Venting is the controlled release of gases into the atmosphere in the course of oil and gas production operations [4]. Gas flares are the choice disposal option for handling waste hydrocarbon gases because of their ability to burn efficiently [6]. A large number of hydrocarbons are produced when waste oil-gas and oil-gas-water solutions are flared. Flaring is inefficient with combustion being most affected by ambient winds and heating value of the fuel.
Inefficient burning releases raw fuel [7]. The efficiency of flares can be dependent on several factors like composition of the flare stream, Flow rate of flare gases, wind velocity, ambient turbulence, presence of hydrocarbon droplets in the flare stream and presence of water droplets in the flare stream [8].
In combustion, gaseous hydrocarbons react with atmospheric oxygen to form carbon dioxide CO 2 and water. In some waste gases, carbon monoxide CO is the major combustible component. During a combustion reaction, several intermediate products are formed, and eventually, most of them are converted to CO 2 and water. Some quantities of stable intermediate products such as carbon monoxide, hydrogen, and hydrocarbons will escape as emissions [10].
The quantity of hydrocarbon emissions generated is dependent on the degree of combustion. Theoretically, the combustion processes with complete combustion create relatively innocuous gases such as carbon dioxide and water.
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However, because the flaring efficiency depends on wind speeds, stack exit velocity, stoichiometric mixing ratios, and heating value, the flaring in reality is rarely successful in the achievement of complete combustion Leahey and Preston cited in [11]. Reduced combustion efficiency must be regarded as the norm in any operation with flaring [7]. Also, depending on the waste gas composition and other factors, the emissions of pollutants from flaring may consist of unburned fuel components e.
The goal of flare is to convert, through oxidation, substances in the flare gas stream to their safest form possible. In the case of hydrocarbons, the most desirable products are carbon dioxide and water vapour. Sulphur in compounds like hydrogen sulphide is converted to sulphur dioxide. Other oxides, like the oxides of nitrogen, or partially oxygenized compounds like carbon monoxide or formaldehyde are less desirable.
Toxic compounds like poly-nuclear aromatic hydrocarbons, aromatics and volatile organic compounds formed in these diffusion flames may not be fully consumed [8]. The effects of gas flaring under this heading are multifaceted. These effects, have received the most attention and corrective action worldwide. Although the impacts are seen more in developing countries like Nigeria, Angola, Libya etc. The impacts on human, the environment and the economy remain that of a global concern. Nigeria and Russia have been mentioned to be the highest gas flaring countries in all the literatures reviewed with more literatures on the Niger Delta region of Nigeria as it concerns these impacts of gas flaring.
Current developments in these countries to mitigate the effects of gas flaring have been discussed under trends of gas flaring. Environmental issues of gas flaring are generally described in terms of efficiency and emissions [12]. It is widely acknowledged that flaring and venting of associated gas contributes significantly to greenhouse gas GHG emissions and has negative impacts on the environment [1].
The environmental problems caused by flaring are mainly global, but to some extent also regional and local. Global environmental impact is due to the burning of associated or solution gas, which produces carbon dioxide CO 2 and methane CH 4. These emissions increase the concentration of greenhouse gases GHG in the atmosphere, which in turn contributes to global warming [14]. Gas flaring contributes to climate change, which has serious implications for the world [15].
Gas flaring is a major source of greenhouse gases GHG contributing to global warming which could accelerate the problem of climatic change and harsh living conditions on earth, if not checked. Flaring releases carbon dioxide and methane, the two major greenhouse gases. Of these two, methane is actually more harmful than carbon dioxide.
It is also more prevalent in flares that burn at lower efficiency. Those less efficient flares tend to have more moisture and particles in them that reflect heat and are said to have similar effect on the ozone layer like aerosols do []. Of the greenhouse gases researched so far, the global warming potential of a kilogram of methane is estimated to be twenty-one times that of a kilogram of carbon dioxide when the effects are considered over one hundred years [4].
Moreso, flaring may further contribute to local and regional environmental problems, such as acid rain with attendant impact on agriculture, forests and other physical infrastructure [14]. The acid rain which results in environmental degradation including soil and water contamination, and roof erosion.
The incineration of sour gas produces sulphur oxides, which are released into the atmosphere. The end result of these compounds when they combine with atmospheric compounds, namely oxygen and water is what is called acid rain, which produces a lot of negative environmental effects [19]. This Local and regional problem is predominant in developing nations like Nigeria where environmentally unethical gas flaring and has contributed significantly to the degradation of the environment in the region.
