Air Quality and the Petroleum Industry

Chapter 21

Air Quality and the Petroleum Industry G.S. Cholakov University of Chemical Technology and Metallurgy, Sofia, Bulgaria E-mail: [email protected]

Chapter Outline 1. Introduction 2. Sustainable Air Quality and the Petroleum Industry 2.1 Strategies for Sustaining Air Quality 2.2 Estimation of the Impact of Air Pollutants 3. Impact of the Petroleum Industry on Air Quality 3.1 Production of Petroleum 3.2 Transportation of Petroleum 3.3 Refining of Petroleum 3.3.1 Overview 3.3.2 Petroleum Processing Operations

563 565 565 567 570 570 571 572 574

3.4 Transportation and Marketing of Petroleum Products 4. Control and Management of Air Pollution in the Petroleum Industry 4.1 Storage and Handling Emissions 4.2 Fugitive Emissions 4.3 Process Emissions 4.4 Secondary Emissions 5. Perspectives and Concluding Remarks References

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582 583 584 584 584 585 585

574

1. INTRODUCTION In 2013 the world obtained 87% of its energy from coal, oil and natural gas [1]. However, in the early days the humans started with renewable energy. According to Greek mythology, the Titan Prometheus gave fire to the people. Most likely his torch was from biomass. Leaving the myths aside, we might assume that the primitive human quickly learnt how to rub two dry Comprehensive Analytical Chemistry, Vol. 73. http://dx.doi.org/10.1016/bs.coac.2016.02.013 Copyright © 2016 Elsevier B.V. All rights reserved.

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biomass pieces (twigs), until they ignite e and eventually some 350,000 years ago e moved on towards civilization. Environmental pollution had also become a significant problem long ago. King Edward I in 1273 gave a striking example of an ancient ‘environmental law’ declaring that ‘.whosoever shall be found guilty of burning coal shall suffer the loss of his head.’ [2]. In the beginning of the 20th century petroleum and its products e energy bearers (fuels: gasoline, diesel, etc.), energy savers (lubricants) and basic petrochemicals, combined with easier extraction, transportation and storage e emerged as the best choice for obtaining energy, especially for transport and organic syntheses. Petroleum and its fuels were liquid and easy for processing and transportation, stable in storage, performed well in the combustion installations with less smoke and ashes, than coal. The energy systems from early times have been dominated by those, into which the potential chemical energy of nonrenewable and renewable fuels is released by combustion. Their main features are the fuel and the combustion installation. The original fuel resource is extracted (fossils), grown (algae, industrial crops) or collected (waste biomass) and more or less processed (ie, ‘refined’) to obtain energy bearers and other products. Transport operations and storage are performed at the site, where the resource is obtained and at the site where it is processed, but also between them. The energy bearers have also to be transported to and stored at the point of their combustion. The petroleum industry is often considered only as an industry which refines crude oil. However, from the point of view of its impact on environment and air quality in particular, it is more appropriate to estimate it as an interrelated system of polluting activities, including excavation and production of crude oil; crude oil transportation and transformation into energy bearers, energy savers and petrochemicals; transportation, marketing and use of petroleum products [3]. The air pollution from the use of petroleum products, despite its huge contribution, cannot be presented in this chapter because of the lack of space. Petroleum industry processes also gaseous hydrocarbons, which accompany crude oils or are produced in their refining. Hydrocarbon gases are the most environmentally compatible fossil fuel alternative and the natural gas industry has become an industry of its own. So, within the limitations of our presentation, we cannot consider also the impact on air quality of natural gas, shale gas, biogases, etc. but should note that their most important component - methane, is a very powerful greenhouse gas. In the previous context the petroleum industry is the industry which in 2014 turned around 4200 million tonnes of crude oil [4] into more than 2500 products. Typical derivatives are liquefied petroleum gas (LPG), gasoline, kerosene, aviation fuel, diesel fuel, fuel oils, lubricants, basic feedstocks and chemicals for the petrochemical industry (eg, benzene, toluene, xylenes, phenol and acetone, etc.). Larger refineries might be integrated with petrochemical plants, delivering to the society anything from pure chemical compounds with more sophisticated

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chemical structure (eg, amines, ethanol amines, glycols, butadiene, isoprene, etc.) to synthetic polymers and elastomers. Refineries usually also synthesise gasoline additives (alkylates, ethers like methyl tertiary butyl ether, etc.). Some of them may produce also lubricants and/or additives for lubricants.

2. SUSTAINABLE AIR QUALITY AND THE PETROLEUM INDUSTRY 2.1 Strategies for Sustaining Air Quality The main task of air pollution management is to ensure air quality, defined by specifications of pollution indicators (typically, sets of limited concentrations of criteria and relevant specific pollutants). Because pollutant rates are varying with time, pollutant concentrations are determined at the time of measurement. The sum of these for a given time estimates the rates of pollutant emissions. These rates, and therefore the air quality within a targeted area, are monitored by stationary and/or mobile measuring stations. The quality of air within a given area is determined by the polluting substances, created from anthropogenic and natural sources in and out of it. Natural sources, however, are not easily controlled by humans. So, to prevent irreversible damage to air quality, environmental engineering concentrates its efforts on control of human polluting activities (polluters) inside the area and negotiating trans-boundary imissions. Emission sources can be classified as stationary (in excavation and petroleum refining, power generation, etc.) and as mobile (transportation activities). The Corinair databases of the European Environment Agency (EEA) present data for polluting activities, applying a detailed classification and identification with Selected Nomenclature for Air Pollution (SNAP) codes [5]. They contain description of the respective activities, methods for measurement and emission factors, pollution control technologies, relevant documents, etc. Specific information for the petroleum industry can be obtained also from the databases of the US environmental protection agency (US EPA) [6]. Both sources are very useful for preparing detailed emission inventories, company reports and other official documents, so they are widely employed. However, for our presentation it is more appropriate to use a most general and easily understandable classification, applicable to the selection of measuring and control strategies. A suitable US EPA classification defines four types of industrial emissions e storage and handling of volatile organic compounds (VOCs), fugitive emissions, process emissions and secondary emissions of VOCs from an inert carrier. Three of these types contain VOCs, identified as substances with normal boiling temperatures below 260 C. These include a wide range of low-molecular-mass organic compounds which are gases or liquids at normal conditions: hydrocarbons, alcohols, ethers, aldehydes, ketones, carbonic acids, halogenated compounds, etc. Applied to fuels, this definition includes all gaseous fuels; gasoline and kerosene gasoil cuts, obtained below 260 C at atmospheric pressure; and their portions in crude oils

