ANALYSIS OF THE TECHNOGENIC LOAD ON THE ENVIRONMENT DURING FORCED VENTILATION OF TANKS

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бИОИНДИКАЦИОННЫЕ ИССЛЕДОВАНИЯ СОСТОЯНИЯ придорожных ЭКОСИСТЕМ

Проведено исследование состояния придорожных экосистем вдоль автомагистралей Украины различных категорий. Исследовались участки на дорогах М02, М03, Н07, Н12 и Р44.

Оценка воздействия на экосистемы осуществлялась биоиндикационными методами, с помощью лишайников и высших растений (овес). Показано, что уровень загрязнения придорожных экосистем тем больше, чем выше категория дороги, а соответственно интенсивность движения автотранспорта.

Plyatsuk Leonid, Doctor of Technical Sciences, Professor, Department of Applied Ecology, Sumy State University, Ukraine, e-mail: l.plyacuk@ecolog.sumdu.edu.ua, ORCID: https://orcid.org/0000-0003-0095-5846

Moiseev Viktor, PhD, Professor, Department of Chemical Technology and Industrial Ecology, National Technical University «Kharkiv Polytechnic Institute», Ukraine, e-mail: kafedrahtpe@i.ua, ORCID: https://orcid.org/0000-0002-3217-1467

Vaskin Roman, PhD, Lecturer, Department of Applied Ecology, Sumy State University, Ukraine, e-mail: r.vaskin@pk.sumdu.edu.ua, ORCID: https://orcid.org/0000-0003-4382-0327

Ablieieva Iryna, PhD, Assistant, Department of Applied Ecology, Sumy State University, Ukraine, e-mail: i.ableyeva@ecolog.sumdu.edu.ua, ORCID: https://orcid.org/0000-0002-2333-0024

Vaskina Iryna, Assistant, Department of Applied Ecology, Sumy State University, Ukraine, e-mail: irulik.vaskina@gmail.com, ORCID: https://orcid.org/0000-0001-5904-9640

UDC ББ.083.2:ББ-971:Б14.849 DOI: 10.15587/2312-8372.2018.124341

ANALYSIS OF THE TECHN0GENIC LOAD ON THE ENVIRONMENT DURING FORCED VENTILATION OF TANKS

Дослгджено вплив свтлих нафтопродуктгв (бензин, дизельне паливо, гас) на стан навколишнього середовища в зонг впливу резервуаргв збериання цих продуктгв. Обгрунтовано, що застосуван-ня примусовог вентилящ з традицшною подачею повтря е екологгчно небезпечною операцгею. Доведено, що альтернативою цьому ршенню е ежекторний-вихровий метод подачг повтря при дегазацп резервуаргв з подальшим уловлюванням паргв нафтопродуктгв за допомогою абсорб-цшног-конденсацшног установки.

Клпчов1 слова: примусова вентиляцгя, ежекторний спосгб подачг повтря, екологгчна небезпека, резервуари збериання нафтопродуктгв, оцтка ризику.

Khalmuradov В., Harbuz S., Ablieieva I.

Storage tanks for oil products are environmentally hazardous sources of anthropogenic impact on the environment, acting as objects of uncontrolled emissions of steam-air mixtures or vapor-gas-air mixtures and spills of oil products, followed by fires and explosions. The environmental relevance of storage is essentially dependent on its potential to pollute the environment and on the physical and chemical properties of the stored substances. Petroleum tanks are used on the farm to store gasoline and diesel fuel. Properly designed petroleum storages must

prevent leaks and the potential contamination of soils, surface water or groundwater. The analysis of the sources of environmental impact during the operation of the reservoirs indicates that the vertical steel tanks, even during normal operation, are environmentally hazardous.

