Abstract

Past studies in the Shell Petroleum Development Company (SPDC) of Nigeria Limited and literature had suggested 95% as the average combustion efficiency for flow station flares operated in the company. However, with technological advancements, increasing global environmental awareness, the growing concerns on the impacts of gas flaring and the desire to better manage gaseous emissions from SPDC facilities, the need was identified to more accurately evaluate the quality of flares and more importantly, their combustion efficiencies.

Employing the services of Shell Thornton Research Centre, measurements were made on eight representative flares of varying designs and flow rates across the company, to determine their minimum combustion efficiencies using the open-path infrared technique.

Unburned methane and carbon monoxide were not detected in the individual flare exhausts studied and, therefore, minimum combustion efficiencies were calculated by considering the potential quantities of gas that may have been present and yet remained undetected in the plume. Combustion efficiencies based on maximum methane and carbon monoxide levels in the exhaust gases of typical flares operated by SPDC were measured to be in excess of 0.98.

This paper discusses the results of the study with a look at the methodologies and techniques; the processes and assumptions made.

1.Introduction

The impact of crude oil Exploration and Production activities in the Niger Delta has received local and international focus for some time. One of the activities causing the greatest concern is the routine flaring of associated and non-associated gas. Well over One Billion standard cubic feet of gas is flared daily from all the SPDC production facilities. Real and perceived impacts have been claimed by host communities and environmental groups to have occurred to human health, vegetation, soil and the ecosystem by the gaseous emissions from SPDC operations.

SPDC as a good corporate citizen has embarked on a programme to eradicate the need to flare associated gas before the year 2008. The reduction will be achieved in a number of ways including:

  • Finding new outlets for the gas by expanding the local market (principally as a fuel for industrial users)

  • Replacing the non-associated gas currently supplied to customers with associated gas

  • Liquefying and exporting the gas (the Bonny NLNG facility which came onstream in 1999 is planned to liquefy 20% of the gas SPDC currently flares)

  • Careful management of the existing reservoirs to maximise gas production

However, until the need for flaring is eradicated, SPDC is continuing to ensure that the remaining flares burn efficiently with minimal impact on the environment.

A measurement of the combustion efficiency is therefore an important parameter that may be used to assess the impact of flaring operations.

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