Introduction

Everybody has seen flares burning in industrial plants such as petroleum refineries, chemical plants, natural gas processing plants as well as at oil or gas production sites having oil wells, gas wells, offshore oil and gas rigs and landfills. The flare has always been a symbol for stable production, but nowadays a flameless flare may be a symbol for stable and clean production. The size and brightness of the resulting flame in not related to the reliability and well operability of the plant, but also depends upon the flammable component compositions and the flow rates. Burning flammable components which are vented from processing units can be happened during normal operations and process upsets conditions. The primary function of flares is providing safe conditions to protect the facility, employees and the surrounding environment. On the other hand, flaring these components also creates trade-off emissions, such as nitrogen oxides (NOx), sulfur oxides (SOx), greenhouse gases (CO, CO2) and unburned hydrocarbons. Damages to the surrounding caused by the destruction of these valuable and expensive raw materials are unavoidable because of safety and continuity of the process. As these products, destroyed through burning in the stack, have already been treated in the refining process, their value is that of an enriched product. Recovering and reuse of these waste components before they are combusted by the flare is preferable because of not venting undesired component to the environment and also providing new sources of fuel or feed stock. For creating the sense about flaring it has been estimated that, in 2006 the global gas flaring were 168 billion cubic meters (BCM) which represents 25% of the natural gas consumption of the USA. If it were to reach market, this quantity of gas (at a nominal value of $5.62 per 1000 cubic feet [1]) would be worth $29.8 billion USD [2]. It is also estimated that the gas flared annually is equivalent to 30% of the European Union's gas consumption, or 75% of Russia's gas exports. The gas flared yearly also represents more than the combined gas consumption of Central and South America. It should be noted that the annual 35 BCM (or 1.2 trillion cubic feet) of gas flared in Africa alone is equivalent to half of that continent's power consumption [3]. It is also claimed that 5% of the world's natural gas production is wasted by burning or "flaring" unused gas each year [4].

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