Preparation of tanks with residues of petroleum products for fire repair works is one of the most complex and environmentally hazardous technological operations in the process of exploitation of tanks. Fires and explosions on reservoirs from flammable substances and flammable liquids often occur during cleaning and preparation for repairs, and in the course of repair work directly [1]. The share

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of fires in the industrial sector during routine, repair and fire work is 13 % of the total number of fires. At the same time, at enterprises of the oil and gas complex, the share of fires in repair and fireworks reaches 50 %, and on reservoirs - 70 %. It is explained by the fact that light oil products are highly flammable due to availability to be easily ignited by heat, sparks or flames. Vapors may form explosive mixtures with air and may travel to source of ignition and flash back. Most vapors are heavier than air and will spread along ground and collect in low or confined areas (sewers, basements, tanks). Vapor explosion hazard indoors, outdoors or in sewers. Those substances designated with a (P) may polymerize explosively when heated or involved in a fire. Run off to sewer may create fire or explosion hazard.

Health hazard assessment of the petroleum vapors of the tanks indicates the following. Inhalation or contact with material may irritate or burn skin and eyes. Fire may produce irritating, corrosive and/or toxic gases. Vapors may cause dizziness or suffocation. Run off from fire control or dilution water may cause pollution [2].

Saturated aliphatic hydrocarbons, such as isooctane, may be incompatible with strong oxidizing agents like nitric acid. Charring of the hydrocarbon may occur followed by ignition of unreacted hydrocarbon and other nearby combustibles. In other settings, aliphatic saturated hydrocarbons are mostly unreactive. They are not affected by aqueous solutions of acids, alkalis, most oxidizing agents, and most reducing agents [3].

Regular operation, pre-repair and repair work on tanks with oil products is a source of anthropogenic impact on the environment due to the emergence of environmentally hazardous situations, accompanied by explosions and fires, and pose a real threat to life and health of the population. That&s why research and assessment of the reduction in the load on nature when introducing forced ventilation of tanks by means of ejector-vortex air supply with subsequent utilization of the injected petroleum products is a very topical scientific and practical task of improving the ecological safety of the territories.

a two-layer primer is used, along which enamel is applied. The thermal insulation is made on the wall and on the roof of the tank. During the technological audit of the object of research it was discovered that it is equipped with additional tank equipment, including level control devices, breathing fittings, fire safety devices, lightning protection device.

Main technical characteristics of the vertical steel tank 5000 m3 is shown in Table 1.

The design of the tank with the technical characteristics given in Table 1 is shown in Fig. 1.

Technical characteristics ef VST 5000 m3

Indicator name Value

Nominal volume, m3 5000

Internal diameter of the wall, m 20.92

Wall height, m 14.90

Density of the product, kg/m3 900

Estimated height of filling, m 14.90

Wall of VST-5000

Number of belts, pieces 10

Thickness of upper belt, mm 6

Thickness of the lower belt, mm 12

Bottom of VST-5000

Number of edges, pieces 12

Thickness of the central part, mm 5

Thickness of edges, mm 10

Roof of VST-5000

Number of beams, pieces 32

Weight of constructions, kg

Wall 64420

Bottom 17732

Roof 26201

Stairs 1480

Platforms on the roof 3051

Hatches and nozzles 2182

The object of research is an above-ground vertical steel tank, used as storage tank for light oil products (gasoline, diesel fuel, kerosene). The vertical steel tank (VST) consists of a cylindrical body, a flat bottom and a fixed roof (a self-supporting conical roof, the bearing capacity of which is provided by a conical shell of the deck, a skeleton conical roof consisting of carcass elements and flooring). The vertical tank is made with a floating roof or pontoon. The floating roof, located inside the reservoir on the surface of the liquid, is designed to reduce its loss from evaporation and to exclude the possibility of an explosion and fire.

The test vertical cylindrical tank has an anticorrosion coating. As a basis,

Fill line

Earth line

Fig. 1. Typical vertical storage tank (top filled)

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GASEOUS STREAMS TO:

In the process of exploitation of such tanks, their wear and tear occurs, which requires the elimination of the wall and bottom shell defects, mainly using fireworks. In this regard, the preparation of tanks, including degassing through the ventilation of the internal space, is an important integral stage of reservoir maintenance.

