipment to recover it.
- Purge and pilot gas. Purge gas is used to prevent stagnant corrosive fluid in the flare headers, prevent oxygen ingress, and also flare tip flame instability and flashback.
- Valve leakage. Valve leakage increases with time. This can be reduced by upgrading the valves to low leakage valves and continuously monitors the leakage rate.
- Pipeline scraping activities. This is one of the main causes of plant upsets as the different plant equipment is not designed to handle the large liquid slugs associated with the pipeline scraping activities.
- Drilling and workover activities
- Equipment maintenance, startup or shutdown activities
Global Gas Flaring Challenges:
- Small flow at scattered remote locations
- Large flow variation where the flow can range from 1.0 MMSCFD for purge gas to more than 2,000 MSCFD that represents challenge for accurate flow measurements.
- Accurate flow measurements. The most important part of beyond zero-routine flaring strategy is the measurement of the flared gas. The installed meters shall be capable of measure wide range from zero to 100%. Regular flow DP meters will not be able to meet this large range. Recommended flowmeters are the ultrasonic flowmeters.
- Overdesign or oversizing of both flare and relief system to account for uncertainties. Overdesign (oversizing) is one of the many challenges facing the flare and relief systems globally. Potential causes for over design include:
- Safety margin (an insurance policy by designers, suppliers and operators) to accommodate the unforeseen system changes.
- Picking the next higher size. Calculations normally results in sizes that fall between two standard sizes. The engineer picks the next available size instead of reviewing the sizing calculations to check if we can remove or reduce safety factors.
- Uncertainties. Over design margin is normally accepted to account for the unknown especially for new processes, new ventures or lack of accurate data.
- Absence of follow-up and coordination between the different engineering phases from feasibility study, basic engineering to detail engineering.
- Plant flexibility: Every industrial facility operator would love to have his plant and equipment extremely flexible to meet the production demand. Normally, we look at the upper limit when we think about the plant flexibility and forget operating at a lower limit.
- Reluctancy to adopt the new technologies: There are always resistance for trying new technologies in new projects to avoid getting it wrong or to minimize potential delays in the project startup and operation if the technology did not meet the expectations.
- Spare equipment and spare capacity