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and finished products. Obviously, in the petroleum industry huge quantities of VOCs are being produced, stored and handled/manipulated (ie, transferred from one vessel to another) not only in crude oil excavation and refineries, but also at gasoline stations, marketing terminals, etc. Fugitive emissions from seals usually consist of VOCs. However, industrial emissions often contain higher boiling substances, leaking from hot and pressurized streams. In the latter case, the higher boiling substances condense at some distance from the emission source. Process emissions might contain different pollutants, depending on the particular process and technology. Most of the criteria pollutants, common to industrial process emissions, come from combustion processes. Secondary emissions of VOCs might be emitted from polluted water, solid and oily residuals, sludge, wastes, etc. The above classification can be applied to a wide range of stationary sources e power stations, household energy use, etc. It is also suitable to mobile sources, where storage and handling emissions are evaporating from the car tank, fugitive emissions, from the fuel supply equipment and process emissions, from the tailpipe. It should be also emphasized that renewable fuels are polluting air in a similar way. Air quality in engineering ecology is achieved and sustained by three interrelated strategies: monitoring, control and management of air pollution, specifically applied to man-made pollution. Monitoring gathers information about the object of environmental interest, according to preset goals. It involves identification of polluting sources and pollutants relevant to the object; creation of inventories; methods for quantitative estimation (measurement, emission factors and combined estimates) of the polluting emission rates; information about the mechanisms of formation of the pollutants, etc. Today, monitoring usually starts with visiting environmental cites on the Internet [eg, national, of European Union (EU), United States, etc.] to learn what other people have done. Then it continues with activities within the particular object where air quality has to be ensured e measurements and estimations of rates of pollution, preparing inventories, etc. Control has to identify specific legal and technical options for limiting or avoiding air pollution, so that air quality can be maintained. It should review the best available techniques (BATs) and select the maximum achievable control technologies (MACTs), applicable to the particular air pollution. Management combines the information gathered from monitoring and control, into action plans. These plans should select the targeted pollution sources (‘key/priority sources’) and the MACTs to be applied, define concrete goals and time frames for their achievement, costs, responsibilities of participants, etc. Air pollution management plans for polluters are mandatory in developed countries and are reported to control bodies (eg, regional inspections for environment), together with their polluting emissions declarations. At site and company level they are usually aimed not only at achieving compliance with air quality standards. Companies which pollute less than allowed can sell ‘credits’ to those that cannot fulfil the requirements.

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Air quality standards are becoming stricter. So, the three strategies described previously are also developing towards better air quality. Monitoring updates the information with new measurements, control reviews the latest pollution control technologies, while action plans ensure concrete improvements in advance of legal changes.

2.2 Estimation of the Impact of Air Pollutants Evaluation and comparison of different pollutants for their potential impact on the environment involves assessment of indicators like exposure limit values, volatility, density, potential to accumulate in the air and others. The concentrations of contaminants can be estimated by experimental measurement, by calculation with emission factors and formulae and/or by combining own experimental measurement with development of site-specific own values of emission factors (adapted constants). Experimental measurements evaluate representative samples, taken at prescribed intervals. The results are reported as instantaneous emission rates at the time of sampling and/or as cumulative values for a given period of time. The place for performing outdoor measurements, usually done for overall estimation of air quality, should be selected taking into account wind-blowing directions, terrain features, natural contribution, avoid nontypical polluting activities (eg, road repair works), etc. Measurement ‘at source’ is representative for polluting sources, but taking a sample should follow also specific rules [7]. For instance, in a chimney, sampling should be done along its central axis because emission rates are lower closer to the sides of the chimney and depend also on deposits on chimney walls. The measurement sample should not contain substances that are not typical for the pollutant stream (for instance, leaves, dead birds, insects, etc.). The principal air-sampling system has several common features and rules [7]. The sampling tube, if necessary, might be heated to avoid condensation of some of the pollutants and get an incorrect reading of their concentration. From the sampling tube the gas goes to detectors which determine the concentrations of the various pollutants. It is important to measure the volume emission rates. A gas clock is a device, which can do that. Forced gas flow with a pump is often used. Sensors for measuring the pressure and temperature are also included. They are necessary for recalculation of the concentrations into normal cubic metres (volume at a pressure of 0.1 MPa and a temperature of 0 C). The particular methods, used for measuring emissions, depend on the magnitude of the concentrations, the rates and types of the pollutants, as well as on the type of the emission. The latest techniques are described in detail in other chapters of this book. They are widely used for process emissions in the petroleum industry. Measurements of storage and handling emissions of VOCs, as well of fugitive emissions, seem to be more specific and somewhat lagging behind, as applied in the petroleum industry. The former might be still

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measured by difference of the mass of the liquid ‘before’ and ‘after’ a period of storage and/or loading into or transfer from a tank. Online monitoring of hydrocarbon concentrations in the vapour space of the tank or of the level, temperature and density of the fluid is still considered expensive and not widely used. The use of a hydrocarbon ionization detector for fugitive emissions, originally developed by US EPA and standard in Europe (EN ISO 15446), is widely accepted because it is quicker and less expensive than ‘bagging’ of the numerous sources, most of which do not leak. Optical gas imaging is also emerging as a competitive alternative. Comparison of practical applications of these methods can be found in [8]. Remote sensing is being tested also for storage tanks. Simulated application of DIAL (differential absorption LIDAR, where LIDAR is light detection and ranging) for such tanks is described in Ref. [9]. Most recent publications of US EPA and CONCAWE (CONservation of Clean Air and Water in Europe), the European Oil Company Organisation for Environment, Health and Safety [6,10,11], describe in detail the latest methods for measurement of air pollutants from sources within US and European refineries. Hereunder, some practical advantages and disadvantages of experimental measurements are noted. Practical Advantages of Experimental Measurements: l

l

l

l l

Experimental measurements are objective, and for a particular emission source, they are the most accurate way for evaluation. Experimental measures are usually standardised and have clearly defined uncertainties. Experimental measurements assess the state of the polluting source and can be used to repair it and control pollution. Without experimental measurements emission factors cannot be developed. Experimental measurements are used for prescribing sanctions and granting bonuses.