The concentration of acid in rain water appears to be higher in the Niger Delta region and decreases further away from the region [20]. The acid rain caused by gas flaring has altered the vegetation of the Niger Delta area. On a casual observation of the flares in the Niger Delta one sees that they are sooty and are evidently burn at low efficiency [16]. When it rains, this soot runs off the roofs of building and pollutes the soil and water aquifers of the people [19].
Gas flaring for instance, has negative effects on the immediate environment, particularly on plant growth and wildlife. Soils of the study area are fast losing their fertility and capacity for sustainable agriculture due to the acidification of the soils by the various pollutants associated with gas flaring in the area [22]. Studies show that gas flaring significantly affects not only the microclimate but also the soil physic-chemical properties of the flare sites Alakpodia, ; Odjugo, cited in [2]. There is an adverse ecological and bacterial spectrum modification by the gas flaring [23].
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For optimum yield of maize within the Niger Delta where gas flaring is taking place, a recommended that maize must not be cultivated within 2 km of the bund wall of the flare sites was made. Research findings show that there is indeed a correlation between environmental variables resulting from gas flaring and the development of certain ailments found in individuals residing in such area. The health impacts of air pollution spreads across a wide area, and those who rely on locally produced food whether from their own production or bought at market, risk contamination [14].
The flares contain widely-recognized toxins, such as benzene, which pollute the air. Local people complain of respiratory problems such as asthma and bronchitis. There have been over identified toxins released from flaring including carcinogens such as benzopyrene, benzene, carbon disulphide CS 2 , carbonyl sulphide CO S and toluene; metals such as mercury, arsenic and chromium; sour gas with H 2 S and SO 2 ; Nitrogen oxides NO x ; Carbon dioxide CO 2 ; and methane CH 4 which contributes to the greenhouse gases [17].
Additionally, the US Environmental Protection Agency EPA has also stated that exposure to benzene causes acute leukemia and a variety of other blood related disorders in humans. World Bank Information on the adverse effects of particulate matter, suggests that gas flaring from Bayelsa alone, would likely cause on a yearly basis, 49 premature deaths, respiratory illness among children and asthma attacks [24]. In a sour gas flare many reduced sulphur species are formed.
Several including hydrogen sulphide and carbon disulphide are potent toxic chemicals. Exposure to H 2 S at concentrations below the level it can be smelled is associated with spontaneous abortion. The most common cause of Thyroid cancers is radioactivity. Thyroid cancers have an elevated median rate ratio in those geographic areas with extensive flaring operations [7]. Environmental contaminants have also been related to endocrine dysfunction, immune dysfunction, reproductive disorders and autoimmune rheumatic diseases.
Gas flaring causes surrounding communities to suffer from increased health risks including premature deaths, respiratory illnesses, asthma and cancer [25]. Another effect that should be addressed is thermal pollution, since there is a limit to which the human body can tolerate the fluxes released during gas flaring. Furthermore, both habitat and structural buildings nearby also have heat threshold [26].
Nigeria provides an appalling example of such a loss. Oil companies in Nigeria flare an estimate 2. From an economic perspective, the flaring of this associated gas is a colossal waste to the communities. The economic cost of total gas flared is quite staggering which implies great investment opportunities for the private sector. Hence, more gas intensive modes of production, greater private sector investment are encouraged in the sector and governments should recycle and seek for more trading opportunities for the gas sector [27].
Apart from the release of greenhouse gases into the atmosphere, gas flares are said to release some As a result of this incineration of the environment, gas flaring has raised temperatures and rendered large areas uninhabitable [21]. All oil fields contain associated gas although in varying quantities. In analogous to the way bubbles appear when the cap is removed from a bottle of carbonated drink, so the associated gas is released when oil is brought up from the deep rock strata in which it is found.
One of the challenges involved in addressing environmental aspects of flaring is identifying how much gas is being released. The difficulty to evaluate the gas flaring emission is to find out the most reliable database and to understand why these databases show different data. The method for estimating emissions from natural gas flaring is based on the volume of vented and flared gas reported to EIA assuming that all gas is flared [10].
A major difficulty in managing flaring and venting is identifying exactly how much gas is coming from the various sources that are contributing to the overall volume flared and vented. The proportion of associated gas to oil Gas Oil Ratio can vary significantly between oil fields. There is debate within the industry regarding the extent to which it is possible to measure gas flow rates accurately under such varied conditions with the measuring devices presently available on the market.
