Managing process flares due to abnormal situation via design of co-gen system of discontinuous sources
Authors: Eljack Fadwa 
Published: November 2013

Flaring is a recognized environmental issue with multiple implications. Flaring results in economic losses waste of limited material and energy resources, generation of huge amounts of CO2 and other harmful Green House Gases emissions affecting local air quality and contributing to global warming. The bigger impact is on local populations close to industrial cites. Flaring affects their quality of life and health. Yearly, over a 150 billion cubic meters of natural gas are flared globally, the equivalent of 400 million tons CO2 emissions. The numbers seem large in magnitude but the impact is even larger when you consider that 400 million tons of CO2 emissions per year equal the annual emission rate of 77 million cars; and $10-15 billion dollars in losses at current gas prices. It is a common practice in process operation to flare under abnormal situations as a safety precaution; and it is standard operation procedure to also flare during upsets that occur in plant operation, such as equipment malfunction, off-spec production, or emergency shutdowns. Flaring is used to dispose of flammable gases that are either unusable or uneconomical to recover. There are many other causes for flaring that the project team intends on investigating. It should noted that most of the flaring of associated gas from oil production or direct gas venting are the sources of concern that industry must address by better operational practices. Qatar is blessed with the third largest natural gas (NG) reserve in the world and a booming industry covering wide spectrum of valuable gas derivatives. The industrial fortune however comes at a cost in terms of impact on the environment. In 2009, Qatar officially partnered with the World Bank in its program for Global Gas Flaring Reduction, aiming to be a global leader in environmental protection. Flare reduction will directly contribute limiting the emission of harmful gases and the reduction of CO2. Evolving environmental regulations and Qatar's commitment to flare reduction makes better management of industrial processes a research priority for Qatar Literature indicates that the reason for high flaring sources is a combination of lack of end use options for the unwanted gases during operation, and weak environmental regulations. Companies have access to relatively inexpensive NG and often feel that managing associated gases is too much of a hassle. With rising energy and oil prices, industry has motivation to better manage natural resources. In this paper the authors propose a methodology that focuses on use of cogeneration to mitigate flaring while gaining economic and environmental benefits. It is based on simultaneous design and operational optimization where (1) identify key flaring and venting sources, causes and consequences of process upsets that result in flaring and (2) apply the proposed methodology. The novelty in this method is it incorporates design and operational factors in designing combined heat and power system with special emphasis on discontinuous sources due to process upset. A base case study for an ethylene process was used to evaluate the process performance under varying abnormal situation scenarios.