Practical Disadvantages of Experimental Measurements: l

l

l

l

Experimental measurements are expensive in terms of equipment and qualification of measurement personnel. The result of experimental measurements is valid for the particular source but usually cannot be used for similar sources, even within the same company. For instance, emissions from a storage tank depend on meteorological factors, so they would be different for sea side and higher altitude sources. Obtaining a representative sample for experimental measurements, especially ‘at source’, might be sometimes difficult or even impossible. For huge amounts of point sources (eg, fugitive emissions) measuring of all is too expensive and impractical.

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The above considerations have lead to the use of emission factors. Emission factors are average statistical coefficients obtained by processing data from compatible devices and experimental methods, used to measure the pollutants from one and the same kind of polluting activity. They are expressed in different ways depending on the activity; examples are kg/tonne of incinerated fuel; kg/MWh; % of stored and/or manipulated amount of VOCs, etc. In vehicles, typical dimensions are g/km (or mile) run, g/test cycle, etc. Aircraft emissions are usually reported in grams per cycle “takeoffelanding”. With the increasing number of experimental measurements and obtained data, emission factors are further refined and detailed for specific activities. Today the recommended values of emission factors are published on the Internet sites of environmental agencies e EPA, EEA, CONCAWE and others [5,6,10,11]. Values of emission factors are often included as coefficients in empirical formulae, derived from adequately representative amounts of experimental data. Some of the practical advantages and disadvantages of emission factors and the correlations in which they might be used are summarized hereunder. Practical Advantages of Emission Factors: l l l

l

l

Emission factors are available on the web free of charge. Emission factors allow for swift approximate estimates. For large objects (a region in a country, a country in the EU, a state in USA, etc.) emission factors provide adequate estimates. Emission factors and empirical correlations are used in the development of computer software for modelling and simulation of air pollution (eg, in ‘TANKS’, ‘MOVES’, etc. programs) and for definition of air quality specifications. Emission factors can be used in the development of own (adapted) values and correlations, valid for the given company site.

Practical Disadvantages of Emission Factors: l

l l l

The uncertainties of the emission factors are always higher than those of experimental results because they add modelling errors to experimental errors. Emission factors cannot be used for sanctioning a particular polluter. Emission factors cannot be used to repair a particular polluting object. For older and specific equipment emission factors might not be available.

Some of the aforementioned disadvantages of the experimental measurements and the emission factors on a cite level can be overcome by development of own values of the emission factors (‘adapted estimates’) from own experimental results. Such adapted estimates are most useful for the fugitive emissions, evaporating from seals of pumps, compressors, valves, flanges, etc.,

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which in a refinery might include several hundreds of thousand sources. The leak detection and repair (LDAR) protocol [12] might be used as a basis for their development.

3. IMPACT OF THE PETROLEUM INDUSTRY ON AIR QUALITY 3.1 Production of Petroleum Production of petroleum is preceded by exploration and discovery of the respective resources, which however do not involve a significant impact on air pollution, as compared to the main activities of the petroleum industry [13]. Oil is obtained from production wells, together with some amount of gaseous hydrocarbons (methane to butanes). Some production sites are situated offshore and in arctic climate zones. Largest onshore sites might cover up to 300 square kilometres of land, with a huge number of drilling rigs. The impact of petroleum and its products on air quality depends on its composition [13]. For instance, contribution to emissions of VOCs and SOx is determined by their concentration in the particular fuel. That is why, hereunder, we present briefly selected characteristics of crude oils. Crude oils are mixtures of gaseous, liquid and solid chemical compounds, nearly all of which are hydrocarbons with 1e60 carbon atoms. Typical element analysis gives 79.5e87.3% carbon; 10.4e14.8% hydrogen; 0e8% sulphur; 0e2% oxygen, 0e0.1% nitrogen and 0e0.05% metals (Fe, V, Ni, As, etc.). Nonmetals are contained in heterocompounds, while the metals are included in inorganic salts. The latter are dissolved in the water extracted in varying amounts with the crude oils. Crude oils contain thousands of organic compounds with different molecular structure and mass. The main hydrocarbon groups are n- and i-alkanes, cyclanes and arenes. Alkenes appear in the products of certain chemical transformation processes. Typically, the normal boiling temperatures of degassed crudes are between 30 and more than 500 S. Thus, significant amounts of crude oil components and their products are VOCs. Sulphur is usually in mercaptans (R-SH), hydrogen sulphide (H2S), dissolved free sulphur, thiophen ((CH)4S), sulphonic acids (RSO3H), alkyl sulphides (R-S-R) and alkyl disulphides (R-SS-R), sulphoxides (R-SO-R1), alkyl sulphates (R2SO4) and sulphones (RSO2R). In the formula, R is an organic radical. Oxygen, typical for cycloalkane crudes, is present in carboxylic acids with a cyclane radical, and less often in phenols. Nitrogen is in significant quantities in the heavier fractions of cycloalkane crudes within alkylquinolines, pyridines, pyrroles, indoles and carbazoles. The main polluting activities in petroleum production, apart from extraction, include dewatering/desalting; storage of huge amounts of oil, gas and water, containing VOCs; manipulation (transferring from one vessel to another); and

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loading at transportation terminals. Combustion by flaring (burning some amount of gas for safety reasons) and in mobile (vehicles) and stationary installations (eg, for electricity generation) is also performed. Depending on particular cite conditions and oil properties, relatively small amounts of oil can be extracted without some enhanced oil recovery technology. Secondary oil recovery is practiced to increase oil yield, after the pressure in the well falls down. It is done by flooding with water, containing salt and surface active substances, and/or by injection of some amounts of the produced hydrocarbon gas back into the well. Tertiary oil recovery with air or inert gas injection (eg, CO2) becomes increasingly popular. Heated gas purging for lowering density and viscosity is typical in cold zones. In this case, steam, cogenerated by some of the produced gas, along with electricity, is preferred. Microbial degradation of hydrocarbon chains within the well, and thus lowering viscosity is a cheaper but still new alternative. Depending on oil type and conditions in the well, including rocks’ permeability, tertiary recovery would increase crude oil yield with 5e15%. More oil can be obtained by fracturing and horizontal drilling technologies, similar to those developed for shale gas. They can be applied to conventional or nonconventional resources, eventually leading to greater environmental pollution. The obtained crude oils, known as ‘tight oils’, are mixed and processed together with conventional crudes. It has been suggested recently that fracturing with CO2 and N2 might be more effective than the traditional hydraulic fracturing with water, sand and surfactants. The world production of petroleum in 2014 reached 4220.6 million tonnes, up from 3904.7 million tonnes in 2004 [4], which is an increase of 8.09%. It is important to note, that Europe and Eurasia produced around 834 million tonnes, out of which around 670 million tonnes were extracted in former Soviet Union countries. For the same year Ref. [4] estimates, that Europe imported 446.9 million tonnes of crude oil. Table 1 summarises the main activities at a petroleum production cite and their impact on air quality.