Although some oil companies and equipment manufacturers would disagree, low-pressure gas rate measurement can be a significant problem. Others believe that the best way to obtain consistent data is to base it on estimates and calculations [4]. Smaller flaring and venting volumes are typically estimated by first measuring the gas-oil ratio in the crude oil stream and then inferring the amount of gas flared or vented from the measured amount of oil produced.
Larger-volume sites may use orifice plates or other measurement devices. Battery operators are not currently required to report the composition of gas being flared or vented on an on-going basis. Thus, there is no direct way to determine the composition of solution gas flared. Apart from the physical and environmental differences among battery sites, there are significant variations in the composition and phase of materials being flared and vented [28].
Despite the ubiquity of flares in the world, there have been relatively few successful studies investigating their emissions and most have focused on quantifying gasphase carbon conversion efficiencies. Progress has been hampered by the inherent difficulties in accurately sampling emissions from an unconfined, turbulent, inhomogeneous, elevated plume of a flare. General understanding is further complicated by the incredibly wide range of operating conditions i. There are various methods of detecting air pollution in an industrial environment.
These experimental methods are capital intensive; hence only large or well-established industries can afford them [30]. Accurate and transparent determination of environmental impacts of flaring and venting of gas associated with oil production, and potential benefits of mitigation, are severely hampered by the lack of publically available gas composition data [31]. Only very limited data are available that describe methane emissions from natural gas and oil activities.
Industrial Gas Flaring Practices
Because natural gas and oil activities are complex, it is not easy to define simple relationships between emissions and gross descriptors of the activities undertaken. The following data have been identified: Different methods, emission factors, estimations and ratios from International organization and recognized environmental agency and boards globally have been used to give statistical data and estimation of both the quantity of gas flared and the emissions from gas flaring.
The seemingly absence of a single global method, emission factor and estimation procedure used in the oil and gas industry all over the world to determine the volume of gas flared and its emissions be it from complete or incomplete combustion, sweet or sulphur present hydrocarbons has pose a continuous problem in determining the actual impact of gas flaring and its emissions on human and its role in environmental degradation both at a local and global level. Subject to this, researchers from wide range of disciplines such as environmentalist, engineers etc.
This approach so far includes analytical studies, numerical studies, modelling, computer simulations, etc. The goal behind each study being to mitigate the effects of gas flaring. Abdulkareem [30] carried out experimental analysis on gas flare to determine the extent of air pollution by the petroleum refinery industry on the concentrations of NO, CO, SO 2 and total hydrocarbon. Pollutant concentration from the flare point was modelled using visual basic.
The result of the simulation of model developed from the modified principle of gaseous dispersion by Gaussian showed a good agreement with the experimental results. The quality of air with respect to the pollutant measured was unacceptable when compared with Federal Environmental Protection Agency Nigeria set limit. The dispersion pattern of pollutants showed that the extent of spreading is dependent on nearness to the source of flare, wind speed, temperature etc.
In the University of Alberta flare research project experiments, gases and liquids flared at battery sites in western Canadian sedimentary basin were characterized with samples drawn at the base of the flare stacks so that they would be representative of the materials being flared and found no liquid present at any of the sites tested.
Hence, no correlation was found between smoke emissions from the flare and the compositional variations of the flare stream and statistical argument that flare streams containing liquids are far less likely to exist than previously assumed [26]. A air flame was simulated for quiescent conditions and temperature and concentration profiles were compared to experimental data. Results show that high momentum flames are more sensitive to the crosswind problem as the jet velocity increases. Also pollutant concentrations became quite large at an unstable condition on the ground level.
The results were compared with experimental data obtained from a gas flare in petroleum company in an industrial city of Nigeria. Also the effects of some parameters i. Volumes of gas flared at different flow station were collected as well as geometrical parameters. The results of simulation of model developed based on the principles of gaseous dispersion by Gaussian showed a good agreement with dispersion pattern. The results showed that the dispersion pattern of pollutants at ground level depends on the volume of gas flared, wind speed, velocity of discharge and nearness to the source of flaring.
Hence, continuous gas flaring irrespective of the quantity deposited in the immediate environment will in long run lead to change in the physicochemical properties of soil. Model equations that represent ground level concentration of pollutants were presented.