One of the most problematic places of this operation is extremely high level of explosion and fire risk, and therefore, a significant danger to the life and health of people in the zone of influence of reservoirs. Within forced ventilation of the VST-5000 tank, 1.5 tons of petroleum products vapor enters the atmospheric air. To address this shortcoming, the application of the absorption-condensation technology of vapor recovery of oil products, the efficiency of which reaches 99 %, is proposed in the paper.

The aim of research is determination of the level of anthropogenic load on the environment in the operation of vertical storage tanks for light oil products, as well as the rationale for environmental safety due to the introduction of forced ventilation with an ejector air supply method.

To achieve this goal, the following tasks were solved:

ronmental Protection Agency Standard 40 CFR Part 63 has established an emission limit of 10 g TOC/m3. The German TA-Luft Standard, the most stringent known gasoline emission regulation, has set an emissions limit to 150 mg TOC (excluding methane) per cubic meter of loaded product (0.15 g TOC/m3) [4-6].

Gaseous and liquid streams to environmental surroundings from storage in tanks are shown in Fig. 2.

Combustion of liquids occurs when flammable vapors released from the surface of the liquid ignite. The amount of flammable vapor given off from a liquid, and therefore the extent of the fire or explosion hazard, depends largely on the temperature of the liquid, its volatility, how much of the surface area is exposed, how long it is exposed for, and air movement over the surface. Other physical properties of the liquid, such as flashpoint, auto-ignition temperature (AIT), viscosity, lower explosion limit (LEL) and upper explosion limit (UEL), give further information as to how vapor/air mixtures may develop and also on the potential hazards.

VAPOUR RETURN SYSTEMS VAPOUR TREATMENT SYSTEMS

Storage Tanks

Operational: Tank Filling Emptying Cleaning Manual Gauging Sampling Breathing Fugitive emissions Incidents: Overfill Leakage

Transfer

Operational: System Filling Draining Cleaning Pigging Purging Sampling Connecting Opening Fugitive emissions Incidents: Leakage

STORAGE IN TANKS

TRANSFER

Regulations on controlling organic vapor pollutants in air have been issued world-wide. In the ambient air quality standards produced by the US Environmental Protection Agency, the maximum 3-hour concentration of hydrocarbon content is 0.24 ppm, not to be exceeded for more than a year. The recently passed European Community stage emissions limit is 35 grams& total organic compounds (TOC) per cubic meter gasoline loaded (35 g TOC/m3). Similarly, the United States Envi3rd PARTY

Storage Tanks

Operational:

Incidents:

Draining Cleaning Sampling

Overfill Leakage

Transfer

Operational: Cleaning Pigging Sampling Connecting Opening Pressure relief

Incidents: Overfill Leakage

LIQUID STREAMS TO: OPEN AND CLOSED COLLECTION SYSTEMS, WASTE WATER TREATMENT, SOIL AND SURFACE WATER

Fig. 2. Flow chart with potential emissions resulting from aboveground and underground storage facilities

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Regulation 7 of Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) requires employers to classify places at the workplace where an explosive atmosphere may occur into hazardous and non-hazardous areas. The aim is reducing to a minimum acceptable level the probability of a flammable atmosphere coinciding with an electrical or other ignition source [7].

For flammable vapors there are three classes of hazardous area or zone: zone 0, zone 1 and zone 2. A zone is an area around a process or activity where a flammable atmosphere may be present.

Zone 0 is a place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapor or mist is present continuously or for long periods or frequently.

Zone 1 is a place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapor or mist is likely to occur in normal operation occasionally.

Zone 2 is a place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapor or mist is not likely to occur in normal operation but, if it does occur, will persist for a short period only [8].

Example of hazardous area classification for a fixed-roof tank is shown in Fig. 3.