3.2 Transportation of Petroleum The main transportation of petroleum is realised with pipelines and tankers. Tankers are around one-fifth of the total world merchant tonnage of marine transport, vessels with up to 300,000-tonne capacity or more being in use. Pipelines can provide the link between the oil field and the refinery or the sealoading terminal. The crude oil pipelines may be several thousands of kilometres long, crossing different countries, mountains and even the oceans. Intermediate pumping stations powered by gas turbines stations provide the flow uphill. The BakueTbilisieCeyhan pipeline, for instance, spans 1760 km of rugged terrain, with 1500 river crossings along the way [14]. The total length of crude oil transportation pipelines of the United States in 2013 is estimated at around 1,430,000 km [15]. Russia is in second place with

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TABLE 1 Impact of Main Petroleum Production Activities on Air Quality No.

Process/Activity

Main Air-Polluting Emission Streams

1

Crude oil production

Process (combustion) from drill rigs’ and vehicle engines; as well as from flares; fugitive from seals (tubings) of drill pipes.

2

Dewatering and desalting

Storage and manipulation from crude storage tanks and electro dehydrators, if used; fugitive from pump, valve compressor, etc. seals; Secondary from depleted water and sludges.

3

Gas separation (stabilisation)

Fugitive from flash drums, valves; typical emissions from distillation columns, if used.

4

Enhanced oil recovery

Depends on applied technology. In general, process and fugitive emissions are increased.

5

Loading at terminals

Storage and handling from storage and transportation tanks; fugitive from pump, etc. seals; secondary from ballast water (tankers).

around 81,000 km and Canada is third with around 20,000 km. Fig. 1 shows the major movements of crude oil streams worldwide in 2014 [4] (without petroleum products and petrochemicals). According to the same reference, these streams total 2788 million tonnes, around 15% more than in 2004 and around 66% of the crude, produced in 2014. It should be noted that pipelines can be running under water, under and/or above ground and contain hundreds of thousands of seals (flanges, valves, etc.) that can emit air pollutants. Mobile pollution sources, rail or road transport and waterway barges, are used for inland commercial exchanges of crude oil. They also have storage tanks and seals. Taking into account the significant amount of crude oil imported in Europe, discussed previously, we can conclude that pollution from transportation of petroleum is a more serious problem for it, rather than production.

3.3 Refining of Petroleum The throughput of small petroleum refineries is typically from 1.8 to 9.0 million tonnes per year, for a small refinery, to 18.0 to 62.0 million tonnes per year, for a large one. In 2014, the refinery processing capacity of the world was 4,806,397.2 thousand tonnes per year, 18.4% of which was in the United States and 14.7% in the EU [4]. The refinery throughputs (amounts of yearly refined crude oil) of the world in the same year were 3,826,283.4 thousand tonnes, 20.6% of these realised in the United States and 14.5% in the EU.

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FIGURE 1 Major trade movements of oil in 2014. Trade flows worldwide (million tonnes) [4].

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3.3.1 Overview Refineries differ in complexity (ie, in processes, technologies and depth of conversion available), which is often estimated by the so-called ‘Nelson Complexity Index (NCI)’, originally developed by W.L. Nelson [16,17]. The NCI assigns a complexity factor to major refinery process units, based on their complexity and cost in comparison to atmospheric crude distillation, assigned an NCI factor of 1.0. The complexity of each piece of refinery equipment is then calculated by multiplying its NCI by its throughput ratio as a percentage of atmospheric crude distillation capacity. The sum of the complexity values assigned to each piece of equipment summarises the technological complexity of a refinery and its economic potential. Higher NCI number indicates a greater cost of the refinery and higher added value of its products. In general, it correlates also with greater pollution and capability to process heavier and/or more sulphurous crudes. Fig. 2 presents a simplified scheme of a modern petroleum refinery without production of petrochemicals [18]. In 2014 the world petroleum processing industry produced around 4.26 billion tonnes of refined petroleum products, 22.06% of which were manufactured in the United States, 14.4% in Western Europe and 31.4% in Asia and the Pacific region [19]. An energy equivalent to the energy value of 3e8% of the processed crude oil is burned in-house. The exact amount for a particular refinery depends mainly on the assortment of products being produced but also on energy efficiency. One of the most advanced refining industries, that of the United States in 2002, used 3.1 quadrillion BTUs of energy [20] (conversion factor: BTU ¼ 1.054 kJ). Petroleum processing uses also huge amounts of water. The average amount of water used in US refineries is estimated to average 1.5e2.5 m3 per one cubic metre of crude oil processed. Polluted water is treated inside the refinery and most of it is recycled [20]. It should be noted that obtaining and moving water consumes energy and polluted refinery streams are often sources of secondary emissions of VOCs. 3.3.2 Petroleum Processing Operations The refining of crude oil and its fractions employs a wide variety of processes, determined by the composition of the processed crudes, and existing markets for the products, which can be produced. The refinery flow scheme in Fig. 2 shows a general processing arrangement used by modern refineries in the United States. The typical refinery processes and associated operations are classified somewhat differently by EEA and EPA. EEA [21] defines four groups of general refinery processes: separation processes, petroleum conversion processes; petroleum treating processes and blending, with SNAP codes 040101 and 040102 for ‘Petroleum Products Processing’ and ‘Fluid Catalytic Cracking’, respectively. Refinery principal

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FIGURE 2 A principal scheme of a US refinery [18].