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The model equations were simulated using QBasic programme to show the operation and behaviour of the system. Sonibare [34] reviewed for the purpose of air pollution control strategy the significance of these gaseous emissions in the formation of secondary air pollutants in the atmosphere. Three important secondary air pollutants formed in the atmosphere due to the presence of primary air pollutants from natural gas flares were reviewed with their environmental impacts and formation mechanisms discussed for the purpose of control measures.
Johnson [35] developed quantitative model for yearly averaged solution gas flare efficiency and GHG prediction, but need industry flare composition data to start making comprehensive calculations of emissions inventories and GHG reduction. Two flow stations, Agbada 1 and 2 of Shell Petroleum Development Corporation were monitored while Eneka village with no history of gas flaring was introduced as control for comparison for a period of three months.
Results show that CO 2 , CO and associated air pollutants gave significant and more or less worrisome concentrations at the choice sites evident in recorded values in comparison to the Control site and reference regulatory set standard. Further m distance from flare stack did not show statistically significant difference in terms of emissions and risk of death from carbon dioxide poisoning could threaten if there are no interventions.
The volume of gas flare and conditions of flare as well as experimental data on concentration were collated. The dispersion model based on the principle of Gaussian distribution. The simulated results shows the dispersion pattern of pollutants from gas flaring and the effect of change in the volume of gas flared, stack efficiency, wind speed and atmospheric stability on the concentrations of pollutants from gas flaring were investigated. The Eulerian model was used for the prediction of air pollutants in some gas flare locations in Niger Delta region of Nigeria.
A continuity equation mass balance that incorporates second order reaction schemes for the generation of pollutants at source or in the ensuing atmosphere was used to characterize the n species in the fluid element and the finite difference method the Crank-Nicholson formulation was applied for the numerical scheme. Different simulations were carried out at ground levels and altitudes and the Eulerian model provided a satisfactory prediction of the spatial and transient concentration profiles for the pollutants in the gas flares.
For pilot-scale flares in the absence of cross flow, Pohl et al. Flaring creates other pollutant emissions such as particulate matter PM in the form of soot or black carbon BC. Quantitative emission measurements were performed on lab-scale flares for a range of burner diameters, exit velocities, and fuel compositions. Total soot emissions from turbulent jet-diffusion flames representative of associated gas flares were studied.
Both a gravimetric sampling method and a laser induced incandescence instrument were used in conjunction with a hood sampling system to measure the soot yield per mass of fuel burned for a wide range of conditions, including five different burner exit diameters, a broad range of flow rates, and six different fuel mixtures. A specific sampling protocol was developed for these measurements, based on current PM test protocols for stationary sources and diesel engines.
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Visit our Beautiful Books page and find lovely books for kids, photography lovers and more. Back cover copy With the consequences of the world's gas flaring practicesonly just beginning to be understood or even studied, this volumeis the first in decades to tackle a very difficult hot-button issuefor our time that could significantly reduce CO2 emissions andtheir affect on global warming.
When properly used and maintained, flare gas systems can be asafe and reliable technology for system protection and incontrolling emissions stemming from emergency releases.
Cheremisinoff Nicholas P. Industrial Gas Flaring Practices
Further to this, there are oftenmisconceptions and misrepresentations on flaring efficiencies. Thishas led to under reporting of releases of toxins withincommunities. Flares are widely used throughout the oil refining andpetrochemical industries to manage waste gases and as a means ofsafety control of over pressurization of process units. Bothindustry and environmental statutes concerning the regulation offlares characterize flaring as a safe practice that is capable ofcontrolling air emissions to a high level of efficiency.
Butflaring operations are conducted far more frequently than systemswere originally intended to operate, and aging refineries andpetrochemical plants have given low priority to the criticalmaintenance and replacement of flare system components. Theconsequences have been far greater emissions than are generallyreported along with serious accidents that have caused loss oflives and extensive damages to facility infrastructure andcommunity property. This volume is intended as a technical reference for refineriesand chemical plants. The information contained herein is the resultof reviewing the general literature of flaring options andtechnologies, reviewing industry and U.
EPA-published studies, and examining some of the practices of certain refinery operationswhere information has been accessible. Industrial Gas Flaring Practices Tackles a very difficult, misunderstood, and often overlookedtopic: Shows how dealing with this subject is a very significant steptoward reducing worldwide CO2 emissions, and thus hopefully helpingto reverse or slow down climate change. Is the only comprehensive volume of its kind dealing with gasflaring from a technical and environmental point of view.