The efficiency of the different technologies is product dependent, e. g. the adsorption efficiency of activated carbon is much higher for butane than it is for methane. Increased overall emission reduction efficiency can be achieved by having two systems in series, e. g. a membrane first stage treatment unit followed by a thermal oxidizer as a second stage to further control the emissions from the first stage.

However, the incremental reduction in emissions may be small compared to operating only a single stage process. For example, gasoline single stage VRUs (Vapor Recovery Units) can achieve an average efficiency of 99 %. Adding a second stage would remove another 0.9 %. The

capital and operating costs of the second stage, therefore, result in a very poor cost per ton emission abated effectiveness [9].

To date, many manuals have been developed to carry out pre-repair works, including the implementation of degassing of tanks [10-12]. To prevent air pollution by vapors of ventilated petroleum products, in particular gasoline, it is suggested to carry out forced ventilation of tanks with an ejector-vortex method of supplying air to the internal space [13].

However, there are no calculations for assessing the zone of active pollution due to natural ventilation or forced ventilation with traditional air supply Based on the foregoing, there is a need to assess the reduction of the man-made impact on the environment when implementing the proposed solution.

The red threat zone represents the worst hazard level, and the orange and yellow threat zones represent areas of decreasing hazard.

The calculation was based on the set location conditions, the type of shelter, the physical and chemical properties of chemicals removed from the reservoir into the atmospheric air, meteorological and climatic parameters, and so on (Table 2).

Fig. 3. Vertical storage tank - typical hazardous area classification

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Input dates for releasing modelling

Site data

Location ANDREEVKA, UKRAINE

Building Air Exchanges Per Hour 0.85 (sheltered single storied)

Coordinates Latitude 49°33&19" N Longitude 36°37&49" E

Chemical data

Chemical Name ISOOCTANE

CAS Number 540-84-1

Molecular Weight 114.23 g/mol

PAC-1 230 ppm

PAC-2 830 ppm

PAC-3 5000 ppm

LEL 9500 ppm

UEL 60000 ppm

Ambient Boiling Point 98.3 °C

Vapor Pressure at Ambient Temperature 0.051 atm

Ambient Saturation Concentration 51.929 ppm or 5.19 %

Atmospheric data (manual input of data)

Wind 5 meters/second from 60° true at 2 meters

Ground Roughness open country

Cloud Cover 3 tenths

Air Temperature 20 °C, No Inversion Height

Relative Humidity 25 %

Source strength

Source Height 16.9 meters

Direct Source 200 grams/sec

Release Duration 60 minutes

Release Rate 12 kilograms/min

Total Amount Released 720 kilograms

where API is air pollution index; qmean.i is mean annual (or mean monthly) concentration of the i-th pollutant, mg/m3; MPCd.m.i is its daily mean maximum permissible concentration mg/m3; K is a dimensionless coefficient allowing the degree of air pollution by the i-th pollutant to be adjusted to the degree of air pollution by substances of third hazard class.

The values of K: are 0.85, 1.0, 1.4 and 1.7, respectively, for hazard classes 4, 3, 2 and 1 of a given pollutant. Petroleum substance group (isooctane, gasoline) refers

to third hazard class that&s why it is used coefficient Ki at the level of 1.

AEGLs are calculated for five relatively short exposure periods - 10 minutes, 30 minutes, 1 hour, 4 hours, and 8 hours - as differentiated from air standards based on longer or repeated exposures. AEGL «levels» are dictated by the severity of the toxic effects caused by the exposure, with Level 1 being the least and Level 3 being the most severe. All levels are expressed as parts per million or milligrams per cubic meter (ppm or mg/m3) of a substance above which it is predicted that the general population could experience, including susceptible individuals.

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exposure guidelines, only a single IDLH value is defined for applicable chemicals.