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products might include three product types: liquid fuels: from motor and aviation gasoline, through aviation kerosene and diesel fuels, to heating fuel and residual oil; by-product fuels and feed stocks: naphtha, lubricants, LPGs, asphalt, etc.; and primary petrochemicals: ethene, propene, butadiene, BTX (benzene, toluene and xylenes). Production of the latter group is not included in Ref. [21], but in subsector 040500 (Chapters B451and B452). The particular SNAP codes associated with petroleum processes can be found in Ref. [22]. They include additional groups of processes in addition to the aforementioned processes, namely, feedstock handling and storage, product storage and handling, auxiliary processes. The latter identify combustion and flares, incineration of wastes, sulphur plants, etc. The ‘Organic chemical production’ group is also included, although this is a large group and some of its chemicals are not produced in petrochemical plants. EPA [18] lists five groups of general refinery processes and associated operations. The first three groups have the same titles and contain the same processes as in EU [21]. The fourth EEA group ‘Blending’, EPA includes in ‘Feedstock and product handling’, together with loading/unloading and storage activities, which is different as compared to Ref. [22]. The fifth EPA group ‘Auxiliary facilities’ is also different. It does not include combustion and organic chemical production facilities but has ‘Hydrogen production’, which is a key facility for the ever increasing hydrogen needs in modern refineries. For detailed description of the aforementioned processes and installations, pollutants and sources, emission factors, etc. the reader is referred to the original publications [18,21,22] and the links provided there in. Hereunder, we provide a concise compilation of the aforementioned groups complemented by some processes, which we consider relevant [13], SNAP codes and complexity indices, when available. The emission factors in SNAPs allow for estimation of the installed pollution control technologies and thus for evaluation of a refinery’s pollution prevention potential in addition to its NCI economic value. Examples of physical activities, used in refining, are presented in Table 2. Assignment of SNAP codes for polluting activities, as Table 2 shows, depends on the chosen definitions of the respective installations. Distillations (atmospheric, vacuum, at elevated pressure, with or without preheated water vapour, azeotropic, extractive, with chemical reaction, etc.) are used in many installations for separation of gases from liquids but also after conversion processes (eg, debutanization after fluid catalytic cracking). It also separates solvents from extraction processes (No. 5, 6 in Table 3). Some of the distillations use preheated steam. The condensed water joins water from desalting, vacuum-creating barometric condensers, etc., becoming a source of secondary emissions in water treatment (SNAP code 091001 for auxiliary facilities). Similarly, operations with process heaters (marked in Fig. 2) produce combustion emissions throughout the refinery (SNAP codes 030104 and 030105 for auxiliary facilities). Thus the discussed classifications are not related to activity locations on site. This might be beneficial for the concept of fence-line

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TABLE 2 Physical Process Activities: Separation, Blending, Handling, etc. No.

Process/Activity

SNAP Code [22]

NCI [17]

1

Atmospheric distillations

040101

1.0

2

Vacuum distillations

040101

1.3

3

Light ends recovery (Gas processing)

040101

e

4

Blending

040101

e

5

Feed stock handling and storage

050401/050402

e

6

Product storage and handling

040104

e

7

Solvent extractions

040101

e

8

Solvent dewaxing

040101

e

9

Adsorption refining

040101

e

SNAP, Selected Nomenclature for Air Pollution; NCI, Nelson Complexity Index.

TABLE 3 Petroleum Conversion Processes No.

Process/Activity

SNAP Code [22]

NCI [17]

1

Thermal cracking/visbreaking

040101

2.75

2

Thermal cracking/coking

040101

7.5

3

Fluid catalytic cracking

040102

6

4

Catalytic hydrocracking

040101

8

5

Catalytic reforming

040101

5

6

Alkylation/polymerisation

040101

10

7

Aromatics

0405

20

8

Isomerisation

0405/040101

3

9

Catalytic hydrorefining and desuphurization

040101

2.5

10

Oxygenates (ethers e MTBE/TAME)

0405

10

11

Lubricants

e

60

12

Asphalt blowing

060310

1.5

13

Other organic chemical production processes

0405

e

14

Sulphur recovery plants

040103

240

SNAP, Selected Nomenclature for Air Pollution; NCI, Nelson Complexity Index.

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monitoring of toxics from refineries, being introduced by EPA [23], but from the point of view of pollution control technologies it is most efficient if they are chosen and applied ‘at source’. Table 3 presents examples of petroleum processes with chemical conversion. Table 3 gives examples of the numerous processes with chemical conversion used in refineries. The ‘Lubricants’ group involves a specific combination of activities with high complexity, some of which are not identified in Table 3, for instance, hydroizomerisation of waxes and catalytic dewaxing. Petrochemical production processes, listed under No. 13 in Table 3, might involve production of phenol and acetone; alkylene oxides (ethane, propene oxides, etc.) and derivative nonionogenic surfactants (eg, glycols); halogen compounds (eg, chlorinated benzene); nitrogen compounds (eg, amines and ethanol amines), etc. Many of the intermediates and products can be classified as toxic or hazardous pollutants, which might be also VOCs. This holds also for the arenes and some of the other nonmethane hydrocarbons, emitted in refineries. Polymerization might produce high octane components for gasoline but also high-molecular-mass synthetic polymers and elastomers. Methane is a greenhouse gas. Asphalt blowing with air produces carcinogenic oxygenated acids. Table 4 gives examples of petroleum treating processes. EEA and EPA include in this category deasphalting, which here is included in Table 2 with other extraction separation processes. Hydrotreating and hydrodesulphurization chemically convert heterocompounds into hydrocarbons and saturate unsaturated bonds. They are presented in Table 3 for convenience because they have SNAP codes and complexity indices. Table 4 gives examples of processes in which the undesirable compounds after chemical conversion are removed from the product. Acid refining is obsolete, but the other processes are widely used. They do not have SNAP codes and/or indices so instead, Table 4 presents their main emissions. Acid refining treats petroleum fractions or used oils typically with concentrated sulphuric acid or oleum. Typical examples are the refining of gasoil-derived straight-chain paraffins (n-alkanes) from arenes and the

TABLE 4 Examples of Petroleum Treating Processes No.