Spreading algorithm for downwind dispersion may be provided one of the possible method such as follows: Gaussian dispersion model or Heavy Gas dispersion model. Referring to the initial data on the estimated situation of the entry of a steam-air mixture of petroleum products into the atmospheric air (Table 1) simulation was carried out using Heavy Gas dispersion model. The heavy gas dispersion models can be divided into four groups: simple/empirical models, intermediate/integral and shallow layer models, advanced/Lagrangian particle and Lagrangian Gaussian puff models, sophisticated/CFD models [17].

Three zones were given based on the value of MPC for gasoline or isooctane that is equal 5 mg/m3 (5 mg/(cu-m)). These zones are colored in three different colors: red, orange and yellow in order of decreasing danger level. The text information on the program display indicates the dimensions of the designated danger areas:

- Red: 1.2 kilometers - (5 mg/(cu-m));

- Orange: 1.6 kilometers - (3 mg/(cu-m));

- Yellow: 2.9 kilometers - (1 mg/(cu-m)).

Fig. 4 shows the zone of active pollution of atmospheric air with petrol vapors. If there is a population in the red zone, there is a real danger of acute toxic effects.

An ALOHA threat zone estimate displayed on a Google Earth map (Fig. 5). The red, orange and yellow zones indicate areas where specific Level of Concern thresholds were exceeded.

Fig. 6 shows the rate of change in the concentration of gasoline vapor at a distance of 1 km from the location of the reservoir for storing this petroleum product during ventilation without cleaning the exhaust steam-air mixture.

Fig. 7 shows flammable threat zone for gasoline vapor that is the part of a flammable vapor cloud where the concentration is in the flammable range, between the Lower and Upper Explosive Limits (LEL and UEL).

Fig. 5. Threat zone on a Google Earth map for the study area

Fin. 4. Toxic area of gasoline vapor during natural ventilation of tanks

Concentration of petrol vapor at a distance of 1 kilometer in the southwest direction

These limits are percentages that represent the concentration of the fuel (that is, the chemical vapor) in the air. If the chemical vapor comes into contact with an ignition source (such as a spark), it will burn only if its fuel-air concentration is between the LEL and the UEL because that portion of the cloud is already pre-mixed to the right mixture of fuel and air for burning to occur. ALOHA uses 60 % of the LEL as the default LOC for the red threat zone, because some experiments have shown that flame pockets can occur in places where the average concentration is above that level. Another common threat level used by responders is 10 % of the LEL, which is ALOHA&s default LOC for the yellow threat zone.

As can be seen from the Fig. 6, for the given conditions there are no red and orange zones. And this means that the danger of ignition is minimal, as indicated by the yellow zone of 80 m. The yellow zone is characterized by 10 % of the LEL.

Another no less important indicator is the explosion zone. Overpressure, also called a blast wave, refers to the sudden onset of a pressure wave after an explosion.

This pressure wave is caused by the energy released in the initial explosion—the bigger the initial explosion, the more damaging the pressure wave.

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Fig. 7. Flammable threat zone fer gasoline vapor

Unlike toxic LOCs, no well-defined guidelines or standards exist to evaluate the overpressure hazard. So, ALOHA uses default overpressure values (in pounds per square inch, psi) that are based on a review of several widely accepted sources on overpressure and explosions:

- 8.0 psi (destruction of buildings);

- 3.5 psi (serious injury likely);

- 1.0 psi (shatters glass).

For the case under consideration, the size of zone with serious injury likely is 13 m in the direction of the prevailing wind (according to the wind rose) as it is shown in Fig. 8.

Calculation of API in accordance with (1) can be carried out as follows:

It is known that the safe state of the environment, in particular atmospheric air, is characterized by the value of this indicator at a level below 1. Under the given conditions, the API is 1.6, which indicates that there is a danger to the population in the zone of influence of gasoline vapor emissions (Fig. 4, 5). Results of modeling and calculation of such zones: toxic area, flammable threat zone and blast area of gasoline vapor during natural ventilation of tanks indicate the following inferences.