Process/Activity

Main Emissions

1

Acid refining, eg, for waste lubricant regeneration

Process, secondary

2

Acid gas removal

Process, fugitive

3

Chemical sweetening

Process, secondary

4

Desalting

Secondary

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obsolete regeneration of used lubricating oils, from which acid sludges are depleted. Process emissions come from the acid reagent, and secondary emissions - from the acid sludges which emit SO2. Acid gas removal (Fig. 2) treats light ends or gases, for instance with amines, which form complexes with H2S, thermally decomposed in a next stage. The liberated H2S goes to sulphur recovery, and the purified gases or light naphtha is utilized as shown in Fig. 2. Chemical sweetening oxidises mercaptans to alkyl disulphides in the presence of a catalyst and caustics. The disulphides may be extracted and removed. Process emissions are the major problem, which comes from the involved air blowing treatment. The treated hydrocarbon fractions are VOCs, which might be emitted as process and/or fugitive streams. Desalting removes water, salts, grits, etc. from the crude oil in horizontal elecrodehydrators, in the presence of surfactants. Secondary emissions from the water streams are the main effluents. Table 5 presents auxiliary facilities, without those included in previous tables.

TABLE 5 Auxiliary Facilities SNAP Code [22]

No

Auxiliary Facility

1

Combustion

030104, 030105

Process

2

Process furnaces

030106

Process (combustion)

3

Waste water treatment

090001, 090002

Secondary

4

Incinerators of wastes and sludges

090202, 090205

Process (combustion)

5

Flares

090203

Combustion

6

Landfills

090400

Secondary

7

Cooling towers

e

Fugitive, secondary

8

Vapour recovery

e

Storage and handling, fugitive

9

Blowdown systems

10

Steam purging in maintenance operations

e

Secondary, fugitive

11

Hydrogen production

e

Process

SNAP, Selected Nomenclature for Air Pollution.

Main Emissions

Combustion

580 SECTION j III Real Scenarios

Combustion in Table 5 is related to several facilities. No. 1 is combustion in boilers of different power, used mainly to generate steam. Process furnaces heat up crude oil and feed stocks to the required high temperatures for distillation or chemical conversion operations. Emissions from both sources contain all criteria pollutants in proportions depending on the used fuels, typically refinery gases and/or fuel residues. Incinerators of wastes and sludges might contain permanent organic pollutants, depending on the composition of the waste. Blow-down systems collect and separate the gases and liquids from planned or unplanned discharges. Liquids are recycled, while gases might be recycled or burned out in flares. Combustion emissions from flares are usually smokeless but in the case of unplanned discharges might have additional pollutants. Other sources of typical combustion emissions, not shown in Table 5, are the vehicle and stationary engines, process compressors, turbines, etc. employed at the refinery site. The emission of VOCs from waste water treatment and landfills can be classified as secondary, although fugitive emissions might be also emitted. Cooling towers are used to cool down water for reuse. Vapour recovery systems collect mainly VOCs from different sources (tanks, water treatment, etc.), thus controlling their release. Steam purging is typically used to clean up vessels, which have to be repaired during maintenance shutdowns. The condensed water contains an assortment of hydrocarbons and possibly other compounds, depending on the material being cleaned out. VOCs from these operations appear usually as secondary and fugitive emissions in water treatment facilities; heavier compounds are transformed there into sludges.

3.4 Transportation and Marketing of Petroleum Products In 2014 the world produced [4] close to 4.89 billion tonnes of crude oil distillates, 32.7% of which were light (aviation and motor gasolines, light distillate feed stocks); 36.8% middle distillates (jet fuel, heating kerosines, gasoil feed stocks); 8.7% fuel oils (heavier marine bunker fuels, according to the US specification) and 18.6% others (refinery gas, LPG, solvents, coke, lubricants, bitumen, wax, other refined products, refinery fuels and losses). We might reasonably assume that approximately these amounts of distillates and finished products (ie, doped with additives) were transported from refineries to final customers. Significant portions (eg, automotive diesel) or the entire quantities of these (eg, gasolines) have normal boiling temperatures less than 260 C and are nonmethane VOCs (NMVOCs). Petrochemicals are not included in these estimations. Some are VOCs, but compounds containing heteroatoms are much more reactive and dangerous pollutants than NMVOCs. Among the fuels, gasoline transportation and marketing is the greater contributor to emissions of VOCs. The organization of the gasoline distribution system is illustrated on Fig. 3, providing also the respective SNAP codes [24].

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FIGURE 3 The gasoline distribution system [24].

Transportation and marketing of the rest of the petroleum products follow a similar scheme. Their place in the whole petroleum industry chain is described in greater detail, together with the relevant pollution control technologies, in [25]. From the point of view of the overall impact of the petroleum industry, transportation and marketing of petroleum can be characterized with two main features. Bulk consumers of petrochemicals and distillates are either industrial sites, which use them as feed stocks, or large storage depots for state and military reserves, etc. In the latter case, significant amounts of finished products are also transported, stored and distributed. In general, such consumers usually have adequate experience, funds, equipment, personnel, etc. to provide air pollution monitoring, control and management, similar to those in refineries. Small and individual consumers transport, store and use finished fuels and lubricants, which go not only into their automobiles, as in Fig. 3, but also into other vehicles, off-road applications in engines and small combustion plants for agricultural, building and construction, military, etc. field activities. In the described commercial chain, the large pollution sources transform into smaller and of increasing numbers point sources, while the necessary knowledge and means for monitoring, control and management of air pollution become less available. The emissions from transportation and marketing can be classified as storage and handling, fugitive and secondary. US EPA [25] lists their sources as (1) rail tank cars, tank trucks and marine vessels; loading, transit and ballasting losses; (2) service stations: bulk fuel drop losses and underground tank breathing losses; (3) motor vehicle tanks: refuelling losses; (4) large storage tanks: breathing, working and standing storage losses. Description, emission factors and control technologies for group 4, including organic liquids storage, are provided in Ref. [26]. Evaporative and exhaust emissions from transportation in AP42 have been the object of Ref. [27], which after 2013 is no longer maintained. The European Environment Agency (EEA) also describes emissions from mobile sources with several SNAP codes. Storage and handling emissions are released [13,25], when a tank is ‘breathing’, as the result of differences of pressure, temperature and VOCs’

582 SECTION j III Real Scenarios

concentrations in the gas phase of the tank and in the air out of the tank. Loading and unloading has a similar effect, which is observed also as motor vehicle refuelling losses. During transportation the uncontrolled movement of the liquid phase within the tank changes pressure on the gas phase and stimulates opening and closing of tank valves. Fugitive emissions come from the same sources (valves, flanges, seals, etc.) as in the other branches of the petroleum industry. They are only of NMVOCs, released at normal and/or increased pressure (from pipelines). Secondary emissions of VOCs evaporate from drained water and scrubbed sludge, obtained during maintenance operations on tanks, and especially from ballast water kept in the tanks of barges and tankers, emptied of cargo. Evaporative emissions from vehicle fuel systems are typical for gasoline, released from a hot engine. Combustion emissions of vehicle exhausts contain the criteria pollutants and specific pollutants, the proportion, composition and chemical structure of which depend on the used fuel.