Fig. 8. Blast area of gasoline vapor cloud explosion

The calculation was carried out for a reservoir with a volume of 5000 m3 at an initial concentration of 300 mg/m3. The assessment of active pollution zones was carried out with the calculation that the release of petroleum vapor is 200 g/s for 60 minutes. Other baseline data are given in Table 1.

Using the software product ALOHA it was determined that zone of acute toxic effect is 1.2 kilometers (5 mg/(cu-m)); zone of toxic effect of medium strength is 1.6 kilometers (3 mg/(cum)); zone of low toxicity is 2.9 kilometers (1 mg/(cum)). The population that is within these zones is in the field of increased dangers.

To reduce the emission of hydrocarbon vapors into the atmosphere when decontaminating land tanks for storage of light oil products, it is necessary to shorten the time of its carrying out. The task is achieved due to the fact that during forced ventilation, the supply of atmospheric air is carried out from opposite sides of the tank through two rotary air ejectors.

Strengths. Using the ejector method of degassing tanks for storage of light oil products allows to reduce the time of degassing of tanks of various shapes and sizes. This is achieved by intensifying the mixing of the internal vapor-gas medium with atmospheric air. Strengths also include a high degree of capture, the technology does not have high or low temperatures and pressures, small capital and operating costs, no maintenance sites, reliable operation of the installation in summer and winter; easy installation and maintenance of the installation.

Weaknesses. It is possible to attribute to the weak sides of the installation that the relative gas velocity is higher than the recommended values for atmospheric devices, which reduces the absorption efficiency, additional pumps are required for periodically feeding and pumping the absorbent (oil product) from

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the underground reservoir to the storage tank. Forced ventilation of tanks with an ejector-vortex method of air supply requires additional energy.

Opportunities. The impulse of absorption-condensation technology of vapor recovery of petroleum products allows to eliminate harmful emissions to the atmosphere, since its efficiency reaches 99 %. In this regard, the payment for the environmental tax and for damage to the environment is canceled. Moreover, recovered pairs of petroleum products, in particular gasoline, are sold as a commercial product, which causes additional income. The application of the software product ALOHA allows to predict and evaluate the zone of active contamination quickly and effectively when carrying out the ventilation of tanks by various methods of supplying air.

Threats. The exploitation of vertical steel tanks, including their ventilation, may not always be under the control of the maintenance staff. Various emergencies can lead to the complete destruction of reservoirs. And as a result, fires and explosions occur, which create huge damage to the environment. In addition, people who find themselves in this zone are at very high risk of injury and death.

References

АНАЛИЗ ТЕХНОГЕННОЙ НАГРУЗКИ НА ОКРУЖАЮЩУЮ СРЕДУ ПРИ ПРИНУДИТЕЛЬНОЙ ВЕНТИЛЯЦИИ РЕЗЕРВУАРОВ

Исследовано влияние светлых нефтепродуктов (бензин, дизельное топливо, керосин) на состояние окружающей среды в зоне воздействия резервуаров хранения этих продуктов. Обосновано, что применение принудительной вентиляции с традиционной подачей воздуха является экологически опасной операцией. Доказано, что альтернативой этому решению является эжекторно-вихревой метод подачи воздуха при дегазации резервуаров с последующим улавливанием паров нефтепродуктов с помощью абсорбционно-конденсационной установки.

Khalmuradov Batyr, PhD, Associate Professor, Department of Civil and Industrial Safety, National Aviation University, Kyiv, Ukraine, e-mail: batyrk@ukr.net, ORCID: http://orcid.org/0000-0003-2225-6528

Garbuz Sergey, Lecturer, Department of Fire and Technogenic Security of Facilities and Technologies, National University of Civil Protection of Ukraine, Kharkiv, Ukraine, e-mail: sgarbuz65@gmail.com, ORCID: http://orcid.org/0000-0001-6345-6214

Ablieieva Iryna, PhD, Department of Applied Ecology, Sumy State University, Ukraine, e-mail: i.ableyeva@ecolog.sumdu.edu.ua, ORCID: http://orcid.org/0000-0002-2333-0024