4. CONTROL AND MANAGEMENT OF AIR POLLUTION IN THE PETROLEUM INDUSTRY Monitoring, as discussed previously, provides inventories of data for the estimation of the impact of all sources of air-polluting emissions and imissions, within a relevant object of assessment. The compilation of inventories starts at company cite level and goes up to higher levels e region, state, continent, global, etc. According to the used method in the EU [28,29], the primary data can be classified as measured (M); calculated (C) from activities, emission factors or mass balances; and estimated (E) by nonstandardised methods, best assumptions, etc. They are collected in the European Pollutant Release and Transfer Register. For SOx, released in EU in 2011, for instance, 52% of the reported data are M, 45% C and 3% E [28]. The respective environment agencies develop, organize and publish all methods for obtaining compatible information. They classify and describe activities, give emission factors, recommend BATs, etc. We have already presented relevant EEA and EPA documents and publications from CONCAWE, which are a valuable source for the petroleum industry. Hereunder, we shall summarise some of the recommended technologies, assigning them to sources and classifying the emissions, as described previously. More detailed information can be obtained from the original publications, as well as in Ref. [30]. A general approach for controlling pollution from any industry is the limitation of the use of energy, water and steam. In the petroleum industry energy is obtained by combustion, water has to be from own supplies, and preheated steam is widely used.

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4.1 Storage and Handling Emissions Larger quantities of volatile organic liquids are stored in above ground tanks, while underground tanks are typical for gasoline stations. Military bases may also employ underground storage. There are four types of tanks, used for above ground storage of liquids: fixed roof, with internal floating roof, with external floating roof and with domed external floating roof [26]. In the EU before 1994, liquids, consisting entirely of VOCs (eg, gasoline) could be stored in fixed-roof tanks, which have significantly higher emissions. Their control has been achieved by selecting and maintaining the tank colour, valves, regulating gas space, etc. After 1994 (EU Directive 94/63/EC) fixedroof tanks for gasoline must either be equipped with an internal floating roof, be vapour balanced or be connected to a vapour recovery unit. These technologies are applicable to handling and storage of similar liquids and usually applied together in modern storage depots. Internal floating roofs follow the liquid level. Their seals decrease the amount of liquid above the roof, the vapours of which are sent to recovery units, for instance, buffer tanks, which collect and release vapours, depending on the pressure above the float. Vapour balance, combined with submerged filling pipes, returns the vapours into the vessel from which the tank is filled in. It is used also at gasoline stations. For filling of automobiles the pump of the station sends the vapours from the car reservoir into the underground storage tank. The described technologies can be applied to all relevant sources within the petroleum industry. Options for creating action plans for managing of storage and handling emissions from a fixed-roof tank when the EU Directive had been implemented could be estimated by the program ‘TANKS’, developed by the US EPA [31]. Around that time we have used TANKs to simulate the effect of pollution control, as applied to an existing gasoline tank with 0.67% yearly emissions. As a first step, the main input variables (fluid properties, tank parameters and condition, meteorological factors, etc.) of the program had been changed until the predicted emissions coincided, within acceptable limits of uncertainties, with the measured ones. Then calculations have been performed, applying consecutively different control options e changing paint, adjusting valves and liquid level, introducing a vapour recovery system, introducing an internal floating roof with different seals, etc. A combination of these, which predicted that the desired new yearly limit of emissions (<0.01%) could be achieved, had been selected. Predicted results could be validated by physically applying the selected combination of control technologies to the selected tank. The obtained information could be used to develop action plans in terms of required costs, time, etc. for implementation of the selected technologies to all suitable tanks at the storage site.

584 SECTION j III Real Scenarios

4.2 Fugitive Emissions The main sources of fugitive emissions in a refinery are the valves, which combine a huge number with a high emission factor [25]. Control is achieved by closing leak and spill points, change of seals, modification (eg, closed-vent system) and replacement of leaking equipment. The LDAR protocol [12] is widely used for management of these emissions.

4.3 Process Emissions Process emissions from refineries depend on the type of process being realised. In Fig. 2 the significant air polluters are given in bold. Tables 2e5 provide additional details. The most important information sources, which describe also pollution control, have been given in the text. Catalytic cracking pollutes air with flue gases from catalyst regeneration and with conventional combustion emissions (high temperatures are employed). The former contain particulates, hydrocarbons, SO2, CO and CO2, NOx, aldehydes, ammonia, cyanides and other less significant pollutants [25]. Particulates contain worn catalysts, metals and residuals from promoters, in addition to carbon [11]. They are controlled conventionally, with cyclones, precipitators, scrubbers, etc. Supplying oxygen to the regenerator, beneficial to control of oxidisable pollutants and yields, is an option, when the sulphur in the feed is low. Cyanides go to scrubbing water, where they can be transformed. Conventional combustion emissions depend on the used fuel. They are released from all refinery heaters and vehicles and can be controlled with all available industrial technologies. In flue gases hydrogen, left from other applications, might be beneficial. Waste incinerators might produce persistent organic pollutants. In this case, plasma combustion is required [30]. Gases from catalyst regeneration in catalytic reforming might contain small amounts of chlorine and persistent organic pollutants. Process emissions from production of petrochemicals require specific control technologies. Cushions with inert gases, instead of blowing through, benign solvents and alternative syntheses, when possible, present the more general approaches.

4.4 Secondary Emissions The sources of these emissions have been already discussed. They consist predominately of CH4 and NMVOCs. Typically, those are collected by closedvent systems, applied also in waste water treatment facilities. In the blowdown systems, liquids are condensed and recycled. The rest are burnt in flares. Using less water and steam, especially in maintenance operations, is an important control option. For vacuum distillation units controlling steam, replacing ejectors with pumps and water condensers with air condensers is efficient.

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Air pollution management on a company level selects key sources. Action plans for them are drafted at lower levels and then fitted in the general strategy of the company. It is also important to note that good practice should manage in synergy air, water and soil pollution.

5. PERSPECTIVES AND CONCLUDING REMARKS The petroleum industry in its entirety might be a huge source of air pollution, especially if the use of its products is also accounted for. However, it is always in the public eye and closely monitored by environment agencies. It adequately uses and develops latest pollution control technologies, with efficiency in many cases above 90% [18,25]. Systemic pollution management of the industry can provide additional advantages. Modern vehicles have also adopted powerful emission control technologies e reduced consumption and more environmentally compatible fuels, afterburning treatment, on-board diagnostics, zero-emission electric and super-ultralow-emission hybrid vehicles, etc. [30]. The same holds for cogeneration of energy with fossil fuels. At the end of this chapter, we might conclude that the main impact of the petroleum industry on pollution comes from the multiplication of huge amounts of materials by relatively well-controlled and small amounts of pollutants. Global renewable energy, including hydroelectricity, consumed in 2014 was 1213.9 Mtoe, around 9.4% of the total energy consumption [4]. Global production of renewable fuels was 70.8 Mtoe. Comparison with previously given data, calls for more renewable energy and fuels, produced competitively and with less pollution. Changing from extensive to intensive energy use and smart technologies with high efficiency; CO2 capture; total utilization of waste biomass and municipality wastes; increasing yields from industrial crops; biorefineries and co-processing, etc. are vital keys to sustainable development. Improvement of combustion energy systems is limited by availability of biomass, conversion coefficients, carbon foot prints, volatility, etc. Their gradual replacement with electrolytic energy systems (fuel cells) is the expected breakthrough. Competitive, ecocompatible and safe production, storage and distribution of hydrogen are key problems [30]. Optimistic scenarios predict 100% renewable energy by 2050 [32]. Whether this could and would be achieved depends on transparency, sound life cycle analyses and impartial judgement of all alternatives, some of which, unfortunately, might still be exposed to speculation and corruption.

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586 SECTION j III Real Scenarios [3] AP-42, Chapter 5.2. Transportation and Marketing of Petroleum Liquids, Document C05S02, EPA, U.S., 1995. http://www.epa.gov/air. [4] BP Statistical Review of World Energy, BP p.l.c., 2015. Downloaded from: www.bp.com/ statisticalreview. [5] EMEP/EEA air pollutant emission inventory guidebook, EEA Technical Report, 2013. No 12/2013. [6] Review of Emissions Test Reports for Emissions Factors Development for Flares and Certain Refinery Operations, Office of Air Quality Planning and Standards, Sector Policies and Programs Division, EPA, U.S., 2015. http://www3.epa.gov/ttn/chief/consentdecree/ final_report_ef.pdf. [7] N. DeNevers, Air Pollution Control Engineering, 2nd reissue ed., Waveland Pr Inc., 2010. [8] Abating Fugitive VOC Emissions More Efficiently, CONCAWE Reviews, Concawe, Brussels, 2015 vol. 24, 1. [9] Towards the Establishment of a Protocol for the Quantification of VOC Diffuse Emissions Using Open-path Remote Monitoring Techniques: DIAL Monitoring of a VOC Source of Known Emission Flux, CONCAWE NPL Report Np. 12, Concawe, Brussels, 2014. [10] Emissions Estimation Protocol for Petroleum Refineries, EPA, U.S., 2015. http://www3.epa. gov/ttnchie1/efpac/protocol/. [11] Air Pollutant Emission Estimation Methods for E-PRTR Reporting by Refineries, CONCAWE Report No. 3, Concawe, Brussels, 2015. [12] Protocol for Equipment Leak Emission Estimates, EPA-453/R-95e017, EPA, U.S., 1995. [13] G. St. Cholakov, Control of pollution in the petroleum industry, in: B. Nath, G. St. Cholakov (Eds.), Pollution Control Technologies, vol. 3, Eolss Publishers, Oxford, UK, 2009, pp. 86e107. [14] http://www.bp.com/en/global/corporate/about-bp/what-we-do/moving-oil-and-gas/pipelines. html. [15] https://en.wikipedia.org/wiki/List_of_countries_by_total_length_of_pipelines. [16] https://en.wikipedia.org/wiki/Nelson_complexity_index. [17] www.ogj.com/ogj-survey-downloads.html. [18] AP-42, Stationary Sources. Chapter 5.1. Petroleum Refining fifth ed., vol. I, EPA, U.S., 2015. Downloaded from: http://www3.epa.gov/ttnchie1/ap42/ch05/final/c05s01.pdf. [19] OPEC Annual Statistical Bulletin, 2015. https://www.opec.org/opec_web/static_files_ project/media/downloads/publications/ASB2014.pdf. [20] http://www3.epa.gov/region9/waterinfrastructure/oilrefineries.html#energy. [21] Processes in petroleum industries, Emission Inventory Guidebook, B411, pr040101. Activities 040101 & 040102, EEA, 2006. [22] Processes in petroleum industries, Emission Inventory Guidebook. B410, pr040101. Activities 040101 & 040102, EEA, 2006. [23] EPA imposes fence-line monitoring on US refiners, Hydrocarbon Processing, 09.29.2015, in: http://www.hydrocarbonprocessing.com/Article/3492867/Latest-News/EPA-imposes-fenceline-monitoring-on-US-refiners.html. [24] Gasoline distribution, Emission Inventory Guidebook, B551e2, ed050501. Activities 050501-050503, EEA, 2006. Downloaded from: http://www.eea.europa.eu/. [25] AP 42, Stationary Sources. Chapter 5.2. Transportation and Marketing of Petroleum Liquids, fifth ed., vol. I, EPA, U.S, 2008. [26] AP 42, Stationary Sources, Chapter 7. Liquid Storage Tanks, fifth ed., vol. I, EPA, U.S, 2006. [27] AP 42, Mobile Sources, fifth ed., vol. II, EPA, U.S, 2006.

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